GE P645

Parameter Description Value
Transient Bias This setting enables or disables the transient bias factor Enabled
Zero seq filt HV This setting enables or disables zero sequence filtering on the HV winding Disabled
Zero seq filt LV This setting enables or disables zero sequence filtering on the LV winding Disabled
Zero seq filt TV This setting enables or disables zero sequence filtering on the TV winding Disabled
IH2 Diff Set This setting defines the second harmonic blocking threshold. Disabled
CT Saturation This setting enables or disables CT saturation detection. Disabled
No Gap This setting enables or disables CT Gap detection. Disabled
IH5 Diff Set This setting defines the fifth harmonic blocking threshold. Disabled
A series of internal and external faults were simulated to determine the CT requirements for the differential
f
unction. We performed these tests with different X/R ratios, CT burdens, fault currents, fault types and points on
the current waveform.
The system conditions, CT dimensioning factor and CT kneepoint voltage are as follows:
System Conditions K Kneepoint voltage (VK)
In < I
F
<= 40In
5 <= X/R <= 20
16
VK => 16In(R
CT
+ 2R
L
+ R
r
) (ear
th fault)
VK => 16In(R
CT
+ R
L
+ R
r
) (phase fault)
40In < I
F
<= 64In
5 <= X/R <= 20
30
VK => 30In(R
CT
+ 2R
L
+ R
r
) (ear
th fault)
VK => 30In(R
CT
+ R
L
+ R
r
) (phase fault)
In < I
F
<= 40In
20 <= X/R <= 120
21
VK => 21In(R
CT
+ 2R
L
+ R
r
) (ear
th fault)
VK => 21In(R
CT
+ R
L
+ R
r
) (phase fault)
40In < I
F
<= 64In
20 <= X/R <= 120
30
VK => 30In(R
CT
+ 2R
L
+ R
r
) (ear
th fault)
VK => 30In(R
CT
+ R
L
+ R
r
) (phase fault)
where:
● V
K
= kneepoint v
oltage
● K = CT dimensioning factor
● I
n
= rated current
● R
CT
= resistance of CT secondary winding
● R
L
= Resistance of a single lead from device to current transformer
● R
r
= resistance of any other protection devices sharing the current transformer
● I
F
= maximum external fault level
Chapter 6 - Transformer Differential Protection P64x
140 P64x-TM-EN-1.3