Advertisement
6 F 2 S 0 8 4 2
2.1.2.2 Scheme Logic
Directional phase overcurrent protection
Figure 2.1.35 and Figure 2.1.36 show the scheme logic of the directional phase overcurrent
protection DOC1 and DOC2 with selective definite time or inverse time characteristic.
The definite time protection is selected by setting [MDOC1] and [MDOC2] to "DT". Definite time
overcurrent elements are enabled for the DOC1 and DOC2 phase overcurrent protection
respectively, and trip signal DOC1 TRIP and DOC2 TRIP are given through the delayed pick-up
timer TOC1 and TOC2.
The inverse time protection is selected by setting [MDOC1] and [MDOC2] to any one of "IEC",
"IEEE", "US" or "CON" according to the IDMT characteristic to employ. Inverse time
overcurrent elements DOC1I and DOC2I are enabled for DOC1 and DOC2 protection
respectively, and trip signal DOC1 TRIP and DOC2 TRIP are given. The trip mode of DOC1
TRIP and DOC2 TRIP can be selected by setting [DOCTP] to "3POR"(any one of 3 phases) or
"2OUTOF3"(2 out of 3 phases) gate. When the "2OUTOF3" selected, the trip signal is not issued
during single-phase fault. The switch [DOCTP] is common for DOC1 to DOC4 protection.
The forward operate zone (DOC1F and DOC2F) or reverse operate zone (DOC1R and DOC2R) is
selectable by the scheme switches [DOC1-DIR] and [DOC2-DIR].
ICD is the inrush current detector ICD, which detects second harmonic inrush current during
transformer energisation, and can block the DOC1 and DOC2 protection by the scheme switches
[DOC1-2F] and [DOC2-2F] respectively. See Section 2.1.7.
The DOC1 and DOC2 protection can be disabled by the scheme switches [DOC1EN] and
[DOC2EN] or PLC logic signals DOC1 BLOCK and DOC2 BLOCK.
Figure 2.1.37 and Figure 2.1.38 show the scheme logic of the definite time phase overcurrent
protection DOC3 and the DOC4. DOC3 and DOC4 give trip and alarm signals DOC3 TRIP and
DOC4 ALARM through delayed pick-up timers TDOC3 and TDOC4. The trip mode of DOC3
TRIP and DOC4 ALARM can be selected by setting [DOCTP] to "3POR"(any one of 3 phases) or
"2OUTOF3"(2 out of 3 phases) gate. When the "2OUTOF3" selected, the trip signal is not issued
during single-phase fault.
The forward operate zone (DOC3F and DOC4F) or reverse operate zone (DOC3R and DOC4R) is
selectable by the scheme switches [DOC3-DIR] and [DOC4-DIR].
The DOC3 and DOC4 protection can be disabled by the scheme switches [DOC3EN] and
[DOC4EN] or PLC logic signals DOC3 BLOCK and DOC4 BLOCK.
The DOC3 and DOC4 can also be blocked by the ICD.
⎯
⎯
42
Advertisement
