TranSystems Corporation - LGM Construction

501070099 Federal Express Oakland Sort Expansion Issued for Bid 10/11
3. Potential transformers shall be supplied through current-limiting fuses.
2.8 CONTROL SYSTEMS
A. Control circuits: 120 volts, supplied through secondary disconnecting devices from control power transformer.
B. Control power sources for electrically operated circuit breakers: Control power transformers, with interlocking
relays, connected to the line side of each main circuit breaker. Provide 120 volt secondaries connected
through automatic transfer relays to ensure a fail-safe automatic transfer scheme that will prevent the two
power sources from being concurrently connected to the control system and from being connected together.
C. Control Power Fuses: Primary and secondary fuses for current-limiting and overload protection of transformer
and fuses for protection of control circuits.
D. Control Wiring: Factory-installed, with bundling, lacing, and protection included. Provide flexible conductors
for No. 8 AWG and smaller, for conductors across hinges, and for conductors for interconnections between
shipping units.
E. For each electrically operated circuit breaker, provide circuit breaker electrical trip lockout with amber LED
light indication.
F. For each electrically operated circuit breaker, provide LED opened and closed indicators.
G. Automatic Source Transfer Control System
1. The substation shall be provided with an automatic/manual control system that shall provide for control of
the two main circuit breakers and the tie circuit breaker in order to provide an open transition control
sequence for providing power through the switchboard in the event of a loss of either of the main power
sources. Interlocks shall be in place to ensure that under no circumstances can both main breakers and
the tie breaker be closed concurrently.
2. The automatic source transfer control system shall NOT require an uninterruptible power supply for proper
operation.
3. Provide an industrial grade type 27/47 relay to monitor each incoming power source on the line side of the
main circuit breaker.
a. 27/47 relay for undervoltage, phase reversal, single phase and phase voltage balance
b. Undervoltage sensing (device 27) on both sources shall be set at 88% of nominal voltage
(adjustable) with local LED indication.
c. Phase loss (device 47) set at 68% of nominal voltage (adjustable) with local LED indication.
d. Phase sequence (reverse phase) sensing (device 47) set at 2 cycles (adjustable) with local LED
indication.
e. Phase imbalance (device 47) set at 10% (adjustable) with local LED indication
4. Provide a key-operated test switch (located behind the exterior door) for simulating loss of voltage of
either source.
12 KV – 480/277V SECONDARY DOUBLE-ENDED UNIT SUBSTATIONS 16371-8