Siemens SDR 15.5 kV Instruction Manual page 14

14
Auxiliary power supply
The three-phase type SDR controller uses an
internal 48 V bus, which is backed-up by
rechargeable batteries as an uninterruptible
power supply. The internal bus is energized
by the power supply unit (PS1). It is
connected to the auxiliary power provided
on site, either through low-voltage supply or
power transformer connected to the high-
voltage line (optional). The charging of the
batteries is temperature compensated by
the power supply unit.
The incoming supply needs to be connected
to the terminals on terminal block X1.
The power supply unit (PS1) is protected by
the miniature circuit breaker CB1. CB1 also
protects the ground fault circuit interrupter
(GFCI) duplex outlet, which is supplied to
provide power to the user's laptop
computer.
The heaters are connected to the same
incoming supply and are protected by the
miniature circuit breaker CB2.
Rechargeable batteries
Four-12 V batteries are supplied with the
recloser. They are to be installed in series on
site (see Installation and commissioning on
page 18). The batteries are protected by the
miniature circuit breaker CB3. The batteries
ensure minimal stand-by operation for 48
hours at 20 °C from a fully charged initial
condition.
If miniature circuit breaker CB3 opens or
trips, it disconnects the control power for
the controller and the controller will neither
operate the recloser nor protect the
network. Control and protection functions
restart automatically by closing CB3.
If the batteries are not in use, they should
be recharged at intervals of six months.
Deep discharge protection (provided with
the Siemens type 7SR224 control and
protection relay)
The controller is equipped with deep
discharge protection to avoid damage to the
batteries if the auxiliary power supply is
absent for an extended time.
In case of loss of auxiliary supply, the
recloser will work as long as the internal bus
voltage remains above 39 V. If the internal
bus voltage goes below this limit, the
voltage at the control relay binary input
drops below the threshold level and a timer
will start. This will create an entry to the
event file and can be mapped to a general
alarm. After a customer-settable time
(default value is 30 minutes), the batteries
will be disconnected from the electronics.
The recloser is now completely inoperative
and will remain in the state (open or closed)
that it was in when the batteries were
disconnected.
With returning auxiliary supply power, the
controller will start-up and close the control
relay binary output contact to connect the
batteries to the power supply unit. The
power supply is restored and the recloser
returns to normal operation. The restoring
can be delayed up to 2 minutes, caused by
the reactivation of the power supply unit.
Until the restoration process is complete,
the recloser cannot be electrically switched
from one position (closed or open) to the
other.
Optional features
An optional power circuit supply can be
provided for additional communication
modules (radio unit or modem). It is directly
connected to the auxiliary power supply
through CB1 and not connected to the
uninterruptible power supply.
Additional BI/BO may be provided as an
option.