JPH0239074B2 - HIRAIKINOTEIKOBUNDENRYUJIDOKENSHUTSUHOHO - Google Patents

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 a change in the non-linear characteristics of the resistance element, and specific examples of this are changes in the leakage current waveform of the lightning arrester when the rated voltage is applied,
This occurs in the form of an increase in the peak value of the current. Therefore, deterioration has traditionally been determined using these measurement elements.

However, the non-linear resistance element of this type of lightning arrester has a capacitance, which is approximately equivalently represented as a parallel circuit of a non-linear resistance R _a and a capacitance C _a , as shown in FIG. 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 i _a 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, the waveform will be as shown in i _a in the figure. On the other hand, since the capacitance current does not have nonlinearity, it becomes a sine wave current that leads the voltage e by 90° as shown by i _c in Fig. 3, and the leakage current i _L is equal to this capacitance current i _c . It is the sum of the above resistance current i _a . Therefore, the waveform and peak value of the resistive current i _a will be different from the original one, so it is important to erase the capacitive current i _c in order to make a highly reliable determination of deterioration.

Therefore, in the past, for example, the phase of the voltage proportional to the leakage current of the arrester and the voltage applied to the arrester was changed.
At the same time, a waveform observation device is used to generate a 90° advanced voltage value and take the difference between them using a differential circuit. The current is erased by the capacitance by manual adjustment. However, this method is not only cumbersome and time-consuming, but also may lack accuracy, and there is also a recent demand for automatic numerical display of the deterioration status of lightning arresters in the control switchboard room of power generation and substations. However, this cannot meet the demands of simplifying maintenance and ensuring thorough protection of the system by enabling constant monitoring. The present invention realizes accurate erasure of capacitance current from leakage current and automation thereof, thereby meeting the above-mentioned demand for constant display of deterioration in a control switchboard room. Next, the details will be explained using the drawings.

The features of the present invention are as follows. In other words, as shown in the circuit diagram shown in Figure 4, the phase of the voltage applied to the surge arrester made by the same method as before is set at 90°.
The advanced voltage E _S is applied to the (-) terminal of the differential circuit DF via the gain control circuit GCA. And (+)
Find the difference _{( EX -} G _{O ·} ES) between the voltage E On the other hand, this output is a common mode component detection circuit that uses voltage E _S as a reference signal.
In addition to SD, a DC voltage E _Y proportional to the capacitance component of the component in phase with the voltage E _S , that is, ( _EX − G _O · E _S ) is detected at the output. This forms a negative feedback circuit that controls the initial gain G _O of the gain control circuit GCA to a balanced gain G ₁ and adds the input G ₁ E _S necessary to cancel the capacitance to the differential circuit DF. This is characterized in that an output proportional to the resistance current can be obtained on the output side of the differential circuit DF.

That is, the voltage e applied to the arrester is e=e ₀ sinω ₀ t, and as shown in Figure 1, the resistance of the arrester is R _a , the capacitance is C _a , the current flowing through the arrester is i _t , and the resistance current is
If i _R is the capacitance current i _c , the current flowing through the lightning arrester is
i _L is the sum of resistance current i _R and capacitance _current i _L = i _a + i _c = e ₀ /R _a sinω ₀ t + e ₀・C _a・ω ₀・cosω ₀ t ……(1) . On the other hand _{, let} the voltage _{E
Then , E X in FIG . 4 becomes E} In addition, the voltage E _S in Figure 4 is obtained by advancing the phase of the applied voltage by 90° to erase the capacitance current i _c .
If the constant of proportionality is K ₁ , then E _S =K ₁・e ₀・cosω ₀ t ……(3). Also, the initial gain of the gain control circuit GCA is G ₀
Then, the output is G ₀・E _S ……(4). Therefore _, if _{E 0 is the} output of the _differential circuit _DF in Fig _. 4, into which _E (e ₀ /R _a sinω ₀ t＋e
₀・C _a・ω ₀・cosω ₀ t) −G ₀・K ₁・C ₀・cosω ₀ t＝R _d e ₀ ／R _a sinω ₀ t＋(R _d・
C _a・ω ₀ −G ₀・K ₁ )・e ₀・cosω ₀ t……(5) To erase the current corresponding to the capacity of E ₀ ,
What is necessary is to find the gain G ₀ that satisfies R _d ·C _a ·ω ₀ −G ₀ ·K ₁ =0.

Therefore, we now convert the output E ₀ of the differential circuit DF into E _S of the equation (3) above.
The common-mode component detection circuit SD in Fig. 4 uses the reference signal as
Enter. Here, the common-mode component detection circuit SD is a circuit that outputs a DC voltage proportional to only the component in phase with the reference signal of the input signal, and the reference signal ±
It does not respond to 90° phase input components, and outputs a negative DC voltage for 180° phase components. Therefore, if the proportionality constant is K ₂ , the output E _Y is proportional to the capacitance contained in E _0. E _Y = K ₂・(R _d・C _a・ω ₀ −G ₀・K ₁ ) ……(6 ) is obtained. And this is the gain control circuit
Feedback to GCA as gain control input,
The gain control circuit GCA is set so that E _Y in the previous equation (6) becomes zero.
Automatically adjusts the gain _G0 .

For example, if the gain characteristic of the gain control circuit GCA is proportional to E _Y connected to the gain control input, then G = K ₃ · E _Y (Here, K ₃ is a proportionality constant, and G is the GCA when E _Y is input. gain), and if G ₀ in the previous equation (6) is G, then E _Y =K ₂・(R _d・C _a・ω ₀ −G ₀・K ₁ ) =K ₂・(R _d・C _a・ω ₀ −K ₃・E _Y・K ₁ ) ...(7). When E _Y is calculated from this equation (7), E _Y =R _d・K ₂・C _a・ω ₀ /1+K ₁・K ₂・K ₃ .

Therefore, if the gain of the gain control circuit GCA when the negative feedback feedback is balanced is G ₁ , then G ₁ =K ₃・E _Y =K ₃・R _d・K ₂・C _a・ω ₀ /1+K ₁・If K ₂ and K ₃ are set so _that 1≪K _{1 and} K ₂ and K ₃ , then G ₁ is G ₁ = R _d C _a and ω ₀ / K ₁ ……(8 ) becomes. Therefore, by substituting G ₁ in equation (8) for G ₀ in equation (5), R _d・C _a・ω ₀ −G ₀・K ₁ = 0 in equation (5),
The current can be erased by the capacity.

FIG. 5 is a circuit diagram of an embodiment of the present invention based on the above idea, in which L is a power line and A _r
is a lightning arrester, ID is a detector for leakage current _iL , for example, a clamp-type current transformer that can detect the current without opening the connection line of the lightning arrester _Ar , or a detection resistor inserted in series with the connection line is used, These are placed on the ground side of the arrester so as not to introduce any insulation disadvantages. A ₁ is an amplifier with high input impedance, and there is a leakage current i _L on the output side.
to obtain a proportional voltage _E. The ED uses a detector for the voltage applied to the lightning arrester, such as a winding voltage transformer or a capacitive voltage transformer. A ₂ is an amplifier with high input impedance, and φ is a phase shifter, which outputs a capacitance erasing voltage E _S that advances the phase of the output voltage of the amplifier A ₂ by 90°. GCA is a gain control circuit, such as an amplifier, to which a voltage E _S is applied, and when its initial gain is G _O , an output of G _O E _S is obtained. DF is a differential circuit, for example, a differential amplifier, to which a voltage _EX proportional to the leakage current i _L and a voltage G _O E _S from the gain control amplifier GCA are applied as inputs, and the difference between these is applied to the output side. Sends the output ( _EX −G _O・E _S ). SD
is an in-phase component detection circuit, which consists of the following parts in FIG. SR is a well-known synchronous rectifier, SS is its synchronous signal generator, such as a zero point detection circuit,
A square wave whose polarity is inverted at each cycle of the output E _S of the phase shifter φ is generated, and is added to the synchronous rectifier SR as a synchronous signal to perform synchronous rectification.
MS is an averaging circuit, e.g., an integrating circuit, which smooths the output of the synchronous rectifier SR and converts it into the differential amplifier DF.
A DC voltage _{E Y is created that is proportional to the in-phase portion of E S of the} output of ( _E The gain of the gain control amplifier GCA is controlled by the voltage E _Y to provide a balanced gain G ₁ , creating a capacitance component G _{1 ES} necessary to cancel the capacitance in _EX .

In this way, on the output side of the differential amplifier DF,
Since an output proportional to the resistance current is automatically output, for example, the output waveform or the peak value detected by a peak value detector (not shown) can be digitally processed and then digitized and displayed to prevent deterioration at any time. You can monitor the status of

An embodiment of the present invention has been described above, and in this method, a square wave whose polarity is reversed at the polarity reversal point of E _S generated by the synchronization signal generator SS is used as the synchronization signal of the synchronous rectifier SR. This in-phase component detection circuit is based on only one point of E _S. Therefore, as explained in FIGS. 2 and 3,
If the resistance current flows based on non-linear characteristics and contains harmonics, it will cause an error in cancellation, even though it is not a big problem in practice, making it difficult to accurately 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 configured by a multiplier that takes the product of the voltage E _S described above and ( _EX − G _O E _S ), which is the output of the differential amplifier DF. It is formed by MLT and averaging circuit MS.
Then, after extracting the in-phase component of E _{S of the} voltage _E By setting the DC voltage E _Y to be proportional to _S )×E _S , it is possible to eliminate errors in erasing due to synchronous rectification. Next, the experimental results will be explained.

In Fig. 7, the horizontal axis is the measurement result of the peak value of the resistance current, which was accurately measured by the conventional method by changing the flowing current for the same single zinc oxide type arrester element.
FIG. 3 is a diagram in which the vertical axis represents the measurement results obtained by the method of the present invention. In addition, Figure 8 a and b show a resistor current of 60 μA and 1 m
A is a waveform diagram of the applied voltage and resistance component current measured by the conventional method and the method of the present invention.
The waveforms are those obtained by the conventional method, and the B waveforms are those obtained according to the present invention.

From the above, according to the present invention, the peak value of the resistance current can be automatically and continuously measured over a wide current range with almost the same accuracy as conventional methods (±5% or less), and the waveform can also be measured with high precision. I understand.

Also, good results were obtained when the measuring device according to the present invention was used to measure the resistance current of a zinc oxide lightning arrester manufactured by Company A installed in each phase of the RST of a 154 KV substation of H Electric Power Co., Ltd. Figure 9 shows an example. In the figure, i _L is the leakage current, i _R is the resistance current,
P is the power loss of the lightning arrester measured based on the resistance current.

As is clear from the above description, according to the present invention, the resistance current required for deterioration determination of lightning arresters such as zinc oxide type surge arresters and SiS surge arresters, which include capacitance current in leakage current, can be calculated without the need for troublesome operations. This can be obtained automatically without having to do anything, and will greatly contribute to the realization of an automatic deterioration detection device for lightning arresters, and furthermore, to the realization of a constant monitoring system.

[Brief explanation of drawings]

Fig. 1 is an equivalent circuit of a lightning arrester, such as a zinc oxide type arrester, whose leakage current includes a capacitance, Figs. 2 and 3 are illustrations of leakage current waveforms, and Fig. 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, FIG. 6 is a partial circuit diagram showing another example of the common-mode component detection circuit, and FIGS. 7, 8, and 9 are explanatory diagrams of experimental results. It is. L...power line, A _r ...surge arrester, ID...leakage current detector, _A1 ...amplifier, ED...applied voltage detector for lightning arrester, _A2 ...amplifier, φ...phase shifter,
GCA...Gain control circuit, (amplifier), DF...Differential circuit (amplifier), SD...Common mode component detection circuit, SR
...Synchronous rectifier, SS...Synchronous signal generator, MLT
...Multiplier, MS...Averaging circuit.

Claims (1)

[Claims] 1 Add a voltage E _X proportional to the leakage current of the arrester and a voltage E _S that is in phase with the capacitance current in the arrester leakage current to the differential circuit via the gain control circuit,
The output is added to a circuit that detects a DC voltage proportional to the in-phase component of the _{voltage E} A method for automatically detecting a resistance current in a lightning arrester, characterized by automatically detecting only the resistance current output from the leakage current by erasing the capacitance.