A parameter design method of 500kV large-span metal oxide surge arrester

Abstract

The present application relates to a kind of 500kV large span metal oxide arrester parameter design method, comprising: setting the rated voltage of arrester body, power frequency reference voltage and direct current 2mA reference voltage;Select the arrester 50% lightning impulse discharge voltage;Select the arrester power frequency voltage resistance value and operating impulse withstand voltage;Build large span transmission line model, calculate nominal discharge current.The present application can greatly improve the lightning protection performance of 500kV line Yangtze River large span tower, improve the safety and stability of 500kV transmission line large span section;The nominal discharge current of the arrester of the present application is 30kA, can withstand short time huge lightning current impact, large current arrester can safely discharge larger power frequency follow-up, and quickly cut off, avoid self overheat damage, large current capacity can reduce the "protection failure" caused by arrester itself due to overcurrent damage, avoid the cascading reaction of power grid caused by arrester failure, ensure the continuous operation of power system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrical engineering, and in particular to a 500kV large-span metal oxide arrester parameter design method. BACKGROUND

[0002] Running experience shows that lightning is the main cause of line tripping and power failure accidents, and lightning accidents account for more than 50% of power system accidents. With the increase of tower height, the probability of being struck by lightning also increases. The 500kV large-span line tower is more than 300 meters high, which is a typical tower vulnerable to lightning. Due to the high importance of large-span towers, once lightning accidents cause damage to conductors or insulators, it will greatly affect the power supply reliability and safe and stable operation of the power grid.

[0003] The power system generally uses lightning protection lines, arresters or discharge gaps for lightning protection. Among them, the arrester is the most reliable lightning protection measure, which can effectively protect against direct lightning, induced lightning and shielding lightning. Arresters mainly include gapless arresters and gap arresters. Among them, gapless arresters are mainly used to protect transformers, disconnecting switches and other equipment; gap arresters are mainly used to protect line insulators and are suitable for use on 500kV large-span section towers.

[0004] At present, there is no design method for large-span transmission line arresters in national standards and industry standards. For large-span transmission lines of different voltage levels, due to differences in geographical environment, tower height, overvoltage and insulation coordination, whether it is AC-DC hybrid or other factors, when selecting large-span transmission line arresters, specific working conditions also need to be analyzed and calculated. For large-span transmission lines of different voltage levels, when carrying out lightning protection design, not only the accurate calculation of the lightning protection performance of large-span tower transmission lines needs to be considered, but also the safe service life requirement of large-span transmission lines needs to be considered. High-reliability arresters are configured for different large-span transmission lines, so as to ensure the power supply reliability of large-span transmission lines. However, the existing arrester design method does not consider the difference between large-span transmission lines and ordinary transmission lines. SUMMARY

[0005] In order to solve the problem that there is currently no design for large-span transmission line arresters, the purpose of the present application is to provide a 500kV large-span metal oxide arrester parameter design method which can guide the design of 500kV large-span metal oxide arresters and improve the operation reliability of 500kV large-span sections.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solution: a 500kV large-span metal oxide arrester parameter design method, characterized in that the method comprises the following sequential steps:

[0007] The method comprises the following steps in sequence:

[0008] (1) setting the rated voltage, power frequency reference voltage and DC 2mA reference voltage of the arrester body;

[0009] (2) selecting the 50% lightning impulse discharge voltage of the arrester;

[0010] (3) selecting the power frequency voltage withstand value and the operating impulse withstand voltage of the arrester;

[0011] (4) constructing a large-span transmission line model according to the rated voltage, power frequency reference voltage, DC 2mA reference voltage, 50% lightning impulse discharge voltage of the arrester, power frequency voltage withstand value and operating impulse withstand voltage of the arrester, and calculating the nominal discharge current.

[0012] Step (1) is specifically referring to: setting the rated voltage of the 500kV line arrester body as 396kV, the power frequency reference voltage as greater than or equal to 396kV, and the DC 2mA reference voltage as greater than or equal to 561kV.

[0013] Step (2) is specifically referring to: selecting the 50% lightning impulse discharge voltage of the arrester as 2800kV.

[0014] Step (3) is specifically referring to: selecting the power frequency voltage withstand value of the arrester as 600kV, and the operating impulse withstand voltage as greater than or equal to 980kV.

[0015] Step (4) specifically comprises the following steps in sequence:

[0016] (4a) calculating the maximum shielding lightning current :

[0017] The calculation formula of the striking distance of lightning current to the conductor or ground wire is:

[0018] ;

[0019] Wherein, k is the coefficient, k=1.25; I is the amplitude of lightning current;

[0020] The calculation formula of the striking distance of lightning current to the ground is:

[0021] ;

[0022] Wherein, h is the height of the tower to the ground;

[0023] When the striking distance circle of the conductor is completely shielded by the striking distance circle of the ground wire and the ground striking distance, the lightning current at this time is the maximum shielding lightning current ​​When the striking circle of the conductor is completely shielded, i.e. the striking circles of the conductor, ground wire and the ground intersect at the same point, the geometric constraints are:

[0024] (1);

[0025] wherein, is the angle between the coplanar direction of the conductor and ground wire and the radial direction of the conductor, which varies with the lightning current; is the horizontal distance between the conductor and the ground wire; is the protection angle; is the height of the conductor to the ground; is the striking distance of the lightning current to the ground wire;

[0026] The maximum shielding failure current is obtained by solving formula (1) 61.945 kA;

[0027] (4b) Constructing a large-span transmission line model: the large-span transmission line model includes three parts of a large-span tower model, a transmission line model and a lightning arrester model, the large-span tower model is built by using the hara lossless multi-surge impedance model; the transmission line is built by using the LCC model; the lightning arrester is modeled by using the nonlinear resistance according to the provided voltage-current characteristic curve of the resistance sheet, i.e. the voltage-current characteristic curve of the resistance sheet is input into the parameter table of the nonlinear resistance for modeling;

[0028] (4c) Simulation calculation: in order to determine the nominal discharge current of the lightning arrester, the current flowing through the lightning arrester under shielding failure is obtained by simulation calculation; in order to consider the extreme case, the maximum shielding failure lightning current 61.945 kA is applied to the central conductor of the span of the large-span transmission line model to simulate the lightning shielding failure under the extreme case; probes are placed at both ends of the lightning arrester model to measure the current flowing through both ends of the lightning arrester model under the maximum shielding failure lightning current 61.945 kA, i.e. the maximum current flowing through both ends of the lightning arrester under shielding failure is 33.549 kA, and the nominal discharge current of the lightning arrester is set to 30 kA.

[0029] As can be seen from the above technical solution, the beneficial effects of the present invention are as follows: First, the present invention can significantly improve the lightning protection performance of the 500kV transmission line's long-span tower across the Yangtze River, and improve the safety and stability of the long-span section of the 500kV transmission line; at the same time, the present invention can be applied to long-span lines of different voltage levels, has a broader prospect for promotion and application, and better contributes to the safe and reliable operation of the power grid system; Second, the surge arrester of the present invention has a nominal discharge current of 30kA, which can withstand the impact of a large lightning current in a short time. The high-current surge arrester can safely discharge a larger power frequency follow current and quickly cut it off to avoid overheating damage. The high current capacity can reduce the "protection failure" caused by the surge arrester itself due to overcurrent damage, avoid the chain reaction of the power grid caused by the surge arrester failure, and ensure the continuous operation of the power system. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the electrical geometry model;

[0031] Figure 2 Maximum lightning strike current A calculation diagram. Detailed Implementation

[0032] A parameter design method for a 500kV long-span metal oxide surge arrester, comprising the following sequential steps:

[0033] The method includes the following steps in sequence:

[0034] (1) Set the rated voltage, power frequency reference voltage and DC 2mA reference voltage of the surge arrester body;

[0035] (2) Select a surge arrester with 50% of the lightning impulse discharge voltage;

[0036] (3) Select the power frequency voltage withstand value and switching impulse withstand voltage of the surge arrester;

[0037] (4) Based on the rated voltage of the surge arrester body, the power frequency reference voltage, the DC 2mA reference voltage, the 50% lightning impulse discharge voltage of the surge arrester, the power frequency voltage withstand value of the surge arrester and the switching impulse withstand voltage, construct a long-span transmission line model and calculate the nominal discharge current.

[0038] Step (1) specifically refers to setting the rated voltage of the 500kV line surge arrester body to 396kV, the power frequency reference voltage to be greater than or equal to 396kV, and the DC 2mA reference voltage to be greater than or equal to 561kV.

[0039] Step (2) specifically refers to selecting a surge arrester with a 50% lightning impulse discharge voltage of 2800kV.

[0040] Step (3) is specifically referring to: selecting the lightning arrester power frequency voltage withstand value as 600 kV, and the operating impulse withstand voltage as greater than or equal to 980 kV.

[0041] Step (4) specifically includes the following sequential steps:

[0042] (4a) calculating the maximum shielding lightning current :

[0043] The calculation formula of the striking distance of lightning current to the ground wire is:

[0044] ;

[0045] Wherein, k is a coefficient, k = 1.25; I is the amplitude of lightning current;

[0046] The calculation formula of the striking distance of lightning current to the ground wire is:

[0047] ;

[0048] Wherein, h is the height of the tower to the ground;

[0049] When the striking distance circle of the ground wire is completely shielded by the striking distance circle of the ground wire and the ground striking distance, the lightning current at this time is the maximum shielding lightning current ; When the striking distance circle of the ground wire is completely shielded, that is, the striking distance circle of the ground wire and the ground striking distance intersect at the same point, the geometric constraint is:

[0050] (1);

[0051] Wherein, is the angle between the co-linear direction of the ground wire and the ground wire and the radius direction of the ground wire, which changes with the lightning current; is the horizontal distance between the ground wire and the ground wire; is the protection angle; is the height of the ground wire to the ground; is the striking distance of lightning current to the ground wire;

[0052] The maximum shielding lightning current 61.945 kA is obtained by solving formula (1).

[0053] ​​(4b) Constructing a long-span transmission line model: The long-span transmission line model includes three parts: a long-span tower model, a transmission line model, and a surge arrester model. The long-span tower model is constructed using the HARHA lossless multi-surge impedance model; the transmission line model is LCC model; the surge arrester is modeled using a nonlinear resistor based on the provided volt-ampere characteristic curve of the resistor element, that is, the volt-ampere characteristic curve of the resistor element is input into the parameter table of the nonlinear resistor for modeling.

[0054] (4c) Simulation calculation: To determine the nominal discharge current of the surge arrester, the current flowing through the surge arrester under the condition of lightning strike is obtained through simulation calculation; to consider extreme cases, the maximum lightning strike current with a waveform of 2.6 / 50μs and an amplitude of 61.945kA is used. A conductor is applied to the center span of a long-span transmission line model to simulate lightning strikes under extreme conditions; probes are placed at both ends of the surge arrester model to measure the surge arrester model at the maximum lightning strike current. The current flowing through the lower two ends is 33.549kA, which means that under the condition of a lightning strike, the maximum current that may flow through the two ends of the surge arrester is 33.549kA. The nominal discharge current of the surge arrester is set to 30kA.

[0055] like Figure 1 As shown, to calculate the nominal discharge current of a surge arrester on a long-span tower, it is necessary to determine the exposed arc around the center of the span of the long-span tower using an electrical geometry model (EMG). In the EMG, the striking distance is related to the leader potential, and thus to the lightning current. Figure 2 As shown, arcs are drawn with the overhead ground wire and conductor as centers and the striking distance as the radius, and horizontal lines are drawn with the ground striking distance as the height. The intersections of these arcs and horizontal lines form three continuous curve segments: B1A1, A1A2, and A2B2. Since the A1A2 curve segment represents the conductor's striking distance arc, meaning the lightning leader will preferentially strike the conductor within this range (i.e., a backlash), this curve is also considered an exposed arc. A perpendicular line is drawn from the intersection point to the ground, describing the exposed width of the curve segment, which is segment D2D3. Furthermore, B1 and B2 are the intersection points of the ground horizontal striking distance and the overhead ground wire striking distance arc, corresponding to the left of D1 and the right of D2, representing induced overvoltage areas. When the overhead ground wire's striking distance arc covers the conductor's striking distance arc, A2 and A1 coincide. Due to the shielding effect of the overhead ground wire, the lightning leader will not backlash the conductor. The lightning current amplitude corresponding to this striking distance is the maximum backlash lightning current on the conductor.

[0056] The EGM model is used to calculate the maximum striking distance when the exposed arc is 0, and then the maximum lightning current is inferred. The calculation parameters required are: conductor suspension point height, conductor sag, conductor insulator length, horizontal distance between conductors and ground wires, number of thunderstorm days, rated voltage of the transmission line, distance of the conductor from the center of the tower, and arc-building rate. The parameter values ​​are shown in Table 1 below.

[0057] Table 1 calculates parameter value

[0058]

[0059] According to the calculation result, it is concluded that the maximum shielding lightning current in the central span is 61.95488kA.

[0060] In summary, the application can greatly improve the lightning protection performance of the 500kV line Yangtze River large-span tower, improve the safety and stability of the 500kV transmission line large-span section; at the same time, the application can be applied to large-span lines of different voltage levels, has a broader application prospect, and better helps the safe and reliable operation of the power grid system; the arrester of the application has a nominal discharge current of 30kA, can withstand a huge lightning current impact for a short time, the large-current arrester can safely discharge a larger power frequency follow-up current and quickly cut it off, avoids self-overheating damage, the large-current capacity can reduce the "protection failure" caused by the self-overheating damage of the arrester, avoids the power grid chain reaction caused by the arrester failure, and protects the continuous operation of the power system.

[0061] The above shows and describes the basic principles, main features and advantages of the application. Those skilled in the art should understand that the application is not limited by the above examples, and the above examples and descriptions in the specification are only the principles of the application. Without departing from the spirit and scope of the application, various changes and improvements can be made to the application, and these changes and improvements all fall within the scope of the claimed application. The scope of protection claimed by the application is defined by the appended claims and their equivalents.

Claims

1. A method for designing parameters of a 500 kV large-span metal oxide surge arrester, characterized in that: The method comprises the following steps in sequence: (1) setting the rated voltage, power frequency reference voltage and DC 2mA reference voltage of the arrester body; (2) selecting the 50% lightning impulse discharge voltage of the arrester; (3) selecting the power frequency voltage withstand value and operating impulse withstand voltage of the arrester; (4) constructing a large-span transmission line model according to the rated voltage, power frequency reference voltage, DC 2mA reference voltage, 50% lightning impulse discharge voltage of the arrester, power frequency voltage withstand value and operating impulse withstand voltage of the arrester, and calculating the nominal discharge current; Step (4) specifically comprises the following steps in sequence: (4a) Calculate the maximum lightning current around the strike : The striking distance of lightning current to the conductor or ground wire The calculation formula is: ； Wherein, k is a coefficient, k = 1.25; I is the amplitude of lightning current; The striking distance of lightning current to the ground The calculation formula is: ； Wherein, h is the height of the tower to the ground; When the striking circle of the conductor is completely shielded by the striking circle of the ground wire and the striking circle of the ground, the lightning current at this time is the maximum shielding failure current When the striking circle of the conductor is completely shielded, that is, the conductor, the striking circle of the ground wire and the striking circle of the ground intersect at the same point, the geometric constraint is: （1）； wherein, is the angle between the co-linear direction of the conductor and ground wire and the radial direction of the conductor as the lightning current varies; is the horizontal distance between the conductor and ground wire; is the protection angle; is the height of the conductor above the ground; is the striking distance of the lightning current to the ground wire; The maximum lightning current of the shielding failure is obtained by solving formula (1) 61.945 kA; (4b) constructing a large-span transmission line model: the large-span transmission line model comprises three parts of a large-span tower model, a transmission line model and an arrester model, the large-span tower model is built by using a hara lossless multi-surge impedance model; the transmission line is built by using an LCC model; the arrester is modeled by using a nonlinear resistor according to the provided voltage-current characteristic curve of the resistor disc, that is, the voltage-current characteristic curve of the resistor disc is input into the parameter table of the nonlinear resistor for modeling; (4c) Simulation calculation: In order to determine the nominal discharge current of the surge arrester, the current flowing through the surge arrester under the situation of lightning shielding is obtained by simulation calculation; in order to consider the extreme situation, the maximum lightning current of 2.6 / 50 μs waveform and 61.945 kA amplitude is used The lightning shielding situation under the extreme condition is simulated by applying the lightning current to the central conductor of the span of the long-span transmission line model; the probes are placed at both ends of the surge arrester model to measure the maximum lightning current of the surge arrester model under the maximum lightning current of 2.6 / 50 μs waveform and 61.945 kA amplitude The current flowing through the lower end is 33.549 kA, that is, the maximum current flowing through the surge arrester under the situation of lightning shielding is 33.549 kA, and the nominal discharge current of the surge arrester is set to 30 kA.

2. The method for parameter design of 500 kV large-span metal oxide surge arrester according to claim 1, characterized in that: Step (1) specifically refers to: setting the rated voltage of the 500kV line arrester body to 396kV, the power frequency reference voltage to be greater than or equal to 396kV, and the DC 2mA reference voltage to be greater than or equal to 561kV.

3. The method for parameter design of 500 kV large-span metal oxide surge arrester according to claim 1, characterized in that: Step (2) specifically refers to: selecting the 50% lightning impulse discharge voltage of the arrester to be 2800kV.

4. The method for parameter design of 500 kV large-span metal oxide surge arrester according to claim 1, characterized in that: Step (3) specifically refers to: selecting the power frequency voltage withstand value of the arrester to be 600kV, and the operating impulse withstand voltage to be greater than or equal to 980kV.

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