Controlled Switching — Buyer´s Guide
B-6
Edition 2, 2006-09
Explanations
Instrument Transformers (Sensors)
Voltage Transformers
and
Current Transformers
(VT’s and CT’s)
The reference signal should be a permanent supply side voltage (busbar
voltage). The reference voltage must be applied at least 300 ms prior to the
given switching command.
Any type of voltage transformer already existing in the system is suitable.
Power consumption is less than 0. VA.
When making instant and/or interrupting instant is monitored, a CT
secondary signal is required. Any CT already existing in the system is
suitable and no separate core is needed.
For the L83 and T83 load side voltage measurements are needed for
determination of the load conditions.
Transducers
Compensation
When the circuit breaker has a well-known variation in its behavior, with
variations in external conditions, corrections for these can be made.
The controllers F236, L83 and T83 each have two compensation
sensor inputs. An example of possible external conditions that can be
compensated for are operating time variations due to ambient temperature
changes and variations in auxiliary voltage for the circuit breaker coils.
Any external parameter variation giving a known dependency can be
compensated for by suitable sensors. The sensors are optional and are to
be ordered separately.
The compensation features are especially meaningful for circuit breakers
that are not switched frequently.
The signal from the transducer to the controller must be in the range 4 to
20 mA.
For circuit breakers frequently operated, the external parameter change
influencing circuit breaker behavior can be considered as minor and
compensated for by adaptation control.
Compensation equipment is mainly intended for circuit breakers that are
not frequently operated.
Precision Auxiliary
Contacts
If the instants for the contact touch or contact separation are being
monitored, ABB advises using special inductive auxiliary contacts (NAMCO
type I 605.A2 ID No. 724988).