ABB RELION REX640 Technical Manual page 887

1MRS759142 F
Table 842: Voltages and currents used for induced voltage (emf) E calculation
Voltage selection
setting
phase-to-earth
phase-to-earth
phase-to-earth
phase-to-phase
phase-to-phase
phase-to-phase
Pos sequence
The calculated U/f ratio is scaled to a value based on the nominal U
However, the highest allowed continuous voltage (in % U
setting the parameter
measured voltage is compared to the new base value to obtain the excitation level.
1
Voltages, currents and the leakage reactance X
ohms.
REX640
Technical Manual
Phase
supervision
setting
A or AB
B or BC
C or CA
A or AB
B or BC
C or CA
N/A
If all three phase or phase-to-phase voltages and phase currents
are fed to the protection relay, the positive-sequence alternative is
recommended.
If the leakage reactance of the protected equipment is unknown or if the
measured voltage (U
m
then by setting the leakage reactance value to zero the calculated
induced voltage (E) is equal to the measured voltage.
Voltage Max Cont to change the basis of the voltage. The
Calculation of internal induced voltage (emf) E
(
E = ⋅ U + I ⋅ j X ⋅
3 (
A A leak
(
E = 3 ⋅ U + I ⋅ ( j X ⋅
B B leak
(
E U I j X
= 3 ⋅ + ⋅ ( ⋅
C C leak
(
E U = + ( I − I ) ( ⋅ j X
AB A B
(
E U I I j X
= + ( − ) ( ⋅
BC B C
(
E U = + ( I − I ) ( ⋅ j X
CA C A
(
E = 3 ⋅ U + I ⋅ ( j X ⋅
1 1 leak
) is to be used in the excitation level calculation,
in the calculations are given in volts, amps and
leak
Protection functions
1
)
)
(Equation 240)
)
)
(Equation 241)
)
)
(Equation 242)
)
⋅ )
leak
(Equation 243)
)
⋅ )
leak
(Equation 244)
)
⋅ )
leak
(Equation 245)
)
)
(Equation 246)
/f ratio.
n n
) can be defined by
n
887