JPH02198351A - Gas-leakage detecting apparatus - Google Patents

Abstract

PURPOSE:To detect gas leakage highly accurately by obtaining the change in gas pressure based on the change in gas temperature, and finding the change in quantity of gas. CONSTITUTION:A piece of resistance wire 5 is provided in a tank 2, wherein a main body 1 of stationary equipment and insulating gas are sealed, from the top to the bottom part of the tank. The output terminal of the wire is connected to a power source E. A detected voltage V1 from the resistance wire 5 is outputted. A pressure-voltage transducer 7 is communicated to the tank 2 through a pipe 8. A voltage V2 which is proportional to the gas pressure in the tank 2 is outputted. The voltages V1 and V2 are inputted into an operating device 9. The voltage which is proportional to the gas pressure at the time of sealing is corrected to a voltage corresponding to the gas pressure representing the upper and lower temperature distribution in the tank 2, based on the voltage V1. Said voltage is compared with the voltage V2 corresponding to the actually measured gas pressure. When the difference exceeds a specified value, warning is issued. Thus the gas leakage can be detected highly accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a gas leak detection device for gas-insulated stationary equipment and the like.

(Prior Art) In transformers and other stationary equipment that use insulating gas such as SF or gas, gas leakage causes insulation deterioration, so it is required to promptly detect it.

Conventionally, in order to detect this, the average temperature inside the tank is detected from the temperatures at the upper and lower parts of the tank filled with insulating gas, and the pressure of the gas at the time of filling the tank is corrected from that temperature.

When the difference between this corrected gas pressure and the actually measured gas pressure exceeds a certain value, it is determined that there is a gas leak and a necessary alarm is issued.

(Problem to be solved by the invention) However, according to a detection device with such a configuration.

Since the temperature inside the tank is measured at two points, the top and bottom, the measured value is likely to be affected by the mounting position of the thermometer. Furthermore, if the temperature inside the tank does not have a linear distribution in the vertical direction, it will be impossible to measure the average temperature, resulting in an error.

An object of the present invention is to detect gas leaks with high accuracy by determining changes in gas pressure from changes in gas temperature and determining changes in gas amount from this.

(Means for Solving the Problems) This invention stretches a resistance wire vertically inside a tank filled with gas, detects a change in resistance of the resistance wire due to a change in temperature inside the tank, and detects a change in resistance when the gas is filled. By correcting the gas pressure in the tank and comparing this corrected gas pressure with the separately detected gas pressure in the tank, gas leaks can be detected by knowing changes in the amount of gas in the tank. It is characterized by

(Function) Since the resistance wire is strung up and down inside the tank,
The resistance change corresponds very well to the temperature distribution within the tank, and therefore corresponds very well to changes in gas pressure due to temperature changes within the tank. Therefore, by correcting the gas pressure at the time of sealing based on this resistance change and comparing it with the actual measured value of the gas pressure, gas leakage can be detected with high accuracy.

(Example) An example of the present invention will be described with reference to the drawings. 1 is a coil,
Consists of iron core etc. For example, the main body of a stationary device such as a transformer, 2 is a tank that houses it, and 3 is an insulating gas sealed in the tank 2.

4 is a heat sink.

According to this invention, a resistance wire 5 made of a metal wire, such as copper or platinum, whose resistance change is proportional to a temperature change, is strung up and down from the top of the tank 2 to near the bottom. Support it with suitable insulating material or store it in a non-insulated case.

6 is a lead terminal of the resistance wire 5, and IIVL connected to a constant current source E, preferably a direct current, is the detected voltage of the resistance wire 5. Reference numeral 7 denotes a pressure-voltage converter, which is connected to an arbitrary location within the tank 2 through a pipe 8, and outputs a voltage v2 proportional to the pressure of the gas within the tank 2.

Reference numeral 9 denotes a calculation device, which inputs the voltage Vt=Vx and performs calculations as described later to apply a voltage proportional to the preset gas pressure at the time of sealing to the upper and lower temperature distribution in the tank 2 using the voltage v1. Correct the voltage to correspond to the corresponding gas pressure.

And this is the voltage v2 corresponding to the gas pressure actually measured.
If the difference exceeds a certain value, an alarm will be issued.This alarm indicates that there is a gas leak. The configuration and operation of the arithmetic unit 9 will be explained in detail with reference to FIG.

Next, the measurement principle according to the present invention will be explained.

The current reference temperature (for example, the temperature when gas is sealed) T,
The specific resistance of the resistance wire 5 at is ρ. , the temperature coefficient is β. If the cross-sectional area of the resistance wire is S, the length is divided, and the difference in temperature from one end of the resistance wire to the reference temperature is Δt, the resistance of the resistance wire is expressed by the following equation.

Here, R is the resistance value of the resistance wire at the reference temperature T, and ρ R,= represents the integration.

On the other hand, if the temperature in a microvolume dV at any location in the tank is T, then the gas pressure in the tank is calculated using the following formula (%). shows.

Here, if the temperature change is not very large, ΔT/T
Since <<1, 1/(1+ΔT/T,)=1−ΔT/T, if we consider that the temperature distribution in the tank is almost equal to the temperature distribution in the height direction along the resistance line at 22, Since V in equation (2) is replaced, dV is replaced with dX, and ΔT is replaced with Δt, P0 Also, from equation (1).

From Equations (3) and (4), it is found that the rate of change in P can be found by multiplying the rate of change in R by 17βT0.

Next, we will give a specific numerical example to explain the case where pressure change is determined from resistance value.As an example, T0=0℃=273
K (K is absolute temperature) and if copper is used for the resistance wire, β = 4.3 x 10-3, so l/βT
,=0.852. Therefore, if the resistance change of the resistance wire is ΔR, the gas pressure is calculated as follows.

Assuming that △T = 50℃ on the upper side and that the temperature is linearly distributed in the height direction of the tank, and calculating P directly from equation (1'), T = T0 + (50/L) x (x is height from the bottom of the tank).

T, + -x becomes.

On the other hand, the resistance value is.

=R, (1+4.3X10-3X25)=1.1075
R0 From now on, calculate the change in P using equation (5).

ΔP=0.852x (1,1075-1) P,=0
．． 092P.

Therefore, P calculated from the change in R is 1.09
2P, which is an extremely close value to 1,089P, which was directly calculated earlier.

It is clear from this that the value obtained by multiplying the rate of change in resistance determined from the actually measured resistance value by 1/βT0 may be regarded as the rate of change in pressure.

Next, an example of the arithmetic unit 9 in FIG. 1 will be explained with reference to FIG. 2. In the figure, the pressure P0 in the tank 2 at the reference temperature is set in the setter 11, and the resistance value R6 of the resistance wire 5 at the reference temperature is set in the setter 12.

The set value R0 by the setter 12 is given to the subtracter 13 together with the voltage V□ of the resistance wire 5, and the difference between the two values, that is, (
Outputs the calculated value corresponding to R−R, ). This calculated value is calculated by the coefficient unit 1 whose coefficient is (1/R,) set in advance.
4, where it is multiplied by a coefficient. Therefore, its output has a value corresponding to the rate of change of the resistance value R.

The output from the coefficient 514 is input to the coefficient unit 15, which has (1/βT6) set as a coefficient in advance, and is multiplied by that coefficient. Therefore, the output becomes a value corresponding to the rate of change of pressure P (Δp/pe) as described above.

The output of the coefficient unit 15 is given to a multiplier 16, which receives the set value P of the setter 11. is multiplied by The output corresponds to the change in pressure P ΔP. The output and the setting value of the setting device 11 are added by the adder 17, and (po+Δp=p)
Outputs the value corresponding to . This value is nothing but the pressure value corrected by the resistance value.

Therefore, this output and the output of the pressure-voltage converter 7 are
A comparison is made by the comparator 18, and when the difference is greater than a certain value, it can be determined that there is a gas leak from the tank 2. For example, when the above-mentioned difference exceeds a certain value, the comparator 18 may output an output to issue a warning.

It goes without saying that instead of the configuration shown in FIG. 2, a configuration using a microcomputer, for example, may be used.

(Effects of the Invention) As detailed above, according to the present invention, the resistance change of the resistance wire stretched vertically in the tank corresponds extremely well to the change in gas pressure due to temperature conversion. By correcting the gas pressure at the time of sealing based on the change and comparing it with the actual measured value of the gas pressure, it is effective to be able to detect gas leaks with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the invention, and FIG. 2 is a block diagram showing an example of an arithmetic device.

Claims (1)

[Claims] A resistance wire stretched vertically in a tank filled with gas, a detection means for detecting a change in resistance of the resistance wire due to a temperature change in the tank, and a resistance change detected by the detection means. a multiplier for calculating the rate of change in the gas pressure in the tank by multiplying the value (1/βT_0) (where β is the temperature coefficient of the resistance line and T_0 is the reference temperature); a calculation means for calculating the gas pressure during operation by multiplying the rate of change of the gas pressure in the tank by the gas pressure when the gas is filled in the tank; and the gas pressure calculated by the calculation means and the gas pressure in the tank. A gas leak detection device comprising: comparison means for comparing a measured value of the gas leakage amount with an actual measured value, and determining a change in the amount of gas in the tank from the comparison result by the comparison means.