Identification of thermal overload of component of switchgear

Abstract

The invention relates to a method and a device (9) for detecting thermal overload of components of a switchgear (1), which components are arranged in a gas chamber (3) of a gas container (5) of the switchgear (1), which gas chamber is filled with an insulating gas and in which at least one current (I) flows through an electrical conductor (7). In the method, a gas pressure (p) in the gas chamber (3) is measured and a comparison value (f) for the gas pressure (p) in the gas chamber (3) is determined. If the gas pressure (p) significantly exceeds the comparison value (f), it is concluded that at least one component of the switching device (1) arranged in the gas chamber (3) is thermally overloaded.

Description

TECHNICAL FIELD

[0001] The invention relates to a method and a device for identifying a thermal overload of components of a switching device, which components are arranged in a gas chamber of a gas vessel of the switching device, which is filled with an insulating gas, in which gas chamber at least one electric current flows through electric conductors. BACKGROUND

[0002] So far, the temperature in the gas chamber of a switching device has been collected at most locally. For example, the temperature in the gas chamber is measured locally by means of wireless sensors, or individual components in the gas chamber are monitored by means of infrared sensors, which are arranged at a safe distance with respect to the live parts. Temperature determinations are also known for cables and insulating bushings. However, such local temperature measurements cannot monitor the entire current path inside the gas chamber. Monitoring the entire current path by means of local temperature measurements requires a very large number of measuring points and thus also a very large number of temperature sensors, which would make the measuring system very complex and cost-intensive. SUMMARY

[0003] The invention is to solve the technical problem of giving an improved method and an improved device for identifying a thermal overload of components of a switching device, which components are arranged in a gas chamber of a gas vessel of the switching device, which is filled with an insulating gas, in which gas chamber at least one electric current flows through electric conductors.

[0004] According to the invention, the above-mentioned technical problem is solved by a method having the features of claim 1 and by a device having the features of claim 13.

[0005] Advantageous design solutions of the invention are the subject of the dependent claims.

[0006] The method according to the invention serves to identify a thermal overload of components of a switching device, which components are arranged in a gas chamber of a gas vessel of the switching device, which is filled with an insulating gas, in which gas chamber at least one electric current flows through electric conductors. In the method, the gas pressure in the gas chamber is measured. Furthermore, a comparison value for the gas pressure in the gas chamber is determined. When the gas pressure significantly exceeds the comparison value, it is concluded that at least one component of the switching device, which is arranged in the gas chamber, is subject to a thermal overload.

[0007] The application makes use of the fact that a temperature increase of the insulating gas in the gas chamber leads to a pressure increase in the gas chamber, since the volume of the gas chamber and the mass of the insulating gas in the gas chamber are constant and thus, according to the thermal state equation of an ideal gas, the temperature of the insulating gas is proportional to the gas pressure in the gas chamber. Here, a local temperature increase directly influences the gas pressure in the entire gas chamber, so that a temperature increase at a location in the gas chamber remote from the pressure sensor can also be detected by the pressure sensor used to measure the gas pressure. Thus, a single pressure sensor is sufficient for thermal monitoring of the entire gas chamber. The comparison value is a value taken by the gas pressure when no thermal overload occurs in the gas chamber. Thus, a gas pressure measured in the gas chamber that significantly exceeds the comparison value indicates that at least one component of the switching device in the gas chamber is thermally overloaded.

[0008] In one design of the application, all currents flowing in the gas chamber are measured and the comparison value is determined depending on the currents. Additionally, the ambient temperature of the environment of the switching device can be measured and the comparison value can also be determined depending on the ambient temperature.

[0009] The design of the application mentioned at the outset takes into account that the currents flowing in the gas chamber influence the temperature and thus the gas pressure in the gas chamber, since heat is transferred from the conductors in which the currents flow to the insulating gas. Thus, a temperature increase of the insulating gas caused solely by the currents does not indicate a thermal overload of a component of the switching device and must be taken into account when determining the comparison value. In other words, the comparison value must be determined depending on the currents flowing in the gas chamber in order to avoid a false interpretation of a pressure increase in the gas chamber. The same applies to the ambient temperature of the environment of the switching device, since the heat output from the gas chamber to the environment depends on the ambient temperature. However, since the ambient temperature is often at least approximately constant, the influence of the ambient temperature can often be neglected.

[0010] In another design of the application, the comparison value is determined by a transfer function depending on at least two time terms, wherein a first time term describes the heat transfer from the electrical conductor to the insulating gas in the gas chamber and a second time term describes the heat transfer from the insulating gas in the gas chamber to the environment of the switching device.

[0011] The design of the application mentioned at the outset also takes into account the influence of the currents flowing in the gas chamber and the ambient temperature already mentioned above on the temperature of the insulating gas and thus on the gas pressure in the gas chamber.

[0012] In another design of the application, use is made of The comparison value is determined by means of a differential equation which takes into account that the temperature of the insulating gas in the gas chamber can be described as a function of time by a differential equation, into which the heat transfer from the electrical conductor to the insulating gas and from the gas chamber to the environment of the switchgear is incorporated. The differential equation can be solved, as appropriate, by means of a transfer function of the differential equation, into which the mentioned heat transfer is incorporated.

[0013] In another design of the application, the comparison value is determined by means of a thermodynamic simulation of the gas chamber, coupled with a flow simulation of the flow of the insulating gas in the gas chamber. Here, the thermodynamic simulation and the flow simulation can take into account, in particular, a location-dependent relationship of the heat transfer from the electrical conductor in the gas chamber to the insulating gas.

[0014] The aforementioned design of the application aims at an exact determination of the comparison function, which takes into account, for example, also the geometry of the gas chamber and the course of the electrical conductor in the gas chamber. For this purpose, this design of the application is provided with a corresponding thermodynamic simulation of the gas chamber and coupled with a flow simulation of the flow of the insulating gas in the gas chamber.

[0015] In another design of the application, the temperature is measured at at least one location in the gas chamber and the measured temperature is used in the calculation of the comparison value. The temperature measured in the gas chamber can be used as a boundary value or support value in the determination of the comparison value and can advantageously improve the accuracy of the determination.

[0016] In another design of the application, the gas pressure is likewise measured separately in further gas chambers of the switchgear which are filled with insulating gas, and the comparison value is determined in dependence on the gas pressures in these further gas chambers. For example, the average of the gas pressures in these further gas chambers is determined as the comparison value.

[0017] The aforementioned design of the application takes into account that the switchgear often comprises a plurality of identical or at least similar gas chambers which are each filled with insulating gas. The comparison value for a gas chamber can therefore also be determined in dependence on the gas pressure in further gas chambers having similar properties. In particular, the comparison value can be determined as the average of the gas pressures in these further gas chambers when the electrical currents in these gas chambers are also identical or similar. Otherwise, the comparison value is also determined in dependence on the electrical currents flowing in these further gas chambers.

[0018] In another design of the application, a difference threshold value is defined for the gas pressure in the gas chamber exceeding the comparison value, and the gas pressure exceeding the comparison value is assessed as significant when it exceeds the comparison value by more than the difference threshold value.

[0019] ​In another design of the application, a ratio threshold is defined for the ratio of the gas pressure in the gas chamber to the comparison value, and the gas pressure exceeding the comparison value is assessed as significant when the ratio of the gas pressure in the gas chamber to the comparison value exceeds the ratio threshold.

[0020] The two design of the application mentioned above enable a quantitative assessment of the gas pressure in the gas chamber by a threshold value related to the comparison value for the absolute or relative deviation of the gas pressure from the comparison value.

[0021] The application relates to a device for identifying a thermal overload of a component of a switching device, which component is arranged in a gas chamber of a gas vessel of the switching device, which is filled with an insulating gas, in which gas chamber at least one electric current flows through an electric conductor, the device comprising a pressure sensor configured to measure a gas pressure in the gas chamber, and a computing unit configured to determine a comparison value for the gas pressure in the gas chamber and to conclude that a thermal overload of at least one component of the switching device arranged in the gas chamber has occurred when the gas pressure significantly exceeds the comparison value.

[0022] The device according to the application enables the method according to the application to be carried out. The advantages of the device thus correspond to the advantages of the method according to the application mentioned above. BRIEF DESCRIPTION OF DRAWINGS

[0023] The features, characteristics and advantages of the application described above, as well as the implementation thereof, will become more apparent and more easily understood in connection with the description of embodiments, which are explained in detail below in conjunction with the attached drawings. Herein, in the drawings:

[0024] Figure 1 A block diagram of a switching device and a device for identifying a thermal overload of a component of the switching device is shown,

[0025] Figure 2 The time courses of the temperature and the gas pressure in the gas chamber of the switching device, the ambient temperature in the environment of the switching device and the comparison value for the gas pressure are shown.

[0026] In the drawings, parts that correspond to one another are provided with the same reference signs. DETAILED DESCRIPTION

[0027] Figure 1 (ATTACHMENT Figure 1) a block diagram of a switching device 1 and of an apparatus 9 for identifying a thermal overload of components of the switching device 1 is shown. The switching device 1 comprises a gas chamber 3 of a gas vessel 5 filled with an insulating gas and an electrical conductor 7 extending into the gas chamber 3. The apparatus 9 comprises a current sensor 11, a pressure sensor 13, a temperature sensor 15 and a computing unit 17. The current sensor 11 is configured for measuring an electrical current I flowing in the conductor 7. The pressure sensor 13 is configured for measuring a gas pressure p in the gas chamber 3. The temperature sensor 15 is configured for measuring an ambient temperature of an environment of the switching device 1. The computing unit 17 is configured for determining a comparison value f for the gas pressure p according to a method described below and for concluding a thermal overload of at least one component of the switching device 1 arranged in the gas chamber 3 when the measured gas pressure p significantly exceeds the comparison value f.

[0028] In the following, embodiments of a method for acquiring a thermal overload of components of a switching device 1 arranged in a gas chamber 3 according to the present application are described. Figure 2

[0029] Figure 2 (attachment Figure 2 ) a temperature T of the insulating gas and a gas pressure p in the gas chamber 3, an ambient temperature of an environment of the switching device 1 and a comparison value f for the gas pressure p are shown with respect to time t.

[0030] The gas pressure p in the gas chamber 3 and the ambient temperature of an environment of the switching device 1 are measured.

[0031] The comparison value f is a calculated value of the gas pressure in the gas chamber 3 in the absence of an error, i.e. in the absence of a thermal overload in the gas chamber 3. The comparison value f is calculated, for example, in the manner described below, using terms, the transfer function of which depends on two time terms, wherein a first time term describes a heat transfer from the conductor 7 to the insulating gas in the gas chamber 3 and a second time term describes a heat transfer from the insulating gas in the gas chamber 3 to the environment of the switching device 1.

[0032] The heat transfer from the conductor 7 to the insulating gas in the gas chamber 3 depends on a loss power of the conductor 7. A part of this loss power is output from the conductor 7 to the insulating gas in the gas chamber 3. Heat is output from the insulating gas in the gas chamber 3 to the environment of the switching device 1, which heat depends on the ambient temperature of the environment. The comparison value f as a function of time therefore depends on the loss power as a function of time and on the ambient temperature ​The relationship between T, P and T is described, for example, by the following equations [1], [2], [3]: , and

[0033]

[0034]

[0035]

[0036] Here, the following symbols are used:

[0037] : heat capacity of the conductor 7

[0038] : heat capacity of the insulating gas

[0039] : temperature of the conductor 7

[0040] : thermal resistance between the conductor 7 and the insulating gas

[0041] : thermal resistance between the insulating gas and the environment

[0042] V: volume of the gas chamber 3

[0043] n: amount of substance of the insulating gas

[0044] R: universal gas constant

[0045] :derivative with respect to time t

[0046] : derivative of T with respect to time t Equation [1] describes the loss power in relation to T,

[0047] and T. Equation [2] describes the relationship between T, P and T, and is used to replace P in equation [1]. This provides a second-order differential equation for the temperature T as a function of time t, the loss power P as a function of time and the ambient temperature T as a function of time being incorporated therein. Equation [3] is the thermal state equation of an ideal gas, wherein the comparison value f is the pressure. Equation [3] is used to replace P in equation [2] with ​​​​​​​​​This is perfectly fine, because the volume V of gas chamber 3 and the mass n of the insulating gas are constant over time. From this, we obtain the second-order differential equation for the comparison value f(t) as a function of time t, and the power loss as a function of time. and ambient temperature as a function of time It is included in it. For example, by utilizing We use terms to solve this differential equation. Therefore, the solution to this differential equation is... It can be understood as a function It depends on the power loss as a function of time. and ambient temperature as a function of time :

[0048]

[0049] Ambient temperature It is often approximately independent of time, so it can be replaced by a constant value. Power loss It is usually approximated by the square of the current I flowing through conductor 7 and the ohmic resistance of conductor 7. product Proportional. The comparison value f thus depends essentially on the square of the current I.

[0050] The comparison value f is used to identify thermal overload of a component of the switchgear 1 arranged in the gas chamber 3. Here, when the measured gas pressure p significantly exceeds the comparison value f, it is inferred that at least one component of the switchgear 1 arranged in the gas chamber 3 has experienced thermal overload. For example, a difference threshold is defined for the gas pressure p in the gas chamber 3 exceeding the comparison value f, and when the gas pressure p exceeds the comparison value f by more than this difference threshold, the gas pressure p exceeding the comparison value f is assessed as significant. Alternatively or additionally, a ratio threshold is defined for the ratio of the gas pressure p in the gas chamber 3 to the comparison value f, and when the ratio of the gas pressure p in the gas chamber 3 to the comparison value f exceeds this ratio threshold, the gas pressure p exceeding the comparison value f is assessed as significant.

[0051] Figure 2 An example is shown showing the gas pressure in the measured gas chamber 3. Comparison values The calculation results are shown. The average temperature of the insulating gas in gas chamber 3 is also presented. and ambient temperature It can be clearly seen that the gas pressure Without a large time delay, the temperature of the insulating gas in gas chamber 3... The pressure changes proportionally. In this example, the gas pressure... Comparison value The results were very consistent, leading to the conclusion that the components of the switching device 1 located in the gas chamber 3 did not experience thermal overload.

[0052] The calculation of the comparison value described above is merely an example of the calculation of the comparison value under simple or simplified assumptions. In reality, for example, the gas container 5 may also have associated thermal mass, which must be taken into account when performing the calculation. In addition, for example, the positional dependence of heat transfer from conductor 7 to the insulating gas in gas chamber 3 can be considered, and / or the presence of multiple conductors 7 in gas chamber 3 can be considered if necessary. In these cases, the comparison value f is determined, for example, by performing a thermodynamic simulation of gas chamber 3 coupled with a flow simulation of the flow of insulating gas in gas chamber 3. Here, other data sources can also be considered, such as the measurement signal of a temperature sensor arranged in gas chamber 3. The calculation of the comparison value f can then be performed, for example, depending on the position, thereby replacing equation [4], the calculation according to equation [5] provides the result:

[0053]

[0054] Here, x represents the position coordinate and the power loss. The comparison value f depends on the position coordinates, and This represents the temperature in gas chamber 3, acquired by a temperature sensor. In this case, for example, the gas pressure p in gas chamber 3 is measured at multiple locations, and the value of gas pressure p is compared with a comparison value f calculated for the corresponding location. Alternatively, the average value f is calculated with respect to the location coordinate x. The value is used as a comparison value .

[0055] Alternatively, the comparison value f can be determined in other ways. When the switchgear 1 has other gas chambers filled with insulating gas, the gas pressure can be measured separately in these other gas chambers, and the comparison value f can be determined based on the gas pressure in these other gas chambers. For example, the average value of the gas pressure in these other gas chambers can be determined as the comparison value f.

[0056] Although the invention has been shown and described in further detail through preferred embodiments, the invention is not limited to the disclosed examples, and those skilled in the art can derive other variations therefrom without departing from the scope of protection of the invention.

[0057] Regardless of the grammatical gender of a particular term, people with either male or female gender identity are included.

[0058] List of reference numerals

[0059] 1 Switchgear

[0060] 3 gas chambers

[0061] 5 Gas Containers

[0062] 7 conductors

[0063] 9. Device for identifying thermal overload of components of switching equipment

[0064] 11 Current Sensor

[0065] 13 pressure sensors

[0066] 15 Temperature Sensors

[0067] 17 computing units

[0068] f-comparison value

[0069] I current

[0070] p gas pressure

[0071] t time

[0072] Temperature

[0073] Ambient temperature

Claims

1. A method for identifying thermal overload of a component of a switching device (1), said component being arranged in a gas chamber (3) filled with insulating gas in a gas container (5) of said switching device (1), wherein at least one current (I) flows in an electrical conductor (7) in said gas chamber, wherein, - Measure the gas pressure (p) in the gas chamber (3). - Determine the comparison value (f) for the gas pressure (p) in the gas chamber (3), and - When the gas pressure (p) significantly exceeds the comparison value (f), it is inferred that at least one component of the switching device (1) arranged in the gas chamber (3) is thermally overloaded.

2. The method according to claim 1, wherein, Measure all currents (I) flowing through the gas chamber (3) and determine the comparison value (f) based on the currents (I).

3. The method according to claim 2, wherein, Measure the ambient temperature of the environment of the switching device (1) ), and based on the current (I) flowing through the gas chamber (3) and the ambient temperature ( Determine the comparison value (f).

4. The method according to any one of the preceding claims, wherein, The comparison value (f) is determined by a transfer function that depends on at least two time terms, wherein the first time term describes the heat transfer from the electrical conductor (7) to the insulating gas in the gas chamber (3), and the second time term describes the heat transfer from the insulating gas in the gas chamber (3) to the environment of the switching device (1).

5. The method according to any one of the preceding claims, wherein, use The term is used to determine the comparison value (f).

6. The method according to any one of claims 1 to 4, wherein, The comparison value (f) is determined by performing a thermodynamic simulation of the gas chamber (3) coupled with a flow simulation of the flow of the insulating gas in the gas chamber (3).

7. The method according to claim 6, wherein, The thermodynamic simulation and the flow simulation consider the positional dependence of heat transfer from the electrical conductor (7) in the gas chamber (3) to the insulating gas.

8. The method according to any one of the preceding claims, wherein, Temperature is measured at at least one location in the gas chamber (3), and the measured temperature is used when determining the comparison value (f).

9. The method according to claim 1, wherein, Gas pressure is also measured in another gas chamber filled with insulating gas in the switchgear (1), and a comparison value (f) is determined based on the gas pressure in the other gas chamber.

10. The method according to claim 9, wherein, The average gas pressure in the other gas chamber is determined as the comparison value (f).

11. The method according to any one of the preceding claims, wherein, A difference threshold is defined for the gas pressure (p) in the gas chamber (3) exceeding the comparison value (f), and when the gas pressure (p) exceeds the comparison value (f) beyond the difference threshold, the gas pressure (p) exceeding the comparison value (f) is assessed as significant.

12. The method according to any one of the preceding claims, wherein, A ratio threshold is defined for the ratio of gas pressure (p) in the gas chamber (3) to the comparison value (f), and when the ratio of gas pressure (p) in the gas chamber (3) to the comparison value (f) exceeds the ratio threshold, the gas pressure (p) exceeding the comparison value (f) is assessed as significant.

13. A device (9) for identifying thermal overload of a component of a switching device (1), said component being arranged in a gas chamber (3) filled with insulating gas in a gas container (5) of said switching device (1), wherein at least one current (I) flows in an electrical conductor (7) in said gas chamber, said device (9) comprising: - Pressure sensor (13) is configured to measure the gas pressure (p) in the gas chamber (3), and - The calculation unit (17) is configured to determine a comparison value (f) for the gas pressure (p) in the gas chamber (3) and to infer that at least one component of the switching device (1) arranged in the gas chamber (3) is thermally overloaded when the gas pressure (p) significantly exceeds the comparison value (f).

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