Apartment building intelligent power panel for reducing unbalanced load current

Abstract

The present application provides an apartment building intelligent distribution panel for reducing unbalanced load current. It includes: a main circuit breaker receiving a three-phase power supply and cutting off the three-phase power supply according to a control signal when overcurrent or leakage current is detected; a bus bar for distributing the three-phase power supply input through the main circuit breaker; a phase current transformer for detecting the phase current flowing through the three-phase line; a zero sequence current transformer for detecting the leakage current; an instrument transformer for detecting the voltage of the three-phase line; a plurality of single-phase distribution units cutting off one phase of the three-phase power supply of the bus bar according to a phase cutting control signal and supplying it to the corresponding single-phase load, while detecting and outputting the single-phase load current; a phase cutting switch capable of cutting off a certain phase of the three-phase supplied to each single-phase load (20-1 to 20-n), so as to eliminate the imbalance through phase cutting when the unbalanced load current exceeds the allowable value while monitoring the load current.

Description

Technical Field

[0001] This invention relates to the field of distribution panel technology for apartment buildings, and particularly to an intelligent distribution panel for apartment buildings that detects resistive leakage current and reduces unbalanced load current by measuring phase difference. Background Technology

[0002] Generally, apartment buildings, such as large-scale apartment complexes, receive ultra-high voltage electricity from Korea Electric Power Corporation (KEPCO) and supply power to each resident through a distribution panel. For this purpose, an incoming distribution panel is installed in the apartment building's power distribution room (substation). This panel receives the ultra-high voltage (22.9kV) electricity from KEPCO and converts it to low voltage (380V / 220V) through a transformer before supplying it to the residents. The electrical equipment is also built into the switch cabinet within the incoming distribution panel.

[0003] The incoming and distribution panel distributes power to various distribution panels, which in turn receive power from the incoming and distribution panel via main lines and supply it to the end loads and electrical equipment of each household. At this point, the incoming and distribution panel receives 22.9kV ultra-high voltage electricity from the Korea Electric Power Corporation (KEPCO), which is then stepped up to a three-phase four-wire system in a transformer to provide 380V or 220V power to the loads.

[0004] Typically, a switchboard contains various circuit breakers installed in the distribution room, which may include a busbar that receives power from the main circuit breaker. Power from the main circuit breaker's output power line, i.e., the busbar, is then supplied to various loads via branch circuit breakers.

[0005] In Korean Patent Office Registered Patent Publication (B1), Publication No. 10-1790138, "Intelligent Distribution Panel for Providing Branch Power Usage by Utilizing Hall Sensor for Current Measurement (hereinafter referred to as 'Patent Document 1')," in order to calculate the power supplied from the distribution panel to each load, it includes one or more sensor units for measuring current values, and an integrated multi-power meter for displaying the branch power usage output from each sensor unit, while simultaneously measuring the total power usage used through the distribution panel, and transmitting the branch power usage and total power usage to a computer server; it also includes a computer server connected to the electronic power meter and monitoring the transmitted branch power usage.

[0006] Furthermore, the "Method and System for Detecting Leakage Current of Distribution Panel in Ungrounded System" (hereinafter referred to as "Patent Document 2") with publication number 10-2108138 includes an input terminal, multiple branch terminals that branch from the input terminal and supply power to the load and together with the input terminal constitute an ungrounded system, current transformers installed at each branch terminal, a measuring instrument for measuring the current of the current transformers installed at each branch terminal, and a leakage current detection unit that receives the current measured from each measuring instrument and determines the branch terminals with different current directions among the branch terminals with the measuring instruments as the branch terminals where leakage current occurs.

[0007] Traditional smart distribution panels, like those in Patent Document 1, are smart distribution panels with added sensors and communication functions, providing various additional functions such as power metering. In contrast, distribution panels with leakage current detection functions, like those in Patent Document 2, can provide fire prevention functions through leakage current detection.

[0008] However, for switchboards using a three-phase four-wire system, the mixing of single-phase and three-phase loads can lead to unbalanced current flow. Furthermore, within single-phase loads, current imbalances may occur depending on the equipment and its purpose. Traditional switchboards often lack the capability to effectively reduce this unbalanced load current. In other words, severe imbalance can cause losses in transformers and lines, and may also lead to power quality degradation due to malfunctions of protective relays.

[0009] The present invention is proposed to solve the above-mentioned problems. The problem to be solved by the present invention is to provide an intelligent power distribution panel for apartment buildings to reduce unbalanced load current.

[0010] In addition, another problem that this invention aims to solve is to provide an intelligent switchboard that detects resistive leakage current (Igr) by measuring phase difference to protect the power system. Summary of the Invention

[0011] An embodiment of the present invention discloses an intelligent power distribution panel for apartment buildings to reduce unbalanced load current.

[0012] The disclosed intelligent distribution panel is used in apartment building distribution panels for distributing three-phase AC power input from the main distribution panel in a three-phase four-wire system to single-phase or three-phase loads. It includes: a main circuit breaker that receives the three-phase power supply and disconnects it according to a control signal upon detecting overcurrent or leakage current; a busbar for distributing the three-phase power input through the main circuit breaker; phase current transformers for detecting phase currents flowing through the three-phase lines; a zero-sequence current transformer for detecting leakage current; an instrument transformer for detecting the voltage of the three-phase lines; and multiple single-phase distribution... The single-phase distribution unit cuts off one phase of the three-phase power supply from the busbar according to the phase cutoff control signal and supplies it to the corresponding single-phase load, and detects and outputs the single-phase load current; the distribution panel controller receives the single-phase load current supplied from the single-phase distribution unit to the corresponding single-phase load, receives the voltage input from the instrument transformer, receives the detection value input from the phase current transformer and the zero-sequence current transformer to detect leakage current, calculates the load current imbalance, and then generates a phase cutoff signal to reduce the load current imbalance to control the phase cutoff device of the single-phase distribution unit.

[0013] The single-phase power distribution unit may include: an R-phase switch, used to connect the R-phase line to a single-phase load or disconnect it from the single-phase load according to a phase disconnection signal; an S-phase switch, used to connect the S-phase line to a single-phase load or disconnect it from the single-phase load according to a phase disconnection signal; a T-phase switch, used to connect the T-phase line to a single-phase load or disconnect it from the single-phase load according to a phase disconnection signal; and a single-phase current transformer, used to detect the single-phase load current supplied to the single-phase load through the R-phase switch, S-phase switch, or T-phase switch, and transmit it to the distribution panel controller.

[0014] The single-phase power distribution unit may also include a branch circuit breaker for cutting off the power supplied to the single-phase load through an R-phase switch, an S-phase switch, or a T-phase switch.

[0015] The distribution panel controller includes: a resistive leakage current detection module, which receives detection values ​​from current transformers of each phase and voltage transformers for instruments, calculates the apparent power and active power to obtain the power factor, and receives the composite leakage current value from the zero-sequence current transformer, and detects the resistive leakage current using phase difference measurement; and a load current imbalance reduction module, which calculates the three-phase current imbalance of the main three-phase system, and when it exceeds the allowable reference value, calculates the load current imbalance of the single-phase distribution system, and when it exceeds the allowable reference value, reduces the load current imbalance by using a phase cutoff device.

[0016] The load current imbalance reduction module includes: a load current detection unit for detecting the load current supplied to each single-phase load; a load ammeter for recording the load current value input from each single-phase distribution unit at predetermined time units; a three-phase current imbalance calculation unit for receiving the phase current values ​​from each phase current detection unit to calculate the three-phase current imbalance; and a three-phase current imbalance comparison unit for comparing the calculated three-phase current imbalance rate with an allowable reference value. When the reference value is exceeded, the load current imbalance rate is calculated based on the recorded values ​​of the load ammeter. The load current imbalance calculation unit calculates the load current imbalance using the recorded values ​​of the load current meter according to the requirements of the three-phase current imbalance comparison unit. The load current imbalance comparison unit compares the calculated load current imbalance rate with the allowable reference value, and requires phase disconnection when it exceeds the allowable value. The phase disconnection signal generation unit generates a phase disconnection signal that can balance the load current by comparing the average load current of each single-phase distribution unit according to the phase disconnection requirements of the load current imbalance comparison unit. The phase disconnection execution unit executes phase disconnection according to the phase disconnection signal generated by the phase disconnection signal generation unit.

[0017] The present invention can achieve the following beneficial effects: According to the embodiments of the present invention, after calculating the unbalance generated in the three-phase current in the three-phase stage of the trunk system, the unbalance of the load current of the distribution system is calculated. When the unbalance rate exceeds the allowable value, the load current is equalized by phase disconnection, thereby achieving the effect of saving resources while significantly improving the unbalance rate.

[0018] Furthermore, according to embodiments of the present invention, it is possible to quickly detect only the resistive leakage current that may cause a fire in the composite leakage current of the zero-sequence current transformer and cut off the leakage current, thereby preventing fires caused by leakage current.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0021] Figure 1 This is a schematic diagram showing the apartment building power distribution system to which the present invention is applied.

[0022] Figure 2 This is a schematic diagram illustrating an intelligent power distribution panel for reducing unbalanced load current in an apartment building according to an embodiment of the present invention.

[0023] Figure 3 yes Figure 2 The diagram shown is a detailed block diagram of the distribution panel controller.

[0024] Figure 4 This is a graph showing the relationship between the combined leakage current caused by resistive and capacitive leakage currents.

[0025] Figure 5 This diagram illustrates the concept of detecting resistive leakage current according to an embodiment of the present invention.

[0026] Figure 6 This is a flowchart illustrating the steps for reducing load current imbalance according to an embodiment of the present invention.

[0027] 10: Incoming distribution panel; 20-1 to 20-n: Single-phase distribution section;

[0028] 30: Three-phase load; 100: Intelligent distribution panel;

[0029] 110R, 110S, 110T, 110N: Busbars; 112: Main circuit breaker;

[0030] 114: Zero-sequence current transformer; 116R, 116S, 116T: Current transformers;

[0031] 118: Transformer for instruments; 120-1 to 120-n: Single-phase power distribution unit;

[0032] 122: Switch; 124: Single-phase current transformer;

[0033] 126: Branch circuit breaker; 130: Three-phase power distribution unit;

[0034] 140: Distribution panel controller; 142: Resistive leakage current detection module;

[0035] 144: Load current imbalance reduction module. Detailed Implementation

[0036] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0037] The advantages and features of the present invention, as well as the methods for implementing them, are described below with reference to the appendix. Figure 1 The detailed embodiments will become clear.

[0038] However, the present invention is not limited to the embodiments disclosed below, but can be implemented in many different forms. These embodiments are provided to make the disclosure of the present invention complete and to fully inform those skilled in the art of the present invention of its scope. The present invention is defined only by the scope of the claims.

[0039] The specific implementation of the invention will now be described in detail with reference to the accompanying drawings. Regardless of their relevance to the drawings, the same part numbers refer to the same constituent elements, and "and / or" includes each of the mentioned items and all combinations thereof.

[0040] Although terms like "first" and "second" are used to describe various constituent elements, these constituent elements are certainly not limited by these terms. These terms are merely used to distinguish one constituent element from others.

[0041] Therefore, the first constituent element mentioned below may also be a second constituent element within the scope of the technical concept of the present invention.

[0042] The terminology used in this specification is for illustrative purposes and is not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise. The terms "comprises" and / or "comprising" as used in this specification do not exclude the presence or addition of more than one of the mentioned constituent elements.

[0043] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) are to be used in the sense that they are commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be ideally or excessively interpreted unless explicitly defined.

[0044] Spatially relative terms such as "below," "below," "lower," "above," and "upper" can be used to describe the relationship between one component and other components, as shown in the accompanying drawings. In addition to the directions shown in the drawings, spatially relative terms should also be understood in use or operation to include terms indicating different orientations between components. For example, if the components shown in the drawings are flipped, a component described as "below" or "below" of other components might be located "above" of other components. Therefore, the exemplary term "below" can encompass both the "below" and "above" directions. Components can also be oriented in other directions, so spatially relative terms can be interpreted according to orientation.

[0045] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0046] Figure 1This is a schematic diagram illustrating the apartment building power distribution system to which the present invention is applied.

[0047] Reference Figure 1 In the electrical distribution room of an apartment building, such as an apartment complex, a distribution panel 10 is installed. This panel converts the 22.9kV ultra-high voltage supplied by Korea Electric Power Corporation to low voltage and supplies it to intelligent distribution panels 100 installed in the basements of each apartment building. The intelligent distribution panels 100 supply 220V single-phase power to multiple single-phase loads 20-1 to 20-n, and simultaneously supply three-phase power to three-phase loads 30. Here, the single-phase loads 20-1 to 20-n can be household loads connected through the distribution panels of each household in the corresponding building, and the three-phase loads can be elevators or motors.

[0048] According to an embodiment of the present invention, the intelligent distribution panel 100 is equipped with a phase disconnection switch capable of disconnecting one of the three phases supplied to each single-phase load 20-1 to 20-n, so that when the unbalanced load current exceeds the allowable value while monitoring the load current, the imbalance can be eliminated by phase disconnection.

[0049] Furthermore, the intelligent distribution panel 100 according to an embodiment of the present invention detects resistive leakage current by applying phase difference measurement to leakage current detection, thereby providing accurate and rapid protection action.

[0050] Figure 2 This is a schematic diagram illustrating an intelligent power distribution panel for reducing unbalanced load current in an apartment building according to an embodiment of the present invention. Figure 3 yes Figure 2 The diagram shown is a detailed block diagram of the distribution panel controller. Figure 4 This is a graph showing the relationship between the combined leakage current caused by resistive and capacitive leakage currents. Figure 5 This diagram illustrates the concept of detecting resistive leakage current according to an embodiment of the present invention. Figure 6 This is a flowchart illustrating the steps for reducing load current imbalance according to an embodiment of the present invention.

[0051] like Figure 2 As shown, according to an embodiment of the present invention, the intelligent distribution panel 100 includes busbars 110R, 110S, 110T, 110N, a main circuit breaker 112, a zero-sequence current transformer 114, an R-phase current transformer 116R, an S-phase current transformer 116S, a T-phase current transformer 116T, an instrument transformer 118, multiple single-phase distribution sections 120-1 to 120-n for supplying single-phase power to single-phase loads 20-1 to 20-n, a three-phase distribution section 130, and a distribution panel controller 140, all installed in a distribution panel (not shown). The controller distributes the three-phase AC power input from the distribution panel 10 in a three-phase four-wire system to the single-phase loads 20-1 to 20-n or the three-phase load 30.

[0052] Reference Figure 2 The main circuit breaker 112 connects the three-phase four-wire (R, S, T, N) power supply from the distribution panel 10 to the corresponding busbars 110R, 110S, 110T, and 110N via power line cables, while simultaneously connecting or disconnecting the R, S, and T three-phase power supplies according to control signals. That is, based on the control signals from the distribution panel controller 140, it can perform a protective action of disconnecting the three-phase power supply when overcurrent or leakage current is detected. In embodiments of the present invention, although the main circuit breaker 118 is described as performing a leakage current disconnection action, a separate residual current circuit breaker is preferred.

[0053] Busbars 110R, 110S, 110T, and 110N are main power lines used to distribute the three-phase power input through the main circuit breaker 112.

[0054] Phase current transformers are devices used to detect the phase current flowing through each phase line and provide it to the distribution panel controller 140. The R-phase current transformer 116R detects the phase current flowing through the R-phase line 110R and provides it to the distribution panel controller 140. The S-phase current transformer 116S detects the phase current flowing through the S-phase line 110S and provides it to the distribution panel controller 140. The T-phase current transformer 116T detects the phase current flowing through the T-phase line 110T and provides it to the distribution panel controller 140.

[0055] The zero-sequence current transformer 114 is a sensor used to detect leakage current. It comes in wound and through-type versions. The through-type typically consists of an iron core, a primary circuit, a primary conductor through which current flows, and a secondary winding wound around the iron core. When the primary current generates magnetic flux in the iron core of the zero-sequence current transformer, this flux generates a secondary current. If the primary current does not include leakage current, the total magnetic flux is zero. However, if the sum of the three-phase currents is not zero due to leakage current, the total magnetic flux is also not zero. In this case, the remaining magnetic flux flows through the iron core in the form of Φ, thus linking with the secondary coil of the zero-sequence current transformer. Therefore, a voltage is induced in the secondary coil, causing current to flow through it, thereby enabling the detection of leakage current.

[0056] The instrument transformer 118 is designed to detect phase-to-phase or line-to-line voltage in a three-phase circuit. It consists of multiple instrument transformers connected to the corresponding circuits. Typically, the phase-to-phase voltage is 380V and the single-phase voltage is 220V.

[0057] According to the control signal from the distribution panel controller 140, the single-phase power distribution units 120-1 to 120-n cut off one phase of the three-phase power supply of the bus and supply it to the corresponding single-phase loads 20-1 to 20-n. At the same time, they detect the single-phase load current and provide it to the distribution panel controller 140. Therefore, the single-phase power distribution units 120-1 to 120-n include: an R-phase switch 122R that connects the R-phase bus 110R to the load-side wire 128-1 according to the R-phase disconnection signal of the distribution panel controller 140; an S-phase switch 122S that connects the S-phase bus 110S to the load-side wire 128-1 according to the S-phase disconnection signal; a T-phase switch 122T that connects the T-phase bus 110T to the load-side wire 128-1 according to the T-phase disconnection signal; a load-side wire 128-2 directly connected to the N-phase bus 110N; a single-phase current transformer 124 for detecting the single-phase load current; and a branch circuit breaker 126 for connecting any phase wire 128-1 passing through switches 122R, 122S, and 122T and the wire 128-2 connected to the neutral N bus 110N to the single-phase load 20 side or disconnecting their connection. In addition, although not shown in the figure, a zero-sequence current transformer can also be installed in the single-phase distribution section 120-1 to 120-n in order to detect leakage current in the single-phase system. When leakage occurs in the single-phase system, the branch switch 126 of the corresponding single-phase distribution section may also be cut off.

[0058] The three-phase power distribution section 130 is used to supply the three-phase power of the busbar to the three-phase load 30 through the branch circuit breaker 136.

[0059] like Figure 3 As shown, the distribution panel controller 140, which performs the unbalanced current reduction function and resistive leakage current detection function according to the embodiment of the present invention, is composed of a resistive leakage current detection module 142 and a load current unbalance reduction module 144. It receives the single-phase detection current supplied from the single-phase distribution sections 120-1 to 120-n to the corresponding single-phase loads 20-1 to 20-n, receives the three-phase voltage input from the instrument transformer 118, receives the detection value input from each phase current transformer 116R to 116T and the zero-sequence current transformer 114 to detect leakage current, calculates the load current unbalance rate, and then generates a phase cut-off signal for reducing unbalance to perform the phase cut-off operation of the single-phase distribution sections 120-1 to 120-n. Such a distribution panel controller 140 can be implemented by various processors such as microcontrollers with A / D conversion ports, digital signal processors (DSPs), network signal processors (NSPs), as well as computer peripherals, application-specific integrated circuits (ASICs), or embedded systems running the Linux operating system, and can execute corresponding functions through software mounted on the processor.

[0060] Reference Figure 3The resistive leakage current detection module 142 consists of a synthetic leakage current detection unit 142-1, a voltage detection unit 142-2, an R-phase current detection unit 142-3, an S-phase current detection unit 142-4, a T-phase current detection unit 142-5, an active power / apparent power calculation unit 142-6, a power factor calculation unit 142-7, a resistive leakage current calculation unit 142-8, a leakage current comparison unit 142-9, and a cut-off execution unit 142-10. It detects resistive leakage current by using phase difference measurement.

[0061] The synthetic leakage current detection unit 142-1 receives the detection value from the zero-sequence current transformer 114 and performs analog-to-digital conversion (ADC) to calculate the synthetic leakage current I0. Known techniques for detecting leakage current using the zero-sequence current transformer 114 include synthetic leakage current detection, frequency injection detection, low-frequency superposition, and average power calculation.

[0062] The composite leakage current (I0) detected by the zero-sequence current transformer (ZCT) is the vector sum of the resistive leakage current (Igr), capacitive leakage current (Igc), and inductive leakage current (Igl). The inductive leakage current (Igl) is typically very small in the circuit and can be ignored. The capacitive leakage current (Igc) is a component that leads the resistive leakage current (Igr) by 90° and flows due to the electrostatic capacitance between the power line and the ground, as well as the electrostatic capacitance to ground of the power lines of connected electrical products. Because the capacitive leakage current (Igc) flows as a displacement current, it will not cause electrical fires or electric shocks. However, the resistive leakage current (Igr) is a component in phase with the voltage and flows due to the deterioration of the insulation resistance to ground of the power line and the electrical products connected to the power line. When the resistive leakage current (Igr) flows, it generates Joule heat, which can potentially cause electrical fires or electric shocks. The relationship between this combined leakage current (I0), resistive leakage current (Igr), and capacitive leakage current (Igc) is shown in the following mathematical formula 1, and can be expressed in a rectangular coordinate system as follows: Figure 4 As shown in the figure.

[0063]

[0064] According to the above mathematical formula 1, since the combined leakage current (I0) can be obtained from the detection current of the zero-sequence current transformer 114, the resistive leakage current (Igr) can be calculated according to the following mathematical formula 2 as long as the angle θ is calculated.

[0065] I gr =I0cosθ (2)

[0066] According to the resistive leakage current detection module 142 of the present invention, the voltage detected by the voltage detection unit 142-2 is used as the reference voltage. The phase difference θ of the capacitive leakage current component in the leakage current measured by the zero-sequence current transformer 114 is calculated. Then, the resistive leakage current is separated and calculated by applying the vector decomposition formula.

[0067] The voltage detection unit 142-2 receives the phase-to-phase voltage and line voltage from the instrument transformer 118, reduces them to several hundred millivolts through a voltage divider circuit, and then performs an analog-to-digital converter (ADC) to detect the real-time voltage value; the R-phase current detection unit 142-3 receives the R-phase current from the R-phase current transformer 116R, converts it into a voltage signal, and then performs an ADC to detect the real-time R-phase current value; the S-phase current detection unit 142-4 receives the S-phase current from the S-phase current transformer 116S, converts it into a voltage signal, and then performs an ADC to detect the real-time S-phase current value; the T-phase current detection unit 142-5 receives the T-phase current from the T-phase current transformer 116T, converts it into a voltage signal, and then performs an ADC to detect the real-time T-phase current value.

[0068] The active power / apparent power calculation unit 142-6 applies integration to the outputs of the voltage detection unit 142-2 and the phase current detection units 142-3 to 142-5 to calculate the apparent power and active power in the following manner.

[0069] Apparent power is divided into active power and reactive power. Apparent power can be easily calculated by multiplying voltage and current. Active power is obtained by sampling voltage and current over a period of time, separating them into positive and negative components, and then adding them together. In other words, starting from zero voltage, the voltage sample value input to voltage detection unit 142-2 and the current sample values ​​input to each phase current detection unit 142-3 to 142-5 are used to calculate the apparent power. Figure 5 As shown, the apparent power is divided into an active power component, which consists of overlapping voltage and current, and a reactive power component, represented by a non-overlapping dashed line. During the apparent power calculation phase, these components are not distinguished; apparent power is calculated through integration.

[0070] Furthermore, in the active power calculation stage, the positive current part and the negative current part are calculated separately. After multiplying the current values, the power of the positive and negative parts is added together, and the remaining part is calculated as active power. In other words, the absolute values ​​of both positive and negative values ​​are taken, and the result of adding all the values ​​together is calculated as apparent power, distinguishing between the positive current part and the negative current part to calculate active power.

[0071] The power factor calculation unit 142-7 receives active power and apparent power from the active power / apparent power calculation unit 142-6, and calculates the power factor cosθ according to the following mathematical formula.

[0072]

[0073] The resistive leakage current calculation unit 142-8 calculates the resistive leakage current value according to the mathematical formula 2 described above, based on the cosθ input by the power factor calculation unit 142-7 and the composite leakage current I0 input by the composite leakage current detection unit 142-1.

[0074] The leakage current comparison unit 142-9 compares the calculated resistive leakage current value with a preset reference value. When the value exceeds the reference value, the cut-off execution unit 142-10 will trip the main circuit breaker 112 to cut off the power supply, thereby preventing fires caused by leakage current.

[0075] In this way, when the instantaneous value of the power supply voltage (V) and the instantaneous value of the combined leakage current (ic) are detected in the line, the average power (W) is calculated from these two signals, and then divided by the effective value of the power supply voltage (V) to calculate the resistive leakage current (Igr), the effective value of the resistive leakage current is shown in the following mathematical formula 4.

[0076]

[0077] In the above formula, the power supply voltage (v) of the circuit is a sine wave, V is the effective value of the power supply voltage (v), ω=2πf is the angular velocity, f is the power supply frequency, and the combined leakage current flowing through the line is a sine wave, as shown in the following mathematical formula.

[0078]

[0079] In mathematical formula 5, I0 is the effective value of the combined leakage current (i0), and θ is the phase angle between the power supply voltage (v) and the combined leakage current (i0). Here, the value of i0 obtained by integrating within the interval where the polarity of the power supply voltage (v) is positive (+) (0<ωt<π) is denoted as K1, and the value obtained by integrating within the interval where the polarity is negative (-) (π<ωt<2π) is denoted as K2, as shown in the following mathematical formula 6.

[0080]

[0081] Since \(\vert K1\vert=\vert K2\vert\) and \(I_{gr}=I_0\cos\theta\), the resistive leakage current (\(I_{gr}\)) can finally be calculated as shown in the following mathematical formula 7.

[0082]

[0083] Thus, according to an embodiment of the present invention, the resistive leakage current (I_{gr}\) can be calculated by integrating the composite leakage current detected by the zero-sequence current transformer over half a cycle of the power supply voltage through the controller (MCU) after A / D conversion.

[0084] On the other hand, such as Figure 6 As shown, the load current imbalance reduction module 144 of the distribution panel controller 140 records the load current of the three-phase and single-phase distribution sections of the main line in table S101 at certain time intervals. At this time, the phase current recording period of the three phases and the load current recording period can be different.

[0085] First, the unbalance of the three phases of the main line is calculated based on the three-phase current records. If it exceeds the preset allowable benchmark value, the unbalance of the distribution load current S102 to S104 is calculated.

[0086] The load current imbalance is calculated. If it exceeds the preset allowable reference value, a phase cut-off plan is formulated to reduce the load current imbalance. A phase cut-off signal is generated, and phase cut-off operations S105 to S107 are performed according to the phase cut-off signal.

[0087] Next, after performing the phase cut-off operation, the imbalance of the three phases of the main line is recalculated. If it has been improved to within the reference value, the operation ends; if it exceeds the reference value, the phase cut-off plan is changed, the phase cut-off signal is modified, and then the phase cut-off operation S108 to S110 is performed again.

[0088] Thus, according to an embodiment of the present invention, the load current imbalance reduction module 144 calculates the phase current imbalance in the three-phase stage of the trunk system and then calculates the load current imbalance in the distribution system, thereby improving the imbalance condition while saving computing resources. However, if phase disconnection operations are too frequent, it may lead to a decline in power quality. Therefore, appropriately setting the imbalance calculation cycle and the reference imbalance value to limit the phase disconnection cycle is a more ideal approach.

[0089] Refer to Figure 3 The load current imbalance reduction module 144 consists of a first load current detection unit 144-1, a second load current detection unit 142-2, an nth load current detection unit 144-n, a load ammeter 144-3, a three-phase current imbalance calculation unit 144-4, a three-phase current imbalance comparison unit 144-5, a load current imbalance calculation unit 144-6, a load current imbalance comparison unit 144-7, a phase cut-off signal generation unit 144-8, and a phase cut-off execution unit 144-9. After detecting the imbalance in layers, it can evenly distribute the load among the three phases, thereby reducing the load current imbalance.

[0090] The first load current detection unit 144-1 is used to detect the load current supplied from the current transformer 124 installed in the first single-phase distribution unit 120-1 to the first single-phase load 20-1 by CT1; the second load current detection unit 144-2 is used to detect the load current supplied from the current transformer 124 installed in the second single-phase distribution unit 120-2 to the second single-phase load 20-2 by CT2; the nth load current detection unit 144-n is used to detect the load current supplied from the current transformer 124 installed in the nth single-phase distribution unit 120-n to the nth single-phase load 20-n by CTn.

[0091] The load current meter 144-3 is used to record the load current values ​​input from each single-phase distribution section 120-1 to 120-n in a predetermined time unit in the manner shown in Table 1 below, so as to calculate the load imbalance rate.

[0092] distinguish Current phase Load current First Single-Phase Power Distribution Section S x111,x112,x113,...... Second Single-Phase Power Distribution Section R y111,y112,y113,...... Third Single-Phase Power Distribution Section S xx111,xx112,xx113,... ... ... ...

[0093] Table 1

[0094] Referring to Table 1 above, it can be seen that the S switch 122S of the first single-phase distribution unit 120-1 is currently in the open state, while the T and R switches 122T and 122R are in the closed state. This indicates that the S-phase power supply of the main line is supplying power to the load side 20-1. Similarly, the R switch 122R of the second single-phase distribution unit 120-2 is currently in the open state, while the T and S switches 122T and 122S are in the closed state. This indicates that the R-phase power supply of the main line is supplying power to the load side 20-2. Furthermore, the load currents of the first and second single-phase distribution units 120-1 and 120-2 are sampled at regular time intervals and recorded in the load current record.

[0095] The three-phase current imbalance detection unit 144-4 receives phase current values ​​from each phase current detection unit 142-3 to 142-5 to detect the imbalance of the three-phase current. For this purpose, the three-phase current imbalance detection unit 144-4 also includes a current table for each phase. After calculating the average current of each phase, the three-phase imbalance rate can be calculated according to the following mathematical formula 8 by comparing the three phases. Thus, in this embodiment of the invention, since an average value over a period of time is used instead of instantaneous values, the imbalance rate can be calculated more accurately.

[0096]

[0097] The three-phase current imbalance comparison unit 144-5 compares the calculated three-phase current imbalance rate with the allowable reference value. When the reference value is exceeded, in order to determine the load current imbalance of each single-phase distribution unit 120-1 to 120-n, the load current imbalance calculation unit 144-6 is required to calculate the load current imbalance.

[0098] The load current imbalance calculation unit 144-6 calculates the load current imbalance by phase based on the requirements of the three-phase current imbalance comparison unit 144-5 and the recorded values ​​of the load current meter 144-3.

[0099] For example, after calculating the average load current of each single-phase distribution section in load current table 144-3, the values ​​are summed phase by phase to calculate the three-phase load current imbalance. In Table 1, the load current of the first single-phase distribution section 120-1 is phase S, so it is added to the average load current of the third single-phase distribution section 120-3, which also uses phase S. After summing the load currents of each phase in the same way, the load current imbalance rate is calculated according to mathematical formula 4.

[0100] The load current imbalance comparison unit 144-7 compares the load current imbalance value with the allowable reference value. When the allowable value is exceeded, the phase cut-off signal generation unit 144-8 is required to generate a phase cut-off signal.

[0101] The phase cutoff signal generation unit 144-8, based on the phase cutoff requirements of the load current imbalance comparison unit 144-7, compares the average load current of each single-phase distribution unit 120-1 to 120-n, determines the phase with the maximum current and the phase with the minimum current, and then selects the single-phase distribution unit with the load current that minimizes the difference between the two, generating a phase cutoff signal for that single-phase distribution unit. For example, when the load current of phase R is 130A, the load current of phase S is 110A, and the load current of phase T is 80A, the average load current is approximately 106A. Furthermore, to reduce the load current imbalance, it is ideal to switch the load of the single-phase distribution unit using the maximum current (phase R) to the minimum current (phase T), or vice versa. Therefore, from single-phase distribution sections using either phase T or phase R, the single-phase distribution section whose load current is closest to half the difference between the maximum and minimum current values ​​is selected. When this single-phase distribution section is using phase T, a signal to switch to phase R is generated; when it is using phase R, a phase-cut-off signal to switch to phase T is generated. That is, in the example above, the difference between the maximum current of 130A and the minimum current of 80A is 50A. Therefore, the single-phase distribution section with a load current closest to half of this (25A) is found. If this single-phase distribution section is using phase T, a signal to switch to phase R is generated; if it is using phase R, a phase-cut-off signal to switch to phase T is generated.

[0102] The phase cut-off execution unit 144-9 performs the phase cut-off operation based on the phase cut-off signal generated by the phase cut-off signal generation unit 144-8, and can request the three-phase current imbalance calculation unit 144-4 to recalculate the imbalance after the phase cut-off.

[0103] In summary, the present invention has been described with reference to one embodiment illustrated in the figures; however, those skilled in the art will understand that various modifications and other equivalent embodiments are possible.

Claims

1. A smart distribution panel for apartment buildings to reduce unbalanced load current, characterized in that, include: The main circuit breaker is used to receive three-phase power and disconnect the three-phase power supply when overcurrent or leakage current is detected according to the control signal. Busbar, used to distribute the three-phase power input through the main circuit breaker; Phase current transformers are used to detect the phase current flowing through a three-phase line; Zero-sequence current transformer is used to detect leakage current; Transformers for instruments are used to detect the voltage of three-phase lines; Multiple single-phase power distribution units cut off one phase of the three-phase power supply of the bus according to the phase cutoff control signal and supply it to the corresponding single-phase load, while detecting and outputting the single-phase load current. as well as The switchboard controller receives the single-phase load current supplied from the single-phase distribution section to the corresponding single-phase load, receives the voltage input from the instrument transformer, receives the detection values ​​input from the phase current transformer and the zero-sequence current transformer to detect leakage current, calculates the load current imbalance, and then generates a phase cutoff signal to reduce the load current imbalance in order to control the phase cutoff device of the single-phase distribution section.

2. The intelligent power distribution panel for reducing unbalanced load current in apartment buildings according to claim 1, wherein, The single-phase power distribution unit includes: R-phase switch is used to connect the R-phase line to a single-phase load or disconnect it from a single-phase load according to the phase disconnection signal. An S-phase switch is used to connect an S-phase line to a single-phase load or disconnect it from a single-phase load based on a phase disconnection signal. A T-phase switch is used to connect a T-phase line to a single-phase load or disconnect it from a single-phase load based on a phase disconnection signal; and A single-phase current transformer is used to detect the single-phase load current supplied to the single-phase load through the R-phase switch, S-phase switch or T-phase switch and transmit it to the distribution panel controller.

3. The intelligent power distribution panel for reducing unbalanced load current in apartment buildings according to claim 2, wherein, The single-phase power distribution unit also includes: A branch circuit breaker is used to disconnect the power supplied to a single-phase load through the R-phase switch, S-phase switch, or T-phase switch.

4. The intelligent power distribution panel for reducing unbalanced load current in apartment buildings according to claim 1, wherein, The switchboard controller includes: The resistive leakage current detection module receives detection values ​​from current transformers and voltage transformers for instruments in each phase, calculates the apparent power and active power and then obtains the power factor, and receives the composite leakage current value from the zero-sequence current transformer, and uses phase difference measurement to detect the resistive leakage current. The load current imbalance reduction module calculates the three-phase current imbalance of the main three-phase system. When it exceeds the allowable benchmark value, it calculates the load current imbalance of the single-phase distribution system. When it exceeds the allowable benchmark value, it reduces the load current imbalance by using a phase cut-off device.

5. The intelligent power distribution panel for reducing unbalanced load current in apartment buildings according to claim 4, wherein, The load current imbalance reduction module includes: The load current detection unit is used to detect the load current supplied to each single-phase load; The load current meter records the load current value input from each single-phase power distribution unit at predetermined time units; The three-phase current imbalance calculation unit receives the phase current values ​​from each phase current detection unit to calculate the three-phase current imbalance. The three-phase current imbalance comparison unit compares the calculated three-phase current imbalance rate with the allowable reference value. When the reference value is exceeded, the load current imbalance rate is calculated based on the recorded value of the load ammeter. The load current imbalance calculation unit calculates the load current imbalance using the recorded values ​​of the load ammeter, according to the requirements of the three-phase current imbalance comparison unit. The load current imbalance comparison unit compares the calculated load current imbalance rate with the allowable reference value, and requires phase disconnection when the allowable value is exceeded. The phase cut-off signal generation unit generates a phase cut-off signal that can balance the load current by comparing the average load current of each single-phase distribution unit according to the phase cut-off requirement of the load current imbalance comparison unit. The phase cut-off execution unit performs phase cut-off based on the phase cut-off signal generated by the phase cut-off signal generation unit.

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