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Is low voltage blocking overcurrent protection and compound voltage overcurrent protection the same?
Apr 11, 2018

These two kinds of protection are mostly used for backup protection of transformer, busbar and line, mainly to prevent overcurrent caused by external faults.


First, let's talk about low voltage starting overcurrent protection.

It is made up of two parts of low voltage relay and over current relay. When two components are acting at the same time, they can start tripping.  Overcurrent relay is adjusted according to the possible maximum load current.


Next, let's look at the overvoltage protection with compound voltage starting.

The overcurrent relay is still there, but there are two relays on the voltage side, one is the negative sequence overvoltage relay, the other is the low voltage relay.

Therefore, it can be said that this protection is an improved version of over-current protection with low voltage starting, with higher sensitivity in the case of asymmetrical faults and the same sensitivity in three-phase short circuit. There is no difference between the two kinds of protection in the location of application, but the difference in structure and performance.

In the book of Professor Zhang Baohui, we talked about the composite voltage starting overcurrent protection wiring, which is relatively simple and widely used. Although it is not easy to see in the logical diagram. It's just a relay.

This lock is okay, but there should be atresia in the two protection. In order to prevent breakage in the circuit of voltage transformer, if the line is broken, the low voltage relay will start. Therefore, in practice, a voltage circuit breaker should be added. I think all two protection need to be broken. Therefore, the usual address is directly called low voltage starting overcurrent protection and compound voltage starting overcurrent protection.


Author: the middle two studies electric

Link: https://www.zhihu.com/question/57578410/answer/153636992.

Source: knowing

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Add: No.38 South Taoyuan Road, Yaozhuang Town,Jiashan County, Jiaxing City, Zhejiang Province, China
Contact person: Elva Zhuang&Sunny Ni
Tel:+86-573-84775555
Fax:+86-573-84776699
Phone:+86-13732570078
E-mail:
sales9@great-relay.com
       sunny.ni@great-relay.com