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Sudden voltage change function (SVC)
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The sudden voltage change function, SVC, is intended for single-phase systems and is
applicable in systems supplied from static frequency converters. It can however also be
applied in two-phase systems but will only measure voltage change in phase UL1.
The function is intended to prohibit the distance protection tripping due to heavy load.
The function measures the voltage derivative (du/dt) and releases the distance protec-
tion tripping. It is a complement to the sudden current change function (SCC). If the
converter is working close to the current limit before the fault, it is not sure that suffi-
cient current change is obtained for the release of the impedance protection from SCC.
A quickly dropping of the voltage is obtained instead, which activates sudden voltage
change function.
The output signal from the step voltage function is configured to the logical element for
release of tripping from the impedance function, see figure in section
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The voltage measuring element in one of the built-in digital signal processors continu-
ously measures the voltages between the phase conductor and earth. The voltage signal
is conditioned by a filter before the fundamental frequency, RMS-value is calculated.
The difference between the RMS-value and the value one period earlier is calculated.
This difference is compared to the set operate value du/dt.
Figure 64 shows the simplified logic diagram for the step voltage function.
The output signal SVC-START is activated instantaneously if the change in voltage is
greater than the set operate value du/dt. A timer with the settable time t delays the return
of the output signal SVC-START.
The step voltage function is blocked if the input signal SVC-BLOCK is activated.
The signal SVC-VTSU, which is normally connected to the fuse-failure supervision
function, prevents unwanted operation of the step voltage change function.
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 ...