CN204349424U - Microcomputer transformer backup protection loop - Google Patents

Abstract

A microcomputer transformer backup protection circuit, including an OR gate for inputting the negative sequence voltage signal of the low-voltage side of the main transformer and the low-voltage signal of the low-voltage side of the main transformer, the output terminal of the OR gate is connected with a first AND gate, and the other gate of the first AND gate One of the input terminals is to release the main transformer complex voltage locking terminal, and its special feature is that there is an idle normally closed contact of the secondary side switch of the main transformer at the release main transformer complex voltage locking terminal, which is used to input the voltage exit signal of the low voltage side of the main transformer , the output terminal of the first AND gate is connected with the second AND gate through the complex voltage lock-out control switch, the other input terminal of the second AND gate is used to input the current signal of the high voltage side of the main transformer, the output terminal of the second AND gate After the delayer, the trip signal output terminal and the trip outlet are led out. The utility model directly connects the normally closed node of the switch on the two sides of the main transformer to the protection device to realize the automatic withdrawal of the re-pressure locking function on the low-voltage side, without the need for operating personnel to operate, which can prevent the backup protection of the dead zone from refusing to operate. The main transformer is damaged and the accident expands.

Description

Microcomputer Transformer Backup Protection Circuit

technical field

The utility model relates to a backup protection circuit of a microcomputer transformer.

Background technique

In order to reflect the overcurrent caused by the external short-circuit fault of the transformer and as a backup for longitudinal differential protection and gas protection, the transformer should be equipped with a backup protection that reflects the phase-to-phase or ground short-circuit fault, that is, trip the corresponding circuit breaker with a delay. According to the requirements of transformer capacity and protection sensitivity, the transformer backup protection (composite voltage blocking overcurrent protection) should choose overcurrent protection, overcurrent protection initiated by composite voltage (negative sequence voltage and line voltage), or composite current protection (negative sequence current and single-phase voltage-triggered current protection). The overcurrent protection through complex voltage blocking can reduce the operating current and has high sensitivity, so it has been widely used in the backup protection device of the main transformer.

Composite voltage blocking overcurrent protection is composed of composite voltage element, overcurrent element and time element. It is used as backup protection for short-circuit faults of main transformer and adjacent equipment. The access current of this protection is the secondary three-phase current of TA on one side of the main transformer. The input voltage is the secondary three-phase voltage of the TV on this side or the other side of the main transformer.

Some transformer backup protections are only equipped with backup protection on the high-voltage side. Generally, the input current is the secondary three-phase current of the main transformer high-voltage side TA, and the input voltage is the secondary three-phase voltage of the main transformer low-voltage side TV. When the voltage on the low-voltage side of the transformer drops, or the negative-sequence voltage is greater than the set value and the overcurrent on the high-voltage side starts, the protection action will cut off the transformer after a delay.

For devices that are only equipped with backup protection on the high-voltage side, when the re-voltage blocking function is enabled, the over-current protection can trip at the outlet only after the bus voltage on the low-voltage side meets the opening conditions of the re-voltage blocking.

As shown in Figure 1, the primary system of the 66KV substation has 2 main transformers, the transformation level is 66/10KV, and the 10KV is single-bus section wiring.

The backup protection of the 66KV main transformer in the substation is only equipped with high backup protection, the access current is the secondary three-phase current of the main transformer 66KV side TA, and the access voltage is the secondary three-phase voltage of the 10KV bus TV. The phase overcurrent stage I protection, the phase overcurrent stage II protection are enabled, the phase overcurrent stage I stage re-pressure lockout is enabled, and the phase overcurrent stage II stage repressurization lockout is enabled. Low and low voltage, negative sequence overvoltage input for complex pressure lockout value.

When the #1 main transformer is out of service for maintenance, the 10KVI section I bus is powered by the #2 main transformer through the 10KV bus tie switch. After the overhaul of #1 main transformer is completed, the operation of power transmission and commissioning is carried out. During the process of restoring the power transmission operation of #1 main transformer, there is a protection dead zone d1 between the secondary side CT of #1 main transformer and the switch. If a three-phase short-circuit fault occurs in this dead zone, the overcurrent protection of the backup protection on the high-voltage side of the #1 main transformer will start. However, since the 10KVI section I busbar is normally charged at this time, the busbar voltage on the low-voltage side is at the rated value, and the busbar voltage on the low-voltage side will be re-voltage blocked. , #1 main transformer backup protection also does not act. There is no protection installed on the 66KV line in the station. At this time, the short circuit fault cannot be removed, and the line protection of the superior substation needs to act to remove the short circuit fault after a delay. Since the time to remove the fault is generally 3-5 seconds, and the thermal stabilization time of the general main transformer cannot exceed 2s, the backup protection refusal accident in this dead zone may cause damage to the main transformer and expand the scope of the accident.

Utility model content

If the utility model is to provide a backup protection circuit of a microcomputer transformer suitable for the backup protection of the main transformer with only high backup protection, the protection circuit can prevent the backup protection in the dead zone from refusing to operate, and prevent the damage of the main transformer and the expansion of the accident.

The microcomputer transformer backup protection circuit includes an OR gate for inputting the negative-sequence voltage signal of the main transformer low-voltage side and the low-voltage signal of the main transformer low-voltage side. The output terminal of the OR gate is connected with a first AND gate, and the other gate of the first AND gate is The input terminal is the release terminal of the main transformer complex voltage lockout, and its special feature is that there is an idle normally closed contact of the secondary side switch of the main transformer at the release terminal of the main transformer complex voltage lockout, which is used to input the voltage exit signal of the low voltage side of the main transformer, The output terminal of the first AND gate is connected to the second AND gate through the complex voltage lock-out control word, and the other input terminal of the second AND gate is used to input the current signal of the high voltage side of the main transformer, and the output terminal of the second AND gate is passed through After the delayer, the trip signal output terminal and the trip outlet are led out.

The beneficial effects of the utility model are: simple structure, reliable function, using the combination of the AND gate and the OR gate, when the secondary switch of the main transformer is in the split position, the normally closed contact of the secondary side switch of the main transformer is connected, and the reset of the main transformer is released. When the positive voltage signal is obtained from the voltage lock terminal, the first AND gate is opened and the low-voltage side complex voltage lockout function is exited. When the backup protection device detects the overcurrent start, the second AND gate is activated, and the trip signal is output after a delay by the delayer. At the same time, the switch on the high-voltage side and low-voltage side of the main transformer is tripped, so as to realize the direct tripping of the outlet without re-pressure lockout. When the secondary switch of the main transformer is in the closed position, the normally closed contact is disconnected, and the complex pressure locking function is put into use. The utility model directly connects the normally closed contact of the switch on both sides of the main transformer to the protection device to realize the automatic withdrawal of the re-pressure locking function on the low-voltage side, without the need for operators to operate, which can prevent the backup protection of the dead zone from refusing to operate, and prevent the main transformer Damage and accident expansion.

Description of drawings

Figure 1 is a schematic diagram of the primary system of a 66KV substation;

Fig. 2 is a schematic circuit diagram of the utility model.

Detailed ways

As shown in Figure 2, the microcomputer transformer backup protection circuit includes an OR gate for inputting the negative-sequence voltage signal on the low-voltage side of the main transformer and the low-voltage signal on the low-voltage side of the main transformer. The other input terminal of an AND gate is the release terminal of the main transformer complex voltage lockout, and the idle normally closed contact of the secondary side switch of the main transformer is connected to the release terminal of the main transformer complex voltage lockout to input the main transformer low voltage side voltage exit signal, The output terminal of the first AND gate is connected with the second AND gate through the complex voltage lock-out control switch, and the other input terminal of the second AND gate is used to input the current signal of the high voltage side of the main transformer, and the output terminal of the second AND gate is passed through After the delayer, the trip signal output terminal and the trip outlet are led out.

Claims (1)

1. A microcomputer transformer backup protection circuit, including an OR gate for inputting the negative-sequence voltage signal on the low-voltage side of the main transformer and the low-voltage signal on the low-voltage side of the main transformer, the output terminal of the OR gate is connected with a first AND gate, and the first AND gate The other input terminal of the main transformer is to release the main transformer complex voltage locking terminal, and its characteristic is: the normally closed contact of the idle main transformer secondary side switch is connected to the release main transformer complex voltage locking terminal to input the main transformer low voltage side voltage exit signal , the output terminal of the first AND gate is connected with the second AND gate through the complex voltage lock-out control switch, the other input terminal of the second AND gate is used to input the current signal of the high voltage side of the main transformer, the output terminal of the second AND gate After the delayer, the trip signal output terminal and the trip outlet are led out.