JPS59201381A - Method of automatically detecting resistance current of arrester - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to deterioration detection of a lightning arrester such as a zinc oxide type lightning arrester whose leakage current includes a capacitance component, and particularly to detection of a resistance component current in the leakage current.

Deterioration of zinc oxide type lightning arresters and other lightning arresters that use non-linear resistance elements appears as changes in the non-linear characteristics of the resistance element, and concrete examples include changes in the leakage current waveform of the arrester when the rated voltage is applied, and changes in the current waveform. This occurs in the form of an increase in the peak value. Therefore, deterioration has traditionally been determined using these measurement elements.

However, the nonlinear resistance element of this type of lightning arrester has a capacitance, and the nonlinear resistance F(
It is expressed as a parallel circuit of a and a capacitance Ca. Therefore, the leakage current includes a capacitance current, and as a result, the leakage current waveform and peak value are also affected by the capacitance current and naturally differ. That is, since the resistance current iE flows based on the non-linear characteristics shown in FIG. 2, for example, when the applied voltage is a sine wave voltage e as shown in FIG. 3, it has a waveform as shown in [a] in the figure. On the other hand, since the capacitance current has no nonlinearity,
As shown at 1° in FIG. 3, a sine wave current leads the voltage e by 90°, and the leakage current L is the current l corresponding to this capacity. and the sum of the resistance component current la.

Therefore, the waveform and peak value of the resistive current la will be different from the original one, so it is important to erase the capacitive current by 1° in order to make a highly reliable determination of deterioration.

Therefore, in the past, for example, a voltage proportional to the leakage current of the lightning arrester and a voltage obtained by advancing the phase of the voltage applied to the lightning arrester by 90 are created and the difference between these is taken by a differential circuit, and at the same time, the output waveform is In order to obtain a unique waveform based on non-linear characteristics, the 90-lead voltage value is manually adjusted using a waveform observation device to eliminate the capacitive current. However, this method is not only cumbersome and time-consuming, but also may lack accuracy.In addition, there is a recent demand for automatic numerical display of the deterioration status of lightning arresters in the control switchboard room of power generation and substations. Therefore, we cannot meet the demand for constant monitoring, simple maintenance, and thorough system protection.

The present invention realizes accurate erasure of capacitance current from leakage current and automation thereof, thereby meeting the demand for constant display of deterioration in a control switchboard room. Next, the details will be explained and explained using the drawings.

The features of the present invention are as follows. That is, as shown in the circuit diagram shown in FIG. 4, the voltage Es obtained by advancing the phase of the voltage applied to the surge arrester by 90 degrees by the same means as the conventional method is applied to the H of the differential circuit DF through the applied gain control circuit OCA. Add to terminal. and (1) the difference between the voltage Ex proportional to the lightning arrester leakage current applied to the terminal]L (EX-Go-ES)
(G in this step 5 is the initial gain of the gain control circuit (])). On the other hand, this output is added to the synchronous component detection circuit SD which uses the voltage E8 as a reference signal, and the output is a DC voltage EY proportional to the capacitance component of the component in phase with the voltage ES, that is, (EX-C)o-E8). Detect. As a result, the initial gain G of the gain control circuit GCA. The human power required to control G and ES to a balanced gain G to cancel out the capacitance is converted into a differential circuit D.
The present invention is characterized in that a negative feedback circuit added to F is formed so that an output proportional to the resistive current can be obtained on the output side of the differential circuit DF.

FIG. 5 is a circuit diagram of an embodiment of the present invention based on the second idea, in which L is a power line, Ar is a lightning arrester, and I
D is a leakage current IL detector, for example, a clamp-type current transformer that can detect the current without opening the connection wire of the lightning arrester Ar, or a detection resistor inserted in series with the connection wire; It is installed on the grounding side of the lightning arrester to prevent it from occurring. 80 is an amplifier with high input impedance, and there is a leakage current 11 on the output side.
Obtain a voltage EX proportional to . The FD is a detector for the voltage applied to the lightning arrester, such as a winding voltage transformer, a capacitive voltage transformer, or a capacitive voltage transformer. A2 is an amplifier with high input impedance, and G is a phase shifter, which outputs a capacitance erasing voltage ES that advances the phase of the output voltage of the amplifier A2 by 90 degrees.

OCA is a gain control circuit, e.g. an amplifier, to which a voltage Es is applied, a voltage EX proportional to its beginning, and a voltage G of 4- from the gain control amplifier GOA. Es is added, and the difference output (Ex-Go-Es) is sent to the output side. SD is a common-mode detection circuit, and in FIG. 5, it consists of the following parts. ST
(S is a well-known synchronous rectifier, S is its synchronizing signal generator, for example, a zero point detection circuit, and S is its synchronizing signal generator, e.g., a zero point detection circuit of the output ES of the phase shifter 2). MS is an averaging circuit, for example, an integrating circuit, which smooths the output of the synchronous rectifier SR and converts it into the differential amplifier D.
A DC voltage EY is created that is proportional to the in-phase portion of the output of F, that is, Es of (EX-Co-ES). The gain of the gain control amplifier GOA is controlled by the voltage EY to provide a balanced gain G1, and generates capacitance components G1 and ES necessary to cancel the capacitance in "x".

In this way, an output proportional to the resistance current is automatically output to the output side of the differential amplifier DF, so for example, the output waveform or the peak value detected by a peak value detector (not shown) can be digitally processed. After that, the state of deterioration can be constantly monitored by converting it into numerical values and displaying it.

An embodiment of the present invention has been described above. In this method, a square wave whose polarity is reversed at the polarity reversal point of E8 generated by the synchronization signal generator SS is used as the synchronization signal of the synchronous rectifier S'R. This in-phase component detection circuit is based only on point Es. Therefore, in the case of resistive currents that flow based on non-linear characteristics as explained in FIGS. It is difficult to obtain only the resistance current. Therefore, it is necessary to eliminate this error depending on the degree of deterioration determination required, but this can be eliminated by using the following method.

That is, as shown in the partial circuit diagram shown in FIG. 6, the common-mode component detection circuit SD is connected to a multiplier MLT that multiplies the voltage Es described above and (EX-GoEs), which is the output of the differential amplifier DF.
It is formed by an averaging circuit MS.

Then, after extracting the in-phase portion of E8 of the voltage EX as electric power using a multiplier, from the output, (E
X-G. By setting the DC voltage EY to be proportional to Es)×Es, it is possible to eliminate errors in erasing due to synchronous rectification.

As is clear from the explanation in -4- below, according to the present invention, the resistance current required for determining the deterioration of lightning arresters, such as zinc oxide type lightning arresters and 810 lightning arresters, which include a capacitive current in the leakage current, can be easily calculated using a troublesome operation. This can be obtained automatically without the need for a deterioration detection system for lightning arresters, and will greatly contribute to the realization of a constant monitoring system.

[Brief explanation of drawings]

Figure 1 is an equivalent circuit of a lightning arrester, such as a zinc oxide type arrester, in which the leakage current includes a capacity component, Figures 2 and 3 are illustrations of leakage current waveforms, and Figure 4 is a block circuit diagram for explaining the principle of the present invention. ,
FIG. 5 is a block circuit diagram of one embodiment of the present invention, and FIG. 6 is a partial circuit diagram showing another example of the common-mode component detection circuit. 7- L...Power line, Ar...Surge arrester, ID...
・Leakage current detector, 80...Amplifier, ED...
・Applied voltage detector for lightning arrester, A...Amplifier, G...Phase shifter, GCA...Gain control circuit, (amplifier) DF...Differential circuit (amplifier), SD ... Common mode component detection circuit, SR ... Synchronous rectifier, 88 ... Synchronous signal generator, M L'r ... Multiplier, ' MS ... Average value circuit. Patent applicant: 1 person from outside the Central Research Institute of Electric Power Industry Representative patent attorney: Inuzuka 1 person from outside the university 8- Figure 1 Figure 2 Flash Y 3 Flash 4 Figure

Claims (1)

[Claims] A voltage Ex proportional to the leakage current of the lightning arrester and a voltage ES in phase with the capacitance current in the lightning arrester are applied to the differential circuit via a gain control circuit, and the output thereof is applied to the voltage E above.
In addition to the circuit that detects the DC voltage proportional to the component in phase with 8, an output proportional to the capacitance current of the lightning arrester is obtained, and this controls the gain control circuit described above to eliminate the capacitance component from the voltage Ex and prevent leakage. A method for automatically detecting a resistance current in a lightning arrester, which is characterized by automatically separating and detecting only the resistance current output from the current.