Bypass post-starting loop monitoring and protecting device
By introducing low-voltage current transformers and current relays into the starter cabinet, monitoring the reactor current and delaying the fault output, the current impact problem during the motor start-up process is solved, cost and space requirements are reduced, and equipment operation safety is improved.
Patent Information
- Application Number
- CN202421537933.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-02
- Publication Date
- 2025-07-25
- Estimated Expiration
- 2034-07-02
AI Technical Summary
In the prior art, the current impact problem during the motor start-up process leads to waste of power grid resources and equipment damage, and the high-voltage vacuum contactor is costly and takes up a large space, making it difficult to effectively solve.
The low-voltage current transformer and current relay are introduced into the starter cabinet to monitor the current signal of the reactor, and protect the operation through the relay control loop. Combined with the time relay delays the fault output, avoids reactor damage and reduces cost and space requirements.
It realizes effective protection of reactors, reduces equipment costs and space requirements, improves operating safety, avoids damage to reactor insulation windings, and reduces waste of power grid resources.
Smart Images
Figure CN223156691U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of power system drive, and particularly relates to a monitoring and protection device for a starting circuit after bypassing. Background Technique
[0002] In the technical field of high-voltage motor drive, the soft start of motors has been seeking a suitable balance point. A large current impact during the starting process is an unavoidable topic. Allocating a large system capacity will cause waste of grid resources. Even if the corresponding amount of electricity is not consumed, unnecessary fines will occur due to the long-term supply standby on the power supply side. Allocating a small system capacity makes it difficult to smoothly start the motor. Selecting a soft start scheme can effectively reduce the system capacity allocation of the power grid and at the same time reduce the interference to other on-line operating equipment during the starting process.
[0003] During the normal operation of the motor, the current after bypassing the motor all reaches the motor terminal through the contactor KM. When an accident occurs at the contactor outlet, such as the contactor's main contacts cannot be closed due to the poor contact of the contacts or the damage of the coil, a part of the motor current, or even most of it, will pass through the reactor to reach the motor. The characteristics of the reactor itself determine that it cannot flow through a large current for a long time, otherwise it will cause damage to the insulating winding of the reactor and it cannot be used again. In the prior art, usually a high-voltage vacuum contactor switch for strong electrical isolation of the main circuit is used to avoid this situation, but the cost of the high-voltage vacuum contactor for isolation is relatively high, and the installation space requirements for the electrical clearance in the starting cabinet are relatively high. Content of the Utility Model
[0004] The purpose of the utility model is to provide a monitoring and protection device for a starting circuit after bypassing, which can reduce costs, compress the installation space requirements for electrical clearance in the starting cabinet, and has the effect of improving the overall operation safety factor of the equipment.
[0005] The above technical purpose of the utility model is achieved through the following technical solutions: a monitoring and protection device for a starting circuit after bypassing, including a starting cabinet for soft starting of a motor. The starting cabinet includes a front-end current transformer, a rear-end current transformer, a voltage transformer, a circuit breaker, a reactor, and a bypass contactor. The bypass contactor is connected in parallel at both ends of the reactor. The front-end current transformer is connected to the incoming line end of the circuit breaker, and the rear-end current transformer is connected to the outgoing line end of the reactor. A monitoring and protection unit is arranged in the starting cabinet, and the monitoring and protection unit is used to monitor the current signal of the reactor after bypassing and output a protection action signal after sensing an abnormal current signal.
[0006] The utility model is further configured as follows: the monitoring and protection unit includes a current monitoring module, the current monitoring unit includes a low-voltage current transformer and a current relay, the low-voltage current transformer is used to detect the current signal of the reactor after bypass, and the low-voltage current transformer and the current relay are both arranged in the starting cabinet.
[0007] The utility model is further configured as follows: the current relay constantly monitors the abnormal current signal flowing through the reactor after bypassing, outputs a protection action signal after a set time, and the circuit breaker and the bypass contactor receive the protection action signal and disconnect.
[0008] The utility model is further configured as follows: the monitoring and protection unit further includes an isolation circuit, the isolation circuit includes a time relay, the time relay is arranged in the starting cabinet, and the time relay is used to realize the function of delaying fault output.
[0009] The utility model is further configured as follows: the low-voltage current transformer is arranged on one side of the reactor, and the high-voltage cable at the outlet end of the reactor passes through the low-voltage current transformer.
[0010] The utility model is further configured as follows: the outgoing line end of the reactor is connected to the motor to be controlled via the rear-end current transformer.
[0011] The beneficial effects of the utility model are:
[0012] 1. The utility model adds a low-voltage current transformer for current detection of the reactor in the starting part of the primary main circuit, converts the detected current signal of the reactor after bypassing through electromagnetic induction and then connects it to the current relay for amplitude judgment, and realizes the protection and monitoring function of the starting circuit reactor after bypass operation through the action of a specific relay control circuit; saves the cost of a high-voltage contactor switch for strong electrical isolation of the main circuit, reduces the manufacturing cost of the shell material and mechanical processing technology, and improves the safety factor of the overall operation of the equipment with minimal technical transformation expenditure and material increase.
[0013] 2. The utility model is provided with a current relay, which constantly detects the abnormal current flowing through the reactor in the starting circuit after bypassing, and outputs a protection action signal after a set time.
[0014] 3. In the utility model, by monitoring the status of the circuit breaker and the bypass contactor during the starting and bypassing process, the action signal of the current relay when a large current flows during the starting process is shielded to avoid the occurrence of false alarm faults.
[0015] 4. The utility model adds a time relay after the bypass to realize the function of delaying fault output, filtering out the control logic disorder caused by the untimely switching due to the mechanical action time difference of the contactor coil.
[0016] 5. In the utility model, the current detection adopts the installation method of a low-voltage transformer passing through a high-voltage cable, reducing the requirements for the installation space due to the electrical clearance and the material cost of the transformer itself. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In order to more clearly illustrate the technical solutions in the embodiments of the utility model, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the utility model. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.
[0018] Figure 1 It is the electrical system structure diagram of the utility model.
[0019] Figure 2 It is the structural schematic diagram of the monitoring and protection unit of the utility model.
[0020] Figure 3 It is the structural schematic diagram of the isolation circuit of the utility model.
[0021] Figure 4 It is the structural schematic diagram of the starting cabinet of the utility model.
[0022] In the figure, 1. Starting cabinet; 2. Front-end current transformer; 3. Rear-end current transformer; 4. Voltage transformer; 5. Circuit breaker; 6. Reactor; 7. Bypass contactor; 8. Low-voltage current transformer; 9. Current relay; 10. Time relay; 11. High-voltage cable. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0023] The following will clearly and completely describe the technical solutions of the utility model in combination with specific embodiments. Obviously, the described embodiments are only some embodiments of the utility model, rather than all embodiments. Based on the embodiments of the utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the utility model.
[0024] Embodiment: Please refer to FIGS. 1 - 4. A monitoring and protection device for a post - bypass start - up circuit includes a starting cabinet 1, which is used for the soft start of a motor. The starting cabinet 1 includes a front - end current transformer 2, a rear - end current transformer 3, a voltage transformer 4, a circuit breaker 5, a reactor 6, and a bypass contactor 7. The bypass contactor 7 is connected in parallel at both ends of the reactor 6. The front - end current transformer 2 is connected to the incoming line end of the circuit breaker 5, and the rear - end current transformer 3 is connected to the outgoing line end of the reactor 6. A monitoring and protection unit is arranged in the starting cabinet 1, and the monitoring and protection unit is used to monitor the current signal of the reactor 6 after bypass and output a protection action signal when an abnormal current signal is sensed; The monitoring and protection unit includes a current monitoring module. The current monitoring unit includes a low - voltage current transformer 8 and a current relay 9. The low - voltage current transformer 8 is used to detect the current signal of the reactor 6 after bypass, and both the low - voltage current transformer 8 and the current relay 9 are arranged in the starting cabinet 1.
[0025] Specifically, during normal operation, the current after the motor bypass all passes through the bypass contactor 7 to reach the motor end. When an unexpected situation occurs to the bypass contactor 7, such as the contact not being firmly attracted or the coil being damaged and the main contact of the contactor cannot be closed, a part or even most of the motor current will pass through the reactor 6 to reach the motor. The characteristics of the reactor 6 itself determine that it cannot withstand a large current for a long time, otherwise it will cause damage to the insulation winding of the reactor 6 and it cannot be used again. Considering this situation, a current transformer is connected in series in the start - up circuit of the reactor 6 to monitor the current state in the start - up circuit, so as to determine whether the bypass contactor 7 is working effectively. A low - voltage current transformer 8 for detecting the current of the reactor 6 is added in the primary main - circuit start - up part. The monitored current signal is converted through electromagnetic induction and then connected to the current relay 9 for amplitude judgment, and through the action of a specific relay control circuit, the protection and monitoring function of the reactor 6 in the start - up circuit after bypass operation is realized.
[0026] As Figure 2 、 Figure 3 shown, the current relay 9 constantly monitors the abnormal current signal flowing through the reactor 6 after bypass. After a set time, it outputs a protection action signal (i.e., a tripping signal), and the circuit breaker 5 and the bypass contactor 7 receive the protection action signal and disconnect.
[0027] As Figure 3 、 Figure 4As shown, the monitoring and protection unit further includes an isolation circuit. The isolation circuit includes a time relay 10, which is arranged in the starting cabinet 1. The time relay 10 is used to realize the function of delaying fault output. Specifically, after the circuit breaker 5 is closed, the motor starts; after the motor startup is completed, the bypass contactor 7 is closed; the current relay 9 continuously monitors the current flowing through the reactor 6 in the starting circuit. Before the bypass contactor 7 is closed, the current flowing through the current relay 9 is normal. After the bypass contactor 7 is closed, the current flowing through the current relay 9 is abnormal. However, there is a time delay for this abnormality because there is a time difference of dozens of milliseconds for the closing of the bypass contact. It is necessary to judge whether the abnormal current should be output through the auxiliary point of the bypass contact. When the abnormal state of the current lasts longer than the closing time of the bypass contactor 7, it is necessary to isolate the current signal during the abnormal time period through the time relay 10, so as to realize the function of delaying fault output and filter out the control logic disorder caused by the untimely switching of the mechanical action time difference of the contactor coil.
[0028] Further, as Figure 4 shown, the low-voltage current transformer 8 is arranged on one side of the reactor 6, and the high-voltage cable 11 at the outlet end of the reactor 6 passes through the low-voltage current transformer 8.
[0029] Further, the outlet end of the reactor 6 is connected to the motor to be controlled through the rear-end current transformer 3.
[0030] The working principle of the present utility model:
[0031] The low-voltage current transformer 8 is connected in series in the primary main circuit startup part. The monitored current signal is converted through electromagnetic induction and then connected to the current relay 9 for amplitude judgment. The current relay 9 continuously monitors the abnormal current signal flowing through the reactor 6 after bypassing. After a set time, a protection action signal is output, that is, a tripping signal is output to the circuit breaker 5 and the bypass contactor 7, so as to realize the protection monitoring of the reactor 6 in the starting circuit after bypass operation.
Claims
1. A bypass post-start circuit monitoring and protection device, characterized in that: It includes a starting cabinet (1) which is used for the soft start of a motor. The starting cabinet (1) includes a front current transformer (2), a rear current transformer (3), a voltage transformer (4), a circuit breaker (5), a reactor (6) and a bypass contactor (7). The bypass contactor (7) is connected in parallel at both ends of the reactor (6). The front current transformer (2) is connected to the incoming line end of the circuit breaker (5), and the rear current transformer (3) is connected to the outgoing line end of the reactor (6). A monitoring and protection unit is arranged in the starting cabinet (1), and the monitoring and protection unit is used for monitoring the current signal of the reactor (6) after bypass and outputting a protection action signal after sensing an abnormal current signal.
2. The bypass post-start circuit monitoring and protection device according to claim 1, characterized in that: The monitoring and protection unit includes a current monitoring module. The current monitoring unit includes a low-voltage current transformer (8) and a current relay (9). The low-voltage current transformer (8) is used for detecting the current signal of the reactor (6) after bypass. Both the low-voltage current transformer (8) and the current relay (9) are arranged in the starting cabinet (1).
3. The bypass post-start circuit monitoring and protection device according to claim 2, characterized in that: The current relay (9) constantly monitors the abnormal current signal flowing through the reactor (6) after bypass, and outputs a protection action signal after a set time. The circuit breaker (5) and the bypass contactor (7) receive the protection action signal and disconnect.
4. The bypass post-start circuit monitoring and protection device according to claim 2, wherein: The monitoring and protection unit also includes an isolation circuit. The isolation circuit includes a time relay (10). The time relay (10) is arranged in the starting cabinet (1), and the time relay (10) is used for realizing the function of delaying fault output.
5. The bypass post-start circuit monitoring and protection device according to claim 2, characterized in that: The low-voltage current transformer (8) is arranged on one side of the reactor (6), and the high-voltage cable (11) at the outgoing line end of the reactor (6) passes through the low-voltage current transformer (8).
6. The bypass post-start circuit monitoring and protection device according to claim 1, characterized in that: The outgoing line end of the reactor (6) is connected to the motor to be controlled through the rear current transformer (3).