Multi-path combination switch for low-voltage capacitor switching and working method

Abstract

The invention belongs to the technical field of low-voltage switch control, and discloses a multi-path combination switch for low-voltage capacitor switching and a working method, and the multi-path combination switch comprises a multi-path combination switch control system, thyristors, magnetic latching relays, auxiliary relays and circuit breakers. A phases of the power grid are sequentially communicated to form an A-phase first path and an A-phase second path; the power grid C phases are sequentially communicated to form a C-phase first path and a C-phase second path; the phase B of the power grid is connected with a B-phase circuit output branch protection circuit breaker inlet wire; outgoing lines of the output branch protection circuit breakers of the A-phase circuit, the B-phase circuit and the C-phase circuit are respectively connected with compensation capacitors. A corresponding closing method and a corresponding opening method are adopted. Compared with a traditional combination switch, the combination switch has the advantages that complicated and numerous trigger circuits and thyristor circuits are not needed, the problem that the combination switch is damaged due to overvoltage misconduction such as lightning stroke does not exist, circuit elements are reduced, system control is simplified, and reliability and safety of the combination switch are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-voltage switch control, and in particular relates to a multi-channel composite switch for low-voltage capacitor switching and a working method. Background Art

[0002] Switching parallel capacitors is still the most widely used method for reactive power compensation in power grids. The biggest drawback of this technology is that there are large voltage fluctuations and current shocks at the moment of switching, and frequent switching of switches is impossible. There are two main ways to solve this problem. One is to use phase-splitting synchronous switching technology, and the other is to use multi-way composite switching technology. Whether the synchronous switching technology can achieve the expected effect under various conditions depends on the phase accuracy of the closing and opening gates, but due to the influence of manufacturing process and the dispersion of mechanism movement, its long-term effect is not ideal. The requirements of the multi-way composite switch on the dispersion of mechanism movement are relatively loose, and it can fully utilize the original reactive compensation equipment. The new equipment occupies a small area, has no special requirements for the original system, has low transformation investment, simple wiring, and convenient installation. It can realize frequent switching of the compensation device at the zero point, which is suitable for large-scale promotion and application.

[0003] Currently, commonly used compound switches generally adopt a topological structure of thyristor parallel mechanical switches. Since thyristors are too sensitive to the voltage change rate, they are easily misconnected and damaged under overvoltage conditions such as lightning strikes. At the same time, this structure also requires a complex trigger circuit to ensure the synchronization of thyristor triggering. All these factors reduce the reliability and safety of compound switches to a certain extent, limiting their promotion and use. Summary of the invention

[0004] In view of this, the present invention provides a multi-way composite switch for low-voltage capacitor switching and a working method to solve the above problems.

[0005] In order to solve the above technical problems, the present invention provides a multi-way composite switch for low-voltage capacitor switching, comprising:

[0006] Multi-channel composite switch control system, thyristor, magnetic latching relay, auxiliary relay and output branch protection circuit breaker;

[0007] The thyristor includes a first thyristor and a second thyristor; the magnetic latching relay and the auxiliary relay are used to form a connection path with the branch where the first thyristor is located and the branch where the second thyristor is located;

[0008] Among them, one end of the first thyristor is electrically connected to the A phase of the power grid, and the other end is connected to one end of the A phase circuit auxiliary relay; the other end of the A phase circuit auxiliary relay is connected to the A phase incoming line of the A phase circuit output branch protection circuit breaker; and one end of the A phase circuit magnetic latching relay is electrically connected to the A phase of the power grid, and the other end is connected to the A phase incoming line of the A phase circuit output branch protection circuit breaker;

[0009] One end of the second thyristor is electrically connected to the C phase of the power grid, and the other end is connected to one end of the C phase circuit auxiliary relay; the other end of the C phase circuit auxiliary relay is connected to the C phase incoming line of the C phase circuit output branch protection circuit breaker; and one end of the C phase circuit magnetic latching relay is electrically connected to the C phase of the power grid, and the other end is connected to the C phase incoming line of the C phase circuit output branch protection circuit breaker;

[0010] The B phase of the power grid is connected to the input line of the output branch protection circuit breaker of the B phase circuit; and the output branch protection circuit breakers of the A phase circuit, the B phase circuit and the C phase circuit are respectively connected to compensation capacitors.

[0011] As an optional manner, multiple auxiliary relays for the A-phase and C-phase circuits, multiple output branch protection circuit breakers for the A-phase and C-phase circuits, and multiple magnetic latching relays for the A-phase and C-phase circuits are respectively provided.

[0012] As an optional method, a multi-way composite switch control system is used to connect any thyristor, magnetic holding relay and auxiliary relay; the multi-way composite switch control system includes a voltage sampling circuit, a current transformer, a temperature sampling interface circuit, a signal conditioning circuit, a digital control system, a thyristor drive circuit, a magnetic holding relay drive circuit, an auxiliary relay drive circuit, a system power supply circuit, a composite switch status display circuit and a digital control system.

[0013] On the other hand, the present invention also provides a multi-way composite switch working method for low-voltage capacitor switching, which is used in the closing stage and the opening stage of the A-phase circuit and / or the C-phase circuit, and the closing stage includes the following steps:

[0014] After the closing command is issued, the voltage, current and temperature of the current circuit are collected; it is determined whether there is an operating fault in the circuit. If so, an early warning is issued; otherwise, the closing command is executed;

[0015] Close the auxiliary relay to preselect the capacitor to be connected for the thyristor, and detect the voltage at both ends of the circuit after a delay of t1; if the current circuit voltage difference is 0, close the thyristor;

[0016] After a delay of t2, the voltage at both ends of the circuit is detected again. If the waveforms are consistent, the magnetic latching relay is closed. After a delay of t3, the thyristor and the auxiliary relay are disconnected in turn.

[0017] The opening phase includes the following steps:

[0018] After the opening command is issued, the voltage, current and temperature of the current circuit are collected; it is determined whether there is an operating fault in the circuit. If so, an early warning is issued; otherwise, the opening command is executed;

[0019] Close the auxiliary relay to preselect the capacitor to be connected for the thyristor, and close the thyristor after a delay of t4;

[0020] After delay t5, disconnect the magnetic latching relay; wait for delay t6 to turn off the thyristor; wait for delay t7 to disconnect the auxiliary relay.

[0021] As an optional method, voltage, current and temperature acquisition of the current circuit includes:

[0022] The voltage sampling circuit, current transformer, temperature sampling interface circuit and signal conditioning circuit are driven by a digital control system to detect the voltage at both ends of the A phase or C phase circuit.

[0023] As an optional method, the capacitor is a low-voltage reactive power compensation capacitor, and is connected in a delta connection method.

[0024] As an optional manner, two ends of the circuit include an A-phase and / or C-phase circuit power supply port and a low-voltage reactive power compensation capacitor port.

[0025] As an optional manner, the A-phase circuit and / or the C-phase circuit are respectively connected to multiple capacitors.

[0026] The beneficial effects of the present invention are:

[0027] The present invention can realize zero-voltage switching and zero-current switching of the composite switch through certain timing control, eliminate the closing surge current and opening overvoltage in the switching process, and realize arc-free operation of the mechanical switch, thereby improving the electrical life of the mechanical switch contacts; the thyristor is replaced by an auxiliary relay connected in series with a thyristor, and compared with the traditional composite switch, it does not require complex and numerous trigger circuits and thyristor circuits, and does not have the problem of damage caused by mis-conduction due to overvoltage such as lightning strikes, reduces circuit elements, simplifies system control, and improves the reliability and safety of the composite switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of a circuit structure provided by an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of the functional modules of a multi-channel composite switch control system provided by an embodiment of the present invention;

[0030] Figure 3 A phase A circuit closing control flow chart of a multi-channel composite switch control system provided by an embodiment of the present invention;

[0031] Figure 4 This is a flow chart of the A-phase circuit opening control of the multi-channel composite switch control system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with specific implementation methods.

[0033] See also Figure 1 and Figure 2 This embodiment provides a multi-way composite switch for low-voltage capacitor switching, including: a multi-way composite switch control system, a thyristor, a magnetic latching relay, an auxiliary relay and an output branch protection circuit breaker; the thyristor includes a first thyristor and a second thyristor; the magnetic latching relay and the auxiliary relay are used to form a connection path with the branch where the first thyristor is located and the branch where the second thyristor is located; wherein the A phase of the power grid is connected to the first thyristor, the A phase circuit auxiliary relay, and the A phase circuit output branch protection circuit breaker in sequence to form the A phase first path. That is, the first thyristor is the A phase thyristor.

[0034] The A phase of the power grid sequentially connects the A phase magnetic latching relay and the A phase circuit output branch protection circuit breaker to form the A phase second path; the C phase of the power grid sequentially connects the first thyristor, the C phase circuit auxiliary relay, and the C phase circuit output branch protection circuit breaker to form the C phase first path; the C phase of the power grid sequentially connects the C phase magnetic latching relay and the C phase circuit output branch protection circuit breaker to form the C phase second path. That is, the second thyristor is the C phase thyristor.

[0035] The B phase of the power grid is connected to the input line of the output branch protection circuit breaker of the B phase circuit; and the output branch protection circuit breakers of the A phase circuit, the B phase circuit and the C phase circuit are respectively connected to compensation capacitors.

[0036] Please refer again Figure 1 , in this embodiment, a 6-way circuit is used for illustration. Figure 1In the figure, A, B, and C are three-phase busbars of the power grid system, ① is an auxiliary relay, ② is a magnetic latching relay, ③ is a thyristor, ④ is a low-voltage reactive compensation capacitor, and ⑤ is a miniature circuit breaker. The low-voltage reactive compensation capacitor of this embodiment is connected in a triangle connection. When the A and C branches are disconnected, the B phase cannot form a closed loop with other phases, and the B phase is equivalent to not being connected to the system. Therefore, the B phase branch can be streamlined, and the thyristor, auxiliary relay, and magnetic latching relay are removed, leaving only a miniature circuit breaker for isolation, thereby saving equipment investment; the A and C branches can pre-select the branches that need to be switched through the auxiliary relay, so that the thyristor is switched to the branch that needs to be switched in advance, so that the 1 to 6 thyristors and drive circuits can be streamlined, and only one thyristor group and drive circuit are retained for each phase, thereby saving equipment investment.

[0037] Specifically, the magnetic latching relay includes the magnetic latching relays of each branch corresponding to phase A and phase C; the auxiliary relay includes the auxiliary relays of each branch corresponding to phase A and phase C; one end of the thyristor group of phase A is electrically connected to phase A of the power grid, and the other end is connected to one end of the auxiliary relays of phase A 1 to 6; the other ends of the auxiliary relays of phase A 1 to 6 are respectively connected to the phase A incoming lines of the 1 to 6 output branch protection circuit breakers; one end of the magnetic latching relays of phase A 1 to 6 are electrically connected to phase A of the power grid, and the other ends are respectively connected to the phase A incoming lines of the 1 to 6 output branch protection circuit breakers; phase C One end of the thyristor is electrically connected to the C phase of the power grid, and the other end is connected to one end of the C phase 1 to 6 auxiliary relays; the other ends of the C phase 1 to 6 auxiliary relays are respectively connected to the C phase incoming wires of the 1 to 6 output branch protection circuit breakers; one end of the C phase 1 to 6 magnetic latching relays is electrically connected to the C phase of the power grid, and the other end is respectively connected to the C phase incoming wires of the 1 to 6 output branch protection circuit breakers; the B phase of the power grid is electrically connected to the B phase incoming wires of the 1 to 6 output branch protection circuit breakers; the A, B, and C outgoing wires of the 1 to 6 output branch protection circuit breakers are respectively connected to the A, B, and C wiring terminals of the compensation capacitors. Therefore, this embodiment Figure 1 The circuits include the A-phase thyristor Q1, auxiliary relays Ka1-Ka6, magnetic latching relays Ka11-Ka16, the C-phase thyristor Q2, auxiliary relays Kc1-Kc6, magnetic latching relays Kc11-Kc16, circuit breakers QF1-QF6 and capacitors C1-C6. Among them, a1-a6 and c1-c6 represent the connection terminals of the low-voltage reactive power compensation capacitor and the A-phase circuit and the C-phase circuit, respectively.

[0038] Based on the above scheme, the working principle of this embodiment is to use the voltage crossing zero point to trigger the thyristor to turn on, and when the current is zero, the thyristor is automatically disconnected without generating inrush current.

[0039] The specific working process of zero voltage switching is as follows: first, close the auxiliary relay Ka1 to pre-select the thyristor Q1 to the first capacitor C1, and when it is detected that the voltage difference between A and a1 is zero, trigger the thyristor Q1 to turn on; after the thyristor Q1 is stably turned on, close the magnetic latching relay Ka11 to achieve zero voltage and no inrush current; after the magnetic latching relay Ka11 is stably turned on, trigger the disconnection of the thyristor Q1 and the auxiliary relay Ka1 in turn, so as to achieve low power consumption conduction.

[0040] The shut-off process is similar to the on-process, except that the on-process is triggered by the timing of conduction when the voltage difference between A and a1 is zero, while the shut-off process is triggered by the timing of automatic shut-off when the current A passes through zero. The specific working process of zero-current shutdown is as follows: First, close the auxiliary relay Ka1 to pre-select the thyristor Q1 to the first capacitor C1. After the auxiliary relay Ka1 is stably turned on, the thyristor Q1 is triggered to turn on; when the thyristor Q1 is stably turned on, the magnetic latching relay Ka11 is disconnected and Q1 is triggered to disconnect, then the current will gradually transfer from the magnetic latching relay Ka11 to the thyristor Q1 and the auxiliary relay Ka1; when the main circuit current is zero, Q1 is automatically disconnected at this time; after Q1 is stably disconnected, Ka1 is disconnected; since the main circuit current is zero, no arc will be generated during the disconnection process of Ka1, and zero-current shutdown will be achieved in the end.

[0041] For further information, please refer again to Figure 2 The multi-channel composite switch control system of this embodiment includes a voltage sampling circuit, a current transformer, a temperature sampling interface circuit, a signal conditioning circuit, a digital control system, two thyristor drive circuits, 12 magnetic latching relay drive circuits, 12 auxiliary relay drive circuits, a system power supply circuit, a switch state display circuit and a digital control system; the voltage sampling circuit and the signal conditioning circuit are used to detect the voltage zero point and frequency, and transmit them to the digital control system; the input of the signal conditioning circuit is respectively connected to the voltage sampling circuit, the current transformer, and the temperature sampling interface circuit; the output of the signal conditioning circuit is connected to the input of the digital control system; the output of the digital control system is respectively connected to two thyristor drive circuits, 12 magnetic latching relay drive circuits, 12 auxiliary relay drive circuits, and a composite switch state display circuit; the current transformer and the signal conditioning circuit are used for current detection, and transmit them to the digital control system; the temperature sampling interface circuit and the signal conditioning circuit are used to detect the temperature of the capacitor, and transmit them to the digital control system. The composite switch status display circuit is mainly used to monitor the working status of the multi-channel composite switch and provide corresponding fault alarm and fault information; in order to ensure the electrical safety of the capacitor compensation branch, the output branch protection circuit breaker QF (miniature circuit breaker) is introduced to ensure that when this equipment fails, the capacitor can be separated from the power grid.

[0042] exist Figure 2In the figure, V is the voltage sampling circuit, I is the current transformer, E is the temperature sampling interface circuit, N is the signal conditioning circuit, P is the digital control system, D1 is the 2 thyristor drive circuits, D2 is the 12 auxiliary relay drive circuits, D3 is the 12 magnetic latching relay drive circuits, SCR is the thyristor, S is the auxiliary relay, R is the magnetic latching relay, and F is the composite switch state display circuit. The voltage sampling circuit V and the signal conditioning circuit N are mainly used for voltage detection, providing a control basis for the zero voltage opening and current zero-crossing closing of the multi-way composite switch; the current transformer I and the signal conditioning circuit N are mainly used for current detection, providing a control basis for the thyristor fault and overcurrent protection of the multi-way composite switch; the multi-way composite switch state display circuit F is mainly used to monitor the working state of the multi-way composite switch and provide corresponding fault alarms and fault information; since the capacitor will heat up after long-term operation, the temperature detection interface E is the input interface of the capacitor temperature sensor, which provides a basis for over-temperature protection after passing through the signal conditioning circuit N.

[0043] See also Figure 3 and Figure 4 This embodiment also provides a multi-way composite switch operating method for low-voltage capacitor switching, which is used in the closing stage and the opening stage of the A-phase circuit and / or the C-phase circuit.

[0044] The working method of the closing stage is as follows: after receiving the closing command, the digital control system P detects the grid side voltage, various currents, and temperature through the voltage sampling circuit V, current transformer I, temperature sampling interface E, and signal conditioning circuit N to determine whether to enter the closing procedure or the fault alarm procedure; after entering the closing procedure, the digital control system P first closes Ka1 to pre-select Q1 to the first capacitor C1, delay time t1, after Ka1 is stably turned on, the voltage of A and a1 is detected through the voltage sampling circuit V and the signal conditioning circuit N, and when the voltage is detected to pass through the zero point, it immediately triggers to turn on (close the thyristor) Q1; delay time t2, the voltage of A and a1 is detected through the voltage sampling circuit V and the signal conditioning circuit N, when it is detected that Q1 is stably turned on, Ka11 is closed; delay time t3, after Ka11 is stably turned on, Q1 and Ka1 are disconnected in sequence. Figure 3 shown.

[0045] The working method of the opening stage is as follows: after receiving the opening command, the digital control system P detects the grid side voltage, various currents, and temperature through the voltage sampling circuit V, current transformer I, temperature sampling interface E and signal conditioning circuit N to determine whether to enter the closing procedure or the fault alarm procedure; after entering the closing procedure, the digital control system P first closes Ka1 to pre-select Q1 to the first capacitor C1; after the delay time t4, after Ka1 is stably turned on, trigger the turn-on (close the thyristor) Q1; after the delay time t5, after Q1 is stably turned on, disconnect Ka11; after the delay time t6, trigger the turn-off of Q1; when the current passes through zero, Q1 automatically passes through zero and turns off; after the delay time t7, the voltages of A and a1 are detected through the voltage sampling circuit V and the signal conditioning circuit N, and after Q1 is stably turned off, turn off Ka1. Its control principle is as follows Figure 4 shown.

[0046] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A multi-way composite switch for low-voltage capacitor switching, characterized in that: include: Multi-channel composite switch control system, thyristor, magnetic latching relay, auxiliary relay and output branch protection circuit breaker; The thyristor includes a first thyristor and a second thyristor; the magnetic latching relay and the auxiliary relay are used to form a connection path with the branch where the first thyristor is located and the branch where the second thyristor is located; Wherein, one end of the first thyristor is electrically connected to the A phase of the power grid, and the other end is connected to one end of the A phase circuit auxiliary relay; the other end of the A phase circuit auxiliary relay is connected to the A phase incoming line of the A phase circuit output branch protection circuit breaker; and one end of the A phase circuit magnetic latching relay is electrically connected to the A phase of the power grid, and the other end is connected to the A phase incoming line of the A phase circuit output branch protection circuit breaker; One end of the second thyristor is electrically connected to the C phase of the power grid, and the other end is connected to one end of the C phase circuit auxiliary relay; the other end of the C phase circuit auxiliary relay is connected to the C phase incoming line of the C phase circuit output branch protection circuit breaker; and one end of the C phase circuit magnetic latching relay is electrically connected to the C phase of the power grid, and the other end is connected to the C phase incoming line of the C phase circuit output branch protection circuit breaker; The B phase of the power grid is connected to the input line of the output branch protection circuit breaker of the B phase circuit; and the output branch protection circuit breakers of the A phase circuit, the B phase circuit and the C phase circuit are respectively connected to compensation capacitors.

2. A multi-way composite switch for low-voltage capacitor switching according to claim 1, characterized in that: The A-phase and C-phase circuit auxiliary relays, the A-phase and C-phase circuit output branch protection circuit breakers, and the A-phase and C-phase circuit magnetic latching relays are respectively provided in plurality.

3. A multi-way composite switch for low-voltage capacitor switching according to claim 2, characterized in that: The multi-way composite switch control system is used to connect any of the thyristors, magnetic latching relays and auxiliary relays; the multi-way composite switch control system includes a voltage sampling circuit, a current transformer, a temperature sampling interface circuit, a signal conditioning circuit, a digital control system, a thyristor drive circuit, a magnetic latching relay drive circuit, an auxiliary relay drive circuit, a system power supply circuit, a composite switch status display circuit and a digital control system.

4. A multi-way composite switch operating method for low-voltage capacitor switching, used in the closing and opening stages of the A-phase circuit and / or the C-phase circuit, characterized in that: The closing phase includes the following steps: After the closing command is issued, the voltage, current and temperature of the current circuit are collected; it is determined whether there is an operating fault in the circuit. If so, an early warning is issued; otherwise, the closing command is executed; Close the auxiliary relay to preselect the capacitor to be connected for the thyristor, and detect the voltage at both ends of the circuit after a delay of t1; if the current circuit voltage difference is 0, close the thyristor; After a delay of t2, the voltage at both ends of the circuit is detected again. If the waveforms are consistent, the magnetic latching relay is closed. After a delay of t3, the thyristor and the auxiliary relay are disconnected in turn. The opening stage comprises the following steps: After the opening command is issued, the voltage, current and temperature of the current circuit are collected; it is determined whether there is an operating fault in the circuit. If so, an early warning is issued; otherwise, the opening command is executed; Close the auxiliary relay to preselect the capacitor to be connected for the thyristor, and close the thyristor after a delay of t4; After delay t5, disconnect the magnetic latching relay; Wait for delay t6 to turn off the thyristor; wait for delay t7 to disconnect the auxiliary relay.

5. A multi-way composite switch operating method for low-voltage capacitor switching according to claim 4, characterized in that: The voltage, current and temperature acquisition of the current circuit includes: The voltage sampling circuit, current transformer, temperature sampling interface circuit and signal conditioning circuit are driven by a digital control system to detect the voltage at both ends of the A phase or C phase circuit.

6. A multi-way composite switch operating method for low-voltage capacitor switching according to claim 4, characterized in that: The capacitor is a low-voltage reactive power compensation capacitor, and is connected using a triangle connection method.

7. A multi-way composite switch operating method for low-voltage capacitor switching according to claim 4, characterized in that: The two ends of the circuit include an A-phase and / or C-phase circuit power supply port and a low-voltage reactive power compensation capacitor port.

8. A multi-way composite switch operating method for low-voltage capacitor switching according to claim 7, characterized in that: The A-phase circuit and / or the C-phase circuit are respectively connected to multiple capacitors.

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