ABB REG670 Applications Manual page 440

Section 10
Voltage protection
434
TVoltType: STEFPHIZ function is fed from a voltage transformer in the generator
neutral. TVoltType defines how the protection function is fed from voltage
transformers at the high voltage side of the generator. The setting alternatives are:
• NoVoltage is used when no voltage transformers are connected to the generator
terminals. In this case the protection will operate as a 3
protection.
• ResidualVoltage 3U0 is used if the protection is fed from an open delta connected
three-phase group of voltage transformers connected to the generator terminals.
This is the recommended alternative.
• AllThreePhases is used when the protection is fed from the three phase voltage
transformers. The third harmonic residual voltage is derived internally from the
phase voltages.
• PhaseL1, PhaseL2, PhaseL3, are used when there is only one phase voltage
transformer available at the generator terminals.
The setting Beta gives the proportion of the 3
of the generator to be used as restrain quantity. Beta must be set so that there is no risk
of trip during normal, non-faulted, operation of the generator. On the other hand, if
Beta is set high, this will limit the portion of the stator winding covered by the
protection. The default setting 3.0 will in most cases give acceptable sensitivity for
earth fault near to the neutral point of the stator winding. One possibility to assure best
performance is to make measurements during normal operation of the generator. The
protective function itself makes the required information available:
• rd
UT3, the 3 harmonic voltage at the generator terminal side
•
rd
UN3, the 3 harmonic voltage at the generator neutral side
• E3, the induced harmonic voltage
• ANGLE, the phase angle between voltage phasors UT3 and UN3
• DU3, the differential voltage between UT3 and UN3; (|UT3 + UN3|)
• BU3, the bias voltage (Beta x UN3)
For different operation points (P and Q) of the generator the differential voltage DU3
can be compared to the bias BU3, and a suitable factor Beta can be chosen to assure
security.
CBexists: CBexists is set to Yes if there is a generator breaker (between the generator
and the block transformer).
FactorCBopen: The setting FactorCBopen gives a constant to be multiplied to beta if
the generator circuit breaker is open, input CBCLOSED is not active and CBexists is
set to Yes .
UN3rdH<: The setting UN3rdH< gives the undervoltage operation level if TVoltType
is set to NoVoltage. In all other connection alternatives this setting is not active and
operation is instead based on comparison of the differential voltage DU3 with the bias
voltage BU3. The setting is given as % of the rated phase-to-earth voltage. The setting
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
1MRK 502 071-UEN -
rd
harmonic undervoltage
rd
harmonic voltage in the neutral point
Application manual