It is special relay characteristic for selective co-ordination. When closing ACB (changing from OFF to ON), the instantaneous tripping characteristic is effective, but after ACB closed, the instantaneous tripping characteristic becomes ineffective. Therefore, this instantaneous tripping characteristic control is useful for short-circuit fault protection when closing and to expand the selective coordination area with downstream circuit breaker. MCR function is provided in WS relay as option and in WB relay as standard. And instantaneous tripping or MCR is changeable by select switch.