Schweitzer Engineering Laboratories SEL-321 - Distance Element Setting Calculations

5-8 Applications Date Code 20011026
SEL-321/321-1 Instruction Manual
Distance Element Setting Calculations
All settings for the SEL-321 Relay are in secondary quantities. For example, the Zone 1 phase
distance element is set as follows:
Calculations: PTR = 2000:1 PTR/CTR = 10
CTR = 200:1
Zone 1 secondary Ω =
62 42
10
6242
.
.
Ω
Ω
primary
=
secondary along the line angle
All phase and ground distance element secondary settings are calculated in the same manner.
All distance elements are supervised by overcurrent elements. For example, the Zone 1 phase
distance fault detector is set as follows:
Calculations: CTR = 200:1
50PP1 secondary Ω =
510
200
255
A primary
A= .
secondary
All supervisory overcurrent element secondary settings are calculated in the same manner.
Z1P = 6.24
6.246.24
6.24
Z2P = 9.36
9.369.36
9.36
Z3P = 1.87
1.871.87
1.87
50PP1= 2.55
2.552.55
2.55
50PP2= 2.22
2.222.22
2.22
50PP3= 2.45
2.452.45
2.45
Z1MG = 6.24
6.246.24
6.24
Z2MG = 9.36
9.369.36
9.36
Z3MG = 1.87
1.871.87
1.87
XG1 = 6.24
6.246.24
6.24
XG2 = 9.36
9.369.36
9.36
XG3 = 1.87
1.871.87
1.87
RG1 = 2.50
2.502.50
2.50
RG2 = 5.00
5.005.00
5.00
RG3 = 6.00
6.006.00
6.00
50L1 = 0.90
0.900.90
0.90
50L2 = 0.90
0.900.90
0.90
50L3 = 1.30
1.301.30
1.30
50G1 = 0.90
0.900.90
0.90
50G2 = 0.60
0.600.60
0.60
50G3 = 0.50
0.500.50
0.50
- Relay Elements and Other Settings Affected
All set distance and overcurrent supervision elements.