CYG PRS-7367 - Page 210

Protection Functions
202 PRS-7367
0d
I
is the residual differential current of one side.
3.42.2.2 Amplitude Compensation
If CTs used for REF have different primary rated values, the device will automatically adjust the
currents with respective correction ratio shown as below.
TA X
lph X
TA H
K
K
K




Where:
TA X
K

primary side sampled zero-seq CT ratio.
TA H
K

primary side CT ratio. Primary side is reference and Kp is 1.
Transformer balance factor is calculated by this formula. When compensation, multiply current and
Kp.
3.42.2.3 Calculate Differential and Restraint Current
REF differential current and restraint current are calculated as the following formulas:

0 0 0 d Cal Neu
I I I
 

0 0 0
max ,
r Cal Neu
I I I
Where:
I
0d
is the REF differential current;
I
0r
is the residual restraint current;
I
0Cal
is the residual current of the phase currents;
I
0Neu
is the neutral measured current;