Test Cable Clamp KP 39/53
Test | Findings
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| Specification |
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| Cable Clamps |
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| Supplies |
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| Examples |
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| Short-Circuit Tests |
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| Certificate |
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| Contact |
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| Broschure |
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| Imprint |
Test:
Three twisted 20-kV single-core cables with cross-linked polyethylene insulation
and cross sections of 300 mm² (0.47 sq.in) were laid out in a U shape and held
in trefoil arrangement by the cable clamps.
| Test No. | Is kA |
a cm |
l m |
F N |
| 189-79/71 | 64,9 | 4,3 | 1,05 | 18.250 |
| 189-79/72 | 64,3 | 4,3 | 1,31 | 22.350 |
| 189-79/75 | 80,0 | 4,3 | 0,84 | 22.200 |
| 189-79/76 | 81,3 | 4,3 | 1,05 | 28.650 |
| 189-79/78 | 110 | 4,3 | 0,44 | 22.000 |
| 189-79/79 | 111 | 4,3 | 0,44 | 22.400 |
Findings:
Cable clamps withstood short-circuit forces of 18,250 to 28,560 N (4100 to 6440 lb.) without damage.
(Photographs 3 to 6 show the behavior of the trefoil
during and after the surge. Tests revealed that closer spacing of clamps slightly reduces heights
cable jump to.
Considerable bending of cables between clamps was observed.
Photographs 7 and 8 show the trefoil before and after tests 189-79/78 and 189-79/79. Here as well there is considerable bending of cables after two 110-kA surges, although the 44 centimeters (roughly 0.48 yd.) between clamps is the spacing normally used in practice. In these tests, the cables jumped to heights of only 0.2 to 0.3 m (roughly 0.2 to 0.3 yd.).
Besides the fact that the tested cable clamps meet the requirements placed on them, these experiments show that:
When using single-core, we recommend that the dynamic forces of the short-circuit current be considered as well, not only its thermic effects.
In order to prevent excessive bending of cables between clamps, the latter may have to be closer together for high short-circuit currents than their maximum admissible strain would normally dictate.
With high short-circuit currents, simply arranging the cables in trefoil and laying them on racks, for instance, it is not enough. As photograph 3 to 6 show, the bundled cables can be damaged during jumps, or they may damage other system parts. In such cases, it appears expedient to connect the trefoil to the rack at appropriate intervals, bearing in mind that the rack itself must be able to withstand a certain amount of strain. However, these tests do not allow us to state how high such strain may be.
Considerable bending of cables between clamps was observed.
Photographs 7 and 8 show the trefoil before and after tests 189-79/78 and 189-79/79. Here as well there is considerable bending of cables after two 110-kA surges, although the 44 centimeters (roughly 0.48 yd.) between clamps is the spacing normally used in practice. In these tests, the cables jumped to heights of only 0.2 to 0.3 m (roughly 0.2 to 0.3 yd.).
Besides the fact that the tested cable clamps meet the requirements placed on them, these experiments show that:
When using single-core, we recommend that the dynamic forces of the short-circuit current be considered as well, not only its thermic effects.
In order to prevent excessive bending of cables between clamps, the latter may have to be closer together for high short-circuit currents than their maximum admissible strain would normally dictate.
With high short-circuit currents, simply arranging the cables in trefoil and laying them on racks, for instance, it is not enough. As photograph 3 to 6 show, the bundled cables can be damaged during jumps, or they may damage other system parts. In such cases, it appears expedient to connect the trefoil to the rack at appropriate intervals, bearing in mind that the rack itself must be able to withstand a certain amount of strain. However, these tests do not allow us to state how high such strain may be.