Short animations of the calculations behind cable and protection design. Project examples are
anonymised; the explainers use a standard's own worked example or a clearly labelled
illustration.
No. 1
Transformer tails: IEC or finite element?
Eight 33 kV tails in common ducts pass IEC 60287 and fail by finite element. What the spacing and a 6 x 2 bank change.
Circuit rating against the 546.7 A needed, IEC 60287 and finite element. Soil heat field by superposition of the cable losses.
Cable engineering in 30 seconds · No. 1 · See the series
Three cables in one duct, four duct sizes, one that works. The CIGRE TB 889 jamming band.
Duct fit to CIGRE TB 889 clause 4.5.2 for three cables in one duct: D/d below 2.8 and at least 13 mm over the top cable.
Cable engineering in 30 seconds · No. 2 · See the series
A relay graded above an LV breaker: why standard inverse cuts under it and extremely inverse does not.
Time-current curves from the grading engine, currents referred to 11 kV. Margins verified at the calculated fault levels.
Cable engineering in 30 seconds · No. 3 · See the series
Thermal thrust, a locking wave and a flexible loop, on the CIGRE TB 669 Annex 5 worked example.
CIGRE TB 669 Annex 5 worked example, a generic 400 kV cable. Geometry schematic after TB 669 Figure 106, wave offset exaggerated.
Cable engineering in 30 seconds · No. 4 · See the series
Single-point, solid and cross-bonded sheaths on an illustrative 1500 m route: voltage, current and why they cancel.
Illustrative example, not a project: 1500 m, 1000 A, trefoil. Standing voltage and circulating current from the EREC C55, IEC 60287-1-1 and IEEE 575 formulas.
Cable engineering in 30 seconds · No. 5 · See the series
Short-circuit forces on the clamps up to a sealing end, and what happens when there are too few.
Illustrative example, not a project: 132 kV, 200 mm phase spacing, 100 kA peak. Force per metre from CIGRE TB 889 eq (32); clamp rating from the manufacturer's published 113 kA test on a 117 mm cable.
Cable engineering in 30 seconds · No. 6 · See the series
An independent check of a 132 kV design across eight layouts, against a hand calculation that asked for a bigger cable.
Circuit rating against the 1021 A duty, IEC 60287. Soil heat field by superposition of the cable losses at the duty.
Cable engineering in 30 seconds · No. 7 · See the series
Energising one, five, seven and all fourteen transformers on a 49.9 MW battery site, against the ER P28 Issue 2 voltage change windows.
From an issued ER P28 Issue 2 study, anonymised: EMT energisation of 33/0.4 kV 4.35 MVA transformers at the minimum fault level, against the Issue 2 rapid voltage change windows.
Cable engineering in 30 seconds · No. 8 · See the series
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