THOMSON TS 870, Installation, Operating & Service Manual

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TS 870 Transfer Switch
PM062 REV 11 16/04/19 22 Thomson Power Systems

CLOSED TRANSITION: When both sources of supply are available,
the transfer switch will operate in a “make-before-break” closed
transition sequence during load transfers.
NOTE: If only one source of supply is available during an initiated transfer
sequence, the control system will automatically revert to an open transition transfer
sequence.
2. Synchronizing Protection: To ensure both sources are in synchronism prior to
initiating a closed transition transfer sequence, a TSC 900 in-phase monitor is used.
The GHC has a Sync page to allow monitoring of phase and voltage of the 2
sources. The in-phase relay will block a closed transition transfer sequence until
both sources phase angle and voltages are within programmed limits. The synch
check relay settings are field programmable (+-5 to 20 Deg Phase Angle (

ω
) and
1-10% voltage difference (

U) and they are factory set as follows:
NOTE: The standard closed transition transfer switch does not contain an
automatic synchronizer to control the generators frequency or voltage to bring it
within limits of the sync check relay. For correct closed transition transfer operation,
the system requires the generators frequency to be set within 0.25% of nominal
frequency and the generators voltage to be set within 0.5% of nominal voltage.
3. Closed Transition Time Period: The time period in which both sources of supply are
paralleled together during the closed transition transfer sequence is 50-100
milliseconds (maximum). The time period is inherently controlled by operation of
auxiliary contacts from the power switching devices (i.e. when one switching
devices closes, its aux contact closes to initiate tripping of the opposite switching
device).
4. Closed Transition Failure Mode Operation: The TSC 900 continually monitors the
closed transition operation time period. The TSC 900 is factory set for 100
milliseconds that allows normal closed transition operation (i.e. both power
switching devices remain closed for less than 100 milliseconds). The alarm circuit
is not activated under normal operation. Should the closed transition operation time
exceed 100 milliseconds (i.e. both power switching devices remain closed for
longer than the normal closed transition time period plus the setting of TSC 900
timer, the following sequence of events will occur:
•
TSC 900 time delay period will expire and will activate auxiliary trip relay.