CN106526356A - Metal oxide lightning arrester live-line detection validity test system - Google Patents

Abstract

The invention relates to a live detection effectiveness test system for a metal oxide arrester, which includes a DC test circuit and an AC test assembly, the DC test circuit includes an AC part and a rectification part, and realizes the measurement of the leakage current of the metal oxide arrester test product under DC voltage For measurement, the AC test assembly includes an AC test circuit and a high and low temperature test box, and the metal oxide arrester sample is set in the high and low temperature test box to realize the test of the influence of external factors on the characteristic parameters of the metal oxide arrester sample. Compared with the prior art, the present invention studies the influence of external factors, such as temperature, charging rate, external insulation surface contamination, etc., on the characteristic parameters of the metal oxide arrester, and the test results can be applied to the charged detection of the metal oxide arrester , Improve the accuracy and effectiveness of the live detection test.

Description

A metal oxide arrester live detection effectiveness test system

technical field

The invention belongs to the field of electrical engineering, and in particular relates to a live detection effectiveness test system of a metal oxide arrester.

Background technique

Zinc oxide surge arrester (referred to as MOA) is an important protection line of defense for power system equipment, and its operating status directly affects its effect on protecting other equipment. Live detection is an important means to check the operation status of zinc oxide arrester. However, today's MOA state detection cannot guarantee validity and correctness. A number of ultra-high voltage power stations said that the change of the characteristic parameters of the arrester cannot directly indicate the occurrence of faults and accidents, and sometimes the inspectors cannot make effective judgments based on the existing fault criteria, and may even make misjudgments that consume manpower and material resources to detect power outages affect normal operation. Therefore, further research is needed to propose more accurate and effective detection methods and fault criteria.

Under the continuous operating voltage, the continuous current I _x flowing through the zinc oxide resistor is composed of resistive current I _R and capacitive current I _C. Since the equivalent resistance R is a nonlinear resistance, the resistive current I _R is a non-linear resistance. Sinusoidal waveform, containing fundamental, third, fifth and higher harmonic components, mainly based on fundamental and third harmonic currents. The equivalent capacitance C is a linear capacitance, and its capacitance value does not change much when the small capacitance C changes with the voltage. Therefore, when the voltage variation range is small, the equivalent capacitance is approximately a constant value. The capacitive current I _C flowing through the capacitor C has the same waveform as the bus voltage U _x . Among the above current components, the resistive current will cause active power loss, resulting in heating and aging of the valve plate. However, since the resistive current only accounts for 10% to 20% of the total leakage current, the heating power consumption of the zinc oxide arrester resistor plate in the working state very low. However, as the insulation performance of zinc oxide resistors decreases, the changes in the above-mentioned current components are different. When the insulation performance of the arrester decreases, the overall performance is that the resistive current increases, and the capacitive current basically does not change. Since the proportion of resistive current is too small, the continuous current does not change much.

Moisture and aging of zinc oxide resistors are the main reasons for the reduction of the insulation performance of zinc oxide arresters. Relevant literature shows that moisture and aging cause different components in the resistive current to rise in different degrees. Therefore, in the analysis of the leakage current of resistors, this paper selects The resistive fundamental current and the resistive tertiary current are used as characteristic parameters, and the continuous current is measured at the same time for comparison.

In addition, in order to better observe the change of insulation performance, the zinc oxide resistor is also measured at a DC 1mA reference voltage and the leakage current at 0.75U _1mA .

In the live detection of metal oxide arresters, the influence of external factors on the characteristic parameters of arresters is not considered. However, with the improvement of MOA manufacturing technology and the adjustment of resistor sheet formulation process, the state parameter characteristics of MOA have changed significantly, and the traditional MOA state detection method cannot guarantee the validity and correctness of detection. The test results of several ultra-high voltage power stations in operation show that the change of the characteristic parameters of the arrester cannot directly reflect the occurrence of faults and accidents, and the testers sometimes cannot give effective and accurate judgments on the MOA status based on the existing test data. It is even possible to make a misjudgment and consume manpower and material resources to detect power outages and affect normal operation. In the field handover test of AC UHV MOA, the leakage current measured by the same MOA in different environments is very different. In addition, in the live detection of UHV MOA, some leakage current and resistive current exceed the MOA of the operating regulations. No problems were found during the subsequent full-scale test at the factory. This questioned the effectiveness of UHV MOA live detection and the adaptability of fault criteria.

Contents of the invention

The object of the present invention is to provide a metal oxide arrester electrification detection effectiveness test system in order to overcome the above-mentioned defects in the prior art, and improve the accuracy and effectiveness of the zinc oxide arrester live detection test.

The purpose of the present invention can be achieved through the following technical solutions:

A metal oxide arrester live detection effectiveness test system, including a DC test circuit and an AC test assembly, the DC test circuit includes an AC part and a rectification part, to realize the measurement of the leakage current of the metal oxide arrester test product under DC voltage, the The AC test assembly includes an AC test circuit and a high and low temperature test box, and the metal oxide arrester sample is arranged in the high and low temperature test box to realize the test of the influence of external factors on the characteristic parameters of the metal oxide arrester sample.

The AC part of the DC test circuit has the same structure as the AC test circuit, and both include AC power components, protective resistors, sampling resistors, capacitive voltage dividers and oscilloscopes, and the AC power components, protective resistors, and capacitive voltage dividers form a loop , the metal oxide arrester sample and the sampling resistor are connected in parallel with the capacitor voltage divider after being connected in series, and the oscilloscope is respectively connected to both ends of the sampling resistor and the secondary end of the capacitor voltage divider.

The rectifying part of the DC test circuit includes a rectifying silicon stack and a rectifying capacitor. The anode of the rectifying silicon stack is connected to a protective resistor, and the cathode is respectively connected to a metal oxide arrester test sample and one end of the rectifying capacitor. The other end of the rectifying capacitor is connected to the AC Power component connections.

The AC power supply assembly includes a power supply, a voltage regulator and a transformer connected in sequence, and the transformer is an isolation transformer.

The implementation of the measurement of the leakage current of the metal oxide arrester test product under DC voltage is specifically:

a1) Adjust the AC power supply components, use the oscilloscope to make the current of the metal oxide arrester test product 1mA, record the secondary terminal voltage u ₂ of the capacitor voltage divider, and obtain the DC 1mA reference voltage of the metal oxide arrester test product;

a2) Continue to adjust the AC power supply components so that the secondary terminal voltage of the capacitor voltage divider is 0.75u ₂ , record the voltage at both terminals of the sampling resistor, and obtain the leakage current at 75% of the DC reference voltage of the metal oxide arrester sample.

The test to realize the influence of external factors on the characteristic parameters of metal oxide arrester samples is specifically:

b1) Adjust the AC power supply components, load the long-term operating voltage of the metal oxide arrester sample, change the temperature of the metal oxide arrester sample through the high and low temperature test chamber, measure the leakage current of the metal oxide arrester sample, and study the temperature effect on the metal oxide arrester. The influence of the characteristic parameters of the arrester test product;

b2) Adjust the AC power supply components, keep the temperature of the metal oxide arrester sample constant, change the operating voltage of the metal oxide arrester sample, measure the leakage current of the metal oxide arrester sample, and study the effect of the charge rate on the metal oxide arrester The influence of the characteristic parameters of the sample;

b3) Load the continuous operating voltage of the metal oxide arrester sample, change the surface pollution degree of the metal oxide arrester sample, measure the leakage current of the metal oxide arrester sample, and study the impact of the pollution degree of the outer insulating surface of the metal oxide arrester sample on the metal oxide arrester sample. The influence of the characteristic parameters of oxide arrester test samples.

The maximum output voltage of the transformer is 20kV.

Compared with the prior art, the present invention has the following beneficial effects:

1) The present invention designs a set of test system according to the characteristics of the small current area of MOA according to the operating state of MOA and the test requirements of charging detection, and studies external factors, such as temperature, charge rate, contamination of the outer insulating surface, etc., to metal oxidation The influence of the characteristic parameters of the metal oxide arrester, the test results can be applied to the live detection of the metal oxide arrester, and the accuracy and effectiveness of the live detection test can be improved.

2) The structure of the test circuit of the present invention is simple, and the test operation is convenient.

3) The test system of the present invention adopts an isolation transformer to isolate the power supply of the test circuit to prevent the test circuit from raising the ground voltage to cause harm to the oscilloscope and effectively protect the oscilloscope.

Description of drawings

Fig. 1 is the structural representation of DC test circuit of the present invention;

Fig. 2 is the structural representation of the AC test circuit of the present invention;

Fig. 3 is a schematic diagram of the process of processing test data in the present invention.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is carried out on the premise of the technical solution of the present invention, and detailed implementation and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

This embodiment provides a metal oxide arrester live detection effectiveness test system, including a DC test circuit and an AC test component, the DC test circuit includes an AC part and a rectification part, and realizes the leakage current of the metal oxide arrester under DC voltage The AC test assembly includes an AC test circuit and a high and low temperature test chamber, and the metal oxide arrester sample is set in the high and low temperature test chamber to realize the test of the influence of external factors on the characteristic parameters of the metal oxide arrester sample . The characteristics of this test system are:

1. This test system is mainly aimed at the small current characteristics of metal oxide arrester resistors;

2. This test system covers all internal and external factors that affect the characteristic parameters of metal oxide arresters.

Since the characteristic parameters of the metal oxide arrester resistor (MOV) and the overall arrester (MOA) have a simple cumulative relationship, this test system is carried out for the metal oxide arrester resistor.

1. DC test circuit

As shown in Figure 1, the DC test circuit includes an AC part and a rectification part. The AC part includes a power supply U, a voltage regulator TV, a transformer TM, a protection resistor R1, a sampling resistor R2, capacitors C1, C2 and an oscilloscope, a power supply U, a voltage regulator The transformer TV and the transformer TM are connected in sequence, the capacitors C1 and C2 form a capacitor voltage divider, the transformer TM, the protection resistor R1, and the capacitor voltage divider form a loop, and the metal oxide arrester sample MOA and the sampling resistor R2 are connected in series with the capacitor voltage divider In parallel, the two ends of the sampling resistor R2 and the secondary end of the capacitor voltage divider are respectively connected to an oscilloscope. The rectification part includes a rectification silicon stack D and a rectification capacitor C. The anode of the rectification silicon stack D is connected to the protection resistor R1, the cathode is respectively connected to MOA and one end of the rectification capacitor C, and the other end of the rectification capacitor C is connected to the transformer TM.

Among them, the protection resistor R1 can prevent the loop current from being too large, and its parameter is 3.5MΩ; the sampling resistor R2 is a precision sampling resistor, whose resistance value is almost unchanged with temperature and voltage, and its parameter is 2kΩ; V1 and V2 are voltmeters, determined by Oscilloscope measurements.

The DC U _1mA of the MOV test product is all within 10kV, so the test system uses a transformer with a maximum output voltage of 20kV, a maximum output current of 400mA, and a capacity of 5kVA. The voltage regulator model is TDDC-3kVA, the input voltage is 220V, and the output voltage range is 0V～250V. A silicon stack is used for rectification, and a water resistance is set in the circuit as a protection resistance. The measuring instrument is a DPO4032 oscilloscope produced by Tektronix.

According to the test conditions in the laboratory, since the half-wave rectification will produce large pulsation, in order to ensure the quality of the DC voltage, the condition that the DC pulsation does not exceed ±3% must be met. The rated DC average voltage of the test product is U _d , the rated DC average current is I _d , and the calculation formula of the DC voltage ripple coefficient S is as follows:

The selection of capacitance parameters is determined by formula (2):

In the formula, f is the test voltage frequency, C is the rectification capacitance value, U _d is the rated DC average voltage of the test product, I _d is the rated DC average current, and S is the DC voltage ripple coefficient.

According to the factory parameters of the test product, it can be seen that U _1mA is about 4kV ~ 9kV, and the average current I _d does not exceed 20mA. Putting each parameter into the formula can calculate C _min = 833.3nF, so the capacitance value in the loop should exceed 834nF . According to the laboratory conditions, a capacitor with a capacitance value of 1μF and a withstand voltage of 20kV can be selected.

In order to protect the oscilloscope, we use an isolation transformer to isolate the power supply of the test circuit to prevent the test circuit from raising the ground voltage and causing harm to the oscilloscope.

R2 is a precision sampling resistor with a resistance value of 2kΩ. By measuring its voltage, the current i of the metal oxide arrester sample can be obtained.

In the formula, u _R is the voltage of R2, the unit is V, and i is the current of the metal oxide arrester sample, the unit is mA.

Oscilloscope 2 displays the voltage as the secondary voltage u ₂ of the high-voltage capacitive divider, and the primary voltage

u ₁ =n×u ₂

In the formula, u ₁ is the high-voltage terminal voltage of the arrester test product, u ₂ is the secondary voltage of the voltage divider, C ₁ is the high-voltage capacitor of the voltage divider, C ₂ is the low-voltage capacitor of the voltage divider, and n is the capacitor voltage division ratio.

The voltage loaded on the metal oxide arrester sample can be calculated by the following formula,

However, since the equivalent resistance of the oxide arrester is much larger than the sampling resistance R2, u _MOA =u ₁ is approximately taken in the test.

experiment method:

1) Adjust the voltage regulator, slowly increase the test voltage, so that the voltage in oscilloscope 1 is 2V, that is, the current of the metal oxide arrester test product is 1mA, record the voltage u ₂ in oscilloscope 2, and convert the primary voltage u ₁ , which is The DC 1mA reference voltage of the test object.

2) Continue to adjust the voltage regulator, slowly reduce the test voltage, so that the voltage in oscilloscope 2 is 0.75u ₂ , record the voltage in oscilloscope 1, and calculate the current of the test product, which is the 75% DC reference of the metal oxide arrester test product Leakage current at voltage.

2. AC test components

The AC test components include an AC test circuit and a high and low temperature test chamber. The AC test circuit is shown in Figure 2, including a power supply U, a voltage regulator TV, a transformer TM, a protection resistor R1, a sampling resistor R2, capacitors C1, C2 and an oscilloscope , the power supply U, the voltage regulator TV, and the transformer TM are connected in sequence, the capacitors C1 and C2 form a capacitor voltage divider, the transformer TM, the protection resistor R1, and the capacitor voltage divider form a loop, and the metal oxide arrester sample MOA and the sampling resistor R2 are connected in series Afterwards, it is connected in parallel with the capacitor voltage divider, and the two ends of the sampling resistor R2 and the secondary end of the capacitor voltage divider are respectively connected to an oscilloscope.

This test system mainly studies the change of characteristic parameters under MOA operating conditions, that is, the surge arrester works in the power frequency small current area. Normally, its leakage current is 0mA~5mA. The capacity of the voltage regulator and transformer used in the test system The requirements are the same as for the DC link.

The external factors of the test research include the temperature of the arrester body, so the GDH-2025A high and low temperature test chamber is selected to change the temperature of the test product. The technical parameters are shown in Table 1. In order to ensure the accuracy of the temperature, the test sample has been stored in the test box during the whole measurement process, and the temperature in the box is measured with a thermocouple to keep the same temperature throughout the test process.

Table 1 Technical parameters of GDH-2025A high and low temperature test chamber

experiment method:

1) Adjust the voltage regulator, load the long-term operating voltage of the MOA, change the temperature of the MOA, measure the leakage current of the MOA, and study the influence of temperature on the characteristic parameters of the MOA;

2) Adjust the voltage regulator to keep the temperature of the MOA constant, change the operating voltage of the loaded MOA, measure the leakage current of the MOA, and study the influence of the charge rate on the characteristic parameters of the MOA;

3) Load the continuous operating voltage of the MOA, change the pollution degree of the MOA surface, measure the leakage current of the MOA, and study the influence of the pollution degree of the outer insulation surface of the MOA on the characteristic parameters of the MOA;

3. Test data processing method

Since there are various current components in the leakage current of the zinc oxide resistor, the voltage waveform acting on the zinc oxide resistor and the leakage current waveform through the zinc oxide resistor are obtained through an oscilloscope and a precision sampling resistor.

All measured current values in this embodiment are peak values.

The peak value of the continuous current can be read from the current waveform, and the measurement of the peak value of the resistive current adopts the capacitive current compensation method. The principle is to fully compensate the capacitive current in the continuous current to obtain the resistive current. The principle can be expressed by the following formula (3):

In the formula, u _sf is obtained by shifting the voltage on the arrester to make it consistent with the phase of the capacitive current, and the phase shift angle is 90°; ix _is the full current value; G is the compensation coefficient. When the capacitive current is completely compensated, only the resistive current i _r remains, namely:

i _r =i _x -i _c =i _x -Gu _sf (4)

The compensation coefficient G can be obtained by formula (3), and the resistive current component can be obtained by formula (4).

In the actual data processing, first use Matlab to decompose the obtained voltage signal and current signal by FFT. After the decomposition, according to the Fourier transform corresponding relationship, you can read the peak value of the corresponding frequency component voltage or current component from the spectrum table, and then Compensation after phase shift is performed according to the phase angle relationship between voltage and current to obtain resistive fundamental wave current and resistive tertiary current values in the zinc oxide resistor sheet. which is:

i _r1 =i _x1 -i _c1 =i _x1 -Gu _sf1 (5)

i _r3 =i _x3 -i _c3 =i _x3 -Gu _sf3 6)

The specific process is shown in Figure 3, and the implementation steps are as follows:

1) Measure voltage waveform and full current waveform;

2) Decompose the voltage and current waveforms by FFT to obtain the fundamental wave and the third harmonic respectively;

3) Phase-shift the voltage fundamental wave signal to get u _sf1 to make it consistent with the capacitive current phase;

4) Compensate the capacitive current, the compensation coefficient is G, and obtain the resistive fundamental wave current i _r1 ;

5) Similarly, the capacitive current is compensated after phase-shifting the third harmonic of the voltage to obtain the resistive third harmonic current i _r3 .

Claims (7)

1. A metal oxide arrester live detection effectiveness test system is characterized in that it comprises a DC test circuit and an AC test assembly, and the DC test circuit includes an AC part and a rectification part, and realizes that the metal oxide arrester is tested under a DC voltage. For the measurement of leakage current, the AC test assembly includes an AC test circuit and a high and low temperature test chamber, and the metal oxide arrester test product is set in the high and low temperature test chamber to realize the influence of external factors on the characteristic parameters of the metal oxide arrester test product test. 2. metal oxide lightning arrester electrification detection effectiveness testing system according to claim 1, is characterized in that, the structure of the alternating current part of described direct current test loop and alternating current test loop is identical, all comprises alternating current power assembly, protective resistor, sampling Resistor, capacitive voltage divider and oscilloscope, described AC power supply component, protective resistor, capacitive voltage divider form a loop, described metal oxide lightning arrester sample and sampling resistor are connected in parallel with capacitive voltage divider after being connected in series, and described oscilloscope is respectively connected The two ends of the sampling resistor and the secondary terminal of the capacitor voltage divider. 3. metal oxide arrester electrification detection effectiveness testing system according to claim 2, is characterized in that, the rectification part of described DC test circuit comprises rectification silicon pile and rectification capacitor, the anode of described rectification silicon pile and protective resistor The cathode is respectively connected to the test object of the metal oxide arrester and one end of the rectifying capacitor, and the other end of the rectifying capacitor is connected to the AC power supply component. 4. The metal oxide arrester live detection effectiveness test system according to claim 2, wherein the AC power supply assembly includes a power supply, a voltage regulator and a transformer connected in sequence, and the transformer is an isolation transformer. 5. metal oxide lightning arrester electrification detection validity testing system according to claim 2, is characterized in that, the measurement of the leakage current under the described realization metal oxide lightning arrester sample DC voltage is specifically: a1) Adjust the AC power supply components, use the oscilloscope to make the current of the metal oxide arrester test product 1mA, record the secondary terminal voltage u ₂ of the capacitor voltage divider, and obtain the DC 1mA reference voltage of the metal oxide arrester test product; a2) Continue to adjust the AC power supply components so that the secondary terminal voltage of the capacitor voltage divider is 0.75u ₂ , record the voltage at both terminals of the sampling resistor, and obtain the leakage current at 75% of the DC reference voltage of the metal oxide arrester sample. 6. metal oxide arrester electrification detection effectiveness test system according to claim 2, is characterized in that, the test that described realization external factors influences the metal oxide arrester sample characteristic parameter is specifically: b1) Adjust the AC power supply components, load the long-term operating voltage of the metal oxide arrester sample, change the temperature of the metal oxide arrester sample through the high and low temperature test chamber, measure the leakage current of the metal oxide arrester sample, and study the temperature effect on the metal oxide arrester. The influence of the characteristic parameters of the arrester test product; b2) Adjust the AC power supply components, keep the temperature of the metal oxide arrester sample constant, change the operating voltage of the metal oxide arrester sample, measure the leakage current of the metal oxide arrester sample, and study the effect of the charge rate on the metal oxide arrester The influence of the characteristic parameters of the sample; b3) Load the continuous operating voltage of the metal oxide arrester sample, change the surface pollution degree of the metal oxide arrester sample, measure the leakage current of the metal oxide arrester sample, and study the impact of the pollution degree of the outer insulating surface of the metal oxide arrester sample on the metal oxide arrester sample. The influence of the characteristic parameters of oxide arrester test samples. 7. The metal oxide arrester live detection effectiveness test system according to claim 4, characterized in that the maximum output voltage of the transformer is 20kV.