The test was carried out at ERA of Leatherhead on February
14th 2008. The purpose of the test was:
i) To carry out ‘due diligence’ safety tests so that the cable
glands (cable termination) products produced by Pro-term Ltd were tested under laboratory conditions at ERA of Leatherhead
ii) To verify that the new and unique method of grounding (360o grounding teeth) was valid and was able to carry fault currents related to the host cable capability and subsequently still retain low electrical resistance post fault current test
iii) To test the cable gland products on both laboratory jigs and also industrial standard metallic electrical enclosures
There were two products to be tested:
a) The Pro-term BITE gland, this is for the termination of ‘Steel Wire Armoured’cables.
b) The ‘Spring-clamp’ gland system, this is for the termination of braidedarmoured/screened cables
The tests were as prescribed in EN50262 where:
a) The cable glands were to be in circuit grounding the armouring/shielding, the electrical potential is between the two bus bars of the test jig.
b) To re-test the resistance values after the high current short circuit test with a calibrated high current continuity test meter.
c) The test time was nominated at one second.
Results of the braided armoured (SY cable) test
i) The flexible armoured cable with the pro-term ‘Spring-clamp’ products were tested at a current value of 540 amps and neither the cable glandnor the cable showed any physical ill effects and the electrical continuity was <5 milliohm
ii) The same assembly was tested at >1,500 amps, the cable had visiblydeteriorated (burned black) and the SY braided armour had failed, thecable gland remained unaffected.
iii) The test proved that the cable gland system had greater fault currenthandling capability than the host cable.
Left photo shows the burnt SY cable.
Right photo shows the cable armouring failure at the point of termination.
Results of the Steel Wire Armoured (SWA) cable termination
i) The steel wire armoured cable was unaffected at 1,700 amps RMS for 1second
ii) The same cable was subjected to 2,600 RMS for 1 second and showedserious heat degradation, the cable glands were unaffected and showed no degradation.
iii) A new cable harness (into a painted commercial thin metal box) was subjected to 6,700 amps (peak), the cable insulation was totally destroyed, the thin metal box connection heated at the point of connection to the cable gland and showed signs of degradation.
Left photo – harness pre test
Right photo - results of 2,600 amp RMS one second test, the cable (4mm2 3 core)had current limiting capabilities, cable glands were unaffected.
Photo above – 6,700 amps (peak) caused the cable to fail and ignite, the heat caused increased impedance restricting the 1 second RMS value to 2,700 amps, the
armour wires of the cable were welded together such was the heat.
Conclusions & Observations
i) The glands out performed the host cables in terms of fault current carrying capability.
ii) Where cable electrical armour was maintained the glands showed low electrical continuity after the fault current test (<5 milliohm)
iii) The Pro-term ‘automatic grounding system’ (AGS) showed good capability for bulk fault current carrying.
iv) There was no noticeable physical degradation of the cable glands where the cable survived.
v) The braided armour cable fault current capability was limited to less than 1000 amp RMS for 1 second.
vi) The Wire armoured cable fault current capability was limited to less than 3,000 amp RMS for 1 second.
vii) The pro-term cable glands fully comply to the standard EN50262.