JP2600823Y2 - Abnormal overheat detector for gas insulated switchgear - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormal overheat detecting device for detecting whether or not abnormal overheating has occurred in a container of a gas insulated switchgear.

[0002]

2. Description of the Related Art In a gas insulated switchgear, a device is used as a device for detecting whether or not abnormal overheating has occurred due to an abnormal current supply (increase in contact resistance, etc.) or a poor contact of an electrical contact portion. In some cases, the presence or absence of abnormal overheating is detected by converting the detected value of the gas pressure into a gas pressure at room temperature and comparing the converted gas pressure at room temperature with a predetermined overheat determination level. In this case, the temperature used for the calculation of the normal-temperature converted gas pressure should originally be the temperature of the gas in the container, but in a gas-insulated switchgear in which it is necessary to minimize the insertion of foreign matter that may disturb the electric field. Since it is difficult to insert a temperature sensor into a container, the ambient temperature of the container is actually detected and the detected value is used for gas pressure conversion.

A detector of this type includes a pressure sensor for detecting the pressure of gas in a container of the gas insulated switchgear, a temperature sensor for detecting a temperature outside the container, a detection output of the pressure sensor and a detection output of the temperature sensor. A normal temperature converted gas pressure calculating means for calculating the gas pressure detected by the pressure sensor into a gas pressure at normal temperature (normally 20 ° C.) to obtain a normal temperature converted gas pressure, and overheating the normal temperature converted gas pressure An abnormal overheat judging means for judging that abnormal overheating has occurred in the container when the normal temperature converted gas pressure exceeds the overheat judgment level as compared with the judgment level.

FIG. 11 shows a schematic configuration of an apparatus (hardware) used for this detection method.
Is a pressure sensor for detecting the pressure inside the container of the gas insulated switchgear, and 2 is a temperature sensor for detecting the ambient temperature of the container.
The outputs of these sensors are input to the computer 4 via the sensor input unit 3.

[0005] The computer reads the detected value of the pressure sensor and the detected value of the temperature sensor every predetermined time, for example, every 10 minutes, and performs an operation of converting the detected value of the pressure sensor into a pressure value at normal temperature. . Here, assuming that the gas density coefficient of the gas in the container is L, the normal temperature is 20 ° C., the detected value of the gas pressure at time n is Px, the detected value of the temperature is Tx, and the gas pressure converted to normal temperature is Pnx, the following Pnx is obtained. It is obtained by the formula.

Pnx = Px + L (20−Tx) (1) The normal temperature-converted gas pressure calculating means is realized by performing the above calculation.

In the process of realizing the abnormal overheating judging means, the presence or absence of abnormal overheating is judged by comparing the normal temperature converted gas pressure Pnx with an overheating judgment level. That is, the pressure increase in the container when no abnormal overheating has occurred in the container is only an increase in gas pressure due to an increase in gas pressure due to an increase in outside air temperature and an increase in gas pressure due to heat generated with energization in a steady state.
The normal temperature gas pressure does not exceed a certain range. On the other hand, when abnormal overheating is added to the cause of the increase in the gas pressure in the container, the normal-temperature-converted gas pressure rises beyond a predetermined range. Therefore, the judgment level Pr appropriately set is compared with the normal temperature-converted gas pressure Pnx at each sampling time, and Pnx
When> Pr, it can be detected that abnormal heating has occurred. In the conventional detection device, for example, the normal temperature-converted gas pressure Pnx calculated from the sampled value is sampled every 10 minutes and compared with the overheat determination level Pr, and the normal temperature-converted gas pressure continuously exceeds the overheat determination level twice. When this is detected, an overheat detection output such as an alarm is generated.

In the conventional abnormal overheat detecting device, the overheat judging level Pr basically includes a charged gas pressure Po in the vessel at 20 ° C., a pressure rise ΔPImax expected when the maximum load current is applied, and a disturbance (mainly, (Change in outside air temperature) and the maximum pressure increase ΔP (+) max expected. Here, the pressure increase ΔPImax expected when the maximum load current is applied and the maximum pressure increase ΔP (+) max expected due to disturbance are obtained by actual measurement and are fixed values, but the charge gas pressure Po (heat due to load current) And the pressure inside the container when the ambient temperature is 20 ° C.) changes each time the inside of the container is charged after maintenance and inspection and repair are performed. Therefore, in practice, the overheat determination level Pr is set by the following equation (2) in consideration of the margin α.

Pr = Po + ΔPImax + ΔP (+) max + α (2) FIG. 12 shows a change in the normal-temperature-converted gas pressure with respect to the load current. In FIG. 12, a curve a indicates a pressure change due to a disturbance (change in air temperature or the like). It shows the change of gas pressure in the container with respect to the load current when there is no load current, and the maximum value is ΔPIm
ax. Curve b shows the pressure change ΔP (+) max due to disturbance.
Shows a pressure change in the case where is added. Conventionally, the gas pressure in the container is determined as the overheat determination level Pr = Po + ΔPImax +
Abnormal overheating is detected when ΔP (+) max + α is exceeded.

As described above, in the conventional abnormal overheat detecting device, the overheat judging level Pr is set by the equation (2), but the change width of the charge gas pressure Po is ΔPImax + ΔP (+) max.
Therefore, the margin α needs to be set to be considerably large in the equation (2). For this reason, the magnitude of the overheat determination level Pr becomes considerably large, and it is inevitable that the detection sensitivity of abnormal overheat is reduced.

Further, when trying to detect abnormal overheating of an existing gas insulated switchgear, the pressure rise due to the load current cannot be reduced to zero, so that the charged gas pressure in the container may not be measured. In this case, the overheat determination level Pr could not be set properly.

Therefore, the inventor of the present invention first described the charged gas pressure Po
An abnormal overheat detection device that can accurately set the overheat determination level without being affected by the variation width of the pressure and the pressure rise caused by the load current has been proposed.

In the above-mentioned abnormal overheat detecting device, the gas output from the pressure sensor for detecting the gas pressure inside the container of the gas insulated switchgear and the output of the temperature sensor for detecting the temperature outside the container are used to detect the gas caused by disturbance. A specific time set in a time zone in which pressure change is small and load fluctuation is small (for example, 5 am
) Is calculated as the specific time normal temperature converted gas pressure Pnp in the container at the time, and the specific time normal temperature converted gas pressure Pnp is the lowest value of the specific time normal temperature converted gas pressure Pnp calculated at the same time before the previous day. Is selected as the base pressure Pb. The base pressure Pb has a maximum drop ΔP (−) max of the normal temperature converted gas pressure due to the disturbance at the specific time and a rise ΔΔ (−) max of the gas pressure when the maximum load current is applied.
The superheat determination level Pr = Pb + ΔP (−) max + Δ is obtained by adding PImax and the maximum rise ΔP (+) max of the gas pressure due to the disturbance.
PImax + ΔP (+) max is calculated, and it is detected that abnormal overheating has occurred when the sequentially calculated normal-temperature-converted gas pressure Pnx exceeds the above-mentioned overheating determination level Pr.

[0014]

In the above-described abnormal overheat detecting device, the equation Pr = P for obtaining the overheat determination level is used.
b + ΔP (−) max + ΔPImax + ΔP (+) max The second to fourth terms [ΔP (−) max + ΔPImax + ΔP (+) max] on the right side are fixed values, but the first term, Pb, is defined as Each time the normal-temperature-converted gas pressure becomes low, it is changed to that low value. In this way, the base pressure Pb asymptotically approaches the gas pressure when the load current is the minimum and the pressure drop due to the disturbance is the maximum [when the pressure drop of ΔP (-) max occurs]. Therefore, the term of Pb + ΔP (−) max on the right side of the equation for obtaining the overheat determination level Pr asymptotically approaches the charged gas pressure in the container.

Therefore, when the overheating judgment level is set by the above equation, the overheating judgment level can be converged to a minimum necessary value, and the overheating judgment level must be set with a large margin. The detection sensitivity can be increased as compared with a conventional abnormal overheat detection device.

As described above, in the gas insulated switchgear, it is difficult to directly measure the temperature of the gas in the container. Therefore, when converting the gas pressure detected by the pressure sensor into the gas pressure at room temperature, However, the temperature outside the container detected by the temperature sensor must be used. However, since the difference between the temperature outside the container and the gas temperature inside the container is not constant and greatly differs between summer and winter, when the specific time normal temperature conversion gas pressure Pnp is calculated using the temperature outside the container In summer, the value will be significantly different between summer and winter, and it has been clarified that the proposed overheating detection device may cause the overheating judgment level to be too low in summer and cause erroneous detection. Was.

In general, there is a linear relationship between the gas pressure P and the gas temperature T as shown by a straight line in FIG.
There is a relationship of P = Lo · T + Mo. Here, Lo is a gas density coefficient, Mo is a constant, and the gas density coefficient Lo indicates a constant value if the type of gas is constant and there is no gas leakage.
On the other hand, the relationship between the temperature T outside the container of the gas insulated switchgear and the gas pressure P inside the container is generally as shown by a straight line in FIG. 9, and when this is expressed by an equation, P = L · T + M. . Here, L is an apparent gas density coefficient and M is a constant. Generally, the apparent gas density coefficient L shows a value larger than the actual gas density coefficient Lo. In the previously proposed apparatus, the gas pressure Pnp at a specific time and a normal temperature was calculated using the gas density coefficient Lo known in advance, but the gas pressure and the temperature sensor detected at a specific time by the pressure sensor were used. Since the ambient temperature is on the straight line in FIG. 9, the detected value Px1 of the gas pressure at the ambient temperature T1 higher than the normal temperature (20 ° C. in this example) is converted into the pressure at the normal temperature using the gas density coefficient Lo. Then, the converted value becomes Pnp1 shown in FIG. 9, which is larger than the correct normal-temperature converted gas pressure Pnp. Similarly, when the detected value Px2 of the gas pressure at the ambient temperature lower than the normal temperature is converted into the gas pressure at the normal temperature using the gas density coefficient Lo,
The converted value becomes like Pnp2 in FIG. 9, which is smaller than the correct normal-temperature converted gas pressure Pnp.

FIG. 10 shows a gas pressure Pnp converted to a normal temperature at a specific time.
This shows the change throughout the year (all-year change). As is clear from FIG.
Indicates the maximum value Pnpmax in summer when the temperature is higher than room temperature, and indicates the minimum value Pnpmin in winter when the temperature is lower than room temperature.

In the proposed abnormal overheat detecting device, when the gas pressure Pnp at the specific time and the normal temperature reaches the minimum value Pnpmin in winter, the base pressure Pb is fixed to the minimum value thereafter. Therefore, in the next summer when the normal-time converted gas pressure rises to the maximum value Pnpmax at the specific time, the sequentially calculated normal-temperature converted gas pressure Pnx approaches the overheat determination level Pr by the maximum ΔPnp, and the overheat determination level decreases. Erroneous detection may occur. In order to avoid this erroneous detection, it is conceivable to set the overheat determination level Pr by ΔPnp higher. However, in such a case, the overheat determination level in winter becomes too high, and the detection sensitivity decreases. Inevitable.

An object of the present invention is to provide an abnormal overheat detection device for a gas insulated switchgear which can increase detection sensitivity throughout the year without causing erroneous detection in a specific period.

[0021]

As shown in FIG. 1, the abnormal overheat detecting device according to the first aspect of the present invention comprises a pressure sensor 1, a temperature sensor 2, a normal temperature converted gas pressure calculating means 5, , Base pressure selection means 6, winter superheat determination level calculation means 8, summer superheat determination level calculation means 9
And abnormal overheat judging means 10.

The pressure sensor 1 detects the pressure of the gas inside the container of the gas insulated switchgear, and the temperature sensor 2 detects the temperature outside the container.

The normal-temperature-converted gas pressure calculating means 5 receives the detection output of the pressure sensor and the detection output of the temperature sensor as inputs,
An operation for converting the gas pressure Px detected by the pressure sensor into a gas pressure at room temperature is performed to obtain a room temperature converted gas pressure Pnx.

The base pressure selecting means 6 converts the normal temperature converted gas pressure calculated by the normal temperature converted gas pressure calculating means at a specific time set at a time when the change in gas pressure due to disturbance is small and the load fluctuation is small, to a specific time and normal temperature conversion. The gas pressure Pnp is compared with the lowest value of the specific time normal temperature converted gas pressure Pnp calculated at the same time before the previous day, and the lower of the compared specific time normal temperature converted gas pressure is selected as the base pressure Pb.

The overheat judging level calculating means 8 for winter includes a base pressure Pb selected by the base pressure selecting means 6, a maximum decrease ΔP (-) max of a normal temperature converted gas pressure due to a disturbance at a specific time, and a maximum load current supply. Gas pressure rise ΔPImax and maximum gas pressure rise ΔP (+) m due to disturbance
ax and the overheat determination level for winter Prw = Pb + ΔP
(−) max + ΔPImax + ΔP (+) max is calculated.

The summer-time superheat determination level calculating means 9 calculates the difference ΔPnp between the minimum value Pnpmin and the maximum value Pnpmax when the change in the gas pressure Pnp converted to normal temperature at normal time throughout the year is observed.
Assuming that Pnpmax-Pnpmin is a specific time normal temperature converted gas pressure difference, the specific time normal temperature converted pressure difference ΔPnp is added to the winter superheat determination level Prw to obtain the summer superheat determination level P.
Calculate rs.

The abnormal overheat judging means 10 sets a certain period before and after the month when the specific time normal temperature converted gas pressure Pnp shows the minimum value Pnpmin as winter, and before and after the month when the specific time normal temperature gas pressure Pnp shows the maximum value Pnpmax. A certain period is set as summer, and one year is divided into winter and summer, and in winter, the normal temperature converted gas pressure Pnx is compared with the winter superheat judgment level Prw, and the normal temperature converted gas pressure Pnx becomes the winter superheat judgment level Prw. If it exceeds, it is determined that abnormal overheating has occurred in the container of the gas insulated switchgear.
Is compared with the summer superheat determination level Prs, and when the normal temperature converted gas pressure Pn exceeds the summer superheat determination level Prs, it is determined that abnormal overheating has occurred in the container of the gas insulated switchgear.

In the present invention, one year is divided into winter and summer as described above. In the present invention, each of the winter and summer periods is performed at the installation location of the gas insulated switchgear. It is appropriately determined according to the actual change of the specific time normal temperature converted gas pressure Pnp. That is, the winter and summer periods are determined from the characteristics of the year-to-year change of the specific-time normal-temperature-converted gas pressure Pnp, and from what day to how many days are winter and how many days are summer. This depends on the climate of the place where the gas insulated switchgear is installed (temperature change throughout the year). In determining the respective periods of winter and summer, for example, the change of the specific time normal temperature converted gas pressure Pnp throughout the year is stored, and the change of the specific time normal temperature converted gas pressure Pnp for one year is grasped. A certain period around the day when the specific time normal temperature converted gas pressure Pnp showed the maximum value is a certain period before and after the summer,
What is necessary is just to make the fixed period before and after the specific time ordinary temperature converted gas pressure Pnp the minimum value the winter time around the day on which the minimum value is shown. The lengths in summer and winter may not be equal.

The winter and summer periods may be set to be the same every year, and the winter and summer periods may be corrected based on data accumulated every year or each time a certain number of years have elapsed. Good.

Similarly, the gas pressure difference .DELTA.P
The value of np may be updated every year based on the actually measured value, or the same value may be used for a predetermined year and month.

As shown in FIG. 2, the abnormal overheat detecting device according to the second aspect of the present invention includes a pressure sensor 1 for detecting a gas pressure in a container of a gas insulated switchgear and a temperature sensor outside the container. It comprises a temperature sensor 2 to be detected, a gas density coefficient calculating means 11, a normal temperature converted gas pressure calculating means 5 ', a base pressure selecting means 6, an overheating determination level calculating means 8', and an abnormal overheating determining means 10 '. Is done.

The gas density coefficient calculating means 11 calculates the gas pressure versus the ambient temperature from the ambient temperature and the gas pressure detected by the pressure sensor and the temperature sensor in a specific time zone in which the change in the gas pressure due to the disturbance is small and the load fluctuation is small. The characteristic is determined, and an apparent gas density coefficient L is determined from the gas pressure-ambient temperature characteristic.

The normal-temperature-converted gas pressure calculating means 5 'receives the detection output of the pressure sensor and the detection output of the temperature sensor as inputs,
Using the latest apparent gas density coefficient L, the gas pressure detected by the pressure sensor is converted into a gas pressure at room temperature to obtain a room temperature converted gas pressure Pnx.

The base pressure selecting means 6 calculates the normal temperature-converted gas pressure calculated by the normal temperature-converted gas pressure calculating means 5 'at a specific time set at a time when the change in gas pressure due to disturbance is small and the load fluctuation is small. It is compared with the lowest value of the specific time normal temperature converted gas pressure Pnp calculated at the same time before the previous day as the normal temperature converted gas pressure Pnp, and the lower of the compared specific time normal temperature converted gas pressure is selected as the base pressure Pb.

The overheat judging level calculating means 8 'is provided with a base pressure Pb selected by the base pressure selecting means and a maximum decrease Δ 常 of the normal temperature converted gas pressure due to disturbance at a specific time.
P (-) max and increase ΔP of gas pressure when maximum load current is applied
Superheat determination level Pr = Pb + ΔP (−) max + ΔP by adding Imax and the maximum rise ΔP (+) max of gas pressure due to disturbance.
Calculate Imax + ΔP (+) max.

The abnormal overheat judging means 10 'compares the normal temperature converted gas pressure Pnx with the overheat judgment level Pr, and when the normal temperature converted gas pressure Pnx exceeds the overheat judgment level Pr, abnormal overheating occurs in the container. It is determined that there is.

In the above-mentioned specific time zone, similarly to the time zone for setting the time for detecting the gas pressure for calculating the normal-temperature converted gas pressure, the change in the gas pressure due to disturbance is small,
It is a time when the load fluctuation is small, and this specific time is
Generally, it is preferable to set the time zone from midnight to 6:00 am. Further, in order to calculate the normal-temperature converted gas pressure Pnp at a specific time using the latest gas density coefficient L, it is preferable that the specific time zone is a time zone before the specific time.

[0038]

In the invention described in claim 1, the base pressure selecting means compares the specific time ordinary temperature converted gas pressure Pnp every day with the minimum value of the specific time ordinary temperature converted gas pressure Pnp at the same time before the previous day. Therefore, the lower one is set as the base pressure Pb. Therefore, Pb of the first term on the right side of the arithmetic expression Prw = Pb + ΔP (−) max + ΔPImax + ΔP (+) max that gives the overheating determination level in winter decreases as the normal-temperature gas pressure in the container at a specific time decreases. Is changed to the value.
The base pressure Pb is asymptotic to the gas pressure when the load current is minimum and the pressure drop due to disturbance is maximum [when a pressure drop of ΔP (-) max is occurring]. The term of Pb + ΔP (−) max on the right side of the equation for obtaining Prw gradually approaches the charged gas pressure in the container. When Pnp reaches the minimum value in winter, the overheating determination level P
rw is fixed. In winter, by using the overheating determination level Prw, the detection sensitivity of abnormal overheating can be increased without causing erroneous detection. The overheat determination level Prw in the winter is the same as the overheat determination level used in the proposed device, and converges to a minimum necessary value in the winter.

As described above, erroneous detection may occur if abnormal overheating is detected in summer using the overheating determination level Prw in winter as it is. Therefore, in the present invention,
The minimum value Pnpmin and the maximum value Pnpmax when the change in the specific time normal temperature converted gas pressure Pnp is observed throughout the year are calculated, and the difference ΔPnp = Pnpmax−Pnpmin between them is calculated as the specific time normal temperature converted gas pressure difference. A value obtained by adding the specific time normal temperature converted gas pressure difference ΔPnp to the winter overheat determination level Prw is used as the abnormal overheat determination level Prs in summer. As a result, the overheat determination level Prs in summer can be given a minimum margin, and erroneous detection can be prevented from occurring in summer without lowering the detection sensitivity.

According to the first aspect of the present invention, in winter when the normal-temperature converted gas pressure is calculated to be low, the overheat determination level is converged to the minimum necessary value, and the normal-temperature converted gas pressure is increased. In the calculated summer season,
At specific time, normal temperature converted gas pressure difference Δ
By making the level to which Pnp is added the overheating determination level, the overheating determination level has the minimum necessary margin, so that the detection sensitivity can be increased without causing erroneous detection throughout the year.

According to a second aspect of the present invention, the gas pressure is changed from the ambient temperature and the gas pressure detected by the pressure sensor and the temperature sensor in a specific time zone in which the change in gas pressure due to disturbance is small and the load fluctuation is small. When the apparent gas density coefficient L is obtained from the pressure versus ambient temperature characteristic, the apparent gas density coefficient L is calculated from the gas pressure versus ambient temperature characteristic, and the normal-temperature-converted gas pressure is calculated using the latest apparent gas density coefficient L,
Since the calculation error of the normal-temperature converted gas pressure due to the difference between the temperature outside the container and the gas temperature can be almost eliminated, the calculation formula Pr = Pb + ΔP (−) max + ΔPImax + ΔP throughout the year.
Using the overheat determination level calculated by (+) max, abnormal overheat can be detected with high sensitivity without causing erroneous detection.

[0042]

FIG. 3 schematically shows a hardware configuration used in an embodiment of the present invention. In FIG. 3, reference numeral 20 denotes a necessary device such as a circuit breaker and a disconnector and a container filled with SF ₆ gas. It is a gas insulated switchgear (GIS) housed inside. Although not shown, the gas insulated switchgear 20 has a plurality of gas sections (containers), and the pressure sensors 1a and 1a detect the gas pressure for each of the plurality of gas sections.
.., 1k are provided. Further, outside the gas insulated switchgear, a temperature sensor 2 for detecting the air temperature around the container is arranged.

Reference numeral 3 denotes a sensor input unit for receiving the outputs of the pressure sensor and the temperature sensor. The sensor input unit is an amplifier 21 for amplifying the outputs of the pressure sensors 1a, 1b,.
, 21k, and a low-pass filter 22 that passes only low-frequency components of the outputs of these amplifiers.
a, 22b,... 22k, a signal converter 23 for converting the output of the temperature sensor 2 composed of a temperature-sensitive resistance element or the like into a voltage signal proportional to temperature, an amplifier 24 for amplifying the output of the signal converter 23, and an amplifier. And a low-pass filter 25 that passes only low-frequency components of the 24 outputs.

The outputs of the filters 22a, 22b,... And 25 are input to a multiplexer (MPX) 26, and the signals selected by the multiplexer are passed through an A / D converter 27 to a CPU 28, a memory 29, a bus line 30, and a bus line Is input to the computer 4 including a terminating impedance 31 for terminating the terminal section of the computer 4.

Using the computer and predetermined software, the normal-temperature-converted gas pressure calculating means 5, the base pressure selecting means 6, the specific-time normal-temperature converted gas pressure difference calculating means 7, and the overheating determination level calculating means 8 for winter shown in FIG. , Summer overheat determination level calculation means 9 and abnormal overheat determination means 10, or gas density coefficient calculation means 11, normal temperature conversion gas pressure calculation means 5 ', base pressure selection means 6, overheat determination level calculation means shown in FIG. 8 ′ and an abnormal overheat determining unit 10 ′ are realized.

First, the case where the function realizing means of FIG. 1 is realized by the microcomputer 4 will be described. The normal-temperature-converted gas pressure calculating means 5 receives the output Px of the pressure sensor and the output Tx of the temperature sensor as inputs, and Calculate the pressure Pnx. In this embodiment, the normal temperature is set to 20 ° C., and the normal temperature-converted gas pressure Pnx is calculated by the above equation (1). The base pressure selecting means 6 converts the normal temperature converted gas pressure calculated by the normal temperature converted gas pressure calculating means 5 at a specific time set in a time period in which the change in gas pressure due to disturbance is small and the load fluctuation is small, to a specific time normal temperature converted gas pressure. Pnp, which is calculated at the same time before the previous day, at the specific time and normal temperature converted gas pressure P
The lower one is selected as the base pressure Pb as compared with the lowest value of np. In this embodiment, the specific time (24 hour display) is 5:00.

Specific time normal temperature converted gas pressure difference calculating means 7
Is provided with a storage means for storing a specific time normal temperature converted gas pressure Pnp calculated daily, and a minimum value Pnpmi when a change in the specific time normal temperature converted gas pressure Pnp is seen throughout the year.
n and the maximum value Pnpmax are obtained, and the difference ΔPnp = Pnpma
x-Pnpmin is calculated as the gas pressure difference at a specific time and at normal temperature.

The winter superheat determination level calculating means 8 includes a base pressure Pb selected by the base pressure selecting means 6, a maximum decrease ΔP (-) max of a normal temperature converted gas pressure due to disturbance at a specific time, and a maximum load current supply. Gas pressure rise ΔPImax and maximum gas pressure rise ΔP (+) m due to disturbance
ax and the overheat judgment level P for winter
Calculate rw.

Prw = Pb + ΔP (−) max + ΔPImax + ΔP (+) max (3) Further, the summer-time overheat determination level calculation means 9 converts the winter-time overheat determination level Prw to the specific time normal temperature conversion gas pressure difference ΔPnp.
(Maximum change of year-round change of gas pressure converted to normal temperature at specific time)
Is added to calculate the summer overheat determination level Prs. This overheat determination level Prs is represented by the following equation.

Prs = Prw + ΔPnp = Pb + ΔP (−) max + ΔPImax + ΔP (+) max + ΔPnp (4) In this embodiment, the output of the pressure sensor and the output of the temperature sensor are sampled at regular intervals (for example, every 10 minutes). To calculate the normal temperature converted gas pressure Pnx. In the winter season, the normal temperature converted gas pressure Pnx is compared with the winter superheat determination level Prw, and when it is detected twice consecutively that the normal temperature converted gas pressure exceeds the overheat determination value, an abnormal overheat detection signal is generated. generate. In the summer, the normal-temperature-converted gas pressure Pnx is compared with the summer-time superheat determination level Prs, and an abnormal overheat detection signal is generated when the normal-temperature-converted gas pressure Pnx continuously exceeds the overheat determination level Prs twice.

FIG. 4 is a flowchart showing an algorithm of software for realizing each function realizing means in the embodiment of the present invention. The operation of the embodiment of the present invention will be described below with reference to this flowchart.

When the detection operation is started, first, an initial setting step S0 is performed. In this step, the continuous determination frequency N is set to 0, and an initial value of the base pressure Pb is set. The initial value of the base pressure is set to a value corresponding to the lowest value of the normal-temperature converted gas pressure measured at 5:00 in the morning before the previous day.
Next, the initial value of the base pressure Pb and the maximum decrease ΔP of the normal-temperature-converted gas pressure due to a disturbance (mainly a change in temperature) at 5 o'clock in the morning, which is measured in advance and stored in a memory, are described.
Using (−) max, the increase ΔPImax of the gas pressure when the maximum load current is applied in the daytime zone, and the maximum increase ΔP (+) max of the gas pressure due to the disturbance in the daytime, in winter according to the equation (3). The initial value of the overheating determination level Prw for summer is calculated, and the initial value of the overheating determination level Prs for summer is calculated by adding the predetermined time normal temperature converted gas pressure difference ΔPnp obtained in advance to the overheating determination level Prw.

After the above-mentioned initial setting is completed, step S1
Then, the sampling time is measured. In this embodiment, sampling is performed every 10 minutes. At the sampling time, the pressure sensors 1a to 1k are set in step S2.
And the output Tx of the temperature sensor 2 are sampled, and the sampled value of the output of the temperature sensor 2 and the sampled value of the output of the pressure sensors 1a to 1k are sequentially sent to the CPU 28 through the multiplexer 26 and the A / D converter 27. give. When the sampled value Tx of the output of the temperature sensor and the sampled value Px of the output of the pressure sensor are given to the CPU, step S3 is performed, and the normal-temperature converted gas pressure Pnx is calculated.

Next, in step S4, it is determined whether or not the current sampling time is 5:00 in the morning, and if it is 5:00 in the morning, the flow shifts to step S5 to calculate the current time (5 o'clock in the morning). The normal-temperature-converted gas pressure Pnx is set to the specific-time normal-temperature-converted gas pressure Pnp, and in step S6, Pnp is compared with the base pressure (the lowest value of the normal-temperature gas pressure calculated at 5:00 before the previous day). As a result, when Pnp <Pb, in step S7, the value of the base pressure Pb is replaced with the specific time normal temperature converted gas pressure Pnp calculated this time, and the base pressure Pb
Print the value of

Further, as a result of comparing the gas pressure Pnp converted at a specific time and ordinary temperature with the stored base pressure Pb in step S6, if Pnp ≧ Pb, the value of the base pressure Pb is not updated and the following steps S8 and S8 are performed. Step S9
Proceed to. In step S8, the base pressure Pb and ΔP (-) max
+ ΔPImax + ΔP (+) max is used to calculate the winter superheat determination level Prw, and in step S9, the summer time overheat determination level Prs is calculated by adding the specific time normal temperature converted gas pressure difference ΔPnp to Prw. Therefore, when the value of the base pressure Pb is updated at 5:00 in the morning, the values of Prw and Prs are updated.

After calculating the summer overheat determination level Prs,
Proceed to step S10. Also, as a result of the determination of the time in step S4, if the current sampling time is not 5:00 in the morning, the process proceeds to step S10.

At step S10, it is determined whether or not the present time is winter. If it is winter, the routine proceeds to step S11, where the calculated normal-temperature-converted gas pressure Pnx is compared with the overheat determination level Prw for winter. I do. If it is determined in step S10 that the current time is not winter, the normal-temperature-converted gas pressure Pnx calculated this time is compared with the summer-time superheat determination level Prs in step S12.

When Pnx ≦ Prw is satisfied in step S11 and when Pnx ≦ Prs is satisfied in step S12, the number of determinations N is set to 0 in step S13 to prepare for the next sampling. In step S11, Pnx
> Prw holds, and in step S12, Pnx
If> Prs holds, 1 is added to the value of the number of determinations N in step S14, and it is determined in step S15 whether or not the number of determinations N is equal to 2. If the number of determinations N is not equal to 2, Goes to step S1 to prepare for the next sampling.

When it is determined that N = 2 in winter and summer (when Pnx> Prw or Pnx> Prs is detected twice consecutively), it is determined that abnormal overheating has occurred. Generates an abnormal overheat detection signal. At this time, the normal temperature-converted gas pressure Pnx satisfying the condition for generating the abnormality detection signal
By determining which gas section is the pressure, the gas section in which abnormal overheating has occurred can be specified.

If Pnx> Prw or Pnx> Prs is detected only once, then Pnx ≦ Prw or Pnx ≦ Prs
Is detected, the value of N is set to 0, so that no abnormal overheat detection signal is generated.

In this embodiment, steps S4 to S7 in FIG.
1 realizes the base pressure selecting means 6 of FIG. 1, and the steps S8 and S9 realize the overheat judging level calculating means 8 for winter and the overheating judging level calculating means 9 for summer, respectively. The steps S10 to S15 implement the abnormal overheat judging means 10.

FIG. 6 is a graph showing changes in the normal-temperature converted gas pressure Pnx,
This is an example of how the overheat determination level Prw is updated every day at 5:00 in the morning. When the specific time normal temperature converted gas pressure Pnp calculated at 5 o'clock in the morning becomes lower than the minimum value of the specific time normal temperature converted gas pressure before the previous day, the base pressure Pb is updated. When the pressure drop due to is maximized, the gas pressure gradually approaches [when the pressure drop of ΔP (-) max occurs].
Therefore, the term of Pb + ΔP (−) max on the right side of the equation (3) asymptotically approaches the charged gas pressure in the container, and the overheat determination level Prw converges to the minimum necessary optimum value.

FIG. 7 shows the minimum value P5min of the normal temperature converted gas pressure at 5:00 in the morning, the maximum value P5max of the normal temperature converted gas pressure at 5:00 in the morning, the charging pressure Po of each gas section, and the base pressure Pb. This shows the relationship with the overheat determination level Prw. That is, the normal-temperature gas pressure at 5:00 in the morning is the maximum pressure rise due to the load current from the charge pressure Po to the charge pressure Po from P5min, which is obtained by subtracting the maximum pressure drop ΔP (-) max due to the disturbance expected at 5:00 in the morning. It takes a value between P5max, which is obtained by adding the component ΔPImax and the maximum pressure rise ΔP (+) max due to disturbance. The base pressure Pb becomes lower every time it is updated, and when the load current is zero, the base pressure Pb becomes lower.
b can drop to P5min. When the base pressure Pb becomes lower than the charge pressure Po, the base pressure Pb becomes ΔPImax
By simply adding ΔP (+) max and ΔP (+) max, the overheat determination level becomes too low. Therefore, in the present invention, ΔP is added to the base pressure Pb.
After adding (-) max, ΔPImax and ΔP (+) max are further added to obtain the overheat determination level Prw.

FIG. 8 shows the year-to-year changes of the overheat determination level and the gas pressure Pnp converted to the normal temperature at a specific time. Initially, the overheat determination levels Prs and Prw show relatively high values, but from the summer to winter, the specific-time normal-temperature converted gas pressure P
As np decreases, the overheat determination level decreases. When the specific-time normal-temperature converted gas pressure Pnp once reaches the minimum value Pnpmin at a certain time tw in winter, the winter overheat determination level Prw converges to the minimum value. . Overheat judgment level P for winter
After rw once converges to the minimum value, the winter overheat determination level Prw becomes constant, and the summer overheat determination level Prs is Prw
And ΔPnp.

As described above, in the abnormality detection device according to the present invention, the overheat determination level can be made to converge to the minimum necessary optimum value, so that the detection sensitivity for abnormal overheat can be greatly increased.

In the above embodiment, the calculation for updating the base pressure Ps is performed every day at 5 o'clock in the morning. However, the time for performing the calculation for updating the base pressure is determined by the gas pressure due to the disturbance. Any time may be used as long as it is a specific time set in a time zone in which the change is small and the load fluctuation is small, and may be a time other than 5:00 in the morning.

In the above embodiment, one overheating determination level is set throughout the day. However, the day is divided into daytime and nighttime, and the daytime overheating determination level and the nighttime overheating determination level are set. May be set. For example, from 6:00 to 20:50 is the daytime zone,
It is also possible to set different winter overheat determination levels and summer overheat determination levels for the daytime zone and the nighttime zone, respectively, from 0 minutes to 6:00 of the next morning as a night time zone.

In the above embodiment, the microcomputer realizes the function realizing means of FIG. 1 and sets an appropriate overheat determination level for each of winter and summer, thereby causing erroneous detection throughout the year. Although it is possible to detect abnormal overheating with high sensitivity, the overheating determination level can be set to an appropriate value throughout the year also by realizing each function realizing means of FIG. 2 using a microcomputer. Abnormal overheating can be detected with high sensitivity without causing erroneous detection.

In the case of the configuration shown in FIG. 2, the gas density coefficient calculating means 11 operates in a specific time zone (for example, from midnight to 6 am
(Time period until time), a gas pressure versus ambient temperature characteristic is obtained from the ambient temperature and the gas pressure detected by the pressure sensor and the temperature sensor, respectively, and an apparent gas density coefficient L is obtained from the gas pressure versus ambient temperature characteristic. The calculation of the gas density coefficient is preferably performed every day in a fixed time period. Also, in order to use the apparent gas density coefficient calculated immediately before when calculating the normal-temperature converted gas pressure at a specific time, the apparent gas density coefficient calculated before the specific time (for example, 5:00 am) arrives. It is preferable to terminate the calculation of the gas density coefficient.

The normal-temperature-converted gas pressure calculating means 5 'receives the detection output of the pressure sensor and the detection output of the temperature sensor as inputs,
Using the latest apparent gas density coefficient L, the gas pressure detected by the pressure sensor is converted into a gas pressure at room temperature to obtain a room temperature converted gas pressure Pnx.

The base pressure selecting means 6 sets the normal temperature converted gas pressure calculated by the normal temperature converted gas pressure calculating means 5 'at 5:00 a.m. Is compared with the lowest value of the specific time normal temperature converted gas pressure Pnp calculated at the same time, and the lower of the compared specific time normal temperature converted gas pressure is selected as the base pressure Pb.

The overheat judging level calculating means 8 'calculates the maximum decrease ΔΔ of the base pressure Pb selected by the base pressure selecting means and the normal temperature reduced gas pressure due to disturbance at a specific time.
P (-) max and increase ΔP of gas pressure when maximum load current is applied
Superheat determination level Pr = Pb + ΔP (−) max + ΔP by adding Imax and the maximum rise ΔP (+) max of gas pressure due to disturbance.
Calculate Imax + ΔP (+) max.

The abnormal overheat judging means 10 'compares the normal temperature converted gas pressure Pnx with the overheat judgment level Pr, and when the normal temperature converted gas pressure Pnx exceeds the overheat judgment level Pr, abnormal overheating occurs in the container. It is determined that there is.

As described above, when the apparent gas density coefficient is updated at any time and the normal temperature-converted gas pressure is calculated using the latest apparent gas density coefficient, the difference between the temperature outside the container and the gas temperature is calculated. The calculation error of the normal-temperature converted gas pressure caused by this can be almost eliminated. Therefore, by using the overheat determination level calculated by the arithmetic expression Pr = Pb + ΔP (−) max + ΔPImax + ΔP (+) max throughout the year, abnormal overheat can be detected with high sensitivity without causing erroneous detection.

FIG. 5 is a flowchart showing an algorithm of software when each function realizing means of FIG. 2 is realized by a microcomputer. When following this flowchart, first, an initial setting step S0 is performed. In this step, the number of continuous determinations N is set to 0, and the initial values of the base pressure Pb and the gas density coefficient L are set. As in the above-described example, the initial value of the base pressure Pb is set to a value corresponding to the lowest value of the normal-temperature converted gas pressure measured at 5:00 in the morning before the previous day. Next, the initial value of the base pressure Pb and the maximum decrease ΔP (−) max of the normal-temperature-converted gas pressure due to a disturbance (mainly a change in temperature) at 5:00 in the morning, which is measured in advance and stored in a memory, and The initial value of the winter overheat determination level Prw is calculated by the equation (3) using the gas pressure rise ΔPImax when the maximum load current is applied and the maximum gas pressure rise ΔP (+) max due to disturbance in the daytime zone. Then, the initial value of the summer-time superheat determination level Prs is calculated by adding the specific-time normal-temperature-converted gas pressure difference ΔPnp obtained in advance to the overheat determination level Prw.

After the above-mentioned initial setting is completed, step S1
Then, the sampling time (10 minutes in this example) is measured. At the sampling time, the output Px of the pressure sensors 1a to 1k and the output T of the temperature sensor 2 are determined in step S2.
x is sampled, and the sampled value of the output of the temperature sensor 2 and the sampled value of the output of the pressure sensors 1a to 1k are sequentially supplied to the CPU 28 through the multiplexer 26 and the A / D converter 27. Gas pressure sampling value P
x and the sampling value Tx of the ambient temperature are stored in a memory.

Next, in step S3, it is determined whether or not the current time zone is a specific time zone from midnight to 5:00 am
If it is determined that the time is a specific time zone, step S
The process proceeds to step S4, and if it is determined that the time is not a specific time zone, the process proceeds to step S5. In step S4, the gas pressure P sampled at an arbitrary time t1 in a specific time zone
The gas density coefficient L [= (Px1−Px) using x1 and the temperature Tx2 outside the container and the gas pressure Px2 and the temperature Tx2 outside the container sampled at an arbitrary time t2 after the time t1.
x2) / (Tx1-Tx2)], and the process proceeds to the next step S5.

In step S5, it is determined whether or not the current time is 5:00 am, and if it is 5:00 am, the flow shifts to step S6. In step S6, an average value of the gas density coefficients L calculated a plurality of times during a specific time period from midnight to 5:00 am is determined to determine the latest gas density coefficient L used when calculating the normal-temperature converted gas pressure. I do. After determining the gas density coefficient L, the process proceeds to step S7 to calculate the ordinary temperature converted gas pressure Pnx using the latest sampled values Px and Tx and the gas density coefficient L, and in step S8 this normal temperature converted gas pressure Pnx As the specific time normal temperature converted gas pressure Pnp. Next, in step S9, Pnp is set to the base pressure (the lowest value of the normal temperature gas pressure calculated at 5:00 before the previous day).
Compare with Pb. As a result, when Pnp <Pb, in step S10, the value of the base pressure Pb is replaced with the calculated gas pressure Pnp at the specific time and the normal temperature calculated this time, and a new value of the base pressure Pb is printed. Also, as a result of comparing the specific time normal temperature converted gas pressure Pnp with the stored base pressure Pb in step S9, when it is determined that Pnp ≧ Pb, the next step S11 is performed without updating the value of the base pressure Pb. To base pressure Pb and ΔP (-) max
+ ΔPImax + ΔP (+) max and the overheat determination level Pr
Is calculated. After calculating the overheat determination level Pr, the process proceeds to step S13.

If it is determined in step S5 that it is not 5:00 am, the flow advances to step S12 to calculate the ordinary-temperature converted gas pressure Pnx using the latest sampling values Px and Tx and the gas density coefficient L, and Proceed to step S13.

In step S13, the normal temperature converted gas pressure Pnx
And the overheat determination value Pr. As a result, Pnx ≦ Pr
Is satisfied, the number of determinations N is set to 0 in step S14 to prepare for the next sampling. If Pnx> Pr is satisfied in step S13, 1 is added to the value of the number of determinations N in step S15.
It is determined whether or not the number of determinations N is equal to 2, and if the number of determinations N is not equal to 2, the flow shifts to step S1 to prepare for the next sampling.

When it is determined that N = 2 in step S16 (when Pnx> Pr is detected twice consecutively), it is determined that abnormal overheating has occurred, and an abnormal overheating detection signal is generated. Let it. When Pnx> Pr is detected only once, the value of N is set to 0 the next time Pnx ≦ Pr is detected, so that no abnormal overheat detection signal is generated.

According to the flowchart shown in FIG.
The process of steps S3 to S6 implements the gas density coefficient calculating means 11 of FIG. The base pressure selection means 6 is realized by the processes of steps S7 to S10, and the overheat determination level calculation means 8 'of FIG. 2 is realized by step S11. The steps S7 and S12 realize the normal-temperature-converted gas pressure calculating means 5 'in FIG.
The abnormal overheat judging means 10 'of FIG.
Is realized.

In the flowchart shown in FIG.
The latest gas density coefficient is determined by calculating the gas density coefficient L several times in a specific time zone and taking the average value, but since the gas pressure and the temperature have a linear relationship, The gas pressure Px and the temperature T outside the container sampled at the start time and end time of a specific time zone, respectively.
The gas density coefficient may be calculated only once using the value of x.

[0084]

As described above, according to the first aspect of the present invention, the overheating judgment level is converged to the minimum necessary value in winter when the normal-temperature-converted gas pressure is calculated to be low, and the normal-temperature conversion is performed. In the summer when the gas pressure is calculated to be higher, a level obtained by adding the specific time normal temperature converted gas pressure difference ΔPnp to the overheating determination level in the winter and the overheating determination level is set, so that the overheating determination level has a minimum required margin. As a result, there is an advantage that the detection sensitivity can be increased without causing erroneous detection throughout the year.

According to the second aspect of the present invention, the gas pressure is changed from the ambient temperature and the gas pressure detected by the pressure sensor and the temperature sensor in a specific time zone in which a change in gas pressure due to disturbance is small and a load change is small. Since the apparent gas density coefficient L was obtained from the pressure vs. ambient temperature characteristic from the gas pressure vs. ambient temperature characteristic, and the latest apparent gas density coefficient L was used to calculate the normal temperature conversion gas pressure, the container Almost no calculation error of normal temperature converted gas pressure caused by the difference between outside temperature and gas temperature, overheat detection level is set to an appropriate value throughout the year, and abnormal overheat detection without erroneous detection Can be performed with high sensitivity.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of the invention described in claim 1;

FIG. 2 is a block diagram showing a configuration example of the invention described in claim 2;

FIG. 3 is a block diagram showing a configuration of hardware used in the embodiment of the present invention.

FIG. 4 is a flowchart showing an algorithm of software for realizing the function realizing means of FIG. 1;

FIG. 5 is a flowchart showing an algorithm of software for realizing the function realizing means of FIG. 2;

FIG. 6 is a diagram illustrating a state where an overheat determination level is updated in the embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a relationship among a normal-temperature converted gas pressure detected at a specific time, a base pressure Ps, and an overheat determination level Pr in the present invention.

FIG. 8 shows the change of the overheat determination level with respect to the month and the month and the change of the gas pressure of the gas insulated switchgear at room temperature with respect to the normal temperature (specific temperature normal temperature converted gas pressure) at 5:00 am FIG. 4 is a diagram showing the relationship between

FIG. 9 is a diagram showing a relationship between a gas pressure and a gas temperature and a relationship between a gas pressure and a temperature outside a container.

FIG. 10 is a diagram showing a relationship between a gas pressure at a specific time and a normal temperature in a gas insulated switchgear and a change with respect to a date;

FIG. 11 is a configuration diagram schematically showing a general configuration of an abnormal overheat detection device.

FIG. 12 is a diagram illustrating how to set an overheat determination level in a conventional abnormal overheat detection device.

[Explanation of symbols]

1, 1a to 1k Pressure sensor 2 Temperature sensor 3 Sensor input unit 4 Computer 5, 5 'Room temperature converted gas pressure calculation means 6 Base pressure selection means 8 Overheat determination level calculation means for winter 9 Overheat determination level calculation means for summer 10 ′ Abnormal overheat judging means 11 Gas density coefficient calculating means Px Gas pressure detection value Tx Temperature detection outside the vessel Pnx Px converted to normal temperature gas pressure Pnp Specific time every day (for example, 5:00 am Pb base pressure Pnpmin Minimum value of year-to-year change in normal-time converted gas pressure Pnpmax Maximum value of year-to-year change in normal-time converted gas pressure ΔPnp Specific-time normal-temperature converted gas pressure Difference ΔP (-) max Maximum drop in normal-temperature converted gas pressure due to disturbance at a specific time ΔP (+) max Above maximum gas pressure due to disturbance Increase ΔPImax Increase in gas pressure when the maximum load current is applied Pr Overheat determination level Prw Overheat determination level for winter Prs Overheat determination level for summer

Claims (2)

(57) [Scope of request for utility model registration] A pressure sensor for detecting a pressure of gas in a container of the gas insulated switchgear; a temperature sensor for detecting a temperature outside the container; and a detection output of the pressure sensor and a detection output of the temperature sensor. As an input, a calculation for converting the gas pressure detected by the pressure sensor into a gas pressure at normal temperature is performed, and a normal temperature converted gas pressure Pnx
A normal-temperature-converted gas pressure calculating means that calculates a normal-temperature-converted gas pressure at a specific time set during a time period in which a change in gas pressure due to disturbance is small and a load variation is small at a specific time It is compared with the lowest value of the specific time normal temperature converted gas pressure Pnp calculated at the same time before the previous day as the converted gas pressure Pnp, and the lower of the compared specific time normal temperature converted gas pressure is the base pressure Pb.
And a base pressure P selected by the base pressure selecting means.
b, the maximum decrease ΔP (−) max of the normal-temperature converted gas pressure due to the disturbance at the specific time, the increase ΔPImax of the gas pressure when the maximum load current is applied, and the maximum increase ΔP (+) max of the gas pressure due to the disturbance. Is added to the winter overheat determination level Prw =
Pb + ΔP (−) max + ΔPImax + ΔP (+) max winter superheat determination level calculating means; and a minimum value Pnpmin and a maximum value Pnpmax when the specific time normal temperature converted gas pressure Pnp is observed throughout the year. The difference ΔPnp = Pnpmax−Pnpmin is defined as a specific time normal temperature converted gas pressure difference, and the specific time normal temperature converted pressure difference ΔPnp is added to the winter superheat determination level Prw to calculate the summer superheat determination level Prs. Means, a constant period before and after the month when the specific time normal temperature gas pressure Pnp indicates the minimum value Pnpmin is defined as winter, and a constant period before and after the month when the specific time normal temperature gas pressure Pnp indicates the maximum value Pnpmax is defined as summer. In the winter, the normal temperature converted gas pressure Pnx is compared with the winter superheat determination level Prw, and the normal temperature converted gas pressure Pnx becomes the winter superheat determination level Prw in winter. When it is exceeded, it is determined that abnormal overheating has occurred in the container. An abnormal overheat detecting device for a gas insulated switchgear, comprising: an abnormal overheat determining means for determining that abnormal overheating has occurred in the container when the pressure exceeds Prs. 2. A pressure sensor for detecting a gas pressure in a container of the gas insulated switchgear, a temperature sensor for detecting a temperature outside the container, a specific sensor having a small change in gas pressure due to disturbance and a small load change. Gas density coefficient calculating means for obtaining a gas pressure versus ambient temperature characteristic from the ambient temperature and the gas pressure detected by the pressure sensor and the temperature sensor respectively in a time zone and obtaining an apparent gas density coefficient L from the gas pressure versus ambient temperature characteristic; And inputting the detection output of the pressure sensor and the detection output of the temperature sensor, converting the gas pressure detected by the pressure sensor into the gas pressure at room temperature using the latest apparent gas density coefficient L, A normal-temperature-converted gas pressure calculating means for obtaining a pressure Pnx; and the normal-temperature-converted gas pressure calculating means at a specific time set during a time period in which a change in gas pressure due to disturbance is small and a load change is small The specific-time normal-temperature converted gas pressure calculated by the gas-pressure calculating means is compared with the lowest value of the specific-time normal-temperature converted gas pressure Pnp calculated at the same time before the previous day as the specific-time normal-temperature converted gas pressure Pnp. The lower pressure is the base pressure Pb
And a base pressure P selected by the base pressure selecting means.
b, the maximum decrease ΔP (−) max of the normal temperature converted gas pressure due to the disturbance at the specific time, the increase ΔPImax of the gas pressure when the maximum load current is applied, and the maximum increase ΔP (+) max of the gas pressure due to the disturbance. And the overheat determination level Pr = Pb +
An overheat determination level calculating means for calculating ΔP (−) max + ΔPImax + ΔP (+) max; and comparing the normal-temperature converted gas pressure Pnx with the overheat determination level Pr to determine when the normal-temperature converted gas pressure Pnx exceeds the overheat determination level Pr. An abnormal overheat detecting device for a gas insulated switchgear, comprising: an abnormal overheat determining unit that determines that abnormal overheating has occurred in the container.