CN108548983B - Method, device and system for testing capacitance current - Google Patents

Abstract

The invention provides a capacitive current testing method, device and system. The method comprises: electrically connecting the test terminals of the current output module of the capacitive current testing device to the a-phase terminal, b-phase terminal and c-phase terminal of a switch cabinet live indication device respectively. , electrically connect the ground terminal o with the ground terminal of the switch cabinet live indicating device, and electrically connect the current transformers of each phase between the corresponding live indicating sensor capacitance and the switch cabinet live indicating device capacitance; output different frequency current signals; Obtain the inter-frequency voltage and inter-frequency current corresponding to each of the inter-frequency current signals; calculate the ground-to-ground capacitance of each phase of the neutral point ungrounded system; calculate the ground-to-ground capacitance current according to the ground-to-ground capacitance of each phase . The method has the advantages of simple test loop, capable of separately calculating each phase-to-ground capacitance of the power system, no need for power failure, and high safety, and is suitable for capacitance current testing of ungrounded systems.

Description

Method, device and system for testing capacitive current

technical field

The present disclosure relates to the technical field of power systems, and in particular, to a method, device and system for testing capacitive current.

Background technique

In a system that is not grounded at the neutral point, when the line is single-phase grounded, the current flowing through the fault point is the capacitive current generated by the line-to-ground capacitance. Most of the faults of the neutral point ungrounded system are caused by the excessive capacitive current when the line is single-phase grounded, and the arc is not easy to self-extinguish. my country's power system stipulates that when the capacitance current of 10kV and 35kV systems is greater than 30A and 10A, an arc suppression coil should be installed to compensate the capacitor current. In order to determine the compensation capacity of the arc suppression coil, a capacitor current test should be carried out. In addition, in order to verify whether ferromagnetic resonance occurs between the electromagnetic voltage transformer PT of the non-effectively grounded system and the stray capacitance of the line, the system capacitance current must also be measured.

Commonly used capacitance current test methods include direct measurement method and indirect measurement method. The direct measurement method directly measures the single-phase grounding of a certain phase line; the indirect measurement methods mainly include offset capacitance method, neutral point added capacitance method and different frequency method. . However, the direct method to measure the capacitance current should be in direct contact with the high voltage during the test, and the safety of the power grid and human life is at greater risk. The current indirect measurement methods, such as the neutral point plus capacitance method, have safety risks when there is no neutral point in some systems or the neutral point offset voltage is small, and a single-phase ground fault occurs during the measurement process; the different frequency method is usually used in electromagnetic fields. When measuring the open delta winding of the type voltage transformer, the harmonic eliminator should be removed or short-circuited, which requires the electromagnetic voltage transformer to be powered off, the test work becomes complicated, and even brings the risk of ferromagnetic resonance to the system. Therefore, it is necessary to find a safe and easy test for capacitive current testing.

SUMMARY OF THE INVENTION

The embodiments of the present invention provide a method, device and system for testing capacitive current, so as to solve the problems of complicated operation and poor safety in the prior art.

The invention provides a capacitive current testing device, comprising a power supply module, a high-frequency power supply module, a current output module, a testing module, a capacitance-current calculation module and a current transformer, and one end of the high-frequency power supply module is electrically connected to the power supply module, the other end is electrically connected to the current output module and the test module respectively, and the test module is also electrically connected to the capacitance current calculation module and the current transformer of each phase.

Preferably, the current output module includes a test terminal m and a ground terminal o, the test terminal m is electrically connected to the a-phase terminal, b-phase terminal and c-phase terminal of the switch cabinet live indication device, respectively, and the ground terminal o is electrically connected to Connect to the ground terminal of the switch cabinet energized indicating device.

Preferably, the device further includes a display module, and the display module is electrically connected to the other end of the capacitance current calculation module.

The present invention also provides a capacitive current testing system, which includes the device described in any one of the above, and also includes a three-phase power supply, a live indicating sensor, and a switch cabinet live indicating device, the a-phase end of the switch cabinet live indicating device , b-phase terminal and c-phase terminal are respectively electrically connected with _A -phase source E1, B-phase source _E2 and C-phase source E3 in the _three -phase power supply through the live indicating sensor. During the test, the current output module The test terminal m is respectively electrically connected to the a-phase end, b-phase end and c-phase end of the switch cabinet live indication device, and the ground terminal o of the current output module is electrically connected to the ground end of the switch cabinet live indication device. The current mutual inductance of each phase The device is electrically connected between the capacitor of the corresponding live indicating sensor and the capacitor of the switch cabinet live display device.

The present invention also provides a method for testing capacitive current, comprising the following steps:

Connect the test terminal m of the current output module of the capacitive current test device to the a-phase terminal, b-phase terminal and c-phase terminal of the switch cabinet live indication device respectively, and connect the ground terminal o of the current output module of the capacitive current test device to the switch cabinet live. The ground terminal of the indicating device is electrically connected, and the current transformer of each phase is electrically connected between the corresponding live indicating sensor capacitance and the switch cabinet live display device capacitance;

Control the high-frequency voltage module of the capacitive current test device to output a preset different-frequency current signal;

The test module obtains each corresponding inter-frequency voltage ua , _ub , _uc and each corresponding inter-frequency current i _a , _ib , _ic under the inter-frequency current i ₀ of the current output _module ;

According to a-phase different-frequency current ia, _b -phase different-frequency current ib, _c -phase different-frequency current ic, _{a-phase different-frequency voltage u a , b} -phase different-frequency voltage ub, _c -phase different-frequency voltage uc and charging Indicate the capacitance of the sensor, and calculate the capacitance to ground of each phase of the neutral point ungrounded system;

According to the ground capacitance of each phase, the ground capacitance current is calculated.

Preferably, the different frequency current signal is a certain current value i ₀ between 0.1 mA and 100 mA, and the frequency of the different frequency current signal is a certain frequency value between 0.2 k and 1000 kHz.

Preferably, the calculation formula of the capacitance to ground of each phase is:

Among them, C _a , C _b , and C _c are the relative-to-ground capacitance of A, the relative-to-ground capacitance of B, and the relative-to-ground capacitance of C in the neutral point ungrounded system, respectively; C ₁₁ , C ₁₂ , and C ₁₃ are respectively corresponding to the switch cabinet live indication sensor A-phase capacitance, B-phase capacitance and C-phase capacitance; ω ₁ is the angular frequency of the input different-frequency current signal.

Preferably, the calculation formula of the capacitance current to ground is:

为被测系统相电压，I_c为对地电容电流。Wherein, C ₂₁ , C ₂₂ , and C ₂₃ are the A-phase capacitance, B-phase capacitance, and C-phase capacitance corresponding to the charging indicator device, respectively, and ω ₂ is the angular frequency of the system under test;

is the phase voltage of the system under test, and I _c is the capacitance current to the ground.

The beneficial effects of this application are as follows:

The invention provides a capacitive current testing method, device and system. The device includes a power supply module, a high-frequency power supply module, a current output module, a testing module, a capacitance-current calculation module and a current transformer. One end of the high-frequency power supply module is electrically The power module is connected to the power supply module, and the other end is electrically connected to the current output module and the test module respectively, and the test module is also electrically connected to the capacitance current calculation module and the current transformer of each phase. Among them, the power supply module is used to supply power to other modules of the device; the high-frequency power supply module is used to generate different-frequency current signals; the current output module is used to output the different-frequency current signals to the voltage divider capacitor of the charged indicator device; the measurement module is used to test The voltage of the current output module and the total loop current; the capacitance current calculation module is used to calculate the capacitance current according to the preset formula, and the current transformer is used to test the different frequency current of each phase. The invention cleverly utilizes the capacitances (C ₁₁ , C ₁₂ , C ₁₃ ) of the commonly used switch cabinet live indicating sensors and the capacitances (C ₂₁ , C ₂₂ , C ₂₃ ) of the live indicating devices, and by applying different-frequency current signals, measures The voltage of the capacitors (C ₂₁ , C ₂₂ , C ₂₃ ) of the live indicating device and the different-frequency current passing through the live indicating sensor of the switchgear can be used to obtain the capacitive current of the system under test to the ground. It has the advantages of relative ground capacitance, no power failure, and high safety. It is suitable for capacitive current testing of ungrounded systems.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description serve to explain the principles of the invention.

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. In other words, on the premise of no creative labor, other drawings can also be obtained from these drawings.

FIG. 1 is an electrical wiring diagram of a capacitive current test system based on a switch cabinet live indication device provided by an embodiment of the application;

FIG. 2 is an electrical equivalent circuit diagram of A phase-to-ground capacitance measurement provided by an embodiment of the present application;

FIG. 3 is an electrical equivalent circuit diagram of a B phase-to-ground capacitance measurement provided by an embodiment of the present application;

FIG. 4 is an electrical equivalent circuit diagram of a C phase-to-ground capacitance measurement provided by an embodiment of the present application;

5 is a schematic structural diagram of a capacitance current testing device provided by an embodiment of the present application;

FIG. 6 is a method flowchart of a capacitive current testing method provided by an embodiment of the present application.

Detailed ways

In order to make those skilled in the art better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described The embodiments are only some of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Please refer to FIGS. 1-4 , which show the electrical wiring diagram, the electrical equivalent circuit diagram of A relative to ground capacitance measurement, and the B relative to ground capacitance of a capacitive current testing system based on a switch cabinet live indicating device provided by the embodiments of the present application, respectively. Measurement electrical equivalent circuit diagram and C phase-to-ground capacitance measurement electrical equivalent circuit diagram. It can be seen from Figure 1-4 that the test system includes a neutral point ungrounded system and a corresponding capacitive current test device, and the neutral point ungrounded system is the system under test of the capacitive current test device. The three-phase power sources ( _A -phase source E1, B-phase source _E2 , and C _- phase source E3) of the system under test are respectively electrically connected with live indicating sensors, and the live indicating sensors are electrically connected with the switch cabinet live indicating device. The switchgear live indicator device is usually used to monitor whether the switchgear is electrified. If it is electrified, a warning signal will be issued or the switchgear door will be electrically locked to remind the staff that the switchgear is electrified and the door cannot be opened.

The electrification indicating sensor includes A-phase capacitance C ₁₁ , B-phase capacitance C ₁₂ and C-phase capacitance C ₁₃ corresponding to each, respectively, and the switch cabinet electrification indicating device includes A-phase capacitance C ₂₁ , B-phase capacitance corresponding to each C ₂₂ and C-phase capacitor C ₂₃ , capacitor C ₁₁ is electrically connected to capacitor C ₂₁ , capacitor C ₁₂ is electrically connected to capacitor C ₂₂ , and capacitor C ₁₃ is electrically connected to capacitor C ₂₃ . Capacitor C ₂₁ , capacitor C ₂₂ and capacitor C ₂₃ cooperate with C ₁₁ , C ₁₂ , and C ₁₃ to divide the voltage to ensure the voltage on the charged indicator light.

The capacitive current test device provided by the present application includes a test terminal m and a ground terminal o, the test terminal m is electrically connected to the a-phase terminal, b-phase terminal and c-phase terminal of the switch cabinet live indication device, respectively, and the ground terminal o is connected to The ground terminal of the switch cabinet live indicating device is electrically connected, and the test terminal m is used to inject different frequency current signals and three-phase current tests into the system.

Please refer to FIG. 5 , which is a schematic structural diagram of a capacitance current testing apparatus provided by an embodiment of the present application. As can be seen from Figure 5, the capacitive current testing device includes a power supply module 1, a high-frequency power supply module 2, a current output module 3, a testing module 4, a capacitance-current calculation module 5 and a current transformer 6, and one end of the high-frequency power supply module 2 The power supply module 1 is electrically connected, and the other end is electrically connected to the current output module 3 and the test module 4 respectively. The test module 4 is also electrically connected to the capacitance current calculation module 5 and the current transformer 6 of each phase. Among them, the power supply module 1 is a power supply module, which is used to supply power to other modules of the device, and the power supply module 1 can be a component with a power supply function such as a battery; the high-frequency power supply module 2 is used to generate different-frequency current signals, such as frequency converters, etc.; The current output module 3 is used to output the different frequency current signal to the voltage dividing capacitor of the charged indicating device. The current output module 3 includes a test terminal m and a ground terminal o, which are used to convert the different frequency current of a certain frequency between 0.2k and 1000kHz. The signals are injected into the voltage dividing capacitors (C ₂₁ , C ₂₂ , C ₂₃ ) of the A-phase, B-phase and C-phase live indicating devices respectively; the measurement module 4 is used to test the voltage of the current output module 3, the total loop current and the different frequency of each phase The current, that is, each corresponding inter-frequency voltage u _a , _ub , _uc and each corresponding inter-frequency current _ia , _ib , ic under _{i 0} under the inter-frequency current, the measurement module 4 may have A tester with voltage and current detection functions; the capacitance current calculation module 5 is used to calculate the capacitance current according to preset programs and formulas, and the capacitance current calculation module 5 can be a microprocessor with calculation processing functions such as MCU, and the current transformer 6 is used for To test the different frequency current of each phase.

In addition, in other embodiments of the present application, the capacitive current testing device may further include a display module 7, and the display module 7 is electrically connected to the other end of the capacitive current calculation module 5 for displaying the capacitive current value calculated by the capacitive current calculation module 5 , in this embodiment, the display module 7 may be a display with a display function.

Based on the above-mentioned capacitive current testing device, the present application also provides a capacitive current testing method. Please refer to FIG. 6 , which shows a method flowchart of a capacitive current testing method provided by an embodiment of the present application. As can be seen from Figure 6, this includes the following steps:

Step S100: Connect the test terminal m of the current output module of the capacitive current test device to the a-phase terminal, b-phase terminal and c-phase terminal of the switch cabinet live indicating device respectively, and connect the ground terminal o of the current output module of the capacitive current test device to the ground terminal o of the current output module of the capacitive current test device. The ground terminal of the switch cabinet live indication device is electrically connected, and the current transformer of each phase is electrically connected between the corresponding live indicator sensor capacitance and the switch cabinet live display device capacitance.

Step S200 : controlling the high-frequency voltage module of the capacitive current testing device to output a preset inter-frequency current signal i ₀ , the inter-frequency current signal is a certain current value i ₀ between 0.1 mA and 100 mA, and the inter-frequency current The frequency of the signal is a certain frequency value between 0.2k and 1000kHz.

Step S300 : the test module acquires each corresponding inter-frequency voltage ua , _ub , _uc and each corresponding inter-frequency current _{i a , ib} under the inter-frequency current i ₀ of the inter-frequency current signal , _ic . Among them, u _a is the inter-frequency voltage corresponding to a, u _b is the inter-frequency voltage corresponding to b, and u _c is the inter-frequency voltage corresponding to c; i _a is the inter-frequency current corresponding to a, and i _b is b The corresponding different frequency current, ic is the corresponding different frequency current of _c .

Step S400: According to a-phase different-frequency current i _a , _b -phase different-frequency current ib , _c -phase different-frequency current ic , a-phase different-frequency voltage u _a , _b -phase different-frequency voltage ub , and c-phase different-frequency voltage u _c and the capacitance of the charged indicating sensor, calculate the ground capacitance of each phase of the neutral point ungrounded system. The specific calculation formula is:

Among them, C _a , C _b , and C _c are the relative-to-ground capacitance of A, the relative-to-ground capacitance of B, and the relative-to-ground capacitance of C in the neutral point ungrounded system, respectively; C ₁₁ , C ₁₂ , and C ₁₃ are respectively corresponding to the switch cabinet live indication sensor A-phase capacitance, B-phase capacitance and C-phase capacitance; ω ₁ is the angular frequency of the input different-frequency current signal. In the above formula 1, C ₁₁ , C ₁₂ , C ₁₃ and ω ₁ are all known quantities. Therefore, according to the electrical equivalent circuit diagram provided in Figure 2-4, the calculation formula 1 can be obtained. The capacitances C _a , C _b , and C _c of each phase of the ungrounded system.

Step S500: According to the ground capacitance of each phase, calculate the ground capacitance current I _c , and the specific calculation formula is:

为被测系统相电压，I_c为对地电容电流。Among them, ω ₂ is the angular frequency of the system under test, usually a fixed value, 50Hz;

is the phase voltage of the system under test, and I _c is the capacitance current to the ground.

The capacitive current testing device and the testing method based on the capacitive current testing device provided by the present invention have the advantages of simple test loop, ability to separately calculate each phase-to-ground capacitance of the power system, no need for power failure, and high safety, and are suitable for capacitive current testing of ungrounded systems .

Each embodiment in this specification is described in a progressive manner, and the same and similar parts between the various embodiments may be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the apparatus or system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and reference may be made to some descriptions of the method embodiments for related parts. The apparatus and system embodiments described above are only schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in One place, or it can be distributed over multiple network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution in this embodiment. Those of ordinary skill in the art can understand and implement it without creative effort.

The above are only specific embodiments of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as It is the protection scope of the present invention.

Claims (7)

1. a test device for capacitive current, characterized in that it comprises a power supply module (1), a high frequency power supply module (2), a current output module (3), a test module (4), a capacitive current calculation module (5) and a current transformer (6), one end of the high-frequency power supply module (2) is electrically connected to the power supply module (1), and the other end is electrically connected to the current output module (3) and the test module (4), respectively, The test module (4) is also electrically connected to the capacitive current calculation module (5) and the current transformer (6) of each phase; wherein: The power supply module (1) is used for supplying power to the high-frequency power supply module (2), the current output module (3), the test module (4) and the capacitance current calculation module (5); The high-frequency power module (2) is used to generate an inter-frequency current signal; The current output module (3) includes a test terminal m and a ground terminal o, the test terminal m is respectively electrically connected to the a-phase end, b-phase end and c-phase end of the switch cabinet live indication device, and the ground terminal o is electrically connected. Connect to the ground terminal of the switch cabinet live indicating device; The test module (4) is used for each corresponding different frequency voltage and each corresponding different frequency current under the different frequency current; The capacitance current calculation module (5) is used to calculate the capacitance current according to a preset program and formula. 2. The device according to claim 1, characterized in that, the device further comprises a display module (7), and the display module (7) is electrically connected to the other end of the capacitive current calculation module (5). 3. A test system for capacitive current, characterized in that, comprising the device according to any one of claims 1-2, further comprising a three-phase power supply, a live indicating sensor and a switch cabinet live indicating device, the switch cabinet being charged The a-phase end, b-phase end and c-phase end of the indicating device are respectively electrically connected to the _A -phase source E1, B-phase source _E2 and C-phase source E3 in the _three -phase power supply through the live indicating sensor, and the test is carried out. At this time, the test terminal m of the current output module (3) is respectively electrically connected to the a-phase terminal, b-phase terminal and c-phase terminal of the switch cabinet live indication device, and the ground terminal o of the current output module (3) is electrically connected to the switch cabinet live indicator device The grounding terminal of each phase is electrically connected, and the current transformer (6) of each phase is electrically connected between the corresponding charge indicating sensor capacitor and the switch cabinet charge display device capacitor. 4. a testing method of capacitive current, is characterized in that, comprises the steps: Connect the test terminal m of the current output module of the capacitive current test device to the a-phase terminal, b-phase terminal and c-phase terminal of the switch cabinet live indication device respectively, and connect the ground terminal o of the current output module of the capacitive current test device to the switch cabinet live. The ground terminal of the indicating device is electrically connected, and the current transformer of each phase is electrically connected between the corresponding live indicating sensor capacitance and the switch cabinet live display device capacitance; Control the high-frequency voltage module of the capacitive current test device to output a preset different-frequency current signal; The test module obtains each corresponding inter-frequency voltage u _a , _ub , _uc and each corresponding inter-frequency current i _a , _ib , _ic under the inter-frequency current i ₀ of the switch cabinet live display device; According to a-phase different-frequency current ia, _b -phase different-frequency current ib, _c -phase different-frequency current ic, _{a-phase different-frequency voltage u a , b} -phase different-frequency voltage ub, _c -phase different-frequency voltage uc and charging Indicate the capacitance of the sensor, and calculate the capacitance to ground of each phase of the neutral point ungrounded system; According to the ground capacitance of each phase, the ground capacitance current is calculated. 5 . The method according to claim 4 , wherein the inter-frequency current signal is a certain current value i ₀ between 0.1 mA and 100 mA, and the frequency of the inter-frequency current signal is between 0.2 k and 1000 kHz. 6 . a frequency value in between. 6. The method according to claim 4, wherein the calculation formula of the capacitance to ground of each phase is: Among them, C _a , C _b , and C _c are the relative-to-ground capacitance of A, the relative-to-ground capacitance of B, and the relative-to-ground capacitance of C in the neutral point ungrounded system, respectively; C ₁₁ , C ₁₂ , and C ₁₃ are respectively corresponding to the switch cabinet live indication sensor A-phase capacitance, B-phase capacitance and C-phase capacitance; ω ₁ is the angular frequency of the input different-frequency current signal. 7. The method according to claim 6, wherein the calculation formula of the capacitance current to ground is:

Wherein, C ₂₁ , C ₂₂ , and C ₂₃ are the A-phase capacitance, B-phase capacitance, and C-phase capacitance corresponding to the charging indicator device, respectively, and ω ₂ is the angular frequency of the system under test;

is the phase voltage of the system under test, and I _c is the capacitance current to the ground.

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