1

Name: Osamu TSUBOICountry: JapanRegistration No.:

Group: B5Pref. Subject: 1

Question: 7

Question 7

Non-harmonic-restraint schemes applied in Japan

2

Name: Osamu TSUBOICountry: JapanRegistration No.:

Group: B5Pref. Subject: 1

Question: 7

1. 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:

3

Name: Osamu TSUBOICountry: JapanRegistration No.:

Group: B5Pref. Subject: 1

Question: 7

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)

4

Name: Osamu TSUBOICountry: JapanRegistration No.:

Group: B5Pref. Subject: 1

Question: 7

Current remains balanced between windings of the parallel tank even during inrush

(for 1000kV transformer with parallel winding)

Parallel winding current-balance relay scheme

Serieswinding

Commonwinding

Tertiarywinding

61S

61T

61C

61: Current-balance relay

1000kV

500kV

154kV

5

Name: Osamu TSUBOICountry: JapanRegistration No.:

Group: B5Pref. Subject: 1

Question: 7

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)

Differentialrelay

Harmonicrestraint

Small drop intransformer

tertiary voltage

&

&

Trip

Trip-lockcondition