CN106483360A - Method using 220V power supply on-line monitoring arrester resistance current - Google Patents

Abstract

The invention provides a method for online monitoring the resistive current of an arrester by using a 220V power supply. The method includes the following steps: 1) adjusting the online monitoring condition of the power supply voltage; 2) simultaneously using the PT secondary voltage and the 220V power supply voltage in the substation as reference voltages Obtain current and voltage angle Φ and real-time current and voltage angle Φ1 respectively; 3) take the angle obtained by Φ-Φ1 as a constant angle, correct it constantly, and convert the real-time data of 220V power supply voltage into real-time data of PT secondary voltage; 4) pass the steps The corrected data in 3 and the current signal transformation of MOA obtain the fundamental voltage U1, the peak value of the fundamental current Ix1p, and the current-voltage angle Φ; 5) judge the performance of the MOA by the current-voltage angle Φ and the peak value of the resistive current fundamental Ir1p. The above solution solves the problems of inconvenient installation and short-circuit risk in selecting the PT secondary reference voltage for the on-line monitoring system of the resistive current of the arrester.

Description

The Method of On-line Monitoring the Resistive Current of Surge Arrester Using 220V Power Supply

technical field

The invention relates to the technical field of electric power online monitoring, in particular to an online monitoring system for lightning arresters.

Background technique

Surge arrester is an important primary equipment in power production in the power industry. Its main function in substations (boosting and stepping down stations) and lines is to protect other equipment from lightning overvoltage and system surge overvoltage. Since the 1980s, metal oxide arresters (MOA) have gradually replaced SiC arresters. Due to the good volt-ampere characteristics of metal oxide arresters, the protection level of major equipment in power production has made a qualitative leap. With the popularization of MOA, its operation status has been paid more and more attention by the industry.

Most of the zinc oxide arresters used in substations around the world no longer have series gaps. During the operation of MOA, there is always a certain leakage current passing through the valve plate, which will accelerate the aging of the valve plate——moisture and aging are the root causes of the inferior degradation of MOA valve plates . Generally, under normal operating conditions, the main current flowing through the arrester is capacitive current, and the resistive current only occupies a small part, about 10%-20%. The resistive component of the detected arrester mainly includes: the surface leakage of the inner and outer surfaces of the porcelain sleeve, the surface leakage of the valve plate and its own nonlinear resistance component, and the leakage of the insulating support. When the valve plate of the arrester is aging, the arrester is damp, and the internal insulating parts of the arrester are damaged, the capacitive current does not change much, but the resistive current increases greatly. The main cause of arrester accidents is that after the resistive current increases, the loss increases, causing thermal breakdown. Therefore, measuring AC leakage current and resistive current is the main method to detect arresters.

At present, the detection method for judging the resistive current of zinc oxide arrester is to use the live tester of zinc oxide arrester for live detection. The regulations require that the detection frequency is "110kV and above once a year before the thunderstorm season", and the interval between the two live tests is long, and it is difficult to detect sudden resistive current over-limit faults. Therefore, it is necessary to develop an online monitoring system for the resistive current of the zinc oxide arrester, which can measure the resistive current of the zinc oxide arrester at any time, so as to understand the aging and moisture status of the arrester in real time. When it is found that the resistive current of the arrester exceeds the limit, the system will automatically alarm to ensure that the transportation inspection department can obtain the operation status of the equipment at the first time, so as to conduct expert analysis and troubleshooting to ensure the safe operation of the power grid.

Most of the current online monitoring methods are to select the PT secondary voltage as the reference voltage and introduce it into the input channel of the online monitoring system. However, choosing the PT secondary voltage as the reference voltage not only has the problem of inconvenient installation and maintenance, but also has the risk of short circuit.

Contents of the invention

The present invention provides a method for online monitoring of arrester resistive current by using 220V power supply, which solves the problems of inconvenient installation and short-circuit risk in selecting PT secondary reference voltage in the arrester resistive current online monitoring system in the prior art.

Technical scheme of the present invention is realized like this:

A method for monitoring the resistive current of an arrester online using a 220V power supply, the method includes the following steps:

1) Adjust the frequency of the power supply voltage to be consistent with the frequency of the grid, and ensure that the angle between the MOA and the three-phase grid bus is stable;

2) At the same time, the current and voltage angle Φ and the real-time current and voltage angle Φ1 are respectively obtained by using the PT secondary voltage and the 220V power supply voltage in the substation as reference voltages;

3) Take the angle obtained by Φ-Φ1 as a constant angle, and modify it constantly to convert the real-time data of the 220V power supply voltage into the real-time data of the PT secondary voltage;

4), remove the PT secondary voltage measuring equipment, input the data corrected in step 3 and the current signal of MOA to the surge arrester live tester, and transform to obtain the voltage fundamental wave U1, the current fundamental wave peak value Ix1p and the current voltage angle Φ.

5) Judging the MOA performance by using the current voltage angle Φ and the voltage in-phase component as the resistive current fundamental peak value Ir1p.

As a further technical solution, the transformation in step 4 is Fourier transformation.

Beneficial effects of the present invention:

1. When the monitoring method proposed by the present invention is used for online monitoring, since the 220V power supply voltage is selected as the reference voltage, the installation and operation of the lightning arrester online monitoring system can be installed and operated without opening the PT junction box for secondary voltage wiring, avoiding the secondary voltage of the PT Risk of short circuit to voltage.

2. In the case of 500kV anti-interference, the leakage current of the arrester can be accurately measured. Adopting the monitoring method proposed by the present invention, the monitoring system only has a magnetic connection with the primary equipment, and there is no electrical connection. The installation of the device does not change any wiring and operation mode of the original zinc oxide arrester, and will not cause any interference and influence on the primary system. , reduce device failure rate, extend online monitoring life, and reduce maintenance workload.

Description of drawings

Fig. 1 is a schematic diagram of the design principle of the present invention.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

The present invention will be further described below in conjunction with accompanying drawing.

A method for monitoring the resistive current of an arrester online using a 220V power supply, the method includes the following steps:

1) Adjust the frequency of the power supply voltage to be consistent with the frequency of the grid, and ensure that the angle between the MOA and the three-phase grid bus is stable;

2) At the same time, the current and voltage angle Φ and the real-time current and voltage angle Φ1 are respectively obtained by using the PT secondary voltage and the 220V power supply voltage in the substation as reference voltages;

3) Take the angle obtained by Φ-Φ1 as a constant angle, and modify it constantly to convert the real-time data of the 220V power supply voltage into the real-time data of the PT secondary voltage;

4), remove the PT secondary voltage measuring equipment, input the data corrected in step 3 and the current signal of MOA to the surge arrester live tester, and transform to obtain the voltage fundamental wave U1, the current fundamental wave peak value Ix1p and the current voltage angle Φ.

5) Judging the MOA performance by using the current voltage angle Φ and the voltage in-phase component as the resistive current fundamental peak value Ir1p.

As a further technical solution, the transformation in step 4 is Fourier transformation.

1. Measuring principle

After the input current and voltage are digitally filtered, the fundamental wave is taken out, and then the peak value of the resistive current fundamental wave is calculated by projection method Ir1p=Ix1pcosΦ. Because the fundamental wave value is stable, Ir1p is generally used to measure the performance of the arrester.

The peak value of the total current fundamental wave Ix1p is projected in the direction of the voltage fundamental wave U1 as the peak value of the resistive current fundamental wave (Ir1p), and projected in the vertical direction as the peak value of the capacitive current fundamental wave (Ic1p), and Φ is the phase angle of the current and voltage fundamental wave. Therefore, both Φ and Ir1p can be used to directly measure the performance of MOA.

Two, the design principle of the present invention

As shown in Figure 1: the present invention proposes a monitoring method to simultaneously measure the secondary voltage of the PT and the voltage of the 220V power supply in the substation, and use the two voltages as reference voltages. According to the above measurement principle, the current and voltage angle Φ and real-time The current and voltage angle Φ1, since the two are data on the same line and at the same time point, the difference between the two is a constant value. According to this phenomenon, the voltage of the 220V power supply in the substation is constantly corrected through the instrument. Therefore, the real-time data of the PT secondary voltage can be measured and calculated through the 220V power supply voltage in the substation, thereby realizing online monitoring.

3. Judgment criteria

1. The instrument inputs the PT secondary voltage as a reference signal, and at the same time inputs the MOA current signal. After Fourier transform, the voltage fundamental wave U1, the current fundamental wave peak value Ix1p and the current voltage angle Φ can be obtained. Therefore, the in-phase component with the voltage is the resistive current fundamental peak (Ir1p), and the quadrature component is the capacitive current fundamental peak (Ic1p):

Ir1p=Ix1pcosΦ Ic1p=Ix1psinΦ

Considering that δ=90°-Φ is equivalent to the dielectric loss angle, it is also very simple to directly use Φ to evaluate MOA: when there is no "phase interference", Φ is mostly between 81° and 86°. According to the requirement of "the resistive current cannot exceed 25% of the total current", Φ cannot be less than 75.5°. The following table evaluates the performance of MOA in sections:

performance <75° 75°～77° 78°～80° 81°～83° 84°～89° >89°

Φ inferior Difference middle good excellent There is interference

Attention should be paid when Φ<80°.

2. Interference between phases

The cause of interphase interference: when measuring three-phase MOA, due to the influence of interphase interference, the current phases of phase A and C will shift to the direction of phase B. Generally, the offset angle is about 2°~4°, which leads to an increase in the resistive current of phase A , C phase becomes smaller.

The principle of automatic compensation of the tester is: Assume that the influence of B relative to A and C is symmetrical, measure the angle Φca at which Ic leads Ia, A-phase compensation Φ0a=(Φca-120°)/2, C-phase compensation Φ0c=-(Φca- 120°)/2. This method actually carries out the software arithmetic mean to the resistive current of A and C phases.

In fact, the influence of B relative to A and C is symmetrical, which is an assumption. The situation at the substation site is complicated, and the influence of B relative to phase A and C is not necessarily symmetrical; moreover, some three-phase arresters are not arranged in a "one-word" arrangement, but in a "triangular" arrangement. . Therefore, the average compensation of pure software may affect the data judgment of phase A and phase C. In addition, the resistive current of phase A (phase C) affected by phase B increases (decreases), which indeed increases (decreases) the active power on the resistive valve plate of the arrester. If the "automatic side compensation" is used for arithmetic compensation , the obtained value is not the true value of phase A (phase C). Therefore, the surge arrester live test proposed by the present invention uses the "disable compensation" method.

4. Application Examples

Embodiment one

In April 2015, the Zhengzhou 500KV substation of the maintenance company of the State Grid Henan Electric Power Company adopted a method of using the 220V power supply to monitor the resistive current of the arrester online, and compared it with the secondary voltage monitoring of the PT, and displayed the results in real time All are the same, randomly selected as the data at 18:52:53 on April 25, as follows:

Embodiment two

In April 2015, the Zhengzhou 110kV substation of the State Grid Zhengzhou Power Supply Company adopted a method of using the 220V power supply to monitor the resistive current of the arrester online, and compared it with the secondary voltage monitoring of the PT. The real-time display results were the same. Randomly select the data at 11:44:31 on April 20, as follows:

To sum up, the monitoring data results shown in Example 1 show that no abnormality occurs; the monitoring data results shown in Example 2 show that the comprehensive performance evaluation of phase A and phase C of the arrester is inferior and needs to be repaired.

Using the 220V power supply as the reference voltage after compensation and correction, the obtained monitoring data is the same as the PT secondary voltage as the reference voltage for online monitoring of the resistive current of the arrester, and the installation and operation of the arrester online monitoring system does not need to open the PT junction box The wiring of the secondary voltage avoids the danger of short circuit of the PT secondary voltage.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention within.

Claims (2)

1. utilize the method for 220V power supply on-line monitoring arrester resistance current it is characterised in that institute The method of stating includes following step：

1), regulating power source voltage frequency is consistent with mains frequency, and guarantees the folder of MOA and electrical network bus three-phase Angle is stable；

2), distinguished as the reference voltage with 220V power supply voltage in PT secondary voltage and transformer station simultaneously Obtain current/voltage angle, φ and real-time current level angle Φ 1；

3), with the angle obtained by Φ-Φ 1 as constant angle, constantly revise, 220V is powered electricity Source voltage real time data is changed into PT secondary voltage real time data；

4) PT secondary voltage measuring apparatus, are removed, by the electric current of the data revised in step 3 and MOA Signal input, to lightning arrester with electrical testing meter, converts and obtains voltage fundamental U1, current first harmonics peak I x1p and electricity Stream level angle Φ.

5), pass through current/voltage angle, φ and arc in phase component to judge for resistance current fundamental peak Ir1p MOA performance.

2. the method for claim 1 it is characterised in that：It is transformed to Fourier in described step 4 Conversion.