What is the principle of domestic medium and low voltage panel busbar protection?
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Author:hkwa49fa3
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Published time: 2019-07-01
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1) Transformer backup overcurrent protection scheme
At present, the most widely used medium and low voltage busbar protection schemes, the protection tripping is generally set to 1.2-2.0s, which obviously cannot meet the requirements of rapid removal of medium voltage busbar faults.
2) Feeder overcurrent component blocking incoming line overcurrent protection scheme
In recent years, the medium and low voltage busbar protection schemes realized by the overcurrent protection of microcomputers proposed by foreign countries. The protection action time is 300-400ms, and it still cannot meet the requirement of quickly cutting off the arc short circuit fault within 75ms.
3) High-impedance bus protection scheme using the principle of circulation
The special medium voltage busbar protection scheme adopted by some important foreign projects has a protection action time of 35-60ms. This kind of scheme has complicated wiring and high requirements for CT. It is difficult to install on the 6-35KV bus. In addition, this type of protection cannot be protected from faults at cable joints where the probability of failure is high due to the limited installation position of the CT, and it cannot provide fault location. Therefore, it is not suitable for medium voltage busbar protection applications.
The existing protection scheme obviously cannot meet the requirements of rapid resection fault or protection coverage. It is urgent to adopt a new type of medium and low voltage busbar protection system to solve the problem that the medium and low voltage busbars have a high probability of failure and delay resection faults lead to fault development. The problem of expanding, resulting in huge economic losses.
