Test method for air-insulated disconnectors subjected to equivalent simulated high altitude conditions under dry conditions

Abstract

The present invention discloses a test method for equivalently simulating high altitude of an air-insulated isolating switch under dry conditions, comprising the following steps: 1) changing the temperature, air pressure, voltage and load capacitance in an artificial climate chamber respectively, and conducting a breaking test of the air-insulated isolating switch for breaking a capacitive low-current circuit; 2) measuring the distance between the isolating switch contacts at the moment of arc extinguishing under various atmospheric conditions; 3) constructing a fitting formula for the change of the distance between the isolating switch contacts at the moment of arc extinguishing as a function of temperature, air pressure, voltage and load capacitance; 4) calculating a correction factor formula for voltage with respect to temperature, air pressure and load capacitance; 5) determining an equation for voltage U and an equation for load capacitance C based on the correction factor formula; and 6) obtaining the voltage and load capacitance when equivalently simulating high altitude conditions under conventional altitude. This method can equivalently simulate high altitude and has the characteristics of being time-consuming and low-cost.

Description

Technical Field

[0001] The invention relates to a test method for an air-insulated isolating switch, and in particular to a test method for an air-insulated isolating switch under dry conditions that equivalently simulates high altitude. Background Art

[0002] Air-insulated disconnect switches, as switchgear designed to provide an isolation break in the open position according to specified requirements, offer reliable insulation, isolating the circuit breaker requiring maintenance from the power source. A clear disconnect point ensures the safety of personnel and equipment during circuit breaker maintenance. They do not interrupt short-circuit or load currents. However, because air-insulated disconnect switches are often connected to transformers, lightning arresters, unloaded lines, unloaded transformers, bushings, and circuit breaker shunt capacitors, they also require a certain level of capacitive low-current interrupting capability.

[0003] GB / T 1985-2014, "High-Voltage AC Disconnectors and Earthing Switches," specifies a test circuit for air-insulated disconnectors breaking low capacitive currents, but does not include altitude correction for the test voltage. In actual production, increasing altitude can lead to adverse conditions such as decreased atmospheric pressure and air density, which can reduce the breakdown voltage of the air gap. This can ultimately cause the disconnector to fail to interrupt the arc, potentially causing equipment damage or worker safety hazards. Therefore, research on the ability of air-insulated disconnectors to break low capacitive currents at high altitudes is of great significance.

[0004] At present, there is a large demand for tests on air-insulated isolating switches for breaking small capacitive currents, and the market prospects are good.

[0005] Defects and shortcomings of existing technology:

[0006] Typically, personnel work in an artificial climate chamber, adjusting temperature, air pressure, and other conditions to simulate high-altitude conditions. However, adjusting the temperature and air pressure in the artificial climate chamber typically takes 20 to 30 minutes or even longer. To maintain these atmospheric conditions, the chamber's regulating devices operate continuously throughout the experiment. This consumes significant time, manpower, and energy costs, impacting the effectiveness of the experiment. Summary of the Invention

[0007] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a test method for air-insulated disconnectors to simulate high altitude under dry conditions. The method can simulate high altitude and has the characteristics of being time-consuming and low-cost.

[0008] To achieve the above object, the test method of air-insulated disconnector under dry conditions equivalent to simulated high altitude comprises the following steps:

[0009] 1) In an artificial climate chamber, change the temperature, air pressure, voltage and load capacitance respectively, and conduct an interruption test of the air-insulated isolating switch on and off a capacitive low current circuit;

[0010] 2) Measure the distance between the disconnector contacts at the moment of arc extinguishing under various atmospheric conditions;

[0011] 3) Construct a fitting formula for the change in the distance between the disconnector contacts at the moment of arc extinguishing as a function of temperature, air pressure, voltage, and load capacitance;

[0012] 4) Using the fitting formula, calculate the correction factor formula of voltage with respect to temperature, air pressure and load capacitance;

[0013] 5) determining an equation regarding voltage U and an equation regarding load capacitance C based on the correction factor formula;

[0014] 6) Calculating the equation for voltage U and the equation for load capacitance C to obtain the voltage and load capacitance when equivalently simulating high-altitude conditions at a conventional altitude, and conducting an equivalent simulation of high altitude tests for air-insulated disconnectors under dry conditions based on the voltage and load capacitance when equivalently simulating high-altitude conditions at a conventional altitude.

[0015] Before step 1), the method also includes: building an air-insulated isolating switch to disconnect the capacitive low current circuit.

[0016] The specific process of building an air-insulated isolating switch to interrupt a capacitive low current circuit is as follows:

[0017] According to the provisions of GB / T 1985-2014 "High-voltage AC disconnectors and earthing switches", an air-insulated disconnector is constructed to interrupt a capacitive low-current circuit. The parameters of the air-insulated disconnector for interrupting a capacitive low-current circuit are set according to actual operating conditions.

[0018] The specific operations of step 1) are:

[0019] By using the controlled variable method, the temperature, air pressure, voltage and load capacitance were changed in an artificial climate chamber, and the breaking test of the air-insulated isolating switch on the capacitive low current circuit was carried out.

[0020] The specific operations of step 2) are:

[0021] By collecting arc videos, the distance between the disconnector contacts at the moment the opening arc is extinguished under various atmospheric conditions is measured.

[0022] The fitting formula in step 3) is: L = kf(T)f(P)f(U)f(C).

[0023] The specific operations of step 4) are:

[0024] Assume that the distance between the disconnector contacts at the moment of arc extinction at normal altitude and high altitude is equal, and use the fitting formula obtained in step 3) to calculate the voltage correction factor formula U=K for temperature, air pressure and load capacitance. t U0, where K t =K T K P K C .

[0025] The specific operations of step 5) are:

[0026] Based on the correction factor formula, a correction factor formula for equivalently simulating high-altitude conditions at conventional altitudes is calculated. This is then combined with a formula to maintain the rated current flowing through the two arms of the disconnector when closed, resulting in equations for voltage U and load capacitance C.

[0027] The present invention has the following beneficial effects:

[0028] The test method for equivalently simulating high altitude conditions for air-insulated disconnectors under dry conditions described in the present invention, during specific operation, constructs a fitting formula for how the distance between the disconnector contacts at the moment the opening arc is extinguished varies with temperature, air pressure, voltage, and load capacitance, and uses this formula to calculate the voltage and load capacitance when equivalently simulating high altitude conditions at conventional altitudes. Finally, the test is conducted based on this formula. In actual operation, only the voltage and load capacitance need to be changed to achieve equivalent simulation of high altitude conditions. The test of air-insulated disconnectors breaking small capacitive currents under high altitude conditions saves time, manpower, and energy costs, bringing substantial economic benefits to the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of a three-phase horizontal air-insulated disconnector;

[0030] Figure 2 Circuit diagram for the test;

[0031] Figure 3 It is a sampling diagram of the maximum projection length of the opening arc in the vertical direction and the contact distance at the moment when the opening arc is extinguished;

[0032] Figure 4 It is a graph showing the contact distance at the moment when the opening arc is extinguished and the maximum vertical projection length of the opening arc as a function of temperature, air pressure, voltage and load capacitance;

[0033] Figure 5 This is the fitting curve of the contact distance changing with temperature at the moment of opening and extinguishing the switch;

[0034] Figure 6It is a fitting curve diagram of the contact distance changing with air pressure at the moment of opening and extinguishing the switch;

[0035] Figure 7 It is the fitting curve of the contact distance changing with voltage at the moment of opening and extinguishing the switch;

[0036] Figure 8 It is a fitting curve diagram of the contact distance changing with the load capacitance at the moment of opening and extinguishing the switch;

[0037] Figure 9 This is a diagram showing the idea of ​​solving the air pressure correction factor as an example;

[0038] Figure 10 is the fitting curve of temperature;

[0039] Figure 11 is the fitting curve of air pressure;

[0040] Figure 12 This is the fitted curve of the load capacitance correction factor. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the solutions of the present invention, 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 described embodiments are only embodiments of a part of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0042] The accompanying drawings illustrate schematic diagrams of the structures of the disclosed embodiments of the present invention. These figures are not drawn to scale; for the purpose of clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0043] The test method for an air-insulated disconnector under dry conditions to simulate high altitude conditions comprises the following steps:

[0044] 1) According to the provisions of GB / T 1985-2014 "High-voltage AC disconnectors and earthing switches", build an air-insulated disconnector to interrupt the capacitive low-current circuit, and set the parameters of the air-insulated disconnector to interrupt the capacitive low-current circuit according to the actual working conditions;

[0045] 2) Using the principle of the controlled variable method, the temperature, air pressure, voltage and load capacitance were changed in an artificial climate chamber to conduct an interruption test of the air-insulated isolating switch on a capacitive low current circuit;

[0046] 3) By collecting arc video, the distance between the disconnector contacts at the moment when the opening arc is extinguished under various atmospheric conditions is measured;

[0047] 4) Solve the fitting formula for the change of the distance between the disconnector contacts at the moment of arc extinguishing as a function of temperature, air pressure, voltage, and load capacitance, i.e., L = kf(T)f(P)f(U)f(C);

[0048] 5) Assume that the distance between the disconnector contacts at the moment of arc extinction at normal altitude and high altitude is equal, and use the fitting formula obtained in step 4) to calculate the voltage correction factor with respect to temperature, air pressure and load capacitance: U = K t U0, where K t =K T K P K C ;

[0049] 6) Based on the correction factor formula obtained in step 5), calculate the correction factor formula for equivalent simulation of high altitude conditions at normal altitude. Combined with the formula for maintaining the rated current flowing through the two arms of the disconnector when closed, the equations for U and C are obtained respectively;

[0050] 7) Solve the equations for U and C to obtain the voltage and load capacitance at a normal altitude that are equivalent to simulating high altitude conditions.

[0051] Example 1

[0052] This embodiment is as follows Figure 1 Taking the three-phase horizontal air-insulated disconnector shown in the figure as an example, the specific process is as follows:

[0053] 1) The rated voltage of the three-phase horizontal air-insulated disconnector is 126 kV, and a voltage of 72.7 kV can be applied during single-phase testing;

[0054] 2) Figure 2 The circuit shown is used for disconnection test of isolating switch. R is 3kΩ protective resistor, the equivalent value of C1 is 0.7965nF, the effective value of C2 is 0.04285μF, and T0 is the isolating switch under test.

[0055] 3) Using the principle of controlled variable method, change the temperature, pressure, voltage and load capacitance respectively, conduct ten breaking tests and collect arc video;

[0056] 4) If Figure 3 The data shown in the figure respectively collects the maximum vertical projection length of the opening arc and the contact distance at the moment the opening arc is extinguished, L1 and L2. Among them, L1 is the data required to be collected in GB / T 1985-2014, which is convenient for determining the insulation distance of the three-phase switch. For horizontal disconnectors, L2 is the maximum horizontal projection length of the arc, that is, the distance between the contacts at the moment the opening arc is extinguished. L2 is fitted in the subsequent test sequence.

[0057] 5) Figure 4 a was carried out under the conditions of 97.0 kPa, 72.7 kV, and 42 nF; Figure 4 b was carried out at 25°C, 72.7 kV, and 42 nF; Figure 4 c was carried out under the conditions of 5°C, 74.5 kPa, and 42 nF; Figure 4 d was carried out under the conditions of 96.0 kPa, 20 °C, and 72.7 kV, and the average value of ten tests was also taken;

[0058] 6) Figure 5 、 Figure 6 、 Figure 7 and Figure 8 These are the fitting curves of the contact distance at the moment of arc extinguishing as a function of temperature, air pressure, voltage and load capacitance. The fitting formulas are shown in equations (1), (2), (3) and (4) respectively:

[0059] L2=0.212T+46.33 (1)

[0060] L2=-0.0006383P 3 +0.1639P 2 -14.41P+485.2 (2)

[0061] L2=0.009114U 2 +0.1619U-0.3983 (3)

[0062] L2=-0.01761C 2 +1.954C+0.7779 (4)

[0063] Assume the fitting formula L2 = kf(T)f(P)f(U)f(C), and get k = 6.955×10-6. The formula for L2 is:

[0064] L2=0.0000069550×(0.212T+46.33)(-0.0006383P 3 +0.1639P 2 -14.41P+485.2)

[0065] (0.009114U2 +0.1619U-0.3983)(-0.01761C 2 +1.954C+0.7779)(5)

[0066] 7) Verify the accuracy of L2 in formula (5). As shown in Tables 1, 2, 3 and 4, it can be seen that the error of the fitting formula is small, basically within 10%;

[0067] Table 1

[0068]

[0069]

[0070] Table 2

[0071]

[0072] Table 3

[0073]

[0074] Table 4

[0075]

[0076] 8) Figure 9 This is a diagram showing the solution of the pressure correction coefficient. Figure 9 The K T About T and K P About P and K C Regarding the fitting curve and formula of C, Figure 10 、 Figure 11 and Figure 12 are the fitting curves of temperature, air pressure and load capacitance correction factors, respectively, and their expressions are shown in equations (6), (7) and (8):

[0077] K T =0.002321T+0.9534 (6)

[0078] K P =0.000117P 2 -0.02519P+2.392 (7)

[0079] K C =0.2551×ln(C+1)+0.004174 (8)

[0080] 9) Obtain the correction formula for the equivalent simulated high altitude test under standard atmospheric conditions;

[0081] U=K t U0 (9)

[0082] K t =K T K P K C (10)

[0083] 10) In the laboratory, it is usually necessary to ensure that the rated current flowing through the air-insulated isolating switch remains unchanged when it is turned on. To achieve this goal, the following measures are taken:

[0084] First, the test conditions at location 1 are recorded as T0, P0, and C0, and the applied voltage is unknown; the test conditions at location 2 (conditions at a certain high altitude) are recorded as T, P, C0, and the applied voltage is U0, and the conditions are all known; the test conditions at location 3 (conditions in the laboratory) are recorded as T0 and P0, but the load capacitance is C, and the applied voltage is U, where the magnitudes of U and C are to be determined. When it is necessary to simulate location 2 by changing the voltage at location 1, the voltage U applied at location 1 is 12 =K T K P U0; If you need to simulate location 3 by changing the voltage at location 1, then the voltage U applied at location 1 13 =K C U; if U 12 =U 13 , that is, K T K P U0=K C U, that is, the purpose of equivalent simulation of location 2 is achieved at location 3, and the values ​​of U and C at location 3 show a certain functional relationship, which is given by Figure 2 It can be seen that the rated current flowing through the isolating switch is I=10 -6 ωCU (unit A), combined with this formula, we can get the parameter selection of U and C in the test room when simulating different altitude conditions under the condition of constant I. In this case, I=10 -6 ωC0U0=I0 remains unchanged, and U=10 6 Substituting I0 / ωC, we get K C 10 6 I0 / ωC=K T K P *U0, solve to get C, then pass U=10 6 I0 / ωC, solve for C.

[0085] 11) According to the analysis in step 10), under standard atmospheric conditions, when the rated current flowing through the disconnector at closing time is constant at I0≈0.96A, if we want to equivalently simulate the situation at a certain high altitude, the values ​​of U and C during the disconnector test should be determined by formula (11):

[0086]

[0087] Among them, K T , K P and K C The expressions of are shown in formula (6), formula (7) and formula (8) respectively. It should be noted that K T and K P are the temperature and pressure correction factors calculated based on the temperature and pressure in the test room; K C is the load capacitance correction factor calculated based on the load capacitance at high altitude working locations. The accuracy of formula (11) is verified, and the results are shown in Tables 5, 6, and 7.

[0088] Table 5

[0089]

[0090] Table 6

[0091]

[0092]

[0093] Table 7

[0094]

[0095] 12) Considering the randomness of the arc discharge process, it can be seen from Tables 5, 6, and 7 that the overall error is small, and it is possible to achieve the goal of keeping the rated current flowing through the two arms of the disconnector unchanged when closing the circuit breaker, while also achieving the purpose of equivalently simulating high-altitude conditions.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A test method for air-insulated disconnectors under dry conditions to simulate high altitude, characterized in that: The following steps are involved: 1) In an artificial climate chamber, change the temperature, air pressure, voltage and load capacitance respectively, and conduct a breaking test of the air-insulated isolating switch on a capacitive low current circuit; 2) Measure the distance between the disconnector contacts at the moment of arc extinction under various atmospheric conditions; 3) Construct a fitting formula for the change in the distance between the disconnector contacts at the moment of arc extinguishing as a function of temperature, air pressure, voltage, and load capacitance; 4) Using the fitting formula, calculate the correction factor formula of voltage with respect to temperature, air pressure and load capacitance; 5) Determine the voltage based on the correction factor formula U The equation for load capacitance C equation; 6) Calculate the voltage U The equation for load capacitance C The equation is used to obtain the voltage and load capacitance when the high-altitude conditions are equivalently simulated at normal altitude. Based on the voltage and load capacitance when the high-altitude conditions are equivalently simulated at normal altitude, the test of equivalent simulation of high altitude of air-insulated disconnector under dry conditions is carried out.

2. The test method for air-insulated disconnectors under dry conditions under claim 1, characterized in that: Before step 1), it also includes: building an air-insulated isolating switch to interrupt the capacitive low current circuit.

3. The test method for air-insulated disconnectors under dry conditions under claim 2, characterized in that: The specific process of building an air-insulated isolating switch to interrupt a capacitive low current circuit is as follows: According to the provisions of GB / T 1985-2014 "High-voltage AC disconnectors and earthing switches", an air-insulated disconnector is constructed to interrupt a capacitive low-current circuit. The parameters of the air-insulated disconnector for interrupting a capacitive low-current circuit are set according to actual operating conditions.

4. The test method for air-insulated disconnectors under dry conditions under claim 1, characterized in that: The specific operations of step 1) are: By using the controlled variable method, the temperature, air pressure, voltage and load capacitance were changed in an artificial climate chamber, and the breaking test of the air-insulated isolating switch on the capacitive low current circuit was carried out.

5. The test method for air-insulated disconnectors under dry conditions under claim 1, characterized in that: The specific operations of step 2) are: By collecting arc videos, the distance between the disconnector contacts at the moment the opening arc is extinguished under various atmospheric conditions is measured.

6. The test method for air-insulated disconnectors under dry conditions under claim 1, characterized in that: The fitting formula in step 3) is: L = kf ( T ) f ( P ) f ( U ) f ( C ).

7. The test method for air-insulated disconnectors under dry conditions under claim 1, characterized in that: The specific operations of step 4) are: Assume that the distance between the disconnector contacts at the moment of arc extinction at normal altitude and high altitude is equal, and use the fitting formula obtained in step 3) to calculate the voltage correction factor formula for temperature, air pressure and load capacitance. U = K t U 0, where K t = K T K P K C .

8. The test method for air-insulated disconnectors under dry conditions at equivalent simulated high altitude according to claim 1, characterized in that: The specific operations of step 5) are: Based on the correction factor formula, the correction factor formula for equivalent simulation of high altitude conditions at normal altitude is calculated, and then the formula for keeping the rated current flowing through the two arms of the disconnector unchanged when closed is combined to obtain the voltage U The equation for load capacitance C equation.

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