ABB 615 series Technical Manual page 650

Section 4
Protection functions
644
Voltage selection setting Phase supervision
setting
phase-to-phase B or BC
phase-to-phase C or CA
Pos sequence N/A
1) Voltages, currents and the leakage reactance X
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 (V
then by setting the leakage reactance value to zero the calculated induced
voltage (E) is equal to the measured voltage.
The calculated V/f ratio is scaled to a value based on the nominal V
highest allowed continuous voltage (in % V
Voltage Max Cont to change the basis of the voltage. The measured voltage is compared
to the new base value to obtain the excitation level.
The excitation level (M) can be calculated:
E
f
m
M
=
V Volt Max continuous
n
⋅
f 100
n
GUID-2712EB3B-0126-44B6-AABC-AA4BD2569FFB V1 EN
M excitation level (V/f ratio or volts/hertz) in pu
E internal induced voltage (emf)
f measured frequency
m
V nominal phase-to-phase voltage
n
f nominal frequency
n
Calculation of internal induced voltage (emf) E
(
E V ( I I
= + −
BC B C
GUID-AF78379A-78B9-466A-85E1-593333656FB8 V2 EN
E V ( ( I I
= + −
CA C A
GUID-90521B6F-C9B3-411F-82AD-E5AAF3D3ACEA V2 EN
(
E 3 V I (
= × + ×
1 1
GUID-E79E33FD-02FF-4E92-80A4-C7FEBB99C839 V2 EN
in the calculations are given in volts, amps and ohms.
leak
) is to be used in the excitation level calculation,
m
) can be defined by setting the parameter
n
1MAC059074-MB A
1)
)
) ( j X )
× ×
leak
) ( j X ) )
× ×
leak
)
j X )
×
leak
/f ratio. However, the
n n
(Equation 120)
615 series ANSI
Technical Manual