D
Diff
iffer
erential curr
ential current sour
ent sources (
ces (normal opera
normal operation)
tion)
When calculating the differential current in a basic situation, it is strongly recommended to consider the
following transformer component errors (the illustrated parts in the image below).
Figure. 5.3.10 - 62. Differential current sources (normal operation).
There seven (7) differential current sources for normal operation:
1) Primary side CT measurement accuracy (CTE
pri
)
In this example the primary side CTs are Class 10P, which means the measurement error is 10 %.
2) Secondary side CT measurement accuracy (CTE
sec
)
In this example the secondary side CTs are Class 5P, which means the measurement error is 5 %.
3) Relay measurement accuracy (primary and secondary) (RE
m
)
The relay measurement error is below 0.5 %, its optional accuracy below 0.2 % per measurement
channel: the combined value for both sides is either 1 % or 0.4 %.
A
AQ
Q-T256
-T256
Instruction manual
Version: 2.06
114
© Arcteq Relays Ltd
IM00028
Summary of Contents for AQ-T256
Page 1: ...AQ T256 Transformer protection IED Instruction manual...
Page 2: ......
