Calculating Settings For Step 2 - ABB Relion 650 Series Applications Manual

Section 3
RET650 setting examples
To assure that the protection detects all earth-faults on the 145 kV busbar the protection
should be set:
Setting:
IEC09000455 V1 EN-US
Figure 19: Fault calculation for 145 kV residual overcurrent protection selectivity
The calculations show the largest residual current from the transformer = 1.2 kA.
To assure selectivity the setting must fulfil:
I
high,set
which gives about 1 500 A ,where k is the transient overreach (due to fault current DC-
component) of the overcurrent function. For the four step phase overcurrent function; k =
1.05.
2. Set
Characteristic1 : ANSI Def.Time
As the protection should be set for a time delay of 0.4 s the selectivity to the line
protections should be assured. Therefore earth-faults should be calculated where the
fault point on the lines is at zone 1 reach (about 85 % out on the line).
3.1.8.3

Calculating settings for step 2

1. Set
To assure that step 2 detects all earth-faults on the outgoing lines earth-faults
calculations are made where single phase-faults and phase-to-phase-to earth-faults are
applied to the adjacent busbars.
IEC09000456 V1 EN-US
Figure 20: Fault calculation for sufficient reach of the 145 kV residual overcurrent
48
IN1> ≤ 0.75 · 2.2 = 1.65 kA
85%
≥ 1.2 · k · 3I
0 max
t1 to 0.4 s
IN2> to 400% of IBase , corresponding to 956 A
protection
© Copyright 2011 ABB Power Grids. All rights reserved
IN>
145kV
3
1
IN>
145kV
3
1
1MRK 504 124-UEN B
RET650
Ph-Ph
1 1
3
IEC09000455-1-en.vsd
GUID-057CA03F-C89E-4793-B8C5-1D49082A9B9F v2
RET650
Ph-Ph 1 1
3
IEC09000456-1-en.vsd
Transformer protection RET650
Application manual
22kV
22kV