99
Sudden current change function (SCC)
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The sudden current change function SCC measures the current increase per time unit
(di/dt) in all phases (one or two). In order to distinguish between heavy traction loads
and faults, it is used to enable the instantaneous trip from the measuring zone 2 and/or
the measuring zone 3 on the distance protection. The function can be activated or deac-
tivated via a binary input.
The sudden current change function’s operating modes may be selected from the fol-
lowing:
•
Off.
•
As start for zones 2 and 3 (Normal).
•
As start for zones 2 and 3 and as backup function when the primary protection is
down due to different reasons, e. g. blocking from the fuse failure supervision func-
tion (Backup).
The output signals from the sudden change current function should be configured to the
logical element for release of tripping from the impedance function, see figure in sec-
tion
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The current measuring element in one of the integrated signal processors continuously
measures the phase currents (IL1 and IL2) in two-phase systems and current IL1 in sin-
gle phase systems. The current signal is filtered by a low pass filter. The difference be-
tween the filtered value and the actual current value is calculated and compared with
the set operate value. The output signal SCC-START is activated instantaneously if the
measured current difference exceeds the set operate value. A timer delays the resetting
of the signal by the set time t.
The simplified logic diagram for the SCC function is shown in figure 45.
Содержание REO 517
Страница 10: ... RQWHQWV ...
Страница 16: ...6 Introduction to the application manual KDSWHU QWURGXFWLRQ ...
Страница 64: ...54 Blocking of signals during test KDSWHU RPPRQ IXQFWLRQV ...
Страница 88: ...78 Scheme communication logic ZCOM KDSWHU LQH LPSHGDQFH ...
Страница 100: ...90 Time delayed phase and residual overcurrent protection TOC1 KDSWHU XUUHQW Equation 36 Iset IsSEC I1b 100 ...
Страница 146: ...136 Unbalance protection for capacitor banks TOCC KDSWHU XUUHQW ...
Страница 166: ...156 Dead line detection DLD KDSWHU 3RZHU V VWHP VXSHUYLVLRQ ...
Страница 171: ...161 About this chapter KDSWHU RQWURO KDSWHU RQWURO ERXW WKLV FKDSWHU This chapter describes the control functions ...
Страница 293: ...283 About this chapter KDSWHU RJLF KDSWHU RJLF ERXW WKLV FKDSWHU This chapter describes the logic functions ...
Страница 378: ...368 Monitoring of DC analog measurements KDSWHU 0RQLWRULQJ ...
Страница 379: ...369 About this chapter KDSWHU 0HWHULQJ KDSWHU 0HWHULQJ ERXW WKLV FKDSWHU This chapter describes the metering functions ...
Страница 384: ...374 Pulse counter logic PC KDSWHU 0HWHULQJ ...
Страница 412: ...402 Serial communication modules SCM KDSWHU DWD FRPPXQLFDWLRQ ...
Страница 440: ...430 LED indication module KDSWHU DUGZDUH PRGXOHV ...