Basler Electric BE1-87T - Manual (Page 84)

4-42 BE1-87T Installation 9171300990 Rev V
Procedure Two
Refer to Figure 4-37 for a one-line drawing of this example.
Data
Figure 4-38. Two Winding Transformer Relay Setting Calculation Example
Specifications High side Low side
kV 69 12.47
MVA 12/20 12/20
CT Ratio 600 1200
CT Tap 300 800
CT Accuracy Class 400 800
CT Resistance (ohms) 0.18 0.48
One-Way Lead Burden
(ohms)
0.7 0.7
XFMR Connection* DELTA WYE
CT Connection WYE WYE
Input # 1 2
Fault Current (Three-
Phase)
1,916 10,603
Fault Current (Single-
Phase)
1,171 11,231
* Standard connection: High voltage leads low voltage by 30°.
Step 1. Determine the full load primary current (I
P
) of each winding:
Tap and Phase Shift Settings
Use the top kVA rating of the transformer when making the calculations:
HIGH LOW
IP =
× MVA rating of transformer 1,000
V 3 LINE - LINE
( )(
) ( ) (
)
IP
IP =
=
20,000
69
167.35
3
I
I
P
P
=
=
20,000
12 3
925
.47
.98