Basler Electric BE1-51/27C - Manual (Page 63)

9137200998 Rev E 57
Figure 36. System Example
Downstream current in Table 4 is the current in the downstream relay with which the BE1-51/27C
elements must coordinate. The currents are the changes resulting from the fault assuming a driving point
voltage of 11 kV. Actual currents will be the sum of the table values plus the pre-fault load currents.
Transient level currents are based on use of the generator transient reactance. Steady-state level
currents are based on use of generator steady-state reactance and assuming no generator regulator
boost. Note that the table values apply for 3-phase faults. Transient level currents in generators for a
phase-to-phase fault will be about equal to the 3-phase current values. Steady-state level currents in the
generators will be higher for a phase-to-phase fault.
Table 4. Three-Phase Fault Currents
Level Out of Service Fault Loc.
Fault Current - A @ 11 kV
Downstream Generator
Transient T2 1 7256 776
Steady State T2 1 5961 129
Transient
―
2 7256 776
Transient T2 2 1552 776
Steady State T2 2 258 129
Transient
―
3 713 713
Steady State
―
3 127 127
Coordination with Feeder 51 Relay for Fault 1
(1) Multiples of pickup in 51 relay at transient level:
( ) 7.6
960
7256
6 800/5
7256
= =
BE1-51/27C Tests and Adjustments