ABB SYNCHROTACT® Accessories Adaptation and compensation voltage transformers (VTs)

When are adaptation or compensation VTs needed?

– If the two nominal measuring voltages are out of admissible

range (50 to 130 VAC).

– If the two nominal measuring voltages are different. With

the types SYN 5200 and SYN 5201. differences between

the nominal values up to 10 % can be tuned by parameter

setting. – If there is a step-up transformer between measuring VT and

circuit breaker, which shifts the phase by a fixed value, it

can be compensated with types SYN 5200 and SYN 5201.

With the types SYN 5100. SYN 5202. SYN 5302. or with

the use of electromechanical synchronizing instruments,

compensation VTs shall be used in order to compensate for

the phase shift.

If possible, the compensation should be done in a way

that a single phase compensation VT is required only

If there is a step-up transformer between measuring VT and

circuit breaker, the connection group is usually Yd1 (+30 DEG)

or Yd11 (-30 DEG).

With the appropriate selection of the phases, the phase shift

can be compensated without any additional components. In

this example the compensation of the amplitude by factor √3

remains. This can be done by a single phase compensation VT.

In order to achieve higher accuracy, especially if higher load

(synchronizing instruments) is connected, the compensation

should be carried out on the generator side.

If a three-phase compensation is inevitable, 3 single-phase VTs

have to be selected which will then be connected according

to the needs. Be aware that the single phase ratio has to

be calculated.