These matching factors are also displayed in the SY
STEM CONFIG column (Match Factor CT1 and Match Factor
CT2)
Now set the current differential parameters as follows:
Setting in GROUP 1 DIFF PROTECTION Value
Trans Diff Enabled
Set Mode Advance
Is1 200.0e-3 PU
K1 30.00%
Is2 1.000 PU
K2 80.00%
tdiff 0 s
Is-CTS 1.500 PU
Is-HS1 10.00 PU
HS2 Status Disabled
Zero seq filt HV Enabled
Zero seq filt LV Enabled
Zero seq filt TV Enabled
IH2 Diff Block Enabled
IH2 Diff Set 20%
Cross Blocking Enabled
CT Saturation Enabled
No Gap Enabled
IH5 Diff Block Enabled
IH5 Diff Set 35%
Circuitry Fail Disabled
5.4 EXAMPLE 3: AUTOTRANSFORMER WITH UNLOADED DELTA WINDING
Consider an autotransformer with the following specifications:
● P
ower rating: 175/175/30 MVA
● Connection type: YNyn0d1
● Voltage specification: 230/115/13.8 kV.
● HV CT ratio: 1200:5
● LV CT ratio: 1200:5
● Neutral CT ratio: 1200:5
● HV taps at +5% and -15%
The winding configuration is set to HV + LV + TV. The CT on the HV line side is connected to T1 CT, the CT on the HV
neutral side is connected to T2 CT, and the CT on the LV side is connected to T3 CT.
P64x Chapter 6 - Transformer Differential Protection
P64x-TM-EN-1.3 127
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