1. MR type R switch 4 resistors

2. Example Canada 3.4 and 6 Ohms Phase shifting transformer 840 MVA 240kV

4. MCa - Main contact (copper) opening

6. First region MSCa - Main switching contact opens

7. Adding resistance – current drops

8. Second region – subtracting turns TCa2 - Transition contact closes Connecting onto the contact at “potential” and lower resistance

9. UP

10. Second region – adding turns Connecting onto the contact with potential at lower resistance

11. DOWN

12. Third region

13. Fourth

14. Fifth

15. Recovery

16. Main contact = b

18. Influence of L More or less turns Phase shifter

19. More turns

20. Less turns 4 th segment influenced

21. OLTC problem ? 890MVA 500kV/25kV Malaysia

22. Nameplate 2 type R OLTCs in parallel

23. Type R – two resistors sequence

24. Nameplate Double tap changer windings in parallel Y connected Fine-coarse regulation

25. Double time on ODD transitions Transition 100mSec

26. Good time on EVEN transitions Transition 40mSec

27. Complete test – up and down

28. Is it because two parallel windings and two parallel OLTCS tested at the same time?