CN114184981B - Low-voltage electric leakage positioning equipment and off-line electric leakage assessment method - Google Patents

Abstract

The present invention proposes a low-voltage leakage locating device and an offline leakage assessment method, which are used to accurately select leakage fault lines in the Taiwan area and locate the leakage fault location. When the line under test is in a power outage state, the host of the low-voltage leakage locator passes through the A specific voltage is applied to the four-phase lines A, B, C, and N in the tested area, and the current is injected into the four-phase lines through the current sampling circuit for measurement, and then the resistance value of the tested line is calculated, and then each phase is measured according to the complex leakage model. The resistance value to the ground is finally calculated according to the resistance value of A, B, C and N to the ground. The leakage current and daily average leakage amount of each phase line in the tested station area are calculated, and the leakage of the tested station area is evaluated. When any phase When the resistance to ground is less than the threshold, it is determined that there is a leakage fault in the station area; this invention can standardize the configuration of leakage protectors in rural power distribution stations, improve the installation rate and commissioning rate of protection in the station area, and give full play to the effectiveness of leakage protectors , to ensure the safety of people’s lives and property to the greatest extent.

Description

Low-voltage leakage positioning equipment and offline leakage assessment method

Technical field

The invention relates to the technical field of power grid operation and maintenance, in particular to low-voltage leakage positioning equipment and offline leakage assessment methods.

Background technique

Leakage in rural distribution network lines is currently a pain point and difficulty that plagues the safe and economical operation of low-voltage rural distribution networks. For a long time, there has been no effective technical means to accurately locate leakage faults, which has brought the following three problems to power grid enterprises: First, power supply reliability Reduce, low-voltage line leakage occurs from time to time, which can easily cause the main leakage breaker in the Taiwan area to trip, which greatly affects the normal production and life of customers. Secondly, it is difficult to guarantee the safety of electricity. In order to improve the reliability of power supply, some Taiwan areas have withdrawn leakage protection. When a leakage fault occurs, the leakage protection cannot operate, causing fires or electric shock casualties. Third, the economic benefits of the enterprise are damaged, and intermittent leakage occurs from time to time, making it difficult to detect and deal with it in time, resulting in loss of profits for the power grid enterprise. drain.

Contents of the invention

The present invention proposes low-voltage leakage positioning equipment and offline leakage assessment methods, which can standardize the configuration of leakage protectors in rural distribution stations, improve the installation rate and operation rate of protection in station areas, maximize the effectiveness of leakage protectors, and maximize the protection of the people. Safety of life and property.

The present invention adopts the following technical solutions.

The offline leakage assessment method of low-voltage leakage is used to accurately select leakage fault lines in the Taiwan area and accurately locate the location of leakage faults. The offline leakage assessment method is based on the low-voltage leakage locator when the line under test is in a power outage state. The host applies a specific voltage to the four-phase lines A, B, C, and N in the tested station area, and injects current into the four-phase lines through the current sampling circuit for measurement, and then calculates the resistance value of the tested line, and then measures it according to the complex leakage model Obtain the resistance value of each phase to the ground, and finally calculate the leakage current and daily average leakage amount of each phase line in the tested station area based on the resistance values of A, B, C, and N to the ground, and perform a leakage assessment on the tested station area. When the resistance value of any phase to ground is less than the threshold value, it is determined that there is a leakage fault in the station area.

In the complex leakage model, R _A0 , R _B0 , R _C0 , and R _N0 are the insulation resistance values of phase A, phase B, phase C, and phase N that need to be measured during offline leakage evaluation. If the insulation resistance value is infinite, the evaluation No leakage occurs in this phase. If the insulation resistance value is a specific value that can be measured within the range, it is estimated that leakage occurs in this phase. The following formula exists in the model;

R _AN ＝R _AN0 //(R _A0 +R _N0 //(R _BN0 +R _B0 )//(R _CN0 +R _C0 )) Formula 9;

R _BN =R _BN0 //(R _B0 +R _N0 //(R _AN0 +R _A0 )//(R _CN0 +R _C0 )) Formula 10;

R _CN =R _CN0 //(R _C0 +R _N0 //(R _AN0 +R _A0 )//(R _BN0 +R _B0 )) Formula 11;

R _AG ＝R _A0 //[R _AN0 +(R _BN0 +R _B0 )//(R _CN0 +R _C0 )//R _N0 ] Formula 12;

R _BG =R _B0 //[R _BN0 +(R _AN0 +R _A0 )//(R _CN0 +R _C0 )//R _N0 ] Formula 13;

R _CG =R _C0 //[R _CN0 +(R _AN0 +R _A0 )//(R _BN0 +R _B0 )//R _N0 ] Formula 14;

R _NG =R _N0 //(R _AN0 +R _A0 )//(R _BN0 +R _B0 )//(R _CN0 +R _C0 ) Formula 15;

In Formula 9 to Formula 15, when the resistance R _AN between phase A and phase N, the resistance between phase B and phase N R _BN , the resistance between phase C and phase N R _CN , the resistance between phase A and phase G R _AG , the resistance between phase B and phase G The resistance R _BG , the resistance between C phase and G phase R _CG , and the resistance between N phase and G phase R _NG are known quantities measured by the host of the low-voltage leakage locator. Then R _A0 and R can be calculated according to formulas 9 to 15. _B0 , R _C0 , R _N0 , R _AN0 , R _BN0 , R _CN0 values.

The offline leakage evaluation method is to use the host of the low-voltage leakage locator to apply a specific voltage to the A, B, C, and N four-phase lines in the tested area when the line under test is in a power outage state. The current sampling circuit injects current measurement into the four-phase circuit;

The hardware used by the host computer of the low-voltage leakage locator for offline leakage evaluation includes an MCU, a current sampling circuit, a voltage dividing circuit and a voltage following circuit;

The current sampling circuit includes a voltage source, a current sampling resistor and IC1, and T is the resistance being measured;

The voltage dividing circuit is used to make the full-scale voltage range output by the current sampling circuit meet the ADC acquisition range of the MCU.

Low-voltage leakage locating equipment. The low-voltage leakage locating equipment includes a low-voltage leakage locator host and a low-voltage leakage locator slave. The hardware part of the low-voltage leakage locator host includes a battery charging circuit, a battery, a DC\DC circuit, a display, a button, and a bee. Beeper, MCU, shift circuit, integrating circuit, amplifier circuit, full-wave rectification circuit, filter circuit, MCU, signal conditioning circuit, current limiting resistor, analog channel switch, current sampling circuit, voltage dividing circuit, voltage following circuit.

The host hardware part of the low-voltage leakage locator also includes a Rogowski coil used for online leakage evaluation method. The hardware used for online leakage evaluation also includes a shift circuit, an integration circuit, an amplification circuit, a full-wave rectification circuit, a low-pass filter circuit and MCU;

The online leakage evaluation method uses a low-voltage leakage positioning device to measure the current vector sum of the A, B, C, and N phases of the tested station area through the Rogowski coil in the online working state. If the Rogowski coil measures the current vector sum of the tested station area, it is not If zero, the evaluation result is that there is leakage in the table area. If the current vector sum of the measured table area measured by the Rogowski coil is zero, the evaluation result is that there is no leakage in the table area;

When measuring the vector sum of the A, B, C, and N phase currents in the tested area, the Rogowski coil outputs a differential signal of the vector sum of the A, B, C, and N phase currents. This output signal is linearly related to the rate of change of the measured current. ;

The output signal of the Rogowski coil enters the integrating circuit according to the proportion of different weights through the shift circuit. The integrating circuit integrates and restores the differential signal of the Rogowski coil output current vector sum, and integrates the voltage signal output by the Rogowski coil to obtain an accurate representation of the object. Measure the AC voltage signal of the waveform of the current signal;

The amplifier circuit amplifies the signal output by the integrating circuit; the full-wave rectifier circuit is connected to the amplifier circuit to perform full-wave rectification on the signal output by the amplifier circuit; the low-pass filter circuit is connected to the full-wave rectifier circuit to output the full-wave rectifier circuit The signal is low-pass filtered and the effective value of the measured current is output.

Low-voltage leakage locating equipment is used to locate leakage currents with loop characteristics. When locating leakage, the low-voltage leakage locator host is used to inject characteristic signals into the fault line. Due to the loop characteristics of the leakage current, the injected characteristic signals only exist in In the circuit to the ground, that is, there is an injected characteristic signal on the front side of the fault point but not on the rear side of the fault point. Then, the location of the leakage fault is determined by judging whether there is an injected characteristic signal in the line under test. The specific method is: in the low-voltage leakage With the use of the locator slave machine, the location of the leakage fault point can be accurately located. First, rough segmentation detection is performed, and then the point is accurately determined.

In the host computer of the low-voltage leakage locator, the hardware part used for leakage positioning includes MCU, signal conditioning circuit, current limiting resistor, and analog channel switch;

When locating leakage on the power outage line in the Taiwan area, the host of the low-voltage leakage locator injects a characteristic signal into the faulty line. The characteristic signal includes a voltage signal for leakage assessment and a pulse signal for leakage positioning. The low-voltage leakage positioning instrument The magnetic core coil sensor of the instrument slave machine receives the characteristic signal and outputs an induction signal. The induced voltage of the induction signal is proportional to the rate of change of the voltage of the characteristic signal injected into the host machine of the low-voltage leakage locator.

The low-voltage leakage locator host uses a pulse signal as a characteristic signal injected into the fault line; the pulse signal is generated by a half-bridge circuit in the low-voltage leakage locator host.

In the leakage locating process, the host of the low-voltage leakage locator generates a coded frequency signal and injects it into the fault line according to the master-slave agreement. Only one phase of the fault line is signal-injected with the characteristic coded signal at a time, and then the characteristic coded signal is injected into the leakage fault line. Along the way, a low-voltage leakage locator is used on the slave machine to decode characteristic signals in a non-contact manner. The location of the leakage fault point is first roughly segmented, and then the leakage fault point is accurately located.

The software of the low-voltage leakage locator host is based on the Linux+QT architecture. When executing a long-time leakage assessment operation, a separate thread operation is used to avoid affecting the execution of other software modules;

When generating the encoded frequency signal for signal injection, the injection signals of A-phase, B-phase, C-phase, and N-phase use the same encoding method, and the signal content of the injection signals of A-phase, B-phase, C-phase, and N-phase is different. ;

The low-voltage leakage locator slave machine includes a magnetic core coil sensor, a low-voltage leakage locator slave machine PCB and a battery;

After the low-voltage leakage locator host injects a characteristic signal into the fault line, the characteristic signal generates a magnetic field around the fault line. Assume that the voltage of the characteristic signal injected by the low-voltage leakage locator host into the leakage fault line is V, the frequency is F, and the ground resistance of the fault line is R, If the current I flows through the fault line, then according to Biot-Savart's law, the magnetic induction intensity B at a distance d from the fault line can be obtained as:

Among them, μ ₀ is the vacuum magnetic permeability, μ ₀ =4π×10 ^-7 Tesla·meter/ampere;

The slave machine of the low-voltage leakage locator receives the magnetic field of the characteristic signal through the magnetic core coil sensor and interprets the special signal. According to Faraday's law of electromagnetic induction, the magnitude of the induced electromotive force ξ output by the magnetic core coil sensor is related to the change rate of the magnetic flux passing through the loop. Directly proportional to

The slave machine of the low-voltage leakage locator receives the output signal of the magnetic core coil sensor and demodulates it, and then identifies whether the demodulated signal is a characteristic signal injected by the host machine of the low-voltage leakage locator.

The invention can realize accurate line selection of leakage fault lines and precise positioning of leakage fault locations, and can better implement DL/T736-2010 "Rural Power Grid Leakage Protector Installation and Operation Regulations" and "State Grid Corporation of China Rural Low-voltage Power Grid Leakage Protection "Principles of Device Configuration" (State Grid Nong'an [2012] No. 39), which can standardize the configuration of leakage protectors in rural distribution stations, improve the installation rate and commissioning rate of protection in station areas, maximize the effectiveness of leakage protectors, and maximize protection The safety of people's lives and property has important social significance and economic benefits.

This invention innovatively proposes to use the characteristics of low-voltage leakage fault lines to inject characteristic signals from the low-voltage leakage locator host into the line to be measured. If the line where the characteristic signal is injected is a leakage fault line, there will be low-voltage leakage locator host injection in the fault circuit. characteristic signal, thereby realizing the function of line selection for leakage faults. The low-voltage leakage locator host injects characteristic coding signals into the leakage fault line, and the low-voltage leakage locator slave machine is used along the leakage fault line to decode the characteristic signals in a non-contact manner. Before the fault point, the injected feature coding signal continues to exist, and after the fault point, the injected feature coding signal disappears. The fault location can be quickly determined by roughly segmenting it first and then pinpointing it accurately.

Description of the drawings

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments:

Figure 1 is a schematic diagram of the low-voltage leakage positioning principle of the present invention;

Figure 2 is another schematic diagram of the low-voltage leakage positioning principle of the present invention;

Figure 3 is a schematic diagram of the hardware principle of the low-voltage leakage locator host;

Figure 4 is a schematic diagram of a complex leakage model used for offline leakage assessment;

Figure 5 is a schematic diagram of the A, B, C and N phases of the circuit under test being connected to the Rogowski coil during online leakage assessment;

Figure 6 is a schematic diagram of the leakage positioning operation of the present invention.

Detailed ways

As shown in the figure, the offline leakage assessment method of low-voltage leakage is used to accurately select leakage fault lines in the Taiwan area and accurately locate the location of leakage faults. The offline leakage assessment method is to conduct a power outage on the line under test. The host of the low-voltage leakage locator applies a specific voltage to the four-phase lines A, B, C, and N in the test area, and injects current into the four-phase lines through the current sampling circuit for measurement, and then calculates the resistance value of the line under test, and then According to the complex leakage model, the resistance value of each phase to the ground is obtained. Finally, the leakage current and daily average leakage amount of each phase line in the tested station area are calculated based on the resistance values of A, B, C, and N to the ground. Carry out leakage assessment, and when the resistance value of any phase to ground is less than the threshold, it is determined that there is a leakage fault in the station area.

In the complex leakage model, R _A0 , R _B0 , R _C0 , and R _N0 are the insulation resistance values of phase A, phase B, phase C, and phase N that need to be measured during offline leakage evaluation. If the insulation resistance value is infinite, the evaluation No leakage occurs in this phase. If the insulation resistance value is a specific value that can be measured within the range, it is estimated that leakage occurs in this phase. The following formula exists in the model;

R _AN ＝R _AN0 //(R _A0 +R _N0 //(R _BN0 +R _B0 )//(R _CN0 +R _C0 )) Formula 9;

R _BN =R _BN0 //(R _B0 +R _N0 //(R _AN0 +R _A0 )//(R _CN0 +R _C0 )) Formula 10;

R _CN =R _CN0 //(R _C0 +R _N0 //(R _AN0 +R _A0 )//(R _BN0 +R _B0 )) Formula 11;

R _AG ＝R _A0 //[R _AN0 +(R _BN0 +R _B0 )//(R _CN0 +R _C0 )//R _N0 ] Formula 12;

R _BG =R _B0 //[R _BN0 +(R _AN0 +R _A0 )//(R _CN0 +R _C0 )//R _N0 ] Formula 13;

R _CG =R _C0 //[R _CN0 +(R _AN0 +R _A0 )//(R _BN0 +R _B0 )//R _N0 ] Formula 14;

R _NG =R _N0 //(R _AN0 +R _A0 )//(R _BN0 +R _B0 )//(R _CN0 +R _C0 ) Formula 15;

In Formula 9 to Formula 15, when the resistance R _AN between phase A and phase N, the resistance between phase B and phase N R _BN , the resistance between phase C and phase N R _CN , the resistance between phase A and phase G R _AG , the resistance between phase B and phase G The resistance R _BG , the resistance between C phase and G phase R _CG , and the resistance between N phase and G phase R _NG are known quantities measured by the host of the low-voltage leakage locator. Then R _A0 and R can be calculated according to formulas 9 to 15. _B0 , R _C0 , R _N0 , R _AN0 , R _BN0 , R _CN0 values.

The offline leakage evaluation method is to use the host of the low-voltage leakage locator to apply a specific voltage to the A, B, C, and N four-phase lines in the tested area when the line under test is in a power outage state. The current sampling circuit injects current measurement into the four-phase circuit;

The hardware used by the host computer of the low-voltage leakage locator for offline leakage evaluation includes an MCU, a current sampling circuit, a voltage dividing circuit and a voltage following circuit;

The current sampling circuit includes a voltage source, a current sampling resistor and IC1, and T is the resistance being measured;

The voltage dividing circuit is used to make the full-scale voltage range output by the current sampling circuit meet the ADC acquisition range of the MCU.

Low-voltage leakage locating equipment. The low-voltage leakage locating equipment includes a low-voltage leakage locator host and a low-voltage leakage locator slave. The hardware part of the low-voltage leakage locator host includes a battery charging circuit, a battery, a DC\DC circuit, a display, a button, and a bee. Beeper, MCU, shift circuit, integrating circuit, amplifier circuit, full-wave rectification circuit, filter circuit, MCU, signal conditioning circuit, current limiting resistor, analog channel switch, current sampling circuit, voltage dividing circuit, voltage following circuit.

The host hardware part of the low-voltage leakage locator also includes a Rogowski coil used for online leakage evaluation method. The hardware used for online leakage evaluation also includes a shift circuit, an integration circuit, an amplification circuit, a full-wave rectification circuit, a low-pass filter circuit and MCU;

The online leakage evaluation method uses a low-voltage leakage positioning device to measure the current vector sum of the A, B, C, and N phases of the tested station area through the Rogowski coil in the online working state. If the Rogowski coil measures the current vector sum of the tested station area, it is not If zero, the evaluation result is that there is leakage in the table area. If the current vector sum of the measured table area measured by the Rogowski coil is zero, the evaluation result is that there is no leakage in the table area;

When measuring the vector sum of the A, B, C, and N phase currents in the tested area, the Rogowski coil outputs a differential signal of the vector sum of the A, B, C, and N phase currents. This output signal is linearly related to the rate of change of the measured current. ;

The output signal of the Rogowski coil enters the integrating circuit according to the proportion of different weights through the shift circuit. The integrating circuit integrates and restores the differential signal of the Rogowski coil output current vector sum, and integrates the voltage signal output by the Rogowski coil to obtain an accurate representation of the object. Measure the AC voltage signal of the waveform of the current signal;

The amplifier circuit amplifies the signal output by the integrating circuit; the full-wave rectifier circuit is connected to the amplifier circuit to perform full-wave rectification on the signal output by the amplifier circuit; the low-pass filter circuit is connected to the full-wave rectifier circuit to output the full-wave rectifier circuit The signal is low-pass filtered and the effective value of the measured current is output.

Low-voltage leakage locating equipment is used to locate leakage currents with loop characteristics. When locating leakage, the low-voltage leakage locator host is used to inject characteristic signals into the fault line. Due to the loop characteristics of the leakage current, the injected characteristic signals only exist in In the circuit to the ground, that is, there is an injected characteristic signal on the front side of the fault point but not on the rear side of the fault point. Then, the location of the leakage fault is determined by judging whether there is an injected characteristic signal in the line under test. The specific method is: in the low-voltage leakage With the use of the locator slave machine, the location of the leakage fault point can be accurately located. First, rough segmentation detection is performed, and then the point is accurately determined.

In the host computer of the low-voltage leakage locator, the hardware part used for leakage positioning includes MCU, signal conditioning circuit, current limiting resistor, and analog channel switch;

When locating leakage on the power outage line in the Taiwan area, the host of the low-voltage leakage locator injects a characteristic signal into the faulty line. The characteristic signal includes a voltage signal for leakage assessment and a pulse signal for leakage positioning. The low-voltage leakage positioning instrument The magnetic core coil sensor of the instrument slave machine receives the characteristic signal and outputs an induction signal. The induced voltage of the induction signal is proportional to the rate of change of the voltage of the characteristic signal injected into the host machine of the low-voltage leakage locator.

The low-voltage leakage locator host uses a pulse signal as a characteristic signal injected into the fault line; the pulse signal is generated by a half-bridge circuit in the low-voltage leakage locator host.

In the leakage locating process, the host of the low-voltage leakage locator generates a coded frequency signal and injects it into the fault line according to the master-slave agreement. Only one phase of the fault line is signal-injected with the characteristic coded signal at a time, and then the characteristic coded signal is injected into the leakage fault line. Along the way, a low-voltage leakage locator is used on the slave machine to decode characteristic signals in a non-contact manner. The location of the leakage fault point is first roughly segmented, and then the leakage fault point is accurately located.

The software of the low-voltage leakage locator host is based on the Linux+QT architecture. When executing a long-time leakage assessment operation, a separate thread operation is used to avoid affecting the execution of other software modules;

When generating the encoded frequency signal for signal injection, the injection signals of A-phase, B-phase, C-phase, and N-phase use the same encoding method, and the signal content of the injection signals of A-phase, B-phase, C-phase, and N-phase is different. ;

The low-voltage leakage locator slave machine includes a magnetic core coil sensor, a low-voltage leakage locator slave machine PCB and a battery;

After the low-voltage leakage locator host injects a characteristic signal into the fault line, the characteristic signal generates a magnetic field around the fault line. Assume that the voltage of the characteristic signal injected by the low-voltage leakage locator host into the leakage fault line is V, the frequency is F, and the ground resistance of the fault line is R, If the current I flows through the fault line, then according to Biot-Savart's law, the magnetic induction intensity B at a distance d from the fault line can be obtained as:

Among them, μ ₀ is the vacuum magnetic permeability, μ ₀ =4π×10 ^-7 Tesla·meter/ampere;

The slave machine of the low-voltage leakage locator receives the magnetic field of the characteristic signal through the magnetic core coil sensor and interprets the special signal. According to Faraday's law of electromagnetic induction, the magnitude of the induced electromotive force ξ output by the magnetic core coil sensor is related to the change rate of the magnetic flux passing through the loop. Directly proportional to

The slave machine of the low-voltage leakage locator receives the output signal of the magnetic core coil sensor and demodulates it, and then identifies whether the demodulated signal is a characteristic signal injected by the host machine of the low-voltage leakage locator.

Example 1:

When performing slave detection on a faulty line to locate the leakage fault point, first roughly segment the entire faulty line and select several points to be tested. Turn on the slave machine, open the offline/online dual-channel microcurrent leakage diagnosis equipment assistant app, connect to Bluetooth, click "Start Monitoring", and place the "detection area" of the slave machine close to the line under test and keep it perpendicular to the line under test. After hearing the beeping sound from the Assistant APP, go to the next point to be tested and test until you no longer hear the beeping sound. Then you can determine the rough location of the fault (the line fault point is between the beeping sound and no sound). time), based on this principle, gradually narrow the scope until the line fault point is found.

After processing the line fault point, conduct offline leakage assessment on the faulty line again. If the result is a fault-free line, it means that the fault has been eliminated. If the line is still measured as a faulty line, it means that the line has multiple fault points. Then perform slave machine detection again to continue troubleshooting.

Claims (1)

1. The off-line leakage assessment method of low-voltage leakage is used for accurately selecting lines of leakage faults of a transformer area and accurately positioning the positions of the leakage faults, and is characterized in that: the off-line leakage assessment method comprises the steps that under the condition that a tested line is in a power failure state, a host computer of a low-voltage leakage locator is used for applying specific voltage to A, B, C, N four-phase lines of a tested platform area, current sampling circuits are used for measuring injection currents of the four-phase lines, resistance values of the tested line are calculated, ground resistance values of all the phases are measured according to a complex leakage model, leakage current and daily average leakage electric quantity of all the phase lines of the tested platform area are calculated according to A, B, C, N ground resistance values, leakage assessment is conducted on the tested platform area, and when the ground resistance value of any one phase is smaller than a threshold value, leakage faults of the platform area are judged;

in the complex electric leakage model, R _A0 、R _B0 、R _C0 、R _N0 The insulation resistance values of the A phase, the B phase, the C phase and the N phase, which are required to be measured during off-line leakage evaluation, are evaluated that no leakage occurs in the phase if the insulation resistance value is infinite, and the phase is evaluated that the leakage occurs if the insulation resistance value is a specific value which can be measured in a measuring range, and the following formula exists in a model;

in the formulas nine to fifteen, the phase-A and phase-N interphase resistors R _AN Phase B and phase N interphase resistance R _BN C-phase to N-phase resistance R _CN Phase-to-phase resistance R _AG Phase B and phase G phase resistance R _BG C-phase to G-phase resistance R _CG N-phase to G-phase resistance R _NG R is calculated according to the formulas nine to fifteen for the known quantity measured by the low-voltage leakage locator host _A0 、R _B0 、R _C0 、R _N0、 R _AN0 、R _BN0 、R _CN0 Values.