80
High speed and instantaneous phase
overcurrent protection (HSOC, IOC)
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The protection is intended for single-phase and two-phase systems with a rated frequen-
cy of 16 2/3, 50 or 60 Hz.
The high speed and instantaneous overcurrent protection functions are non-directional
and normally serves as a local backup function to the distance protection.
The overcurrent protection has two operating modes:
•
HSOC that measures on sample level and is faster than the IOC, but has a larger
transient overreach.
•
IOC that measures on a filtered signal and has a limited overreach
The fault current on long lines depends mostly on the fault position and decreases with
the distance from the generation point. Faults very close to the generation (and relay)
point, for which very high fault currents are characteristic, should be cleared as quickly
as possible.
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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. An elliptical filter is used to filter the current signals before the ef-
fective value is calculated for the IOC function. The calculated effective value is
compared with a set operate value I>> and the output signal IOC-TRIP is activated in-
stantaneously if the measured current exceeds the operate value. A separate counter is
used as protection against large overreaching.
For the other, faster function, HSOC, a direct sample value is used, but a separate
counter protects the function from operation on individual current peaks. The signal is
compared with a set operate value, I>>> and the output signal HSOC-TRIP is activated
instantaneously if the measured current exceeds the operate value.
The simplified logic diagram of the instantaneous phase overcurrent function is shown
in figure 41.
The IOC function is disabled if:
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 ...