Name: Osamu TSUBOI Country: Japan Registration No.: Group: B5 Pref. Subject: 1 Question: 7 1 Question 7 Non-harmonic-restraint schemes applied in Japan

Name: Osamu TSUBOI Country: Japan Registration No.: Group: B5 Pref. Subject: 1 Question: A non-harmonic-restraint scheme is selected according to the relay principle. 2.Fault current includes lower harmonic; such as 1000kV, cable transmission. Non-harmonic-restraint schemes applied in Japan Non-harmonic-restraint schemes are applied in the following cases:

Name: Osamu TSUBOI Country: Japan Registration No.: Group: B5 Pref. Subject: 1 Question: 7 3 Impedance locus scheme  For preventing unwanted operation of distance protection relay  In Japan, the distance protection is generally used for a transformer backup protection  Reactance X calculated by distance protection:  varies during inrush  almost fixed during fault (for distance protection)

Name: Osamu TSUBOI Country: Japan Registration No.: Group: B5 Pref. Subject: 1 Question: 7 4 Current remains balanced between windings of the parallel tank even during inrush (for 1000kV transformer with parallel winding) Parallel winding current-balance relay scheme Series winding Common winding Tertiary winding 61S 61T 61C 61: Current-balance relay 1000kV 500kV 154kV

Name: Osamu TSUBOI Country: Japan Registration No.: Group: B5 Pref. Subject: 1 Question: 7 5 Tertiary voltage restraint scheme  Drop in transformer tertiary voltage:  small during inrush  large during internal fault  For preventing unwanted trip-lock by the harmonic restraint (for network with lower harmonic) Differential relay Harmonic restraint Small drop in transformer tertiary voltage & & Trip Trip-lock condition