ABB REF542PLUS integrated protection relay
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.

The use of the already planned and tested synchronizing
system saves all engineering costs and inreases safety.
SYNCHROTACT® CSS only needs to be installed, connected
and commissioned.
The system uses the proven and reliable SYNCHROTACT® 5
components and can be built into a 19" frame.
To ensure high availability of the plant, SYNCHROTACT®
CSS consists of a fully automatic and independent manual
synchronizing unit.
Different versions are available, either for one or for two
circuit breakers, and both either in single- or dual-channel
configuration.
The PC software, SynView, which is included in the delivery,
provides quick and simple commissioning.
Functionality
SYNCHROTACT® CSS supports the following operating
modes, which can be selected by means of a switch.
– Operating mode AUTO: generator voltage and frequency
are automatically matched by the synchronizing equipment.
The circuit breaker will be closed subsequently and exactly
with phase-coincidence, taking the breaker closing time into
consideration.
– Operating mode MAN: the functions are carried out
manually by means of push buttons on the front panel.
The necessary values are displayed on the synchronizing
instruments. The paralleling command is issued by holding
down the release button and pushing the command button if
phase-coincidence is reached.
– Operating mode TEST: this is identical to the AUTO-mode,
except for the paralleling command which is not sent to
the circuit breaker but displayed by the system only.
With models for two circuit breakers the paralleling point has
to be selected by means of the appropriate selector switch
before the synchronizing process is started.
Releasing by means of a key switch, the circuit breaker can
be closed even if one or both measuring voltages are dead
(dead bus).
Changing the control mode selection from «local» to «remote»
allows the use of automatic synchronizing from a remote
location.