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Issue:
Having two different values for RL ( Lead resistance from the CT to the relay); RL from the phase CT to the relay and RL from the neutral point CT to the relay
Environment:
Protection Function ANSI 64ref
High impedance differential
Sepam 80 Current Transformer requirement
Resolution:
In any application where the high impedance differential is used, all the CTs must have the following:
- the same ratio,
- the same magnetizing curve (same minimum Vk),
- the same maximum Rct (current Transformer secondary winding resistance),
- if the relevant CTs are not at the same distance from the relay, take the maximum RL.
Attached Cahier Technique no.194 for more information about high impedance calculation
Having two different values for RL ( Lead resistance from the CT to the relay); RL from the phase CT to the relay and RL from the neutral point CT to the relay
Environment:
Protection Function ANSI 64ref
High impedance differential
Sepam 80 Current Transformer requirement
Resolution:
In any application where the high impedance differential is used, all the CTs must have the following:
- the same ratio,
- the same magnetizing curve (same minimum Vk),
- the same maximum Rct (current Transformer secondary winding resistance),
- if the relevant CTs are not at the same distance from the relay, take the maximum RL.
Attached Cahier Technique no.194 for more information about high impedance calculation
Released for:Schneider Electric Egypt and North East Africa
