Multi-path composite switch for low-voltage capacitor switching
By employing a thyristor-connected auxiliary relay and a magnetic latching relay in the low-voltage capacitor switching device, and utilizing zero-point voltage and current triggering, the problems of voltage oscillation and current surge are solved, thereby improving the reliability and safety of the device and reducing the modification cost.
Patent Information
- Application Number
- CN202423170635.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-20
- Publication Date
- 2025-12-09
- Estimated Expiration
- 2034-12-20
AI Technical Summary
Existing low-voltage capacitor switching devices experience voltage oscillations and current surges during switching, and thyristors are susceptible to overvoltage damage such as lightning strikes, resulting in insufficient reliability and safety of composite switches.
The system employs a thyristor series auxiliary relay structure, utilizing the voltage zero-crossing point to trigger conduction and the current zero-crossing point to automatically disconnect. By combining a magnetic latching relay and an auxiliary relay, the triggering circuit is simplified, and reliability and safety are improved.
It achieves zero-voltage turn-on and zero-current turn-off, reduces circuit components, improves the reliability and safety of the composite switch, and reduces equipment modification costs.
Smart Images
Figure CN223651967U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of low-voltage switch control technology, specifically, it relates to a multi-channel composite switch for low-voltage capacitor switching. Background Technology
[0002] Switching parallel capacitors remains the most widely used method for reactive power compensation in power grids. The biggest drawback of this technology is the significant voltage and current surges during switching, making frequent switching impossible. There are two main solutions: phase-synchronous switching technology and multi-channel composite switching technology. The success of synchronous switching technology under various conditions hinges on the accuracy of the closing and opening phases; however, its long-term performance is not ideal due to manufacturing processes and the dispersion of mechanical movement. Multi-channel composite switching, on the other hand, has less stringent requirements regarding the dispersion of mechanical movement. It can utilize existing reactive power compensation equipment, requires minimal additional space, has no special requirements for the existing system, involves low retrofitting costs, and is simple to wire and install. It enables frequent switching at zero-crossing points of the compensation device, making it suitable for widespread application.
[0003] Currently, commonly used composite switches generally adopt a topology of thyristors connected in parallel with mechanical switches. Because thyristors are too sensitive to voltage change rate, they are easily damaged by false triggering under overvoltage conditions such as lightning strikes. At the same time, this structure requires a complex triggering circuit to ensure the synchronicity of thyristor triggering. All these factors reduce the reliability and safety of composite switches to some extent, limiting their widespread use. Utility Model Content
[0004] In view of this, the present invention provides a multi-channel composite switch for low-voltage capacitor switching to solve the above problems.
[0005] To solve the above technical problems, this utility model provides a multi-channel composite switch for low-voltage capacitor switching, comprising:
[0006] Multi-channel composite switch control system, thyristors, magnetic latching relays, auxiliary relays and output branch protection circuit breakers;
[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] Specifically, phase A of the power grid is sequentially connected to the first thyristor, the auxiliary relay of phase A circuit, and the output branch protection circuit breaker of phase A circuit to form the first path of phase A; phase A of the power grid is sequentially connected to the magnetic latching relay of phase A circuit and the output branch protection circuit breaker of phase A circuit to form the second path of phase A.
[0009] The first path of the C phase is formed by sequentially connecting the first thyristor, the auxiliary relay of the C phase circuit, and the protection circuit breaker of the output branch of the C phase circuit; the second path of the C phase is formed by sequentially connecting the C phase magnetic latching relay and the protection circuit breaker of the output branch of the C phase circuit.
[0010] The B phase of the power grid is connected to the incoming line of the output branch protection circuit breaker of the B phase circuit; and the outgoing lines of the output branch protection circuit breakers of the A phase circuit, B phase circuit, and C phase circuit are respectively connected to compensation capacitors.
[0011] As an alternative, one end of the first thyristor is electrically connected to phase A of the power grid, and the other end is connected to one end of the auxiliary relay of phase A circuit; the other end of the auxiliary relay of phase A circuit is connected to the phase A incoming line of the output branch protection circuit breaker of phase A circuit; and one end of the magnetic latching relay of phase A circuit is electrically connected to phase A of the power grid, and the other end is connected to the phase A incoming line of the output branch protection circuit breaker of phase A circuit.
[0012] As an optional approach, multiple auxiliary relays for phase A circuit, protective circuit breakers for output branches of phase A circuit, and magnetic latching relays for phase A circuit are respectively provided.
[0013] As an alternative, 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 auxiliary relay of the C-phase circuit; the other end of the auxiliary relay of the C-phase circuit is connected to the C-phase input line of the C-phase circuit output branch protection circuit breaker; and one end of the magnetic latching relay of the C-phase circuit is electrically connected to the C-phase of the power grid, and the other end is connected to the C-phase input line of the C-phase circuit output branch protection circuit breaker.
[0014] As an optional approach, multiple auxiliary relays for the C-phase circuit, protection circuit breakers for the output branches of the C-phase circuit, and magnetic latching relays for the C-phase circuit are provided.
[0015] As an alternative, the composite switch control system is used to connect any thyristor, magnetic latching relay, and auxiliary relay.
[0016] As an optional approach, the multi-channel 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.
[0017] As an optional configuration, there are 2 thyristor drive circuits, 12 magnetic latching relay drive circuits, and 12 auxiliary relay drive circuits.
[0018] As an optional approach, the voltage sampling circuit and the signal conditioning circuit are used for voltage zero-point and frequency quiescence detection; the input of the signal conditioning circuit is connected to the voltage sampling circuit, the current transformer, and the temperature sampling interface circuit, respectively.
[0019] As an alternative, a temperature sampling interface circuit and a signal conditioning circuit are used to detect the capacitor temperature.
[0020] The beneficial effects of this utility model are as follows:
[0021] This invention uses a thyristor series auxiliary relay to replace the thyristor. Compared with the traditional composite switch, it does not require complex and numerous trigger circuits and thyristor circuits, and it does not have the problem of damage caused by overvoltage mis-connection due to lightning strikes, etc. It reduces circuit components, simplifies system control, and improves the reliability and safety of the composite switch. Attached Figure Description
[0022] Figure 1 A schematic diagram of the circuit structure provided for an embodiment of this utility model;
[0023] Figure 2 A schematic diagram of the functional modules of the multi-channel composite switch control system provided in the embodiment of this utility model. Detailed Implementation
[0024] To enable those skilled in the art to better understand the technical solution of this utility model, the present utility model will be further described in detail below with reference to specific embodiments.
[0025] Please see Figure 1 and Figure 2 This embodiment provides a multi-channel composite switch for low-voltage capacitor switching, including: a multi-channel composite switch control system, thyristors, a magnetic latching relay, an auxiliary relay, and an output branch protection circuit breaker; the thyristors include a first thyristor and a second thyristor; the magnetic latching relay and the auxiliary relay are used to form connection paths with the branch where the first thyristor is located and the branch where the second thyristor is located; wherein, phase A of the power grid is sequentially connected to the first thyristor, the phase A circuit auxiliary relay, and the phase A circuit output branch protection circuit breaker to form the first phase A path. That is, the first thyristor is the phase A thyristor.
[0026] Phase A of the power grid is sequentially connected to the phase A magnetic latching relay and the phase A circuit output branch protection circuit breaker to form the second path of phase A; Phase C of the power grid is sequentially connected to the first thyristor, the phase C circuit auxiliary relay, and the phase C circuit output branch protection circuit breaker to form the first path of phase C; Phase C of the power grid is sequentially connected to the phase C magnetic latching relay and the phase C circuit output branch protection circuit breaker to form the second path of phase C. That is, the second thyristor is the phase C thyristor.
[0027] The B phase of the power grid is connected to the incoming line of the output branch protection circuit breaker of the B phase circuit; and the outgoing lines of the output branch protection circuit breakers of the A phase circuit, B phase circuit, and C phase circuit are respectively connected to compensation capacitors.
[0028] Please refer to it again. Figure 1 In this embodiment, a 6-way circuit is used for illustration. Figure 1 In the diagram, A, B, and C are the three-phase busbars of the power grid system. ① is an auxiliary relay, ② is a magnetically latched relay, ③ is a thyristor, ④ is a low-voltage reactive power compensation capacitor, and ⑤ is a miniature circuit breaker. The low-voltage reactive power compensation capacitor typically uses a delta connection. When branches A and C are both disconnected, phase B cannot form a closed loop with other phases, effectively leaving phase B unconnected to the system. Therefore, the phase B branch can be simplified by removing the thyristor, auxiliary relay, and magnetically latched relay, leaving only a miniature circuit breaker for isolation, thus saving on equipment investment. Branches A and C can use the auxiliary relay to pre-select the branch to be switched, allowing the thyristor to be switched to the required branch in advance. Therefore, the 1-6 thyristor and drive circuits can be simplified, retaining only one thyristor group and drive circuit per phase, further saving on equipment investment.
[0029] Specifically, the magnetic latching relays include magnetic latching relays for each branch corresponding to phase A and phase C; the auxiliary relays include auxiliary relays for each branch corresponding to phase A and phase C; one end of the phase A thyristor group is electrically connected to phase A of the power grid, and the other end is connected to one end of auxiliary relays 1 to 6 of phase A; the other ends of auxiliary relays 1 to 6 of phase A are respectively connected to the phase A incoming line of the protection circuit breaker for output branches 1 to 6; one end of magnetic latching relays 1 to 6 of phase A is electrically connected to phase A of the power grid, and the other end is respectively connected to the phase A incoming line of the protection circuit breaker for output branches 1 to 6; phase C One end of the thyristor is electrically connected to phase C of the power grid, and the other end is connected to one end of auxiliary relays 1-6 of phase C. The other ends of auxiliary relays 1-6 of phase C are respectively connected to the input line of phase C of the output branch protection circuit breaker 1-6. One end of magnetic latching relay 1-6 of phase C is electrically connected to phase C of the power grid, and the other end is respectively connected to the input line of phase C of the output branch protection circuit breaker 1-6. Phase B of the power grid is electrically connected to the input line of phase B of the output branch protection circuit breaker 1-6. The output lines A, B, and C of the output branch protection circuit breaker 1-6 are respectively connected to the terminals A, B, and C of the compensation capacitors. Therefore, in this embodiment... Figure 1 The circuit includes thyristor Q1 for phase A, auxiliary relays Ka1-Ka6, magnetic latching relays Ka11-Ka16, thyristor Q2 for phase C, auxiliary relays Kc1-Kc6, magnetic latching relays Kc11-Kc16, circuit breakers QF1-QF6, and capacitors C1-C6.
[0030] Based on the above scheme, the working principle of this embodiment is to use the voltage zero-crossing point to trigger the thyristor to conduct, and when the current is zero, the thyristor automatically disconnects, without generating inrush current.
[0031] The specific working process of zero-voltage turn-on is as follows: First, the auxiliary relay Ka1 is closed to pre-select thyristor Q1 to the first capacitor C1. When the voltage difference between A and a1 is detected to be zero, thyristor Q1 is triggered to conduct. After thyristor Q1 is stably turned on, the magnetic latching relay Ka11 is closed to achieve zero-voltage, inrush-current-free turn-on. After the magnetic latching relay Ka11 is stably turned on, the thyristor Q1 and the auxiliary relay Ka1 are triggered to disconnect in sequence to achieve low-power turn-on.
[0032] The turn-off process is similar to the turn-on process, except that the turn-on process is triggered by a timing sequence that controls the conduction when the voltage difference between A and a1 is zero, while the turn-off process is triggered by a timing sequence that automatically turns off when the current in A crosses zero. The specific working process of zero-current turn-off is as follows: First, the auxiliary relay Ka1 is closed to pre-select thyristor Q1 to the first capacitor C1. After the auxiliary relay Ka1 is stably turned on, it triggers the conduction of thyristor Q1. After the thyristor Q1 is stably turned on, the magnetic latching relay Ka11 is opened and triggers the opening of Q1. 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 opened. After Q1 is stably opened, Ka1 is opened. Since the main circuit current is zero, no arc is generated during the opening process of Ka1, and finally zero-current turn-off is achieved.
[0033] Furthermore, the multi-channel composite switch control system in 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, twelve magnetic latching relay drive circuits, twelve auxiliary relay drive circuits, a system power supply circuit, a switch status 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 connected to the voltage sampling circuit, the current transformer, and the temperature sampling interface circuit, respectively. 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 connected to the two thyristor drive circuits, the twelve magnetic latching relay drive circuits, the twelve auxiliary relay drive circuits, and the composite switch status display circuit, respectively. 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 for detecting the capacitor temperature and transmit it to the digital control system. The composite switch status display circuit is mainly used to monitor the working status of multiple composite switches and provide corresponding fault alarms and fault information. In order to ensure the electrical safety of the capacitor compensation branch, an output branch protection circuit breaker (miniature circuit breaker) is introduced to ensure that the capacitor can be disconnected from the power grid when the equipment fails.
[0034] exist Figure 2In this circuit, V represents the voltage sampling circuit, I represents the current transformer, E represents the temperature sampling interface circuit, N represents the signal conditioning circuit, P represents the digital control system, D1 represents two thyristor drive circuits, D2 represents twelve auxiliary relay drive circuits, D3 represents twelve magnetic latching relay drive circuits, SCR represents a thyristor, S represents an auxiliary relay, R represents a magnetic latching relay, and F represents the composite switch status display circuit. The voltage sampling circuit V and the signal conditioning circuit N are mainly used for voltage detection, providing control basis for the zero-voltage turn-on and current zero-crossing turn-off of the multi-channel composite switch. The current transformer I and the signal conditioning circuit N are mainly used for current detection, providing control basis for thyristor fault and overcurrent protection of the multi-channel composite switch. The multi-channel composite switch status display circuit F is mainly used for monitoring the operating status of the multi-channel composite switch and providing corresponding fault alarms and fault information. Since capacitors generate heat during long-term operation, the temperature detection interface E is the input interface of the capacitor temperature sensor, which, after passing through the signal conditioning circuit N, provides a basis for over-temperature protection.
[0035] The above are merely preferred embodiments of this utility model. It should be noted that the above preferred embodiments should not be considered as limitations on this utility model, and the scope of protection of this utility model should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of this utility model, and these improvements and modifications should also be considered within the scope of protection of this utility model.
Claims
1. A multi-channel composite switch for low-voltage capacitor switching, characterized in that, include: Multi-channel composite switch control system, thyristors, magnetic latching relays, auxiliary relays and output branch protection circuit breakers; 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; Specifically, phase A of the power grid is sequentially connected to the first thyristor, the auxiliary relay of phase A circuit, and the output branch protection circuit breaker of phase A circuit to form the first path of phase A; phase A of the power grid is sequentially connected to the magnetic latching relay of phase A circuit and the output branch protection circuit breaker of phase A circuit to form the second path of phase A. The first path of the C phase is formed by sequentially connecting the first thyristor, the auxiliary relay of the C phase circuit, and the protection circuit breaker of the output branch of the C phase circuit; the second path of the C phase is formed by sequentially connecting the C phase magnetic latching relay and the protection circuit breaker of the output branch of the C phase circuit. The B phase of the power grid is connected to the incoming line of the output branch protection circuit breaker of the B phase circuit; and the outgoing lines of the output branch protection circuit breakers of the A phase circuit, B phase circuit, and C phase circuit are respectively connected to compensation capacitors.
2. A multi-channel composite switch for low-voltage capacitor switching according to claim 1, characterized in that, One end of the first thyristor is electrically connected to phase A of the power grid, and the other end is connected to one end of the auxiliary relay of phase A circuit; the other end of the auxiliary relay of phase A circuit is connected to the phase A incoming line of the output branch protection circuit breaker of phase A circuit. Additionally, one end of the magnetic latching relay in phase A circuit is electrically connected to phase A of the power grid, and the other end is connected to the phase A incoming line of the output branch protection circuit breaker of phase A circuit.
3. A multi-channel composite switch for low-voltage capacitor switching according to claim 2, characterized in that, The A-phase circuit auxiliary relay, the A-phase circuit output branch protection circuit breaker, and the A-phase circuit magnetic latching relay are each provided in multiple quantities.
4. A multi-channel composite switch for low-voltage capacitor switching according to claim 1, characterized in that, 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 the C phase input 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 input line of the C phase circuit output branch protection circuit breaker.
5. A multi-channel composite switch for low-voltage capacitor switching according to claim 4, characterized in that, The C-phase circuit auxiliary relay, the C-phase circuit output branch protection circuit breaker, and the C-phase circuit magnetic latching relay are each provided in multiple quantities.
6. A multi-channel composite switch for low-voltage capacitor switching according to claim 1, characterized in that, The multi-channel composite switch control system is used to connect any of the thyristors, magnetic latching relays, and auxiliary relays.
7. A multi-channel composite switch for low-voltage capacitor switching according to claim 1, characterized in that, The multi-channel 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.
8. A multi-channel composite switch for low-voltage capacitor switching according to claim 7, characterized in that, The system includes two thyristor drive circuits, twelve magnetic latching relay drive circuits, and twelve auxiliary relay drive circuits.
9. A multi-channel composite switch for low-voltage capacitor switching according to claim 7, characterized in that, The voltage sampling circuit and signal conditioning circuit are used for voltage zero-point and frequency quiescence detection; the input of the signal conditioning circuit is connected to the voltage sampling circuit, the current transformer, and the temperature sampling interface circuit, respectively.
10. A multi-channel composite switch for low-voltage capacitor switching according to claim 7, characterized in that, The temperature sampling interface circuit and signal conditioning circuit are used to detect the capacitor temperature.