JPH0545400A - Insulation deterioration diagnosis method for power equipment - Google Patents

Abstract

(57) [Summary] [Purpose] An improved insulation deterioration diagnosis method capable of accurately measuring the insulation state of a multi-circuit switch for distribution in an operating state. [Composition] In a distribution multi-circuit switch in operation, the corona discharge generated is detected by observing the current flowing from the shielding layer of the cable drawn into the distribution multi-circuit switch to the cable ground wire. , The insulation state of the multi-circuit switch for distribution is examined by analyzing the detected signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a non-destructive and highly accurate probability of the degree of insulation deterioration of a multi-circuit switch, which is a power device whose housing is directly grounded. The present invention relates to a novel insulation deterioration determination method that can be determined with.

[0002]

2. Description of the Related Art When insulation deterioration occurs in an aerial multi-circuit switch, which is a device for high-voltage power, partial discharge occurs in the deteriorated part (electrode part). Conventionally, this partial discharge has been conventionally observed and diagnosed by detecting the electromagnetic waves generated by the partial discharge at each of the three electrode portions of each phase of each circuit by an antenna.

[0003]

According to the above-mentioned conventional method, in order to measure the whole of the multi-circuit switch for distribution, for example, 5 circuits and 3 phases, it is necessary to measure with respect to 45 antennas, and the whole is measured. It was very laborious and time-consuming to do.

The present invention has been made in view of the above circumstances, and solves the above-mentioned problems of the prior art, reliably measures partial discharge in an operating state, and as a result, diagnoses the insulation state with high accuracy. It is an object of the present invention to provide an improved insulation deterioration diagnosing method for electric power equipment.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, corona discharge generated in an operating distribution multi-circuit switch is corroded from a shielding layer of the cable drawn into the distribution multi-circuit switch to ground the cable. This is a method of detecting the current flowing through the line, and analyzing the detected signal to check the insulation state of the device.

The present invention also provides, as a signal analysis method, a method of diagnosing insulation deterioration of electric power equipment, characterized by examining the insulation state of a multi-circuit switch for distribution by performing frequency analysis on the signal in the range of 1 MHz to 1 GHz. Is.

[0007]

[Function] Since the electrodes of each circuit are connected in the fixed electrode and further connected to the conductor of the lead-in cable,
When corona discharge occurs in the electrode, it is considered that the signal reaches the cable shielding layer from the cable conductor through the cable insulator. Then, the signal can be detected.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle of this method will be described below with reference to FIG. FIG. 1 is a schematic diagram of a measuring method showing a case of measuring a ground line of an R phase 5 circuit. That is, five movable electrode portions 2 are provided in the multi-circuit switch housing 1. Then, a penetrating current transformer (CT) 5 is arranged on the cable ground wire 4 of the lead-in cable 3 connected to the five movable electrode portions 2.
The signal line 11 sends a signal to the spectrum analyzer 13 via the amplifier 12 to detect the frequency component. The output from the spectrum analyzer 13 is input to the computer 14 and stored therein.

The equivalent circuit of FIG. 1 is shown in FIG. For example, an epoxy connection portion 6a connected to the electrode portion 2a of the third circuit
In the case where it is deteriorated to become a partial discharge generation part, corona discharge is generated in the electrode part 2a and electric charges are discharged, so that pulsed noise (signal) is generated in the power supply line. Cable 3 that passes through the bus of this signal electrode
Up to the cable conductor 7. Since this signal generated by the partial discharge has a high frequency component, it reaches the cable shielding layer 3'from the cable conductor 7 through the cable insulating material (high-resistance conductive rubber) 8 by capacitive coupling. The cable grounding wire 4 is connected to the cable shielding layer 3 ', and the partial discharge signal eventually falls to the ground. Therefore, the partial discharge detection method according to the present invention is to observe the state of partial discharge by observing the current flowing through the cable ground wire 4 by using the through current transformer (CT) 5.

In such an aerial multi-circuit switch,
If water enters the housing 1 during the operation and further water enters the inside of the epoxy electrode 6, a minute corona discharge will start from the inside of the electrode due to long-term charging. Then, with the passage of time, this corona discharge develops into glow discharge, scintillation, and tracking, and eventually into dielectric breakdown of the epoxy electrode portion 6. In this way, corona discharge is always generated in the process from the generation of corona discharge to the dielectric breakdown, so that the signal from the penetrating current transformer (CT) 5 is always observed, and each signal has its own characteristic in each process. This has been found based on the results of earnest research by the present inventors.

In particular, as a result of frequency analysis of the current signal using a spectrum analyzer, the frequency component of the current (measured using CT) flowing in the cable ground wire at the time of occurrence of micro corona discharge immediately after the start of deterioration is Several tens of MHz
It was found that the frequency component spreads from the high frequency side to the low frequency side as the deterioration progresses to glow discharge, scintillation, and tracking, while it is relatively biased to the high frequency side of several GHz. . For example, when tracking starts, the frequency band of the current is 10 kHz.
It became clear that the frequency component spreads up to several GHz and reaches 10 kHz.

FIGS. 3 and 4 show graphs of measurement examples measured using this method. That is, FIG. 3 (A), (B)
Shows the result of measurement in a laboratory for a multi-circuit switch whose deterioration has progressed. From this result, it can be seen that the frequency band of the partial discharge signal observed in the deteriorated multi-circuit switch extends to the low frequency side of the order of 10 kHz.

On the other hand, FIGS. 4 (A) and 4 (B) show measurement results of external noise components measured in a sound multi-circuit switch actually installed in the field. From this result, 1MHz
Very large external noise is observed in the following frequency bands.

From the measurement results shown in FIG. 3 and FIG. 4, it is considered difficult to discriminate between the external noise and the deteriorated signal in the frequency band of 1 MHz or less when actually measuring at the site. Therefore, it is considered that the frequency band used for actual observation (deterioration diagnosis) is preferably 1 MHz or more.

On the other hand, since the detected signal itself becomes small in a high frequency band of 1 GHz or more, it is not appropriate to use this for deterioration diagnosis.

From the above results, it is considered that the insulation degradation diagnosis method of the present invention is most effective in measuring in the frequency range of 1 MHz to 1 GHz.

Table 1 shows the results of examining five examples of the multi-circuit switch in operation, which have different insulation deteriorations. That is, after measuring and analyzing the cable grounding wire current, the multi-circuit switch is removed from the site, and the insulation discharge diagnosis method of the present invention and the conventional partial discharge detection device are used to measure the partial discharge charge and the epoxy electrode. It shows the results of an investigation on the details of the surface.

[0018]

[Table 1]

As is clear from Table 1, when a partial discharge is detected from the multi-circuit switch, a signal is observed on the cable ground wire and a discharge mark is formed on the surface of the epoxy electrode.

In the above example, the other circuit switch for distribution is explained, but in this deterioration diagnosis method, for example, a cable such as a π-coupling high-voltage cabinet is connected, and the cable ground is common with the case ground. Of course, it can be similarly applied to such power equipment.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an insulation deterioration diagnosing method for electric power equipment of the present invention,

2 is an equivalent circuit diagram of FIG.

3A and 3B are graphs showing signal measurement examples,

4A and 4B are graphs showing an example of noise measurement.

[Explanation of symbols]

 1 Multi-circuit switch housing 2 Movable electrode part 3 Lead-in cable 4 Cable ground wire 5 Penetration type current transformer (CT) 6 Epoxy connection part 7 Cable conductor 8 Cable insulator 11 Signal line 13 Spectrum analyzer 14 Computer

Claims (2)

[Claims] 1. A corona discharge generated in an operating power distribution multi-circuit switch is monitored by observing a current flowing from a shielding layer of the cable drawn into the power distribution multi-circuit switch to a ground line of the cable. A method for diagnosing insulation deterioration of electric power equipment, characterized in that the insulation state of a power distribution multi-circuit switch is investigated by analyzing the detected signal. 2. The signal analysis method according to claim 1, wherein the insulation state of the power distribution multi-circuit switch is examined by performing frequency analysis on the signal in the range of 1 MHz to 1 GHz. Diagnostic method.