A contractor had a 132 kV cable design from their supplier and wanted it checked before committing. We rebuilt the rating from first principles to IEC 60287 across every installation case the route could present.
The Brief
- A 1600 mm² aluminium 132 kV design, roughly 200 m of route, for phase one of a 200 MW battery site.
- The design existed. What did not exist was an independent check that it held up in every configuration the route would actually be built in.
- The commercial risk sat on the conductor size: going up a size after order is expensive, and going up a size unnecessarily is expensive too.
How It Was Done
- Eight separate rating cases rather than one: one and two circuits, flat and trefoil formation, ducted and direct buried, taken in combination.
- The phase-two circuits were included as a mutual heating case, because a cable that passes today can fail once the neighbouring circuit is energised.
- Every input stated, and every assumption that could not be evidenced flagged in the report rather than buried in a spreadsheet.
What Came Out Of It
- The stated 1600 mm² aluminium design carries the phase-one duty in seven of the eight cases. A separate hand calculation had asked for 2000 mm² copper, and it was not needed.
- The one failure was both circuits in touching trefoil, direct buried, where the two circuits heat each other: 980 A against a 1021 A duty. That is the case most often left out of a supplier rating.
- The fix was a layout choice, not a bigger cable. Ducting the same trefoil clears the duty, and flat formation carries the full transformer rating on both circuits.
Standards applied
IEC 60287
Published without naming the client. The technical detail is exactly as delivered.
Something Similar?
Tell us the voltage, the duty and what you need out of it, and we will come back with a scope and a fee.