Cable terminal field lightning arrester resistive current live detection method and system

Abstract

The invention discloses a cable terminal field lightning arrester resistive current live-line detection method and system, and the method comprises the steps: building a relation between a cable terminal and a starting end voltage vector based on a transformer substation, a cable line and an overhead line system equivalent circuit, inputting the models and lengths of a cable and an overhead line, and a voltage vector of a far-end transformer substation; and the voltage vector of the end part of the lightning arrester of the cable terminal field is obtained through calculation, and basic data is provided for resistive current measurement of the lightning arrester of the cable terminal field. The method comprises the following steps: establishing a phase relation between a cable terminal and a starting end voltage; establishing the relationship between the electrical parameters of the typical cable and the overhead line and the actual model, length and other input quantities; measuring a voltage vector of a source-end transformer substation; and calculating to obtain a voltage vector of the end part of the lightning arrester in the cable terminal field so as to obtain a voltage phase of the end part of the lightning arrester. The method is creatively embodied in that the cable terminal field lightning arrester end voltage phase measurement problem is converted into circuit equation solving, the physical significance is clear, and the calculation process is simple.

Description

Technical Field

[0001] The invention relates to the technical field of resistive current measurement of lightning arresters in the electric power industry, and in particular to a method and system for detecting resistive current of lightning arresters in a cable terminal field. Background Art

[0002] As the mainstream overvoltage protection device of the power system, the operating status of the gapless metal oxide arrester (hereinafter referred to as "arrester") is very important for the safe and reliable operation of the power system. The arrester bears the system operating voltage and short-term overvoltage for a long time. The resistive current that characterizes the active power loss of the arrester has become the most critical indicator for measuring the arrester status. Live detection and online monitoring with resistive current as the target have become the main means of arrester status monitoring. Among them, resistive current live detection has replaced the power outage DC leakage current test and become an annual preventive test item for arresters.

[0003] For some 220kV and 110kV substations (such as urban substations or substations in heavily loaded areas), due to land acquisition and other reasons, the outgoing lines from the substation must pass through a section of 220kV or 110kV cable to the cable terminal field, where they are converted into overhead lines. A set of lightning arresters must be installed at the cable terminal as overvoltage protection.

[0004] The equivalent circuit of the lightning arrester can be regarded as the parallel connection of the ground capacitance C and the nonlinear resistance R. Accordingly, the total ground leakage current (hereinafter referred to as "total current") I of the lightning arrester is composed of the superposition of the capacitive current Ic and the resistive current IR. The capacitive current leads the voltage at the end of the lightning arrester by 90° and is less affected by the operating state of the lightning arrester. The resistive current is in phase with the voltage at the end of the lightning arrester and is closely related to the operating state of the lightning arrester. It reflects the active loss of the lightning arrester resistor and internal insulation, and is a key indicator for evaluating the operating state of the lightning arrester.

[0005] Since the capacitive current Ic accounts for more than 90% of the total current I, the resistive current I R The proportion is very low, and the change of resistive current is difficult to be reflected from the change of total current I, that is, it is impossible to effectively perceive the change of the operating state of the lightning arrester from the total current. Therefore, it is necessary to decouple the capacitive current and the resistive current. The mainstream method to solve this problem is the capacitive current compensation method. This method obtains the phase of the end voltage based on the measured voltage signal at the end of the lightning arrester, shifts the phase by 90° to obtain the phase of the equivalent capacitive current, constructs the capacitive current vector, subtracts the capacitive current vector from the total current vector, and adopts the idea of ​​approximation by minimization method. Through the adjustment and reconstruction of the capacitive current, the separated resistive current component is minimized. At this time, it is considered that the capacitive current is fully compensated, so that the resistive current component is obtained by compensating the capacitive current.

[0006] It can be seen that the core of the capacitive current compensation method is to obtain the phase of the voltage at the end of the arrester. For the arrester inside the substation, it can be obtained by extracting the secondary voltage signal of the voltage transformer (hereinafter referred to as "PT") of the same bus section as the arrester being measured; for the arrester in the cable terminal field, since the cable terminal field is not equipped with a voltage transformer, it is impossible to obtain the voltage signal at the end of the arrester, and the conditions of the capacitive current compensation method cannot be met. The arrester in the cable terminal field does not have the conditions for resistive current live detection, which becomes a blind spot for the arrester live detection. The operating status of the arrester can only be roughly grasped through the full current monitor and infrared detection configured by the arrester, and the annual preventive test of the arrester cannot be carried out--the resistive current live detection. This problem seriously troubles the grassroots operation and maintenance departments.

[0007] The patent of the present invention proposes a solution and detection system for the above problems. From the voltage signal at the end of the cable line at the substation end, the voltage at the end of the lightning arrester in the cable terminal field is calculated based on the circuit principle, thereby obtaining the voltage phase information at the end of the lightning arrester, providing basic data for the live detection of resistive current in the lightning arrester in the cable terminal field, and based on the capacitive current compensation method, the resistive current is calculated from the total current of the lightning arrester. Summary of the invention

[0008] The embodiment of the present invention provides a method and system for detecting the resistive current of a lightning arrester in a cable terminal field. The idea is to establish an equivalent circuit of a substation, a cable line, and an overhead line. Based on the relationship between the electrical parameters of typical 220kV and 110kV cables and overhead lines and input quantities such as actual models and lengths, the voltage vector at the end of the cable line at the source-end substation is calculated to obtain the voltage vector at the end of the lightning arrester in the cable terminal field. The voltage vector is used as the basic data for calculating the capacitive current compensation method. Based on the capacitive current compensation method, the resistive current is calculated from the total current of the lightning arrester.

[0009] The embodiment of the present invention provides a method for detecting the resistive current of a cable terminal field lightning arrester, comprising six steps:

[0010] S1: Establish the relationship between the voltage vectors of the cable terminal node and the starting node;

[0011] S2: Establish the relationship between the electrical parameters, models and lengths of typical cables and overhead lines;

[0012] S3: Measure the voltage vector at the end of the cable line to be tested at the source substation;

[0013] S4: Calculate the voltage vector at the end of the arrester in the cable terminal field;

[0014] S5: Measure the total current vector flowing through the cable terminal field arrester;

[0015] S6: Based on the capacitive current compensation method, the resistive current flowing through the cable terminal field arrester is obtained.

[0016] The embodiment of the present invention provides a cable terminal field arrester resistive current live detection system, comprising three units: a starting end voltage vector measurement unit 11 of the cable line to be tested, a cable terminal field voltage vector solution unit 12, and a cable terminal field arrester resistive current calculation and display unit 13, such as Figure 3 shown.

[0017] The starting end voltage vector measuring unit 11 of the cable line to be tested includes three modules: a starting end voltage vector measuring module 111 of the cable line to be tested, a signal sending module 112, and a signal receiving module 113. Figure 3 shown.

[0018] The cable terminal field voltage vector solution unit 12 includes three modules: a cable and overhead line electrical parameter conversion module 121, a cable and overhead line voltage level, model and length parameter input module 122, and a cable terminal field voltage vector calculation module 123. Figure 3 shown.

[0019] The cable terminal field arrester resistive current calculation and display unit 13 includes three modules: a cable terminal field arrester full current measurement module 131, a resistive current calculation module 132, and an output display module 133. Figure 3 shown.

[0020] The embodiments of the present invention have the following advantages:

[0021] (1) At present, since the cable terminal field is not equipped with a voltage transformer, the voltage signal at the end of the lightning arrester cannot be obtained, and the conditions for the capacitive current compensation method cannot be met. The lightning arrester at the cable terminal field does not have the conditions for conducting the annual preventive test - resistive current live detection, which becomes a blind spot for lightning arrester live detection. The method and system of the present invention solve the problem of obtaining the voltage phase at the end of the lightning arrester at the cable terminal field, and the pain point of resistive current live detection is solved.

[0022] (2) The method of the present invention is based on circuit principles and converts the problem of obtaining the voltage phase at the end of the lightning arrester in the cable terminal field into solving a circuit equation. It only requires inputting basic information such as the cable and overhead line model and length based on the initial voltage phase measurement results of the cable end in the remote substation to obtain the voltage phase at the end of the lightning arrester in the cable terminal field. The processing process is simple and does not add additional measurement links to grassroots measurement personnel.

[0023] The creativity of the method and system of the present invention is reflected in the conversion of the voltage phase measurement problem of the cable terminal field arrester end into the solution of a circuit equation. The physical meaning is clear and the calculation process is simple. There is no need to add measurement links to grassroots measurement personnel. Basic data is provided for the resistive current measurement of the cable terminal field arrester. The resistive current is calculated from the full current measurement result by a capacitive current compensation method, and a corresponding cable terminal field arrester resistive current live detection system is provided, thereby solving the problem that the cable terminal field arrester cannot carry out resistive current live detection, which has long troubled grassroots test personnel of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1 Equivalent circuit diagram of the substation, cable outlet and overhead line system of the present application method;

[0026] Figure 2 A flowchart of the invention method of this application;

[0027] Figure 3 This is a principle block diagram of the system of the present invention;

[0028] Figure 4 This is a schematic diagram of the implementation steps of an embodiment of the invention method of this application. DETAILED DESCRIPTION

[0029] The embodiment of the present invention provides a method and system for detecting live resistive current in a cable terminal field lightning arrester, which converts the problem of measuring the voltage phase at the end of the cable terminal field lightning arrester into solving a circuit equation. The method has clear physical meaning and simple calculation process, and provides basic data for measuring resistive current in the cable terminal field lightning arrester, thereby solving the problem that the cable terminal field lightning arrester cannot carry out live resistive current detection, which has long troubled grassroots test personnel in the power system.

[0030] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] See also Figure 4 An embodiment of a method for detecting the resistive current of a lightning arrester in a cable terminal field provided by an embodiment of the present invention comprises the following six steps:

[0032] 101. Establish the relationship between the voltage vectors of the cable terminal node and the starting node.

[0033] Build an equivalent circuit model of the substation, cable line, and overhead line system, including the equivalent circuit parameters of the remote substation, the resistance, inductance, and capacitance to ground per unit length of the cable line, the resistance, inductance, and capacitance to ground per unit length of the overhead line, and the equivalent circuit parameters of the load side.

[0034] According to the model, the relationship expression between the voltage phase of the cable terminal node and the voltage vector of the cable starting node of the source substation is solved.

[0035] like Figure 1 As shown, generally, the source-end substation adopts a power supply model, and the system impedance on both sides of the line is equivalent to pure inductance (such as a 220kV system with an inductance value of 30mH). The cable line and overhead line can be equivalent to a combination of resistance, inductance and ground capacitance respectively. The ground capacitance per unit length of the cable line is much larger than that of the overhead line, and R1 and R2 are DC resistances.

[0036] By solving the circuit, we can get the voltage vector of the cable terminal field node: The voltage vector at the cable start end The relationship between.

[0037] 102. Establish the relationship between the electrical parameters, models and lengths of typical cables and overhead lines.

[0038] For typical 220kV, 110kV cables and overhead lines, their electrical parameters are characterized by unit length resistance, inductance and capacitance to ground. For a certain type of cable, its unit length electrical parameters are certain, and It changes in proportion to the length. For overhead lines of a certain voltage level, the electrical parameters do not change significantly with design and height, so a uniform value can be used in engineering.

[0039] The information in the equipment information system of the equipment management unit is generally the voltage level, model and length of cables and overhead lines, and there is a one-to-one correspondence with their electrical parameters, that is, the electrical parameters of cables and overhead lines can be obtained through voltage level, model and length.

[0040] By setting the conversion link, the voltage level, model and length of the cable and overhead line can be used as input quantities to obtain the electrical parameters (C1, R1, L1, C2, R2, L2) of the cable and overhead line.

[0041] 103. Measure the voltage vector at the starting end of the cable line to be tested at the source-end substation.

[0042] The voltage vector is measured on the same busbar as the source substation and the cable to be tested. Generally, the voltage signal is read from the secondary side of the bus voltage transformer (PT cabinet), which is the voltage vector at the starting end of the cable line to be tested.

[0043] The voltage vector information is transmitted to the cable terminal field by wireless transmission, public network signal and other means.

[0044] 104. Calculate the voltage vector at the end of the lightning arrester at the cable terminal field.

[0045] Input voltage level, model and length of cable line and overhead line, and starting end voltage vector of the cable line to be tested at the source substation, and calculate the end voltage vector of the lightning arrester in the cable terminal field according to steps 102 and 101, so as to obtain the end voltage phase of the lightning arrester in the cable terminal field.

[0046] 105. Measure the total current vector flowing through the cable terminal field arrester.

[0047] A temporary bypass cable terminal field arrester three-phase counter is used to measure the full current vector flowing through the cable terminal field arrester.

[0048] The total current is the total leakage current vector flowing through the arrester, including the capacitive current vector and the resistive current vector.

[0049] 106. Based on the capacitive current compensation method, the resistive current flowing through the cable terminal field arrester is obtained.

[0050] The current mainstream capacitive current compensation method is adopted. According to the arrester end voltage phase obtained by 104 solution, the phase is shifted by 90° to obtain the phase of the equivalent capacitive current, and the capacitive current vector is constructed. The capacitive current vector is subtracted from the full current vector. The idea of ​​approximation by minimization method is adopted. Through the adjustment and reconstruction of the capacitive current, the separated resistive current component is minimized. At this time, it is considered that the capacitive current is fully compensated, so the resistive current component is obtained by compensating the capacitive current.

[0051] See also Figure 3 An embodiment of the cable terminal field lightning arrester resistive current live detection system provided by an embodiment of the present invention includes the following three units: a starting end voltage vector measurement unit 11 of the cable line to be tested, a cable terminal field voltage vector solution unit 12, and a cable terminal field lightning arrester resistive current calculation and display unit 13.

[0052] The starting end voltage vector measuring unit 11 of the cable line to be tested comprises three modules: a starting end voltage vector measuring module 111 of the cable line to be tested, a signal sending module 112 and a signal receiving module 113 .

[0053] The starting end voltage vector measurement module 111 of the cable line to be tested is used in the source end substation to measure the voltage vector on the same bus as the cable to be tested. Generally, the voltage signal is read through the PT secondary side of the bus voltage transformer (PT cabinet) to obtain the starting end voltage vector of the cable line to be tested.

[0054] The signal sending module 112 is used in the source-end substation to transmit the voltage vector information to the cable terminal field, and can be transmitted by wireless transmission, public network signal, etc.

[0055] The signal receiving module 113 is used at the arrester to be tested in the cable terminal field to receive the voltage vector signal of the starting end of the cable line to be tested and obtain the voltage phase of the starting end of the cable line to be tested.

[0056] The cable terminal field voltage vector solution unit 12 includes three modules: a cable and overhead line electrical parameter conversion module 121, a cable and overhead line voltage level, model and length and other parameter input module 122, and a cable terminal field voltage vector calculation module 123.

[0057] The cable and overhead line electrical parameter conversion module 121 is used to obtain the voltage vector of the cable terminal field node. The voltage vector at the cable start end The relationship between And establish the association between the voltage level, model and length of cables and overhead lines and the electrical parameters (C1, R1, L1, C2, R2, L2) of cables and overhead lines.

[0058] The parameter input module 122 of the voltage level, model and length of cables and overhead lines is used to input the cable and overhead line information in the equipment information system of the equipment management unit, generally the parameters such as voltage level, model and length.

[0059] The cable terminal field voltage vector calculation module 123 calculates the cable terminal field voltage vector according to the cable and overhead line electrical parameter conversion module 121 and the voltage level, model and length of the cable and overhead line parameter input module 122 to obtain the phase of the cable terminal field arrester end voltage.

[0060] The cable terminal field arrester resistive current calculation and display unit 13 comprises three modules: a cable terminal field arrester full current measurement module 131 , a resistive current calculation module 132 , and an output display module 133 .

[0061] The cable terminal field lightning arrester full current measurement module 131 is used to measure the full current vector flowing through the cable terminal field lightning arrester, which is generally measured by temporarily bypassing the cable terminal field lightning arrester three-phase counter.

[0062] The resistive current calculation module 132 is used to calculate the resistive current flowing through the cable terminal field lightning arrester by the capacitive current compensation method, wherein the cable terminal field lightning arrester end voltage phase obtained by the cable terminal field voltage vector calculation module 123 can be realized by automatic import, and the calculation program of the capacitive current compensation method can be solidified into this module.

[0063] The output display module 133 is used to output the resistive current detection result of the cable terminal field arrester.

[0064] The above is a detailed description of a method and system for detecting resistive current live in a cable terminal field lightning arrester. Its creativity is reflected in converting the problem of measuring the voltage phase at the end of the cable terminal field lightning arrester into solving a circuit equation. It has clear physical meaning and a simple calculation process. It does not require additional measurement links for grassroots measurement personnel. It provides basic data for resistive current measurement of cable terminal field lightning arresters, calculates resistive current from the full current measurement results through a capacitive current compensation method, and provides a corresponding resistive current live detection system for cable terminal field lightning arresters, thereby solving the problem of the inability to carry out resistive current live detection in cable terminal field lightning arresters, which has long plagued grassroots test personnel in power systems.

[0065] The embodiments of the present invention have the following main technical advantages:

[0066] (1) At present, since the cable terminal field is not equipped with a voltage transformer, the voltage signal at the end of the lightning arrester cannot be obtained, and the conditions for the capacitive current compensation method cannot be met. The lightning arrester at the cable terminal field does not have the conditions for conducting the annual preventive test - resistive current live detection, which becomes a blind spot for lightning arrester live detection. The method of the present invention solves the problem of obtaining the voltage phase at the end of the lightning arrester at the cable terminal field, and the pain point of resistive current live detection is solved.

[0067] (2) The method of the present invention is based on circuit principles and converts the problem of obtaining the voltage phase at the end of the lightning arrester in the cable terminal field into solving a circuit equation. It only requires inputting basic information such as the cable and overhead line model and length based on the initial voltage phase measurement results of the cable end in the remote substation to obtain the voltage phase at the end of the lightning arrester in the cable terminal field. The processing process is simple and does not add additional measurement links to grassroots measurement personnel.

[0068] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cable terminal field arrester resistive current live detection system, characterized in that: The system comprises three units: a voltage vector measuring unit 11 for the starting end of the cable line to be tested, a voltage vector solving unit 12 for the cable terminal field, and a resistive current calculation and display unit 13 for the lightning arrester for the cable terminal field.

2. According to claim 1, a cable terminal field arrester resistive current live detection system is characterized in that: The starting end voltage vector measuring unit 11 of the cable line to be tested comprises three modules: a starting end voltage vector measuring module 111 of the cable line to be tested, a signal sending module 112 and a signal receiving module 113 .

3. According to claim 1, a cable terminal field arrester resistive current live detection system is characterized in that: The cable terminal field voltage vector solution unit 12 includes three modules: a cable and overhead line electrical parameter conversion module 121, a cable and overhead line voltage level, model and length and other parameter input module 122, and a cable terminal field voltage vector calculation module 123.

4. According to claim 1, a cable terminal field arrester resistive current live detection system is characterized in that: The cable terminal field arrester resistive current calculation and display unit 13 includes three modules: a cable terminal field arrester full current measurement module 131 , a resistive current calculation module 132 and an output display module 133 .

5. A method for detecting the resistive current of a cable terminal arrester according to claims 1 to 4, characterized in that: It includes 6 steps: S1: Establish the relationship between the voltage vectors of the cable terminal node and the starting node; S2: Establish the relationship between the electrical parameters, models and lengths of typical cables and overhead lines; S3: Use the starting end voltage vector measurement module 111 of the cable line to be tested to measure the end voltage vector of the cable line to be tested at the source end substation; S4: Calculate the voltage vector at the end of the lightning arrester in the cable terminal field using the cable terminal field voltage vector calculation module 123; S5: Use the cable terminal field lightning arrester full current measurement module 131 to measure the full current vector flowing through the cable terminal field lightning arrester; S6: Based on the capacitive current compensation method, the resistive current flowing through the cable terminal field arrester is obtained.

6. The method for detecting the resistive current of a lightning arrester in a cable terminal field according to claim 5, characterized in that: Step S1 specifically includes: An equivalent circuit model of the substation, cable line, and overhead line system is established, including the equivalent circuit parameters of the remote substation, the resistance, inductance, and capacitance to ground per unit length of the cable line, the resistance, inductance, and capacitance to ground per unit length of the overhead line, and the equivalent circuit parameters of the load side. According to the model, the relationship between the voltage vector of the cable terminal node and the voltage vector of the cable starting node at the source substation is obtained.

7. The method for detecting the resistive current of a cable terminal arrester according to claim 5, characterized in that: Step S2 specifically includes: For typical cables and overhead lines, there is a one-to-one correspondence between their electrical parameters (resistance, inductance and capacitance to ground) and the information in the equipment information system of the equipment management unit (such as voltage level, model and length). A conversion link is set up, and the voltage level, model and length are input to obtain the electrical parameters of the cables and overhead lines.

8. The method for detecting the resistive current of a lightning arrester in a cable terminal field according to claim 5, characterized in that: Step S3 specifically includes: The voltage vector of the starting end of the cable line to be tested is read at the secondary side of the PT of the same busbar as the cable to be tested at the source substation.

9. The method for detecting the resistive current of a cable terminal arrester according to claim 5, characterized in that: Step S4 specifically includes: The model and length of the cable line and overhead line are input, and the voltage vector at the end of the cable terminal field lightning arrester is calculated according to S1, S2 and S3, so as to obtain the voltage phase at the end of the cable terminal field lightning arrester.

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