ABB RELION Series, Technical Manual

Page: 765 / 804

necessary for overcurrent protection to operate already starting from as low frequency
as 2 Hz during the generator start-up or shutdown phase. The wide peak-to-peak
measurement principle is selected with the
Measurement mode setting "Wide P-to-P".
The measurement mode calculates the average from the positive and negative peak
values over the 500 ms wide measurement window, independently of the
Frequency
adaptivity setting value. Retardation and reset times are longer due to the length of the
measurement window. The frequency of the fault current affects the operate time. The
damping of the harmonics is quite low and practically determined by the
characteristics of the anti-aliasing filter of the protection relay current inputs.
When using measurement mode “Wide P-to-P”, the protection relay
accepts only
Operate delay time setting value 800 ms or longer and
Operating curve type 5=”ANSI Def. Time” or 15=”IEC Def. Time”.
Operation accuracy in the frequency range 2...85 Hz is ±1.5% or ±0.003 × I
n
. Operate
time accuracy in definite time mode is ±1.0% of the set value or ±60 ms when I
Fault
=
2 × set Start value and the fault current frequency is 10...85 Hz.
11.6 Calculated measurements
Calculated residual current and voltage
The residual current is calculated from the phase currents according to equation:
Io I I I
A B C
= − + +
( )
GUID-B9280304-8AC0-40A5-8140-2F00C1F36A9E V1 EN
(Equation 88)
The residual voltage is calculated from the phase-to-earth voltages when the VT
connection is selected as “Wye” with the equation:
Uo U U U
A B C = + +
( ) / 3
GUID-03909E83-8AA3-42FF-B088-F216BBB16839 V1 EN
(Equation 89)
Sequence components
The phase-sequence current components are calculated from the phase currents
according to:
I I I I
A B C 0
3
= + +
( ) /
GUID-2319C34C-8CC3-400C-8409-7E68ACA4F435 V2 EN
(Equation 90)
I I a I a I
A B C 1
2
3
= + ⋅ + ⋅
( ) /
GUID-02E717A9-A58F-41B3-8813-EB8CDB78CBF1 V2 EN
(Equation 91)
I I a I a I
A B C 2
2
3
= + ⋅ + ⋅
( ) /
GUID-80F92D60-0425-4F1F-9B18-DB2DEF4C2407 V2 EN
(Equation 92)
1MRS758755 A
Section 11
General function block features
REC615 and RER615 759
Technical Manual