Single-Pole Tripping Applications - GE L60 Instruction Manual

CHAPTER 8: APPLICATION OF SETTINGS DISTANCE/BACKUP SUPERVISION

8.2.8 Single-pole tripping applications

The L60 provides functionality for single-pole tripping from 87PC, distance functions, or instantaneous overcurrent
elements via the trip output element. 87PC can detect internal faults on the line but not faulted phases, since the phase
currents are combined in one quantity. Faulted phases are detected by the phase selector, which signals to the trip output
element the type of fault present to correctly trip.
Once the trip output produces a single-pole trip, the open pole condition is set a half cycle later, even if the pole is not yet
physically open and 87PC is not reset, as the fault is not interrupted by the breaker. Therefore, mapping the 87PC function
directly to the trip output always causes a three-pole trip. To avoid this, simple logic (see example shown) must be
implemented and mapped to the Input. The virtual output operates when single-pole
TRIP 1-POLE 87PC TRIPOUT (VO45)
tripping occurs and is mapped to the Input. To avoid forcing a three-pole trip, virtual output 45 is reset shortly
TRIP 1-POLE
after the single-pole trip operation.
Figure 8-7: Single-pole tripping with 87PC FlexLogic example
To provide tripping for evolving faults during open pole conditions, the output is provided and mapped
87PC TRIPEVL (VO46)
into three-pole trip input of the trip output function. Once the breaker pole opens and the fault is interrupted, 87PC is reset
and ready for the next operation 50 ms later (this time is dictated by the setting plus a 1 to 1.5 cycle security
87PC RESET
margin). Depending on the load current, FDL, and FDH settings, the relay can be exchanging with squares. However, this
appears as through-current and no 87PC operation occurs. However, if a fault occurs during the open pole condition, then
87PC operates again and requests the trip output element to trip the remaining two phases.
Figure 8-8: Trip output with 87PC setup example
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L60 LINE PHASE COMPARISON SYSTEM – INSTRUCTION MANUAL 8-9