High Voltage Cable Sizing
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:
Formula
S = (ISC X √t ) / K
Where,
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.
Points to Remember
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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 Cable Sizing Calculator to determine the best parameters for cables utilized in high voltage transmission and distribution networks. Accurate sizing calculations help to ensure safety, efficiency, & regulatory compliance.){kind=link}