Calculating Settings For Step 1 - ABB REC650 Applications Manual

Section 3
REC650 setting examples
3.1.6.2
52
1. Set GlobalBaseSel to 1, IBase = 240 A
2. Set DirModeSel1, DirModeSel2 and DirModeSel4 to Non-directional
3. Set DirModeSel3 to Disabled

Calculating settings for step 1

Set the operating residual current level and time delay
1. Set Pickup1 to 689% of IBase, corresponding to 1650 A
Faults are applied at the 145 kV busbar as shown in figure 10.
ANSI11000126 V1 EN
Figure 10: Fault calculation for 145 kV residual overcurrent protection setting
The following fault types are applied: phase-phase-ground short circuit and phase-
ground-fault. The source impedance (both positive sequence and zero sequence) at
the 145 kV level gives the following residual current from the transformer during a
phase-to-ground busbar fault (the current is hand-calculated but is normally
calculated in a computer).
The zero sequence transformer impedance is assumed to be equal to the positive
sequence short circuit impedance:
2
V 145
N
= × =
Z j e j
0 T k
S 60
N
GUID-50CCC0F7-742D-45C4-84BC-923222214C69-ANSI V1 EN
The residual current from the transformer during a single phase-ground-fault and
with maximum short circuit power is:
51N_67N
145 kV
3
2
× = W
0.12 j 42
1MRK 511 286-UUS A
REC650
1
Ph-Ph
1
Y
Y
3
1
Y
ANSI11000126-1-en.vsd
(Equation 13)
Application manual
22 kV