Abstract:In order to confirm whether the underexcitation limitation protection value coordinates with the field failure protection value, both of the values should be checked for power plant. Due to the principle of underexcitation limitation protection is different from that of field failure protection, the values must be normalized to the same plane to be compared. This paper introduced the method of converting impedance circle of field failure protection to power circle, which is verified to be correct by practical calculation and test.

Keywords:under excitation limitation, field failure protection, coordination calculation, impedance circle, power circle