JP3146472B2 - Failure detection device for gas insulated electrical equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas-insulated electrical device for detecting a fault when a ground fault or a short-circuit fault occurs inside the device, such as a gas-insulated switchgear or a gas-insulated transformer. The present invention relates to a failure detection device.

[0002]

2. Description of the Related Art In general, a gas insulated switchgear is formed by accommodating a device such as a circuit breaker or a disconnector in a metal container and sealing an insulating gas such as sulfur hexafluoride gas at a certain pressure. It is excellent in miniaturization, high reliability and safety. However, if a ground fault or short circuit fault occurs inside the gas-insulated switchgear, the gas-insulated switchgear has a sealed structure, so it is not possible to visually confirm that the fault has occurred from the outside. Have difficulty.
For this reason, when a ground fault or short circuit fault occurs, the gas pressure of the insulating gas increases due to the fault arc energy, and a fault of the gas insulated switchgear may be detected by detecting this pressure increase. In this failure detection device, a pressure sensor is conventionally provided in a gas insulated switchgear, and the pressure sensor measures the pressure value of the insulating gas. Then, a pressure rise value is obtained from a difference between the pressure instantaneous value which is the output of the pressure sensor and the sealed pressure value, and when the pressure rise value exceeds a preset monitoring value, it is determined that a failure has occurred. ing.

[0003] Further, in a gas insulated switchgear, the inside thereof is usually divided into a plurality of gas compartments such as a breaker gas compartment and a disconnector gas compartment, and a failure occurs from the viewpoint of stable power supply. It is necessary to quickly restore a healthy gas section other than the gas section and that does not hinder the application of voltage, and to shorten the power outage time. Therefore, in order to detect a faulty partition, a faulty partition detection device may be used, and the output of the faulty detection device is also used as one input of the faulty partition detection device.

[0004]

The above-mentioned conventional fault detecting device has the following problems. The pressure value of the insulating gas when a failure occurs is a pressure value obtained by adding the pressure increase due to the failure to the above-described sealed pressure value. For this reason, the pressure rise value due to the failure is determined by subtracting the sealed pressure value from the pressure value measured by the pressure sensor. However, the pressure rise value due to the failure is related to the gas volume of the gas-insulated electrical equipment and the arc energy of the failure.If the gas volume of the gas-insulated electrical equipment is large or the failure arc energy is small such as a ground fault, The pressure rise value is very small, for example, a minute pressure rise value that is several thousandths or less of the sealed pressure value. Therefore, when the pressure value including the sealed pressure value is measured and such a small pressure rise value is extracted from this pressure value, the accuracy of the pressure measuring means is reduced to an error smaller than the small pressure rise value. There is a need to. In addition, the pressure sensor output is converted from analog to digital (A / D
Conversion) and digital pressure measurement or pressure rise measurement, the A / D converter
Very high resolution is required as well as measurement accuracy. For example, gas pressure value is 5 kgf / cm ^2, the micro-pressure increase value due to a failure is to 0.001kgf / cm ^2, 5.0
It is necessary to distinguish between 01 kgf / cm ² and 5.000 kgf / cm ^2, and a measurement accuracy or resolution of less than 0.02% is required. Achieving such high precision and high resolution poses a problem in terms of technical difficulty and economy.

[0005] In addition, the sealed pressure value fluctuates even when the gas temperature changes due to the influence of air temperature fluctuation and the like, so that no failure occurs. Therefore, assuming a fixed value of the sealed pressure value to be subtracted from the pressure value measured by the pressure sensor output,
Due to fluctuations in the normal sealed pressure value other than the failure, the pressure rise value may be erroneously detected, thereby erroneously detecting a failure.

Therefore, an object of the present invention is to measure the pressure value from the output of the pressure sensor without increasing the precision of the pressure measuring means or using an A / D converter with high resolution. Provided is a failure detection device for a gas-insulated electrical device that can also detect a minute pressure rise value due to a failure, and also correctly detect a failure without erroneously detecting a pressure rise due to a normal pressure fluctuation other than the failure. That is.

[0007]

A pressure sensor for detecting a gas pressure is provided in a gas-insulated electric device in which an insulating gas is sealed. A first differential amplifier and a second differential amplifier for amplifying the difference between the output signal of the pressure sensor and the reference signal are provided. A pressure value is measured from the output signal of the pressure sensor at a constant cycle, and the measured value is alternately read. On the one hand, the measured value is read as the reference signal of the first differential amplifier, and on the other hand, the measured value is read as the second signal. A reference signal setting unit for outputting as a reference signal of the differential amplifier unit. A first pressure rise detection unit for detecting a change amount from a current value and a past value that is a predetermined past time before the current value from the respective outputs of the first and second differential amplification units, and a second pressure rise detection unit A detection unit is provided.
A selection unit is provided for selecting an output of the first or second pressure rise detection unit that has passed the predetermined past time or more from the time when the reference signal setting unit outputs the reference signal. A determination unit is provided for comparing the output from the selection unit with a preset monitoring value and determining that a failure has occurred when the output exceeds the monitoring value.

[0008]

According to the present invention, as described above, a small pressure rise value due to a failure can be detected without using a high-precision pressure measuring means or using a high-resolution A / D converter. That is, the reference signal to the differential amplifying unit is set from the reference signal setting unit because the sealed pressure value measured by the pressure sensor in a certain cycle is set, so that a new reference signal is set in the next cycle after being set. If a failure occurs before this and the pressure rises, the differential amplifier obtains an output that amplifies only the pressure rise value due to the failure, which is the rise from the sealed pressure value. For this reason, the accuracy of the pressure measuring means is required to be not the accuracy of the measurement value including the sealing pressure value but the accuracy of the measurement value of the pressure rise obtained by subtracting the sealing pressure value. Even if it is not a means,
A minute pressure rise value can be detected. A / D
As for the resolution of the converter, only the resolution for the pressure rise value not including the sealed pressure value is required, and the high resolution A /
A minute pressure rise value can be detected without using a D converter.

Further, since the pressure rise value is detected by the amount of change between the current value of the output of the differential amplifying unit and the past value before a predetermined past time, by setting an appropriate past time, it is possible to obtain a value at the time of failure. The amount of change is large when the pressure rises steeply, but the amount of change is extremely small when the pressure changes slowly due to temperature or the like. For this reason, a pressure rise is not erroneously detected due to a slow change in the sealed pressure value due to a normal temperature or the like. Further, the pressure rise value is detected by a change amount between the present value of the output of the differential amplifier and the past value before a predetermined past time, and two sets of the differential amplifier and the pressure rise detector are provided. The pressure rise detection unit that has detected the amount of change from the current value and the past value of the differential amplification unit for the same reference signal is selected, and the determination unit determines. For this reason, a reference signal different from the reference signal set in the previous cycle is set due to a change in the sealed pressure value, thereby changing the output of the differential amplifying unit, and causing the pressure rise detection unit that has detected an erroneous change amount to change. You will not choose. Therefore, the pressure rise value detected due to an erroneous pressure change due to the change in the setting of the reference signal can be ignored, and only the pressure rise value due to the failure can be correctly detected.

[0010]

FIG. 1 shows an embodiment of the present invention. Note that this embodiment shows a case where the present invention is applied to a gas insulated switchgear.Although the gas insulated switchgear is usually divided into a plurality of gas compartments, the gas insulated switchgear is simply described for simplicity. An embodiment for one gas compartment will be described.
In FIG. 1, a gas compartment 1 of a gas insulated switchgear is formed by accommodating a device such as a circuit breaker (not shown) in a metal container 1a and enclosing an insulating gas 1b such as sulfur hexafluoride. . The gas compartment 1 is provided with a pressure sensor 2 for detecting the gas pressure of the insulating gas 1b. A first differential amplifier 3, a second differential amplifier 4, and a reference signal setting unit 5 are provided on the output side of the pressure sensor 2. The reference signal setting unit 5 is the first,
Second sample and hold circuits 51 and 52, and a control circuit 53 for controlling their sample state and hold state
It consists of.

The output signal of the pressure sensor 2 is supplied to the signal input terminals of the first and second differential amplifiers 3 and 4 and the first and second sample and hold circuits 5 of the reference signal setting unit 5.
1 and 52 are input to respective input terminals. Output signals of the first and second sample and hold circuits 51 and 52 are input to reference signal input terminals of the first and second differential amplifiers 3 and 4, respectively. Each of the first and second differential amplifiers 3 and 4 includes:
The difference between the input signal of the signal input terminal and the input signal of the reference signal input terminal is amplified. In each of the first and second sample-hold circuits 51 and 52 of the reference signal setting unit 5, the output in the sample state becomes the same signal as the input signal, and the input in the hold state immediately before the output changes from the sample state to the hold state. The signal is held and output until the hold state is released. The control circuit 53 controls the sampling and holding states of the first and second sample and hold circuits 51 and 52. The control circuit 53 includes a first control signal for the first sample and hold circuit 51 and a second sample and hold circuit 52. And outputting a second control signal.

A first pressure rise detector 6 is provided on the output side of the first differential amplifier 3 and a second pressure rise detector 7 is provided on the output side of the second differential amplifier 4. Output signals of the first and second pressure rise detection units 6 and 7 are input to the determination unit 9 via the selection unit 8. The first pressure rise detector 6 includes a delay circuit 61 that delays an input signal by a predetermined time and outputs the delayed signal, and an arithmetic circuit 62 that calculates a difference between the two input signals. The output signal of the first differential amplifier 3 is directly input to the arithmetic circuit 62 and is input via the delay circuit 61. The second pressure rise detecting section 7 has the same configuration, and includes a delay circuit 71 for delaying an input signal for a predetermined time and outputting the same and an arithmetic circuit 72 for calculating a difference between the two input signals, and a second differential amplifying section. 4 are directly input to the arithmetic circuit 72 and input via the delay circuit 71. Note that the delay circuits 61 and 7
The predetermined time delay of 1, ie, the delay time Td, is usually the same time.

The selecting section 8 selects and outputs one of the first and second pressure rise detecting sections 6 and 7. When the first sample and hold circuit 51 of the reference signal setting section 5 is in the sample state, From the hold state to the delay circuit 61
When the predetermined delay time Td or more has elapsed, the first pressure rise detection unit 6 is selected. The second signal of the reference signal setting unit 5
A predetermined delay time T of the delay circuit 71 after the sample and hold circuit 52 changes from the sample state to the hold state.
When d or more has elapsed, the second pressure rise detection unit 7 is selected. In this embodiment, this selection is performed by a selection control signal from the control circuit 53. The selection unit 8 can be constituted by, for example, an analog multiplexer, and can be realized by controlling the channel selection of the analog multiplexer as described above. The determination unit 9 compares the output signal of the selection unit 8 with a preset monitoring value, and
When the output signal exceeds the monitoring value, it is determined that the pressure rise is “present”, and a determination result indicating that the gas compartment 1 has failed is output.

Next, the operation of the present invention will be described with reference to FIG. FIG. 2 shows the output signal of the pressure sensor 2, the first and second control signals for the first and second sample and hold circuits 51 and 52 from the control circuit 53 of the reference signal setting unit 5, the first and second control signals.
, The output signals of the sample and hold circuits 51 and 52,
The output signals of the second differential amplifiers 3 and 4, the output signals of the delay circuits 61 and 71 and the arithmetic circuits 62 and 72 of the first and second pressure rise detectors 6 and 7, the reference signal setting unit 5 3 shows a selection control signal for the selection unit 8 from the control circuit 53 and an output signal of the selection unit 8.

The first of the control circuits 53 of the reference signal setting unit 5
The second control signal is a control signal that repeats a signal in which the first Ts seconds of the T seconds is a sample state period and the subsequent Th seconds is a hold state period in a T second cycle. However, the second control signal starts the sample state period T / 2 seconds after the start of the sample state period of the first control signal. The time relationship between the sample state period Ts and the hold state period Th is Ts << Th. Therefore, the first and second sample and hold circuits 5
Reference numerals 1 and 52 alternately hold the pressure values obtained by measuring the output signals of the pressure sensor 2 in a T / 2 second cycle for about T seconds (because of Ts << Th). In the case of FIG. 2, the first sample and hold circuit 51 outputs the first control signals t1, t
The pressure values P1, P3, P5, and P7 from the pressure sensor 2 sampled at time points 3, 3, and 5 are respectively held and output for T seconds. Further, the second sample and hold circuit 52
Means that the pressure values P2, P4, and P6 from the pressure sensor 2 sampled at times t2, t4, and t6 of the second control signal are respectively held and output for T seconds. These output signals serve as reference signals for the first and second differential amplifiers 3 and 4.

The output of the first differential amplifier 3 amplifies the difference between the pressure value P measured by the pressure sensor 2 and the reference signal output from the first sample and hold circuit 51.
The difference between the pressure values P and P1 during the period from time t1 to t3, the difference between the pressure values P and P3 during the period from time t3 to t5, and the pressure values P and P5 during the period from time t5 to t7.
And a signal obtained by amplifying the difference. The output of the second differential amplifier 4 is used to amplify the difference between the pressure value P measured by the pressure sensor 2 and the reference signal from the second sample and hold circuit 52. Is a signal obtained by amplifying the difference between the pressure values P and P2 in the period, and the signal obtained by amplifying the difference between the pressure values P and P4 in the period from the time point t4 to t6.

By doing so, the outputs of the first and second differential amplifiers 3 and 4 amplify only the pressure fluctuations that have changed from the sealed pressure value of the gas compartment 1, and therefore, Only the minute pressure fluctuation is amplified. For example, when measuring a small pressure rise value of 0.001 kgf / cm ² , the error of the conventional pressure measurement means is that the measurement range is 5 k
If gf / cm ² , it was necessary to be less than 0.02%. However, in the present invention, the measurement range of the pressure rise value of the first and second differential amplifiers 3 and 4 is 0.1 kgf / cm.
^In the case of 2, the measurement accuracy of the first and second differential amplifiers 3 and 4 may be less than 1%. Further, even if the sealed pressure value fluctuates due to temperature or the like, the reference signals of the first and second differential amplifying units 3 and 4 fluctuate accordingly, so that the first and second differential amplifying units 3 , 4 amplify only the minute pressure fluctuation from the reference value based on the changed sealed pressure value without saturation. Therefore, the minute pressure rise value can be detected without increasing the measurement accuracy of the first and second differential amplifiers 3 and 4.

In the first and second pressure rise detecting sections 6 and 7,
The pressure rise value is detected from the outputs of the first and second differential amplifiers 3 and 4. First and second pressure rise detection units 6,
7 have the same operating principle, the operation of one first pressure rise detection unit 6 will be described. The arithmetic circuit 62
The difference between the output signal of the first differential amplifier 3 and a signal obtained by delaying the output signal by the delay circuit 61 by a predetermined delay time Td is obtained. Therefore, the difference between the present value and the past value that is a predetermined past time Td before that time is determined, and the amount of change in the output of the first differential amplifier 3, that is, the pressure rise value can be detected. .

For example, from the time point (t1 + Td) in FIG.
In the period up to, due to pressure fluctuations due to normal temperature etc.,
The output of the first pressure rise detecting unit 6 has a very small change amount, but a large change amount during the period from time (t5 + Td) to t7 due to a steep pressure increase due to a failure. Similarly, the output of the second pressure rise detection unit 7 also has a very small change amount during the period from the time (t2 + Td) to t4, but has a large change amount due to the failure during the period from the time (t4 + Td) to t6. Becomes

The selecting section 8 starts to select the first pressure rise detecting section 6 after a delay time Td from the point in time when the first sample and hold circuit 51 enters the hold state, and the second sample and hold circuit 52 sets the hold state to the hold state. The selection is terminated after a delay time Td from the point in time when. Further, after the delay time Td from the time when the second sample and hold circuit 52 enters the hold state, the selection of the second pressure rise detection unit 7 is started, and the delay from the time when the first sample and hold circuit 51 enters the hold state is started. After the time Td, the selection ends. This selection control
As shown in FIG. 2, the selection is performed by a selection control signal from the control circuit 53. The output of the selection unit 8 thus selected includes the first,
Due to the change in the reference signals of the second differential amplifiers 3 and 4, an erroneous change output continuously from the first and second pressure rise detectors 6 and 7 for the time Td is not selected, and the change is correct. Only the amount will be output. For example, during the period from time t4 to (t4 + Td) in FIG. 2, an erroneous change due to a change in the reference signal of the second differential amplifying unit 4 is output from the second pressure rise detecting unit 7. Instead, the correct change amount detected by the first pressure rise detection unit 6 is used.

The determination unit 9 compares the correct change amount from the selection unit 8 with a preset monitoring value. If the pressure rise value exceeds the monitoring value, it is determined that a failure has occurred. And the failure is correctly detected. In FIG. 2, in the failure occurring during the period from the time (t5 + Td) to t7, since the first pressure rise detection unit 6 that outputs the correct change amount is selected, the pressure increase value is calculated based on the change amount of the output. Is detected, whereby the failure can be correctly detected.

Although the above is an embodiment in which the present invention is realized by an analog circuit, the functions of the first and second pressure rise detecting units 6, 7, the selecting unit 8, and the determining unit 9 are realized by digital processing. In this case, A / D converters are provided on the output sides of the first and second differential amplifiers 3 and 4, respectively. 1st, 2nd
As described above, the outputs of the differential amplifiers 3 and 4 amplify only the change from the sealed pressure value, and do not include the sealed pressure value. Therefore, the small pressure rise value can be detected without using a high-resolution A / D converter.

For example, a small pressure rise value 0.001 kgf /
When measuring cm ² , the resolution of the conventional A / D converter is 0.02 when the measurement range is 5 kgf / cm ^2.
%. However, according to the present invention,
If the measurement range of the A / D converter is 0.1 kgf / cm ² , its resolution should be less than 1%. Also, even if the sealing pressure value fluctuates due to temperature, etc., the first and second
Since the reference signals of the differential amplifiers 3 and 4 vary, only the minute pressure variation from the reference value is A / D-converted based on the changed sealed pressure value.
There is no need to use a / D converter.

Although the above embodiment has been described with respect to one gas compartment of a gas insulated switchgear, the present invention can be similarly applied to other gas compartments. Further, the present invention is not limited to the gas insulated switchgear, but can be applied to gas insulated electric devices such as gas insulated transformers.

[0025]

As described above, according to the present invention, when measuring a pressure value from the output of a pressure sensor, the accuracy of the pressure measuring means is not increased or the A / D of high resolution is measured.
Without using a converter, a small pressure rise value due to a failure can be detected, and further, a failure can be correctly detected without erroneously detecting a pressure rise due to a normal pressure fluctuation other than the failure.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 gas section 2 pressure sensor 3 first differential amplifier 4 second differential amplifier 5 reference signal setting unit 6 first pressure rise detection unit 7 second pressure rise detection unit 8 selection unit 9 determination unit

Claims (1)

(57) [Claims] 1. A pressure sensor provided in a gas insulated electric device in which an insulating gas is sealed, for detecting a gas pressure, and a first sensor for amplifying a difference between an output signal of the pressure sensor and a reference signal. A differential amplifier unit and a second differential amplifier unit, and a pressure value is measured at regular intervals from an output signal of the pressure sensor, and the measured values are alternately read, while the measured values are read by the first differential amplifier. A reference signal of the dynamic amplifying unit, a reference signal setting unit that outputs a measurement value read by the other as a reference signal of the second differential amplifying unit, and a reference signal setting unit that outputs the reference signal of the first and second differential amplifying units. A first pressure rise detection unit for detecting an amount of change from a current value and a past value a predetermined past time before the current value, and a second pressure increase detection unit.
The first or second pressure rise detecting section, wherein the predetermined past time or more has passed since the reference signal setting section output the reference signal.
A selection unit that selects the output of the pressure rise detection unit, a comparison unit that compares an output from the selection unit with a preset monitoring value, and determines that a failure has occurred when the output exceeds the monitoring value; A failure detection device for a gas-insulated electrical device, comprising: