ABB RELION REX640 Technical Manual page 519

1MRS759142 C
REX640
Technical Manual
UD Magnitude of the third harmonic differential voltage
3H
Ū Terminal side third harmonic voltage phasor
3H_T
Ū Neutral side third harmonic voltage phasor
3H_N
The magnitude of the third harmonic differential voltage UD_3H and the phase angle
difference between the terminal side and neutral side third harmonic voltage
U_3HANGL_T_N are available in the Monitored data view.
Bias calculation
The amplitude of the third harmonic bias voltage can be calculated using the following
equation.
UB Beta U
= ⋅ 3H_N
3 H
GUID-492EEC3D-EF54-480B-99DD-B67F29D23940 V1 EN
UB Magnitude of the third harmonic bias voltage
3H
Beta
Setting to achieve the required degree of security under healthy conditions
Ū Neutral side third harmonic voltage phasor
3H_N
The third harmonic bias voltage calculation shown in
operating conditions if there is no generator circuit breaker between generator and
transformer. But if the generator circuit breaker is used, it is needed to reduce the
sensitivity of the protection when it is open. The use of the generator circuit breaker
is defined by Generator CB used setting set to "Yes" and the open position is sensed
when the binary input GCB_CLOSED available is FALSE.
With the generator breaker in the open position, function desensitizes the protection
by multiplying the value of the Beta setting with the set constant CB open factor
setting.
UB CB open factor Beta
=
3H
GUID-3B550CE3-1B8B-4938-8D55-3B7BD584276D V1 EN
Neutral side third harmonic voltage is measured via a voltage transformer between the
generator neutral point and the earth. The magnitude of the third harmonic biased
voltage UB_3H is available in the Monitored data view.
Level detector
In the third harmonic differential method, Level detector compares the third harmonic
differential voltage with the third harmonic bias voltage. If the differential voltage
exceeds the biased voltage, the module sends an enabling signal to start the timer.
If the terminal voltage is not available, that is, Voltage selection is set to "No voltage"
the module compares the neutral side third harmonic voltage U_3H_N to the set
Voltage N 3.H Lim.
⋅ U
⋅
3 _ H N
Section 4
Protection functions
(Equation 69)
Equation 69 is valid under all
(Equation 70)
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