CN108919026B - Live detection method for leakage current of lightning arrester - Google Patents

Abstract

The invention relates to a method for electrification detection of arrester leakage current, which includes the following steps: obtaining three-phase leakage current and three-phase operating voltage, obtaining the phase angle of the current leading voltage, obtaining compensation angles φ _OA and φ _OC , and calculating the leakage current resistance. The linear components I _AR , I _BR and I _CR are used to determine the condition of the arrester; the advantages of the present invention are: it is simple and easy to obtain the three-phase operating voltage through the secondary side of the bus transformer, with strong anti-interference and high reliability; and then through the compensation angle φ _OA and φ _OC compensate for the angle between the voltage and current, which can basically eliminate the influence of arrester inter-phase interference on the measurement results; finally, the resistive component of the leakage current is calculated, which can better reflect the aging and moisture conditions of the arrester.

Description

A method for electrification detection of leakage current of lightning arrester

Technical field

The invention relates to a method for electrification detection of arrester leakage current.

Background technique

A lightning arrester is an electrical appliance used to protect electrical equipment from high transient overvoltage and to limit the freewheeling time and often the freewheeling value. It is usually connected between the grid wire and the ground wire, and is also connected next to the winding or wire of the electrical appliance. During the use of the arrester, the leakage current charged test of the arrester needs to be carried out. The main purpose is to measure the full current of the arrester and the peak value of the fundamental wave of the resistive current. Then based on the changes in these two values, it is judged whether the interior of the arrester is affected by moisture or metal oxides. Check whether the valve plate has deteriorated. The most commonly used methods for current live detection of leakage current of lightning arresters are the fundamental wave method and the waveform analysis method. When a group of three-phase arresters with normal performance are lined up in a row, the results of the live detection of leakage current are: It often appears that phase A resistive current > phase B resistive current > phase C resistive current. Sometimes, the resistive current of phase C may even be negative. However, when performing live detection of leakage current on a running arrester, it will be affected by The influence of phase interference leads to deviations in the measured full current and resistive current, thus affecting the judgment results of the inspection personnel.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for electrification detection of arrester leakage current, and to solve the existing technical problem of inaccurate test results caused by inter-phase interference.

In order to solve the above technical problems, the present invention is implemented through the following technical solutions: a method for electrification detection of arrester leakage current, which includes the following steps in sequence:

Step 1: Obtain the three-phase leakage current from the lower ground lead of the arrester. And obtain the three-phase operating voltage from the secondary side of the busbar voltage transformer/> And according to the three-phase leakage current Obtain the three-phase full current I _AX , I _BX and I _CX ;

Step 2: Obtained according to step 1 To calculate the phase angles φ _A , φ _B , and φ _C of the current leading voltage;

Step 3: Calculate the compensation angles φ _OA and φ _OC based on the φ _A and φ _C calculated in step two;

Step 4: Based on the phase angles φ _A , φ _B , φ _C calculated in step two, and the compensation angle calculated in step three

φ _OA and φ _OC find the leakage current resistive components I _AR , I _BR and I _CR ;

Step 5: Determine the condition of the arrester based on the three-phase full currents I _AX , I _BX and I _CX obtained in step 1 and the leakage current resistive components I _AR , I _BR and I _CR calculated in step 4.

Preferably, the three-phase leakage current in step one and three-phase operating voltage All are measured by AC sampling analyzer, and/> Expressed by the following formulas:

Among them: I _AX , I _BX and I _CX are the three-phase full current, φ _IA is The phase angle of φ _IB is/> The phase angle of , φ _IC is/> The phase angle of U _A is/> The amplitude of φ _UA is/> The phase angle of U _B is/> The amplitude of φ _UB is/> The phase angle of U _C is/> The amplitude of φ _UC is/> phase angle.

Preferably, the phase angles φ _A , φ _B , and φ _C in step 2 are calculated by the following formulas respectively, where:

φ _A =φ _IA -φ _UA ;

φ _B =φ _IB -φ _UB ;

φ _C =φ _IC -φ _UC .

Preferably, the compensation angles φ _OA and φ _OC in step three are calculated by the following formulas respectively, where:

φ _OA = (φ _C -φ _A )/2;

φ _OC =-(φ _C -φ _A )/2.

Preferably, the resistive components I _AR , I _BR , and I _CR in step 4 are calculated by the following formulas respectively, where:

I _AR =I _AX cos(φ _A +φ _OA );

I _BR =I _BX cosφ _B ;

I _CR = _ICX cos(φ _C +φ _OC ).

Prioritize, in step 5, judge the condition of the arrester through the following method: under the same environmental conditions, the increment of the leakage current resistive components I _AR , I _BR and I _CR should be ≤30% compared with the last or initial value. The increment of phase full current I _AX , I _BX and I _CX should be ≤20% compared with the last or initial value. When the leakage current resistive components I _AR , I _BR and I _CR increase by 0.3 times, the test period should be shortened and monitoring should be strengthened. , when the leakage current resistive components I _AR , I _BR and I _CR increase by 1 times, power outage should be checked.

To sum up, the advantages of this invention are: it is simple and easy to obtain the three-phase operating voltage through the secondary side of the busbar voltage transformer, with strong anti-interference and high reliability; and then the angle between the voltage and current is calculated through the compensation angle φ _OA and φ _OC . Compensation can basically eliminate the impact of the arrester's inter-phase interference on the measurement results; finally, the resistive component of the leakage current is calculated, which can better reflect the aging and moisture content of the arrester and ensure the detection quality of the inspector. When the arrester fails It can be inspected and repaired as soon as possible to ensure the reliable and stable operation of the arrester.

Description of the drawings

Figure 1 is the equivalent circuit diagram of the arrester’s phase interference;

Figure 2 is the phasor diagram of the arrester’s interphase interference leakage current.

Detailed ways

Since there is stray capacitance between the phases of the three-phase arrester, which will affect the amplitude and phase angle of the full current measured by the detection device, a lumped parameter circuit model is used to conduct a detailed analysis. The circuit model is shown in Figure 1. To simplify the problem, only the fundamental wave is analyzed. Z _A , Z _B , and Z _C respectively represent the self-impedance of the three phases of the arrester A, B, and C. The impedance angle is usually between -81° and -86°. Z _AB , Z _BA , Z _AC , Z _CA , Z _BC and _ZCB respectively represent the mutual impedance caused by interphase stray capacitance, and the impedance angle is -90°; the currents measured by the detection device are _IAX , _IBX , and _ICX .

When the three phases of the arrester are evenly distributed in a straight line, it can be considered that Z _A = Z _B = Z _C > Z _AB = Z _BA = Z _BC = Z _CB > Z _CA = Z _AC . Therefore, the leakage current phasor diagram can be obtained, as shown in Figure 2, where I _AX , I _BX , and I _CX are the total leakage currents detected by the instrument, while I _AA , I _BB , and I _CC are the total leakage currents that actually flow through the arrester. Current, it can be seen from Figure 2 that the measured value of leakage current I _BX after phase B is affected by inter-phase interference has a smaller amplitude than the actual leakage current I _BB through the phase B arrester, and the angle φ _B of the leakage current leading U _B is slightly become smaller. The phase angles of phase A and phase C are greatly affected. φ _A becomes significantly smaller and φ _C becomes significantly larger, generally causing a deviation of 2° to 4°.

A method for electrification detection of arrester leakage current, including the following steps:

Step 1: Obtain the three-phase leakage current from the lower ground lead of the arrester. And obtain the three-phase operating voltage from the secondary side of the busbar voltage transformer/> And according to the three-phase leakage current/> Obtain the three-phase full current I _AX , I _BX and I _CX ;

Step 2: Obtained according to step 1 To calculate the phase angles φ _A , φ _B , and φ _C of the current leading voltage;

Step 3: Calculate the compensation angles φ _OA and φ _OC based on the φ _A and φ _C calculated in step two;

Step 4: Based on the phase angles φ _A , φ _B , φ _C calculated in step two, and the compensation angle calculated in step three

φ _OA and φ _OC find the leakage current resistive components I _AR , I _BR and I _CR ;

Step 5: Determine the condition of the arrester based on the three-phase full currents I _AX , I _BX and I _CX obtained in step 1 and the leakage current resistive components I _AR , I _BR and I _CR calculated in step 4.

The three-phase leakage current in step one And three-phase operating voltage/> All are measured by AC sampling analyzer, and/> Expressed by the following formulas:

Among them: II _AX , I _BX and I _CX are the three-phase full current, φ _IA is The phase angle of φ _IB is/> The phase angle of , φ _IC is The phase angle of U _A is/> The amplitude of φ _UA is/> The phase angle of U _B is/> The amplitude of φ _UB is/> The phase angle of U _C is/> The amplitude of φ _UC is/> phase angle.

The phase angles φ _A , φ _B , and φ _C in step two are respectively calculated by the following formulas, where:

φ _A =φ _IA -φ _UA ;

φ _B =φ _IB -φ _UB ;

φ _C =φ _IC -φ _UC .

The compensation angles φ _OA and φ _OC in step three are calculated by the following formulas, where:

φ _OA = (φ _C -φ _A )/2;

φ _OC =-(φ _C -φ _A )/2.

The resistive components I _AR , I _BR , and I _CR in step four are respectively calculated by the following formulas, where:

I _AR =I _AX cos(φ _A +φ _OA );

I _BR =I _BX cosφ _B ;

I _CR = _ICX cos(φ _C +φ _OC ).

Step 5: Use the following method to judge the condition of the arrester: under the same environmental conditions, the increment of the leakage current resistive components I _AR , I _BR and I _CR should be ≤30% compared with the last or initial value, and the three-phase full current The increment of I _AX , I _BX and I _CX should be ≤20% compared with the last or initial value. When the leakage current resistive components I _AR , I _BR and I _CR increase by 0.3 times, the test period should be shortened and monitoring should be strengthened. When leakage When the current resistive components I _AR , I _BR and I _CR increase by 1 times, the power should be cut off and checked.

In addition to the above preferred embodiments, the present invention also has other embodiments. Those skilled in the art can make various changes and deformations according to the present invention. As long as they do not deviate from the spirit of the present invention, they shall all fall within the scope of the invention as defined by the appended claims. scope.

Claims (4)

1. A method for electrification detection of arrester leakage current, which is characterized in that it includes the following steps in sequence: Step 1: Obtain the three-phase leakage current from the lower ground lead of the arrester. ,/> ,/> , and obtain the three-phase operating voltage from the secondary side of the busbar transformer/> ,/> ,/> , and according to the three-phase leakage current/> ,/> ,/> Get three-phase full current/> ; Step 2: Obtained according to step 1 ,/> ,/> ,/> ,/> ,/> To calculate the phase angle of current leading voltage/> ; Step 3: Calculated according to step 2 To calculate the compensation angle/> , the compensation angle They are calculated by the following formulas, where: ; ; Step 4: Phase angle calculated based on step 2 , and the compensation angle calculated in step three/> Find the resistive component of the leakage current/> , the resistive component of the leakage current/> pass respectively Calculated by the following formula, where: ; ; ; Step 5: Based on the three-phase full current obtained in Step 1 And the leakage current resistive component calculated in step 4/> to judge the condition of the arrester. 2. A method according to claim 1, characterized in that: the three-phase leakage current in step one , ,/> , and three-phase operating voltage/> ,/> ,/> All are measured by AC sampling analyzer, and/> , ,/> ,/> ,/> ,/> Expressed by the following formulas: in: is the three-phase full current,/> for/> The phase angle of ,/> for/> The phase angle of ,/> for The phase angle of U _A is/> The amplitude of /> for/> The phase angle of U _B is/> The amplitude of /> for/> The phase angle of U _C is/> The amplitude of /> for/> phase angle. 3. A method according to claim 2, characterized in that: the phase angle in step two They are calculated by the following formulas, where: 4. A method according to claim 1, characterized in that: in step five, the condition of the arrester is judged by the following method: under the same environmental conditions, the resistive component of the leakage current Compared with the last or initial value, the increment should be ≤30%, three-phase full current/> Compared with the last or initial value, the increment should be ≤20%. When the leakage current resistive component/> When increasing by 0.3 times, the test period should be shortened and monitoring should be strengthened. When the resistive component of the leakage current When increasing by 1 times, power outage should be checked.