ABB RELION 620 Series Technical Manual page 303

1MAC504801-IB E
620 series ANSI
Technical Manual
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Figure 135: Functional module diagram
V/f calculation
This module calculates the V/f ratio, that is, the excitation level from the internal induced
voltage (E) and frequency. The actual measured voltage (V
induced voltage (emf) E, a value the equipment has to withstand. This voltage
compensation is based on the load current (I
equipment. The leakage reactance of the transformer or generator is set through the
Leakage React setting in percentage of the Z base.
The internal induced voltage (E) is calculated from the measured voltage. The settings
Voltage selection and Phase supervision determine which voltages and currents are to be
used. If the Voltage selection setting is set to "phase-to-ground" or "phase-to-phase", the
Phase supervision setting is used for determining which phases or phase-to-phase
voltages ("A or AB", "B or BC" and "C or CA") and currents are to be used for the
calculation of the induced voltage.
Table 249: Voltages and currents used for induced voltage (emf) E calculation
Voltage selection setting Phase supervision
setting
phase-to-ground A or AB
phase-to-ground B or BC
phase-to-ground C or CA
phase-to-phase A or AB
Table continues on next page
Protection functions
) deviates from the internal
m
) and the leakage reactance (X
L
Calculation of internal induced voltage (emf) E
(
E 3 V I ( j X
= × + × ×
A A
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(
E 3 V I ( j X
= × + × ×
B B
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(
E V I j X
3 (
= × + × ×
C C
GUID-8B274F07-54A0-4CEC-9AAC-618F742D9EED V2 EN
(
E V ( I I ) ( j X
= + − × ×
AB A B
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Section 4
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