Transformer short-circuit protection device
A simplified transformer short-circuit protection device using an intermediate relay and bidirectional thyristor ensures immediate power cutoff during short circuits, addressing complexity and cost issues of existing devices while enhancing safety.
Patent Information
- Application Number
- CN202411635068.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-15
- Publication Date
- 2024-12-27
AI Technical Summary
Existing transformer short-circuit protection devices are complex and costly, posing challenges in ensuring reliable and efficient protection against transformer failures.
A simplified transformer short-circuit protection device comprising an intermediate relay, power-on delay relay, bidirectional thyristor, voltage regulator, resistors, and fuses, which triggers immediate cutoff of the primary side of the transformer during a short circuit.
The device provides effective protection by immediately cutting off power to the transformer during a short circuit, ensuring safe operation and preventing potential explosions.
Smart Images
Figure CN119209408A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a protection circuit of a transformer and belongs to the field of transformers. Background Art
[0002] The transformer is a very important power supply equipment in the power system. If the transformer fails, it will affect the reliability of the power supply to a certain extent, as well as the normal operation of the system. The transformer is a very important power supply equipment in the power system. If the transformer fails, it will affect the reliability of the power supply to a certain extent, as well as the normal operation of the system.
[0003] Common faults and abnormal operating conditions of power transformers The primary and secondary windings inside the transformer tank may experience phase-to-phase short circuits, turn-to-turn short circuits, single-phase ground short circuits on the neutral point directly grounded system side windings, and insulation breakdown between the primary and secondary windings. Faults inside the tank generate arcs, causing violent gasification of the insulating oil, which may cause the transformer tank to explode. Phase-to-phase short circuits and ground short circuits may also occur in the external casing and lead wires of the tank. Abnormal operating conditions of the transformer mainly include overload, overcurrent caused by external short circuits, neutral point overvoltage caused by external ground short circuits, oil level reduction caused by tank leakage, or temperature increase caused by cooling system failures.
[0004] In order to ensure the safe operation of power transformers, prevent accidents from expanding, and ensure the safe and stable operation of the power system, corresponding relay protection devices can be installed according to the capacity, structure and fault type of the transformer. Among them, regarding the short-circuit protection device, according to the situation and abnormal operation mode, the transformer generally needs to be equipped with the following protection. Differential protection or current quick-break protection uses the current size and phase of the high and low voltage sides of the transformer to achieve differential protection. Longitudinal differential protection or current quick-break protection that reacts to transformer lead wire, bushing and internal short-circuit faults. Protect the transformer windings or lead wires from phase-to-phase short circuits, ground short circuits in large ground current systems, and short circuits between winding turns, and protect against instantaneous action to disconnect the circuit breakers on each side of the transformer. Existing transformer short-circuit protection devices are relatively complex and costly. Summary of the invention
[0005] In view of the problem that the existing transformer short-circuit protection device is relatively complicated, the present invention provides a transformer short-circuit protection device.
[0006] The transformer short-circuit protection device of the present invention comprises an intermediate relay KA, a power-on delay relay KT, a start button SB1, a stop button SB2, a bidirectional thyristor VTH, a voltage regulator VT, a resistor R1 and a resistor R2;
[0007] The start button SB1, the stop button SB2, the coil of the intermediate relay KA and the coil of the power-on delay relay KT are connected in series between the live wire L and the ground wire N, and the normally open contact KA-1 of the intermediate relay KA is connected in parallel to both ends of the start button SB1;
[0008] One end of the primary coil of the transformer T is connected to one end of the bidirectional thyristor VTH, the other end of the bidirectional thyristor VTH is connected to the live wire L, and the control end of the bidirectional thyristor VTH is connected to one end of the resistor R1; the normally open contact KA-2 of the intermediate relay KA and the normally closed contact of the power-on delay relay KT are connected in series and then connected in parallel to the two ends of the bidirectional thyristor VTH; the other end of the primary coil of the transformer T is grounded;
[0009] One end of the secondary coil of the transformer T is connected to one end of the voltage regulator tube VT and one end of the load at the same time; the other end of the secondary coil of the transformer T is connected to one end of the resistor R2 and the other end of the load at the same time; the common node of the other end of the voltage regulator tube VT and the resistor R2 is connected to the other end of the resistor R1.
[0010] Preferably, it also includes a fuse FU1 and a fuse FU2, wherein the fuse FU1 is connected in series in the primary coil circuit of the transformer T; and the fuse FU2 is connected in series in the secondary coil circuit of the transformer T.
[0011] Preferably, a circuit breaker QS is further included, and the live wire L and the ground wire N provide working power to the protection device through the circuit breaker QS.
[0012] Beneficial effects of the present invention: The transformer short-circuit protection device of the present invention has a simple structure. When a short circuit occurs, the trigger voltage of the bidirectional transistor disappears, and the primary side of the transformer is immediately cut off, so that the transformer is effectively protected. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 It is a circuit diagram of the transformer short-circuit protection device of the present invention. DETAILED DESCRIPTION
[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0015] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.
[0016] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.
[0017] Specific implementation method 1: The following is combined Figure 1 The transformer short-circuit protection device described in this embodiment includes an intermediate relay KA, a power-on delay relay KT, a start button SB1, a stop button SB2, a bidirectional thyristor VTH, a voltage regulator VT, a resistor R1 and a resistor R2;
[0018] The start button SB1, the stop button SB2, the coil of the intermediate relay KA and the coil of the power-on delay relay KT are connected in series between the live wire L and the ground wire N, and the normally open contact KA-1 of the intermediate relay KA is connected in parallel to both ends of the start button SB1;
[0019] One end of the primary coil of the transformer T is connected to one end of the bidirectional thyristor VTH, the other end of the bidirectional thyristor VTH is connected to the live wire L, and the control end of the bidirectional thyristor VTH is connected to one end of the resistor R1; the normally open contact KA-2 of the intermediate relay KA and the normally closed contact of the power-on delay relay KT are connected in series and then connected in parallel to the two ends of the bidirectional thyristor VTH; the other end of the primary coil of the transformer T is grounded;
[0020] One end of the secondary coil of the transformer T is connected to one end of the voltage regulator tube VT and one end of the load at the same time; the other end of the secondary coil of the transformer T is connected to one end of the resistor R2 and the other end of the load at the same time; the common node of the other end of the voltage regulator tube VT and the resistor R2 is connected to the other end of the resistor R1.
[0021] Furthermore, it also includes fuse FU1 and fuse FU2, wherein fuse FU1 is connected in series in the primary coil circuit of transformer T; and fuse FU2 is connected in series in the secondary coil circuit of transformer T. It is used for circuit overcurrent protection.
[0022] Furthermore, a circuit breaker QS is included, and the live wire L and the ground wire N provide working power to the protection device through the circuit breaker QS.
[0023] Working process:
[0024] When the start button SB1 is pressed, the coil of the intermediate relay KA is energized, and KA-1 is immediately closed to form a self-locking function, keeping the circuit Figure 1 The upper circuit in the middle remains in a closed state, the coil of the intermediate relay KA is energized, and its other contact KA-2 is also closed at the same time. KA-2 and the normally closed contact KT closed at this time form a path, so that the transformer T is energized and works;
[0025] When SB1 is pressed, the coil of the power-on delay relay KT is also energized synchronously, but its normally closed contacts are not disconnected immediately. During the delay process, the voltage across the bidirectional thyristor VTH is zero and it does not participate in the primary circuit of the transformer T. The path formed by the normally closed contacts of KT and KA-2 provides working power for the transformer T, so that the transformer starts working. After a delay of about 1 second, the normally closed contacts of the power-on delay relay KT are disconnected, and the bidirectional thyristor VTH participates in the primary coil circuit of the transformer T.
[0026] The voltage at the common node of VT and R2 is the trigger voltage of VTH. When the transformer T works normally, VTH is triggered to be in the on state. If the transformer T is short-circuited, the voltage across the voltage regulator tube VT is 0, and the VTH trigger voltage is 0, then VTH is turned off, which also turns off the primary circuit of the transformer T, loses the working power supply, and protects the transformer T.
[0027] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.
Claims
1. Transformer short-circuit protection device, characterized in that: It includes an intermediate relay KA, a power-on delay relay KT, a start button SB1, a stop button SB2, a bidirectional thyristor VTH, a voltage regulator VT, a resistor R1 and a resistor R2; The start button SB1, the stop button SB2, the coil of the intermediate relay KA and the coil of the power-on delay relay KT are connected in series between the live wire L and the ground wire N, and the normally open contact KA-1 of the intermediate relay KA is connected in parallel to both ends of the start button SB1; One end of the primary coil of the transformer T is connected to one end of the bidirectional thyristor VTH, the other end of the bidirectional thyristor VTH is connected to the live wire L, and the control end of the bidirectional thyristor VTH is connected to one end of the resistor R1; the normally open contact KA-2 of the intermediate relay KA and the normally closed contact of the power-on delay relay KT are connected in series and then connected in parallel to the two ends of the bidirectional thyristor VTH; the other end of the primary coil of the transformer T is grounded; One end of the secondary coil of the transformer T is connected to one end of the voltage regulator tube VT and one end of the load at the same time; the other end of the secondary coil of the transformer T is connected to one end of the resistor R2 and the other end of the load at the same time; the common node of the other end of the voltage regulator tube VT and the resistor R2 is connected to the other end of the resistor R1.
2. The transformer short-circuit protection device according to claim 1, characterized in that: It also includes fuse FU1 and fuse FU2. Fuse FU1 is connected in series in the primary coil circuit of transformer T; fuse FU2 is connected in series in the secondary coil circuit of transformer T.
3. The transformer short-circuit protection device according to claim 2, characterized in that: It also includes a circuit breaker QS, and the live wire L and the ground wire N provide working power to the protection device through the circuit breaker QS.