Gas monitoring system and corresponding method

Abstract

The present invention relates to a gas monitoring system, comprising: a gas insulated switchgear (1), the gas insulated switchgear comprising a chamber (4), the chamber being filled with an insulating gas (5) surrounding a high voltage or medium voltage component (6); a sensor (2), the sensor being operatively connected to the chamber (4) and being adapted to measure a physical property of the insulating gas (5) in the chamber (4) over a period of time; and a computer unit (3), the computer unit being adapted to perform statistical step detection on a measurement value of the sensor (2) to determine whether a jump has occurred, and / or to perform statistical change detection to determine whether a change has occurred, wherein the statistical step detection and / or statistical change detection comprises confirming an expected range based on past sensor measurement values ​​and checking whether a current sensor measurement value is outside the expected range.

Description

Technical Field

[0001] The invention relates to a gas monitoring system comprising: a gas insulated switchgear comprising a chamber filled with an insulating gas surrounding a high voltage or medium voltage component; and a sensor operatively connected to the chamber and adapted to measure a physical property of the insulating gas in the respective chamber over a period of time. The invention also relates to a corresponding method for a gas insulated switchgear comprising a chamber filled with an insulating gas surrounding a high voltage or medium voltage component, the method comprising the step of measuring a physical property of the insulating gas in the respective chamber over a period of time. Background Art

[0002] Gas insulated switchgear, i.e. GIS, is usually operated at medium voltage of 10kV to 100kV and / or high voltage of 100kV to 1200kV. In order to insulate high or medium voltage components, such as disconnectors, fuses and / or circuit breakers, GIS is filled with insulating gas, such as air or SF6. Other gases are also in use and are currently being developed by different manufacturers. However, SF6 is generally the gas of choice for high voltage applications due to various advantages. The symmetrical arrangement of molecules leads to great stability and very high dielectric capacity. Therefore, at atmospheric pressure, SF6 has a dielectric strength of about three times that of air. Therefore, GIS using SF6 as insulating gas can be much more compact than equipment using air as the insulating medium. In addition, SF6 is a "self-repairing" dielectric because SF6 is largely not damaged by breakdown. This makes SF6 very suitable for use as an interruption medium.

[0003] On the other hand, SF6 is also considered a very potent greenhouse gas. The U.S. Environmental Protection Agency reports that SF6 has an atmospheric lifetime of approximately 3,200 years and a global warming potential (100-year range) that is 23,900 times that of carbon dioxide. Therefore, the use of SF6 is strictly controlled and regulated. Manufacturing defects within GIS may cause SF6 leakage, which affects the environment and at the same time degrades the insulation performance of the GIS. Losing too much insulating gas can have potentially catastrophic effects due to uncontrolled discharges.

[0004] EP 3 790 032 A1 describes a method for monitoring a circuit breaker containing a gas having at least one gas property having a provided value, the method comprising the following steps: a) collecting a data set relating to at least one gas property within the circuit breaker, wherein the data set comprises the values ​​of the at least one gas property under specific conditions or during specific times of the day, b) calculating the standard deviation of the at least one gas property of the data set for at least 3 days out of the last 10 days, c) comparing the standard deviation of the gas pressure with a predetermined threshold, d) triggering a first action if the standard deviation exceeds the threshold.

[0005] In order to avoid this problem, existing gas monitoring systems for gas insulated switchgear have been developed which are used to typically monitor the density and / or pressure of the system. Based on these measured values, a leakage rate is calculated. In order to improve the accuracy of this leakage rate calculation, the system can take into account, for example, the last four weeks of measurements and / or data points. If gas handling operations occur or if the load changes, in particular the gas compartment in the voltage transformer, this leads to an immediate change in the initially measured gas pressure and / or density. Such very rapid pressure changes can lead to an erroneously calculated leakage rate, thereby causing unnecessary alarms and warnings, which is inconvenient for the continuous operation of the GIS. Summary of the invention

[0006] It is therefore an object of the present invention to provide an improved gas monitoring system and a corresponding method for preventing such "false alarms".

[0007] The objects of the invention are solved by the features of the independent claims. Preferred embodiments are described in detail in the dependent claims.

[0008] Therefore, the object is solved by a gas monitoring system comprising:

[0009] A gas-insulated switchgear comprising a chamber filled with an insulating gas surrounding a high-voltage or medium-voltage component,

[0010] a sensor operatively connected to the chamber and adapted to measure a physical property of the insulating gas in the corresponding chamber over a period of time, and

[0011] A computer unit is adapted to perform statistical step detection on the sensor measurement values ​​to determine if a jump has occurred and / or to perform statistical change detection on the sensor measurement values ​​to determine if a change has occurred.

[0012] The key point of the proposed solution is therefore the automatic detection of sudden changes in gas handling or other physical properties, such as, for example, changes in the pressure and / or density values ​​of the insulating gas. In this case, as described below, it can then be decided whether to restart the leakage rate calculation, or whether the jump and / or change constitutes a "false alarm" that can be removed from the measurement data, such as in the case of voltage transformers as high- or medium-voltage components. In this way, unnecessary alarms and warnings are drastically reduced or even eliminated.

[0013] Thus, unlike prior art systems, after a gas handling operation, such as, for example, refilling with insulating gas, it is not necessary to specifically manually restart the leakage rate and / or trend calculation algorithms, such as, for example, HAPG and the competition algorithm. Similar problems may occur in the gas compartment of a voltage transformer, wherein the gas pressure and / or density depends to a great extent on the load of the voltage transformer. Thus, if a line related to the voltage transformer is connected or disconnected, the pressure and / or density changes in a significantly increasing and / or decreasing manner, i.e., in a jump-like manner, respectively. Such jumps have a similar effect to a refill and may lead to false alarms, which are avoided in a very convenient manner by the proposed solution.

[0014] In other words, the proposed solution essentially increases the occurrence of jump and / or change detection, in particular before the subsequent actual leakage rate and / or trend calculation. The proposed jump and / or change detection can look at past measurements to confirm whether the current measurement constitutes a jump and / or change. Jump and / or change detection can confirm the expected range based on past measurements, and can check whether the current, especially the most recent measurement, is outside the expected range. In particular, statistical step detection and / or statistical change detection can include: confirming the expected range based on past sensor measurements, and checking whether the current sensor measurement is outside the expected range. If the current sensor measurement is outside the expected range, a jump and / or change may be detected, and the jump and / or change can be excluded by adding an offset to the measurement as described below.

[0015] In the embodiments of the prior art, the problem of leakage rate calculation has been observed in the real world due to gas handling and after causing jumps in the gas compartment of the voltage transformer, in which the pressure and / or density depends largely on the load of the line, especially the power-on. With the proposed solution, multiple recent data points can be used instead of new data points to detect jumps and / or changes. Thus, the jump and / or step detection threshold can be calculated using past measurements or given by a predefined configuration. Generally, for all compartments except the voltage transformer, an upward jump indicates refilling. A downward jump indicates a large leak or removal of gas. Therefore, a downward jump may trigger a leakage alarm. For the voltage transformer, an upward jump may be a refill or power-on event. A downward jump may be caused by a huge leak or power outage. A downward jump caused by a power outage should not cause a leakage alarm. The proposed solution provides detection of these pressure drop events in order to avoid false alarms.

[0016] The gas insulated switchgear, i.e. GIS, is preferably configured for operation in a medium voltage range of 10 kV to 100 kV and / or in a high voltage range of 100 kV to 1200 kV. The chamber preferably provides airtightness and / or comprises a metal housing encapsulating medium voltage or high voltage components. The medium voltage or high voltage components are exemplarily provided as circuit breakers, fuses, disconnectors, etc. The measured physical properties may include pressure, density, sound velocity, diffraction, etc. There may be a single sensor, as well as multiple sensors, which may measure the same or different physical properties. The term "over a period of time" preferably refers to that the sensor measures continuously, for example continuously over one day, two days or more. The computer unit may be provided as any computerized device, such as, for example, a microprocessor.

[0017] Statistical step detection, also known as step smoothing, step filtering, offset detection, jump or edge detection, is preferably understood as the process of finding sudden changes in the mean level of the measured values. Statistical step detection is preferably performed as the measured data arrive, preferably using so-called online algorithms. Statistical change detection preferably involves identifying when a probability distribution of a random process or time series changes.

[0018] According to a preferred embodiment, if a jump and / or change occurs, the computer unit is adapted to:

[0019] a) Reset the insulation gas leakage rate calculation in the chamber, or

[0020] b) Remove jumps and / or changes by applying an offset to the sensor measurements.

[0021] Thus, in the case of a jump and / or change detected, the leakage rate and / or trend calculation can be automatically reset and reinitialized accordingly. This situation may be limited to jumps and / or changes that increase physical properties, such as, for example, refilling does not generally reduce physical properties, such as, for example, gas pressure. Alternatively, in the case where physical properties such as, for example, pressure and / or density depend on, for example, line load or other parameters, such as, for example, gas compartments in voltage transformers, jumps and / or changes can be removed from the measured values. In this case, in particular before applying the leakage rate calculation, an offset can be applied, which removes the jumps and / or changes. The offset is preferably equal to a value that substantially balances the jumps and / or changes in the measured values. Thus, the leakage rate calculation can be continued without the need to reinitialize and reset the leakage rate calculation algorithm accordingly.

[0022] In another preferred embodiment, the computer unit is adapted to:

[0023] c) When it is determined that a jump has occurred, decide to perform a) or b) based on the height of the jump and / or the direction of the jump and / or the additional measurement signal indicating the state of the gas-insulated switchgear.

[0024] Particularly for embodiments comprising a gas compartment where b) is possible, such as a voltage transformer for example, it is advantageous to decide whether option a) or b) should be selected. This decision can be made based on at least one of the following parameters: the height of the jump; the direction of the jump, for example, since the pressure change of the voltage transformer upon energization is alternating, so that after an upward jump the next jump will be a downward jump; an additional measurement signal indicating a state, such as the voltage of the voltage transformer as an analog value or a binary value.

[0025] In another preferred embodiment, the computer unit is adapted to:

[0026] d) Calculate the leakage rate of the insulating gas in the chamber.

[0027] Such calculation is preferably performed after the decisions a) and b) are made. The calculation of the leakage rate of the insulating gas may include the calculation of a predicted leakage rate for the future. Such a prediction allows a strict inventory of gases that are controlled by environmental standards or are very expensive. In addition, the operator of the GIS is able to identify a time in the future from which the operation of the GIS may become dangerous and the GIS requires maintenance. For example, the leakage of an insulating gas such as SF6 may affect the environment and at the same time reduce the insulation performance of the GIS. Therefore, the loss of too much insulating gas may lead to potentially catastrophic effects due to uncontrolled discharges.

[0028] According to another preferred embodiment, the jump and / or change is characterized by a measured value ≥ 1.5, 2.0, 2.5, 5.0 or 10.0 of the standard deviation of the measured values ​​of the last hour, the last two hours, the last day or the last two days. Alternatively, the standard deviation of the measured values ​​of the last 12 hours, the last 18 hours, the last 5 days or the last 10 days can be considered. In this way, precise measurement rules are defined to decide whether a jump and / or change has occurred.

[0029] In another preferred embodiment, statistical change detection includes sequentially discounting an autoregressive time series model. Such an autoregressive model means that a time series model is preferably constructed to predict current measurements based on past measurements in the same univariate time series. In addition, other statistical change detection algorithms known to those skilled in the art may also be used.

[0030] According to a further preferred embodiment, the physical property of the insulating gas is indicative of the density of the insulating gas in the chamber. In this way, the sensor is preferably provided as a density measuring sensor.

[0031] In another preferred embodiment, the gas insulated switchgear comprises a voltage transformer. The voltage transformer VT, also known as a potential transformer PT, is generally understood as a shunt-type instrument transformer. The voltage transformer is generally designed to provide a negligible load to the power source being measured and has a precise voltage ratio and phase relationship to achieve accurate secondary connection metering.

[0032] In general, there are various possibilities for the insulating gas. However, according to a preferred embodiment, the insulating gas is SF6. Sulfur hexafluoride, i.e. SF6, has traditionally been the insulating gas of choice in high voltage applications. The symmetrical arrangement of the molecules results in great stability and very high dielectric capacity. At atmospheric pressure, SF6 has a dielectric strength of about three times that of air. Therefore, a GIS using SF6 as an insulating gas can be much more compact than equipment using air as an insulating medium. In addition, SF6 is a "self-repairing" dielectric because SF6 is largely not damaged by breakdown. This makes SF6 very suitable for use as an interruption medium. In addition to SF6, other insulating gases are being developed as more climate-friendly alternatives to SF6, which can also be used in the proposed solution.

[0033] The object is permanently solved by a method for detecting jumps and / or changes in a gas-insulated switchgear comprising a chamber filled with an insulating gas surrounding a high-voltage or medium-voltage component, the method comprising the following steps:

[0034] measuring the physical properties of the insulating gas in the corresponding chamber over a period of time, and

[0035] Statistical step detection is performed on the sensor measurements to determine if a transition has occurred and / or statistical change detection is performed to determine if a change has occurred.

[0036] According to a preferred embodiment, if a jump and / or change occurs, the method comprises the following steps:

[0037] a) Reset the insulation gas leakage rate calculation in the chamber, or

[0038] b) Removing the jumps and / or changes by applying an offset to the sensor measurements.

[0039] In another preferred embodiment, the method comprises the following steps:

[0040] c) When it is determined that a jump has occurred, decide to perform a) or b) based on the height of the jump and / or the direction of the jump and / or the additional measurement signal indicating the state of the gas-insulated switchgear.

[0041] According to another preferred embodiment, the method comprises the following steps:

[0042] d) Calculate the leakage rate of the insulating gas in the chamber.

[0043] In another preferred embodiment, the jump and / or change is characterized by a measured value ≥ 1.5, 2.0 or 2.5 of the standard deviation of the measured values ​​of the last hour, last two hours, last day or last two days.

[0044] According to another preferred embodiment, statistical change detection comprises sequentially discounting an autoregressive time series model.

[0045] In another preferred embodiment, the physical property of the insulating gas is indicative of the density of the insulating gas in the chamber.

[0046] Other embodiments and advantages of the method may be directly and clearly derived by a person skilled in the art from the system described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0048] In the attached picture:

[0049] Figure 1 A gas monitoring system according to an exemplary embodiment is shown in schematic form. DETAILED DESCRIPTION

[0050] Figure 1A gas monitoring system according to an exemplary embodiment is shown in schematic form.

[0051] The gas monitoring system comprises a gas insulated switchgear 1, a sensor 2 and a computer unit 3. The gas insulated switchgear 1 comprises a tubular gastight chamber 4 filled with an insulating gas 5 surrounding a high or medium voltage component 6. The insulating gas 5 is provided as sulfur hexafluoride, SF6, while other insulating gases having similar interrupting capabilities may be used.

[0052] The high or medium voltage component 6 is provided as a voltage transformer. The sensor 2 is provided as a pressure sensor and is operatively connected to the chamber 4 for measuring the pressure as a physical characteristic of the insulating gas 5 in the chamber 4 over a period of time. Figure 1 Only one chamber 4 is shown, but the gas insulated switchgear 1 may comprise three or more chambers 4 , one for each phase and each filled with an insulating gas 5 surrounding a high or medium voltage component 6 and each equipped with a respective sensor 2 .

[0053] The computer unit 3 includes a microprocessor or similar computing device and is configured to perform statistical step detection on the sensor measurement values ​​to determine if a jump has occurred, and / or statistical change detection to determine if a change has occurred. Thus, if the most recent measurement value is ≥ 1.5, 2.0 or 2.5 of the standard deviation of the measurement values ​​of the last hour, last two hours, last day or last two days, the computer unit 3 determines that a jump and / or change has occurred.

[0054] In this case, the computer unit 3 decides whether: a) the already performed leakage rate calculation of the insulating gas 5 in the chamber 4 is reset and reinitialized accordingly, or b) the detected jump and / or change is removed by applying a corresponding offset to the sensor measurement value and the leakage rate calculation is then continued. In the latter case, the offset is therefore applied before the leakage rate calculation is performed in order to counteract the jump and / or change.

[0055] Step b) is possible for a gas compartment comprising a voltage transformer such that the decision can be made based on one of: the height of the jump and / or change; the direction of the jump and / or change, for example, since the pressure change of the voltage transformer upon energization is alternating, wherein, after an upward jump, the next jump will be a downward jump; or an additional measurement signal indicating a state, such as for example the voltage of the voltage transformer, for example as an analog value or a binary value.

[0056] Once the offset is applied, the leakage rate of the insulating gas 5 in the chamber 4 can be continuously calculated. The size of the offset is selected to equalize jumps and / or changes in the measurement data. Statistical step detection for determining whether a jump has occurred and / or statistical change detection for determining whether a change has occurred can include sequentially discounting the autoregressive time series model.

[0057] Although the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary rather than restrictive; the invention is not limited to the disclosed embodiments. Other variations of the embodiments to be disclosed may be understood and effected by those skilled in the art in practicing the claimed invention by studying the drawings, the disclosure and the appended claims. In the claims, the term "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are listed in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantageous purposes. Any reference signs in the claims should not be construed as limiting the scope.

[0058] Reference numerals list

[0059] 1 Gas insulated switchgear

[0060] 2 Sensors

[0061] 3 Computer unit

[0062] Room 4

[0063] 5 Insulating gas

[0064] 6 Medium voltage components

Claims

1. A gas monitoring system, comprising: A gas-insulated switchgear (1) comprising a chamber (4) filled with an insulating gas (5) surrounding a high-voltage or medium-voltage component (6), a sensor (2) operatively connected to the chamber (4) and adapted to measure a physical property of the insulating gas (5) in the chamber (4) over a period of time, and A computer unit (3) adapted to perform statistical step detection on the sensor measurement values ​​to determine whether a jump has occurred and / or statistical change detection on the sensor measurement values ​​to determine whether a change has occurred, wherein: The statistical step detection and / or the statistical change detection comprises: confirming an expected range based on past sensor measurements and checking whether a current sensor measurement is outside the expected range.

2. A gas monitoring system according to the preceding claim, wherein: If a jump and / or change occurs, the computer unit (3) is adapted to: a) resetting the leakage rate calculation of the insulating gas (5) in the chamber (4), or b) removing the jumps and / or changes by applying an offset to the sensor measurements.

3. A gas monitoring system according to the preceding claim, wherein: The computer unit (3) is adapted to: c) in the case of determining that a jump has occurred, deciding to perform a) or b) according to the height of the jump and / or the direction of the jump and / or an additional measurement signal indicating the state of the gas-insulated switchgear, and / or wherein, The computer unit (3) is adapted to: d) calculating the leakage rate of the insulating gas (5) in the chamber (4).

4. A gas monitoring system according to any one of the preceding claims, wherein: The jump and / or change is characterized by a measured value ≥ 1.5, 2.0 or 2.5 of the standard deviation of the measured values ​​of the last hour, last two hours, last day or last two days.

5. A gas monitoring system according to any one of the preceding claims, wherein: The statistical change detection involves sequentially discounting an autoregressive time series model.

6. A gas monitoring system according to any one of the preceding claims, wherein: The physical property of the insulating gas (5) is indicative of the density of the insulating gas (5) in the chamber (4).

7. A gas monitoring system according to any one of the preceding claims, wherein: The gas insulated switchgear comprises a voltage transformer.

8. A gas monitoring system according to any one of the preceding claims, wherein: The insulating gas (5) is SF6.

9. A method for detecting jumps and / or changes in a gas-insulated switchgear (1), the gas-insulated switchgear (1) comprising a chamber (4) filled with an insulating gas (5) surrounding a high-voltage or medium-voltage component (6), the method comprising the following steps: measuring a physical property of the insulating gas (5) in the corresponding chamber (4) over a period of time, and Statistical step detection is performed on the sensor measurement value to determine whether a jump has occurred and / or statistical change detection is performed on the sensor measurement value to determine whether a change has occurred, wherein: The statistical step detection and / or the statistical change detection comprises: confirming an expected range based on past sensor measurements and checking whether a current sensor measurement is outside the expected range.

10. The method according to the preceding method claim, wherein: If a jump and / or change occurs, the method comprises the following steps: a) resetting the leakage rate calculation of the insulating gas (5) in the chamber (4), or b) removing the jumps and / or changes by applying an offset to the sensor measurements.

11. The method according to the preceding method claim, wherein: The method comprises the following steps: c) when it is determined that a jump has occurred, deciding to perform a) or b) according to the height of the jump and / or the direction of the jump and / or an additional measurement signal indicating the state of the gas-insulated switchgear.

12. The method according to any one of the preceding method claims, comprising the steps of: d) calculating the leakage rate of the insulating gas (5) in the chamber (4).

13. The method according to any one of the preceding method claims, wherein: The jump and / or change is characterized by a measured value ≥ 1.5, 2.0 or 2.5 of the standard deviation of the measured values ​​of the last hour, last two hours, last day or last two days.

14. The method according to any one of the preceding method claims, wherein: The statistical change detection involves sequentially discounting an autoregressive time series model.

15. The method according to any one of the preceding method claims, wherein: The physical property of the insulating gas (5) is indicative of the density of the insulating gas (5) in the chamber (4).

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