HV – High Voltage Cable Sizing Calculator

HV - High Voltage Cable Sizing Calculator

Sizing high voltage cables involves determining the proper parameters for cables used to carry or distribute power at high voltages.

  • Voltage rating,
  • Current carrying capability,
  • Insulation type,
  • Conductor material,
  • Environmental conditions, and
  • Regulatory criteria

are all taken into consideration. Proper size enables safe & efficient transmission while reducing losses and preserving system reliability.

When calculating the cross sectional area of a high-voltage cable, the result found using the following formula:

S = (ISC X √t ) / K


S – The conductor’s nominal cross-sectional area in mm2

ISC – Short circuit current or fault current value in KA

T – Fault clearing time in seconds

K – Factor based on conductor material resistivity, temperature co-efficient, heat capacity, initial and final temperature.

BS 7671 defines K as

  • 0.094 for XLPE-insulated Aluminium cables,
  • 0.143 for Copper cables, and
  • 0.076 for PVC-Insulated Aluminium cables.

When the formula yields a non-standard size, a conductor with the next higher standard cross section area must be utilized.

The short circuit duration for cables should correspond to the tripping time of the feeder’s protection devices.

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