Classification of protection settings for oil immersed transformers
Writer： Hengfeng you electric Time：2021-09-26 views：times
The protection equipment of 10kV oil immersed distribution transformer mainly includes circuit breaker, load switch and fuse.
Circuit breaker, also known as switch, plays the role of connecting and breaking circuit in the circuit, but it has strong "arc extinguishing" ability, so it can not only control the breaking of electrical appliances, but also trip automatically in case of short circuit. Cut off the circuit; Circuit breaker, also known as switch, plays the role of connecting and disconnecting the circuit in the circuit, but it has strong "arc extinguishing" ability, so it can not only control the breaking of electrical appliances, but also automatically trip and cut off the circuit in the case of short circuit.
Load switch is developed on the basis of disconnector, namely knife switch. It has good operation ability and can cut off the load current. It has certain "arc extinguishing" ability, but the "arc extinguishing" ability is not large. The formation of "obvious disconnection point" is conducive to maintenance, but can not cut off the short-circuit current. Therefore, it is often used in combination with the fuse to solve the problem of obvious operation and disconnection point, and has the function of cutting off the short-circuit current.
A fuse is also called a fuse. It also plays the role of connecting and disconnecting the circuit in the circuit. Within its capacity range, it has strong "arc extinguishing" ability and can be used for the protection of electrical equipment; But no charge. Inconvenient operation or replacement.
Load breaking joint saves investment, but it can not break short-circuit current and is rarely used; The circuit breaker has good technical performance, but it has high equipment investment, complex use and unrealistic wide application; The protection configuration mode of load switch and fuse combination can avoid the use of complex and expensive circuit breaker, make up for the disadvantage that load switch can not break short-circuit current, and meet the needs of actual operation. Therefore, this configuration is often used as a protection method for oil immersed distribution transformers.
1. The opening and closing no-load oil immersed transformer has good performance.
The capacity of oil immersed transformer generally does not exceed 1250kva and rarely reaches 1600 kVA. The no-load current of the transformer is generally about 2% of the rated current, and the no-load current of the larger transformer is smaller.
When the ring network cabinet switches on and off the low current no-load oil immersed transformer, it has good performance and does not produce high overvoltage.
2. It has good protection performance for oil immersed transformer.
Using load switch to increase the breaking capacity of backup current limiting fuse is more effective than using circuit breaker, and sometimes the latter may not even play an effective protective role.
The data show that when the oil immersed transformer has a short-circuit fault, the pressure rise generated by the arc and the bubbles formed by gasification will occupy the space originally belonging to the oil, and the oil will transfer the pressure to the transformer tank. As the short circuit condition continues, the pressure will increase. Rise, causing deformation and cracking of oil tank body.
In order not to damage the fuel tank, the fault must be corrected within 20 ms. If the circuit breaker is used, due to the relay protection plus its own action time and arc extinguishing time, the full opening time is generally not less than 60ms, which can not effectively protect the transformer.
The backup current limiting fuse with high breaking capacity has fast breaking function and current limiting function, which can cut off the fault and limit the short-circuit current within 10ms, and can effectively protect the transformer.
Therefore, the backup current limiting fuse with high breaking capacity shall be used instead of the circuit breaker to protect the oil immersed transformer.
3. It has a certain price advantage. Although with the development of vacuum combination switches, some types of vacuum combination switches are cheaper than load switches, such as some domestic vacuum combination switches, they need to be equipped with corresponding protection devices, so they have no price advantage.
Therefore, the combination of load switch and high-voltage fuse has been widely used in the protection of small and medium-sized transformers.
2. Correct coordination between load switch and fuse
The fundamental difference between load switch and fuse is that fuse has the ability to break short-circuit current, while load switch only has the ability to break short-circuit current.
The above is the relevant explanation of HENGFENGYOU electric on the temperature parameters of oil immersed transformer. If you still don't understand, you can call + 86 15853252696 for further consultation. For comparison, we also provide the protection setting instructions of oil immersed transformer for more users to further understand. The protection setting of transformer is very important, which is not only related to the normal operation of transformer, but also related to the safety of power consumption and life and production. No technology is absolutely safe. Only we understand and actively monitor can we ensure everything.