## Sample Calculation of Relay Setting of P543

Length of Protected Line (L): 1.645 KM
Length of Adjacent Line (L1): 24 KM
Length of Adjacent Line (L2): 44.3 KM
Line positive sequence Impedance (Z1): 0.1556+J 0.381 ohm
: 0.4115<67.758 ohm
Line Zero sequence Impedance (Z0): 0.378+J 1. 298 ohm
: 1.352<73.76 ohm

Line Angle (RCA): 67.76 deg
CT Ratio: 400/1A
PT Ratio: 132kv/root3/110V/root3

## Calculation and relay setting

Transformation ratio (n): CT Ratio/ PT Ratio: (400/1) / (132000/110)
: 0.3333
Positive Sequence Impedance for Prot. line (Line Impedance ZL): 0.41151.645 : 0.677 ohm (Primary Value): 0.677 * 0.3333
: 0.226 ohm (Secondary Value)

Positive sequence Impedance angle:
Line Angle (RCA): 67.76deg ≈68 deg

## Ground Factor Calculation

Grounding Factor Kg: (Z0-Z1)/3Z1
: (0.378+J 1. 298 – 0.1556+J 0.381)/3(0.1556+J 0.381)
KZ1, KZ2, KZ3: 0. 764
Angle of Grounding Factor Kg: (arc Tan((X0-XL/(R0-RL)))-(arc Tan(XL/RL))1807/22
Kang: 8.61 deg.≈ 9 deg

## ZONE SETTINGS

Zone-1 reach
Dist Z1(Quad.): (80% of Protected Line Impedance*(CTR/PTR)) : 0.8*0.677*0.3333
: 0.181 ≈ 0.184 ohm
Ttrip: Inst.

Zone-2 reach
DIST Z2 (Quad.) : (100% Protected Line Impedence+50% of next shortest line
Impedance) x(CTR/PTR)
: (1*0.4115*1.645+0.5*0.4115*24)*0.3333
: 1.872 ohm
Ttrip: 400 ms
OR
: 120% (ZL)
: 1.2 *0.230
: 0.276 ohm

Zone-3 reach (Not required)
DIST Z3 (Quad.): (100% of Protected Line Impedence+100% next longest line
Impedance)(CTR/PTR): (1*0.4115*1.645+1*0.4115*44.3)*0.3333
: 6.302 ohm
Ttrip: 600 ms

Zone-4 reach
DIST Z4 (Quad.): (10% of Protected line Impedance)(CTR/PTR) : (0.1*0.4115*1.645)*0.3333
: 0.023 ohm
Ttrip: 1000 ms