DET-882
SecoGear Medium-voltage Switchgear Application and Technical Guide
Control Power Equipment
©2017 General Electric All Rights Reserved
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Although battery system is more reliable, it requires
more maintenance than a capacitor system (remember
that a capacitor trip also contains a small rechargeable
battery system that requires periodic maintenance and
replacement)
•
For a little additional cost, DC closing power can be
obtained through the battery tripping system
•
A small UPS should be included to power AC control in
case of an emergency or power loss if no self-powered
microprocessor relays are used
• A small UPS should be included to power AC control in
case of an emergency or power loss if no self-powered
microprocessor relays are used.
DC Battery Trip
When properly maintained, a battery bank is the most
reliable tripping source. An added benefit is that it requires
no auxiliary tripping devices and uses single-contact
relays, which directly energize a single trip coil in the
breaker. Power circuit voltage and current conditions
during time of faults do not affect a battery-trip supply;
therefore, it is considered the best source for circuit
breaker tripping.
Once a battery bank has been selected for tripping
purposes, it can, after proper evaluation of additional loads,
also be used for breaker closing power. For indoor
applications where a battery bank can be located close to
the switchgear, a 48 V battery operating level is suitable.
For more general use, a 125 V battery system is
recommended. 250 V batteries can be used if other
conditions require that voltage.
Reliability and long service life of the batteries will be
possible only with proper maintenance, when kept fully
charged. For equipment in remote locations with difficult
access, where periodic maintenance is unlikely, the
capacitor trip device may be a better option.
NOTICE
On indoor (NEMA 1) applications, batteries are
typically not located within the switchgear structure.
SecoVac Autocharge Capacitor Trip Device
The GE/ITI Automatic Charging Capacitor Trip Device
(CTDB-6) is used to trip circuit breakers and lockout relays
when AC control power source is utilized. The CTDB-6
converts AC control bus voltage to DC voltage and stores
enough energy to operate a lockout relay or trip a circuit
breaker, often more than once.
The CTDB-6, with batteries fully charged, will maintain a
charge for a minimum of three days after the AC power
has been interrupted. In normal operation, the batteries are
trickle charged from the AC voltage source. The
Autocharge Capacitor trip device is provided on SecoVac
breakers whenever AC control voltage is specified. GE
offers for both 120 Vac and 240 Vac control power sources.
Direct Acting Undervoltage Trip Device
Most SecoVac circuit breakers can be provided with a
direct-acting undervoltage trip device. The undervoltage
trip device is a factory-installed unit, which is an integral
part of the breaker mechanism. Its function is to monitor
the DC trip control voltage and to mechanically trip the
breaker if that control voltage is lost. The UV device will
also block closing of the breaker if the control voltage is not
80% or more of the nominal value.
Breaker Closing
Closing power availability should also be independent of
voltage conditions on the power system associated with
the switchgear as the tripping. Accordingly, a DC battery
bank is normally considered to be the most reliable
auxiliary power source. Nevertheless, in many instances,
the battery bank or other independent power source
necessary to achieve this goal may require an investment,
which is considered too high for the advantages gained.
This is particularly true for small switchgear installations,
consisting of only a few circuit breakers.
NOTICE
When initially installing SecoGear, to energize the control
power equipment first establish the control power and
then rack in SecoVac circuit breakers one at a time. This
process will begin charging the closing spring of each
breaker one by one, instead of trying to charge them all
at once, preventing the risk of overloading the AC or DC
source.
Besides from the economic factor that would be the
primary decision to select AC or DC closing power, the
following situations must be taken into account:
•
Closing breakers with the power system de-energized
•
Availability of housing space for a battery and its
associated charging equipment
•
Estimated ambient temperature extremes and the
effect on battery capability
•
Maintenance requirements for a battery and battery
charger
•
Expected future equipment additions, which may affect
the present choice of closing-power source
When the closing mechanism is operated from AC, the
current required is such that it can be taken from a control
power transformer or a general purpose or lighting source,
internal or external to the switchgear. The energy for the
