JPH04262273A - Zinc oxide type lightning arrester monitor - Google Patents

Abstract

PURPOSE:To exctly measure the leak current from a zinc oxide type arrester changing in a wide range and perform control and maintainance etc., easily. CONSTITUTION:A leak current signal from a zinc oxide type arrester 1 which is amplified with a proper amplification gain and its gain signal indicating the amplifiaction gain, are duplicated and sent to a monitoring point. The sent leak current signal and gain signal are separated and extracted to calculate a leak current value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc oxide lightning arrester monitoring device that detects deterioration of zinc oxide lightning arresters at an early stage.

0002

2. Description of the Related Art Definitions of abbreviations used in this specification are listed below. MOA: Zinc oxide lightning arrester CT: Current transformer MPX: Multiplexer BPF: Bandpass filter S/N: Signal-to-noise I/V: Current-voltage (conversion) V/F: Voltage-frequency (conversion) E/O: Electricity-optical (conversion) O/E: Optical-electrical (conversion) F/V: Frequency-voltage (conversion) PLL: Phase-locked loop A/D: Analog-digital (conversion)

0003
Since leakage current increases when the MOA deteriorates, the deterioration of the MOA has been detected by measuring this leakage current. FIG. 2 shows a conventional zinc oxide type lightning arrester monitoring device disclosed in Japanese Unexamined Patent Publication No. 2-123688. The leakage current of the MOA (1) measured by the CT (2) is subjected to voltage conversion, frequency conversion and electro-optical conversion to a data processing device installed remotely via optical fiber (13) from the sensor box (22'). (19'). Data processing device (19)
performs optical-to-electrical conversion on optical signals from a plurality of MOAs, and then processes each signal from each MOA using the built-in MPX (20). The output of the MPX (20) is subjected to frequency-voltage conversion and input to the BPF (5) to extract a leakage current signal, and then input to the synchronous rectifier (10). To be precise, this leakage current signal includes a sine wave component of the current flowing through the power transmission line (50). In contrast, an isolation transformer (6
), the data processing device (19') is connected to the power transmission line, and the sine wave component of the power transmission line (50) is converted to a predetermined level, harmonic components are removed, and the power transmission line is adjusted to a predetermined phase. The signal is input to the synchronous rectifier (10) as a signal. In this synchronous rectifier (10), the sinusoidal wave components of both signals are canceled to obtain a leakage current value. This leakage current value is A
/D conversion, the microcomputer (17) determines whether or not it exceeds a predetermined value, and if it exceeds the predetermined value, a display device (18) indicates that the MOA is abnormal.
will be displayed.

0004

The leakage current measured as described above has a difference of several tens of times between the initial value when the MOA is normal and the final value when the MOA is determined to be abnormal. In addition, the initial value differs significantly for each MOA depending on the voltage range and capacity used. For this reason, the zinc oxide type lightning arrester monitoring device is required to accurately measure leakage current over a very wide detection range. However, the amplification factor of the detection signal in the circuit in the sensor box (22') is fixed.
When adjustments are made to optimally measure up to the terminal value for each OA, it is difficult to accurately measure the initial value at normal times. Specifically, there were problems in accurate measurement due to a decrease in the S/N ratio, a decrease in resolution of A/D conversion, and the like. Furthermore, adjusting and setting the amplification factor for each MOA as described above is time-consuming and complicated in terms of management and maintenance.

[0005] This invention was made to solve the above problems, and it is possible to accurately detect MO over a wide detection range.
It is an object of the present invention to provide a zinc oxide type lightning arrester monitoring device that can measure the leakage current of A and can also be easily adjusted, managed, and maintained.

[0006]

[Means for Solving the Problems] A zinc oxide type lightning arrester monitoring device according to the present invention includes leakage current detection means connected to a zinc oxide type lightning arrester, and detects the level of leakage current detected by the leakage current detection means. gain setting means for setting an appropriate amplification gain for the leakage current; an amplifier for amplifying the leakage current with the amplification gain set by the gain setting means; a signal representing the amplification gain set by the gain setting means; and a signal amplified by the amplifier. A transmitting means for multiplexing leakage current as a gain signal and a leakage current signal and transmitting the same; a separating and extracting means for separately extracting the gain signal and the leakage current signal from the signal transmitted by the transmitting means; and the gain signal and the leakage current signal. A calculation means for calculating a leakage current value from the current signal is provided.

[0007]

[Operation] In the zinc oxide type lightning arrester monitoring device of the present invention, the gain setting means sets an appropriate amplification gain for the detected leakage current of the zinc oxide type lightning arrester, and the leakage current is amplified by the set amplification gain. A transmitting means multiplexes and transmits a current signal and a gain signal representing its amplification gain. The leakage current signal and the gain signal are separated and extracted from the transmitted signal by the separation and extraction means, and are calculated by the calculation means to obtain a leakage current value.

[0008]

1 and 2 showing block diagrams of an embodiment of the present invention. A CT (2) connected to a sensor box (22) detects a leakage current of an MOA (1) connected between a power transmission line (50) and ground. Inside the sensor box (22), the I/V converter (3) converts the leakage current into a voltage signal. A comparator (41) detects the level of this voltage signal, and an amplifier (41) is used to amplify the leakage current to the optimal signal level for the monitoring device.
43) outputs a gain designation signal that designates an appropriate gain. This gain designation signal is input to a gain switch (42) and a gain signal generator (44). Amplifier (43
) amplifies the voltage signal from the I/V converter (3) with an appropriate gain selected by the gain switch (42). At the same time, the gain signal generator (44) generates a voltage signal proportional to the gain specified by the comparator (41). Note that it is practically sufficient for the gain specified by the gain designation signal to be switched stepwise as necessary, and it is not necessary to switch it continuously. Further, since the AC waveform of the commercial frequency is input to the comparator (41), it is desirable that the comparator (41) has an output holding function for a period slightly longer than one cycle of the commercial frequency.

The clock circuit (45) outputs a pulse signal at an appropriate sampling time, and the shift register (46) outputs a pulse signal at an appropriate sampling time.
), and the V/F conversion circuit for leakage current signal (4
7) The gain signal V/F conversion circuit (48) and the synchronization signal pulse width shaping circuit (49) are sequentially operated in a time-sharing manner. That is, a pulse signal representing a leakage current signal, a pulse signal representing a gain signal, and a pulse signal representing a synchronization signal are generated. In the next logical OR circuit (51),
These signals are logically summed and multiplexed to form one pulse signal. Next E/O converter (
32) converts the pulse signal into an optical pulse signal and transmits it from the sensor box (22) to the upper data processing device via the optical fiber (13).

In the data processing device (19), the optical pulse signals transmitted from the plurality of sensor boxes are transmitted to the O/E converter (34).
)(34)..., the pulse signal is restored to the original pulse signal. This pulse signal is input to MPX (20). The MPX (20) switches inputs from a plurality of sensor boxes in a predetermined order. During the output of this MPX (20), MO
A leakage current signal, gain signal, and synchronization signal are included. Among these, the synchronization signal is detected by the PLL circuit (52), and the shift register (53) is operated in synchronization with the synchronization signal. By this synchronous operation, the pulse signal of the leakage current signal is converted into a voltage signal in the leakage current signal F/V conversion circuit (54). Also F/V for gain signal
The conversion circuit (55) converts the pulse signal representing the gain signal into a voltage signal.

A signal containing a leakage current of an appropriate frequency is extracted from the voltage signal of the leakage current signal inputted to the BPF (5) and inputted to the synchronous rectifier (10). To be precise, this leakage current signal includes a sine wave component of the current flowing through the power transmission line (50), so the sine wave component is removed by the following processing. The voltage of the power transmission line (50) is further input to the data processing device (19) via an isolation transformer (6), and after being converted to a predetermined level by a level conversion circuit (7), it is converted to a predetermined level by a BPF (8). A sine wave component of the current flowing through the power transmission line (50) from which harmonic components have been removed is input to the waveform adjustment section (9). This sine wave component is made into a predetermined phase by the waveform adjustment section (9), and then the synchronous rectification section (
10). In this synchronous rectifier (10), the sine wave component included in the leakage current signal and the above sine wave component are canceled out, and only the leakage current component that does not include the sine wave component is obtained.

This leakage current component is inputted to the A/D converter (16) via the MPX (21), and then inputted to the microcomputer (17) as a digital signal representing the leakage current component. On the other hand, the gain signal output from the F/V conversion circuit (55) also passes through the MPX (21) to the A/D converter (16).
) and is input to the microcomputer (17) as a digital signal representing the gain. A microcomputer (17
) performs arithmetic processing to obtain accurate leakage current values. Similarly, the effective signal of the leakage current signal that has been full-wave rectified by the full-wave rectifier (4) is also input to the A/D converter (16) via the MPX (21), digitized, and converted into a digital signal. is input into the microcomputer (17) as follows. A microcomputer (17) calculates an effective signal and a gain signal of the leakage current signal to obtain an accurate effective value of the leakage current. The microcomputer (17) stores data such as preset leakage current values, and when the calculated leakage current exceeds a predetermined value, it is determined that an abnormality has occurred in the MOA, and the display device (18) indicates the appropriate value. Display. Note that the above MPXs (20), (21) and (22) are controlled by a microcomputer (17). As described above, in this device, the leakage current of the MOA is always amplified with the optimum gain, so various MOAs with different leakage currents can be used.
This is reasonable because the same device can be applied to OA as well.

[0013]

[Effects of the Invention] As described above, according to the present invention, the widely varying leakage current of a zinc oxide lightning arrester is amplified with an appropriate amplification gain, and the gain signal representing the amplification gain and the amplified leakage current signal are multiplexed. and sent to the monitoring point. Since the transmitted gain signal and leakage current signal are each separated and extracted and then calculated by the calculation means, it is possible to accurately determine the leakage current value that changes over a wide range. Semi-fixed adjustment, setting,
There is no need for management etc.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a zinc oxide lightning arrester monitoring device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a zinc oxide lightning arrester monitoring device according to an embodiment of the present invention (a diagram showing details of the data processing device (19) shown in FIG. 1).

FIG. 3 is a block diagram showing a conventional zinc oxide lightning arrester monitoring device.

[Explanation of symbols]

1 Zinc oxide lightning arrester 2 CT 10 Synchronous rectifier 16 A/D converter 17 Microcomputer 41 Comparator 42 Gain switch 43 Amplifier 44 Gain signal generator 45 Clock circuit 46 Shift registers 47, 48 V/F conversion circuit 49 Synchronization signal Pulse width shaping circuit 51 Logic OR circuit 52 PLL circuit 53 Shift registers 54, 55 F/V conversion circuit

Claims (1)

[Claims] 1. Leakage current detection means connected to a zinc oxide type lightning arrester, gain setting means for detecting the level of leakage current detected by the leakage current detection means and setting an appropriate amplification gain for the leakage current, and said gain. an amplifier that amplifies the leakage current with an amplification gain set by the setting means; a signal representing the amplification gain set by the gain setting means; and a leakage current amplified by the amplifier, each multiplexed and transmitted as a gain signal and a leakage current signal. An oxidizing device comprising a transmitting means, a separating and extracting means for separately extracting the gain signal and the leakage current signal from the signal transmitted by the transmitting means, and a calculating means for calculating a leakage current value from the gain signal and the leakage current signal. Zinc type lightning arrester monitoring device.