ABB REG650 Technical Manual page 257

1MRK 502 034-UEN -
Technical Manual
+ ³
U U Beta U
3T 3N
3N
EQUATION1712 V2 EN
U , and U are third harmonic phasors with real and imaginary parts. The factor
3N 3T
Beta must be set not to risk operation under non-faulted conditions.
The voltage U is measured via a voltage transformer between the generator
3N
neutral point and earth. The voltage U
setting TVoltType defines how the protection function is fed from voltage
transformers at the high voltage side of the generator. (If U
level UT3BlkLevel, STEFPHIZ function is blocked. The choices of TVoltType are:
NoVoltage: There is no voltage measured from the generator terminal side. This
can be the case when there are only phase-to-phase voltage transformers available
at the generator terminal side. In this case the protection will operate as a simple
rd
neutral point 3 harmonic undervoltage protection, which must be blocked
externally during generator start-up and shut-down.
ResidualVoltage: The function is fed from an open delta connection of the phase to
earth connected voltage transformers at the generator terminal side,
U =(1/3)*U_Open_Delta.
3T
AllThreePhases: The function is fed from the three phase to earth connected
voltage transformers at the generator terminal side. The 3
is calculated in the IED, U
PhaseL1, PhaseL2, or PhaseL3: The function is fed from one phase voltage
transformer only. The 3
to any of the phase voltages, as the third harmonic voltage is of zero sequence type,
U =U3Lx.
3T
A simplified block diagram describing the stator earth fault protection function
shown in figure 128.
can be measured in different ways. The
3T
=(1/3)*(U3L1+U3L2+U3L3).
3T
rd
harmonic zero sequence voltage is assumed to be equal
Section 8
Voltage protection
(Equation 85)
is lower than the set
3T
rd
harmonic voltage U
3T
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