Frequency selection matching device and method in long-distance GIL field voltage withstand test

Abstract

The invention discloses a frequency-selecting matching device and a frequency-selecting matching method for a long-distance GIL field voltage withstand test, a resistance-capacitance network with impedance changing along with frequency is arranged at the tail end of a long-distance GIL, the resistance-capacitance network is in a high-resistance state under alternating voltage, the high-voltage arm function of a voltage divider is realized, alternating voltage measurement is performed, and the frequency-selecting matching device and the frequency-selecting matching method for the long-distance GIL field voltage withstand test are realized. According to the invention, the device is in a low-resistance state under transient breakdown traveling wave voltage, achieves the function of impedance matching, and achieves the matching and absorption of the transient traveling wave voltage at the tail end, thereby greatly suppressing and even eliminating the refraction and reflection of the transient traveling wave voltage, and further suppressing the problem of multi-point secondary discharge generated by breakdown transient traveling waves in the long-distance G-IL field withstand voltage.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power equipment, and in particular to a frequency selection and matching device and method in a long-distance GIL on-site withstand voltage test. Background Art

[0002] As a high-voltage, high-current, long-distance power transmission equipment, gas-insulated metal-enclosed transmission line (GIL) has been widely used in power systems due to its advantages of large transmission capacity, low loss, small footprint, and high operational reliability. GIL performs particularly well in complex terrain and harsh climatic conditions.

[0003] On-site withstand voltage test is a key link to ensure the insulation reliability of GIL. At present, all GILs must undergo AC withstand voltage test after on-site installation to assess their insulation, which has become a routine link specified by the standard. In recent years, a new phenomenon and problem has emerged in the process of GIL on-site withstand voltage test, that is, the phenomenon of multi-point breakdown of GIL under AC withstand voltage. In particular, with the increase of GIL distance, the probability of multi-point breakdown is higher. The main reason is that: although the test voltage of AC withstand voltage is a steady-state voltage, once the insulation breakdown is caused by some random factors or local defects, a significant transient traveling wave overvoltage will be generated. Because the GIL end bushing is approximately open-circuited, the transient traveling wave overvoltage will further produce complex refraction, reflection and superposition processes in the long-distance GIL, and propagate in the long-distance GIL, thereby forming an overvoltage wave with a higher peak value, which will cause repeated insulation threats to the entire long-distance GIL and cause secondary multiple discharge phenomena. The on-site positioning of secondary discharge is very difficult, and because it involves multiple gas chambers, it seriously affects the difficulty of GIL on-site testing and maintenance, and has a great impact on the construction period and benefits of GIL projects. Summary of the invention

[0004] The present invention aims to solve the deficiencies of the above-mentioned prior art and provides a frequency selective matching device and a frequency selective matching method for a long-distance GIL on-site withstand voltage test, thereby realizing the dual functions of the high-voltage arm of the voltage divider and the matching impedance, greatly suppressing or even eliminating the refraction and reflection of the transient traveling wave voltage, and thereby suppressing the problem of multi-point secondary discharges caused by the breakdown of transient traveling waves in the long-distance GIL on-site withstand voltage.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A frequency selection and matching device in a long-distance GIL on-site withstand voltage test comprises an on-site quick docking unit and a resistor and capacitor network whose impedance varies with frequency, which are connected in sequence. The resistor and capacitor network is a resistor and capacitor network composed of multiple resistors and capacitors connected in series. The resistor and capacitor network is connected to a long-distance GIL pipeline through the on-site quick docking unit and a long-distance GIL casing. The long-distance GIL pipeline is connected to an industrial frequency experimental power supply through the long-distance GIL casing at the other end.

[0007] As a further technical solution of the present invention: the long-distance GIL pipeline is provided with a plurality of pot-type insulators and three-pillar insulators.

[0008] As a further technical solution of the present invention: the on-site quick docking unit is a high-voltage busbar, and the high-voltage busbar is a vertical external connection structure.

[0009] As a further technical solution of the present invention: the on-site quick docking unit is a docking flange, and the docking flange is an armored straight-insertion structure.

[0010] A frequency selection and matching method in a long-distance GIL field withstand voltage test, using the above-mentioned frequency selection and matching device, comprises the following steps:

[0011] Step S102, obtaining parameters of the GIL and calculating its impedance characteristics;

[0012] Step S104, obtaining parameters of instruments required for the test and calculating impedance characteristics of the generating circuit and the measuring circuit;

[0013] Step S106, designing a matching network according to the impedance characteristics of the GIL;

[0014] Step S108, impedance matching is achieved by selecting similar instruments required for the test or adding additional electrical components to the circuit.

[0015] As a further technical solution of the present invention: Step S102 includes: obtaining basic parameters of the length, conductor material, conductor cross-section and insulation material of the GIL; calculating R, L, C parameters and characteristic parameter Z per unit length; and calculating the GIL impedance characteristics in combination with frequency influence.

[0016] As a further technical solution of the present invention: the step S104 includes: obtaining the parameters of the instruments required for the test and establishing a circuit model; calculating the impedance characteristics according to the model in combination with the frequency domain analysis method; and verifying the calculation results by actual measurement per unit length.

[0017] As a further technical solution of the present invention: it also includes a verification step, specifically: circuit simulation is performed according to the parameters of the GIL and the instrument to verify the matching network.

[0018] As a further technical solution of the present invention: it also includes further matching optimization of the impulse voltage generator and the high-voltage wire, which is achieved by adjusting the output impedance and transmission frequency parameters of the device.

[0019] As a further technical solution of the present invention: during the on-site pressure withstand test of the long-distance GIL, it is necessary to monitor the voltage and current parameters in the long-distance GIL pipeline and record the test data. By analyzing the test data, the operating performance of the GIL under lightning impulse conditions is evaluated.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention sets a RC network whose impedance changes with frequency at the end of the long-distance GIL. The RC network presents a "high resistance" state under AC voltage, realizes the high-voltage arm function of the voltage divider, and performs AC voltage measurement. The RC network presents a "low resistance" state under transient breakdown traveling wave voltage, realizes the function of matching impedance, and realizes the matching and absorption of transient traveling wave voltage at the end, thereby greatly suppressing or even eliminating the refraction and reflection of transient traveling wave voltage, and further suppressing the problem of multi-point secondary discharge caused by the breakdown of transient traveling waves in the field withstand voltage of the long-distance GIL. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a wiring diagram of the on-site quick docking unit of the present invention as a high-voltage busbar;

[0023] Figure 2 It is a wiring diagram of the on-site quick docking unit of the present invention as a docking flange;

[0024] Figure 3 It is a schematic diagram of the high-voltage busbar structure of a vertical external structure;

[0025] Figure 4 It is a schematic diagram of the docking flange structure of the armored straight plug structure;

[0026] Figure 5 yes Figure 4 Schematic diagram of the middle AA section;

[0027] Figure 6 It is a flow chart of the frequency selection and matching method in the long-distance GIL field withstand voltage test of the present invention;

[0028] Figure 7 is a specific flow chart of step S102;

[0029] Figure 8 This is a specific flowchart of step S104.

[0030] In the figure: 1-power frequency experimental power supply, 2-long distance GIL bushing, 3-long distance GIL pipeline, 4-pot insulator, 5-three-pillar insulator, 6-on-site quick docking unit, 7-capacitor, 8-resistor, 9-resistor-capacitor network. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments 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.

[0032] Embodiment 1, as Figure 1-8 As shown, the present invention discloses a frequency selection and matching device for a long-distance GIL on-site withstand voltage test, comprising an on-site quick docking unit 6 and a resistor and capacitor network 9 whose impedance varies with frequency, which are connected in sequence. The frequency selection and matching device for a long-distance GIL on-site withstand voltage test is connected to an on-site power frequency test power supply 1 and a long-distance GIL bushing 2, and realizes the dual functions of traveling wave frequency selection and matching and test voltage measurement.

[0033] The resistor-capacitor network 9 includes a resistor-capacitor network of multiple resistors 8 and capacitors 7 connected in series, thereby realizing frequency-variable impedance. The larger the capacitance value, the smaller the capacitive reactance at low frequency, but the capacitive reactance at high frequency will also decrease accordingly. In order to present a "high impedance" state under AC voltage, a smaller capacitance value can be selected. To ensure that the capacitive reactance value does not exceed 10% of the GIL corridor wave impedance at the power frequency, and the resistor-capacitor network can effectively match the GIL corridor when a breakdown traveling wave is generated, the selectable capacitance value range is between 10pF and 2000nF.

[0034] The choice of resistance value needs to take into account the reactance of the capacitor and the required impedance value. Under AC voltage, the resistor and capacitor will jointly determine the impedance of the RC network. By adjusting the resistance value, the impedance of the RC network under AC voltage can be further controlled. Considering the practicality and economy on site, the selectable resistance value range is between 50Ω and 100Ω. (Under the power frequency voltage, the frequency is very low, the impedance of the capacitor is large, the RC network is generally in a "high resistance" state, and the end sleeve is still approximately open-circuited. The existence of the RC network does not affect the power frequency withstand voltage test. If the GIL breaks down, the equivalent frequency of the breakdown traveling wave is very high. The total impedance of the RC network is mainly determined by the resistor, and the total impedance of the RC network is basically matched with the GIL wave impedance, which can achieve the effect of eliminating reflected waves.) The results we hope for are: the frequency-variable impedance is approximately infinite under the power frequency voltage. At this time, the current and power of the frequency selection and matching device are very small, and the impact on the power supply and capacity of the power frequency test is very small; the frequency-variable impedance is very small when the GIL breaks down, which is basically equal to the wave impedance of the GIL (the GIL wave impedance of the embodiment used in this project is 100Ω), thereby achieving RC matching of the traveling wave at the end of the GIL, and greatly or even completely eliminating the refraction and reflection of the traveling wave.

[0035] The frequency-dependent impedance estimation method of the resistor network and capacitor network in the frequency-selective matching device is as follows:

[0036] The frequency-dependent equivalent impedance of the capacitor network is estimated by the following formula:

[0037]

[0038] In the formula, Z C is the frequency-dependent equivalent impedance of the capacitor network, in Ω; ω is the angular frequency, in rad / s; c is the capacitance, in farad; π is pi, approximately equal to 3.14; f is the frequency, in Hz.

[0039] The resistor network will inevitably contain a certain amount of stray inductance due to its structural inductance. Its frequency-dependent equivalent impedance is estimated by the following formula:

[0040] Z R =r+ωL=r+2πL

[0041] In the formula, Z R is the frequency-dependent equivalent impedance of the resistor network, in Ω; r is the resistance value, in Ω; ω is the angular frequency, in rad / s; L is the equivalent stray inductance, in H; π is pi, approximately equal to 3.14.

[0042] For example, when conducting a withstand voltage test on a 550kV GIL, it is estimated that its equivalent wave impedance is 90Ω. The selected resistance and capacitance parameters are: 75Ω+10pF, and the resistance network is Figure 5The low inductance radial structure shown, the equivalent stray inductance of GIL is estimated to be 0.1uH. Its impedance at power frequency is: 3.19×10 8 Ω, at this time, the current is 2.40×10 -3 A, the power is 1.77kW, which satisfies the large frequency-variable impedance under the power frequency voltage, and the current and power of the frequency-selective matching device are small. At the equivalent frequency of the traveling wave (according to statistics, the rise time of the breakdown traveling wave in the GIL is on the order of 3ns, at this time, the equivalent frequency is estimated to be 300MHz), at this time, the theoretical impedance is 90Ω. It is achieved that the frequency-variable impedance is basically equal to the equivalent wave impedance of the GIL at the equivalent frequency of the breakdown wave.

[0043] Embodiment 2, based on embodiment 1, the on-site quick docking unit 6 includes two typical structures: a vertical external connection structure and an armored direct plug-in structure, respectively as follows Figure 1 and Figure 2 shown.

[0044] Among them, the vertical external connection structure is suitable for GIL with bushing outlet. It is connected through a high-voltage busbar. The high-voltage busbar has excellent conductivity and mechanical strength. Connecting the GIL bushing through the high-voltage busbar can ensure the stability and reliability of the current during transmission. However, the vertical external connection structure connected through the high-voltage busbar will be affected by the resistance and inductance effects of the busbar itself.

[0045] Among them, the detailed structure of the vertical external structure is as follows Figure 3 shown.

[0046] Among them, the armored plug-in structure is suitable for GIL with reserved docking flange. The plug-in structure can achieve quick docking and flange sealing. Compared with the reactance generated by the high-voltage busbar, the reactance generated by the armored plug-in structure with reserved docking flange direct plug connection has less impact on the circuit system.

[0047] Among them, the detailed structure of the armored direct plug structure is as follows Figure 4 and Figure 5 shown.

[0048] Embodiment 3, based on Embodiment 2, the present invention further discloses a frequency selection and matching method for a long-distance GIL field withstand voltage test, comprising:

[0049] Step S102, obtaining parameters of the GIL and calculating its impedance characteristics;

[0050] Step S104, obtaining parameters of instruments required for the test and calculating impedance characteristics of the generating circuit and the measuring circuit;

[0051] Step S106, designing a matching network according to the impedance characteristics of the GIL;

[0052] Step S108, impedance matching is achieved by selecting similar instruments required for the test or adding additional electrical components to the circuit.

[0053] In specific implementation, step S102 includes: obtaining basic parameters of the length, conductor material, conductor cross section and insulation material of the GIL; calculating R, L, C parameters and characteristic parameter Z per unit length; and calculating the GIL impedance characteristic in combination with the frequency influence.

[0054] In specific implementation, step S104 includes: obtaining parameters of instruments required for the test and establishing a circuit model; calculating impedance characteristics according to the model in combination with a frequency domain analysis method; and verifying the calculation results by actual measurement per unit length.

[0055] In specific implementation, the frequency selection and matching method is mainly based on the resonance principle, impedance matching principle and phase balance principle.

[0056] In addition to the above, the present invention can also perform circuit simulation according to the parameters of the GIL and the instrument to verify the matching network.

[0057] The selection of the high-voltage wire of the present invention should not only consider its impedance characteristics, but also its transmission performance, mechanical strength and other factors. In practical applications, it may be necessary to further optimize the matching between the impulse voltage generator and the high-voltage wire. This can be achieved by adjusting the parameters of the device, such as output impedance, transmission frequency, etc.

[0058] After selecting the appropriate impulse voltage generator and high-voltage conductor, the GIL impulse test is carried out. During the test, it is necessary to monitor the voltage, current and other parameters in the GIL pipeline and record the test data. By analyzing the test data, the operating performance of the GIL under extreme conditions such as lightning impulse can be evaluated.

[0059] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0060] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode includes only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A frequency selection and matching device in a long-distance GIL field withstand voltage test, comprising a field quick docking unit and a resistor and capacitor network whose impedance varies with frequency, connected in sequence, characterized in that: The resistor and capacitor network is a resistor and capacitor network composed of multiple resistors and capacitors connected in series. The resistor and capacitor network is connected to the long-distance GIL pipeline through an on-site quick docking unit and a long-distance GIL casing. The long-distance GIL pipeline is connected to the power frequency experimental power supply through the long-distance GIL casing at the other end.

2. The frequency selection and matching device in the long-distance GIL field withstand voltage test according to claim 1, characterized in that: The long-distance GIL pipeline is provided with a plurality of pot-type insulators and three-pillar insulators.

3. The frequency selection and matching device in the long-distance GIL field withstand voltage test according to claim 1, characterized in that: The on-site quick docking unit is a high-voltage busbar, and the high-voltage busbar is a vertical external connection structure.

4. The frequency selection and matching device in the long-distance GIL field withstand voltage test according to claim 1, characterized in that: The on-site quick docking unit is a docking flange, and the docking flange is an armored direct-insertion structure.

5. A frequency selection and matching method in a long-distance GIL field withstand voltage test, characterized in that: The frequency selection and matching device according to any one of claims 1 to 4 comprises the following steps: Step S102, obtaining parameters of the GIL and calculating its impedance characteristics; Step S104, obtaining parameters of instruments required for the test and calculating impedance characteristics of the generating circuit and the measuring circuit; Step S106, designing a matching network according to the impedance characteristics of the GIL; Step S108: impedance matching is achieved by selecting similar instruments required for the test or adding additional electrical components to the circuit.

6. The frequency selection and matching method in a long-distance GIL field withstand voltage test according to claim 5, characterized in that: Step S102 includes: obtaining basic parameters of the length, conductor material, conductor cross section and insulation material of the GIL; calculating R, L, C parameters and characteristic parameter Z per unit length; and calculating the GIL impedance characteristic in combination with the frequency influence.

7. The frequency selection and matching method in a long-distance GIL field withstand voltage test according to claim 5, characterized in that: The step S104 includes: obtaining parameters of instruments required for the test and establishing a circuit model; calculating impedance characteristics according to the model in combination with a frequency domain analysis method; and verifying the calculation results by actual measurement per unit length.

8. The frequency selection and matching method in a long-distance GIL field withstand voltage test according to claim 5, characterized in that: It also includes a verification step, specifically: circuit simulation is performed based on the parameters of the GIL and the instrument to verify the matching network.

9. The frequency selection and matching method in a long-distance GIL field withstand voltage test according to claim 5, characterized in that: It also includes further matching optimization of the impulse voltage generator and the high-voltage wire, which is achieved by adjusting the output impedance and transmission frequency parameters of the equipment.

10. The frequency selection and matching method in a long-distance GIL field withstand voltage test according to claim 5, characterized in that: During the on-site pressure withstand test of long-distance GIL, it is necessary to monitor the voltage and current parameters in the long-distance GIL pipeline and record the test data. By analyzing the test data, the operating performance of GIL under lightning impulse conditions can be evaluated.

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