ABB REG670 Commissioning Manual page 91

1MRK 502 073-UUS A
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062
Commissioning manual
Calibrating injection based 100% stator earth fault protection
GUID-3C7F0567-2367-46E4-9606-FCFC7408DAA0 V1 EN-US
Figure 21: ICT calibration tab 1 including the stability region indicator bar
5. Connect a calibration resistance Rcal between the neutral point of the generator
and ground; the value of the calibration resistance can be selected on the basis of
the impedance to ground of the stator:
£ £ ×
Z R 2 Z
stat cal
IECEQUATION17022 V1 EN-US
The stator impedance to ground can be estimated by one of the below quantities:
• The total impedance to ground of the stator windings at the injection
frequency:
1
=
Z
stat
1
w
+
j C
R
N
IECEQUATION17023 V1 EN-US
where R is the primary grounding resistor
N
• The total impedance to ground of the stator windings at the injection
frequency taking into account the equivalent resistance R
grounding resistor transferred to the primary side of the grounding
transformer:
stat
stat
Section 7
Stability region
indicator bar
IEC11000047-1-en.vsd
,eq of the
N
85