Woodward MRM4, Manual

Page: 289 / 460

Protective Elements
Applications of the I-Protection Module Setting in Option
ANSI 51 – Short circuit protection, non-
directional
Device Planning menu Measuring Mode:
Fundamental/TrueRMS/negative
phase sequence current (I2)
ANSI 51Q Negative Phase Sequence
Overcurrent Protection
( Please refer to the 51Q chapter )
Parameter Set: Measuring
Method =I2 (Negative
Sequence Current)
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.
For each element the following characteristics are available:
•
DEFT (UMZ);
•
NINV (IEC/AMZ);
•
VINV (IEC/AMZ);
•
LINV (IEC/AMZ);
•
EINV (IEC/AMZ);
•
MINV (ANSI/AMZ);
•
VINV (ANSI/AMZ);
•
EINV (ANSI/AMZ);
•
Thermal Flat;
•
IT;
•
I2T; and
•
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«
EN MRM4 01/11 Page 289
t = Tripping delay
t-char = Time multiplier/tripping characteristic factor
I = Fault current
I> = If the pickup value is exceeded, the module/element starts to time out to trip.