Protective Elements
Measuring Mode
For all protection elements it can be determined, whether the measurement is done on basis of the »
Fundamental«
or if »
TrueRMS«
measurement is used.
Alternatively the »
Measuring Mode«
can be set to
»I2«
. In this case the negative phase sequence current will be
measured. This is to detect unbalanced faults.
Voltage restraint overcurrent protection 51V
When the Parameter »
VRestraint«
is set to active the overcurrent protection element works voltage restraint. That
means, the overcurrent pickup threshold will be lowered during voltage drops. This results in a more sensitive
overcurrent protection. For the voltage threshold »
VRestraint max«
additionally the »
Measuring Channel«
can be
determined.
Measuring Channel
With the parameter
»Measuring Channel«
it can be determined, whether the »
Phase to Phase«
voltage or the
»
Phase to Neutral«
voltage is measured.
With the setting »CT Winding Side« = “CT Mains” (Current Transformer Mains Side), all overcurrent protective
elements can be planned as non-directional or optionally as directional (forward / reverse) elements.
(If »CT Winding Side« = “CT Ntrl” (Current transformers on the neutral side), only the non-directional mode is
available.)
For each element the following characteristics are available:
DEFT (UMZ) –
Definite Time-Overcurrent
NINV (IEC/AMZ) –
IEC Normal Inverse
VINV (IEC/AMZ) –
IEC Very Inverse
LINV (IEC/AMZ) –
IEC Long Time Inverse
EINV (IEC/AMZ) –
IEC Extremely Inverse
MINV (ANSI/AMZ) –
ANSI Moderately Inverse
VINV (ANSI/AMZ) –
ANSI Very Inverse
EINV (ANSI/AMZ) –
ANSI Extremely Inverse
RINV –
R Inverse
Thermal Flat
IT
I2T
I4T
Explanation:
By using the projecting parameters each of the overcurrent protective elements can be defined as
»forward«
,
»reverse«
or
»non-directional«
. The forward or reverse direction is based on the characteristic angle for the phase
direction specified by the field parameter
»I MTA«
. No directional information will be taken into account if the current
protective element is planned as
»non-directional«
679 MCDGV4 DOK-HB-MCDGV4-2E
t = Tripping delay
t-char = Time multiplier/tripping characteristic factor. The setting range depends
on the selected tripping curve.
I = Fault current
I> = If the pickup value is exceeded, the module/element starts to time out to trip .
To Next Page
