THOMSON TS 870 - Standard ATS - Closed Transition

TS 870 Transfer Switch
PM062 REV 11 16/04/19 20 Thomson Power Systems
NOTE: A neutral delay timer circuit will delay the transfer sequence in the neutral
position (i.e. both power switching devices open) until the neutral delay time period
expires.
An engine cooldown timer circuit will be initiated once the load is transferred from the
generator supply. Following expiry of the cooldown delay period (adjustable from 0 to
60 minutes), the engine start signal will be removed (contact opening) to initiate
stopping of the generator set.
5.2. STANDARD ATS - CLOSED TRANSITION
NOTE: This section applies only to Closed Transition configured transfer switches.
For transfer switches equipped with the Closed Transition transfer option, the ATS is
configured to operate as follows:
Under normal closed transition operating conditions, the transfer switch operates
automatically during a failure and restoration of utility power and does not require
operator intervention.
When utility supply voltage drops below a preset nominal value (70 - 99% of rated
adjustable) on any phase, an engine start delay circuit will be initiated and the transfer
to utility supply signal will be removed (i.e. contact opening). Following expiry of the
engine start delay period (0 - 60 sec. adjustable) an engine start signal (contact closure)
will be given.
Once the engine starts, the transfer switch controller will monitor the generators voltage
and frequency levels. Once the generator voltage and frequency rises above preset
values (70 – 99% nominal adjustable) a warm up time delay will be initiated. Once the
warm up timer (0-60 Min adjustable) expires, the transfer to generator supply signal
(contact closure) will be given to the transfer switch mechanism. The load will then
transfer from the utility supply (i.e. opening the utility power switching device) to the
generator supply (closing the generator power switching device) via motor driven
mechanism to complete a “Break-before-make” open transition transfer sequence.
The generator will continue to supply the load until the utility supply has returned and
the retransfer sequence is completed as follows: When the utility supply voltage is
restored to above the present values (70 - 99% of rated adjustable) on all phases, a re-
transfer sequence will be initiated once the Utility Return timer expires. The utility will
close its power switching device when it is in synchronism with the generator supply
utilizing the TSC 900 in-phase detector. The generator power switching device will
immediately trip open approximately 50-100 milliseconds after the utility power
switching device closes to complete the make-before-break re-transfer sequence.
An engine cooldown timer circuit will be initiated once the load is transferred from the
generator supply. Following expiry of the cooldown delay period (0 - 60 min.