Earth leakage detection device and method in IT system

Abstract

Technology regarding a leakage current detection device for an IT system is disclosed. A leakage current detection device used in an IT system includes an offset generator and an amplifier. The offset generator applies a DC offset voltage to the secondary neutral point of an insulation section. The amplifier is connected between the offset generator and ground. The first amplifier receives and amplifies the voltage of the low-voltage terminal, which is the other end of the offset generator. The second amplifier outputs a waveform that is inverted from the output of the first amplifier. The leakage current detection device may further include a peak detector and a differential comparator. The peak detector outputs a signal corresponding to the maximum value of the output waveform of the amplifier, and the differential comparator receives the outputs of the first amplifier and the second amplifier and compares whether there is a difference in the output values. If there is a difference in the output values, it can be determined that there is a resistive leakage current. Phase-balanced resistive leakage current can be detected with a simple structure, and the influence of capacitive leakage current can be excluded. In addition, the phase in which phase-balanced resistive leakage current occurs can be detected quickly and accurately.

Description

Technology Field

[0001] The present invention relates to a leakage current detection device and method for an IT system, and in particular, discloses a technology regarding a leakage current detection device and method for an IT system capable of rapidly and accurately measuring resistive leakage current using an offset generator and an amplifier. Background Technology

[0002] In modern society, countless electrical devices that utilize electrical energy are used, including lighting fixtures such as fluorescent lights, home appliances like TVs and refrigerators, and transportation means such as subways and electric vehicles. While electricity makes our lives convenient and efficient, it also presents dangerous aspects. Representative examples of electrical hazards are electrical fires and electric shock accidents. In particular, electric shock accidents caused by electrical leakage can be fatal to humans and animals depending on the amount of current, even with a very short current flow time of just a few milliseconds.

[0003] To prevent electrical accidents, grounding systems such as TN, TT, and IT are utilized. Among these, the IT grounding method has the advantage of low fault current in the event of a grounding system failure, such as a ground fault or leakage current, because it insulates the power system or grounds it with high impedance. In other words, the IT grounding method is an efficient system grounding method for preventing electric shock and fire accidents caused by ground faults or leakage currents. Since the leakage current is not large, power can be maintained without tripping the leakage circuit breaker in the event of a grounding system failure. However, it is necessary to generate an audiovisual alarm in the event of a primary leakage or ground fault.

[0004] In IT systems, there is a problem in that it is difficult to operate relays because leakage current is limited. To solve this, faulty lines can be identified by detecting changes in the ground potential of each phase in the IT system. IT systems possess a characteristic where the potential of each phase changes when a grounding system fault occurs. Technologies are being developed to utilize this characteristic to detect abnormalities in the grounding system or to identify faulty lines. In IT systems, when a ground fault occurs on a specific line, the ground potential of the faulted phase decreases, while the potential of the healthy phases that are not faulty rises. Therefore, the faulty line can be detected by sensing the difference in ground potential between the phases.

[0005] Alternatively, a method is being developed to connect an insulation monitoring device containing high impedance between the power system and the ground, and to measure the current from the closed circuit formed between the power system and the ground when a grounding system fault occurs in a specific section. In this method, the current flowing through the path via the insulation monitoring device can be detected by the voltage distribution ratio based on the internal resistance within the device. The insulation monitoring device can further facilitate the detection of circulating current in the closed circuit by injecting specific signals, such as square waves, between the power line and the ground.

[0006] However, methods that detect changes in voltage or the amount of current circulating in a closed circuit have a problem in that it is difficult to detect and respond to grounding system faults in a phase-balanced state. Phase-balanced leakage refers to a situation where each phase is electrically leakage through an impedance value nearly identical to that of the ground, such as when all power lines in the system are submerged. In a phase-balanced leakage situation, if a person comes into contact with a specific phase, they may suffer an electric shock accident due to the lowered (hundreds of ohms) system grounding resistance. Furthermore, when such an electric shock accident occurs, there is no difference between the outflow and inflow currents of the leakage circuit breaker; consequently, a fault is not detected in the ZCT inside the leakage circuit breaker, posing a risk of continuous electric shock without the breaker tripping.

[0007] In the event of a phase-balanced leakage, each phase of the power system achieves a balanced state, resulting in a stable condition with no voltage fluctuations. Furthermore, the fault current circulating in the closed circuit between the power system and the ground is a small amount that is difficult to measure due to phase balance. In other words, when a phase-balanced leakage occurs, the system becomes electrically very similar to a normal state where no grounding fault has occurred. For this reason, methods that detect voltage changes or measure the amount of fault current circulating in the closed circuit face difficulties in detecting phase-balanced leakage.

[0008] Meanwhile, capacitive leakage current due to capacitance exists in many electrical devices. Since this capacitive leakage current is unlikely to pose a risk factor compared to resistive leakage current unless it is excessive, it is necessary to eliminate it when detecting leakage current and detect only resistive leakage current.

[0009] In conventional insulation monitoring devices, in order to exclude capacitance and measure only the resistive leakage current, the system waited until the ground capacitance of each line was buffered by a fault detection pulse. That is, the resistive leakage current was detected through the current flowing between the system and the ground after the transient response had completely ended. However, depending on the resistance value of the system and the ground capacitance value of each line, a detection delay of several seconds to several minutes or more may occur.

[0010] In addition, conventional insulation monitoring devices had a problem where, when the ground capacitance of each line distributed in the system was asymmetric, the leakage current of the resistive component and the asymmetric capacitive component were added together and detected. Although the actual insulation resistance value is good, the current component of the asymmetric ground capacitance distributed in each line flows into the measured resistance, which can lead to a false detection that there is a problem with the insulation resistance.

[0011] Furthermore, to further limit the system's leakage current, the detection resistor inside the insulation monitoring device could not be adjusted arbitrarily. Since the detection relies on converting the amount of current flowing through the resistor, increasing the resistance value results in a lower current, requiring a more sensitive resolution.

[0012] Meanwhile, Registered Patent No. 10-2671336, announced on June 3, 2024, relates to an "insulation monitoring device capable of measuring capacitance," which is configured to quickly separate and measure capacitance and insulation resistance while forming a closed circuit with grounding when a ground fault current occurs, and to eliminate the risk of internal circuit damage of the insulation monitoring device even when a high voltage between phases is applied. An insulation monitoring device capable of measuring capacitance is disclosed, comprising: a constant voltage / constant current generating unit that generates a measuring current (Im) as a constant current; semiconductor switches (T1, T2) that are turned on by a start signal of an MCU so that the measuring current (Im) output from the constant voltage / constant current generating unit (100) conducts to each phase power line; a current detection unit that measures the insulation resistance (Rf) while detecting the magnitude of the measuring current flowing to the insulation resistance (Rf) between the system and ground after the capacitor between the system and ground is fully charged due to the measuring current flowing through the power line through which the semiconductor switch is conducted; and a voltage detection unit that measures the capacitance by detecting the charging voltage across the capacitor between the system and ground after the capacitor between the system and ground is fully charged due to the measuring current flowing through the power line through which the semiconductor switch is conducted, and using previously stored charging voltage and capacitance-related data. Prior art literature

[0013] (Patent Document 0001) KR 10-2671336 B1 (2024.06.03.) The problem to be solved

[0014] One objective of the present invention is to provide a leakage current detection device with a simple structure that quickly and accurately detects leakage current in an IT system.

[0015] Another objective of the present invention is to provide a leakage current detection device capable of filtering capacitive leakage current in an IT system and detecting only resistive leakage current.

[0016] Another objective of the present invention is to provide a leakage current detection device capable of accurately detecting phase-balanced resistive leakage current in an IT system.

[0017] Another objective of the present invention is to provide a leakage current detection device capable of rapidly and accurately detecting the phase where a resistive leakage current occurs in an IT system.

[0018] The problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below. means of solving the problem

[0019] According to one aspect of the proposed invention, a leakage current detection device (100, 200, 1300, 1400, 1500, 1600, 1700) used in an IT system includes an offset generating unit (150, 250, 1350) and an amplification unit (160, 260, 1360).

[0020] The leakage current detection device (100, 200, 1300, 1400, 1500, 1600, 1700) is connected to the neutral point (C) of the secondary power line (L1, L2; L1, L2, L3) to which the load is connected, which is separated from the primary power distribution line by the insulating part (110, 210, 1310, 1410, 1510, 1610, 1710). The insulating part (110, 210, 1310, 1410, 1510, 1610, 1710) separates the primary power distribution line from the power line (L1, L2; L1, L2, L3) of the secondary IT system.

[0021] One end of the offset generating unit (150, 250, 1350) is connected to the secondary neutral point (C) of the insulation unit (110, 210, 1310, 1410, 1510, 1610, 1710), and applies a DC offset voltage to the secondary neutral point (C). The offset generating unit (150, 250, 1350) can set the voltage of the secondary neutral point (C) higher than the voltage of the other end (D) facing ground.

[0022] The amplifier (160, 260, 1360) is connected between the offset generator (150, 250, 1350) and ground, and receives and amplifies the voltage of the other end (D) directed toward ground of the offset generator (150, 250, 1350). The amplifier (160, 260, 1360) can be set to have a gain less than or equal to 1 so that the output voltage becomes lower than the input voltage.

[0023] The above amplifier (160, 260, 1360) includes a first amplifier (161, 261, 1361) and a second amplifier (162, 262, 1362). The first amplifier (161, 261, 1361) receives and amplifies the voltage of the other end (D) of the offset generator (150, 250, 1350). The second amplifier (162, 262, 1362) outputs a waveform that is inverted from the output of the first amplifier (161, 261, 1361). For example, the first amplifier (161, 261, 1361) and the second amplifier (162, 262, 1362) can be configured as inverting amplifiers.

[0024] According to an additional aspect, the second amplifier (162, 262, 1362) may be configured to receive the output voltage of the first amplifier (161, 261, 1361) as an input and output an inverted waveform. For example, the amplifier (160, 260, 1360) may be configured to include a first amplifier (161, 261, 1361) configured as an inverting amplifier and a second amplifier (162, 262, 1362) configured as a cascaded inverting amplifier.

[0025] According to an additional aspect, the leakage current detection device (100, 200, 1300, 1400, 1500, 1600, 1700) further includes a peak detection unit (170, 270, 1370). The peak detection unit (170, 270, 1370) outputs a signal corresponding to the maximum value of the output waveform of the amplification unit (160, 260, 1360).

[0026] According to a variation of the embodiment, the peak detection unit (170, 270, 1370) includes a first peak detection unit (271) and a second peak detection unit (272), and outputs a signal corresponding to the maximum value of the output waveform of the first amplifier (161, 261, 1361) and a signal corresponding to the maximum value of the output waveform of the second amplifier (162, 262, 1362), respectively. That is, the first peak detection unit (271) can be configured to output a signal corresponding to the maximum value of the output waveform of the first amplifier (161, 261, 1361), and the second peak detection unit (272) can be configured to output a signal corresponding to the maximum value of the output waveform of the second amplifier (162, 262, 1362), respectively.

[0027] According to an additional aspect, the peak detection unit (170, 270, 1370) may be configured to include a rectifier circuit. The rectifier circuit of the peak detection unit (170, 270, 1370) may be configured to include a diode placed between the input and the output and a capacitor placed between the output and ground.

[0028] According to an additional aspect, the leakage current detection device (100, 200, 1300, 1400, 1500, 1600, 1700) further includes a differential comparator (180, 280, 1380). The differential comparator (180, 280, 1380) outputs a signal including a DC offset voltage based on the output of the first amplifier (161, 261, 1361) and the output of the second amplifier (162, 262, 1362).

[0029] For example, the differential comparator (180, 280, 1380) can directly receive the output of the amplifier (160, 260, 1360) and output a signal including a DC offset voltage from the output of the first amplifier (161, 261, 1361) and the output of the second amplifier (162, 262, 1362).

[0030] According to a variation of the embodiment, the differential comparator (180, 280, 1380) may receive the output of the peak detector (170, 270, 1370) and output a signal including a DC offset voltage. For example, a signal including a DC offset voltage may be output from the output of the first peak detector (271) corresponding to the output of the first amplifier (161, 261, 1361) and the output of the second peak detector (272) corresponding to the output of the second amplifier (162, 262, 1362).

[0031] For example, when the amplifier (160, 260, 1360), the peak detection unit (170, 270, 1370), and the differential comparison unit (180, 280, 1380) are connected in series, the signal output from the amplifier (160, 260, 1360) passes through the peak detection unit (170, 270, 1370) and is transmitted to the differential comparison unit (180, 280, 1380). In this case, the differential comparator (180, 280, 1380) can output a signal including a DC offset voltage using a signal transmitted through a peak detector (170, 270, 1370) based on the output of the first amplifier (161, 261, 1361) and the output of the second amplifier (162, 262, 1362).

[0032] According to an additional aspect, the differential comparator (180, 280, 1380) can be configured as a differential amplifier circuit including an operational amplifier.

[0033] According to a variation of the embodiment, the differential comparator (180, 280, 1380) may further include a comparator (not shown). For example, the output of the differential amplifier circuit may be input to a comparator to which a reference voltage is input, and a signal that simply determines a resistive leakage current based on the difference from the reference voltage may be output.

[0034] According to an additional aspect, the leakage detection device (100, 200, 1300, 1400, 1500, 1600, 1700) further includes a control unit (190, 290, 1390, 1490, 1590, 1690, 1790). The control unit (190, 290, 1390, 1490, 1590, 1690, 1790) determines that a resistive leakage has occurred if there is a difference between the output values ​​of the first amplifier (161, 261, 1361) and the second amplifier (162, 262, 1362) based on the output signal of the amplifier (160, 260, 1360).

[0035] According to a variation of the embodiment, the control unit (190, 290, 1390, 1490, 1590, 1690, 1790) can determine the occurrence of a resistive leakage current using the output of the peak detection unit (170, 270, 1370). Since the peak detection unit (170, 270, 1370) outputs a signal corresponding to the maximum value of the output waveform of the amplification unit (160, 260, 1360), the control unit (190, 290, 1390, 1490, 1590, 1690, 1790) can determine the occurrence of a resistive leakage current based on the output signal of the amplification unit (160, 260, 1360).

[0036] According to another variation of the embodiment, the control unit (190, 290, 1390, 1490, 1590, 1690, 1790) can determine the occurrence of a resistive leakage current using the output of the differential comparator (180, 280, 1380). Since the output of the differential comparator (180, 280, 1380) is also obtained based on the output of the amplifier (160, 260, 1360), the control unit (190, 290, 1390, 1490, 1590, 1690, 1790) can determine the occurrence of a resistive leakage current based on the output signal of the amplifier (160, 260, 1360).

[0037] According to another variation of the embodiment, the control unit (190, 290, 1390, 1490, 1590, 1690, 1790) can determine the occurrence of a resistive leakage current based on a signal generated when the output of the amplification unit (160, 260, 1360) passes through the peak detection unit (170, 270, 1370) and the differential comparison unit (180, 280, 1380).

[0038] According to an additional aspect, the leakage current detection device (100, 200, 1300, 1400, 1500, 1600, 1700) can be set to operate in an alarm mode or a cutoff mode.

[0039] According to an additional aspect, the control unit (190, 290, 1390, 1490, 1590, 1690, 1790) can be configured to output an alarm signal indicating the occurrence of a resistive leakage current when in alarm mode, and to transmit a signal to a circuit breaker (not shown) to cut off the secondary power line (L1, L2; L1, L2, L3) to which the load is connected by the insulation unit (110, 210, 1310, 1410, 1510, 1610, 1710) when in cutoff mode.

[0040] According to an additional aspect, the control unit (190, 290, 1390, 1490, 1590, 1690, 1790) determines that a non-phase balanced resistive leakage has occurred when the output of the amplifier unit (160, 260, 1360) is an AC signal including a DC offset, and determines that a phase balanced resistive leakage has occurred when the output of the amplifier unit (160, 260, 1360) is a DC signal including a DC offset.

[0041] According to an additional aspect, the control unit (190, 290, 1390, 1490, 1590, 1690, 1790) includes an AD converter unit (295) that generates a digital signal based on an analog signal output from an amplifier unit (160, 260, 1360). The control unit (190, 290, 1390, 1490, 1590, 1690, 1790) can determine whether the output waveform of the amplifier unit (160, 260, 1360) is direct current or alternating current through the AD converter unit (295).

[0042] According to an additional aspect, the leakage detection device (100, 200, 1300, 1400, 1500, 1600, 1700) further includes a circuit that transmits the output of an amplifier (160, 260, 1360) to an AD converter (295). For example, the output of the amplifier (160, 260, 1360) can be transmitted to the AD converter (295) through a differential amplifier circuit (285).

[0043] According to an additional aspect, the control unit (190, 290, 1390, 1490, 1590, 1690, 1790) determines whether the resistive leakage is a phase-balanced resistive leakage only when it is determined that a resistive leakage has occurred based on the output of the amplifier unit (160, 260, 1360).

[0044] According to a variation of the embodiment, the AD converter unit (295) can be configured to operate only when the signal (T) input to the control unit (190, 290, 1390, 1490, 1590, 1690, 1790) corresponds to a signal that causes a resistive leakage, thereby determining whether the resistive leakage is a phase-balanced storage leakage. When no resistive leakage occurs, the operation of the AD converter unit (295) can be stopped to use power efficiently.

[0045] According to an additional aspect, the leakage current detection device (100, 200, 1300, 1400, 1500, 1600, 1700) further includes a plurality of voltage adjustment units (1451, 1452; 1551, 1552; 1650) and a plurality of peak detection units for phase discrimination (1461, 1462; 1561, 1562; 1660).

[0046] Each voltage regulator (1451, 1452; 1551, 1552; 1650) has one end connected to the secondary power lines (L1, L2; L1, L2, L3) of the insulation section (110, 210, 1310, 1410, 1510, 1610, 1710) respectively, and the other end connected to ground, outputting a peak-to-peak voltage signal smaller than the peak-to-peak voltage of the power lines (L1, L2; L1, L2, L3).

[0047] Each peak detection unit (1461, 1462; 1561, 1562; 1660) for each phase is connected to each of the plurality of voltage adjustment units (1451, 1452; 1551, 1552; 1650) and outputs a signal corresponding to the maximum value of the signal waveform output from each of the voltage adjustment units (1451, 1452; 1551, 1552; 1650).

[0048] According to an additional aspect, the peak detection unit (1461, 1462; 1561, 1562; 1660) for phase discrimination may be configured to include a rectifier circuit. The rectifier circuit of the peak detection unit (1461, 1462; 1561, 1562; 1660) for phase discrimination may be configured to include a diode placed between the input and the output and a capacitor placed between the output and ground.

[0049] According to an additional aspect, the peak detection unit for phase discrimination (1461, 1462; 1561, 1562; 1660) includes an operational amplifier having a feedback loop between the output and the negative input, wherein the output of the voltage regulator (1451, 1452; 1551, 1552; 1650) is input as a positive input. For example, the peak detection unit for phase discrimination (1461, 1462; 1561, 1562; 1660) may be configured to include a non-inverting amplifier or a buffer. Unlike configurations having a negative input feedback loop such as an inverting amplifier, this configuration allows for detection while maintaining isolation because no input current flows through the feedback loop. Through this configuration, superior isolation performance can be obtained compared to a conventional inverting amplifier.

[0050] According to an additional aspect, the control unit (190, 290, 1390, 1490, 1590, 1690, 1790) can determine which power line the leakage occurred in based on the signal of the peak detection unit (1461, 1462; 1561, 1562; 1660) when a resistive leakage occurs.

[0051] According to an additional aspect, the leakage current detection device (100, 200, 1300, 1400, 1500, 1600, 1700) further includes a potential comparison unit (1470, 1570, 1670).

[0052] The potential comparison unit (1470, 1570, 1670) receives two outputs from the outputs of the plurality of phase discrimination peak detection units (1461, 1462; 1561, 1562; 1660) and outputs a binary signal. Using the binary signal allows the control unit to process the signal more efficiently. Additionally, the sensitivity of the difference value serving as the reference for phase discrimination can be adjusted by adjusting the resistance of the differential amplifier constituting the potential comparison unit (1470, 1570, 1670).

[0053] According to an additional aspect, the potential comparison unit (1470, 1570, 1670) may be configured to include a first differential amplifier (1571) and a second differential amplifier (1572) whose inputs are crossed with each other. A binary signal can be output using a pair of differential amplifiers whose inputs are crossed with each other.

[0054] The first differential amplifier (1571) is configured to receive a first output, which is one of the outputs of the plurality of phase-discriminating peak detectors (1461, 1462; 1561, 1562; 1660), as a positive input, and receive a second output, which is another output, as a negative input.

[0055] The second differential amplifier (1572) is configured to receive the first output as a negative input and the second output as a positive input so that the input signal of the first differential amplifier (1571) is input in a crossed manner.

[0056] According to an additional aspect, the leakage current detection device (100, 200, 1300, 1400, 1500, 1600, 1700) further includes a switch (SW1, SW2) disposed between the secondary power line (L1, L2; L1, L2, L3) of the insulation part (110, 210, 1310, 1410, 1510, 1610, 1710) and the voltage regulating part (1451, 1452; 1551, 1552; 1650).

[0057] According to an additional aspect, the control unit (190, 290, 1390, 1490, 1590, 1690, 1790) can, when a resistive leakage occurs, connect the switch (SW1, SW2) to operate the phase identification peak detection unit (1461, 1462; 1561, 1562; 1660) and determine which power line the leakage occurred in based on the signal of the phase identification peak detection unit (1461, 1462; 1561, 1562; 1660). When using the switch (SW1, SW2), efficient operation is possible by operating the phase identification peak detection unit (1461, 1462; 1561, 1562; 1660) only when a resistive leakage occurs.

[0058] According to an additional aspect, the leakage current detection device (100, 200, 1300, 1400, 1500, 1600, 1700) further includes a test resistor (Rt1, Rt2) and a voltage detector (1781, 1782). The test resistor (Rt1, Rt2) is connected by a switch (SWt1, SWt2) between the secondary power line (L1, L2; L1, L2, L3) of the insulation part (110, 210, 1310, 1410, 1510, 1610, 1710) and ground. The voltage detector (1781, 1782) is connected between the test resistor (Rt1, Rt2) and ground.

[0059] According to an additional aspect, the control unit (190, 290, 1390, 1490, 1590, 1690, 1790) changes to a cutoff mode that cuts off the secondary power lines (L1, L2; L1, L2, L3) of the insulation unit (110, 210, 1310, 1410, 1510, 1610, 1710) when a resistive leakage occurs, if the voltage received from the voltage detector (1781, 1782) is higher than the reference voltage.

[0060] According to an additional aspect, the leakage detection device (100, 200, 1300, 1400, 1500, 1600, 1700) further includes a cut-off mode indicator (1797). The cut-off mode indicator (1797) can notify the outside that the operation mode has been changed to a cut-off mode.

[0061] According to another aspect of the proposed invention, a leakage current detection method used in an IT system includes an offset voltage application step (S1910), a voltage input step (S1920), and an amplified waveform output step (S1930).

[0062] In the offset voltage application step (S1910), the offset generating unit (150, 250, 1350) applies a DC offset voltage to the secondary neutral point (C) of the insulating unit (110, 210, 1310, 1410, 1510, 1610, 1710) that separates the primary side power distribution line from the secondary side power line (L1, L2; L1, L2, L3).

[0063] In the voltage input step (S1920), the amplifier (160, 260, 1360) receives the voltage of the terminal (D) facing ground of the offset generator (150, 250, 1350) which applies a DC offset voltage to the secondary neutral point of the insulation.

[0064] In the amplified waveform output step (S1930), the amplifier (160, 260, 1360) amplifies the voltage of the terminal (D) facing ground of the input offset generator (150, 250, 1350) through the first amplifier (161, 261, 1361) and outputs it, and outputs a waveform that is inverted from the output of the first amplifier (161, 261, 1361) through the second amplifier (162, 262, 1362).

[0065] According to an additional aspect, in the amplified waveform output step (S1930), the amplifier (160, 260, 1360) transmits the output voltage of the first amplifier (161, 261, 1361) to the input of the second amplifier (162, 262, 1362). That is, the first amplifier (161, 261, 1361) transmits the output voltage to the input of the second amplifier (162, 262, 1362).

[0066] According to an additional aspect, the leakage current detection method further includes a peak detection step (S1940). In the peak detection step (S1940), the peak detection unit (170, 270, 1370) receives the output waveform of the first amplifier (161, 261, 1361) and the output waveform of the second amplifier (162, 262, 1362) and outputs a signal corresponding to each maximum value. The peak detection unit (170, 270, 1370) can rectify the input signal and output a signal corresponding to each maximum value.

[0067] According to an additional aspect, the leakage current detection method further includes a differential comparison step (S1950). In the differential comparison step (S1950), the differential comparison unit (180, 280, 1380) outputs a signal including a DC offset voltage based on the output of the first amplifier (161, 261, 1361) and the output of the second amplifier (162, 262, 1362).

[0068] According to a variation of the embodiment, the differential comparator (180, 280, 1380) receives a signal corresponding to the maximum value of the output waveform of the first amplifier (161, 261, 1361) output from the peak detection unit (170, 270, 1370) and a signal corresponding to the maximum value of the output waveform of the second amplifier (162, 262, 1362), and can output a signal including a DC offset voltage.

[0069] According to an additional aspect, the leakage current detection method further includes steps of determining a resistive leakage current (S1960) and outputting a resistive leakage current alarm (S1965) when there is a difference between two input values ​​in the differential comparison step (S1950).

[0070] According to an additional aspect, the leakage current detection method further includes steps of, when determined to be a resistive leakage current, checking whether it is in an alarm mode (S1970), outputting a resistive leakage current alarm signal if it is in an alarm mode (S1980), and outputting a signal to cut off the power line to a circuit breaker (not shown) if it is in a cutoff mode (S1990).

[0071] According to an additional aspect, the leakage current detection method further includes a voltage adjustment step (S2020) and a peak detection step for phase identification (S2030).

[0072] In the voltage adjustment step (S2020), the voltage adjustment unit (1451, 1452; 1551, 1552; 1650) outputs an adjusted voltage by lowering the voltage between peaks of the voltage signals of the secondary power lines (L1, L2; L1, L2, L3) of the insulation unit (110, 210, 1310, 1410, 1510, 1610, 1710).

[0073] In the phase discrimination peak detection step (S2030), the phase discrimination peak detection unit (1461, 1462; 1561, 1562; 1660) outputs a phase discrimination peak signal corresponding to the maximum value of the controlled voltage waveform.

[0074] According to an additional aspect, the leakage current detection method further includes a potential comparison step (S2040).

[0075] In the potential comparison step (S2040), the potential comparison unit (1470, 1670) receives two signals among a plurality of phase discrimination peak signals and outputs a binary signal.

[0076] According to an additional aspect, the potential comparison step (S2040) includes a first differential amplification step and a second differential amplification step.

[0077] In the first differential amplifier stage, the first differential amplifier (1571) receives the first signal among the two signals at a positive input and receives the second signal among the two signals at a negative input.

[0078] In the second differential amplifier stage, the second differential amplifier (1572) crosses the signal input to the first differential amplifier (1571), receives the second signal at the positive input, and receives the first signal at the negative input.

[0079] According to an additional aspect, the leakage detection method further includes a step (S2050) of identifying a power line where a leakage has occurred. The control unit (190, 290, 1390, 1490, 1590, 1690, 1790) can identify a power line where a leakage has occurred using a binary signal output from the potential comparison step (S2040).

[0080] According to an additional aspect, the leakage current detection method further comprises the steps of connecting a test resistor between a power line and ground, measuring a voltage from a voltage detector connected to the test resistor, setting an alarm mode when the measured voltage for all power lines is less than a reference value, and setting a cutoff mode when the measured voltage for any one power line is greater than a reference value. Effects of the invention

[0081] The leakage current detection device and method for an IT system according to the present invention can filter capacitive leakage current using a DC offset voltage and detect only resistive leakage current.

[0082] The leakage current detection device and method for an IT system according to the present invention can accurately detect phase-balanced resistive leakage current, thereby preventing damage to humans and animals caused by leakage current even in cases such as power line flooding.

[0083] Furthermore, according to the present invention, leakage current can be detected quickly and accurately in IT systems, and it has a simple structure, making it easy to manufacture.

[0084] In addition, according to the present invention, when a resistive leakage current occurs in an IT system, the phase where the leakage current occurred can be detected quickly and accurately. Brief explanation of the drawing

[0085] FIG. 1 is a schematic diagram showing the main configuration of a leakage current detection device for an IT system according to one embodiment. FIG. 2a is a circuit diagram specifically showing the main configuration of a leakage current detection device of an IT system according to one embodiment. FIGS. 2B, FIGS. 2C, FIGS. 2D, FIGS. 2E, and FIGS. 2F are circuit diagrams specifically showing the main configuration of an IT system leakage current detection device according to a variation of one embodiment. Figure 3 is a photograph showing the main configuration of an IT system leakage detection device according to one embodiment implemented as an actual circuit. Figure 4 is a simulation result screen showing the input and output of the amplification unit when the leakage current detection device of an IT system according to one embodiment is in a normal state. FIG. 5 is a circuit diagram showing the case where a resistive leakage current occurs in a leakage current detection device of an IT system according to one embodiment. Figure 6 is a simulation result screen showing the input and output of an amplifier when a resistive leakage occurs in a leakage detection device of an IT system according to one embodiment. FIG. 7 is a circuit diagram showing the case where phase-balanced resistive leakage occurs in a leakage detection device of an IT system according to one embodiment. FIG. 8 is a simulation result screen showing the input and output of an amplifier when a phase-balanced resistive leakage occurs in a leakage current detection device of an IT system according to one embodiment. FIG. 9 is a circuit diagram showing the case where a capacitive leakage current occurs in a leakage current detection device of an IT system according to one embodiment. FIG. 10 is a simulation result screen showing the input and output of an amplifier when a capacitive leakage current occurs in a leakage current detection device of an IT system according to one embodiment. FIG. 11 is a circuit diagram showing the case where a phase-balanced capacitive leakage current occurs in a leakage current detection device of an IT system according to one embodiment. FIG. 12 is a simulation result screen showing the input and output of an amplifier when a phase-balanced capacitive leakage current occurs in a leakage current detection device of an IT system according to one embodiment. FIG. 13a is a schematic diagram showing the case where a leakage current detection device of an IT system according to one embodiment is applied to a three-phase power supply. FIG. 13b is a schematic diagram showing the case where a leakage current detection device of an IT system according to a variation of one embodiment is applied to a three-phase power supply. FIG. 14 is a schematic diagram showing the main configuration of an IT system leakage detection device according to one embodiment, when the device includes a leakage phase determination unit. FIG. 15a is a circuit diagram specifically showing the main configuration of an IT system leakage detection device according to one embodiment, when the leakage phase determination unit is included. FIG. 15b is a circuit diagram specifically showing the main configuration of an IT system leakage detection device according to a variation of one embodiment, in which the leakage phase determination unit is included. FIG. 16 is a schematic diagram showing the main configuration of an IT system leakage detection device according to one embodiment, which includes a leakage phase determination unit, when applied to a three-phase power supply. FIG. 17 is a schematic diagram showing the configuration of a capacitive leakage current detection unit in a leakage current detection device of an IT system according to one embodiment. FIG. 18 is a flowchart illustrating a method for determining an operating mode using a capacitive leakage current detection unit in a leakage current detection device of an IT system according to one embodiment. FIG. 19 is a flowchart illustrating a method for detecting a leakage current state using a leakage current detector in a leakage current detection device of an IT system according to one embodiment. FIG. 20 is a flowchart illustrating a method for identifying a power line where a leakage current has occurred using a leakage current detector in a leakage current detection device of an IT system according to one embodiment. Specific details for implementing the invention

[0086] The foregoing and additional aspects are embodied through embodiments described with reference to the attached drawings. It is understood that the components of each embodiment may be combined in various ways within the embodiment or with components of other embodiments, unless otherwise stated or contradictory. Based on the principle that the inventor may appropriately define the concepts of terms to best describe his invention, the terms used in this specification and claims must be interpreted in a sense and concept consistent with the description or proposed technical idea. In this specification, a module or part may be a set of program instructions stored in memory to be executed on a computer or processor, or may be implemented using a set of electronic components or circuits such as an ASIC or FPGA to execute such instructions. Additionally, the operation of each module or part may be performed by one or more processors or devices. Components marked with the same or similar symbols perform the same or similar functions, so their description may be omitted. For components with reference numerals for which description is omitted, reference may be made to the descriptions previously made for components with the same or similar symbols.

[0087] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0088] FIG. 1 is a schematic diagram showing the main configuration of a leakage current detection device for an IT system according to one embodiment.

[0089] According to one aspect of the proposed invention, a leakage current detection device (100) used in an IT system includes a resistive leakage current detection unit (120). The leakage current detection device (100) may further include a control unit (190) that receives the output result of the resistive leakage current detection unit (120).

[0090] The leakage detection device (100) is connected to the neutral point (C) of the secondary power lines (L1, L2) of the insulation part (110). The insulation part (110) separates the primary power distribution line from the power lines (L1, L2) of the secondary IT system. In the IT system, the secondary power lines (L1, L2) are ungrounded or high-resistance grounded.

[0091] The insulation section (110) is configured to switch from the existing power distribution line to the IT system. Power supplied to the power lines (L1, L2) on the secondary side of the insulation section (110) is supplied to the load (140). According to the law of conservation of energy and Kirchhoff's law, the current on the secondary side of the insulation section (110) cannot flow to the existing power distribution line on the primary side of the insulation section (110). This is also the case when a fault occurs in the grounding system. The current flowing from the secondary side of the insulation section (110) to the ground cannot flow to the primary side of the insulation section (110), and this current forms a return path only to the secondary side of the insulation section (110).

[0092] The insulation section (110) can be composed of an isolation transformer or generator capable of insulating from the existing power distribution line. For example, the isolation transformer can be composed of a tap transformer.

[0093] The resistive leakage current detection unit (120) includes an offset generation unit (150) and an amplification unit (160). The resistive leakage current detection unit (120) may further include a peak detection unit (170) and a differential comparison unit (180).

[0094] One end of the offset generating unit (150) is connected to the secondary neutral point (C) or neutral line of the insulation unit (110), and applies a DC offset voltage to the secondary neutral point (C) and power lines (L1, L2). The other end (D) of the offset generating unit (150) is connected to ground through the amplifier unit (160). The offset generating unit (150) can be configured using a DC power supply, a battery, a current transformer, etc. For example, the offset generating unit (150) can be configured using a DC voltage from an analog rectifier circuit or a DC voltage from an SMPS, or by using a current transformer that can vary the voltage according to the output resistance value.

[0095] When a DC offset voltage is output from the offset generating unit (150), the voltage of the secondary neutral point (C) of the insulation unit (110) rises by the amount of the DC offset voltage compared to the other end (D) on the ground side. Likewise, the voltage of the secondary power lines (L1, L2) of the insulation unit (110) also rises by the amount of the DC offset voltage compared to before the output of the offset generating unit (150) is input.

[0096] According to an additional aspect, the offset generator (150) can set the voltage of the secondary neutral point (C) higher than the voltage of the other end (D) facing ground. That is, the DC offset voltage can be set to a positive (+) value. In this case, the positive terminal of the offset generator (150) is connected to the neutral point (C) of the secondary power line of the insulation unit (110), and the negative terminal is connected to the amplifier (160).

[0097] According to a variation of the embodiment, the offset generating unit (150) can set the voltage of the secondary neutral point (C) lower than the voltage of the other end (D) facing ground. That is, the DC offset voltage can be set to a negative (-) value. In this case, unlike the previous example, the polarity of the offset generating unit (150) can be reversed so that the positive electrode is connected to the amplification unit (160) and the negative electrode is connected to the neutral point (C) of the secondary power line of the insulation unit (110). In this case, the voltage of the secondary neutral point (C) of the insulation unit (110) drops by the amount of the DC offset voltage compared to the other end (D) facing ground. Similarly, the voltage of the secondary power lines (L1, L2) of the insulation unit (110) also drops by the amount of the DC offset voltage compared to before the output of the offset generating unit (150) is input. When an insulation resistance failure occurs, a change in the other end (D) is detected, and resistive leakage current detection is possible using the same principle.

[0098] The amplifier (160) is connected between the offset generator (150) and ground, and receives and amplifies the voltage of the other end (D) directed toward the ground of the offset generator (150). The amplifier (160) can increase the input signal and output it when the gain is greater than 1, output a signal of the same magnitude as the input signal when the gain is 1, and reduce the input signal and output it when the gain is less than 1. It is advantageous for the amplifier to have a large input resistance and a small output resistance. Therefore, it is desirable to construct the amplifier using an operational amplifier (OP amp).

[0099] The amplifier (160) includes a first amplifier (161) and a second amplifier (162). The first amplifier (161) receives the voltage from the low-voltage terminal (D), which is the other end of the offset generator (150), and outputs an amplified signal (S1). The second amplifier (162) outputs a waveform (S2) that is inverted from the output of the first amplifier (161). By using two waveforms that are inverted from each other, the offset voltage can be easily extracted from the input signal. For example, if a DC offset voltage is added to a voltage signal of a sine waveform, the DC offset voltage can be easily identified by calculating the first half-cycle voltage of the sine waveform (S1) output from the first amplifier (161) and calculating and comparing the second half-cycle voltage of the sine waveform (S2) output from the second amplifier (162).

[0100] According to an additional aspect, at least one of the first amplifier (161) and the second amplifier (162) can be configured as a Power Operational Amplifier (Power OP amp) with an output of 100mA or more. Typically, an operational amplifier (OP amp) can be classified as a Power Operational Amplifier (Power OP amp) when the output current is 100mA or more. When configured as a Power Operational Amplifier (Power OP amp), it is possible to supply current more smoothly to the peak detection unit (170) after the amplifier (160), and there is an advantage of being able to charge the charging inrush current of the smoothing capacitor used in the peak detection unit (170) more quickly. For example, when the output current of the Power Operational Amplifier (Power OP amp) is 100mA, a constant current charging time of about 11ms is sufficient to charge 5V to 220uF. In this way, shortening the charging time of the smoothing capacitor has the effect of shortening the detection time of resistive leakage current detection.

[0101] According to a variation of the embodiment, the second amplifier (162) can receive and amplify the voltage of the low-voltage terminal (D), which is the other end of the offset generator (150). In this case, if the first amplifier (161) is a buffer or a non-inverting amplifier, the second amplifier (161) is configured as an inverting amplifier. Meanwhile, if the first amplifier (161) is an inverting amplifier, the second amplifier (161) can be configured as a buffer or a non-inverting amplifier.

[0102] According to an additional aspect, the second amplifier (162) receives the output voltage (S1) of the first amplifier (161) as input and outputs an inverted waveform (S2). For example, the second amplifier (162) can be configured as an inverting amplifier connected in a cascading manner to the output of the first amplifier (161). In this case, since the output of the second amplifier (162) is always inverted from the output of the first amplifier (161), the first amplifier (161) can be configured as an inverting amplifier, as well as a buffer or non-inverting amplifier.

[0103] According to an additional aspect, the leakage detection device (100) further includes a differential comparator (180). The differential comparator (180) receives the output (S1) of the first amplifier (161) and the output (S2) of the second amplifier (162) and outputs a signal including a DC offset voltage. The differential comparator (180) is configured to include a differential amplifier circuit so as to be able to compare whether there is a difference between the outputs of the two amplifiers, namely the output (S1) of the first amplifier (161) and the output (S2) of the second amplifier (162). If there is a difference between the output values ​​of the two amplifiers, the differential comparator (180) outputs a signal (T) to the control unit (190), so that the control unit (190) can generate an alarm or output a cutoff signal.

[0104] According to an additional aspect, the leakage current detection device (100) further includes a peak detection unit (170). The peak detection unit (170) outputs a signal corresponding to the maximum value of the output waveform of the amplifier (160) to facilitate comparison of differences in the differential comparison unit (180). For example, the peak detection unit (170) may be configured to include a rectifier circuit. The rectifier circuit may be configured using a diode and a capacitor. For example, the rectifier circuit may be configured by placing a diode between the input and output of the peak detection unit (170) and placing a smoothing capacitor between the output and ground. When using appropriate diodes and smoothing capacitors, the rectifier circuit can convert the signals (S1, S2) output from the first amplifier (161) and the second amplifier (162) into output waveforms (P1, P2) corresponding to the maximum value that have low ripple and are close to the maximum value, and output them.

[0105] According to a variation of the embodiment, the peak detection unit (170) can be configured to output a signal corresponding to the maximum value of the output waveform of the first amplifier (161, 261, 1361) and a signal corresponding to the maximum value of the output waveform of the second amplifier (162, 262, 1362), respectively.

[0106] According to an additional aspect, the amplifier (160), the peak detection unit (170), and the differential comparator (180) can be connected in series. The differential comparator (180) receives a signal from the peak detection unit (170), and since the peak detection unit (170) outputs a signal corresponding to the maximum value of the output waveform of the amplifier (160), the differential comparator (180) can output a signal including a DC offset voltage based on the output of the amplifier (160).

[0107] According to an additional aspect, the leakage detection device (100) can be set to operate in an alarm mode or a cutoff mode.

[0108] According to an additional aspect, the leakage detection device (100) further includes a control unit (190). The control unit (190) receives an output signal (T) from a differential comparator (180) and determines that a resistive leakage has occurred if there is a difference in the output values ​​of two amplifiers (161, 162). The control unit (190) can be configured to output an alarm signal indicating the occurrence of a resistive leakage when an alarm mode is in place, and to transmit a trip signal to a circuit breaker (not shown) to cut off the power line when a resistive leakage occurs.

[0109] FIG. 2a is a circuit diagram specifically showing the main configuration of a leakage current detection device of an IT system according to one embodiment.

[0110] Referring to FIG. 2a, the leakage current detection device (200) includes an offset generating unit (250), an amplification unit (260), a peak detection unit (270), and a differential comparison unit (280). The illustrated leakage current detection device (200) is configured identically to the resistive leakage current detection unit (220). The leakage current detection device (200) may further include a control unit (not shown).

[0111] The insulating part (210) is composed of a transformer, and an offset generating part (250) that generates a DC voltage is connected to the secondary neutral point (C) of the insulating part (210).

[0112] A first amplifier (261) configured as an inverting amplifier and a second amplifier (262) configured as an inverting amplifier that takes the output of the first amplifier as an input are connected to the other end (D) of the low-voltage side of the offset generating unit (250). For example, the first amplifier (261) and the second amplifier (262) can be formed in a cascade structure. Both the first amplifier (261) and the second amplifier (262) can be configured using operational amplifiers (OP amps).

[0113] According to an additional aspect, the gain of the first amplifier (261) is set to be less than 1. If the gain of the first amplifier (261) is set to be less than 1, the voltage level processed at the downstream end is lowered, making it easier to process in the control unit. The gain of the second amplifier (262) can be set to be equal to 1. If the gain of the second amplifier (262) is set to 1, the output level of the first amplifier (261) and the output level of the second amplifier (262) become the same, making it easy to compare output values ​​with each other.

[0114] The first amplifier (261) and the second amplifier (262) receive a dual power supply to output a signal. The dual power supply can be supplied by a separately provided dual power supply device (not shown). The dual power supply device has a positive output terminal (+Vcc), a negative output terminal (-Vcc), and a neutral point (GND) for grounding. The dual power supply device can be used as a power supply for electronic circuits other than the amplifiers.

[0115] At least one of the first amplifier (261) and the second amplifier (262) is grounded to the earth by a positive power supply. When the ground is connected to the neutral point of the positive power supply, the positive and negative power supply terminals of each amplifier can be electrically connected to the corresponding ground. For example, the amplifier can be configured between the neutral point connected to the offset generator and the earth to be electrically grounded, and can form a path through which leakage current flows when a leakage current occurs. Meanwhile, by adjusting the resistance value of the amplifier, the amount of leakage current flowing to the earth when a leakage current occurs can be controlled.

[0116] The output (S1) of the first amplifier (261) and the output (S2) of the second amplifier (262) are input to the peak detection unit (270). The peak detection unit (270) is composed of a rectifier circuit including a diode and a capacitor, and outputs rectified signals (P1, P2) corresponding to the maximum value of the peak from the input signals (S1, S2), respectively.

[0117] The differential comparator (280) receives signals (P1, P2) corresponding to the maximum values ​​of the signals (S1, S2) output from the first amplifier (161) and the second amplifier (162) output from the peak detection unit (270). The differential comparator (280) can compare the difference between the two input signals (P1, P2) to determine whether there is a DC offset voltage in the input signal and output the result as an output signal (T). The output signal (T) of the differential comparator (280) is transmitted to a control unit (not shown), and the control unit (not shown) can control the power line cutoff by outputting a leakage alarm or a trip signal.

[0118] Referring to FIG. 2a, the differential comparator (280) is configured as a differential amplifier circuit including an operational amplifier. The differential comparator (280) receives the outputs (P1, P2) of the peak detection unit (270) and outputs a signal (T) containing a DC offset voltage. Since the peak detection unit (270) receives the outputs (S1, S2) of the amplifier and outputs a signal (P1, P2) corresponding to the maximum value, the differential comparator (280) can be configured to output a signal (T) containing a DC offset voltage based on the output of the amplifier (260).

[0119] According to a variation of the embodiment, the differential comparator (280) may be configured to further include a comparator (not shown). For example, the output of the differential amplifier circuit may be input to a comparator to which a reference voltage is input, and configured to output a signal that simply determines a resistive leakage current based on the difference from the reference voltage. The reference voltage may be determined using the output of the voltage divider circuit. By configuring it to select from a variable resistor or a plurality of resistors, the resistance value of the voltage divider circuit may be changed to select a specific value among various reference voltages.

[0120] According to an additional aspect, the leakage detection device (200) further includes a control unit (290). The control unit (290) determines that a resistive leakage has occurred based on the output signals (S1, S2) of the amplifier (260), if the difference between the output (S1) of the first amplifier (261) and the output (S2) of the second amplifier (262) is greater than a predetermined threshold value.

[0121] FIGS. 2B, FIGS. 2C, FIGS. 2D, FIGS. 2E, and FIGS. 2F are circuit diagrams specifically showing the main configuration of an IT system leakage current detection device according to a variation of one embodiment.

[0122] Referring to FIG. 2b, the resistive leakage current detection unit (110) includes an offset generation unit (250), an amplification unit (260), and a peak detection unit (270). The leakage current detection device (200) may further include a control unit (290).

[0123] Compared to FIG. 2a, the leakage current detection device (200) of FIG. 2b does not include a differential comparator (280). Instead, the outputs (P1, P2) of the peak detection unit (270) are directly transmitted to the control unit (290). The control unit (290) receives the signal from the peak detection unit (270) and can perform various signal processing, such as analyzing the waveform of the input signal using an AD converter.

[0124] According to a variation of the embodiment, the peak detection unit (270) includes a first peak detection unit (271) and a second peak detection unit (272). The first peak detection unit (271) can be configured to output a signal corresponding to the maximum value of the output waveform of the first amplifier (261), and the second peak detection unit (272) can be configured to output a signal corresponding to the maximum value of the output waveform of the second amplifier (262).

[0125] According to an additional aspect, the peak detection unit (270) may be configured to include a rectifier circuit. For example, the first peak detection unit (271) and the second peak detection unit (272) may each be configured with a rectifier circuit including a diode placed between the input and the output and a capacitor placed between the output and ground.

[0126] Since the output signals (P1, P2) of the peak detection unit (270) are DC-converted signals of the signals (S1, S2) output from the amplifier (260), it is easy for the control unit to process them. The control unit (290) can determine the occurrence of a resistive leakage current using the output of the peak detection unit (270). Since the peak detection unit (270) outputs a signal corresponding to the maximum value of the output waveform of the amplifier (260), the control unit (290) can determine the occurrence of a resistive leakage current based on the output signal of the amplifier (260).

[0127] Referring to FIG. 2c, the resistive leakage current detection unit (110) includes an offset generation unit (250) and an amplification unit (260). The leakage current detection device (200) may further include a control unit (290).

[0128] Compared to FIG. 2b, the leakage detection device (200) of FIG. 2c does not include a peak detection unit (270). Instead, the outputs (S1, S2) of the amplification unit (260) are directly transmitted to the control unit (290). The control unit (290) receives the signal from the peak detection unit (270) and can perform various signal processing, such as analyzing the waveform of the input signal using an AD converter.

[0129] If the resistive leakage current detection unit (110) does not include a peak detection unit (270), the signal input to the microcontroller (MCU) may be a sinusoidal signal containing negative directionality. In this case, since the microcontroller (MCU) cannot receive the negative signal for signal processing, a conventional DC level shifting circuit may be additionally configured. The entire waveform input to the microcontroller (MCU) can be shifted to a range that the microcontroller (MCU) can read. For example, when detecting the presence or absence of an offset by processing the waveform of the first amplifier (261) using AD conversion (ADC), the entire waveform can be shifted to a positive range, an average value for a specific period is calculated, and then the DC level shift value is subtracted to extract only the DC offset voltage. Various calculation methods, such as integration as well as average values, can be utilized to extract the DC offset.

[0130] Meanwhile, if only the S1 signal is used, it is difficult to determine whether the DC offset superposition is caused by the offset generator (250) or an unintended DC offset caused by circuit noise, drift, etc. Therefore, when the S2 signal of the second amplifier (262) is detected simultaneously with S1, there is an advantage in being able to determine that the signal superimposed on the first amplifier (261) and the second amplifier (262) is a DC offset caused by the offset generator (250).

[0131] Referring to FIG. 2d, a first amplifier (265) and a second amplifier (266) constituting an amplifier connected to the lower part (D) of the offset generating unit (255) are connected in parallel.

[0132] The first amplifier (265) is configured to include an inverting amplifier, and the second amplifier (266) is configured to include a non-inverting amplifier, so that outputs with opposite phases can be sent to the peak detection unit (270). In this case, the first amplifier (265), which is an inverting amplifier, can be grounded to the earth through a dual power supply. In addition to FIGS. 2a and 2b, ground leakage can be easily detected by outputting signals with opposite phases in various ways.

[0133] Referring to FIG. 2e, the resistive leakage current detection unit (110) includes an offset generation unit (250), an amplification unit (260), and a differential comparison unit (285). The leakage current detection device (200) may further include a control unit (290).

[0134] Compared to FIG. 2a, the leakage detection device (200) of FIG. 2e does not include a peak detection unit (270). Instead, the outputs (S1, S2) of the amplifier (260) are transmitted to the differential comparator (285), and the differential comparator (285) outputs a signal (T1) containing a DC offset voltage and transmits it to the control unit (290).

[0135] The control unit (290) receives a signal from the differential comparator (285) and can perform various signal processing, such as analyzing the waveform of the input signal using an AD converter.

[0136] According to another variation of the embodiment, the control unit (290) can determine the occurrence of a resistive leakage current using the output (T1) of the differential comparator (285). Since the output (T1) of the differential comparator (285) is also obtained based on the outputs (S1, S2) of the amplifier (260), the control unit (290) can determine the occurrence of a resistive leakage current based on the output signals (S1, S2) of the amplifier (260).

[0137] Referring to FIG. 2f, the resistive leakage current detection unit (110) includes an offset generation unit (250), an amplification unit (260), a peak detection unit (270), and a differential comparison unit (280) that receives the outputs (P1, P2) of the peak detection unit (270). The leakage current detection device (200) may further include a control unit (290) and a differential comparison unit (285) that receives the outputs (S1, S2) of the amplification unit (260).

[0138] Compared to FIG. 2a, the leakage detection device (200) of FIG. 2f further includes a differential comparator (285) that receives the outputs (S1, S2) of the control unit (290) and the amplifier unit (260).

[0139] As in FIG. 2a, the control unit (290) can determine whether a resistive leakage current has occurred by using the output (T) of the differential comparison unit (280) which receives the output (P1, P2) of the peak detection unit (270).

[0140] Meanwhile, the control unit (290) can receive the signal (T1) from the differential comparator (285), which receives the output (S1, S2) of the amplifier (260), and transmit it to the AD converter unit (295). The AD converter unit (295) of the control unit (290) can generate a digital signal based on the analog signal transmitted from the amplifier (260). The control unit (290) can determine whether the output waveform of the amplifier (260) is DC or AC through the AD converter unit (295).

[0141] According to an additional aspect, the control unit (290) may be configured to determine that a non-phase balanced resistive leakage has occurred when the output of the amplifier (260) is an AC signal including a DC offset, and to determine that a phase balanced resistive leakage has occurred when the output of the amplifier (260) is a DC signal including a DC offset.

[0142] According to an additional aspect, the leakage detection device (200) further includes a circuit that transmits the output of the amplifier (260) to the AD converter (295). For example, the output of the amplifier (260) can be transmitted to the AD converter (295) through a differential amplifier circuit (285).

[0143] According to an additional aspect, the control unit (290) determines whether the resistive leakage is a phase-balanced resistive leakage only when it is determined that a resistive leakage has occurred based on the output of the amplifier unit (260).

[0144] For example, the AD converter unit (295) can be configured to operate only when the signal (T) input to the control unit (290) corresponds to a signal indicating the occurrence of a resistive leakage current, thereby determining whether the resistive leakage current is a phase-balanced storage leakage current. When no resistive leakage current occurs, the operation of the AD converter unit (295) can be stopped to use power efficiently.

[0145] Figure 3 is a photograph showing the main configuration of an IT system leakage detection device according to one embodiment implemented as an actual circuit.

[0146] Referring to FIG. 3, the insulation section (310) of the leakage current detection device is configured as a transformer. An offset generating section (350) that generates a DC voltage is connected to the secondary neutral point of the insulation section (310). At the other end of the offset generating section (350) on the low-voltage side, an amplifier section (360) is configured, which is connected to a first amplifier section configured as an inverting amplifier and a second amplifier section configured as an inverting amplifier that takes the output of the first amplifier section as an input.

[0147] The output of the amplifier (360) is input to the peak detection unit and differential comparison unit (380). The peak detection unit and differential comparison unit (380) are composed of a rectifier circuit including a diode and a capacitor, and each output a rectified signal corresponding to the maximum value of the peak from the output signal of the amplifier (360), and can compare the difference between the two rectified signals to check whether an offset voltage is included in the input signal and output the result as an output signal (T). The output signal of the peak detection unit and differential comparison unit (380) is transmitted to a control unit composed of an MCU, etc., to control a leakage alarm or power line cutoff.

[0148] Figure 4 is a simulation result screen showing the input and output of the amplification unit when the leakage current detection device of an IT system according to one embodiment is in a normal state.

[0149] FIG. 4(a) is a graph showing the voltage signal of the other end (D) of the offset generating unit (250) of FIG. 2a, and FIG. 4(b) is a graph showing the two voltage signals (P1, P2) which are the outputs of the peak detection unit (270) of FIG. 2a.

[0150] In a normal state, the offset generating unit (250) does not form a circuit with the secondary power lines (L1, L2) of the insulation unit (210), so no current flows. Therefore, one end (C) of the offset generating unit (250) increases the DC offset voltage on the secondary side of the insulation unit (210), but the other end (D) of the offset generating unit (250) is connected to ground. As a result, the voltage at the other end (D) of the offset generating unit (250) shows 0V, which is the ground voltage, as shown in FIG. 4 (a).

[0151] Since the output of the first amplifier (261) also becomes 0V, the output of the second amplifier (262) also becomes 0V, and the output of the peak detection unit (270) becomes 0V, as shown in FIG. 4 (b).

[0152] FIG. 5 is a circuit diagram showing the case where a resistive leakage current occurs in a leakage current detection device of an IT system according to one embodiment.

[0153] Referring to FIG. 5, this illustrates a case where a resistive leakage current occurs in only one of the power lines (L1). When a resistive leakage current occurs, it can be seen that a leakage impedance or leakage resistance (R1) is connected between the power line (L1) and the ground (earth). A DC and AC circuit is formed through the offset generating unit (550) by the leakage resistance (R1). That is, the leakage current from the AC power line is transmitted to the ground through the leakage resistance (R1) and can flow back into the power system through the offset generating unit (550) connected to the ground.

[0154] Figure 6 is a simulation result screen showing the input and output of an amplifier when a resistive leakage occurs in a leakage detection device of an IT system according to one embodiment.

[0155] FIG. 6(a) is a graph showing the voltage signal of the other end (D) of the offset generating unit (550) of FIG. 5, and FIG. 6(b) is a graph showing the two voltage signals (P1, P2) which are the outputs of the peak detection unit (570) of FIG. 5.

[0156] When a resistive leakage occurs in only one of the power lines (L1), DC and AC signals are detected in the offset generator (550) by the current flowing to the offset generator (550) through the leakage resistor (R1). At this time, since the voltage at the other end (D) of the offset generator (550) is lowered by the DC offset voltage relative to the neutral point (C) of the insulation part (510), the voltage at the other end (D) of the offset generator (550) outputs an AC signal with a negative (-) offset, which is the ground voltage, as shown in FIG. 6 (a). That is, in FIG. 6 (a), the positive (+) peak value of the sine waveform is output smaller than the negative (-) peak value.

[0157] The signal in FIG. 6(a) can be processed through the first amplifier (561) and the second amplifier (562) to obtain the first amplified signal (S1) and the second amplified signal (S2) in which the first amplified signal is inverted. FIG. 6(b) shows the output signals (P1, P2) rectified using the peak detection unit (570). Since both the first amplifier (561) and the second amplifier (562) are configured as inverting amplifiers, the red signal (P1), which inverts the relatively large negative peak value in FIG. 6(a), is output larger than the blue signal (P2), which inverts the relatively small negative peak value.

[0158] FIG. 7 is a circuit diagram showing the case where phase-balanced resistive leakage occurs in a leakage detection device of an IT system according to one embodiment.

[0159] Referring to Fig. 7, this illustrates a case where resistive leakage occurs in both of the two power lines (L1 and L2), such as in flooding. In this case, it can be seen that a leakage impedance or leakage resistance (R1) is connected between one power line (L1) and the ground (earth), and a leakage impedance or leakage resistance (R2) is connected between the other power line (L2) and the ground (earth). When resistive leakage occurs due to the same cause, the leakage resistance (R1) and the leakage resistance (R2) can be seen as having the same value. This case is called a resistive 'phase-balanced leakage'.

[0160] FIG. 8 is a simulation result screen showing the input and output of an amplifier when a phase-balanced resistive leakage occurs in a leakage current detection device of an IT system according to one embodiment.

[0161] FIG. 8(a) is a graph showing the voltage signal of the other end (D) of the offset generating unit (750) of FIG. 7, and FIG. 8(b) is a graph showing the two voltage signals (P1, P2) which are the outputs of the peak detection unit (770) of FIG. 7.

[0162] In the case of a resistive phase-balanced leakage current as shown in FIG. 7, the current flowing from one power line (L1) to ground through the leakage resistor (R1) flows to another power line (L2) through another leakage resistor (R2) of the same size, so the AC signal does not flow through the offset generator (750), and thus a negative DC voltage is output at the other end of the offset generator (750). At this time, since the secondary side of the insulation unit (710) is in phase balance, the voltage of the neutral point (C) becomes 0V, and the other end (D) of the offset generator (750) shows a negative offset voltage as shown in FIG. 8 (a).

[0163] When the signal in Fig. 8 (a) is inverted and amplified through the first amplifier (761), a positive DC signal (S1) is output, and when this is rectified, a DC signal (P1) indicated in red in Fig. 8 (b) is output. When the positive DC signal (S1), which is the output of the first amplifier (761), is inverted and amplified through the second amplifier (762), a negative DC signal (S2) is output. When this is rectified, there is no positive signal, so 0V is output, and this signal is indicated in blue in Fig. 8 (b).

[0164] FIG. 9 is a circuit diagram showing the case where a capacitive leakage current occurs in a leakage current detection device of an IT system according to one embodiment.

[0165] Referring to FIG. 9, this illustrates a case where a capacitive leakage current occurs in one of the power lines (L1). When a capacitive leakage current occurs, it can be seen that a leakage impedance or leakage capacitance (C1) is connected between the power line (L1) and the ground (earth). An AC circuit passing through the offset generator (950) is formed by the leakage capacitance (C1). That is, the leakage current from the AC power line is transmitted to the ground through the leakage capacitance (C1), and can flow back to the power line (L1) through the offset generator (950) connected to the ground. However, since DC signals cannot pass through the leakage capacitance (C1), only AC signals can flow as leakage current.

[0166] FIG. 10 is a simulation result screen showing the input and output of an amplifier when a capacitive leakage current occurs in a leakage current detection device of an IT system according to one embodiment.

[0167] Figure 10 (a) is a graph showing the voltage signal of the other end (D) of the offset generating unit (950) of Figure 9, and Figure 10 (b) is a graph showing the two voltage signals (P1, P2) which are the outputs of the peak detection unit (970) of Figure 9.

[0168] When a capacitive leakage current occurs in only one of the power lines (L1), an AC signal is detected in the offset generating unit (550) by the current flowing to the offset generating unit (950) through the leakage current capacitance (C1). Since the DC signal cannot pass through the leakage current capacitance (C1), there is no DC offset, so the positive (+) peak value of the sine waveform in FIG. 10 (a) is output as being equal to the negative (-) peak value.

[0169] Since the positive (+) peak value and the negative (-) peak value of the signal in FIG. 10 (a) are the same, the output signals (P1, P2) rectified from the signal amplified through the first amplifier (961) and the second amplifier (962) have the same value. This result is illustrated in FIG. 10 (b).

[0170] This invention can detect only resistive leakage current even if the ground capacitance values ​​of each line are asymmetrically distributed to only one power line (L1).

[0171] FIG. 11 is a circuit diagram showing the case where a phase-balanced capacitive leakage current occurs in a leakage current detection device of an IT system according to one embodiment.

[0172] Referring to FIG. 11, this illustrates a case where capacitive leakage occurs in both of the two power lines (L1 and L2). In this case, it can be seen that a leakage impedance or leakage capacitance (C1) is connected between one power line (L1) and the ground (earth), and a leakage impedance or leakage capacitance (C2) is connected between the other power line (L2) and the ground (earth). When capacitive leakage occurs due to the same cause, the leakage capacitance (C1) and the leakage capacitance (C2) can be seen as having the same value. This case is called a capacitive 'phase-balanced leakage'.

[0173] FIG. 12 is a simulation result screen showing the input and output of an amplifier when a phase-balanced capacitive leakage current occurs in a leakage current detection device of an IT system according to one embodiment.

[0174] Figure 12 (a) is a graph showing the voltage signal of the other end (D) of the offset generating unit (1150) of Figure 11, and Figure 12 (b) is a graph showing the two voltage signals (P1, P2) which are the outputs of the peak detection unit (1170) of Figure 11.

[0175] In the case of a capacitive phase-balanced leakage current as shown in FIG. 11, the current flowing from one power line (L1) to ground through the leakage capacitance (C1) flows to another power line (L2) through another leakage capacitance (C2) of the same size. Since the AC signal does not flow through the offset generator (1150), a voltage of approximately 0V is output at the other end of the offset generator (1150), similar to the normal state. At this time, since DC current cannot flow through the leakage capacitances (C1, C2), the voltage at the other end (D) of the offset generator (1150), as in the normal state, shows 0V, which is the ground voltage, as shown in FIG. 12 (a).

[0176] Just like in the normal state, the output of the first amplifier (1161) and the output of the second amplifier (1162) also become 0V, and the output of the peak detection unit (1170) becomes 0V, as shown in Fig. 12 (b).

[0177] Summarizing the results of FIGS. 4 to 12, the output of the other end (D), which is the low-voltage part of the offset generator (250), shows 0V in the normal state, resistive leakage, resistive phase-balanced leakage, capacitive leakage, and capacitive phase-balanced leakage, respectively, AC signal + DC offset, DC offset, AC signal, and 0V. Therefore, if the output of the offset generator (250) or the output of the first amplifier (161) contains a DC offset, it can be determined that a resistive leakage has occurred. Since the effect on the human body is minimal in most cases of capacitive leakage, the control unit (190) can use the output of the offset generator (250) or the first amplifier (261) to perform a cutoff operation or an alarm operation only in the case of a resistive leakage, rather than a capacitive leakage.

[0178] In the conventional electrical and electronic field, RC-based filters such as low-pass filters and integrators are utilized to detect voltages of specific frequencies. However, the detection time required for these filters is affected by the time constant. Among these, the charging time constant is a very important factor in fault detection. It is crucial how quickly a fault is detected after it occurs. However, with these time constant-based filters, lowering the cutoff frequency improves the sensitivity of DC offset voltage detection, but it increases the charging time constant, thereby increasing the time required for detection. For example, when using a low-pass filter, if the cutoff frequency is set to 0.1 Hz to detect the DC offset, the charging time constant takes approximately 1.6 seconds.

[0179] In contrast, the amplifier (160, 260) of this invention can detect insulation resistance failures more quickly without considering the time delay of the charging time constant. That is, the conventional method is a detection method using a frequency-based filter, whereas this invention is a faster and simpler detection method through the comparison of symmetry of a single waveform.

[0180] Meanwhile, the two outputs (P1, P2) of the peak detection unit (270) represent (0V, 0V), (two different positive voltages), (one positive voltage and 0V), (same positive voltage), and (0V, 0V), respectively, in the normal state, resistive leakage, resistive phase-balanced leakage, capacitive leakage, and capacitive phase-balanced leakage. Therefore, it can be determined that a resistive leakage has occurred only when the two outputs (P1, P2) of the peak detection unit (270) are different. For example, the control unit can directly compare the two outputs (P1, P2) and determine that a resistive leakage has occurred if the voltages of the two outputs (P1, P2) are different. Additionally, by adding a differential comparator (280), a signal (T) indicating that a resistive leakage has occurred is output when the voltages of the two outputs (P1, P2) are different, so that a cutoff operation or alarm operation corresponding to the resistive leakage can be performed without a control unit (190) or with only a simple control unit (190).

[0181] The output sensitivity of the signal (T) can be adjusted by controlling the DC offset applied voltage and the output ratio of the differential amplifier circuit of the first amplifier (161, 261), the second amplifier (162, 262), or the differential comparator (180, 280). For example, the trigger sensitivity of the signal (T) can be set to various values, such as a line insulation resistance of 1 M ohm or less, 500 k ohm or less.

[0182] In addition, the presence or absence of resistive leakage can be detected simply and quickly by comparing the signal (T) with a specific reference value, or changes in insulation resistance can be easily detected by continuously processing the output waveform of the signal (T) with an ADC. It is also possible to detect the presence or absence of resistive leakage by receiving the signal (T), confirming the presence or absence of the signal, and then processing the output signal of the amplifier with an ADC (see FIG. 2f).

[0183] Of course, even with only the configuration of the resistive leakage current detection unit (120), capacitance can be excluded and only resistive insulation failure can be quickly detected, but it is also easy to implement a monitoring circuit that detects continuous signal changes by utilizing the examples disclosed above.

[0184] According to another aspect of the proposed invention, a leakage current detection device used in an IT system includes an offset generating unit (150, 250), an amplification unit (160, 260), and a control unit (190, 290). An insulation unit (110, 210) separates the primary side power distribution line from the power line of the secondary side IT system. One end of the offset generating unit (150, 250) is connected to the secondary side neutral point (C) of the insulation unit (110, 210) to apply a DC offset voltage to the secondary side neutral point (C). An amplification unit (160, 260) is connected between the offset generating unit (150, 250) and ground, and receives and amplifies the voltage from the other end (D) of the offset generating unit (150, 250) toward ground. The control unit (190, 290) determines whether a resistive leakage has occurred based on the signal output from the amplifier unit (160, 260).

[0185] The leakage current detection device may further include a peak detection unit (170, 270) and a differential comparison unit (180, 280). The amplification unit (160, 260) may further include a first amplification unit (161, 261) and a second amplification unit (162, 262). For the offset generation unit (150, 250), the amplification unit (160, 260), the peak detection unit (170, 270), the differential comparison unit (180, 280), the control unit (190, 290), etc., you may refer to the parts already described above.

[0186] According to an additional aspect, the control unit (190, 290) can determine that a resistive leakage has occurred if the output of the amplifier unit (160, 260) is an AC signal including a DC offset, and determine that a phase-balanced resistive leakage has occurred if the output of the amplifier unit is a DC signal including a DC offset.

[0187] The DC signal including the DC offset in this invention does not refer solely to an ideal DC signal whose magnitude and direction remain completely constant over time. Even during actual phase equilibrium, small-signal pulsations or sinusoidal waves may be superimposed based on the DC offset due to slight impedance differences between phases. Even if minute magnitude fluctuations caused by small signals below a certain level exist, the signal can be considered DC if its direction remains constant. However, cases where the direction of the signal reverses over time are not included in the concept of DC as defined in this invention. Furthermore, the scope of DC analysis in this invention may be flexibly determined based on thresholds set according to the characteristics of the circuit and the purpose of the analysis.

[0188] FIG. 13a is a schematic diagram showing the case where a leakage current detection device of an IT system according to one embodiment is applied to a three-phase power supply.

[0189] Referring to FIG. 13a, the insulation section (1310) is composed of a three-phase transformer. The secondary side of the insulation section (1310) has power lines (L1, L2, L3) connected to a load (1340). The offset generating section (1350) is connected to a neutral line (N) connected to the neutral point of the secondary side of the insulation section (1310).

[0190] The illustrated leakage current detection device (1300) is configured in the same way as the resistive leakage current detection unit (1320). The leakage current detection device (1300) may further include a control unit (not illustrated).

[0191] The leakage current detection device (1300) of the three-phase power supply can be configured by combining an offset generation unit (1350), an amplifier unit (1360), a peak detection unit (1370), and a differential comparison unit (1380). Each component of the leakage current detection device (1300) of the three-phase power supply can be configured in the same manner as the corresponding components of the single-phase power supply described above.

[0192] FIG. 13b is a schematic diagram showing the case where a leakage current detection device of an IT system according to a variation of one embodiment is applied to a three-phase power supply.

[0193] Referring to FIG. 13b, the secondary of the insulation section (1315) is configured as a delta connection. In this case, the neutral line (N) can be connected to the offset generating section (1350) using a three-phase load section (1317) configured as a Y connection. The offset generating section (1350) is connected to the amplifier section (1360), and the remaining components can be configured in the same way as described above.

[0194] FIG. 14 is a schematic diagram showing the main configuration of an IT system leakage detection device according to one embodiment, when the device includes a leakage phase determination unit.

[0195] According to an additional aspect, a leakage current detection device (1400) used in an IT system includes a resistive leakage current detection unit (1420), a leakage current phase determination unit (1430), and a control unit (1490). The resistive leakage current detection unit (1420) can be configured in the same way as the resistive leakage current detection unit (120, 220, 1320) of the leakage current detection device (100, 200, 1300) described above.

[0196] Referring to FIG. 14, a resistive leakage detection unit (1420) is positioned between the secondary neutral point (C) of the insulation unit (1410) and ground, and the resistive leakage detection unit (1420) transmits a signal (T) related to whether there is a resistive leakage to the control unit (1490).

[0197] The leakage phase determination unit (1430) of the leakage detection device (1400) includes a voltage adjustment unit (1450) and a phase determination peak detection unit (1460).

[0198] The voltage regulator (1450) includes a plurality of voltage regulators (1451, 1452), each having one end connected to the secondary power line (L1, L2) of the insulation unit (1410) and the other end connected to ground.

[0199] In the case of a single phase, two voltage regulators can be configured, and in the case of a three-phase system, three voltage regulators can be configured. For example, since FIG. 14 is a single-phase system, it can be configured to include two voltage regulators: a first voltage regulator (1451) connected to the first power line (L1) and a second voltage regulator (1452) connected to the second power line (L2).

[0200] Each voltage regulator (1451, 1452) can be configured to output a peak-to-peak voltage signal smaller than the peak-to-peak voltage of the secondary power lines (L1, L2). Each voltage regulator (1451, 1452) can be configured as a voltage divider circuit using resistors.

[0201] The phase-distinguishing peak detection unit (1460) is connected to each of the plurality of voltage control units (1451, 1452). Similar to the voltage control units, in the case of a single phase, two phase-distinguishing peak detection units may be configured, and in the case of a three-phase system, three phase-distinguishing peak detection units may be configured. For example, in the case of FIG. 14, the first peak detection unit (1461) may be connected to the first voltage control unit (1451), and the second peak detection unit (1462) may be connected to the second voltage control unit (1452).

[0202] Each peak detection unit (1461, 1462) for each phase can be configured to output a signal corresponding to the maximum value of the signal waveform output from each voltage adjustment unit (1451, 1452). For example, the first peak detection unit (1461) can be configured to output a signal (N1b) corresponding to the maximum value of the output signal (N1a) of the first voltage adjustment unit (1451), and the second peak detection unit (1462) can be configured to output a signal (N2b) corresponding to the maximum value of the output signal (N2a) of the second voltage adjustment unit (1452).

[0203] According to an additional aspect, the peak detection unit (1461, 1462) for the upper plate can be configured to include a rectifier circuit.

[0204] It includes a plurality of voltage regulators (1451, 1452), each having one end connected to the secondary power lines (L1, L2) of the insulation section (1410) and the other end connected to ground. The rectifier circuit of the peak detection section (1461, 1462) for phase discrimination can be configured to include a diode placed between the input and the output and a smoothing capacitor placed between the output and ground.

[0205] The leakage phase determination unit (1430) of the leakage detection device (1400) may further include a potential comparison unit (1470).

[0206] The potential comparison unit (1470) receives two outputs (N1b, N2b) from the outputs of the plurality of phase discrimination peak detection units (1461, 1462) and outputs a binary signal (Va, Vb). By using the binary signal, the control unit can process the signal more efficiently. In addition, the sensitivity of the difference value serving as the reference for phase discrimination can be adjusted by adjusting the resistance of the differential amplifier constituting the potential comparison unit (1470).

[0207] According to an additional aspect, the control unit (1490) can determine which power line the leakage occurred in based on the signal of the peak detection unit (1461, 1462) for phase identification when a resistive leakage occurs.

[0208] FIG. 15a is a circuit diagram specifically showing the main configuration of an IT system leakage detection device according to one embodiment, when the leakage phase determination unit is included.

[0209] According to an additional aspect, a leakage current detection device (1500) used in an IT system includes a resistive leakage current detection unit (1520), a leakage current phase determination unit, and a control unit (1490). The resistive leakage current detection unit (1520) can be configured in the same way as the resistive leakage current detection unit (120, 220, 1320) of the leakage current detection device (100, 200, 1300) described above.

[0210] Referring to FIG. 15, a resistive leakage detection unit (1520) is positioned between the secondary neutral point (C) of the insulation unit (1510) and ground, and the resistive leakage detection unit (1520) transmits a signal (T) related to whether there is a resistive leakage to the control unit (1590).

[0211] The leakage phase determination unit of the leakage detection device (1500) includes a voltage adjustment unit (1550) and a phase determination peak detection unit (1460).

[0212] The voltage regulator (1550) includes a plurality of voltage regulators (1551, 1552), each having one end connected to a secondary power line (L1, L2) of the insulation unit (1510) and the other end connected to ground. For example, the voltage regulator (1550) may be configured to include two voltage regulators: a first voltage regulator (1551) connected to a first power line (L1) and a second voltage regulator (1552) connected to a second power line (L2).

[0213] Each voltage regulator (1551, 1552) can be configured as a voltage divider circuit using a resistor to output a peak-to-peak voltage signal (N1a, N2a) that is smaller than the peak-to-peak voltage of the secondary power lines (L1, L2). In this case, it is preferable to use a high resistance resistor of tens of MΩ to hundreds of MΩ.

[0214] A peak detection unit for phase identification includes a plurality of peak detection units (1561, 1562) connected to each of a plurality of voltage control units (1551, 1552). For example, in the case of FIG. 15, the first peak detection unit (1561) may be connected to the first voltage control unit (1551), and the second peak detection unit (1562) may be connected to the second voltage control unit (1552).

[0215] Each peak detection unit (1561, 1562) for each phase plate can be configured to output a signal corresponding to the maximum value of the signal waveform output from each voltage adjustment unit (1551, 1552).

[0216] According to an additional aspect, the phase-discriminating peak detectors (1561, 1562) may be configured to include a rectifier circuit. For example, the first phase-discriminating peak detector (1561) may include a first rectifier circuit (1561b), and the second phase-discriminating peak detector (1562) may be configured to include a first rectifier circuit (1562b). The rectifier circuits (1561b, 1562b) of the phase-discriminating peak detectors (1561, 1562) may be configured to include a diode placed between the input and the output and a smoothing capacitor placed between the output and ground.

[0217] According to an additional aspect, each phase-discriminating peak detector (1561, 1562) includes each operational amplifier circuit (1561a, 1562a) having a feedback loop between the output and the negative input, and the output of the voltage regulator (1551, 1552) is input as a positive input. For example, the phase-discriminating peak detector (1561, 1562) may be configured to include a non-inverting amplifier or a buffer. Unlike configurations having a negative input feedback loop such as an inverting amplifier, this configuration allows for detection while maintaining isolation because no input current flows through the feedback loop. Through this configuration, superior isolation performance can be obtained compared to a conventional inverting amplifier. It is preferable for the operational amplifier circuit (1561a, 1562a) of the phase-discriminating peak detector (1561, 1562) to use a dual supply.

[0218] According to an additional aspect, the control unit (1590) can determine which power line (L1, L2) has a leakage current based on the signals (N1b, N2b) of the peak detection unit (1561, 1562) for phase identification when a resistive leakage current occurs. For example, when a resistive leakage current occurs, the resistive leakage detection unit (1520) transmits a signal (T) related to the occurrence of a resistive leakage current to the control unit (1590). The control unit (1590) checks the signal (T) received from the resistive leakage detection unit (1520) to determine whether a resistive leakage current has occurred. If it is determined that a resistive leakage current has occurred, the voltage of the secondary power line (L1, L2) of the insulation unit (1510) is input through the respective voltage adjustment unit (1551, 1552). The input voltage (N1a, N2a) generates output signals (N1b, N2b) through the respective phase-specific peak detection units (1561, 1562) and is transmitted to the control unit (1590). The control unit (1590) determines which power line (L1, L2) has a leakage current based on the signals (N1b, N2b) from the phase-specific peak detection units (1561, 1562).

[0219] According to an additional aspect, the leakage detection device (1500) further includes a switch (SW1, SW2) positioned between the secondary power line (L1, L2) of the insulation part (1510) and the voltage regulator (1551, 1552).

[0220] According to an additional aspect, the control unit (1590) can operate the phase-identifying peak detection unit (1561, 1562) by connecting the switch (SW1, SW2) when a resistive leakage occurs, and determine which power line the leakage occurred based on the signal from the phase-identifying peak detection unit (1561, 1562). When using the switch (SW1, SW2), the phase-identifying peak detection unit (1561, 1562) is operated only when a resistive leakage occurs, enabling efficient operation.

[0221] FIG. 15b is a circuit diagram specifically showing the main configuration of an IT system leakage detection device according to a variation of one embodiment, in which the leakage phase determination unit is included.

[0222] Referring to FIG. 15b, the leakage phase determination unit of the leakage detection device (1500) further includes a potential comparison unit (1570). That is, the output signals (N1b, N2b) of the phase determination peak detection units (1561, 1562) are converted into binary signals (Va, Vb) by the potential comparison unit (1570) and input to the control unit (1590).

[0223] The potential comparison unit (1570) receives two outputs from a plurality of phase discrimination peak detection units (1561, 1562) and outputs a binary signal. Using the binary signal allows the control unit to process the signal more efficiently. Additionally, the sensitivity of the difference value serving as the reference for phase discrimination can be adjusted by adjusting the resistance of the differential amplifier constituting the potential comparison unit (1470).

[0224] According to an additional aspect, the potential comparison unit (1570) may be configured to include a first differential amplifier (1571) and a second differential amplifier (1572) whose inputs are crossed. A binary signal can be output using a pair of differential amplifiers whose inputs are crossed. When the binary signal from the potential comparison unit (1570) is transmitted to the control unit (1590), the control unit (1590) can process the transmitted signal more simply. In order to supply only a positive (+) voltage to the control unit, it is preferable to use a single supply for the operational amplifier used in the potential comparison unit (1570).

[0225] In the case of a single phase, since there are two power lines (L1, L2), the potential comparison unit (1570) receiving two outputs can be configured as one. At this time, the outputs (Va, Vb) of the potential comparison unit (1570) are two.

[0226] In the case of three phases, since there are three power lines (L1, L2, L3), there are three combinations of two outputs each (L1-L2, L2-L3, L3-L1), so three potential comparators can be configured to receive two outputs each. Since each potential comparator has two outputs, the total outputs of the three potential comparators are six.

[0227] breakdown situation L1 voltage L2 voltage T Va Vb Bit representation Control unit judgment L1 ground fault 0.40V 223.9V 7.63V 10.59V 0.62V 1, 1, 0 L1 resistive leakage current L1 1kΩ leakage current 0.58V 222.9V 7.62V 10.58V 0.67V 1, 1, 0 L1 resistive leakage current L1 10kΩ leakage current 2.21V 222.1V 7.65V 10.58V 0.67V 1, 1, 0 L1 resistive leakage current L1 30kΩ leakage current 6.39V 217.5V 7.27V 10.58V 0.67V 1, 1, 0 L1 resistive leakage current L1 100kΩ leakage current 18.75V 204.0V 6.44V 10.58V 0.67V 1, 1, 0 L1 resistive leakage current L1 200kΩ leakage current 32.75V 191.9V 5.53V 10.51V 0.66V 1, 1, 0 L1 resistive leakage current L2 ground fault 225.0V 1.08V 7.66V 0.67V 10.58V 1, 0, 1 L2 resistive leakage L2 1kΩ leakage current 226.1V 0.50V 7.69V 0.67V 10.58V 1, 0, 1 L2 resistive leakage L2 10kΩ leakage current 223.6V 2.56V 7.58V 0.67V 10.59V 1, 0, 1 L2 resistive leakage L2 30kΩ leakage current 218.9V 7.39V 7.29V 0.67V 10.58V 1, 0, 1 L2 resistive leakage L2 100kΩ leakage current 204.5V 21.53V 6.41V 0.67V 10.60V 1, 0, 1 L2 resistive leakage L2 200kΩ leakage current 189.1V 37.23V 5.51V 0.67V 10.54V 1, 0, 1 L2 resistive leakage L1, L2 simultaneous 5kΩ leakage current 113.5V 113.6V 2.46V 0.64V 0.64V 1, 0, 0 Resistive phase equilibrium leakage current L1, L2 simultaneous 10kΩ leakage current 113.7V 113.9V 2.46V 0.64V 0.64V 1, 0, 0 Resistive phase equilibrium leakage current L1, L2 simultaneous 30kΩ leakage current 114.2V 114.2V 2.44V 0.64V 0.64V 1, 0, 0 Resistive phase equilibrium leakage current

[0228] Table 1 shows experimental data on resistive leakage current detection for actual circuits.

[0229] The leakage current detection device was constructed in accordance with the single-phase circuit diagram of FIG. 15b. The measurement items are the voltage of the power line (L1 voltage, L2 voltage), the output (T) of the resistive leakage current detection unit, and the output signals (Va, Vb) of the potential comparison unit (1570).

[0230] As shown in Fig. 7, the fault conditions were tested by connecting a resistor (0Ω, 1kΩ, 10kΩ, 30kΩ, 100kΩ, 200kΩ) to the L1 power line or a resistor (0Ω, 1kΩ, 10kΩ, 30kΩ, 100kΩ, 200kΩ) to the L2 power line.

[0231] The threshold value of the output (T) of the resistive leakage current detection unit was set to 1 when the threshold value was greater than or equal to 2.0V, and the output of the potential comparison unit was set to 5.0V to show a bit representation (0, 1).

[0232] When a resistive leakage occurred in the L1 power line, the output (T) of the resistive leakage detection unit became 1, and the outputs (Va, Vb) of the potential comparison unit were 1 and 0. That is, when a leakage occurred in the L1 power line, the bit representation was "1, 1, 0".

[0233] When a resistive leakage occurred in the L2 power line, the output (T) of the resistive leakage detection unit became 1, and the outputs (Va, Vb) of the potential comparison unit were 0 and 1. That is, when a leakage occurred in the L2 power line, the bit representation was "1, 0, 1".

[0234] When simultaneous leakage of L1 power line and L2 power line, i.e., resistive phase equilibrium occurs, the output (T) of the resistive leakage detection unit becomes 1, and the outputs (Va, Vb) of the potential comparison unit are 0, 0. That is, when simultaneous leakage of L1 power line and L2 power line occurs, the bit representation is "1, 0, 0".

[0235] Therefore, by using the output (T) of the resistive leakage current detection unit and the outputs (Va, Vb) of the potential comparison unit, the L1 resistive leakage current, the L2 resistive leakage current, and the resistive phase-balanced leakage current can be obtained simply and clearly.

[0236] breakdown situation L1 voltage L2 voltage T Va Vb Bit representation Control unit judgment L1 10nF 50.10V 198.4V 0.67V 10.58V 0.67V 0, 1, 0 Capacitance not detected L1 20nF 26.96V 219.7V 0.67V 10.59V 0.67V 0, 1, 0 Capacitance not detected L1 30nF 19.12V 223.7V 0.68V 10.59V 0.67V 0, 1, 0 Capacitance not detected L1 40nF 14.22V 225.6V 0.67V 10.59V 0.67V 0, 1, 0 Capacitance not detected L1 50nF 11.50V 227.0V 0.68V 10.59V 0.67V 0, 1, 0 Capacitance not detected L2 10nF 60.30V 180.4V 0.66V 0.67V 9.72V 0, 0, 1 Capacitance not detected L2 20nF 29.50V 210.1V 0.67V 0.67V 10.59V 0, 0, 1 Capacitance not detected L2 30nF 21.10V 214.2V 0.67V 0.67V 10.58V 0, 0, 1 Capacitance not detected L2 40nF 15.42V 215.0V 0.67V 0.67V 10.59V 0, 0, 1 Capacitance not detected L2 50nF 12.12V 218.8V 0.67V 0.67V 10.58V 0, 0, 1 Capacitance not detected L1, L2 simultaneously 10nF 102.8V 121.5V 0.06V 1.85V 0.65V 0, 0, 0 Capacitance not detected L1, L2 simultaneously 30nF 111.2V 114.1V 0.00V 0.65V 0.65V 0, 0, 0 Capacitance not detected L1, L2 simultaneously 50nF 113.0V 113.0V 0.00V 0.65V 0.65V 0, 0, 0 Capacitance not detected

[0237] Table 2 shows experimental data on resistive leakage current detection for actual circuits.

[0238] The leakage current detection device was constructed in accordance with the single-phase circuit diagram of FIG. 15b. The measurement items are the voltage of the power line (L1 voltage, L2 voltage), the output (T) of the resistive leakage current detection unit, and the output signals (Va, Vb) of the potential comparison unit (1570).

[0239] As shown in Fig. 11, the fault conditions were tested by connecting capacitors (10nF, 20nF, 30nF, 40nF, 50nF) to the L1 power line or capacitors (10nF, 20nF, 30nF, 40nF, 50nF) to the L2 power line.

[0240] The threshold value of the output (T) of the resistive leakage current detection unit was set to 1 when the threshold value was greater than or equal to 2.0V, and the output of the potential comparison unit was set to 5.0V to show a bit representation (0, 1).

[0241] Since it is not a resistive leakage, the output (T) of the resistive leakage detection unit corresponds to 0. Therefore, the control unit can determine that capacitance is not detected.

[0242] breakdown situation L1 voltage L2 voltage T Va Vb Bit representation Control unit judgment L1 Flooding Short Circuit 0.30V 225.0V 7.71V 10.59V 0.67V 1, 1, 0 L1 resistive leakage current L2 Flooding Short Circuit 225.1V 0.40V 7.69V 0.67V 10.58V 1, 0, 1 L2 resistive leakage L1 L2 simultaneous flooding and short circuit 112.7V 112.5V 2.47V 0.64V 0.63V 1, 0, 0 Resistive phase equilibrium leakage current

[0243] Table 3 shows experimental data on immersion for actual circuits.

[0244] The leakage current detection device was constructed in accordance with the single-phase circuit diagram of FIG. 15b. The measurement items are the voltage of the power line (L1 voltage, L2 voltage), the output (T) of the resistive leakage current detection unit, and the output signals (Va, Vb) of the potential comparison unit (1570).

[0245] The fault conditions were measured by actually submerging the power lines of the load section in water.

[0246] The threshold value of the output (T) of the resistive leakage current detection unit was set to 1 when the threshold value was greater than or equal to 2.0V, and the output of the potential comparison unit was set to 5.0V to show a bit representation (0, 1).

[0247] When a water leakage occurred in the L1 power line, the output (T) of the resistive leakage detection unit became 1, and the outputs (Va, Vb) of the potential comparison unit were 1 and 0. That is, when a water leakage occurred in the L1 power line, the bit representation was "1, 1, 0", which showed the same value as the L1 resistive leakage in Table 1.

[0248] When a water leakage occurred in the L2 power line, the output (T) of the resistive leakage detection unit was 1, and the outputs (Va, Vb) of the potential comparison unit were 0 and 1. That is, when a water leakage occurred in the L2 power line, the bit representation was "1, 0, 1", which showed the same value as the L2 resistive leakage in Table 1.

[0249] When a simultaneous flooding leakage occurred between the L1 power line and the L2 power line, the output (T) of the resistive leakage detection unit became 1, and the outputs (Va, Vb) of the potential comparison unit were 0, 0. That is, when a simultaneous flooding leakage occurred between the L1 power line and the L2 power line, the bit representation was "1, 0, 0", which showed the same value as the resistive phase-balanced leakage in Table 1.

[0250] Therefore, even in the case of a submerged leakage current, by using the output (T) of the resistive leakage detection unit and the outputs (Va, Vb) of the potential comparison unit, the L1 submerged leakage current, the L2 submerged leakage current, and the simultaneous submerged leakage current of L1 and L2 can be determined simply and clearly, just like with a resistive leakage current.

[0251] Detecting phase-balanced resistive leakage by detecting waveform characteristics (DC + DC offset or AC + DC offset) in the resistive detection unit, and the phase-balanced resistive leakage detection method from the resistive leakage signal + phase discriminator signal, can be implemented as a dual detection structure through mutual cooperation.

[0252] FIG. 16 is a schematic diagram showing the main configuration of an IT system leakage detection device according to one embodiment, which includes a leakage phase determination unit, when applied to a three-phase power supply.

[0253] Referring to FIG. 16, the insulation section (1610) is composed of a three-phase transformer. The secondary side of the insulation section (1610) has power lines (L1, L2, L3) connected to a load (1340). A resistive leakage current detector (1620) is connected to a neutral line (N) connected to the neutral point of the secondary side of the insulation section (1610).

[0254] The illustrated leakage current detection device (1600) can be configured to include a resistive leakage current detection unit (1620), a leakage current phase determination unit (1630), and a control unit (1690).

[0255] The resistive leakage detection unit (1620) of the three-phase power supply can be configured in the same way as the resistive leakage detection unit (1320) of FIG. 13.

[0256] The voltage regulator (1650) includes three voltage regulators, each connected between the power lines (L1, L2, L3) and ground. Each voltage regulator transmits three output signals (N1a, N2a, N3a) to the phase discrimination peak detector (1660). The phase discrimination peak detector (1660) also includes three phase discrimination peak detectors connected to each voltage regulator. Each phase discrimination peak detector outputs three output signals (N1b, N2b, N3b) to the potential comparison unit (1670).

[0257] In the case of three phases, since there are three power lines (L1, L2, L3), if the outputs are combined in pairs (L1-L2, L2-L3, L3-L1), there are three combinations, so the potential comparison unit (1670) includes three potential comparison units, each receiving two outputs. Since the output of each potential comparison unit is two, the total outputs of the three potential comparison units (Va, Vb, Vc, Vd, Ve, Vf) are six.

[0258] Each component of the leakage current detection device (1600) of the three-phase power supply can be configured in the same way by referring to the description of the corresponding components described above.

[0259] FIG. 17 is a schematic diagram showing the configuration of a capacitive leakage current detection unit in a leakage current detection device of an IT system according to one embodiment.

[0260] According to an additional aspect, the leakage current detection device may further include a capacitive leakage current detection unit (1780). The capacitive leakage current detection unit (1780) includes test resistors (Rt1, Rt2) and voltage detectors (1781, 1782). As previously described, the leakage current detection device includes a resistive leakage current detection unit (1720) connected to an insulation unit (1710) and a secondary neutral point (C) of the insulation unit. The output signal (T) of the resistive leakage current detection unit (1720) is input to a control unit (1790). The control unit (1790) can control both the resistive leakage current detection unit (1720) and the capacitive leakage current detection unit (1780).

[0261] Test resistors (Rt1, Rt2) are connected between power lines (L1, L2) and ground by switches (SWt1, SWt2). The switches (SWt1, SWt2) are controlled to be opened or closed by a control unit (1790). Voltage detectors (1781, 1782) are connected between test resistors (Rt1, Rt2) and ground.

[0262] The control unit (1790) can detect the voltage caused by the current passing through the test resistors (Rt1, Rt2) by controlling the switches (SWt1, SWt2) at regular time intervals or when receiving an external interrupt signal.

[0263] When all switches (SWt1, SWt2) are OFF, if the control unit (1790) turns ON the first switch (SWt1), the first test resistor (Rt1) is connected to the first power line (L1). At this time, the first voltage signal (V1) is output from the first voltage detector (1781) by the current flowing through the first test resistor.

[0264] When the first voltage signal (V1) is received from the first voltage detector (1781), the control unit (1790) turns off the first switch (SWt1) and turns on the second switch (SWt2) to connect the second test resistor (Rt2) to the second power line (L2) and receives the second voltage signal (V2) from the second voltage detector (1782).

[0265] According to an additional aspect, the control unit (1790) changes to a cutoff mode that cuts off the power line when a resistive leakage occurs if the voltage received from the voltage detectors (1781, 1782) is higher than the reference voltage. The control unit (1790) can determine that a capacitive leakage occurs if the voltage signals (V1, V2) received from the voltage detectors (1781, 1782) are greater than the reference value. When a capacitive leakage occurs, the control unit can be set to operate in a cutoff mode rather than an alarm mode when a resistive leakage signal is received.

[0266] According to an additional aspect, the leakage current detection device may further include a resistive leakage current alarm device (not shown). The resistive leakage current alarm device may be equipped with a speaker or a light-emitting diode (LED), and may output an auditory or visual alarm signal to the outside when a signal (T) indicating that a resistive leakage current has occurred is input from the differential comparison unit of the resistive leakage current detection unit (1720). The resistive leakage current detection unit (1720) is connected to a control unit (1790) and may operate by a control signal output when a signal (T) indicating that a resistive leakage current has occurred is input to the control unit.

[0267] According to an additional aspect, the leakage detection device (1700) may further include a cut-off mode indicator (1797). The cut-off mode indicator (1797) may be equipped with a speaker or a light-emitting diode (LED), etc., so that when the operation mode of the leakage detection device is changed to a cut-off mode, the leakage detection device may be notified externally that it is operating in a cut-off mode.

[0268] FIG. 18 is a flowchart illustrating a method for determining an operating mode using a capacitive leakage current detection unit in a leakage current detection device of an IT system according to one embodiment.

[0269] According to another aspect of the proposed invention, a leakage current detection method used in an IT system first includes the step of a control unit (1790) receiving a resistive leakage current signal (T) from a resistive leakage current detection unit (1720) (S1810) and checking whether there is a resistive leakage current (S1820). If a resistive leakage current is confirmed, a resistive leakage current alarm may be output (S1830).

[0270] If there is no resistive leakage, a test resistor (Rt1, Rt2) is connected between the power line (L1, L2) and ground to generate a leakage for the power line test (S1840). Then, a voltage signal is received from the voltage detector (1781, 1782) connected to the test resistor (Rt1, Rt2) and the voltage is measured (S1850). The measured voltage is compared with a reference value (S1860), and if the measured voltage for any one of the power lines is greater than the reference value, it means the capacitance is greater than the reference value, so the device is set to operate in cutoff mode (S1890). When operating in cutoff mode, the leakage detection device can be notified externally that it is operating in cutoff mode through the cutoff mode indicator (1797).

[0271] If there are other power lines that have not been tested (S1870), a test leakage current is generated for the untested power lines and the process is repeated (S1840). If the measured voltage for all power lines (L1, L2) is lower than the reference value, the system is set to alarm mode (S1880).

[0272] FIG. 19 is a flowchart illustrating a method for detecting a leakage current state using a leakage current detector in a leakage current detection device of an IT system according to one embodiment.

[0273] According to another aspect of the proposed invention, a leakage current detection method used in an IT system includes an offset voltage application step (S1910), an amplifier voltage input step (S1920), and an amplifier waveform output step (S1930).

[0274] In the offset voltage application step (S1910), a DC offset voltage is applied to the secondary neutral point (C) of the insulation part (110) that separates the primary side power distribution line from the power line of the secondary side IT system.

[0275] In the amplifier voltage input step (S1920), the voltage of the low-voltage offset terminal (D) facing the ground of the offset generator (150), which applies a DC offset voltage to the secondary neutral point of the insulation part (110), is input to the amplifier part (160).

[0276] In the amplification waveform output step (S1930), the voltage of the low-voltage offset terminal (D) is amplified and output through the first amplifier (161), and a waveform that is inverted from the output of the first amplifier (161) is output through the second amplifier (162). To obtain a suitable output, the gain of each amplifier is set to a suitable value in advance.

[0277] According to an additional aspect, the amplified waveform output step (S1930) includes the step of transmitting the output voltage of the first amplifier (161) to the input of the second amplifier (162).

[0278] According to an additional aspect, the leakage current detection method further includes a peak detection step (S1940). In the peak detection step (S1940), the output waveform of the first amplifier (161) and the output waveform of the second amplifier (162) are received as inputs, and a signal corresponding to each maximum value is output. The peak detection step (S1940) may include a step of rectifying the input waveforms.

[0279] According to an additional aspect, the leakage detection method further includes a differential comparison step (S1950). In the differential comparison step (S1950), a signal corresponding to the maximum value obtained by rectifying the output waveform of the first amplifier (161) and a signal corresponding to the maximum value obtained by rectifying the output waveform of the second amplifier (162) are received as inputs, and a comparison is made to see if there is a difference between the two input values.

[0280] According to an additional aspect, the leakage current detection method includes a step (S1960) of determining that there is a resistive leakage current if there is a difference between two input values ​​in a differential comparison step. If there is no resistive leakage current, the measurement can be repeated.

[0281] In the case of a resistive leakage, a resistive leakage alarm can be output through a resistive leakage alarm device (not shown) (S1965). It is checked whether the set operation mode is an alarm mode (S1970), and if it is an alarm mode, a resistive leakage alarm, i.e., an alarm signal, is output (S1980). In the differential comparison step, if there is a difference between the two input values ​​and it is a cutoff mode, the control unit outputs a signal to cut off the power line to the circuit breaker (S1990). When the circuit breaker (not shown) receives the power line cutoff signal, it cuts off the power line to prevent personal injury and fire hazards caused by the leakage.

[0282] According to one embodiment, the potential of the other end (D) of the offset generating unit (150) can be maintained at 0V when the insulation is normal, thereby minimizing the computational burden of the circuit. Even when configuring the ADC of the control unit (190), the ADC can be operated using the output signal (T) of the resistive leakage current detection unit (120) as a judgment criterion, thus minimizing power consumption. That is, this invention can be implemented as an efficient structure that consumes power only when necessary.

[0283] FIG. 20 is a flowchart illustrating a method for identifying a power line where a leakage current has occurred using a leakage current detector in a leakage current detection device of an IT system according to one embodiment.

[0284] According to an additional aspect, the leakage current detection method further includes a voltage adjustment step (S2020) and a peak detection step for phase identification (S2030).

[0285] First, the voltage signal of the secondary power line (L1, L2) of the insulation part (1410) is received (S2010).

[0286] In the voltage adjustment step (S2020), the voltage adjustment unit (1451, 1452) outputs a adjusted voltage by lowering the voltage between peaks of the voltage signal of the secondary power line (L1, L2) of the insulation unit (1410).

[0287] In the phase discrimination peak detection step (S2030), the phase discrimination peak detection unit (1461, 1462) outputs a phase discrimination peak signal corresponding to the maximum value of the adjusted voltage waveform.

[0288] According to an additional aspect, the leakage current detection method further includes a potential comparison step (S2040).

[0289] In the potential comparison step (S2040), the potential comparison unit (1470) receives two signals among a plurality of phase discrimination peak signals and outputs a binary signal.

[0290] According to an additional aspect, the potential comparison step (S2040) includes a first differential amplification step and a second differential amplification step.

[0291] In the first differential amplifier stage, the first differential amplifier (1571) receives the first signal among the two signals at a positive input and receives the second signal among the two signals at a negative input.

[0292] In the second differential amplifier stage, the second differential amplifier (1572) crosses the signal input to the first differential amplifier (1571), receives the second signal at the positive input, and receives the first signal at the negative input.

[0293] According to an additional aspect, the leakage detection method further includes a step (S2050) of identifying a power line where a leakage has occurred. The control unit (190, 290, 1390, 1490, 1590, 1690, 1790) can identify a power line where a leakage has occurred using a binary signal output from the potential comparison step (S2040).

[0294] According to an additional aspect, the leakage current detection method further comprises the steps of connecting a test resistor between a power line and ground, measuring a voltage from a voltage detector connected to the test resistor, setting an alarm mode when the measured voltage for all power lines is less than a reference value, and setting a cutoff mode when the measured voltage for any one power line is greater than a reference value.

[0295] Although the present invention has been described above with reference to embodiments with reference to the accompanying drawings, it is not limited thereto and should be interpreted to encompass various variations that can be obviously derived from them by those skilled in the art. The claims are intended to encompass such variations. Explanation of the symbols

[0296] 100, 200, 1300, 1400, 1500, 1600, 1700: Leakage detection device 110, 210, 1310, 1410, 1510, 1610, 1710 : Insulation part 120, 220, 1320, 1420, 1520, 1620, 1720: Resistive leakage current detector 150, 250, 1350 : Offset generation section 160, 260, 1360: Amplifier 170, 270, 1370: Peak detector 180, 280, 1380 : Differential comparison unit 190, 290, 1390, 1490, 1590, 1690, 1790 : Control unit 1451, 1452; 1551, 1552; 1650 : Voltage regulator 1461, 1462; 1561, 1562; 1660 : Peak detector for phase differentiation 1470, 1570, 1670 : Potential comparator

Claims

Claim 1 A leakage current detection device used in an IT system in which a secondary power line to which a load is connected by an insulating member is separated from a primary power distribution line, comprising: an offset generator, one end of which is connected to the neutral point of the secondary power line of the insulating member and applies a DC offset voltage to the neutral point of the secondary power line; an amplifier, connected between the offset generator and ground, and receiving and amplifying the voltage of the other end of the offset generator directed toward ground; a plurality of voltage regulators, each having one end connected to the secondary power line of the insulating member and the other end connected to ground, and outputting a peak-to-peak voltage signal smaller than the peak-to-peak voltage of the power line; a plurality of phase-discriminating peak detectors, each connected to the plurality of voltage regulators and outputting a signal corresponding to the maximum value of the signal waveform output from the voltage regulators; and a control unit that determines whether a resistive leakage current has occurred on the secondary side of the insulating member based on the output signal of the amplifier; wherein the amplifier comprises: a first amplifier that receives and amplifies the voltage of the other end of the offset generator; A leakage detection device comprising: a first amplifier and a second amplifier that outputs a waveform inverted from the output of the first amplifier; wherein the control unit determines that a resistive leakage has occurred when there is a difference between the output of the first amplifier and the output of the second amplifier, and wherein the control unit determines that a resistive leakage has occurred based on the output signals of the plurality of phase-distinguishing peak detectors when it is determined that a resistive leakage has occurred. Claim 2 A leakage current detection device according to claim 1, wherein the second amplifier receives the output of the first amplifier as an input and outputs an inverted waveform. Claim 3 A leakage current detection device according to claim 1, further comprising a peak detection unit that outputs a signal corresponding to the maximum value of the output waveform of the amplifier. Claim 4 A leakage current detection device according to claim 1, further comprising a differential comparator that outputs a signal including a DC offset voltage based on the output of the first amplifier and the output of the second amplifier. Claim 5 delete Claim 6 A leakage detection device according to claim 1, wherein the control unit determines that a non-phase balanced resistive leakage has occurred when the output of the amplifier is an AC signal including a DC offset, and determines that a phase balanced resistive leakage has occurred when the output of the amplifier is a DC signal including a DC offset. Claim 7 A leakage detection device according to claim 6, wherein the control unit determines whether the resistive leakage is a phase-balanced resistive leakage only when it is determined that a resistive leakage has occurred based on the output of the amplification unit. Claim 8 delete Claim 9 A leakage current detection device according to claim 1, wherein the peak detection unit for phase discrimination comprises an operational amplifier having a feedback loop between the output and the negative input, wherein the output of the voltage adjustment unit is input as a positive input. Claim 10 A leakage current detection device according to claim 9, further comprising: a potential comparison unit that receives two outputs among the outputs of the plurality of phase discrimination peak detection units and outputs a binary signal; wherein the potential comparison unit comprises: a first differential amplifier that receives a first output, which is one output of the plurality of phase discrimination peak detection units, as a positive input and receives a second output, which is another output, as a negative input; and a second differential amplifier that receives the first output as a negative input and receives the second output as a positive input so that the input signals of the first differential amplifier are input in a cross-sectional manner. Claim 11 A leakage detection device according to any one of claims 1, 9, or 10, further comprising a switch disposed between the secondary power line of the insulating part and the voltage regulating part; wherein the control part connects the switch when a resistive leakage occurs and determines which power line the leakage occurred based on the signal of the peak detection part for phase identification. Claim 12 A leakage current detection device according to claim 1, further comprising: a test resistor connected by a switch between the secondary power line of the insulation part and ground; and a voltage detector connected between the test resistor and ground. Claim 13 A leakage detection device according to claim 12, wherein the control unit changes to a cutoff mode that cuts off the secondary power line of the insulation unit when a resistive leakage occurs, when the voltage received from the voltage detector is higher than the reference voltage. Claim 14 A leakage current detection method used in an IT system comprises: an offset voltage application step of applying a DC offset voltage to the secondary neutral point of an insulation section that separates a primary power distribution line from a secondary power line; a voltage input step of inputting the voltage of a terminal facing ground of an offset generating section into an amplifier; an amplified waveform output step of amplifying the voltage input into the amplifier through a first amplifier and outputting it, and outputting a waveform that is inverted from the output of the first amplifier through a second amplifier; a peak detection step of receiving the output waveform of the first amplifier and the output waveform of the second amplifier and outputting a signal corresponding to their respective maximum values; a differential comparison step of receiving a signal corresponding to the maximum value of the output waveform of the first amplifier and a signal corresponding to the maximum value of the output waveform of the second amplifier and comparing whether there is a difference between the two input values; a voltage adjustment step of lowering the voltage between peaks of the voltage signal of the power line and outputting an adjusted voltage if there is a difference between the two input values ​​in the differential comparison step; and a phase discrimination peak detection step of outputting a phase discrimination peak signal corresponding to the maximum value of the adjusted voltage waveform. A leakage current detection method characterized by including: a potential comparison step that receives two signals among a plurality of phase-distinguishing peak signals and outputs a binary signal. Claim 15 A leakage current detection method according to claim 14, wherein the potential comparison step comprises: a first differential amplifier step of inputting a first signal among two signals to a positive input of a first differential amplifier and inputting a second signal among two signals to a negative input; and a second differential amplifier step of crossing the signal input to the first differential amplifier to input the second signal to a positive input of a second differential amplifier and inputting the first signal to a negative input.

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