ABB REL650 series, Applications Manual

Page: 74 / 516

3.1.9.2 Calculating settings for step 1
1. Set Pickup1 to 490 % of IBase
The calculations show the largest phase current I
max
= 3.84 kA
To assure selectivity the setting must fulfil:
I
high, set
≥ 1.2
⋅
k
⋅
I
max
where k is the transient overreach (due to fault current DC-component) of the
overcurrent function. For the four step overcurrent function in the IED k = 1.05.
This gives:
I
high, set
≥ 1.2
⋅
1.05
⋅
3 840 = 4 840 A
Setting: Pickup1= 490 % of IBase which corresponds to 4 900 A
2. Set t1 to 0 s
Faults are applied at points 1 and 2 (busbar faults at both line ends). The following
fault types are applied: 3-phase short circuit, phase-phase-ground short circuit and
phase-ground fault. For the faults at fault point 1 the source impedance at line end A
should be minimized (maximum short circuit power). For the faults at fault point 2
the source impedance at line end B should be minimized (maximum short circuit
power).
3.1.9.3 Calculating settings for step 2
1. Set Pickup2 to 190 % of IBase
To assure that step 2 will detect all short circuits on the line a phase-phase short
circuit is applied at point 1 (the adjacent busbar). The source impedance at line end
A should be maximized (minimum short circuit power) at this calculation. We get
the phase current
I
AB,min
= 2.50 kA (phase-to-phase short circuit).
To assure that step 2 will detect all short circuits on the local busbar a phase-phase
short circuit is applied at point 2 (the local busbar). The source impedance at line end
B should be maximized (minimum short circuit power) at this calculation. We get
the phase current
I
BA,min
= 2.50 kA (phase-to-phase short circuit).
If possible the delay of step 2 should be set equal to the distance protection zone 2
(normally 0.4 s). To assure selectivity with this time delay the function should not
overreach adjacent lines out from the remote busbar and out from the local busbar.
Section 3
1MRK 506 334-UUS A
REL650 setting examples
68
Application manual