Restricted Earth Fault Protection Implementation; Low Impedance Ref; Setting The Bias Characteristic - GE MiCOM P40 Agile Technical Manual

Feeder management ied
Hide thumbs Also See for MiCOM P40 Agile:
Table of Contents

Advertisement

P14x
3

RESTRICTED EARTH FAULT PROTECTION IMPLEMENTATION

3.1
RESTRICTED EARTH FAULT PROTECTION IMPLEMENTATION
Restricted Earth Fault Protection is implemented in the Restricted E/F column of the relevant settings group. It is
here that the constants and bias currents are set.
The REF protection may be configured to operate as either a high impedance or biased element.
3.2

LOW IMPEDANCE REF

3.2.1

SETTING THE BIAS CHARACTERISTIC

Low impedance REF uses a bias charactersitic for increasing sensitivity and stabilising for through faults. The
current required to trip the differential IED is called the Operate current. This Operate current is a function of the
differential current and the bias current according to the bias characteristic.
The differential current is defined as follows:
I
I
I
(
=
+
+
A
B
diff
The bias current is as follows:
{
1
=
 
max
I
bias
2
where:
K = Neutral CT ratio / Line CT ratio
IN = current measured by the neutral CT
The allowable range for K is:
0.05 < K < 15 for standard CTs
0.05 < K < 20 for sensitive CTs
The operate current is calculated according to the following characteristic:
P14xEd1-TM-EN-1
I
K I
)
+
C
N
}
  +
,
,
I
I
I
K I
A
B
C
N
Chapter 7 - Restricted Earth Fault Protection
171

Hide quick links:

Advertisement

Table of Contents
loading

Table of Contents