Single/Triple Autoreclose; System Arrangement For Application Of Single/Triple Autoreclose - Siemens 7SR224 Technical Manual

7SR224 Argus Applications
4.4

Single/Triple Autoreclose

4.4.1

System Arrangement for Application of Single/Triple AutoReclose

In countries, such as the USA, where the distribution network is 4 wire i.e. three phase plus neutral, a three phase
feeder may run out from a sub/station and then at some point be split into three separate single phase plus
neutral feeders where, for example, each line can go up a separate valley and thus be subjected separately to
lightning strikes or single phase to Earth (Ground) or Neutral, Faults. Loads can thus be entirely single pole or a
mix of three pole and single pole.
Some utilities are upgrading their systems to improve the quality of supply to customers by installing three
separate single pole Reclosers plus a Controller that can selectively apply Single or Triple AutoReclose
sequences to each pole asynchronously. Each pole has its own separate fault detection/Trip and AutoReclose
sequencing capability. Different modes of operation can be set by the user to cater for the basic and or seasonal
requirements of different types of load on the three phases. The Controller provides settings to enable the user to
set the required options of Single/Triple Trip/Close and Single/Triple Lockout combinations including the option of
what must happen under two-pole faults. Before setting the controller to Single pole Trip/Single pole Lockout
mode the user must ensure that no plant is connected for which a three phase supply is essential e.g. three
phase motor. A typical application is feeders supplying Oil Rig pumping motors, single pole ARC can be
beneficially applied provided the motor is not run on two poles for extended periods otherwise NPS induced
overheating and failure could result, the Single pole Trip - Three pole Lockout, Mode B, provides for this by
allowing single pole trips followed by reclose but issues only three pole trips when a reclose is not started. An
additional subsequent three pole trip is issued in this Mode if single pole autoreclose fails.
If Single pole Trip is set then each Recloser can each be independently Tripped and Closed as a single pole
circuit breaker, however, in some circumstances all three Reclosers must be Tripped and Closed as a three pole
device. Each Single pole Recloser, therefore, has its own independent Trip/Close circuits and CB Open/Closed
Auxiliary contacts; also, its own Manual Trip & Lockout handle, with auxiliary T&LO contacts, operated by a Hot-
Line working tool. The Control Cubicle must have pole by pole external push button switches to provide local
electrical Trip/Close controls for each Recloser. The Controller provides pole by pole logic and interlocking to
ensure that correct operation occurs in all modes and for all complex fault conditions. Three instances of the
Capacitor Monitor/Test element are included to allow for the additional capacitor networks required by the phase
segregated system.
Figure 4.4-1 System Diagram showing application of Single/Triple pole Reclosers.
Single pole tripping is not normally applied where three-phase loads, or delta connected loads are connected. It is
only applied to Reclosers on systems which allow Single pole to Neutral load connection, e.g. 4 wire, 3Phase +
Neutral, systems, as typically used in the USA and South America. In such systems the routing and loading cab
be such that loads can tolerate running for short periods on only two phases, the third being temporarily dead. As
a simplified model consider that pole A is routed up valley A, Pole B is routed up valley B and pole C is routed up
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