Table. 5.2.1 - 7. Initial data.
Machine nominal power: 153 MVA
Machine high voltage side nominal amplitude: 132 kV
Machine low voltage side nominal amplitude: 15 kV
Hig
High v
h volta
oltage side C
ge side CTT
- CT primary: 800 A
- CT secondary: 2 A
Hig
High-v
h-volta
oltage side nominal curr
ge side nominal current
ent
669 A
R
Resid
esidual curr
ual current C
ent CTT in Input I02
in Input I02
- 3I0CT primary: 250 A
- 3I0CT secondary: 1 A
LLoow v
w volta
oltage side C
ge side CTT
- CT primary: 8000 A
- CT secondary: 5 A
LLoow
w-v
-volta
oltage side
ge side nominal curr
nominal current
ent
5 888 A
- both CTs are pointing towards the protected object (HV-S2 and LV-S2 are pointing at each other)
The nominal currents on both the HV and the LV sides are the same as in Application 1. However, the
CTs' secondary current levels have been changed to 2 A (on the HV side) and to 5 A (on the LV side).
The nominal currents are still calculated the same way:
The HV and LV side nominal current can also be calculated in per unit values as follows:
The secondary nominal current (in amperes) is the result of multiplying the per unit value with the
phase CT secondary side current. This current can be used when the unit is commissioned and when
the directions of CTs are checked. In Application 2 it is necessary to inject higher amplitudes to the CTs
via the secondary injection tool in order to reach the nominal currents. See the example calculation
below:
A
AQ
Q-M257
-M257
Instruction manual
Version: 2.07
26
© Arcteq Relays Ltd
IM00021
Summary of Contents for AQ-M257
Page 1: ...AQ M257 Motor protection IED Instruction manual...
Page 2: ......
