JP3023965B2 - Overheat monitoring device for electrical equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an overheating monitoring device for electric equipment.

(Prior art) In order to monitor abnormal overheating of electric equipment stored in a cubicle or the like, a gas is generated in response to the abnormal overheating, and the occurrence of the overheating state is monitored by detecting the gas. There is something like that.

FIG. 4 shows an example of this, in which an overheat detection unit 43 is installed on a bus 42 to be overheated, which is installed inside a cubicle 41. The overheat detection unit 43 has a gas, for example, a hydrogen gas generation source inside, and is configured to discharge the gas to the outside in response to the overheat state. One example is shown in JP-A-1-320478.

The released gas is detected by the gas sensor 44.
The result is sent to the determination unit 45, where it is determined whether or not the overheating is abnormal. When it is determined that the overheating is abnormal, an alarm output is issued.

Conventionally, in order to avoid a malfunction due to noise, a gas having a high concentration (for example, 20 ppm or more) that cannot be generated in a natural state is generated from the overheating detection unit 43, and the gas sensor 44 has a high Was configured to issue an alarm when the gas was detected.

(Problems to be solved by the invention) However, according to such a configuration, the overheat detection unit 43
Need to generate a large amount of gas from
For that purpose, the overheating detection unit 43 must also be made large. When the overheating detection unit 43 is increased in this way, an insulation problem occurs, and the use range is greatly limited.
Practical application becomes extremely difficult.

An object of the present invention is to make it possible to detect abnormal overheating separately from noise gas even when low-concentration gas is generated from the overheating detection unit.

(Means for Solving the Problems) The present invention provides an overheating detection unit that emits a low-concentration gas in response to abnormal overheating of electric equipment, a gas sensor that detects the gas, and abnormal overheating based on an output from the gas sensor. In the overheating monitoring device for electric equipment, comprising: an overheating determination unit that determines the increase in temperature. In order to determine an increase tendency due to gas release of the overheating detection unit, the output from the gas sensor is sampled at predetermined time intervals at at least three points. Sampling means, calculating means for calculating the amount of change between the sampling value of each sampling by the sampling means and the sampling value at the previous sampling, and determining the magnitude of the result calculated by the calculating means and a predetermined reference value. Judgment is made at each sampling, and a signal is issued when the state exceeding the reference value continues for a certain period of time. And determining that abnormal overheating is generated when a signal from the determining unit is generated.

(Operation) When a gas is released from the overheating detection unit due to the occurrence of abnormal overheating, the detected concentration increases with time. Therefore, the output from the gas sensor is sampled at predetermined time intervals, the amount of change from the previous sampled value is obtained for each sampling, and the amount of change is compared with a reference value. Then, when the state in which the amount of change exceeds the reference value continues for a certain period of time, it is determined that the gas has been released from the overheat detection unit, and it is considered that abnormal overheating has occurred.

In the case of the noise gas, the change in concentration is slow and a sharp increase in concentration as in the case where the overheat detection unit is activated is unlikely to occur. Therefore, the occurrence of abnormal overheating can be determined in distinction from the case of noise gas.

(Embodiment) An embodiment of the present invention will be described with reference to FIG. Reference numeral 1 denotes the gas sensor described with reference to FIG. FIG. 2 shows an example of the configuration. In the figure, reference numeral 21 denotes a metal oxide semiconductor for gas detection, and its resistance changes when it comes into contact with gas.

22 is a load resistor, the Yes is connected to the semiconductor 21 in series, the series circuit are connected between the circuit constant voltage V ₀ is are applied. 23 is a heater for heating the semiconductor 21.

The gas sensor 1 outputs a terminal voltage V of the load resistor 22.
This voltage V is converted into a resistance value of the semiconductor 21. For example, assuming that the resistance value of the load resistor 22 is R, the resistance value r of the semiconductor 21 can be obtained from the following equation.

In FIG. 1, an output from a gas sensor 1 is converted into a digital value by an A / D converter 2 and then sent to a voltage-resistance converter 3. Here, the resistance value is converted into a resistance value r based on the above equation. This converted value is sampled by the sampling means at intervals of, for example, two seconds and stored in the memory 5. The sampling is performed by a pulse from the timing pulse generation circuit 4, and the interval between the sampling and the generation of the gas by the overheat detection unit increases by 3.
It is a time interval that can be detected above the point. Further, the sampling value may be an average value or an intermediate value of the conversion values during a sampling interval.

Reference numeral 6 denotes a computing unit. The calculator 6 calculates, for each sampled value, the amount of change between the previous sampled value and the current sampled value.

Specifically, as shown in FIG. 3, the arithmetic unit 6 calculates B / A when B is sampled, where A, B, C,... .
When C is sampled, C / B is calculated. The calculation result is sent to the determiner 7 each time the calculation is performed.

Note that the first sampling value A is provided to the memory 8 via the arithmetic unit 6. Next sampling B is arithmetic unit 6
, The computing unit 6 fetches the previous sampling value A from the memory 8 and performs the above-described computation here.

Then, after this calculation is completed, the calculation result is sent to the determiner 7, and the sampling value B is stored in the memory 8 in place of the sampling value A that has been stored so far. This is repeated below.

The determiner 7 determines the result of the operation described above. That is, the calculation result is a predetermined reference value smaller than 1, for example, 0.9.
A magnitude relationship with respect to 0.90.99, preferably 0.98 is determined.
When the operation result is larger than 0.98, it is regarded as a normal state, and when it is equal to or smaller than 0.98, it is regarded as an abnormal state.

When the above calculation result is equal to or smaller than the predetermined reference value smaller than 1, it means that the gas concentration at the time of the previous sampling has increased. Therefore, it is clear from this that the abnormal increase in the gas concentration continues.

A state in which the above-described calculation result is equal to or smaller than the predetermined reference value is repeated, and when the number of times reaches the predetermined value, an alarm signal is output from the determiner 7.

This number is set by the timer 9. That is, assuming that the sampling interval is 2 seconds, if the sampling is started and then continues for a predetermined time set in the timer 9, for example, 10 seconds, an alarm signal is output from the determiner 7 by a signal from the timer 9.

If, during this time, the above-mentioned calculation result becomes larger than the predetermined reference value even once, a reset signal is given to the decision unit 7 and reset. Then, the determination for each sampling is repeated again from the beginning.

Instead of the configuration shown in the figure, this may be configured by a microcomputer or the like.

(Effects of the Invention) As described in detail above, according to the present invention, upon detecting abnormal overheating from the gas released when abnormal overheating occurs, the output from the gas sensor gradually increases over a certain period of time. As it is determined that abnormal overheating has occurred, it is possible to detect the gas generated by the overheating detection unit separately from noise gas, and it is not necessary to generate a large amount of gas at the time of abnormal overheating, Therefore, the size of the overheat detection unit can be reduced, and the degree of freedom of the place where the overheat detection unit is installed can be increased even in the electric equipment having a structure in which the overheat detection unit is inserted, so that it is possible to more effectively detect abnormal overheat.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram of a gas sensor, FIG. 3 is a characteristic diagram showing a change in output of the gas sensor, and FIG. 4 is a layout diagram in electric equipment. DESCRIPTION OF SYMBOLS 1 ... Gas sensor, 3 ... Voltage-resistance converter, 4 ... Timing pulse generation circuit, 6 ... Calculator, 7 ... Determiner, 9 ... Timer, 41 ... Electrical equipment, 43 ... Overheat detection Unit, 45 ... Overheat judgment unit,

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-97130 (JP, A) JP-A-62-2899753 (JP, A)

Claims (1)

(57) [Claims] An overheat detecting unit that emits a low-concentration gas in response to abnormal overheating of electrical equipment, a gas sensor that detects the gas, and an overheat determining unit that determines abnormal overheating based on an output from the gas sensor. In the overheating monitoring device for electric equipment provided, in order to determine an increasing tendency due to gas release of the overheating detection unit, sampling means for sampling the output from the gas sensor at predetermined time intervals at at least three points, Calculating means for calculating the amount of change between the sampling value and the sampling value at the time of the previous sampling for each sampling; determining the magnitude of a result calculated by the calculating means and a predetermined reference value for each sampling; Determining means for generating a signal when a state exceeding the value continues for a predetermined time; Electrical equipment overheating monitoring device with a generation of a signal from the means and to the occurrence of abnormal overheating.