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nguyen xuan khanh
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Joined: 16 May 2012
Posts: 170
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 Posted: 05/11/2015 20:03 Post subject: Help: Ground fault current and Earth leakage current |
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I'm working with Earth Leakage Relay (using Zero Current Transformer) and Ground Fault Relay ( using Potential Current Transformer) but i see the trip current setting of Earth Leakage Relay is small ( My company is 2 A) but trip current setting of Ground Fault Relay is very big ( 1600 A) equal to the rated current of ACB (1600A). My company using 3 phase 4 wire and neutral wire is connected to ground.
In my opinion,
suppose:
3 phase: A, B, C.
Neutral line: N
The formula of leakage current is ( using Zero Current Transformer) : vector_i_leak = vector_i_A + vector_i_B + vector_i_C + vector_i_C + vector_i_N
and
the formula of ground fault current is (using Potential Current Transformer):
vector_i_groundfault = vector_i_A + vector_i_B + vector_i_C
as you can see they are nearly the same.
may i'm wrong.
i don't understand why trip current setting of Earth Leakage Relay is small but trip current setting of Ground Fault Relay is very big.
can you help me ? |
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