5.10.5
Parameters
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Table 92: Inverse time earth fault overcurrent function - parameters
Signal
Description
ParSet4..1
Parameter for determining in which set of parameters a particular function is
active.
CurrentInp
Defines the CT input channel. All the current channels are available for selection.
c-Setting
Setting for the exponential factor determining the shape of the operating
characteristic according to BS 142 or for selecting the RXIDG characteristic.
k1-Setting
Tripping characteristic constant
IStart
Pick-up setting (initiates the tripping characteristic).
tmin
Definite minimum time of the tripping characteristic.
NrOfPhases
Number of phases evaluated for measurement:
•
1: neutral current direct from an CT input
•
3: neutral current derived internally from the three phases
IB-Setting
Reference current to take account of discrepancies with respect to IN.
BlockingInp
I/P for the external blocking signal.
•
F: unused
•
T: function always blocked
•
xx: all binary I/P's (or O/P's of protection functions)
Trip
Tripping signal
Start
Pick-up signal
5.10.6
Configuration
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Protection function enable IStart
The function starts to run when the current applied to the function exceeds the setting
IStart.
IStart is normally set to 1.1 IB.
Choice of tripping characteristic c-Setting
The shape of the IDMT characteristic is determined by the constant c.
The standard IDMT characteristics according to BS 142 are:
normal inverse:
c = 0.02
very inverse and long time earth
fault:
c = 1.00
extremely inverse:
c = 2.00
Section 5
1MRK 505 406-UEN B
Bay protection functions
170
Bay protection functions REB500
Technical manual
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