JPS6133385B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the grounding of an insulating bolt, and particularly to a method for detecting the grounding of an insulating bolt used to mechanically connect mutually insulated sheaths of a gas-insulated switchgear in an operating state. The present invention relates to a ground detection method suitable for ground detection.

First, the conventional technology will be explained with reference to FIG. 1, which shows one embodiment of the present invention. Figure 1 is an explanatory diagram of the structure of a part of a bushing through-type current transformer (hereinafter abbreviated as BCT) of a gas-insulated switchgear equipped with a one-turn prevention device. The upper sheath 1 is surrounded by an insulator 5 for preventing the damage, and the upper sheath 1 is assembled to the lower sheath 2 via an insulating spacer 6 using bolts 7. Incidentally, since both the upper sheath 1 and the lower sheath 2 are grounded, in order to prevent one turn from being formed, the bolt 7 electrically and mechanically connected to the lower sheath 2 is connected to the insulating washer 8. , and is electrically insulated from the upper sheath 1 using an insulating tube 9. However, in the past, the insulation state of the bolt 7 with respect to the upper sheath 1 deteriorated for some reason, and the bolt 7 electrically contacted the upper sheath 1, forming one turn, and a normal secondary current was applied to the BCT 4. If an accident occurs in which the flow stops, the insulation condition of the bolts 7 cannot be checked using a tester or the like because both the upper sheath 1 and the lower sheath 2 are grounded. I pulled it out and checked whether the insulation was good or not. However, in this method, since the number of bolts 7 is large, a large amount of time is required for checking.Therefore, it has been desired to develop a method that can detect the quality of the insulation of the bolts 7 while the motor is in operation.

The present invention has been made in view of the above, and its purpose is to detect the grounding of an insulating bolt that mechanically connects sheaths that are both grounded via an electrical insulator during operation. The object of the present invention is to provide a method for detecting the grounding of an insulating bolt.

The feature of the present invention is that a pulse voltage is applied from an oscillator between an insulating bolt and a sheath to which this insulating bolt is attached in an insulating state, and a current transformer is provided.
An abnormality in the insulation between the insulating bolt and sheath, that is, in the grounding state of the insulating bolt, is detected from changes in the secondary current due to changes in the induced voltage due to the current flowing between the insulating bolt and sheath of this current transformer. It is in the point that I made it.

An embodiment of the method of the present invention will be described in detail below with reference to FIGS. 1 to 5.

FIG. 1 is a structural explanatory diagram of a one-turn prevention portion of a BCT of a gas insulated switchgear for explaining one embodiment of the method of the present invention, and also includes an insulating bolt grounding detection device. In Figure 1, 1 is an upper sheath, 2 is a lower sheath, 3 is a protective cover, and 4 is a
BCT, 5 is an insulator, 6 is an insulating spacer, 7 is an insulating bolt having an insulating washer 8 and an insulating tube 9, and since these have already been described above, their explanation will be omitted here.

By the way, in the present invention, when detecting the presence or absence of insulation of the insulating bolt 7 with respect to the upper sheath 1, that is, the grounding state of the insulating bolt 7, an oscillator 10 is provided, and the insulating bolt 7 and the insulating bolt 7 detecting the grounding state from the oscillator 10 are provided. When a pulse voltage is applied between the upper sheath 1 and the impedance between the insulating bolt 7 and the upper sheath 1 changes, that is, the grounding state of the insulating bolt 7, when a current flows between the insulating bolt and the upper sheath 1, the impedance changes between the insulating bolt 7 and the upper sheath 1. , the current flowing through the ground changes,
As a result, the secondary current of the BCT 4 changes, so this change is measured at the secondary terminal 16.

Figure 2 is a diagram showing the experimental results of the relationship between the insulation state of the insulating bolt and the induced voltage of BCT4.
6 was measured using a peak voltmeter with an input impedance of 10 kΩ. A is insulation bolt 7
This is the result when the is forcibly brought into contact with the upper sheath 1, B and C are the results of the insulating bolt that is close to the other normal insulating bolts and the insulating bolt that is far apart. The induced voltage is significantly smaller than in B and C. Therefore, it can be seen from this that the insulating bolt 7 having poor insulation can be easily detected in the operating state. According to this method, even if there are a large number of insulating bolts 7, the grounding state of the insulating bolts 7 can be detected in the assembled state, so the detection can be performed in a short time, and labor costs can be significantly reduced.

FIG. 3 is a circuit diagram showing an embodiment of the oscillator 10 shown in FIG. 1, and in FIG.
2 is a switch, 13 and 14 are timer relays, 13
a is the normally open contact of the timer relay, 14b is the normally closed contact of the timer relay 14, and 14a is the timer relay 14
The normally open contact 15 is a DC power supply, and these are connected as shown in the figure. When switch 12 is closed,
After a predetermined time period, the timer 13 turns on and its contact 1
3a is closed, and after a predetermined time period, timer relay 1
4 is turned on, its contact 14a is closed and a voltage is generated on the output side, and its contact 14b is opened and timer relay 13 is turned off. When the timer relay 13 is turned off, the contact 13a is opened and the timer relay 14 is turned off, the contact 14a is opened and voltage supply to the output side is stopped, and the contact 14b is closed to return to the original state. Repeat this switching action. Therefore, by providing timer relays 13 and 14 with appropriate time limits, a third
A pulse voltage as shown in the figure can be obtained.

As described above, according to the embodiment of the present invention, the insulation of the insulating bolt 7 with respect to the upper sheath 1, that is, the grounding state can be easily detected in the mounted state, so that the detection time can be shortened and the labor cost can be significantly reduced. can be reduced to

In addition, in the above, BCT4 of gas insulated switchgear
The method for detecting the grounding of the insulating bolt 7 to prevent one turn of are insulated via the insulating spacer 25, the sheaths 17 and 18 are fixed to the insulating spacer 19 using insulating bolts 26 and 27, respectively, but in this case also, in the same manner as above, Insulating bolts 26, 27
and the sheaths 17, 18 can be detected. In Fig. 5, 16 is a disconnector, 17 is a current transformer, 18 is a wire breaker, 19 is a current transformer, 20 is a grounding switch, 21 is a current transformer for ground fault detection, and 22 is a grounding switch. It is a terminal. In addition, in Figure 1, BCT4 was used as a current transformer for grounding detection, but BCT
When 4 is not in use, prepare and use a separate current transformer for measurement.

As explained above, according to the present invention, it is possible to detect the insulation between the insulating bolt and the sheath, which mechanically connect the sheaths, which are both grounded, via an electrical insulator, in other words, the grounding state in the mounted state. This has the effect of shortening the time for ground detection and significantly reducing personnel costs.

[Brief explanation of the drawing]

FIG. 1 is a structural explanatory diagram of a one-turn prevention part of a BCT of a gas insulated switchgear including an insulating bolt detection device for explaining an embodiment of the method of the present invention;
Figure 2 is a diagram showing the experimental results of the relationship between the insulation state of the insulating bolt and the induced voltage to the BCT, Figure 3 is a circuit diagram showing an example of the oscillator in Figure 1, and Figure 4 is the 5 and 6 are diagrams showing other application examples of the method of the present invention, and FIG. 5 is a partial explanatory diagram of a skeleton of a compact substation, and FIG. This figure is a sectional view for explaining the insulation structure between the sheaths in the case of FIG. 5. 1... Upper sheath, 2... Lower sheath, 4...
BCT, 6... Insulating spacer, 7... Insulating bolt, 8... Insulating washer, 9... Insulating tube,
10...Oscillator, 16...BCT secondary terminal.

Claims (1)

[Claims] 1. When detecting the insulation between the sheath and an insulating bolt that mechanically connects the sheaths, which are both grounded, via an electrical insulator, the insulation between the insulating bolt and the sheath is detected. A pulse voltage is applied from an oscillator, and a current transformer is provided, and the quality of the insulation is detected from a change in secondary current caused by a change in induced voltage due to a current flowing between the insulating bolt and the sheath of the current transformer. A method for detecting grounding of an insulating bolt, characterized by: 2. The method for detecting grounding of an insulating bolt according to claim 1, wherein the sheath is a sheath of a gas insulated switchgear, and the current transformer is a bushing through type current transformer of the gas insulated switchgear.