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Protective Elements
Minimum Current Threshold for Undervoltage Protection
For the voltage protection running in “undervoltage” mode –
»Mode« = “V<” – there is the option to activate an
undercurrent criterion. This is a “minimum current check”, which blocks the undervoltage protection as soon as all
phase currents drop below a certain threshold value. And vice versa, if the phase currents get available again after
such a dropout, the undervoltage protection is re-enabled only after a settable delay time.
The motivation for using this feature is that a situation where all phase currents are “dead” probably indicates an
open circuit breaker, and it is probably not desirable that the undervoltage protection reacts to this event. The
purpose of the delay time is to avoid an immediate trip during re-closing of the circuit breaker: Without this delay,
there would be the risk that the undervoltage protection trips instantly because the voltages have not yet risen
above the tripping threshold
»V<« (although the phase currents might already be above the minimum current
threshold).
The minimum current check is optional, in the sense that it has to enabled via setting
»Imin release check« =
active).
After the minimum current check has been anabled, the threshold value is settable via
»Threshold Imin«, i. e. the
undervoltage protection is blocked as soon as all phase currents drop below this value.
The delay time for re-enabling the undervoltage protection (after any of the phase currents has become “live” again)
can be set via
»t-delay Imin«.
If this minimum current check is active then you should be aware that without
current flow, the undervoltage protection does not trip. So, depending on your
application, there might be good reasons to not use this feature.
For the HighPROTEC MCDGV4: As the MCDGV4 is fitted with two CT measuring inputs, the minimum current
check is fixed to always use the current values of the CT Ntrl input (Current transformers on the neutral side,
slot X3).
For the HighPROTEC MCDTV4: As the MCDTV4 is fitted with two CT measuring inputs, the minimum current
check always uses the current values according to the Field Parameter setting
»VX Winding Side«.
826
MCDLV4
DOK-HB-MCDLV4-2E
Содержание HighPROtec MCDLV4
Страница 1: ...Manual Line Differential Protection MCDLV4 Software Version 3 4 a DOK HB MCDLV4 2E Revision A English...
Страница 3: ...Order Code Order Code 3 MCDLV4 DOK HB MCDLV4 2E...
Страница 47: ...Installation and Connection 47 MCDLV4 DOK HB MCDLV4 2E...
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Страница 433: ...Parameters 433 MCDLV4 DOK HB MCDLV4 2E...
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Страница 473: ...Blockings 473 MCDLV4 DOK HB MCDLV4 2E...
Страница 822: ...Protective Elements Name Description Profibus Scada Cmd 16 Scada Command 822 MCDLV4 DOK HB MCDLV4 2E...
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Страница 989: ...Protective Elements 989 MCDLV4 DOK HB MCDLV4 2E Pr Q P Q P Qr...
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Страница 1070: ...Supervision 1070 MCDLV4 DOK HB MCDLV4 2E...