HRG 480 Volt shock hazards using 3 phase band heaters with metal flexible cords

[wintersnow]

Metal flexible cord whips appear to have inductive heating.
What is the potential of HRG 93 OHMS With a single fault. Delta wired 3 phase heaters.

I have several pictures to share but am unable to paste.

 

[GoldDigger]

As long as both sides of the circuit are in the same (ferrous) metal sheath, there should not be much if any noticeable inductive heating.
If the sheath is carrying ground fault current from a fault in the heating element you will get both inductive and resistive heating. The fault current might not trip a non-gfci breaker.
A ground fault right in the middle of the element will draw excessive current from both phase legs and put equal current through the sheath.

 

[wintersnow]

Do you have an e- mail to attach some photos?

 

[Dennis Alwon]

Do you have an e- mail to attach some photos?

I sent you my email. You need to have a few more posts to be able to share pics

 

[wintersnow]

So many possible types of GF failures.
For this example circuit two 7,000 watt 3 phase band heaters. 3500 watts each half for a total of 4 halfs =14,000 watts total 18 amp nominal combined load are wired in parrell with each have a separate plug approx 66 OHMS each or 33 Ohms combined. Measured. At the bottom of a solid state relay switching only two phases typical. Protected by high speed 25 Amp fuses all three phases.
Solid ground fault measures 0 ohms on one phase and 66 OHMS on the remaining phase to ground. The HRG transformer measures 3 amps for fault current and provides alarms. What will be the fault current for remaining fault through the 66 ohm heater to ground? Is there adequate protection. Equipment is a secondary path for fault current to provide a low resistance stable path if firmly attached.

 

[Jpflex]

As long as both sides of the circuit are in the same (ferrous) metal sheath, there should not be much if any noticeable inductive heating.
If the sheath is carrying ground fault current from a fault in the heating element you will get both inductive and resistive heating. The fault current might not trip a non-gfci breaker.
A ground fault right in the middle of the element will draw excessive current from both phase legs and put equal current through the sheath.

If both phases were not in the same ferrous metal conduit nec would require a non ferrousinsulated plate at cable entrance to equipment or slots made between phases to avoid heating effect

 

[GoldDigger]

If both phases were not in the same ferrous metal conduit nec would require a non ferrousinsulated plate at cable entrance to equipment or slots made between phases to avoid heating effect

This would avoid the eddy current heating at the cable entrance, but would have no effect on any possible heating (smalll) in the cable itself.

 

[wintersnow]

I understand the small heating potential. Thank you for sharing your knowledge
What about fuse protection for the many possible ground fault short curciut protection @25 amps solid state fast acting fuse to protect the SSR. The typical heater circuit 3 phase 7,000 watts each for a combined load of 14,000 wired in a parallel with two plugs. Would adequate protection be afforded for a single faulted heater to ground. Measured fault resistance 0 ohms to ground 1 phase and 66 ohms to ground remaining phases. HTG grounded system with 3 amps of fault current