SYSTEM PARAMETERS

Nominal System Voltage kV 11

System Configuration - Ring Main

Connected Load MVA 9.35

Demand Load MW 5

Power Factor (pf) p.u 0.85

Demand Ring Load Current (I) Amp 309

Ring Length (L) km 1.575

Maximum Permissible %Voltage Drop % 3.5

DERATING FACTORS

Method of Cable Installation The cable shall be buried directly underground at an average depth of 1000 ~ 1100mm in trefoil configuration.

Ground Temperature Correction Factor 0.83 Assuming a ground temperature of 500 C

Depth of Laying Correction Factor 0.96 Assuming a burial depth of 1100 m

Soil Thermal Resistivity Correction Factor 0.77 Assuming dry soil with thermal resistivity of 2.0 K.m/W

Cable Grouping Correction Factor 1.0 Only applicable to multiple circuits

Harmonic Current Correction Factor 1.0 Assuming a third harmonic content of less than 15%

Total Cable Current Derating Factor 0.61

CABLE SIZING

Cable Voltage Grade

Cable Construction

Cable Size (S) mm2185 240 300 185 240 300 300 400 500

Cable Resistance (R ) ohm/km 0.128 0.098 0.079 0.127 0.098 0.078 0.13 0.102 0.08

Cable Reactance (X) ohm/km 0.1 0.09 0.09 0.12 0.11 0.11 0.11 0.11 0.1

Rated Current Carrying Capacity Amp 383 436 481 405 463 516 405 454 507

Derated Current Carrying Capacity Amp 235 268 295 248 284 317 248 279 311

Voltage Drop Volt 136 110 96 144 119 105 142 122 102

%Voltage Drop % 1.24 1.00 0.88 1.31 1.08 0.95 1.29 1.11 0.92

Short Circuit Current Rating for 1 sec kAmp 45 47

Short Circuit Current Rating for 3 sec kAmp 25 28

SELECTED CABLES

300 mm2 3 x 1 Core Cu/XLPE/AWA/PVC

500mm2 3 x 1 Core Al/XLPE/AWA/PVC

MV CABLE SIZING

8.7/15 kV

3 x 1 Core Cu/XLPE/AWA/PVC 3 x 1 Core Al/XLPE/AWA/PVC1 x 3 Core Cu/XLPE/SWA/XLPE

The two selected cables (highlighed in green) satisfy the requsite current carrying and volatge drops demands of the envisaged system and also provide short circuit current

capability equal to or beyond the 25 kA rating of 11kV feeder switchgear.