ABB Relion 650 Series Technical Manual page 176

Section 6
Current protection
6.6.2 Functionality
The four step residual overcurrent protection (EF4PTOC, 51N/67N) has independent inverse time
delay settings for step 1 and 4. Step 2 and 3 are always definite time delayed.
All IEC and ANSI inverse time characteristics are available.
The directional function includes 3 options
• voltage polarized
• current polarized
• dual polarized
EF4PTOC (51N/67N) can be set directional or non-directional independently for each of the steps.
Second harmonic blocking can be set individually for each step.
EF4PTOC (51N/67N) can be used as main protection for phase-to-ground faults.
EF4PTOC (51N/67N) can also be used to provide a system back-up for example, in the case of the
primary protection being out of service due to communication or voltage transformer circuit
failure.
Directional operation can be combined together with corresponding communication logic in
permissive or blocking teleprotection scheme. Current reversal and weak-end infeed functionality
are available as well.
6.6.3 Function block
EF4PTOC (51N_67N)
I3P*
V3P*
I3PPOL*
BLOCK
BLK1
BLK2
BLK3
BLK4
ANSI08000004 V1 EN-US
Figure 91: EF4PTOC (51N/67N) function block
170
TRIP
TRST1
TRST2
TRST3
TRST4
BFI_3P
PUST1
PUST2
PUST3
PUST4
PUFW
PUREV
2NDHARMD
ANSI08000004-1-en.vsd
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