Distance Protection Requirements - GE MiCOM P40 Agile Technical Manual

Chapter 16 - Current Transformer Requirements
4

DISTANCE PROTECTION REQUIREMENTS

Zone 1 Reach Point Accuracy (RPA)
³ K ´ I
V (1+ X/R)(R
k RPA fZ1
where:
● V = Required CT knee point voltage (volts)
k
K = Fixed dimensioning factor = 0.6
●
RPA
● I = Maximum secondary phase fault current at Zone 1 reach point (A)
fZ1
X/R = Primary system reactance/resistance ratio
●
● R = CT secondary winding resistance
CT
R = Single lead resistance from CT to IED
●
L
Zone 1 Close-up Fault Operation
An additional calculation must be performed for all cables and lines where the source impedance ratio (SIR) may
be less than SIR = 2.
³ K
V I
k max fmax
where:
K = Fixed dimensioning factor = 1.4
max
I = Maximum secondary phase fault current
fmax
Then, the highest of the two calculated knee points must be used.
Note:
It is not necessary to repeat the calculation for earth faults, as the phase reach calculation is the worst-case for CT
dimensioning.
422
+ R )
CT L
´ I(R
+ R )
CT L
P543i/P545i
P54x1i-TM-EN-1