CN112103923B - Method for realizing GIL protection based on thermal characteristic abnormity - Google Patents
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
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- H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
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- H—ELECTRICITY
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- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
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- H02H5/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection
- H02H5/04—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature
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Abstract
A method for realizing GIL protection based on thermal characteristic abnormity is suitable for GIL state monitoring. Establishing a thermal characteristic model of the GIL, and iteratively calculating the thermal characteristic of the GIL by utilizing the partial differential equation coupling of computational fluid mechanics, electromagnetism and thermodynamics; calculating the temperature change rate and the temperature change acceleration by deducing the thermal characteristic parameters of the shell in normal and abnormal operation states, processing data by normalization, and classifying by using a density clustering algorithm; protective actions of different degrees are selected according to classification, an infrared sensor is arranged on the outer surface of the GIL shell to measure the temperature, and signals can be transmitted to a thermal characteristic protective action device to carry out protective actions. The temperature change rate and the temperature change acceleration are selected as the basis for identifying the abnormal degree, corresponding protection actions are carried out, meanwhile, the influence of external environment factors on the thermal characteristics is considered, and the protection accuracy is guaranteed.
Description
The technical field is as follows:
the invention relates to a method for realizing GIL protection based on thermal characteristic abnormity, and belongs to the field of identification and protection of GIL abnormal heating.
Background art:
along with the continuous improvement of the transmission grade of the ultra-high voltage power grid, the influence of severe environmental conditions such as rain, snow, freezing weather, dirt and the like on the transmission effect of the traditional overhead line is more and more obvious, and the GIL has more and more important function in the ultra-high voltage transmission as a transmission line which has high reliability in safe operation, large transmission capacity and is not easily influenced by the environment, and the temperature change rate of the GIL is researched to identify the temperature rise condition in the abnormal state of the GIL, so that the GIL has important significance on the improvement of the safe operation of the GIL. During operation, the GIL conductor temperature will rise due to the heat generated by its joule heating losses and the insulating gas will heat up through heat exchange; meanwhile, the GIL case induced current heat loss and eddy current heat loss also cause the temperature rise of the conductor, the case and the internal insulating gas. In the GIL with the load current often reaching thousands of amperes, internal overheating faults are easily caused by the overhigh temperature in an abnormal state, so that the temperature change rate of the GIL needs to be analyzed and researched, the identification and protection of the abnormal heating of the GIL are realized, and the operation reliability of a GIL system is improved.
Disclosure of Invention
The invention aims to provide a method for realizing GIL protection based on thermal characteristic abnormality, which solves the problems of judging and protecting the abnormal state of the GIL from the thermal characteristic angle, analyzes the thermal characteristic difference of different abnormal states on the basis of considering finite element analysis and multi-physical field coupling analysis, classifies the shell temperature change rate and realizes the protection purpose.
The invention adopts the following technical scheme to solve the technical problems
The method for realizing GIL protection based on the thermal characteristic abnormity comprises the following specific steps:
step S1: establishing a GIL bus thermal characteristic model, analyzing thermal characteristics in different states by combining electromagnetism, computational fluid mechanics and thermodynamics, and simulating and calculating a shell temperature value in a normal state and a shell temperature value in different abnormal states under a rated working condition through the established model;
step S2: the thermal characteristics of normal operation are obtained by analyzing the normal operation state of the GIL bus, and the temperature change rate range and the temperature change acceleration are further calculated to serve as basic conditions for judging whether abnormity occurs and whether signals are transmitted to a thermal characteristic protection action device; then analyzing the thermal characteristic difference of the GIL bus under different abnormal states, wherein the two abnormal states are respectively classified into abnormal states of abnormal contact resistance or slight damage of parts in the GIL bus as approaching warning, and short-circuit faults such as insulator breakage and the like, deducing formulas of abnormal shell temperature change rate and temperature change acceleration under different abnormal states, and calculating the abnormal shell temperature change rate and temperature change acceleration;
analyzing thermal characteristics of all parts of the GIL bus in a normal state through a result obtained by model simulation, calculating to obtain a range of temperature change rates and temperature change acceleration of all parts of the GIL bus, classifying the temperature change rate of a shell of the GIL bus caused by environmental temperature change into a normal state, wherein the environmental temperature change comprises temperature change caused by wind speed, illumination and seasons, obtaining the thermal characteristics of the GIL bus in any environment by utilizing the model simulation, and giving normal temperature ranges in different environments; analyzing the thermal characteristics of the abnormal state through the temperature field value obtained by the simulation model calculation result, calculating to obtain the range of the temperature change rate and the temperature change acceleration of the abnormal state, obtaining the range of the change rate and the temperature change acceleration in the normal state and the abnormal state, and using the ranges as the basis for judging the operation state of the GIL bus;
step S3: processing temperature change rate and temperature change acceleration data of all positions of a GIL bus shell by using a normalization method, processing the temperature data by using an abnormal data processing algorithm based on a density clustering method, dividing the GIL state into three states of normal operation, near warning and abnormal temperature warning according to sudden multiple in a short time of current, wherein the GIL structure has various special fault types, the temperature can rise when a component has slight fault but cannot affect the circuit operation in a short time, and the temperature is higher than the normal operation temperature and lower than the temperature of abnormal faults such as short circuit, so that the faults which cannot cause the circuit power failure but need to check the circuit by field personnel are classified into the near warning state; regarding the change of the running current of the line, determining that the line is in an abnormal state when the running current exceeds the rated current by 1.2 times, and performing power failure maintenance; setting the current to be 4 times of the operating current as the highest boundary value of normal operation, and setting the current to be the highest value near the warning when the current is 1.2 times of the rated current;
multiplying the fuzzy matrix R established in the three states by the corresponding weight W to obtain an evaluation factor P of the GIL bus change rate evaluation system, wherein P is W R; if the temperature of the circuit is not within the range of the normal temperature change rate, comparing the range of the normal temperature change rate with the range of the abnormal temperature change rate, and judging whether to perform light protection action or heavy protection action, wherein the light protection action only alarms, and the heavy protection action alarms and cuts off circuit current;
step S4: an infrared temperature measuring sensor is arranged on the outer surface of the GIL shell, and the thermal characteristics of the GIL bus are comprehensively monitored by the infrared temperature measuring sensor so as to carry out protection; the infrared sensor acquires temperature data at regular time, processes and calculates the temperature change rate in real time, transmits the calculation result to the thermal characteristic protection action device, and performs corresponding light protection alarm action and heavy protection alarm action according to the degree of the change rate, thereby achieving the purpose of realizing protection through thermal characteristic difference.
In the step S1, a thermal characteristic model is established according to the GIL bus structure and the coupling relationship between the electromagnetic field, the fluid field, and the thermal field through COMSOL software, and thermal characteristics of the GIL bus under different environmental conditions and different load currents, including heat conduction inside the conductor and the shell, heat convection in the insulating gas domain and the air domain, and heat radiation of the conductor to the insulating gas and the shell to the insulating gas, are calculated and analyzed, and the shell is heated under the combined action, so that the shell temperature of the GIL bus is obtained.
Assuming that the normal GIL bus shell temperature change rate is the average value of n groups of data at the stable running time, the normal shell temperature change rate formula is calculated as follows:
in the formula, TkNormal shell temperature values in units; delta TkThe temperature change rate of the normal shell at a certain time is unit ℃; t is simulation time corresponding to the value of the normal shell temperature value, and is unit s; Δ t is the time interval of the temperature change rate value, in units of s; t is tmA certain moment of stable operation; t is tm+1For stable operation tmTime of the next acquisition temperature;Δθnthe rate of change of the normal shell temperature,
the range of the temperature change rate takes the maximum value delta thetanbWith a minimum value Δ θnsTherefore, the range of the positive normal temperature change rate is (Δ θ)ns,Δθnb)；
When an abnormality occurs, partial discharge may occur in a certain phase or multiple phases of the GIL bus or a single-phase ground fault may occur in a certain phase, the current suddenly increases, the temperature change rate is abnormal, and the abnormal case temperature change rate is calculated as follows:
ΔTf＝Tf(h+1)-Tf(h)
Δt＝t(h+1)-t(h)
in the formula, TfThe shell temperature value at the abnormal point is unit; delta TfThe temperature change rate of the abnormal shell at a certain time is unit ℃; t is simulation time corresponding to the value of the temperature value of the abnormal shell, and is unit s; Δ t is the time interval of the temperature change rate value, in units of s; h is a certain time of abnormal operation; delta thetafAbnormal shell temperature change rate;
considering the temperature change rate and the temperature change acceleration in different states:
in the formula,. DELTA.TkThe temperature change rate of the shell of the GIL bus is unit ℃; t is tqThe time and unit s corresponding to the temperature change rate value of the GIL bus shell is obtained;
in daily operation, the possibility of sudden drop or sudden rise of the ambient temperature in a very short time is very low; the leakage of the insulating gas at the flange and the connection part of the GIL bus shell rarely does not influence the pressure of the insulating gas, so that the gas pressure can be considered as a constant value; and the air humidity does not change greatly; meanwhile, the change of the wind speed generally needs a certain time process, and can cause the slow change of the temperature of the GIL bus shell, and the change belongs to the fluctuation within the range of normal change rate.
Has the advantages that:
the invention provides two judgment methods of temperature change rate and temperature change acceleration, a normalization method is utilized to process data, and data precision and calculation speed are improved; the method comprises the following steps of defining temperature change rates and temperature change acceleration ranges of different protection domains, wherein heating of GIL conductors and shells is in direct proportion to the square of current, the protection domains are divided according to operating current change multiples, therefore, the obtained ranges of the different protection domains have universality, real-time temperature is compared with the defined ranges, temperature data are classified based on a density clustering algorithm and are divided into three states of normal operation, near warning and temperature abnormity warning, and shell temperature change rate ranges and temperature change acceleration values under the three states are respectively given out and serve as bases of thermal characteristic protection actions and warning of different degrees; meanwhile, the temperature change caused by the change of the environmental factors is considered to belong to a normal range, and the method is beneficial to a temperature monitoring system to judge the operation state of the GIL and protect the GIL to different degrees.
The method has good sensitivity and reliability, selects the temperature change rate and the temperature change acceleration as the basis for judging the abnormal section and the abnormal state, can more accurately reflect the change trend of the temperature, is favorable for accurately judging the abnormal state and giving sufficient response time of the protection device, classifies the range of the temperature change rate and the temperature change acceleration, uses the temperature change acceleration for auxiliary judgment, can effectively identify the fault type and act, and has higher reliability; and the reaction time of the protection device is much shorter than the calculation period of the temperature change rate.
Drawings
FIG. 1 is a flow chart for implementing thermal property protection;
FIG. 2 is a flow chart of a density clustering algorithm;
FIG. 3(a) is a graph of normal state temperature change of the housing under typical operation conditions of the GIL;
FIG. 3(b) is a graph of the critical warning temperature variation of the housing under typical operation conditions of the GIL;
FIG. 3(c) is a graph of abnormal case temperature change during a typical operation of the GIL;
FIG. 4 is a graph of thermal property protection characteristics;
Detailed Description
The technical scheme of the invention is further explained in detail by combining the accompanying drawings as follows:
as shown in fig. 1 and 2, the method for implementing GIL protection based on thermal characteristic anomaly of the present invention specifically includes the following steps:
a method for realizing GIL protection based on thermal characteristic abnormity comprises the following specific steps:
(1) establishing a thermal characteristic model, and iteratively calculating the established model by using a partial differential equation solver, wherein the temperature indexes appearing in the calculation process are as follows: joule heat loss generated on the conductor and the shell in the operation process of the GIL, heat radiation quantity generated between the inner surface of the shell and the outer surface of the conductor, heat conduction quantity between the outer surface of the GIL shell and internal heat, and heat transfer quantity through natural convection, forced convection, radiation heat exchange and the like between the outer surface of the shell and air coated on the outer surface; and then analyzing the thermal characteristics of the normal operation state under different working conditions according to the result obtained by calculation of the preset value.
(2) By calculating and analyzing the electromagnetic field and the temperature field, the shell temperature T can be obtainedkWhen the temperature is almost kept stable during stable operation, the temperature change rate tends to a stable value, the shell temperature change rate in a normal state is calculated, n groups of data are selected to enable the temperature change rate to be more accurate, the maximum value and the minimum value of the temperature change rate in the n groups of data are respectively set as the upper limit and the lower limit of the temperature change rate value range of the circuit in the normal state, the GIL circuit is set to be in the normal operation state at the moment m, and the calculation formula is as follows.
In the formula, TkThe shell temperature value of a normal line segment is unit; delta TkThe temperature change rate of the shell of the normal line segment is unit ℃; t is time corresponding to the value of the shell temperature in unit s; Δ t is the time interval over which the rate of temperature change takes value, in units of s.
The range of the rate of change of the shell temperature of the normal line segment is (Delta theta)nl，Δθnr)。
For a normal state, considering a normal acceleration of a temperature change thereof, a formula thereof:
in the formula,. DELTA.TkThe normal shell temperature change rate is unit ℃; t is tmThe time and the unit s corresponding to the temperature change rate value of the normal shell are taken; the acceleration value under each category can be the same, so the highest value under each category is selected as the acceleration value of the category.
SF when load current increases with load, or partial discharge occurs somewhere in GIL6The gas is instantaneously heated by a discharge arc, or when a single-phase earth fault occurs to a certain phase of the GIL to cause sudden current increase, the shell temperature change rates with different degrees are abnormal, the data with the maximum temperature increase amplitude is selected to calculate the change rate as an upper value limit during calculation, the data with the minimum temperature increase amplitude is selected to calculate the change rate as a lower value limit, the temperature change rates in the range are both in a protection-replay abnormal state, and the shell temperature change rate calculation formula of an abnormal line segment is as follows:
assuming that the increase amplitude of the temperature of the abnormal shell is maximum before and after the h moment, the value upper limit calculation formula of the temperature change rate of the abnormal shell is as follows:
ΔTmax′＝T′k(h+1)-T′k(h)
Δt＝t(h+1)-t(h)
in formula (II) T'kThe temperature change value of the shell at the abnormal point is unit ℃; Δ t is the time interval in units of s.
Assuming that the shell temperature increase amplitude of the abnormal point before and after the moment d is minimum, the value lower limit calculation formula of the abnormal shell temperature change rate is as follows:
ΔTmin′＝T′k(d+1)-T′k(d)
Δt＝t(d+1)-t(d)
therefore, the value of the abnormal shell temperature change rate (. DELTA.. theta.) (fs，Δθfd)。
Under different abnormal operation states of the GIL, the temperature change acceleration is considered, and the formula is as follows:
in the formula,. DELTA.TkThe rate of change of the temperature of the abnormal shell is unit ℃; t is tqThe time and the unit s corresponding to the temperature change rate value of the abnormal shell are taken; and selecting the highest value under each category as the acceleration value of the category.
(3) And processing the temperature change rate and the temperature change acceleration obtained by calculation by using a normalization method, and mapping the data to a range of 0-1 for processing so as to improve the accuracy of the model and the calculation speed.
The normalization of the data was done using the following formula:
wherein x' is temperature data in the range of (0, 1) after treatment, xiAs the rate of change of temperature to be processed in the data set, max (x)i)、min(xi) Respectively, the maximum and minimum values in the data set.
(4) Data are classified by an abnormal data processing algorithm based on a density clustering method, and firstly, a data set D ═ X is obtained1,X2,X3……Xm) Comprising m unmarked data vectors XmEach XmIs a vector of dimension n (X)1,x2,x3……xn) Dividing D into k disjoint data clusters { C by adopting a density clustering-based method l1,2 … k, finding a core object through the minimum element number and radius of the cluster, traversing all elements in the data set by taking the core object as a seed to find abnormal temperature data, detecting the abnormal temperature data by giving the radius of the cluster and the number of the cluster, processing the abnormal temperature data, reducing the number of the outliers and the discrete degree of the outliers, then replacing the outliers in the data set by proper values, reducing the overall discrete degree of the data set, and finally classifying the data to be divided into the data set in a normal operation state and the data set in abnormal states in different degrees. The method comprises the steps of clustering the shell temperature and the SF6 pressure value step by adopting a method of step aggregation and data type division, wherein the SF6 pressure value can be directly obtained from simulation, and the SF6 pressure value on a line operation site is directly obtained from a pressure detection table installed on the shell, namely, only single parameters in a period of time are clustered each time. Taking the case temperature data as an example, assume that the time series of the case temperature is T ═ T (T)1,t2,……tn-1,tn) Data of adjacent time is taken according to a certain step length and combined according to sequence to form three-dimensional data
(5) T＝[(t1,t2,t3)；(t4,t5,t6)；……(tt-1,tt,tt+1)]
(6) After clustering is completed, points which cannot meet the requirements of neighborhoods and minimum clusters are isolated, and the points are temperature abnormal data searched by the algorithm, so that a temperature change rate abnormal database of the online monitoring system is formed.
(7) The method comprises the following steps of respectively measuring two parameter data of a shell temperature change rate and an SF6 pressure value in the operation process of the GIL bus through sensors, and not performing overall comprehensive evaluation on the temperature change rate state of the GIL bus through a single parameter comparison method, so that a multi-sensor comprehensive evaluation algorithm is adopted, the two parameters are combined to perform fuzzy comprehensive evaluation on the state of the GIL bus, and an evaluation factor set of a GIL bus change rate evaluation system is required to be established:
P＝(p1,p2) Temperature change rate of the shell, SF6 pressure value }
The GIL bus temperature state is divided into three levels: normal operation, approaching warning and abnormal temperature. The evaluation set of the present evaluation system is therefore:
V＝(vi1,vi2,vi3) Normal operation, proximity warning, temperature anomaly (i 1,2)
i is 1 for three levels of shell temperature, and i is 2 for SF6Three levels of pressure values. Using membership functions rijAnd (3) associating each parameter with the corresponding evaluation grade to establish a fuzzy matrix R:
rijrepresenting the membership of the ith parameter and the j level, eiFor the collected data, the function when j is 1 is as follows:
the function when j is 2 is as follows:
the function when j is 3 is as follows:
filling each parameter into the matrix, and obtaining the fuzzy matrix. In this embodiment, W ═ W is not considered in the change of the weight under different environments1,w2]And the temperature change rate of the GIL bus can be comprehensively evaluated by the fuzzy matrix so as to judge the abnormal degree of the temperature change rate of the GIL bus.
The light protection and the heavy protection are the same in principle, because the temperature change rate and the temperature change acceleration range are different, protection alarm actions of different degrees of the protection action device are selected according to the category to which the temperature change belongs, action time corresponding to different protections is different and is in an inverse time limit characteristic, the change close to the warning temperature is changed into the light protection alarm action, the temperature change with abnormal temperature is changed into the heavy protection alarm action, and GIL protection can be achieved according to the abnormal thermal characteristic.
The method has strong reliability: the temperature change rate and the temperature change acceleration are used as the basis for detecting or judging the abnormal section and the abnormal state of the fault, the change trend of the temperature can be judged more accurately, and the basic fault type can be effectively identified and the action can be carried out through the detailed classification of the temperature change rate data range.
According to the above analysis, the method defines a sensitivity coefficient Ks as a basis for determining the sensitivity level, as follows:
the time period of temperature change rate calculation is 100ms, the protection action time is the time difference value of current change and temperature change, the difference value is 100ms according to simulation, so the sensitivity coefficient is 1, and according to the actual operation condition on site, the protection action can be carried out before the accident is further worsened, so the method has better sensitivity.
The shell temperature data of each line segment of the GIL is collected by an infrared thermometer, so that the GIL state can be comprehensively monitored, and the protection based on the thermal characteristic abnormity is realized; the infrared thermometer collects temperature data in real time and calculates the temperature change rate of the current point, compares the real-time temperature change rate with three groups of temperature ranges in a database, transmits signals to the thermal characteristic action protection device, and determines whether to make a light protection action or a heavy protection action and a corresponding alarm action.
As shown in fig. 3(a), fig. 3(b) and fig. 3(c), the shell temperature change diagram in the GIL typical operation state can obtain the shell temperature change rate of the heavy protection abnormality of the normal operation line by establishing a thermal characteristic model and a multi-physical field coupling method, and it can be seen that the temperature change rate is increased rapidly, and the abnormal temperature change rate is increased rapidly, so that the abnormal occurrence section and the abnormal state can be determined by calculating and analyzing the temperature change rate of the GIL line segment, the temperature tends to be in a stable state after 6000s in the simulation, the temperature value after 6000s is taken for calculation, and the time interval of the calculation of the temperature change rate is 100 ms.
The temperature change rate calculation for eight groups of data in the normal state was averaged and considered to be a change in the normal range when the load current increased from 1000A to up to 4000A, and the case operating temperature data is shown in table 1 below,
TABLE 1 case temperature data
Calculating according to a normal state temperature change rate calculation formula, wherein the value range of the temperature change rate is obtained as follows:
[0, 0.7], the acceleration a of the temperature change takes a value of 3.
When the load current of the GIL hardly changes in the operation process, the temperature change rate range of the shell also conforms to the value range, so that the shell temperature change rate of the GIL in the normal state is [0, 0.7 ].
Taking the approaching alert state as an example, the load current of the GIL bus is too large and continues for a period of time, at this time, the load current is increased to 1.2 times of the rated current when the simulation time 7000s is set and continues for a certain time, the temperature data of the approaching alert state is shown in the following table 2, M ist
TABLE 2 temperature data of the housing near alert condition
Calculating according to a temperature change rate calculation formula in a near warning state, and obtaining a temperature change rate value range as follows: [0.7, 1.5], the acceleration a' of the temperature change takes a value of 9.
Taking the protection fault as an example, the single-phase bus insulation gas breakdown fault as an example, the single-phase grounding fault occurs at this time, the single-phase grounding fault occurs when the simulation time is 7000s, the duration is 100ms, the temperature data in the fault state is shown in the following table 3,
TABLE 3 Re-protection abnormal case temperature data
Calculating according to a temperature change rate calculation formula in an abnormal state, wherein the value range of the temperature change rate is as follows: [1.5, 3.5], the acceleration a' of the temperature change takes 27.
The action characteristic of the GIL protection can be obtained through the three classified calculation data by combining with the attached figure 4, wherein the abscissa is the temperature change rate, and the ordinate is the alarm time. Because the acceleration has the same value in each state, the acceleration of temperature change is used as an auxiliary means, and the two factors jointly determine the running state; the first state is a normal running state, the action characteristic is a temperature change rate [0, 0.7], meanwhile, the temperature change acceleration is less than 3, the action time is more than 1 second, and the protection action is not carried out; for the light protection under the state close to the alert state, the action characteristic is the temperature change rate [0.7, 1.5], meanwhile, the temperature change acceleration is less than 9, the action time is 0.1 second to 1 second, and sufficient time is reserved for further judging the type of the abnormal state; for the heavy protection action trip, the action characteristic is the temperature change rate [1.5, 3.5], meanwhile, the temperature change acceleration is less than 27, and the action time is 0.1 second for ensuring the safety of equipment; it should be noted that although the temperature change acceleration is an auxiliary determination means, the protection and alarm actions are triggered when any one of the two determination factors is satisfied under each condition.
In this embodiment, the GIL line segment is more favorable to detecting the actual operation condition of the GIL on site through thermal characteristic analysis and temperature monitoring, and corresponding thermal characteristic protection is performed through calculating the temperature change rate and the acceleration and classifying, so that the abnormal degree of the GIL can be accurately and quickly judged, and the reliable operation of the GIL is ensured.
Claims (3)
1. A method for realizing GIL protection based on thermal characteristic abnormity is characterized by comprising the following specific steps:
step S1: establishing a GIL bus thermal characteristic model, analyzing thermal characteristics in different states by combining electromagnetism, computational fluid mechanics and thermodynamics, and simulating and calculating a shell temperature value in a normal state and a shell temperature value in different abnormal states under a rated working condition through the established model;
step S2: the thermal characteristics of normal operation are obtained by analyzing the normal operation state of the GIL bus, and the temperature change rate range and the temperature change acceleration are further calculated to serve as basic conditions for judging whether abnormity occurs and whether signals are transmitted to a thermal characteristic protection action device; then analyzing the thermal characteristic difference of the GIL bus under different abnormal states, wherein the two abnormal states are respectively abnormal contact resistance of each component in the GIL bus or the component is slightly damaged to be close to warning, and the short-circuit fault of the broken insulator is classified into the abnormal state, deducing formulas of the abnormal change rate and the abnormal temperature change acceleration of the shell under different abnormal states, and calculating the abnormal change rate and the abnormal temperature change acceleration of the shell;
analyzing thermal characteristics of all parts of the GIL bus in a normal state through a result obtained by model simulation, calculating to obtain a range of temperature change rates and temperature change acceleration of all parts of the GIL bus, classifying the temperature change rate of a shell of the GIL bus caused by environmental temperature change into a normal state, wherein the environmental temperature change comprises temperature change caused by wind speed, illumination and seasons, obtaining the thermal characteristics of the GIL bus in any environment by utilizing the model simulation, and giving normal temperature ranges in different environments; analyzing the thermal characteristics of the abnormal state through the temperature field value obtained by the simulation model calculation result, calculating to obtain the range of the temperature change rate and the temperature change acceleration of the abnormal state, obtaining the range of the change rate and the temperature change acceleration in the normal state and the abnormal state, and using the ranges as the basis for judging the operation state of the GIL bus;
step S3: processing temperature change rate and temperature change acceleration data of all positions of a GIL bus shell by using a normalization method, processing the temperature data by using an abnormal data processing algorithm based on a density clustering method, dividing the GIL state into three states of normal operation, near warning and abnormal temperature warning according to sudden multiple in a short time of current, wherein the GIL structure has various special fault types, the temperature can rise when a component has slight fault but cannot affect the circuit operation in a short time, and the temperature is higher than the normal operation temperature and lower than the temperature of the abnormal fault with short circuit, so that the faults which cannot cause the circuit power failure but need to be checked by field personnel are classified into the near warning state; regarding the change of the running current of the line, determining that the line is in an abnormal state when the running current exceeds the rated current by 1.2 times, and performing power failure maintenance; setting the current to be 4 times of the operating current as the highest boundary value of normal operation, and setting the current to be the highest value near the warning when the current is 1.2 times of the rated current;
multiplying the fuzzy matrix R established in the three states by the corresponding weight W to obtain an evaluation factor P of the GIL bus change rate evaluation system, wherein P is W R; if the temperature of the circuit is not within the range of the normal temperature change rate, comparing the range of the normal temperature change rate with the range of the abnormal temperature change rate, and judging whether to perform light protection action or heavy protection action, wherein the light protection action only alarms, and the heavy protection action alarms and cuts off circuit current;
step S4: an infrared temperature measuring sensor is arranged on the outer surface of the GIL shell, and the thermal characteristics of the GIL bus are comprehensively monitored by the infrared temperature measuring sensor so as to carry out protection; the infrared sensor acquires temperature data at regular time, processes and calculates the temperature change rate in real time, transmits the calculation result to the thermal characteristic protection action device, and performs corresponding light protection alarm action and heavy protection alarm action according to the degree of the change rate, thereby achieving the purpose of realizing protection through thermal characteristic difference.
2. The method of claim 1, wherein the GIL protection is implemented based on the thermal characteristic anomaly: in the step S1, a thermal characteristic model is established according to the GIL bus structure and the coupling relationship between the electromagnetic field, the fluid field, and the thermal field through COMSOL software, and thermal characteristics of the GIL bus under different environmental conditions and different load currents, including heat conduction inside the conductor and the shell, heat convection in the insulating gas domain and the air domain, and heat radiation of the conductor to the insulating gas and the shell to the insulating gas, are calculated and analyzed, and the shell is heated under the combined action, so that the shell temperature of the GIL bus is obtained.
3. The method of claim 1, wherein the GIL protection is implemented based on the thermal characteristic anomaly: assuming that the normal GIL bus shell temperature change rate is the average value of n groups of data at the stable running time, the normal shell temperature change rate formula is calculated as follows:
in the formula, TkNormal shell temperature values in units; delta TkThe temperature change rate of the normal shell at a certain time is unit ℃; t is simulation time corresponding to the value of the normal shell temperature value, and is unit s; Δ t is the time interval of the temperature change rate value, in units of s; t is t(m)A certain moment of stable operation; t is t(m+1)For stable operation t(m)Time of the next acquisition temperature; delta thetanNormal shell temperature change rate;
the range of the temperature change rate takes the maximum value delta thetanbWith a minimum value Δ θnsTherefore, the range of the positive normal temperature change rate is (Δ θ)ns，Δθnb)；
When an abnormality occurs, partial discharge may occur in a certain phase or multiple phases of the GIL bus or a single-phase ground fault may occur in a certain phase, the current suddenly increases, the temperature change rate is abnormal, and the abnormal case temperature change rate is calculated as follows:
ΔTf＝Tf(h+l)-Tf(h)
Δt＝t(h+1)-t(h)
in the formula, TfThe shell temperature value at the abnormal point is unit; delta TfThe temperature change rate of the abnormal shell at a certain time is unit ℃; t is simulation time corresponding to the value of the temperature value of the abnormal shell, and is unit s; Δ t is the time interval of the temperature change rate value, in units of s; h is a certain time of abnormal operation; delta thetafAbnormal shell temperature change rate;
considering the temperature change rate and the temperature change acceleration in different states:
in the formula,. DELTA.TkThe temperature change rate of the shell of the GIL bus is unit ℃; t is tqThe time and unit s corresponding to the temperature change rate value of the GIL bus shell is obtained;
in daily operation, the possibility of sudden drop or sudden rise of the ambient temperature in a very short time is very low; the leakage of the insulating gas at the flange and the connection part of the GIL bus shell rarely does not influence the pressure of the insulating gas, so that the gas pressure can be considered as a constant value; and the air humidity does not change greatly; meanwhile, the change of the wind speed generally needs a certain time process, and can cause the slow change of the temperature of the GIL bus shell, and the change belongs to the fluctuation within the range of normal change rate.
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