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Current transformers (CTs)

The type SDR vacuum recloser is equipped
with one integrated current transformer per
pole. The current transformer is the
conventional type (iron core magnetic) and
has a ratio of 800 A:1 A. It is for protection
purposes and optimized for operation with
the controller (see controller on page 11).
The secondary signal is based on IEC 60044-1
and the IEC accuracy is 0.5 VA 5P20.

The secondary wires of the CT are connected
to a varistor for each pole in the switch unit.
This prevents the occurrence of high voltages
(due to open-circuit CT secondary) if the
control cable is removed while the switch unit
is in operation. Do not disable the varistor
circuit. The signal transfer from the CTs to the
controller is by the control cable. A separate
cable is not required.

Voltage sensor (optional)

The SDR vacuum recloser can be equipped
with integrated resistive voltage sensors
(optional). The integrated resistive voltage
sensors have a high level of accuracy and are
used both for measurement and protection
purposes. The ratio is adapted to operation
with the controller (see controller on page
11) and provides a 110 V/√3 secondary signal
with rated primary voltage applied to the
recloser.

The voltage sensor and CT outputs are
coordinated with Siemens controllers. If a
non-Siemens controller is used, it is the
controller vendor’s obligation to properly
coordinate their controller with the voltage
sensors and CTs provided in the type SDR
distribution vacuum recloser.

An optional separate sensor cable equipped
with special screening (shield) is used for the
signal transfer from the voltage sensors to the
controller. This results in a high level of
accuracy and protection against disturbances.
The sensor cable is connected at the back of
the operating mechanism housing next to the
control cable.

The secondary wires of the voltage sensors
are connected to a varistor for each pole in
the switch unit. This prevents the occurrence
of high voltage on the sensor cable if the
sensor cable is removed while the switch unit
is in operation. Do not disable the varistor
circuit.

Operating mechanism

The operating mechanism for each of the
three vacuum interrupters is located in a
separate metal housing. To meet the required
fast reclosing cycles, a magnetic actuator with
capacitors as energy storage drives the switch
units.

Each operating mechanism is equipped with
an anti-condensation space heater. It is
operated together with the heating in the
controller and controlled by a thermostat.

A mechanical position indicator is easily
visible from the ground and shows the
current switch position of each recloser (open
= green, closed = red). The colored display is
reflective in the dark when using a flashlight.

Lockout handle

A lockout handle with ring protrudes from
each of the three operating mechanism
housings. The rings are colored bright yellow
and are therefore easily seen.

By pulling any of the three lockout handles,
the selected phase of the recloser opens and
remains locked in this position. The locking
has a dual electrical effect; it locks out both
the controller and the electronics. It also
mechanically locks the magnetic actuator for
that phase.

As long as the lockout handle is pulled out, it
is not possible to close the switch unit for that
phase electrically, whether locally or from a
remote location. The interlocking is not reset
until the lockout handle has been completely
pushed in. After this, the switch unit for that
phase can be closed electrically, either locally
or remotely.

The switching is described in the Operation
section of this instruction manual (see page
22).

Note: Each lockout handle must be fully
pushed in or the interlocking will prevent
closing of the affected recloser.

Recloser

position

Color of

position

indicator

Closed

Red

Open

Green

Table 1: Recloser position and
indicator color