MR type R switch

4 resistors

Example Canada 3.4 and 6 Ohms

Phase shifting transformer 840 MVA 240kV

MCa - Main contact (copper) opening

First regionMSCa - Main switching contact opens

Adding resistance – current drops

Second region – subtracting turns

TCa2 - Transition contact closes

Connecting onto the contact at “potential” and lower resistance

UP

Second region – adding turns

Connecting onto the contact with potential at lower resistance

DOWN

Third region

Fourth

Fifth

Recovery

Main contact = b

Influence of L

More or less turns

Phase shifter

More turns

Less turns

4th segment influenced

OLTC problem ?

890MVA 500kV/25kV

Malaysia

Nameplate2 type R OLTCs in parallel

Type R – two resistors sequence

Nameplate

Double tap changer windings in parallelY connected

Fine-coarse regulation

Double time on ODD transitions

Transition 100mSec

Good time on EVEN transitions

Transition 40mSec

Complete test – up and down

Is it because two parallel windings and two parallel OLTCS

tested at the same time?