Calculating Settings For Step 4 - ABB REL650 Applications Manual

Section 3
REL650 setting examples
3.1.10.4
3.1.11
74
3I = 4 000 A and we get
0BC,step1
790
= ×
3 I 4000
, 0 sel
2980
GUID-F6D8356A-6802-4076-8240-0290B2C9C500 V1 EN
This calculation is made for fault out on each of the lines out from the remote busbar.
To assure both sufficient reach of step 2 and selectivity the setting of step 2 must be
chosen:
1.2 · max(3I ) ≤ IN
0,sel
1.2 · 1 060 ≤ IN
step2
Setting: Pickup2= 140 % of IBase which corresponds to 1400 A
2. Set t2 to 0.4 s

Calculating settings for step 4

The current setting of step 4 should be chosen according to standard procedure in the grid.
From experience it can be concluded that the setting down to about 100 A can be used. This
setting is however highly dependent on the line configuration, manly if the line is
transposed or not.
If definite time delay is used there is some risk of unselective trip at high resistive ground-
faults or series faults. If dependent time delay (inverse time) is used some degree of
selectivity can be achieved.
1. Set Pickup4 to 10 % of IBase which corresponds to 100 A
Characteristic 4: RD Type.
2. Set TD4 to 0.3
3. Set: t4Min to 1.2 s
Calculating settings for scheme communication for residual
overcurrent protection ECPSCH (85)
The communication logic is used to assure fast fault clearance for all ground-faults along
the line, that is also for faults outside the reach of step 1 of the four step residual
overcurrent protection. The logic for the communication schemes requires a
communication link between the four step residual overcurrent protections on the two line
ends. The communication link alternatives are:
=
1060 A
≤ 0.7 · 3I
step2 0ABmin
≤ 0.7 · 2 390 or 1 272 ≤ N
1MRK 506 334-UUS A
≤ 1 673
step2
Application manual
(Equation 25)