A method and system for monitoring SF6 gas density

Abstract

The present application relates to a kind of SF6 gas density monitoring method and system, including multiple SF6 density relay, edge gateway and cloud platform.SF6 density relay is installed in the gas inlet of GIS equipment each gas chamber, its built-in antenna, main control circuit board, temperature pressure integrated sensor, power supply and base plate etc., real-time acquisition SF6 gas temperature and pressure data, calculate density value and standard temperature compensation pressure value by state equation, through LoRa wireless communication transmission to edge computing gateway;Edge computing gateway identifies the relay number of the temperature value exceeding the site index, determines that it is disturbed by heating device, triggers dynamic correction algorithm to send corrected temperature indication value to SF6 density relay, and upload cloud platform synchronously updates data.The system is combined by hardware distributed layout and edge gateway correction, solves the temperature indication error problem under heating environment, eliminates the risk of SF6 relay misjudgment, realizes remote monitoring and alarm.

Description

Technical Field

[0001] This invention relates to the field of power technology, and in particular to a method and system for monitoring SF6 gas density. Background Technology

[0002] In actual operation of gas-insulated substations (GIS), sulfur hexafluoride (SF6) density relays face complex and variable temperature environments. In the low-temperature winter environments of Northeast and Northwest China, especially when the ambient temperature drops to -40℃, SF6 gas inside GIS equipment at voltage levels of 126kV to 550kV can liquefy, causing a sharp drop in gas density and triggering low-pressure alarms and lockouts. To prevent liquefaction, existing technologies typically install heating devices (such as heating rods or heating belts) on the outer shell of the GIS gas chamber to maintain the SF6 gaseous state through forced heating. However, such heating devices generate localized high-temperature areas during operation, while the adjacent SF6 density relays, lacking heating units, have temperature sensors that collect values ​​far lower than the actual gas temperature in the heated area. This temperature difference leads to a decrease in the standard temperature compensation pressure value calculated by the microprocessor (…). Serious deviations can occur, leading to false alarms or missed alarms. For example, in 2018, several 500kV substations in a certain area experienced low-pressure blocking faults due to temperature inconsistencies between the heating and non-heating zones, posing a risk to power grid operation.

[0003] Existing solutions to the above problems have fundamental flaws: on the one hand, relying on the temperature controller built into the heating device can only control start-up and shutdown (e.g., start at -25℃ / stop at -20℃), failing to eliminate temperature interference to the monitoring equipment; on the other hand, while edge computing gateways can send and receive data, they lack real-time dynamic correction capabilities, making it difficult to promptly identify data distortion caused by localized heating. With the large-scale construction of ultra-high voltage projects in frigid regions, the problems between densely deployed heating devices and monitoring systems in GIS equipment are becoming increasingly apparent. Therefore, there is an urgent need for a gas density monitoring method and system that integrates real-time edge computing and dynamic correction to fundamentally solve the problem of density monitoring distortion in heated environments. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art by providing an SF6 gas density monitoring method and system, so as to solve or partially solve the problem of density monitoring distortion caused by heat source interference in the calculation of SF6 gas density value and standard temperature compensation pressure value in gas-insulated substations, which is caused by heat source interference.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] One aspect of the present invention provides a method for monitoring SF6 gas density, comprising the following steps:

[0007] In the SF6 density relay, perform:

[0008] Step S1: Obtain the SF6 gas temperature value at the measuring point in the gas chamber of the gas-insulated substation. Calculate the SF6 gas density and standard temperature compensated pressure values ​​based on the pressure values.

[0009] On the edge computing gateway, execute:

[0010] Step S2: Initialize the temperature coefficient to 0.55-0.75, and adjust the SF6 gas temperature value based on this temperature coefficient. Standardization is performed to calculate the standardized temperature index and threshold of each SF6 density relay. By comparing the temperature index and the threshold, SF6 density relays affected by heat source interference are screened out and the SF6 gas temperature value is corrected.

[0011] Step S3, based on the number of SF6 density relays determined to be affected by heat source interference and the SF6 gas temperature value. The kurtosis is used to update the threshold and the temperature coefficient;

[0012] Step S4, adjust the SF6 gas temperature value. Send the corresponding SF6 density relay to recalculate the SF6 gas density value and the standard temperature compensation pressure value;

[0013] Step S5: The numbers of the SF6 density relays identified as being affected by heat source interference, along with the SF6 gas density value, standard temperature compensation pressure value, and SF6 gas temperature value of each SF6 density relay, are sent to the cloud platform to achieve SF6 gas density monitoring.

[0014] The temperature index is calculated using the following formula:

[0015] ,

[0016] in, The temperature specification for SF6 density relays. It is the first Temperature coefficient of the second sample , These are the median and absolute deviation of the SF6 gas temperature values, respectively. For the first The SF6 gas temperature value of an SF6 density relay.

[0017] The threshold is calculated using the following formula:

[0018] ,

[0019] in, For the threshold, The total number of SF6 density relays, This is a correction factor.

[0020] The correction coefficient and the temperature coefficient are updated using the following formula:

[0021] ,

[0022] ,

[0023] in, It is the first Temperature coefficient of the second sample For this is the first SF6 gas temperature value in the second sampling peak, The total number of SF6 density relays, This represents the number of SF6 density relays that were affected by heat sources during the last update.

[0024] The temperature value of SF6 gas is corrected using the following formula:

[0025]

[0026] in, , These are the corrected and uncorrected versions of the first two numbers, respectively. The SF6 gas temperature value of an SF6 density relay. In addition to The SF6 gas temperature value of all SF6 density relays.

[0027] As a preferred technical solution, the condition for determining that the SF6 density relay is affected by heat source interference is:

[0028]

[0029] in, For temperature indicators, The threshold value is used.

[0030] As a preferred technical solution, the SF6 density relay achieves data interaction with the edge computing gateway through LoRa (Long Range Radio) wireless communication, and the edge computing gateway achieves data interaction with the edge computing gateway through 4G / 5G wireless communication.

[0031] As a preferred technical solution, the density value of SF6 gas and the standard temperature-compensated pressure value are calculated using the Betty-Bridgeman equation of state.

[0032] In another aspect, the present invention provides an SF6 gas density monitoring system for implementing the aforementioned SF6 gas density monitoring method, the system comprising:

[0033] Multiple SF6 density relays are connected to the filling ports of each gas chamber in the gas-insulated substation to collect the SF6 gas temperature value in the chamber in real time. And pressure values, and calculate SF6 gas density and standard temperature compensated pressure values;

[0034] The edge computing gateway establishes a connection with each SF6 density relay via a LoRa wireless communication interface to receive monitoring data from the SF6 density relay and perform dynamic corrections.

[0035] The cloud platform establishes a connection with the edge computing gateway via 4G / 5G wireless connection to receive and store monitoring data of SF6 gas and display the density, pressure and temperature change curves of SF6 gas.

[0036] As a preferred technical solution, any SF6 density relay includes:

[0037] The base is connected to a connector, which is fixedly connected to the gas chamber interface three-way valve of the gas-insulated transformer.

[0038] The integrated temperature and pressure sensor is embedded in the central opening of the base and is used to collect the temperature and pressure values ​​of SF6 gas in the gas chamber of a gas-insulated substation in real time.

[0039] A switch, embedded in an opening on one side of the base, is used to control the start and stop of the device;

[0040] An indicator light, embedded in an opening on the other side of the base, is used to display the relay's operating status in real time;

[0041] A power source, connected to the base, includes a power board and a battery;

[0042] The main control circuit board is connected to the integrated temperature and pressure sensor via a four-wire connector. The main control circuit board has a built-in microprocessor module and a LoRa communication module. The microprocessor module is used to calculate the SF6 gas density value and the standard temperature compensation pressure value.

[0043] A shielding cover is installed below the main control circuit board and completely covers its electronic components to achieve electromagnetic shielding and isolation.

[0044] The antenna is supported and fixed by an arc-shaped slot.

[0045] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0046] (1) Achieving high-accuracy SF6 gas density monitoring: To address the problem of density monitoring distortion caused by interference from heat sources in the calculation of SF6 gas density values ​​and standard temperature compensation pressure values, this invention utilizes an edge computing gateway to achieve high-accuracy SF6 gas density monitoring based on temperature coefficients and SF6 gas temperature values. The temperature index and threshold of each SF6 density relay are calculated. By comparing the temperature index and threshold, SF6 density relays that are affected by heat source interference are screened out and the SF6 gas temperature value is corrected. Then, the data is sent back to the SF6 density relay to recalculate the SF6 gas density value and the standard temperature compensation pressure value, so as to achieve highly accurate SF6 gas density monitoring.

[0047] (2) Considering the impact of abnormal temperature fluctuations on the correction algorithm: In view of the problem that the start-up and shutdown of local heating devices at low temperatures in winter will cause abnormal temperature fluctuations, and the fixed correction algorithm parameters (threshold, temperature coefficient) are difficult to adapt to this dynamic distribution characteristics, this application provides an adaptive dynamic correction method for correction algorithm parameters, based on the number of SF6 density relays determined to be affected by heat source interference and the SF6 gas temperature value. The kurtosis is adjusted, the threshold and temperature coefficient are updated, which to some extent overcomes the problem of overcorrection and whistle bias caused by abnormal fluctuations in the temperature field.

[0048] (3) Ensure the safe and stable operation of GIS equipment under different temperatures: The edge computing gateway of this invention uses an adaptive statistical distribution algorithm to identify monitoring points that are interfered with by the heating device, eliminates temperature acquisition deviation through a dynamic correction mechanism, and sends the correction results to the microprocessor of the corresponding relay through the LoRa communication interface to update the local display data in real time. The cloud platform receives the corrected monitoring data based on 4G / 5G wireless connection and accurately locates the abnormal air chamber by combining the location number information, which significantly reduces the risk of malfunction caused by derivative problems such as heating device failure, and ensures the safe and stable operation of GIS equipment under different temperatures.

[0049] (4) The SF6 density relay has strong anti-vibration stability and low inspection cost: The SF6 density relay of this invention adopts an arc-shaped slot to ensure the antenna's anti-vibration stability, and the electromagnetic shielding cover fully isolates the main control circuit board from interference, enhancing the long-term operational reliability of the equipment. It has a built-in LoRa communication module and antenna, which automatically uploads temperature, density, pressure and equipment location number, realizing remote monitoring of the SF6 status of the GIS gas chamber, reducing the risk and cost of manual inspection. Attached Figure Description

[0050] Figure 1 This is a flowchart illustrating the SF6 gas density monitoring method in the embodiment.

[0051] Figure 2 This is a schematic diagram of the SF6 gas density monitoring system in the embodiment;

[0052] Figure 3 This is a three-dimensional assembly diagram of the SF6 density relay structure in the embodiment;

[0053] Figure 4 This is a three-dimensional assembly diagram of the SF6 density relay after disassembling the antenna and power supply in the embodiment;

[0054] Figure 5 This is a graph showing the temperature correction results of the SF6 density relay in the embodiment;

[0055] Figure 6 The example uses an SF6 density relay. Pressure correction result graph,

[0056] The components include: 1. Antenna, 2. Main control circuit board, 3. Power supply, 4. Integrated temperature and pressure sensor, 5. Base, 6. Switch, 7. Indicator light, 8. Bow-shaped slot, 9. Shielding cover, 10. Power board, 11. Battery, 12. Four-wire connector, and 13. Connector. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0058] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0059] Example 1

[0060] To address the technical problem of SF6 density relay monitoring data distortion, pressure compensation calculation errors, and false alarms caused by localized temperature anomalies in the GIS gas chamber due to heat sources such as heating devices under medium and low temperature conditions, this embodiment provides an SF6 gas density monitoring method. (See [link to relevant documentation]). Figure 1 The methods mainly involve SF6 density relays, edge computing gateways, and cloud platforms.

[0061] The method includes steps S1-S5, wherein step S1 is executed in the processor built into the SF6 density relay, and steps S2-S5 are executed in the edge computing gateway that has been pre-connected to the SF6 density relay:

[0062] Step S1: Each SF6 density relay acquires the temperature value of the SF6 gas in each gas chamber of the GIS. T and pressure value P And calculate the density value ρ and the standard temperature compensated pressure value. .

[0063] SF6 density relays are installed at the gas inlets of each gas chamber in the GIS, and use built-in integrated temperature and pressure sensors (or separate temperature and pressure sensors) to collect the temperature value of SF6 gas. T and pressure value P The density value ρ of SF6 gas and the pressure value compensated for at a standard temperature of 20°C were calculated using the Betty-Bridgeman equation of state in the built-in microprocessor. Simultaneously, the temperature value of SF6 gas is displayed on a local LCD screen or other visual interactive interface. T Pressure value P and the standard temperature compensation pressure value at 20℃ .

[0064] In step S2, the edge computing gateway obtains the SF6 gas temperature value from the SF6 density relay via the LoRa wireless communication interface. The algorithm uses dynamic correction to filter out SF6 density relays that are affected by the heating device (i.e., heat source) and calculates the corrected temperature. .

[0065] Specifically, the dynamic correction algorithm includes the following steps:

[0066] Step S201, the edge gateway counts all SF6 density relays within the receiving station. t Based on the sampled data, the main control processor calculates the temperature index of each SF6 density relay:

[0067] ,

[0068] Recalculate the threshold:

[0069] ,

[0070] in, ( i =1, 2, 3... N ,N (Total number of relays) represents the temperature value collected by the temperature sensor; , These are the temperature values ​​of SF6 gas. T The median and absolute deviation; It is the first t The temperature coefficient for this sampling was initially set to 0.6745. The correction factor is initially set to 0.2, and its initial value is obtained based on experience with abnormal SF6 density relays in substations affected by heating devices.

[0071] For temperature indicators Its function is to standardize temperature deviations; the temperature coefficient defined in this embodiment... It is a dimensionless parameter with an initial value of 0.6745. This value is used to normalize the median absolute deviation (MAD) to make it close to the standard deviation. If the temperature coefficient... A fixed value of 0.6745 is used to assume that the temperature data follows a standard normal distribution. However, considering that in actual operation, GIS equipment is affected by factors such as interference from heating devices and load changes, its temperature distribution is prone to deviating from the standard normal distribution, affecting the accuracy of subsequent calculations. Therefore, to more accurately represent the actual temperature distribution characteristics, a dynamic temperature coefficient mechanism is adopted, which dynamically adjusts the coefficient based on real-time temperature data to improve the accuracy and adaptability of the status assessment. The dynamic temperature coefficient mechanism is detailed in step S3.

[0072] The value of 60 in the threshold formula is set to take into account the number of SF6 sensors installed in GIS substations. N Typically fewer than 60 and at least 3, the value of 3 originates from the 3σ principle in statistics, derived from temperature indicators. Standardization was performed to concentrate the temperature data within the (-3, 3) range. N =60, ;when N When =3, It is between -2.7 and 1.1.

[0073] Step S202, filter out The j A density relay is determined to be interfered with by a heating device (i.e., a heat source), and the correction formula is applied accordingly. Calculate its corrected temperature value ;like Not exceeding the threshold If so, the data collected by the density relay is determined to be normal.

[0074] Step S3, based on the number of SF6 density relays determined to be affected by heat source interference and the SF6 gas temperature value. Peak value, update temperature coefficient and correction factor :

[0075] ,

[0076] ,

[0077] In the formula, n For the previous update The number of abnormal SF6 density relays. It is the first t Secondary sampling temperature T The peak value.

[0078] For temperature coefficient The update formula, as explained above regarding the temperature coefficient, considers the distribution of temperature data during the update process. The formula indicates that when kurtosis > 0.5, the data exhibits a peaked distribution, suggesting that the collected temperature data is concentrated and the GIS equipment is operating at a constant temperature. When kurtosis < 0.5, the temperature data is dispersed, indicating significant fluctuations in the temperature collected by the SF6 density relay. By comparing kurtosis... A value of 0.5 can characterize the distribution of temperature data.

[0079] For correction coefficient The update formula, if If the anomaly rate is >35%, it is considered to be in a high anomaly rate state, and the threshold is lowered. To avoid missed detections. If If the anomaly rate is less than 5%, it is considered to be in a low anomaly rate state, and the threshold is increased. This improves the sensitivity of detection and avoids false positives.

[0080] The calculation formula is:

[0081] ,

[0082] In the formula, and These are the temperature values ​​of SF6 gas. T The mean and standard deviation of the data are shown; kurtosis > 0.5 indicates that the data shows a peaked distribution, suggesting that the collected temperature data is concentrated and the GIS equipment is operating at a constant temperature; kurtosis < -0.5 indicates that the temperature data is dispersed, suggesting that the temperature collected by the SF6 density relay shows significant fluctuations.

[0083] The above update mechanism takes into account the abnormal temperature fluctuations caused by the start-up and shutdown of local heating devices in low-temperature winters. Fixed temperature coefficients are difficult to adapt to this dynamic distribution characteristic. When low temperatures cause temperature data to be skewed to the left, the original coefficients will underestimate the true deviation and delay leak warnings. When high temperatures cause data to be skewed to the right, normal thermal expansion is easily misjudged as abnormal. At the same time, fixed correction coefficients cannot detect changes in the frequency of abnormalities, and when frequent operations during maintenance seasons lead to frequent abnormalities, the mechanism may fail to detect such changes. A value that is too low will trigger overcorrection, exacerbating SF6 relay misadjustment; while during long-term stable operation, High values ​​can lead to SF6 leakage risks.

[0084] Step S4: Correct the SF6 gas temperature value of the SF6 density relay that was determined to be affected by the interference. Send to the corresponding SF6 density relay.

[0085] For SF6 density relays identified as being affected by interference, the LoRa communication interface of the edge gateway will send the corrected temperature value. The data is sent to the corresponding SF6 density relay, and the SF6 gas density value is recalculated in the microprocessor of the corresponding SF6 density relay. ρ and 20℃ standard temperature compensation pressure value .

[0086] Step S5: Measure the SF6 gas density value using a normal SF6 density relay. ρ and 20℃ standard temperature compensation pressure value Uploaded to the cloud.

[0087] For SF6 density relays that are determined to be normal, the data is directly uploaded to the cloud platform via 4G / 5G wireless communication.

[0088] The edge gateway transmits the corrected judgment via 4G / 5G wireless transmission. and the serial number of the abnormal SF6 density relay. L Synchronously upload to the cloud platform system and update monitoring data.

[0089] Among them, the location number of the SF6 density relay L It includes the gas chamber identification information of GIS equipment, which is used by the cloud platform to locate the SF6 density relay and gas chamber location at abnormal temperatures.

[0090] The cloud platform receives and stores monitoring data of SF6 gas and displays the density, pressure, and temperature change curves of SF6 gas.

[0091] To verify the effectiveness of this method, temperature and pressure data uploaded by the SF6 gas sensor of a 110 kV GIS device were processed by a dynamic correction algorithm, and the results are as follows: Figure 5 and Figure 6 As shown, the temperature readings at 14 temperature monitoring points from 4 sensors exceeded the threshold. Temperature coefficient at each point Correction coefficient and the corrected temperature With pressure value See Table 1 for details. The original data shows that higher temperatures lead to lower SF6 pressure readings, while lower temperatures lead to higher pressure readings. After processing by the dynamic correction algorithm provided in this embodiment, the pressure values ​​are accurately corrected, more realistically reflecting the actual pressure state of the SF6 gas.

[0092] Table 1 Results of the Dynamic Correction Algorithm

[0093]

[0094] Example 2

[0095] Based on the foregoing embodiments, this embodiment provides an SF6 gas density monitoring system for implementing the SF6 gas density monitoring method of Embodiment 1. (See [link to previous embodiment]). Figure 2 and Figure 3 The system mainly includes antenna 1, main control circuit board 2, power supply 3, integrated temperature and pressure sensor 4, base 5, switch 6, and indicator light 7.

[0096] Antenna 1 is supported and fixed by the arc-shaped slot 8;

[0097] The microprocessor module built into the main control circuit board 2 calculates the SF6 gas density ρ and the 20℃ standard temperature compensation pressure using the Betty-Bridgeman equation of state. The built-in LoRa communication module and antenna 1 transmit temperature values ​​containing SF6 gas. T ,density ρ Compensation pressure and the relay location number L Data;

[0098] The shielding cover 9 is located below the main control circuit board 2 and completely covers its electronic components to form electromagnetic shielding isolation;

[0099] Power supply 3 consists of a power board 10 and a battery 11 forming a power supply unit;

[0100] The integrated temperature and pressure sensor 4 is embedded in the central opening of the base 5 and is used to collect the temperature value of SF6 gas in the GIS gas chamber in real time. T and pressure P Data is connected to the main control circuit board 2 via the four-wire connector 12.

[0101] The switch 6 is embedded in an opening on one side of the base 5 and is used to control the start and stop of the device;

[0102] Indicator light 7 is embedded in the opening on the other side of the base 5 and is used to display the working status of the device in real time;

[0103] The connector 13 of the base 5 is fixedly connected to the GIS air chamber interface three-way valve.

[0104] The SF6 density relay designed in this invention uses an arc-shaped slot to ensure the antenna's shock resistance and stability, and an electromagnetic shield to fully isolate interference from the main control circuit board, enhancing the long-term operational reliability of the equipment. It has a built-in LoRa communication module and antenna, which automatically uploads temperature, density, pressure and equipment location number, enabling remote monitoring of the SF6 status of the GIS gas chamber and reducing the risks and costs of manual inspection.

[0105] In this invention, the system's edge computing gateway uses an adaptive statistical distribution algorithm to identify monitoring points affected by the heating device. A dynamic correction mechanism eliminates temperature acquisition deviations, ensuring the accuracy of the 20℃ standard compensation pressure value calculation. This effectively overcomes the density monitoring distortion caused by local temperature deviations in the heating device, improving the accuracy and reliability of the monitoring data. Simultaneously, the correction results are sent to the corresponding relay's microprocessor via a LoRa communication interface, updating the locally displayed data in real time. The cloud platform receives the corrected monitoring data via 4G / 5G wireless connection and, combined with location number information, accurately locates abnormal gas chambers, significantly reducing the risk of malfunctions caused by heating device failures and other derivative problems, ensuring the safe and stable operation of GIS equipment at different temperatures.

[0106] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method of SF6 gas density monitoring, characterized by, Comprising the following steps: In the SF6 density relay, the following is performed: Step S1, obtaining SF6 gas temperature value of measuring point in gas insulated substation gas chamber and pressure value, calculating SF6 gas density value and standard temperature compensation pressure value; In the edge computing gateway, the following is performed: Step S2, initializing a temperature coefficient as 0.55-0.75, calculating the SF6 gas temperature value based on the temperature coefficient The temperature index of each SF6 density relay after normalization is calculated, and the threshold value is calculated. By comparing the temperature index and the threshold value, the SF6 density relay disturbed by the heat source is screened out, and the SF6 gas temperature value is corrected. The temperature index is calculated by the following formula: ， wherein, is a temperature index for the SF6 density relay, is the first sampled temperature coefficient, , are the median value and the absolute deviation of the SF6 gas temperature values, respectively, is the SF6 gas temperature value of the SF6 density relay, The threshold is calculated by the following formula: ， wherein is a threshold value, is the total number of SF6 density relays, is a correction factor, The SF6 gas temperature value is corrected by the following formula: ， in, , These are the corrected and uncorrected versions of the first two numbers, respectively. The SF6 gas temperature value of an SF6 density relay. In addition to The SF6 gas temperature values ​​of all SF6 density relays; Step S3, updating the correction coefficient and the temperature coefficient based on the number of SF6 density relays determined to be disturbed by a heat source and the SF6 gas temperature value kurtosis of the peak value, updating the correction coefficient and the temperature coefficient: ， ， wherein, is the temperature coefficient of the first sampled temperature value, is the kurtosis of the first sampled SF6 gas temperature value is the total number of SF6 density relays, is the number of SF6 density relays disturbed by heat sources at the last update;​ Step S4, the modified SF6 gas temperature value SF6 gas density value and standard temperature compensation pressure value are recalculated and sent to the corresponding SF6 density relay; In step S5, the number of the SF6 density relay determined to be disturbed by the heat source, and the SF6 gas density value, the standard temperature compensation pressure value, and the SF6 gas temperature value of each SF6 density relay are sent to the cloud platform to realize SF6 gas density monitoring.

2. The SF6 gas density monitoring method according to claim 1, characterized by, The condition for determining that the SF6 density relay is disturbed by the heat source is: ， wherein is a temperature index, is a threshold value.

3. The SF6 gas density monitoring method according to claim 1, characterized by, The SF6 density relay realizes data interaction with the edge computing gateway through LoRa wireless communication, and the edge computing gateway realizes data interaction with the edge computing gateway through 4G / 5G wireless communication.

4. The SF6 gas density monitoring method according to claim 1, characterized by, The SF6 gas density value and the standard temperature compensation pressure value are calculated by the Bethe-Briggsman state equation.

5. A SF6 gas density monitoring system, characterized in that, A system for implementing the SF6 gas density monitoring method according to any one of claims 1-4, comprising: A plurality of SF6 density relays are connected with the gas inlet of each gas chamber of the gas insulated substation, for collecting the temperature value of SF6 gas in the gas chamber in real time and pressure values, and calculating the SF6 gas density value and the standard temperature compensation pressure value; An edge computing gateway connected with each SF6 density relay through a LoRa wireless communication interface, for receiving monitoring data of the SF6 density relay and performing dynamic correction; A cloud platform connected with the edge computing gateway through 4G / 5G wireless connection, for receiving and storing monitoring data of the SF6 gas, and displaying density, pressure, and temperature change curves of the SF6 gas.

6. A SF6 gas density monitoring system according to claim 5, characterised in that, For any one SF6 density relay, comprising: A base (5) connected with a connector (13) fixedly connected with a gas chamber interface three-way valve of a gas insulated substation; A temperature and pressure integrated sensor (4) embedded in a central opening of the base (5) for real-time acquisition of SF6 gas temperature and pressure values in the gas chamber of the gas insulated substation; A switch (6) embedded in a side opening of the base (5) for controlling the start and stop of the device; An indicator light (7) embedded in the other side opening of the base (5) for real-time display of the working state of the relay; A power supply (3) connected with the base (5), including a power board (10) and a battery (11); A main control circuit board (2) connected with the temperature and pressure integrated sensor (4) through a four-wire connection port (12), the main control circuit board (2) being internally provided with a microprocessor module and a LoRa communication module, the microprocessor module being used for calculating SF6 gas density values and standard temperature compensation pressure values; A shielding cover (9) arranged below the main control circuit board (2) and completely covering the electronic components thereof to realize electromagnetic shielding and isolation; An antenna (1) supported and fixed by an arc-shaped clamping groove (8).

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