9 THEORY OF OPERATION
Single pole operations make use of many features of the relay. At the minimum, the trip output, recloser, breaker control,
open pole detector, and phase selector must be fully programmed and in service; and either protection elements or digital
inputs representing fault detection must be available for successful operation. When single pole trip-and-reclose is required
overall control within the relay is performed by the trip output element. This element includes interfaces with pilot aided
schemes, the line pickup, breaker control, and breaker failure elements.
Single pole operations are based on use of the phase selector to identify the type of the fault, to eliminate incorrect fault
identification that can be made by distance elements in some circumstances and to provide trip initiation from elements that
are not capable of any fault type identification, such as high-set negative-sequence directional overcurrent element. The
scheme is also designed to make use of the advantages provided by communications channels with multiple-bit capacities
for fault identification.
AR FORCE 3-P
The trip output element receives requests for single and three pole trips and three pole reclose initiation, which it then pro-
cesses to generate outputs that are used to:
Determine whether a single or three pole operation should be performed.
Initiate tripping of breaker poles A, B and C, either individually or as a group.
Initiate breaker failure protection for phases A, B and C, either individually or as a group.
Notify the open pole detector when a single pole operation is imminent.
Initiate either single or three pole reclosing.
Block specific protection elements
A or B or C
AR Initiate 3-Pole
Figure 9–28: SINGLE-POLE OPERATION
L60 Line Phase Comparison System
9.2 SINGLE-POLE TRIPPING
1 and 2
1 and 2