Alternating current power grid matching safety test verification system and method

Abstract

The invention discloses an alternating-current power grid matching safety test verification system which comprises a low-voltage alternating-current power distribution structure composed of a static power source, a power distribution board, a power distribution box and a load, and the static power source is a simulation static power source converting direct current into alternating current. The invention further discloses an alternating current power grid matching safety test verification method. The method improves the authenticity of a protection matching test result, and can be widely applied to the technical field of electric power.

Description

Technical Field

[0001] This invention relates to the field of power technology, and in particular to an AC power grid matching safety test verification system and method. Background Technology

[0002] In low-voltage AC power distribution systems, the traditional dry-feed distribution method of "static power source - distribution board - distribution box - user" is commonly used. When a short circuit occurs at a user end, in order to ensure that other users supplied by the same level distribution box do not lose power, the power system design needs to implement selective protection between the branch circuit breakers of the distribution board and the branch circuit breakers of the distribution box. That is, only the branch circuit breaker of the distribution box corresponding to the short-circuited user will operate, while the branch circuit breaker of the upstream distribution board will not operate.

[0003] The traditional test method for verifying the protection matching of upstream and downstream circuit breakers involves cascading the upstream and downstream circuit breakers, with a generator set or mains power supply provided by the test station as the short-circuit source. A short circuit is simulated by short-circuiting the final-stage circuit breaker, thus verifying the protection matching of the upstream and downstream circuit breakers. However, with this traditional method, due to the large energy capacity of generator sets and mains power, the system cannot achieve voltage reduction when simulating a short circuit by short-circuiting the final stage of the circuit breaker. But for systems powered by static power sources, when an external short circuit occurs, the power source changes from a constant voltage source to a constant current source for short-circuit current limiting, resulting in a significant drop in grid voltage. The difference in grid voltage that occurs when using the traditional matching verification method may lead to inconsistencies between the test results and the actual operating conditions of the power grid, mainly for two reasons: (1) If the grid voltage drops during a short circuit, the equipment on the non-fault side will shut down due to the voltage drop while the circuit breaker is clearing the fault. This is especially true for some control equipment equipped with contactors, where the contactor coils will trip due to undervoltage. Therefore, if the equipment under test does not shut down when using the traditional matching test method, it cannot be proven that the equipment is not affected in a grid actually powered by a static power source. (2) For thermal-magnetic circuit breakers in the final distribution box, the operating time for breaking short-circuit current is determined by the energy at the time of operation. When the system voltage decreases, the energy decreases, and the total breaking time of the circuit breaker may increase. Therefore, the matching of upstream and downstream circuit breakers verified by traditional test methods may fail in the actual power grid due to the extended operating time of the final circuit breaker.

[0004] Furthermore, since there are various combinations of power supply, distribution board circuit breaker and distribution box circuit breaker for system-level short-circuit matching verification, traditional test systems require wiring and rewiring after completing a matching test. Completing the verification test of the entire system is time-consuming and cumbersome. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide an AC power grid matching safety test verification system and method. This system provides short-circuit current by simulating the characteristics of a static power source, builds the power grid architecture to be verified according to the system configuration, and presets the short-circuit points to be verified through a centralized short-circuit simulation device. This simplifies the test process, eliminates the influence of the inability of generator sets or mains power to reduce voltage during short circuits, and improves the authenticity of the protection matching test results.

[0006] The present invention provides an AC power grid matching safety test verification system, comprising a low-voltage AC power distribution structure consisting of a static power source, a distribution board, a distribution box, and a load, wherein the static power source is a simulated static power source that converts DC to AC.

[0007] In the above technical solution, the simulated static power supply consists of a DC / DC isolation converter unit, an inverter unit, a filter unit, and a control unit connected in sequence.

[0008] In the above technical solution, the control unit of the simulated static power supply is equipped with a hardware blocking circuit that can block the conducting switching transistor. The control unit of the simulated static power supply is also equipped with current limiting control software that converts the voltage source into a current source and provides short-circuit current according to the set value and set time.

[0009] In the above technical solution, in the system network composed of distribution board, distribution box and load, the branch circuit breaker in the distribution board is an electronic circuit breaker, the branch circuit breaker in the distribution box is a thermal-magnetic circuit breaker, and the load is one or more of the following: motor, electronic, contactor or relay.

[0010] The above technical solution also includes a centralized short-circuit simulation device that can realize the centralized setting of multiple short-circuit points and simulate three-phase short circuits and two-phase short circuits.

[0011] In the above technical solution, the centralized short-circuit simulation device includes a three-phase busbar and multiple first branches connected to the three-phase busbar. Each first branch is equipped with a disconnecting switch for selecting the short-circuit point. The three-phase busbar is equipped with two contactors. One contactor short-circuits three phases of a section of the three-phase busbar to simulate a three-phase phase-to-phase short circuit, and the other contactor short-circuits two phases of another section of the three-phase busbar to simulate a two-phase phase-to-phase short circuit.

[0012] The above technical solution also includes a data acquisition device, which includes a steady-state parameter measurement module, a transient data acquisition module, and a video monitoring module.

[0013] In the above technical solution, the steady-state parameter measurement module consists of multiple Hall sensors and a controller connected to each Hall sensor. Each Hall sensor is installed at the output terminal of the simulated static power supply and in the corresponding second branch of the system network equipped with a branch circuit breaker, for collecting steady-state voltage and current parameters. The transient data acquisition module includes multiple current probes and voltage probes, as well as an oscilloscope connected to each current probe and voltage probe for data processing. Each current probe contains a Rogowski coil. The video monitoring module is equipped with video monitoring equipment to record various parameter information throughout the entire test process.

[0014] In the above technical solution, the data acquisition device also includes a monitoring backend that receives parameter information from the steady-state parameter measurement module, the transient data acquisition module and the video monitoring module respectively. The monitoring backend performs parameter waveform drawing and analysis based on the received parameter information.

[0015] This invention also provides a method for verifying the safety of AC power grid matching, comprising the following steps: S1, based on the characteristics of the static power supply configured in the test grid, setting the short-circuit current limiting value and current limiting time of the simulated static power supply to be consistent with the actual power supply, connecting the simulated static power supply, the distribution board, and the circuit breakers in the distribution box to the load, and configuring the load as a typical load including motors, electronic components, contactors, and relays; S2, connecting the sensors in the data acquisition device to the second branch of the corresponding branch circuit breaker, and sending the voltage and current information of each second branch to the monitoring backend; S3, according to the set short-circuit point, connecting the positive and negative terminals of the output terminals of the branch circuit breaker corresponding to the short-circuit point in parallel to the first branch of the centralized short-circuit simulation device through cables, thus completing the short-circuit point setting, and turning on the video monitoring equipment to start real-time recording; S4, starting the simulated static power supply, closing each branch circuit breaker, and the test verification system entering steady-state operation, viewing the various steady-state parameters of the test verification system at this time through the monitoring backend, and closing the isolation of one of the first branches of the centralized short-circuit simulation device. S5. At this time, simulated short-circuit tests are carried out at the corresponding short-circuit points. The two contactors of the centralized short-circuit simulation device are closed in sequence to conduct three-phase phase-to-phase short-circuit tests and two-phase phase-to-phase short-circuit tests respectively; S6. The transient parameters of each second branch during the short circuit are recorded through the transient data acquisition module. The operation of each branch circuit breaker and the operation of the typical load are observed. The test waveform is recorded. The two contactors and the isolating switch under test are disconnected. The next isolating switch is closed. The above steps are repeated to conduct simulated short-circuit tests at the next short-circuit point; S7. If the lower-level branch circuit breaker trips but the upper-level branch circuit breaker does not operate, the typical load of the non-faulty branch does not stop during the fault clearing process, and the simulated static power supply resumes output after the branch circuit breaker trips, it indicates that the protection parameter settings of the system design are reasonable and the system has selective protection; if both the upper and lower-level branch circuit breakers trip, the typical load of the non-faulty second branch stops during the fault clearing process, or the simulated static power supply also stops after the branch circuit breaker trips, it indicates that the protection parameter settings of the system are unreasonable and the system does not have selective protection.

[0016] The AC power grid matching safety test verification system and method of the present invention have the following beneficial effects: 1) This invention proposes a technical solution for AC power grid matching safety test verification. It can simulate the short-circuit state of static power supply according to test needs and make the expected short-circuit current adjustable to meet the design requirements of different AC low-voltage power systems.

[0017] 2) This invention can fully simulate the voltage and current characteristics of an AC power grid powered by a static power source during a short circuit, eliminating the influence of traditional large power grids or charging generators being unable to reduce voltage, thus ensuring the authenticity of the test results.

[0018] 3) The centralized short-circuit simulation device proposed in this invention can collect multiple short-circuit points at once. During the test, the short-circuit point is selected by the first branch disconnect switch, eliminating the need for frequent line switching and improving test efficiency.

[0019] 4) If the system parameters are found to be unreasonable or lack selective protection through testing, the test parameters can be adjusted to achieve repeated testing, thereby improving the test efficiency. Attached Figure Description

[0020] Figure 1 This is a circuit diagram of the low-voltage AC power distribution structure under test in the AC power grid matching safety test verification system of the present invention. Figure 2 This is a circuit diagram of the centralized short-circuit simulation device in the AC power grid matching safety test verification system of the present invention; Figure 3 This is a circuit diagram of the data acquisition device in the AC power grid matching safety test verification system of the present invention; Figure 4 This is a flowchart illustrating the AC power grid matching safety test verification method of the present invention. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, but these embodiments should not be construed as limiting the present invention.

[0022] The AC power grid matching safety test verification system of the present invention consists of a simulated static power source, a system network, a centralized short-circuit simulation device, and a data acquisition device.

[0023] Example 1 See Figure 1 The simulated static power supply (SPS) receives a DC voltage input and outputs an AC 380V output. It consists of a DC / DC isolation converter, an inverter, a filter, and a control unit. The SPS has a capacity of 160kVA, and the selected power devices can provide a short-circuit current of no more than 1200A in the event of an external short circuit. The operating principle of the SPS is as follows: Under normal operating conditions, the SPS outputs a constant voltage. When an external short circuit occurs, if the SPS detects that the output current exceeds the set short-circuit current, the hardware blocking circuit within the control unit blocks the conducting transistor, forcing the current to decrease and ensuring that the current does not exceed the set value. Simultaneously, software current limiting control is activated, converting the constant voltage output to a constant current output, providing the short-circuit current according to the set value and time. If the external short circuit is interrupted within the set time, the SPS resumes normal operation; if the external short circuit is not interrupted within the set time, the SPS shuts down for protection.

[0024] The system network mainly consists of the tested electronic circuit breakers, thermal-magnetic circuit breakers, and test loads. The circuit breakers are combined and connected according to the tested system architecture. The test loads are selected from various typical loads such as motors, electronic devices, contactors, and relays. This is used to verify the impact of the voltage reduction and current limiting of the simulated static power supply on the operation of non-faulty branch equipment during short-circuit protection. That is, if the circuit breaker protection action time is too long, it may cause other equipment to shut down, thus failing to achieve protection matching.

[0025] To achieve selective protection, branch circuit breakers in the distribution board are usually electronic circuit breakers with time delay, while circuit breakers in the distribution box are usually thermal-magnetic circuit breakers with faster protection action. Based on this, a corresponding AC power grid matching safety test verification system is designed to verify the protection matching between the static power supply and the circuit breakers at each level, ensuring that a short circuit at a certain user end will not cause other users to lose power while they are working normally.

[0026] Example 2 This embodiment is basically the same as Embodiment 1, except that: See Figure 2 The centralized short-circuit simulation device consists of a three-phase busbar and n first branches. Each first branch is equipped with a electrically operated disconnecting switch for selecting the short-circuit point. Two contactors are configured on the three-phase busbar: one contactor short-circuits one section of the three-phase busbar to simulate a three-phase-to-phase short circuit, and the other contactor short-circuits the other section of the three-phase busbar to simulate a two-phase-to-phase short circuit. Both the disconnecting switch and contactors are capable of withstanding a 3kA short-circuit current for 1 second. This device allows for the centralized setting of n short-circuit points and can simulate both three-phase and two-phase short circuits.

[0027] Example 3 This embodiment is basically the same as embodiment 2, except that: See Figure 3The data acquisition device is divided into a steady-state parameter measurement module, a transient data acquisition module, and a video monitoring module. The steady-state parameter measurement module consists of Hall sensors and a controller. The Hall sensors are installed at the output of the analog power supply and in the second branch of each test circuit in the system under test network to collect steady-state voltage and current parameters. The transient data acquisition module includes multiple current and voltage probes, as well as an oscilloscope connected to each probe for data processing. Due to the large short-circuit current exceeding the range of typical Hall sensors, the current probes in the transient data acquisition module use Rogowski coils to achieve high-current measurement, and the oscilloscope is used for data processing. The video monitoring module is equipped with video monitoring equipment to display and store the test site footage in real time. Data from each module is uploaded to the monitoring backend, which can uniformly record various parameter information throughout the entire test process, and can also perform parameter waveform plotting and analysis as needed.

[0028] Example 4 See Figure 4 The present invention provides a method for verifying the safety of AC power grid matching, comprising the following steps: S1. Based on the characteristics of the static power source configured in the test grid, set the short-circuit current limiting value and current limiting time of the simulated power source to be consistent with the actual power source. Arrange the simulated power source, the circuit breaker under test, and the load according to... Figure 1 Connect the circuits shown, and configure the test loads to include various typical loads such as motors, electronic devices, contactors, and relays.

[0029] S2. Connect the sensors in the data acquisition system to the circuits of branch circuit breakers QF1-QF10, and send the voltage and current information of each branch to the monitoring backend.

[0030] S3, according to Figure 1 The short-circuit points F1-F5 in the circuit breaker are connected by parallel cables from the positive and negative terminals of the output terminals of branch circuit breakers QF1, QF2, QF6, QF8, and QF10 to branches 1-5 of the centralized short-circuit simulation device. Figure 2 With the short circuit point now set, the conditions for starting the test are met. Turn on the video surveillance to begin real-time recording.

[0031] S4. Start the simulated static power supply and close the branch circuit breakers QF1-QF10. The test verification system enters steady-state operation. You can view the steady-state parameters of the test system at this time through the monitoring background. Close the isolating switch QS1 of the first branch of the centralized short-circuit simulation device. At this time, the simulated F1 short-circuit test is carried out. Close the contactors KM1 and KM2 of the centralized short-circuit simulation device respectively to conduct three-phase phase-to-phase short-circuit tests and two-phase phase-to-phase short-circuit tests.

[0032] S5. Record the transient parameters of each second branch during the short circuit using the transient data acquisition module, observe the operation of the branch circuit breakers and the working conditions of typical loads, and record the test waveforms. Disconnect contactors KM1 and KM2 and disconnector switch QS1, close disconnector switch QS2, and repeat the above steps to perform a simulated F2 short circuit test.

[0033] S6. If the downstream branch circuit breaker trips but the upstream branch circuit breaker does not, the typical load of the non-faulty branch does not stop during the fault clearing process, and the simulated static power supply resumes output after the branch circuit breaker trips, then the protection parameter settings of the system design are reasonable, and the system has selective protection. If both the upstream and downstream branch circuit breakers trip, and the typical load of the second non-faulty branch stops during the fault clearing process, or the simulated static power supply also stops after the branch circuit breaker trips, then the protection parameter settings of the system are unreasonable, and the system does not have selective protection.

[0034] This invention uses a simulated static power supply to mimic the characteristics of an actual power supply, fully simulating the actual state during use and ensuring the authenticity of the protection matching results. Simultaneously, a centralized short-circuit generator connects all the short-circuit points to be verified, simplifying the testing process.

[0035] By establishing a test system, this invention fully verifies the protection matching between multi-stage circuit breakers in low-voltage power distribution systems powered by static electricity, and can also verify the rationality of power system protection parameter settings. It can be widely applied to the design of low-voltage AC power systems for ships and submarines. Therefore, if the designed protection parameters cannot pass the verification of this test system, the parameter settings need to be optimized to achieve system protection matching.

[0036] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0037] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. An AC power grid matching safety test verification system, comprising a low-voltage AC power distribution structure composed of a static power source - distribution board - distribution box - load, characterized in that: The analog static power supply is a DC-to-AC analog static power supply.

2. The AC grid match safety test verification system of claim 1, wherein: The analog static power supply is composed of a DC / DC isolation conversion unit, an inverter unit, a filter unit and a control unit connected in sequence.

3. The AC grid match safety test verification system of claim 2, wherein: The control unit of the analog static power supply is provided with a hardware blocking circuit capable of blocking the conduction of a switch tube, and is also provided with a current limiting control software capable of converting a voltage source into a current source and providing a short-circuit current according to a set value and a set time.

4. The AC grid match safety test verification system of claim 3, wherein: In a system network composed of a distribution board, a distribution box and a load, the branch circuit breakers in the distribution board are electronic circuit breakers, the branch circuit breakers in the distribution box are thermal magnetic circuit breakers, and the load is one or several of a motor, an electronic device, a contactor and a relay.

5. The AC grid match safety test verification system of claim 4, wherein: The centralized short-circuit simulation device is also provided.

6. The AC grid match safety test verification system of claim 5, wherein: The centralized short-circuit simulation device comprises a three-phase busbar and a plurality of first branch circuits connected to the three-phase busbar, each of the first branch circuits is provided with an isolating switch for selecting a short-circuit point, and the three-phase busbar is provided with two contactors, one of the contactors is used for short-circuiting three phases of a section of the three-phase busbar for simulating a three-phase short-circuit, and the other contactor is used for short-circuiting two phases of another section of the three-phase busbar for simulating a two-phase short-circuit.

7. The AC grid match safety test verification system of claim 6, wherein: The data acquisition device comprises a steady-state parameter measurement module, a transient data acquisition module and a video monitoring module.

8. The AC grid match safety test verification system of claim 7, wherein: The steady-state parameter measurement module is composed of a plurality of Hall sensors and a controller connected to each Hall sensor, each Hall sensor is installed at an output end of the analog static power supply and a corresponding second branch circuit provided with a branch circuit breaker in the system network, and is used for acquiring steady-state voltage and current parameters; the transient data acquisition module comprises a plurality of current probes and voltage probes and an oscilloscope connected to each current probe and voltage probe for data processing, and each current probe is provided with a Rogowski coil; and the video monitoring module is provided with a video monitoring device for recording various parameter information in the entire test process.

9. The AC grid match safety test verification system of claim 8, wherein: The data acquisition device further comprises a monitoring background for receiving parameter information of the steady-state parameter measurement module, the transient data acquisition module and the video monitoring module, and the monitoring background performs parameter waveform drawing and analysis on the basis of the received parameter information.

10. An alternating current grid matching safety test verification method, characterized by: The method comprises the following steps: S1, according to the characteristics of the static power supply configured in the test power grid, setting the short-circuit current limiting value and the current limiting time of the analog static power supply to be consistent with the actual power supply, connecting the branch circuit breakers in the analog static power supply, the distribution board and the distribution box to the load, and configuring the load as typical loads including a motor, an electronic device, a contactor and a relay; S2, connecting the sensors in the data acquisition device to the second branch circuits of the corresponding branch circuit breakers, and sending the voltage and current information of each second branch circuit to the monitoring background; S3, according to the set short-circuit point, connecting the positive and negative poles of the output end of the branch circuit breaker corresponding to the short-circuit point in parallel to the corresponding first branch circuit of the centralized short-circuit simulation device through a cable, and thus the short-circuit point is set, and the video monitoring device is turned on to start real-time recording. S4, start the simulation of static power supply, close each branch circuit breaker, test and verify that the system enters steady state operation, view the steady state parameters of the test and verification system at this time through the monitoring background, close the disconnecting switch of one of the first branches of the centralized short circuit simulation device, at this time carry out the simulation short circuit test of the corresponding short circuit point, sequentially close the two contactors of the centralized short circuit simulation device to carry out three-phase and two-phase short circuit tests respectively; S5, record the transient parameters of each second branch during the short circuit process through the transient data acquisition module, observe the action of each branch circuit breaker and the working condition of the typical load, record the test waveform, open the two contactors and the disconnecting switch under test, close the next disconnecting switch, and repeat the above steps to carry out the simulation short circuit test of the next short circuit point; S6, if the lower branch circuit breaker protection trips and the upper branch circuit breaker does not act, the typical load of the non-fault branch does not stop during the fault removal process, and the simulation static power supply recovers output after the branch circuit breaker protection trips, it indicates that the protection parameter setting of the system design is reasonable, and the system has the selectivity protection; if the upper and lower branch circuit breakers are both protection tripped, the typical load of the non-fault second branch is stopped or the simulation static power supply is also protection stopped after the branch circuit breaker protection trips during the fault removal process, it indicates that the protection parameter setting of the system is not reasonable, and the system does not have the selectivity protection.

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