JPH067722B2 - Gas insulation switchgear ground fault detector - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a ground fault detector of a gas insulated switchgear.

[Technical background of the invention] As a means for detecting a ground fault in a gas-insulated switchgear, a sealed case connected to a casing of the switchgear via a communication pipe is provided, and a micro switch or the like is provided inside the case. It is known that a detection switch and a float that floats due to an increase in pressure at the time of a ground fault are provided, and the floating switch moves the detection switch to display a failure.

However, in this type of detector, as the amount of gas in the switchgear that communicates with the case increases, the detection sensitivity decreases because the pressure rise value due to a ground fault becomes smaller, and due to pressure rises other than ground faults, Also has the problem of malfunction.

This point will be specifically described with the conventional ground fault detector shown in FIG.

In FIG. 1, 11 is a gas-insulated switchgear in which a high-voltage charging part is incorporated in an outer casing filled with insulating gas, 12 is a switch case of a detector, and the switchgear 11 and a communication pipe 13 are provided at the bottom thereof. It has a gas introduction hole 14 connected through it, and inside thereof is a gas chamber 17 provided with a cylinder 15 and a detection switch 16 such as a micro switch. Cylinder 1
5 is vertically installed on the bottom surface of the switch case 12, the lower opening side thereof communicates with the gas introduction hole 14, and the upper portion communicates with the gas chamber 17 through the through hole 19 of the end plate 18.
The detection switch 16 is fixed to an extension of the end plate 18. A float 20 having a protrusion 21 is movably provided in the cylinder 15.

In such a detector, when the gas insulated switchgear is in operation, the gas chamber 17 of the switch case 12 has the switchgear 11
Insulating gas from is introduced through the communication pipe 13, the gas introduction hole 14, and the cylinder 15, and is maintained at a steady pressure. now,
When a ground fault occurs in the switchgear 11, the internal pressure of its jacket rises, and the float 20 floats due to the pressure difference between the pressure transmitted to the cylinder 15 and the pressure in the gas chamber 17 of the switch case, The detection switch 16 is operated via the protrusion 21. The detection switch 16 opens and closes a detection circuit (not shown) to display a failure.

[Problems of background art] However, with such a configuration, when the gas amount of the gas insulated switchgear 11 is large or when the ground fault current is small, the pressure rise value becomes small and the detection sensitivity becomes a problem. Become. In particular, when there is almost no difference between the pressure increase value due to the ground fault current and the pressure increase value due to other factors (for example, temperature fluctuation), the detector may malfunction.

[Object of the Invention] The present invention has been made in view of the above points, and a ground fault of a gas-insulated switchgear capable of reliably detecting a ground fault without operating against a pressure increase due to a factor other than a ground fault. A detector is provided.

[Summary of the Invention] In a ground fault detector for a gas insulated switchgear according to the present invention, a cylinder connected to the communication pipe is provided in a switch case connected to the gas insulated switchgear via a communication pipe. A float that floats when the gas pressure of the gas-insulated switchgear rises is provided, and two pressure switches with different operating pressure values are linked to this float. Whether the pressure rises due to a ground fault or another factor from the operating time difference between these pressure switches. It is to discriminate.

Embodiments of the Invention Embodiments of the present invention will be described below with reference to the drawings. The same members as those of the conventional type shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

FIG. 2 shows the first embodiment of the present invention. In the present embodiment, a pair of pressure switches 16a and 16b, which are operated by the floating of the float 20 through the protrusion 21, are provided in the same gas chamber 17. It is installed in. These pressure switches 1
6a and 16b are set to different operating pressure values as shown by ΔP ₁ and ΔP ₂ in FIG. 3, respectively. Each pressure switch 16a, 16b is connected to a circuit for determining the presence or absence of a ground fault from the output waveform of the pressure switch as shown in FIG. 4 as an example. That is, the pressure switch 16a having a low operating pressure value ΔP ₁ is connected to the synthetic amplifier Amp via the delay circuit Q having the delay time ΔT, and the pressure switch 16b having a high operating pressure value ΔP ₂ is directly connected to the synthetic amplifier Amp. ing. In the circuit of FIG. 4, when the first pressure switch 16a operates at ΔP ₁ of FIG. 3, a step wave having a peak value of −1 and the second pressure switch 16b at ΔP ₂ of FIG. When operated, a step wave having a crest value of +1 with the opposite sign to the above is generated. First pressure switch 1
The output of 6a is the maximum value ΔT (t _{2 in} FIG. 3) of the pressure rise time due to the ground fault in the delay circuit Q, which is calculated.
It is delayed by the maximum value of −t ₁ ) and is combined with the output of the second pressure switch 16b in the combining amplifier Amp.
Now, due to the pressure rise from the gas insulated switchgear, float 2
0 floats and the first and second pressure switches 16a, 16b
When the operation time difference between the first pressure switch 16a and the second pressure switch 16b is T, when T <ΔT, as shown in FIG. , T> ΔT or the second pressure switch 16b
When is not operating, a negative pulse is output to the output of the synthetic amplifier, and the ground fault can be detected. In this case, the pressure rise time during ground fault _(t 2 -t ₁₎ is several tens of m
s on the order of, significantly shorter than the other factors (e.g., ambient temperature changes, etc.) due to pressure rise time _{(t 4 -t 3) [(} t 2 -t 1) << (t 4 -t 3)] Therefore, such discrimination is easy. Further, in terms of circuitry, it is extremely easy to construct a circuit as shown in FIG.

In the embodiment shown in FIG. 2, two pressure switches are attached to one cylinder, but as shown in FIG. 5, two cylinders 15a and 15b are provided in the same gas chamber, and pressure switches 16a and 16b are provided respectively. 1 may be installed, or two conventional detectors shown in FIG. 1 are installed close to the communicating pipe 13 and the pressure switch operating values of each are set differently as shown in FIG. You may stay.

[Effects of the Invention] As described above, according to the present invention, there is provided a ground fault detector of a gas insulated switchgear capable of reliably detecting a ground fault without causing malfunctions due to pressure fluctuations due to factors other than a ground fault. It becomes possible to provide.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a conventional ground fault detector, FIG. 2 is a sectional view of a first embodiment of the present invention, and FIG. 3 is first and second portions of a ground fault detector of the present invention. 4 is a graph showing the operating pressure value and pressure rise time of the switch of FIG. 4, FIG. 4 is a diagram showing the configuration and operation of the circuit connected to each switch of the embodiment of FIG. 2, and FIG.
The drawing is a cross-sectional view showing a second embodiment of the present invention. 11 ... Gas-insulated switchgear, 12 ... Switch case, 13
... communication pipe, 14 ... gas introduction hole, 15 ... cylinder, 16,
16a, 16b ... Detection switch, 17 ... Gas chamber, 18 ...
End plate, 19 ... Through hole, 20a, 20b ... Float, 21
a, 21b ... a stem.

Claims (2)

[Claims] 1. A cylinder connected to the communication pipe is provided in a switch case connected to the gas insulated switchgear via a communication pipe, and a float that floats up due to a rise in gas pressure of the gas insulated switchgear is provided in the cylinder. , A first pressure switch and a second pressure switch operating at different operating pressure values are interlocked with this float, and the output signal of the first pressure switch is used to indicate the pressure rise time at the time of a ground fault of the gas insulated switchgear. A delay circuit for delaying the maximum value ΔT is provided, and the output signal of this delay circuit is combined with the output signal of the second pressure switch whose sign is opposite to that of the first pressure switch, and the sign of this combined signal A ground fault detector for a gas-insulated switchgear, comprising means for determining whether a ground fault has occurred or a pressure increase due to another factor. 2. A gas-insulated switch according to claim 1, wherein the first and second pressure switches are respectively connected to floats in two cylinders provided in the same gas chamber. Device ground fault detector.