Monitoring device and method for ground insulation of ungrounded system

Abstract

The embodiment of the invention provides an ungrounded system ground insulation monitoring device and method, the device comprises a voltage measuring tool and a fling-cut switch, the internal resistance of the voltage measuring tool is used as the parallel resistance, and the voltage between the positive electrode and the negative electrode of a direct-current power supply, the voltage to ground of the positive electrode of the direct-current power supply and the voltage to ground of the negative electrode of the direct-current power supply are measured; and based on the three measured voltage values, substituting the internal resistance of a known voltage measurement tool, calculating the insulation resistance to ground of the system, and monitoring whether the ungrounded system is insulated to ground or not.

Description

Technical Field

[0001] This document relates to the field of insulation monitoring technology, and in particular to a device and method for monitoring the insulation of an ungrounded system to ground. Background Art

[0002] In an ungrounded system, electrical equipment is not directly connected to the ground, so the insulation status of the system is critical to the safety and reliability of the equipment. It is necessary to monitor the insulation status to detect potential insulation failures in a timely manner. Insulation monitoring is an important measure to ensure the normal operation of electrical systems, especially in environments with high electrical safety requirements such as industry and medical.

[0003] As equipment ages, the environment changes, and external influences occur, insulation performance may gradually decline, leading to faults such as leakage and short circuits. The insulation resistance monitoring requirements have been changed from optional requirements to mandatory requirements. Therefore, regular monitoring of insulation resistance is necessary. Traditional insulation resistance measurement methods usually use high-voltage testing, using a voltage measurement tool. During the test, the voltage reading is unstable, and there is a high possibility that human factors will cause deviations in the test results. Existing insulation resistance measurement methods based on the bridge principle must consider the influence of the internal resistance of the voltage measurement tool. The internal resistance of the voltage measurement circuit and the distributed capacitance of the measured system (especially the Y capacitor) affect the test speed and measurement accuracy. Summary of the invention

[0004] One or more embodiments of the present specification provide a monitoring device for the insulation of an ungrounded system to ground, including a voltage measuring tool and a switching switch. The internal resistance of the voltage measuring tool is used as a parallel resistance. By switching the switching switch, the voltage between the positive and negative poles of a DC power supply, the voltage of the positive pole of the DC power supply to ground, and the voltage of the negative pole of the DC power supply to ground are measured respectively. Based on the three measured voltage values, the known internal resistance of the voltage measuring tool is substituted to calculate the insulation resistance of the system to ground.

[0005] Furthermore, when only one voltage measurement tool is used, the automatic test of the three voltages can be achieved by switching the switching switches, and at this time, the number of the switching switches is at least four.

[0006] Furthermore, when measuring the voltage to ground, the internal resistance of the voltage measuring tool and the capacitance to ground of the electrode being measured form an RC equivalent circuit, and the capacitance to ground is a constant value for the same object being measured.

[0007] Furthermore, the voltage measurement tool comprises an internal resistor, an analog-to-digital converter ADC and a single-chip microcomputer, wherein the internal resistor of the voltage detection device is a plurality of resistors connected in series or a voltage divider resistor.

[0008] Furthermore, the voltage measurement tool also includes a buffer amplifier.

[0009] Further, the internal resistance value of the voltage measurement tool is a typical value of 1 MΩ, 10 MΩ, or other set values.

[0010] One or more embodiments of this specification provide a method for monitoring the insulation of an ungrounded system to the ground, including: using the internal resistance of a voltage measurement tool as a shunt resistor, measuring the voltage between the positive and negative poles of a DC power supply, the voltage of the positive pole of the DC power supply to the ground, and the voltage of the negative pole of the DC power supply to the ground respectively, and substituting the measured three voltage values into the known internal resistance of the voltage measurement tool to calculate the insulation resistance of the system to the ground.

[0011] Further, based on the measured voltages of the positive and negative poles of the DC power supply to the ground, the voltage of the positive pole of the DC power supply to the ground, and the voltage of the negative pole of the DC power supply to the ground, the specific method for calculating the insulation resistance is as follows:

[0012] Insulation resistance R i Take the smaller value of R1 and R2. If U1 > U2, the insulation resistance calculation method is as follows:

[0013]

[0014] If U1 < U2, the insulation resistance calculation method is as follows:

[0015]

[0016] Among them, R i is the insulation resistance; R1 is the equivalent insulation resistance of the positive pole of the DC power supply to the ground; R2 is the equivalent insulation resistance of the negative pole of the DC power supply to the ground; U0 is the voltage between the positive and negative poles of the DC power supply, U1 is the voltage of the positive pole of the DC power supply to the ground; U2 is the voltage of the negative pole of the DC power supply to the ground; R0 is the internal resistance of the voltage measurement tool; U0, U1, U2 take absolute values.

[0017] Further, the voltage measurement tool is a conventional multimeter.

[0018] By adopting the embodiment of the present invention, regarding the internal resistance of the voltage measurement tool as a parallel resistor, while affecting the balance of the bridge, voltage measurement is achieved; the minimum system is a voltage measurement tool with a known internal resistance; at least only 4 fast switching switches need to be added to perform a fast test, and a single test only takes a few milliseconds, which can be used for DC systems and can also be used for AC systems; the internal resistance of the voltage measurement tool can be adjusted according to the insulation monitoring result, which can avoid affecting the system insulation monitoring result and at the same time achieve fast detection.

[0019] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features, and advantages of the present invention more obvious and understandable, the following specifically gives the specific embodiments of the present invention. Brief Description of the Drawings

[0020] In order to more clearly illustrate one or more embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0021] Figure 1 An internal circuit diagram of a voltage measurement tool provided for one or more embodiments of this specification;

[0022] Figure 2 A minimum system circuit diagram of a monitoring device for insulation of an ungrounded system to ground provided by one or more embodiments of the present specification;

[0023] Figure 3 A circuit diagram of a monitoring device for ground insulation of an ungrounded system for measuring a DC+ to DC- voltage U0 provided in one or more embodiments of this specification;

[0024] Figure 4 A circuit diagram of a monitoring device for ground insulation of an ungrounded system for measuring a DC+ to PE voltage U1 provided in one or more embodiments of this specification;

[0025] Figure 5 A circuit diagram of a monitoring device for ground insulation of an ungrounded system for measuring a DC- to PE voltage U2 provided in one or more embodiments of this specification;

[0026] Figure 6 A monitoring device for ground insulation of an ungrounded system provided in one or more embodiments of the present specification uses two voltage measurement tools to simultaneously measure U0 and U1 schematic diagram;

[0027] Figure 7 A monitoring device for ground insulation of an ungrounded system provided in one or more embodiments of the present specification uses two voltage measurement tools to simultaneously measure U0 and U2 schematic diagram;

[0028] Figure 8 A monitoring device for insulation of an ungrounded system to ground provided in one or more embodiments of this specification uses two voltage measurement tools to measure U0 schematic diagram;

[0029] Fig. 9 A monitoring device for insulation of an ungrounded system to ground provided in one or more embodiments of this specification uses two voltage measurement tools to measure U1 schematic diagram;

[0030] Fig.10A monitoring device for ground insulation of an ungrounded system provided in one or more embodiments of the present specification uses two voltage measurement tools to measure the schematic diagram of U2. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solutions in one or more embodiments of this specification, the following will be combined with the drawings in one or more embodiments of this specification to clearly and completely describe the technical solutions in one or more embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on one or more embodiments of this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this document.

[0032] According to an embodiment of the present invention, a monitoring device for insulation of an ungrounded system to ground is provided, specifically comprising a voltage measuring tool and a switching switch, wherein the voltage measuring tool comprises an internal resistance, an analog-to-digital converter ADC and a single-chip microcomputer, and the switching switch is used to automatically test the voltage measuring tool. When only one voltage measuring tool is used, the automatic test of three voltages can be realized by switching the switching switch, and at this time, the switching switches are at least four, wherein the internal resistance of the voltage detection device is a plurality of resistors connected in series or a voltage divider resistor. When monitoring is performed, the internal resistance of the voltage measuring tool is used as a parallel resistance, and by switching the switching switch, the voltage between the positive and negative poles of the DC power supply, the voltage of the positive pole of the DC power supply to the ground, and the voltage of the negative pole of the DC power supply to the ground are measured respectively. Based on the three measured voltage values, the known internal resistance of the voltage measuring tool is substituted to calculate the insulation resistance of the system to the ground.

[0033] Figure 1 A schematic diagram of an internal circuit of a voltage detection device provided in one or more embodiments of this specification, such as Figure 1 As shown, R 01 +R 02 The internal resistance R0 of the voltage measurement tool can be realized by multiple resistors in series, or it can be a dedicated voltage divider resistor. The size of R0 is selected according to the needs of the system under test. It can be a typical value such as 1MΩ, 10MΩ, or other values. Taking the measured voltage as 1000V as an example, when R 01 =999kΩ, R 02 =1kΩ or R 01 =9.9MΩ, R 02 =10kΩ, R 02 The voltage on the ADC is 1V, and the ADC measures R 02 The voltage on R 01 and R 02The measured input voltage can be deduced from the proportional relationship. The voltage measurement tool further includes a buffer amplifier (voltage follower). At this time, R 01 or R 02 The current flowing into the ADC can be ignored, and high-precision voltage measurement can be achieved. When the input impedance of the selected ADC is high enough relative to R 02 The buffer amplifier (voltage follower) can be omitted.

[0034] The internal resistance of the voltage measurement tool can be adjusted according to the measured object to improve the test speed: when measuring the voltage to ground, the internal resistance R0 of the voltage measurement tool and the Y capacitor form an RC equivalent circuit. The capacitance of the Y capacitor is fixed. With a smaller R0 value, the time constant of the RC circuit is small, the stabilization time during voltage measurement is short, and the test speed is fast. The capacitance to ground is a fixed value for the same measured object. Among them, R0 should not be too small, especially when multiple insulation monitoring devices are working simultaneously, which will affect the insulation monitoring results.

[0035] Figure 2 This is a schematic diagram of the minimum system of an insulation monitoring device provided by one or more embodiments of this specification. R0 is the internal resistance of the voltage measurement tool, R1 is the equivalent insulation resistance of DC+ to ground, and it is > 10 MΩ under normal conditions. R2 is the equivalent insulation resistance of DC- to ground, and it is > 10 MΩ under normal conditions.

[0036] First, close switches K1 and K4, and open switches K2 and K3, and measure U0 (take the absolute value). Measure the voltage U0 of DC+ to DC- (bus voltage). As Figure 3 shown, ignoring the internal resistance of the DC charger and / or the battery pack, the bus voltage U0 is independent of R0, R1, and R2;

[0037] Then, close switches K1 and K3, and open switches K2 and K4, and measure U1 (take the absolute value). Measure the voltage U1 of DC+ to PE. As Figure 4 shown;

[0038] Finally, close switches K2 and K4, and open switches K1 and K3, and measure U2 (take the absolute value). Measure the voltage U2 of DC- to PE. As Figure 5 shown.

[0039] Each time the switching switch is toggled, all switches should be opened first, and then some of them should be closed according to the requirements.

[0040] The insulation resistance R i is the smaller one of R1 and R2. If U1 > U2, it can be calculated according to Formula 3:

[0041]

[0042] If U1 < U2, it can be calculated according to the formula

[0043]

[0044] When using dual voltage measurement tools for testing, the specific test method is as follows: Figure 6 and Figure 7 As shown, U0 and U1 are measured and U0 and U2 are measured respectively.

[0045] The measurement method of U1 and U2 is the same as above:

[0046] Open switches K2 and K4, close switches K1 and K3, and measure U1 (take the absolute value);

[0047] Open switches K1 and K3, close switches K2 and K4, and measure U2 (take the absolute value).

[0048] Each time you switch the switch, you should first open all switches and then close some of them as needed.

[0049] This method has an additional voltage measurement tool connected between DC+ and DC-, which can continuously monitor U0 and can also measure at intervals. The derived formulas for insulation resistance are shown in Formula 3 and Formula 4 above.

[0050] Another method of testing using a dual voltage measurement tool is as follows Figure 8-10 As shown:

[0051] First, close switches K1, K2, K3, K4 and measure U 01 , U 02 (take the absolute value), two voltage measurement tools measure U0 (bus voltage), such as Figure 8 As shown, U0=U 01 +U 02 ;

[0052] Then open switches K3 and K4, close switches K1 and K2, and measure U1 (take the absolute value), such as Fig. 9 shown.

[0053] Finally, open switches K1 and K2, close switches K3 and K4, and measure U2 (take the absolute value), such as Fig.10 shown.

[0054] The derived formulas for insulation resistance are shown in Formula 3 and Formula 4 above.

[0055] The voltage measuring tool in this embodiment may be a conventional multimeter.

[0056] The voltage detection device of this embodiment can achieve online monitoring for active circuits and can be used for passive circuit detection after being externally powered. The voltage detection device of this embodiment can also be used for DC+ and DC- ground insulation monitoring during the charging process of electric vehicles, as well as for insulation monitoring of electric vehicles during driving.

[0057] This embodiment provides a monitoring method for a monitoring device based on the above-mentioned ungrounded system ground insulation. Using the internal resistance of the voltage measurement tool as the shunt resistance, measure the voltage between the positive and negative poles of the DC power supply, the voltage of the positive pole of the DC power supply to the ground, and the voltage of the negative pole of the DC power supply to the ground respectively. Based on the three measured voltage values, substitute the known internal resistance of the voltage measurement tool to calculate the system ground insulation resistance.

[0058] Among them, based on the measured voltage of the positive and negative poles of the DC power supply to the ground and the equivalent insulation resistance of the positive and negative poles of the DC power supply to the ground, the specific method for calculating the insulation resistance is as follows:

[0059] Insulation resistance R i Take the smaller value of R1 and R2. If U1>U2, the insulation resistance calculation method is as follows:

[0060]

[0061] If U1<U2, the insulation resistance calculation method is as follows:

[0062]

[0063] In the formula, R i is the insulation resistance; R1 is the equivalent insulation resistance of the positive pole of the DC power supply to the ground; R2 is the equivalent insulation resistance of the negative pole of the DC power supply to the ground; U0 is the voltage between the positive and negative poles of the DC power supply, U1 is the voltage of the positive pole of the DC power supply to the ground; U2 is the voltage of the negative pole of the DC power supply to the ground; R0 is the internal resistance of the voltage measurement tool; U0, U1, U2 take absolute values.

[0064] The beneficial effects of the present invention are as follows:

[0065] The present invention regards the internal resistance of the voltage measurement tool as a parallel resistance, realizes voltage measurement while affecting the balance of the bridge; the minimum system is a voltage measurement tool with a known internal resistance; at least only 4 fast switching switches need to be added to perform a quick test, and a single test only takes a few milliseconds, which can be used for DC systems and can also be used for AC systems; the internal resistance of the voltage measurement tool can be adjusted according to the insulation monitoring results, which can avoid affecting the system insulation monitoring results and at the same time achieve quick detection.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A monitoring device for insulation of an ungrounded system to ground, characterized in that: It includes a voltage measurement tool and a switching switch. Using the internal resistance of the voltage measurement tool as the shunt resistor, by switching the switching switch, measure the voltage between the positive and negative poles of the DC power supply, the voltage of the positive pole of the DC power supply to the ground, and the voltage of the negative pole of the DC power supply to the ground respectively. Based on the three measured voltage values and substituting the known internal resistance of the voltage measurement tool, calculate the insulation resistance of the system to the ground.

2. The device according to claim 1, characterized in that When only one voltage measurement tool is used, the automatic test of the three voltages is realized by switching the switching switch. At this time, the switching switch is at least four.

3. The device according to claim 1, characterized in that When measuring the voltage to the ground, the internal resistance of the voltage measurement tool and the capacitance to the ground of the measured electrode form an RC equivalent circuit, and the capacitance to the ground is a fixed value for the same measured object.

4. The device according to claim 1, characterized in that The voltage measurement tool includes an internal resistance, an analog-to-digital converter ADC, and a single-chip microcomputer. Among them, the internal resistance of the voltage measurement tool is several resistors in series or the resistor of a voltage divider.

5. The device according to claim 1, characterized in that The voltage measurement tool also includes a buffer amplifier.

6. The device according to claim 1, characterized in that The value of the internal resistance of the voltage measurement tool is a typical value of 1 MΩ, 10 MΩ or other set values.

7. A method for monitoring the insulation of an ungrounded system to ground, characterized in that: It includes: Using the internal resistance of the voltage measurement tool as the shunt resistor, measure the voltage between the positive and negative poles of the DC power supply, the voltage of the positive pole of the DC power supply to the ground, and the voltage of the negative pole of the DC power supply to the ground respectively. Based on the three measured voltage values and substituting the known internal resistance of the voltage measurement tool, calculate the insulation resistance of the system to the ground.

8. The method according to claim 7, characterized in that When only one voltage measurement tool is used, the automatic test of the three voltages is realized by switching the switching switch. At this time, the switching switch is at least four.

9. The method according to claim 7, characterized in that: Based on the measured voltages of the positive and negative poles of the DC power supply to the ground, the voltage of the positive pole of the DC power supply to the ground, and the voltage of the negative pole of the DC power supply to the ground, the specific method for calculating the insulation resistance is as follows: Insulation resistance R i Take the smaller value of R1 and R2. If U1>U2, the insulation resistance calculation method is as follows: If U1 < U2, the insulation resistance calculation method is as follows: Among them, R i is the insulation resistance; R1 is the equivalent insulation resistance of the positive pole of the DC power supply to the ground; R2 is the equivalent insulation resistance of the negative pole of the DC power supply to the ground; U0 is the voltage between the positive and negative poles of the DC power supply, U1 is the voltage between the positive pole of the DC power supply to the ground; U2 is the voltage between the negative pole of the DC power supply to the ground; R0 is the internal resistance of the voltage measurement tool; U0, U1, and U2 take absolute values.

10. The method according to claim 7, characterized in that The voltage measurement tool is a conventional multimeter.

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