A test method for switching capacitor contactor electrical life

Abstract

The application relates to a test method for switching capacitor contactor electric life, which comprises connecting a to-be-tested switching capacitor contactor into an experimental circuit, and then carrying out a breaking test, and the method further comprises connecting a rated capacitance load into the experimental circuit in advance, the capacitance value of the rated capacitance load being greater than that of the to-be-tested switching capacitor contactor. Compared with the prior art, the application realizes the test on the inrush current impact resistance performance of the to-be-tested switching capacitor contactor, and scientific and appropriate rated capacitance load capacitance capacity is obtained.

Description

Technical Field

[0001] This invention relates to the field of testing technology for switching capacitor contactors, and in particular to a test method for the electrical life of switching capacitor contactors. Background Technology

[0002] A capacitor-switching contactor is a standard AC contactor with a specially designed pre-installed module. This module connects three series resistors into the circuit, thus limiting the peak current during capacitor charging. This connection limits the occurrence of secondary current peaks and ensures that the contactor's main contacts close before the capacitor charges. Therefore, the electrical life performance of a capacitor-switching contactor is one of the most critical performance indicators. In addition to evaluating the weldability of the main contacts during inrush current, the inrush current resistance of the current-limiting resistors is also assessed.

[0003] The existing test method for capacitor switching contactors is as follows: In the low-voltage switchgear industry, the switching application category of capacitor switching contactors is AC-6b. According to the latest national standard GBT14048.4-2020 and the international standard IEC60947-4-1:2018, the life test for AC-6b only specifies a test current of 1.5Ie, and does not specify requirements for inrush current-related parameters, such as... Figure 1 As shown, the existing test procedure for switching capacitor contactors involves connecting multiple switching capacitor contactors under test and their corresponding contactors KM1, KM2, and KM3 to the test circuit, sequentially performing on-off and off-off operations on each contactor, and determining whether each switching capacitor contactor under test exhibits a fault phenomenon; that is, the test procedure is as follows:

[0004] KM1 is switched on and off; then KM2 is switched on and off; then KM3 is switched on and off; finally, the circuit discharges to ground. The test is repeated 100,000 times.

[0005] The existing solution has the following drawbacks:

[0006] 1. Lack of assessment of influencing factors: Besides the test current and test voltage, the inrush current at the moment of connection is a major factor affecting the switching performance of capacitor-type contactors. Inrush current not only affects the resistance to arcing generated when the main contacts are connected, but also tests the performance of the current-limiting resistor and the contacts themselves. Inrush current refers to the peak current flowing into the switching power supply equipment at the moment of connection.

[0007] 2. Limited compatibility with actual customer applications: In real applications, capacitor switching contactors are used in reactive power compensation cabinets. These cabinets typically contain multiple contactors and corresponding capacitor banks. Their operation involves switching them on and off one by one according to the power factor in the power grid. The later the contactor and capacitor bank are switched on, the larger the inrush current they can handle, and the more severe the switching conditions become.

[0008] The current method only limits the test current to 1.5Ie. For switching capacitor contactors, the most likely failure is the contact sticking caused by the large inrush current when the switch is turned on. The current method cannot test and evaluate the inrush current impact resistance of the switching capacitor contactor under test. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing technologies, such as the inability to test and evaluate the surge current impact performance of the switching capacitor contactor, and to provide a test method for the electrical life of the switching capacitor contactor.

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] A test method for the electrical life of a switching capacitor contactor includes connecting the switching capacitor contactor under test to a test circuit and then performing a disconnection test. The method further includes pre-connecting a rated capacitor load to the test circuit, wherein the capacitance value of the rated capacitor load is greater than the capacitance value of the switching capacitor contactor under test.

[0012] Furthermore, the capacitance value of the rated capacitor load is within the range of 2 to 5 times the capacitance value of the capacitor-type contactor under test.

[0013] Furthermore, the rated capacitive load is connected in parallel with the capacitor-type contactor under test.

[0014] Furthermore, the process for determining the capacitance value of the rated capacitive load includes:

[0015] Circuit construction steps: Construct a test circuit;

[0016] Inrush current peak multiple test procedure: Connect a test capacitor in the test circuit and collect the current. Then connect a reference capacitor in parallel in the test circuit and collect the current to measure the corresponding inrush current peak multiple.

[0017] Repeat the test steps: Select test capacitors with different capacitance values ​​and repeat the inrush current peak multiple test steps until the preset number of cycles is reached;

[0018] Calculate the ratio of the capacitance of the test capacitor connected in the test circuit to the capacitance of the reference capacitor during each repeated test. Based on the corresponding inrush current peak multiple, construct the measured inrush current peak curve by fitting. Determine the capacitance value of the rated capacitive load based on the measured inrush current peak curve.

[0019] Furthermore, a closing phase angle control device, a thyristor, and a data acquisition system are connected in series between the reference capacitor and the test circuit. The closing phase angle control device turns the thyristor on or off, thereby connecting or disconnecting the reference capacitor.

[0020] Furthermore, a contactor is connected in series between the test capacitor and the test circuit, through which the test capacitor is connected or disconnected.

[0021] Furthermore, after connecting a test capacitor to the test circuit, the peak value of the stable current is collected; after connecting a reference capacitor to the test circuit, the peak value of the inrush current is collected, and the inrush current peak value multiple is obtained according to the ratio of the peak value of the inrush current to the peak value of the reference current.

[0022] Furthermore, the rated capacitive load is a capacitor bank.

[0023] Furthermore, the number of the capacitor-type contactors under test connected in the experimental circuit is multiple.

[0024] Furthermore, the experimental circuit is a three-phase circuit.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) Before the capacitor-type contactor under test is connected in the test circuit, the rated capacitor load is pre-loaded in the test circuit. When the capacitor-type contactor under test is connected, the inrush current multiplier generated in the circuit increases, which is more in line with actual application and realizes the test of the inrush current impact resistance performance of the capacitor-type contactor under test.

[0027] (2) The present invention takes into account that if the rated capacitor load is pre-loaded too large in the test line, it may lead to overcompensation of the power grid and damage to the power grid. Therefore, a test line is constructed to determine the relationship curve between the multiple of the parallel capacitor bank and the peak inrush current, thereby obtaining a scientific and appropriate rated capacitor load capacity. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of an existing test circuit for a switching capacitor contactor provided in the background art;

[0029] Figure 2 This is a schematic diagram of a test circuit for determining the capacitance value of a rated capacitive load, provided in an embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram of a measured peak flow curve provided in an embodiment of the present invention;

[0031] Figure 4 This is a circuit diagram illustrating a test method for measuring the electrical life of a switching capacitor contactor, as provided in an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0034] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0035] Example 1

[0036] This embodiment provides a test method for the electrical life of a switching capacitor contactor, including connecting a rated capacitor load to the test circuit beforehand, then connecting the switching capacitor contactor under test to the test circuit, and performing a breaking test; the capacitance value of the rated capacitor load is greater than the capacitance value of the switching capacitor contactor under test.

[0037] The rated capacitive load is connected in parallel with the capacitor-type contactor under test, so that when the capacitor-type contactor under test is connected to the test circuit, the rated capacitive load and the capacitor-type contactor under test together generate a larger inrush current.

[0038] Before connecting the capacitor-type contactor under test in the test circuit, this method pre-loads the rated capacitor load in the test circuit. When the capacitor-type contactor under test is connected, the inrush current generated in the circuit increases, which is more in line with actual application and realizes the test of the inrush current impact resistance performance of the capacitor-type contactor under test.

[0039] Experimental verification shows that the capacitance value of the rated capacitor load is preferably within 2-5 times the capacitance value of the capacitor-type contactor under test, and more preferably within 3-4 times the capacitance value of the capacitor-type contactor under test.

[0040] Reasons and risks of parallel capacitor bank capacity: Theoretically, capacitor banks are used to compensate for excessive reactive power in a line. When compensation reaches a certain threshold, the contactor will disconnect the capacitors from the line to prevent overcompensation. Therefore, during testing, unrestricted addition of parallel capacitor lines could easily lead to overcompensation of the power grid, posing a risk of damage.

[0041] As a preferred embodiment, to determine a scientifically appropriate number of parallel capacitor banks, this embodiment determines the capacitance value of the rated capacitive load through the following process:

[0042] Circuit construction steps: Construct a test circuit;

[0043] Inrush current peak multiple test steps: Connect a test capacitor in the test circuit and collect the current to obtain the stable current peak value; then connect a reference capacitor in parallel in the test circuit and collect the current to obtain the inrush current peak value, thereby obtaining the inrush current peak multiple based on the ratio of the inrush current peak value to the reference current peak value.

[0044] Repeat the test steps: Select test capacitors with different capacitance values ​​and repeat the inrush current peak multiple test steps until the preset number of cycles is reached;

[0045] Calculate the ratio of the capacitance of the test capacitor connected in the test circuit to the capacitance of the reference capacitor during each repeated test. Based on the corresponding inrush current peak multiple, construct the measured inrush current peak curve by fitting. Determine the capacitance value of the rated capacitive load based on the measured inrush current peak curve.

[0046] Preferably, a closing phase angle control device, a thyristor, and a data acquisition system are connected in series between the reference capacitor and the test circuit. The thyristor is turned on or off by the closing phase angle control device, thereby connecting or disconnecting the reference capacitor.

[0047] A contactor is connected in series between the test capacitor and the test circuit, through which the test capacitor is connected or disconnected.

[0048] The configuration of the series-connected phase angle control device, thyristor and data acquisition system, as well as the contactor, is more consistent with the relevant configuration in the actual test process of switching capacitor contactor electrical life, and constructs the same experimental environment as the actual experimental process, so as to obtain more accurate and reliable measured curves of inrush current peak.

[0049] In this embodiment, the process of determining the capacitance value of the rated capacitor load is as follows:

[0050] like Figure 2 As shown, a circuit is constructed using a phase angle closing control device, a thyristor, a capacitor bank, a contactor, and a data acquisition system. The phase angle closing control device is set to 90°. First, contactor KM1 is turned on to connect capacitor Cy1 to the power grid. Then, the thyristor is turned on through the phase angle closing control device to connect capacitor Csp to the power grid. The current value is obtained through the data acquisition system. This allows the output of the inrush current peak multiple (Is / In) when Q1 / Q2 = 1, where Q1 is the capacitance value of capacitor Csp and Q2 is the capacitance value of the pre-connected parallel Cy1 capacitor.

[0051] Then, by repeatedly following the above sequence, this embodiment increases the capacitance value of the rated capacitive load by adding parallel capacitor banks, i.e., connecting Cy1, Cy2, Cy3… in parallel, to achieve Q1 / Q2 = 1 / 2, 1 / 3…, thereby measuring the inrush current peak multiple (Is / In). After repeated verification, the relationship curve between the parallel capacitor bank multiple and the inrush current peak value was determined as follows: Figure 3 As shown in the curve, the more parallel capacitor banks are connected, the larger the peak value of the surge, but at the same time, it gradually tends to saturate. The scheme that tends to saturate and has fewer parallel capacitor banks connected is selected as the preferred rated capacitor load scheme.

[0052] In the specific test process of the above-mentioned test method for the electrical life of switching capacitor contactors, the switching capacitor contactor under test is connected to the three-phase test circuit. Multiple switching capacitor contactors under test can be set up to conduct the test in a common cycle. The rated capacitor load is a capacitor bank suitable for three-phase circuits.

[0053] In this embodiment, a specific implementation process of the above-mentioned test method for the electrical life of the switching capacitor contactor is as follows.

[0054] When switching capacitor contactors for electrical life testing, assuming the capacitance of the test load is C, a parallel capacitor bank is pre-connected in the test circuit before the test sample is switched on, serving as the rated capacitor load to increase its inrush current peak value.

[0055] Test plan as follows Figure 4 As shown, the rated capacitive load Cn is set to a capacitance of 3C, the test load is C1 to C3, and Q1 / Q2 = 1 / 3, Cn = 3C1, C1 = C2 = C3. KM0 is the rated capacitive load control switch, and KM1 to KM3 are the test load control switches. The test sequence is as follows: first, KM0 is turned on, Cn is connected to the circuit, and then KM1 to KM3 are controlled to alternately turn the test loads C1 to C3 on and off.

[0056] Verification Results Comparison: Through practical comparison and verification, as shown in Table 1, the proposed pre-installed capacitor scheme was compared with the existing standard scheme without pre-installed capacitors. The proposed scheme exhibited the pre-set fault phenomenon within the actual target of 100,000 cycles, while the standard scheme did not. This demonstrates that the proposed scheme has high practical application reference value.

[0057] Table 1

[0058]

[0059] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A test method for the electrical life of a switching capacitor contactor, comprising connecting the switching capacitor contactor under test to a test circuit, and then performing a disconnection test, characterized in that, The method further includes pre-connecting a rated capacitor load in the experimental circuit, wherein the capacitance value of the rated capacitor load is greater than the capacitance value of the switching capacitor contactor under test. The process for determining the capacitance value of the rated capacitive load includes: Circuit construction steps: Construct a test circuit; Inrush current peak multiple test procedure: Connect a test capacitor in the test circuit and collect the current. Then connect a reference capacitor in parallel in the test circuit and collect the current to measure the corresponding inrush current peak multiple. Repeat the test steps: Select test capacitors with different capacitance values ​​and repeat the inrush current peak multiple test steps until the preset number of cycles is reached; Calculate the ratio of the capacitance value of the test capacitor connected in the test circuit to the capacitance value of the reference capacitor during each repeated test, and construct the measured inrush current peak value curve by fitting based on the corresponding obtained inrush current peak value multiple, and determine the capacitance value of the rated capacitor load based on the measured inrush current peak value curve. The reference capacitor is connected in series with the test circuit via a closing phase angle control device, a thyristor, and a data acquisition system. The closing phase angle control device turns the thyristor on or off, thereby connecting or disconnecting the reference capacitor. After connecting a test capacitor to the test circuit, the peak value of the stable current is collected; after connecting a reference capacitor to the test circuit, the peak value of the inrush current is collected, and the inrush current peak value multiple is obtained according to the ratio of the peak value of the inrush current to the peak value of the stable current.

2. The test method for the electrical life of a switching capacitor contactor according to claim 1, characterized in that, The capacitance value of the rated capacitor load is within the range of 2 to 5 times the capacitance value of the capacitor-type contactor under test.

3. The test method for the electrical life of a switching capacitor contactor according to claim 1, characterized in that, The rated capacitive load is connected in parallel with the capacitor-type contactor under test.

4. The test method for the electrical life of a switching capacitor contactor according to claim 1, characterized in that, A contactor is connected in series between the test capacitor and the test circuit, through which the test capacitor is connected or disconnected.

5. The test method for the electrical life of a switching capacitor contactor according to claim 1, characterized in that, The rated capacitive load is a capacitor bank.

6. The test method for the electrical life of a switching capacitor contactor according to claim 1, characterized in that, The number of the capacitor-type contactors under test connected in the experimental circuit is multiple.

7. The test method for the electrical life of a switching capacitor contactor according to claim 1, characterized in that, The experimental circuit is a three-phase circuit.

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