Field breaker
Two
alternative
measurement
points
for the stator
overload
function
Step-up
transformer
Excitation
transformer
ANSI12000012-2-en.vsd
HV- side
Neutral side
I
A
I
B
I
C
ANSI12000012 V2 EN-US
Figure 311: Measurement of stator current
The selection of current measurement is done by using the parameter
MeasurCurrent::
•
When
MeasurCurrent = RMS (default); the maximum true RMS current value from the three-
phase input currents is used as the measured quantity for the stator overload protection.
•
When
MeasurCurrent = PosSeqNegSeq; the weighted sum of positive and negative sequence
stator currents in primary amperes is used as the measured quantity for the stator overload
protection. This current value is calculated from the connected three-phase input currents,
see Figure
#GUID-93C398EE-7AB7-400A-A357-0CDD9BBDFA33/GUID-877000D4-9090-4709-
B754-6B9EE0F09FA6
.
The weighted sum of positive and negative sequence stator currents is calculated as per the
following equation.
2
2
1
2
PosSeqFactor
NegSeqFactor
I
I
I
=
×
+
×
GUID-8768BBBF-3EF7-4D4A-9FF6-DF4A07272812 V1 EN-US
(Equation 163)
Where:
I is current value in primary amperes used by the overload function
I
1
is stator positive sequence current in primary amperes
I
2
is stator negative sequence current in primary amperes
PosSeqFactor is a setting factor to multiply the positive sequence current and its default value is 1.0
NegSeqFactor is a setting factor to multiply the negative sequence current and its default value is 6.0
1MRK 502 066-UUS B
Section 8
Current protection
581
Technical manual
Summary of Contents for Relion 670 series
Page 1: ... RELION 670 SERIES Generator protection REG670 Version 2 1 ANSI Technical manual ...
Page 2: ......
Page 48: ...42 ...
Page 62: ...56 ...
Page 182: ...176 ...
Page 692: ...686 ...
Page 726: ...720 ...
Page 1014: ...1008 ...
Page 1242: ...1236 ...
Page 1362: ...1356 ...
Page 1386: ...1380 ...
Page 1422: ...1416 ...
Page 1431: ...1425 ...