An abnormal monitoring method and system for the loop resistance of a GIS switchgear

Abstract

The invention discloses a method and system for monitoring the abnormality of the loop resistance of a GIS switch device, relates to the field of online monitoring of the operating status and faults of electrical equipment, and solves the problem that there is currently no effective online monitoring of the loop resistance status of GIS switch products. The key points of the technical solution are: including obtaining the composition information of the GIS switch field, and constructing a circuit model of the GIS switch field according to the composition information; obtaining the operating data of the GIS switch field at a certain moment and the measured current of each phase of each switch in the GIS switch field, inputting the operating data into the circuit model of the GIS switch field, and calculating the theoretical current of each phase of each switch; calculating an index through the measured current and the theoretical current of each phase of each switch, analyzing whether the index meets the abnormality criterion, and determining the abnormal switch when the index meets the abnormality criterion; using the existing operating data, all-weather online monitoring can be achieved by comparing the measured value of the switch current with the theoretical calculated value.

Description

Technical Field

[0001] The present invention relates to the field of on-line monitoring of the operating state and faults of electrical equipment. More specifically, it relates to a method and system for abnormal monitoring of the loop resistance of a GIS switchgear. Background Art

[0002] GIS (Gas Insulated Station) is the abbreviation of Gas Insulated Substation. Compared with traditional outdoor open switchgear, GIS switches have the advantages of compact structure and less floor space, and are more and more widely used in power engineering. However, GIS switchgear is a fully enclosed product, and its circuit breaker, disconnector, busbar and other equipment are all enclosed in a shell filled with insulating gas, and the internal state cannot be directly observed, and the defects and hidden dangers are highly concealed and difficult to detect in time.

[0003] There are a large number of conductor connection parts and contacts inside the GIS switchgear. If the quality and process control are not in place during the production and manufacturing and on-site installation processes, it may cause poor contact and an increase in loop resistance. When the load current is small, it may not cause serious problems, but when the load current increases, the heat generation of the poorly contacted joints will increase sharply, rapidly deteriorating the defects, and ultimately leading to contact erosion and short-circuit faults between the conductor and the shell. Therefore, by doing a good job in the on-line monitoring of GIS switchgear and detecting hidden dangers of poor contact as early as possible, the safe operation level of the equipment can be improved, and the losses caused by equipment failures and unplanned outages can be reduced.

[0004] At present, the inspection method for the loop resistance of GIS switchgear needs to be powered off for detection, and the detection period is long, making it difficult to detect defects in time. The live detection method is mainly infrared temperature measurement, which is sensitive to the heat generation of the shell, but it is difficult to detect the heat generation of the internal conductor and is easily interfered by the shell temperature. Generally, an increase in loop resistance will cause a decrease in the current of this loop. In a three-phase system, the state of the switch loop resistance can be inferred by comparing the magnitudes of the three-phase switch currents. However, due to design reasons, some GIS switch products have inherent three-phase unbalanced currents, which will cause interference. To sum up, there is currently no effective means for on-line monitoring of the loop resistance state of GIS switch products. Summary of the Invention

[0005] The purpose of this application is to provide a method and system for abnormal monitoring of the loop resistance of a GIS switchgear, which is convenient for detecting problems with the internal loop resistance of the GIS switchgear as early as possible.

[0006] The above technical purpose of this application is achieved through the following technical solutions: including

[0007] Obtain the composition information of the GIS switchyard, and construct a circuit model of the GIS switchyard according to the composition information;

[0008] Obtain the operation data of the GIS switchyard at a certain moment and the measured current of each phase of each switch in the GIS switchyard, input the operation data into the circuit model of the GIS switchyard, and calculate the theoretical current of each phase of each switch;

[0009] Calculate indicators through the measured current and theoretical current of each phase of each switch, analyze whether the indicators of each string of switches meet the abnormal criterion, and when they are met, locate the abnormal switch.

[0010] Adopting the above technical solution, the circuit model of the GIS switchyard is constructed by obtaining the composition information of the GIS switchyard, the theoretical current is calculated through the circuit model, multiple indicators are calculated through the theoretical current and the measured current, and the switch with loop abnormality is analyzed in combination with the abnormal criterion, which is suitable for the online monitoring of each GIS switch device in the GIS switchyard. There is no need to add additional equipment, and online monitoring can be realized by collecting existing data to locate the abnormal switch.

[0011] Further, the composition information includes: the topological information of the GIS switchyard, the lengths of three-phase conductors of each section, the three-phase resistance and inductance parameters of each section of conductor.

[0012] Further, the operation data includes: bus voltage, switch opening and closing states, and active and reactive power flows of each interval.

[0013] Further, the indicators include: the per-unit value of the measured current, the relative difference between the measured current and the theoretical current, and the absolute difference between the measured current and the theoretical current;

[0014] Among them, the per-unit value of the measured current is the ratio of the measured current to the theoretical current, the relative difference between the measured current and the theoretical current is the per-unit value of the measured current minus the per-unit value of the theoretical current, and the absolute difference between the measured current and the theoretical current is the measured current minus the theoretical current.

[0015] Further, the indicators also include: the per-unit value unbalance degree of the switch, the total absolute difference of a certain phase of switches in a string, and the total relative difference of a certain phase of switches in a string;

[0016] Among them, the per-unit value unbalance degree is the maximum value of the absolute value of the difference between the per-unit values of any two phases of the switch, the total absolute difference is the sum of the absolute differences of a certain phase of switches in a string, and the total relative difference is the sum of the relative differences of a certain phase of switches in a string.

[0017] Further, calculating indicators through the measured current and theoretical current of three phases of each switch includes: calculating the per-unit value, relative difference, and absolute difference of each phase of each switch, calculating the per-unit value unbalance degree of each switch in each string, the total absolute difference of each phase in each string, and the total relative difference of each phase in each string.

[0018] Further, there are four abnormal criteria, including:

[0019] Criterion 1: The relative difference of the switch is less than the relative difference reduction threshold;

[0020] Criterion 2: Among the switches of the same phase in the same string, the relative difference is greater than the relative difference increase threshold, and the relative difference of the switches in the adjacent strings is not 0;

[0021] Criterion 3: The total absolute difference of this string is greater than the total absolute difference threshold;

[0022] Criterion 4: The per-unit value unbalance degree of the switches within the string is greater than the per-unit value unbalance degree threshold.

[0023] Further, analyze whether the indicators of the switches in each string meet the abnormal criteria. When they are met, locate the abnormal switch, including: when the switches of a certain string meet the abnormal criteria, locate this string as the abnormal string, and locate the switch with the actual current decreasing and the largest decreasing amplitude in the abnormal string as the abnormal switch.

[0024] Further, analyze whether the indicators of the switches in each string meet the abnormal criteria. When they are met, locate the abnormal switch, and it also includes: when the switches of multiple strings all meet the abnormal criteria, compare the total absolute difference and the total relative difference of each string, and locate the string with the largest total absolute difference and total relative difference as the abnormal string.

[0025] On the other hand, this application also provides an abnormal monitoring system for the loop resistance of GIS switchgear, including:

[0026] A model construction module, which is used to obtain the composition information of the substation switchyard and construct the circuit model of the substation switchyard according to the composition information;

[0027] A theoretical calculation module, which is used to obtain the operation data of the substation switchyard at a certain moment and the measured current of each switch in the substation switchyard, input the operation data into the circuit model of the substation switchyard, and calculate the theoretical current of each switch;

[0028] An analysis module, which is used to calculate indicators through the measured current and theoretical current of each switch, analyze whether the indicators meet the abnormal criteria, analyze whether the indicators of the switches in each string meet the abnormal criteria, and when they are met, locate the abnormal switch.

[0029] Compared with the prior art, this application has the following beneficial effects:

[0030] 1. The present invention provides a method and system for abnormal monitoring of the loop resistance of a GIS switchgear, which does not require adding new hardware devices. Only by using the composition information and operation data of the existing GIS switchyard and comparing the measured value of the switch current with the theoretically calculated value can all-weather online monitoring be achieved, timely sensing the abnormal change trend of the switch loop resistance, timely discovering potential hidden dangers of poor contact defects in the loop, and avoiding the development of defects into serious faults.

[0031] 2. The principle of the present invention is simple and effective. It uses per-unit value calculation and characterizes the unbalance degree of three-phase currents, and comprehensively defines multiple indicators, which can effectively exclude the interference caused by the inherent current unbalance of the equipment itself. It is an effective method for realizing all-weather online monitoring of the abnormal loop impedance of GIS equipment at low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings:

[0033] Figure 1 is a flowchart of the abnormal detection method provided by an embodiment of the present invention;

[0034] Figure 2 is a wiring diagram of a 500 kV AC GIS switchyard of a certain converter station provided by an embodiment of the present invention;

[0035] Figure 3 is a background screenshot of the switch currents of the 11th and 12th strings provided by an embodiment of the present invention;

[0036] Figure 4 is a circuit model of the GIS switchyard provided by an embodiment of the present invention;

[0037] Figure 5 is a background screenshot of the switch currents of the 7th to 13th strings provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] Hereinafter, the term "including" or "may include" that may be used in various embodiments of the present application indicates the presence of the claimed functions, operations, or elements, and does not limit the addition of one or more functions, operations, or elements. In addition, as used in various embodiments of the present application, the terms "including", "having", and their cognates are only intended to indicate the presence of specific features, numbers, steps, operations, elements, components, or combinations of the foregoing items, and should not be construed as precluding the presence or addition of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing items.

[0039] In various embodiments of the present application, the expression "or" or "at least one of B or / and C" includes any combination or all combinations of the recited words. For example, the expression "B or C" or "at least one of B or / and C" may include B, may include C, or may include both B and C.

[0040] Expressions (such as "first", "second", etc.) used in various embodiments of the present application may modify various components in the various embodiments, but do not limit the corresponding components. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only for the purpose of distinguishing one element from other elements. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, without departing from the scope of the various embodiments of the present application, the first element may be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0041] It should be noted that: if it is described that one component is "connected" to another component or "linked" to another component, the first component may be directly connected to the second component, and a third component may be "connected" between the first component and the second component. Conversely, when one component is "directly connected" to another component or "directly linked" to another component, it can be understood that there is no third component between the first component and the second component.

[0042] The terms used in various embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the various embodiments of the present application. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the present application belong. The terms (such as those defined in a general use dictionary) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in the various embodiments of the present application.

[0043] To make the purpose, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to embodiments and the accompanying drawings. The illustrative embodiments and descriptions thereof of the present application are only for explaining the present application and do not constitute a limitation to the present application.

[0044] Embodiment 1

[0045] This embodiment provides an abnormal monitoring method for the loop resistance of GIS switchgear. By constructing a circuit model of the GIS switchyard to calculate the theoretical current, multiple indicators are calculated based on the theoretical current and the measured current, and the switches with abnormal loops are analyzed through comprehensive abnormal criteria, which is suitable for monitoring each GIS switchgear in the GIS switchyard.

[0046] See Figure 1 as shown Figure 1 which is the flowchart of the abnormal monitoring method. The method includes:

[0047] S1. Obtain the composition information of the GIS switchyard, and construct the circuit model of the GIS switchyard according to the composition information;

[0048] S2. Obtain the operation data of the GIS switchyard at a certain moment and the measured current of each switch in the GIS switchyard, input the operation data into the circuit model of the GIS switchyard, and calculate the theoretical current of each switch;

[0049] S3. Calculate indicators through the measured current and the theoretical current of each switch, analyze whether the indicators of each string of switches meet the abnormal criteria, and when they are met, locate the abnormal switch.

[0050] Specifically, the composition information includes: the topology information of the GIS switchyard, the lengths of the three-phase conductors of each section, the three-phase resistance and inductance parameters of each section of the conductor; the operation data includes: the bus voltage, the switch opening and closing states, and the active and reactive power flows of each interval; taking the bus voltage and the active and reactive power flows of each interval as input conditions, and based on the circuit model established in step S1, the theoretical current of each phase of each switch in the GIS switchyard is calculated by using the electromagnetic transient simulation or power flow calculation method.

[0051] The indicators include: the per-unit value of the measured current (abbreviated as per-unit value), the relative difference between the measured current and the theoretical current (abbreviated as relative difference), the absolute difference between the measured current and the theoretical current (abbreviated as absolute difference), the per-unit value unbalance degree of the switch (abbreviated as per-unit value unbalance degree), the total absolute difference of a certain phase switch in a string (abbreviated as total absolute difference), and the total relative difference of a certain phase switch in a string (abbreviated as total relative difference).

[0052] Specifically, the per-unit value of the current I p.u is the ratio of the measured current to the theoretical current:

[0053]

[0054] where: I mesr is the actual current, and I calc is the theoretical current.

[0055] The relative difference of the current ΔI p.u, which is the per-unit value of the measured current minus the per-unit value of the theoretical current:

[0056] ΔI p.u =(I p.u -1)

[0057] It should be noted that the per-unit value of the theoretical current is the ratio of the theoretical current to the theoretical current, which is 1.

[0058] The absolute current difference ΔI is the measured current minus the theoretical current:

[0059] ΔI = I mesr - I calc .

[0060] The per-unit imbalance unblce p.u is the maximum value of the absolute value of the difference between the per-unit values of any two phases in the switch:

[0061] unblce p.u = Max(|IA p.u - IB p.u |, |IB p.u - IC p.u |, |IA p.u - IC p.u |)

[0062] where IA p.u , IB p.u , IC p.u are the per-unit values of phases A, B, and C of the switch, respectively.

[0063] The total absolute difference ∑AbsDiff_ph is the sum of the absolute differences of a certain phase of the switch in a string:

[0064]

[0065] where ΔI ph_k is the absolute difference of a certain phase of a certain switch in a string, and the subscript ph represents the switch phase A, B, C; k is the switch number, and for 3 / 2 wiring, k takes 3.

[0066] The total relative difference ∑RelDiff_ph is the sum of the relative differences of a certain phase of the switch in a string:

[0067]

[0068] where ΔI p.u_ph_k is the relative difference of a certain phase of a certain switch in a string, and the subscript ph represents the switch phase A, B, C. k is the switch number, and for 3 / 2 wiring, k takes 3.

[0069] Step S3: Calculate indicators based on the measured current and theoretical current of each phase of each switch, analyze whether the indicators of each string of switches meet the abnormal criterion, and when they are met, locate the abnormal switch. This can be divided into three sub-steps, including:

[0070] S31: Calculate indicators based on the measured current and theoretical current of each phase of each switch;

[0071] S32: Analyze whether the indicators meet the abnormal criterion, analyze whether the indicators of each string of switches meet the abnormal criterion, and when they are met, locate the abnormal switch.

[0072] In step S31, calculate indicators based on the measured current and theoretical current of the three phases of each switch, including: calculating the per-unit value, relative difference, and absolute difference of each phase of each switch, calculating the per-unit value unbalance degree of each switch in each string, the total absolute difference of each phase in each string, and the total relative difference of each phase in each string.

[0073] In step S32, regarding the abnormal criterion, it should be noted that when the return resistance of a certain phase of a certain switch is abnormal (increased), due to the increase in the impedance of this switch, the shunt ratio of the interval current between the switches on the 1st bus side and the 2nd bus side is changed, and generally has the following characteristics:

[0074] The current of the switch with abnormal return resistance decreases, and the current of other switches in the same string increases;

[0075] The current of the switches in the adjacent string changes to a certain extent;

[0076] The current change of the string where the switch with abnormal return resistance is located is the most significant, and the current change of the adjacent string farther away is smaller.

[0077] Therefore, based on the above characteristics and combined with the results of the previous quantitative analysis research, the following abnormal criteria are formulated:

[0078] Criterion 1: The relative difference of the switch is less than the relative difference reduction threshold;

[0079] Criterion 2: Among the switches of the same phase in the same string, there is a relative difference greater than the relative difference increase threshold, and the relative difference of the switches in the adjacent string is not 0;

[0080] Criterion 3: The total absolute difference of this string is greater than the total absolute difference threshold;

[0081] Criterion 4: The per-unit value unbalance degree of the switch is greater than the per-unit value unbalance degree threshold.

[0082] After clarifying the criteria, analyze whether the indicators of each string of switches meet the abnormal criteria, and when they are met, locate the abnormal switch:

[0083] When the switches of a certain string simultaneously meet the abnormal criteria 1, 2, 3, and 4, locate this string as the abnormal string, and locate the switch with the actual current decreasing and the largest decreasing amplitude in the abnormal string as the abnormal switch.

[0084] When the switches of multiple strings meet the abnormal criteria, calculate the sum of the total absolute difference and the total relative difference of the strings, and locate the string with the largest sum of the total absolute difference and the total relative difference as the abnormal string.

[0085] It should be noted that the level of current change is related to factors such as the degree of return resistance change, the stringing method of the switchyard, and the operation mode. The threshold should be set in combination with specific projects and user requirements to balance the requirements of sensitivity and reliability.

[0086] This embodiment also provides an abnormal monitoring system for the loop resistance of a GIS switchgear, which is used to implement the abnormal monitoring method as described above, including

[0087] A model construction module, which is used to obtain the composition information of the substation switchyard and construct the circuit model of the substation switchyard according to the composition information;

[0088] A theoretical calculation module, which is used to obtain the operation data of the substation switchyard at a certain moment and the measured current of each switch in the substation switchyard, input the operation data into the circuit model of the substation switchyard, and calculate the theoretical current of each switch;

[0089] An analysis module, which is used to calculate indexes through the measured current and the theoretical current of each switch, analyze whether the indexes meet the abnormal criteria, analyze whether the indexes of each string of switches meet the abnormal criteria, and when they are met, locate the abnormal switch.

[0090] Embodiment 2

[0091] This embodiment applies the abnormal monitoring method provided in Embodiment 1 to a specific GIS switchyard to further illustrate the abnormal monitoring method.

[0092] First, describe the situation of the GIS switchyard. A 500kV AC GIS switchyard of a converter station adopts a 3 / 2 wiring. During operation, it is found that there is a significant three-phase current imbalance in two strings of switches. It is suspected that the direct resistance of the switches is abnormal. It is planned to power off for loop resistance measurement and use the abnormal monitoring method provided in Embodiment 1 for verification calculation.

[0093] See Figure 2 as shown Figure 2 For the wiring diagram of the 500kV AC GIS switchyard of this converter station, the two strings of switches with significant three-phase current imbalance are the 11th string and the 12th string of switches. The current imbalance situation is as Figure 3 shown Figure 3The background screenshots of the switching currents of strings 11 and 12 are shown. It can be seen that the imbalance of the switching currents of strings 11 and 12 is significant. Taking the 5113 switch as an example: the current of phase A is 915.9 A, and the current of phase C is only 789.8 A, with a difference of 126.1 A.

[0094] Step S1: Establish the circuit model of the switchyard

[0095] Collect relevant drawings, and establish the structure of the circuit model according to the GIS switchyard topology; through calculation and combined with on-site measurement, obtain the conductor resistance and inductance parameters in the GIS of a certain substation, and get the specific parameters of the circuit model. See Figure 4 as shown Figure 4 which is the circuit model of the GIS switchyard.

[0096] Step S2: Obtain the data required for calculation and calculate the theoretical current of each phase of each switch

[0097] Obtain the operation data. See Figure 1 as shown. Table 1 shows the operation status of the switchyard at a certain moment, including the bus voltage, the opening and closing status of the switches, and the active and reactive power flows of each interval.

[0098] Table 1 Operation status of the switchyard at a certain moment

[0099]

[0100]

[0101] In addition, see Figure 5 as shown, which gives the measured currents of each phase of each switch monitored by the background at this moment. In this example, the currents of strings 7 to 13 are extracted as the objects of concern and are listed in Table 2.

[0102] Table 2 Measured values of switch currents (unit: A)

[0103]

[0104]

[0105] Step S31: Index calculation

[0106] According to the measured values and theoretical values of the switch currents, calculate the relevant indexes as shown in Tables 4 - 8 below.

[0107] Table 4 Per-unit value I of the measured current p.u (unit: p.u)

[0108] Current / Switch Number 5133 5123 5113 5103 5093 5083 Phase A 0.99 0.97 0.98 0.99 1.04 0.95 Phase B 0.97 1.01 0.99 1.00 1.03 0.97 Phase C 1.01 1.14 1.03 0.98 1.07 0.98 Current / Switch Number 5132 5122 5112 5102 5092 5082 Phase A 1.09 0.95 1.02 0.99 0.95 0.95 Phase B 1.22 1.17 0.97 1.00 0.95 0.97 Phase C 0.96 1.33 0.93 0.98 0.95 0.98 Current / Switch Number 5131 5121 5111 5101 5091 5081 Phase A 1.02 1.01 1.02 0.97 0.95 1.02 Phase B 1.04 0.98 0.97 0.97 0.95 1.00 Phase C 1.06 1.00 0.93 0.99 0.95 1.00

[0109] Table 5 Relative difference ΔI between the measured current and the theoretical current p.u (unit: p.u)

[0110]

[0111]

[0112] Table 6 Total relative difference of strings ∑RelDiff

[0113] Current / Switch Number 13 Strings 12 Strings 11 Strings 10 Strings 8 Strings 7 Strings Phase A 0.12 0.10 0.07 0.04 0.15 0.12 Phase B 0.28 0.20 0.07 0.04 0.12 0.07 Phase C 0.11 0.48 0.16 0.06 0.16 0.04

[0114] Table 7 Per-unit unbalance degree unblce p.u (Unit: p.u.)

[0115] Switch / Strings 13 Strings 12 Strings 11 Strings 10 Strings 8 Strings 7 Strings Switch No. 3 0.04 <![CDATA 0.18 > <![CDATA 0.05 > 0.01 0.04 0.03 Switch No. 2 <![CDATA 0.26 > <![CDATA 0.39 > <![CDATA 0.09 > 0.02 0.01 0.03 Switch No. 1 0.04 0.03 <![CDATA 0.09 > 0.01 0.01 0.02

[0116] Table 8 Absolute difference between measured current and theoretical current ΔI (Unit: A)

[0117] Current / Switch Number 5133 5123 5113 5103 5093 5083 Phase A -6.00 -11.00 -23.00 -4.00 19.00 -35.00 Phase B -21.00 3.00 -7.00 1.00 12.00 -23.00 Phase C 6.00 24.00 22.00 -9.00 28.00 -12.00 Current / Switch Number 5132 5122 5112 5102 5092 5082 Phase A 7.00 -11.00 7.00 -4.00 -42.00 -34.00 Phase B 21.00 20.00 -11.00 1.00 -36.00 -22.00 Phase C -4.00 11.00 -29.00 -9.00 -39.00 -13.00 Current / Switch Number 5131 5121 5111 5101 5091 5081 Phase A 5.00 9.00 7.00 -21.00 -43.00 11.00 Phase B 8.00 -13.00 -11.00 -24.00 -36.00 -1.00 Phase C 15.00 0.00 -29.00 -12.00 -39.00 -1.00

[0118] Table 9 Total absolute difference of strings ∑AbsDiff (Unit: A)

[0119] Current / Switch Number 13 Strings 12 Strings 11 Strings 10 Strings 8 Strings 7 Strings Phase A 18.00 31.00 37.00 29.00 104.00 80.00 Phase B 50.00 36.00 29.00 29.00 84.00 46.00 Phase C 25.00 35.00 80.00 30.00 106.00 26.00

[0120] Step S32: Judging the abnormal return resistance

[0121] According to the abnormal criterion specified in Embodiment 1 and combined with the results of the previous quantitative research, the judgment criteria in this example are as follows:

[0122] Criterion 1: Relative difference ΔI of the switch p.u1 < -0.05;

[0123] Criterion 2: Relative difference ΔI of the switches of the same phase in the same string, and the relative difference ΔI of the switches in adjacent strings p.u2 > 0.3, and the relative difference ΔI of the switches in adjacent strings p.un ≠ 0;

[0124] Criterion 3: The total relative difference of this string is greater than the relative difference total threshold, and the total absolute difference is greater than the total absolute difference threshold, ∑AbsDiff_ph > 200, ∑RelDiff_ph > 0.3;

[0125] Criterion 4: The per-unit unbalance degree of the switches in the string is greater than the per-unit unbalance degree threshold: unblce p.u > 0.1.

[0126] ​​​Referring to Table 4-9, for the actually measured current of the current switch, although some indicators of some switches in the 11th and 12th strings (partial indicators such as per-unit value unbalance degree and relative difference reach the criterion threshold), the total absolute difference of the 11th and 12th strings is relatively low, not meeting the condition for determining that the switch contact resistance increases abnormally. Therefore, it can be considered that there is no obvious abnormality in the contact resistance of each switch in the switch yard under the current state.

[0127] The foregoing case demonstrates the entire implementation process of this method, but there is no defect in the switch contact resistance abnormality in the case. To verify the effectiveness of this method in monitoring and warning the abnormality defect of the loop impedance, a defect is set for verification based on the above case. Since the physical test conditions are not available, the following uses the simulation method to carry out the example verification, taking the simulation value in the state of abnormal contact resistance as the actually measured value and the simulation data in the fault-free state as the theoretical value.

[0128] Taking Phase A of Switch 5113 as the simulation object below, a 1500 μΩ resistor is connected in series in the switch loop to simulate the increase in the contact resistance of the loop. First, the theoretical values of the currents of each switch in the switch yard when the contact resistance of all switches is normal are given, as shown in Table 10.

[0129] Table 10 Current “theoretical” values when there is no abnormality in the switch contact resistance (unit: A)

[0130]

[0131]

[0132] The “actually measured” values of the switch currents in the state where the contact resistance of Switch 5113 increases abnormally by 1500 μΩ are shown in Table 11.

[0133] Table 11 “Actually measured” values of the switch yard currents after the contact resistance of Phase A of Switch 5113 increases abnormally (unit: A)

[0134] Current / Switch Number 5133 5123 5113 5103 5083 5073 Phase A 733 328 883 548 451 733 Phase B 716 255 852 435 437 702 Phase C 700 168 767 412 427 672 Current / Switch Number 5132 5122 5112 5102 5082 5072 Phase A 76 200 509 548 780 733 Phase B 96 119 361 435 799 702 Phase C 110 33 440 412 810 672 Current / Switch Number 5131 5121 5111 5101 5081 5071 Phase A 212 618 509 788 780 479 Phase B 227 690 361 828 799 508 Phase C 243 776 440 855 810 538

[0135] According to the method proposed by the present invention, calculate the criterion indicators:

[0136] The calculation results of the relevant criterion indicators after the contact resistance of Phase A of Switch 5113 increases abnormally are shown in Tables 12-15.

[0137] Table 12 Per-unit value I of the actually measured current p.u (unit: p.u)

[0138]

[0139]

[0140] Table 13 Relative difference ΔI between the actually measured current and the theoretical current p.u (unit: p.u)

[0141] Current / Switch Number 5133 5123 5113 5103 5083 5073 Phase A 0.00 <![CDATA -0.03 > <![CDATA -0.06 > <![CDATA 0.21 > 0.01 0.00 Phase B 0.00 0.00 0.00 0.00 0.00 0.00 Phase C 0.00 0.00 0.00 0.00 0.00 0.00 Current / Switch Number 5132 5122 5112 5102 5082 5072 Phase A -0.04 <![CDATA -0.01 > <![CDATA 0.79 > <![CDATA 0.21 > -0.01 0.00 Phase B 0.00 0.00 0.00 0.00 0.00 0.00 Phase C 0.00 0.00 0.00 0.00 0.00 0.00 Current / Switch Number 5131 5121 5111 5101 5081 5071 Phase A 0.02 <![CDATA 0.01 > <![CDATA 0.79 > <![CDATA -0.03 > -0.01 0.00 Phase B 0.00 0.00 0.00 0.00 0.00 0.00 Phase C 0.00 0.00 0.00 0.00 0.00 0.00

[0142] Table 14 Total relative difference of strings ∑RelDiff

[0143] Phase / Strings 13 Strings 12 Strings 11 Strings 10 Strings 8 Strings 7 Strings Phase A 0.07 0.05 <![CDATA 1.63 > 0.45 0.03 0.01 Phase B 0.00 0.00 0.00 0.00 0.00 0.00 Phase C 0.00 0.00 0.00 0.00 0.00 0.00

[0144] Table 15 Per-unit unbalance degree unblce p.u (Unit: p.u.)

[0145] Switch / Strings 13 Strings 12 Strings 11 Strings 10 Strings 8 Strings 7 Strings Switch No. 3 0.00 0.03 <![CDATA 0.06 > <![CDATA 0.21 > 0.01 0.00 Switch No. 2 0.04 0.01 <![CDATA 0.79 > <![CDATA 0.21 > 0.01 0.00 Switch No. 1 0.02 0.01 <![CDATA 0.79 > 0.03 0.01 0.00

[0146] Table 16 Absolute difference between measured current and theoretical current ΔI (Unit: A)

[0147] Current / Switch Number 5133 5123 5113 5103 5083 5073 Phase A -3.00 -10.00 -56.00 95.00 3.00 2.00 Phase B 0.00 0.00 0.00 0.00 0.00 0.00 Phase C 0.00 0.00 0.00 0.00 0.00 -1.00 Current / Switch Number 5132 5122 5112 5102 5082 5072 Phase A -3.00 -2.00 224.00 95.00 -8.00 2.00 Phase B 0.00 0.00 0.00 5.00 0.00 0.00 Phase C 0.00 0.00 0.00 0.00 0.00 -1.00 Current / Switch Number 5131 5121 5111 5101 5081 5071 Phase A 5.00 9.00 224.00 -21.00 -8.00 -1.00 Phase B 0.00 0.00 0.00 0.00 0.00 0.00 Phase C 0.00 0.00 0.00 0.00 0.00 0.00

[0148] Table 17 Total absolute difference of strings ∑AbsDiff (Unit: A)

[0149] Phase / Strings 13 Strings 12 Strings 11 Strings 10 Strings 8 Strings 7 Strings Phase A 11.00 21.00 504.00 211.00 19.00 5.00 Phase B 0.00 0.00 0.00 5.00 0.00 0.00 Phase C 0.00 0.00 0.00 0.00 0.00 2.00

[0150] According to the criteria formulated by the present invention, the criteria are compared item by item for judgment. Among them, the switch currents of strings 10, 11, and 12 have changed. The current change of string 12 is slight and can be ignored. The current changes of strings 10 and 11 are significant. The following is an index analysis.

[0151] (1) Criterion 1: Relative difference of the switch ΔI p.u1 <-0.05;

[0152] For string 11: ΔI of phase A of switch 5113 p.u =-0.06 meets

[0153] For string 10: ΔI of phase A of switch 5101 p.u =-0.03 is close to the threshold but does not meet the threshold.

[0154] (2) For switches of the same phase in the same string, the relative difference of the switch ΔI p.u2 >0.3, and for switches of adjacent strings, the relative difference of the switch ΔI p.un ≠0;

[0155] For string 11: Except that the current of phase A of switch 5133 decreases, the currents of phase A of the other two switches 5132 and 5131 increase, and the amplitude is ΔI p.u =0.79, which is greater than the threshold 0.3.

[0156] For string 10: The amplitudes of the currents of phase A of switches 5103 and 5102 increase, but the relative amplitude ΔI p.u =0.21, which is less than the discrimination threshold.

[0157] The currents of the 9th, 10th, and 11th adjacent strings all have offsets.

[0158] (3) Criterion 3: The total relative difference of this string is greater than the total relative difference threshold, and the total absolute difference is greater than the total absolute difference threshold, ∑AbsDiff_ph>200, ∑RelDiff_ph>0.3;

[0159] For the 11th string: ∑AbsDiff_A = 504, ∑RelDiff_A = 1.63. Both the absolute difference and the relative difference meet the criteria.

[0160] For the 10th string: ∑AbsDiff_A = 211, ∑RelDiff_A = 0.45. The absolute difference does not meet the criteria, while the relative difference meets the criteria.

[0161] (4) Criterion 4: The per-unit unbalance degree of the switches within the string is greater than the per-unit unbalance degree threshold: unblce p.u >0.1.

[0162] For the 11th string: unblce p.u = 0.21, reaching the discrimination threshold

[0163] For the 10th string: unblce p.u = 0.79, reaching the discrimination threshold

[0164] The switches of the 11th string simultaneously meet Criteria 1, 2, 3, and 4, and 5133 is the one with decreasing current. It is determined that the current return resistance of the 5133 switch has increased abnormally.

[0165] The switches of the 10th string meet Criteria 3 and 4 but do not meet Criteria 1 and 2, and are not determined to have an abnormally increased return resistance in this example.

[0166] Under certain setting conditions, both the 10th and 11th strings may meet Criteria 1, 2, 3, and 4. At this time, according to Judgment Rule 2, "When more than one string of switches meets the above Criteria 1, 2, 3, and 4, sort them comprehensively according to the total absolute difference and the total relative difference. The string of switches with a larger total absolute difference and total relative difference in the absolute value of the current change of the three switches should be considered more likely to have an abnormal return resistance and should be prioritized for investigation." Since both the absolute difference and the relative difference of Phase A of the switches in the 11th string are greater than those in the 10th string, it should be determined that the switches in the 11th string are abnormal first, and no misjudgment will occur.

[0167] The above results determine that the return resistance of the 5133 switch has increased abnormally, which is consistent with the preset fault, indicating that the method proposed by the present invention is effective.

[0168] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An abnormal monitoring method and system for the loop resistance of a GIS switchgear, characterized in that: including Obtaining the composition information of the GIS switchyard, and constructing a circuit model of the GIS switchyard according to the composition information; Obtaining the operation data of the GIS switchyard at a certain moment and the measured current of each phase of each switch in the GIS switchyard, inputting the operation data into the circuit model of the GIS switchyard, and calculating the theoretical current of each phase of each switch; Calculating indexes through the measured current and the theoretical current of each phase of each switch, analyzing whether the indexes of each string of switches meet the abnormal criterion, and when meeting, locating the abnormal switch; The composition information includes: the topology information of the GIS switchyard, the lengths of three-phase conductors of each section, the three-phase resistance and inductance parameters of each section of conductor; The operation data includes: bus voltage, switch opening and closing states, and active and reactive power flows of each interval; The indexes include: the per-unit value of the measured current, the relative difference between the measured current and the theoretical current, and the absolute difference between the measured current and the theoretical current; wherein, the per-unit value of the measured current is the ratio of the measured current to the theoretical current, the relative difference between the measured current and the theoretical current is the per-unit value of the measured current minus the per-unit value of the theoretical current, and the absolute difference between the measured current and the theoretical current is the measured current minus the theoretical current; The indexes also include: the per-unit value unbalance degree of the switch, the total absolute difference of a certain phase of switches in a string, and the total relative difference of a certain phase of switches in a string; wherein, the per-unit value unbalance degree is the maximum value of the absolute value of the difference between the per-unit values of any two phases of the switch, the total absolute difference is the sum of the absolute differences of a certain phase of switches in a string, and the total relative difference is the sum of the relative differences of a certain phase of switches in a string; Calculating indexes through the measured current and the theoretical current of three phases of each switch, including: calculating the per-unit value, relative difference and absolute difference of each phase of each switch, calculating the per-unit value unbalance degree of each switch in each string, the total absolute difference of each phase in each string, and the total relative difference of each phase in each string; There are four abnormal criteria, including: Criterion 1: The relative difference of the switch is less than the relative difference reduction threshold; Criterion 2: Among the switches of the same string and the same phase, there is a relative difference greater than the relative difference increase threshold, and there is a switch in the adjacent string with a non-zero relative difference; Criterion 3: The total absolute difference of this string is greater than the total absolute difference threshold; Criterion 4: The per-unit value unbalance degree of the switches in the string is greater than the per-unit value unbalance degree threshold; Analyzing whether the indexes of each string of switches meet the abnormal criterion, and when meeting, locating the abnormal switch, including: when the switches of a certain string meet the abnormal criterion, locating this string as an abnormal string, and locating the switch with the reduced actual current and the largest reduction amplitude in the abnormal string as the abnormal switch; Analyzing whether the indexes of each string of switches meet the abnormal criterion, and when meeting, locating the abnormal switch, further including: when the switches of multiple strings all meet the abnormal criterion, comparing the total absolute difference and the total relative difference of each string, and locating the string with the largest total absolute difference and the largest total relative difference as the abnormal string.

2. An abnormal monitoring system for the loop resistance of a GIS switchgear, characterized in that: Performing the abnormal monitoring method as described in claim 1, including A model construction module, which is used to obtain the composition information of the substation switchyard and construct a circuit model of the substation switchyard according to the composition information; A theoretical calculation module, which is used to obtain the operation data of the substation switchyard at a certain moment and the measured current of each switch in the substation switchyard, input the operation data into the circuit model of the substation switchyard, and calculate the theoretical current of each switch; An analysis module, which is used to calculate indexes through the measured current and theoretical current of each switch, calculate indexes through the measured current and theoretical current of each phase of each switch, analyze whether the indexes of each string of switches meet the abnormal criterion, and locate the abnormal switch when it is satisfied.

Images