Gathering insights for the heating conduit problem


Electrical & Instrumentation technician
I'd like to share an issue that we're currently resolving, and I'd greatly appreciate your input on potential causes and solutions.

Our team is relatively new to electrical thermography, and we've recently come across an anomaly at the substation. As shown in the image, one of the conduits carrying a supply line for the feeder exhibits a high temperature, approximately 70°C, while the other conduits maintain a normal ambient temperature.
Each conduit contains three wires and one ground wire, all with a size of 200mm². The feeder breaker is rated at 1000Amps, and it powers the production chiller and circulation pump.

No heating or anomalies were detected on the load side. The issues appear to be concentrated upstream, beginning at the tapping point on the main busbar, extending through a capacitor bank panel, and all the way to the feeder panel. Interestingly, it's only the conduit for phase A that exhibits this unusual heating phenomenon.

Additional details:
• No observed ground faults on accessible sections.
• Current readings on phases remain symmetrical, ranging from 120 to 180 Amps.
• Current reading on the ground wire is consistently 120 Amps and above.

Your insights would be greatly appreciated.

charlie b

Staff member
Lockport, IL
Retired Electrical Engineer
Am I seeing all phase A conductors in one conduit, and the same for phases B and C? There are very limited instances in which that is allowed.

Are all conduits the same material? If the hot conduit is of a magnetically permeable material and the others are not, then that could be your answer.

BTW, why are you seeing any current at all on the ground conductors? Substations are not my specialty, but that seems odd to me.