I found this interesting from
ATSB TRANSPORT SAFETY REPORT
Aviation Occurrence Investigation – AO-2009-027
In-flight fire
427 km south-west of Guam
10 June 2009
Airbus A330-202, VH-EBF
https://www.atsb.gov.au/media/250036...27%20final.doc
From p15
Window heat computer (WHC) inspection
It was reported to the ATSB that upon opening of the number-2 WHC’s external case, some internal electrical circuits exhibited damage to discrete components and circuit boards. Based on that damage, the WHC manufacturer concluded that excessive voltage from the windshield temperature sensor wires had been conducted through to the WHC, and upon exposure to that voltage, the internal components and circuitry became damaged from electrical overstress. It was also concluded that the last ‘hard-fault’ as contained in the PFR relevant to the number-2 WHC, was written by the central maintenance computer at 1524 when the WHC ceased functioning.
In that case it was the plug to the windscreen that had overheated & melted, BUT....the Windscreen Heater Computer also suffered electrical damage as the power applied to the heater elements was fed back down the sensor element wiring back into the WHC. The heater elements are supplied with 200VAC at up to 3.6kw. It would be assumed that the circuit breakers would not detect a fault if the current was below the 3.6kw normal limit.
In a worse case scenario, this would led to a fire in the WHC in the avionics bay.
EDIT: Additional note, the cabling was also damaged, so fire/smoke could have been generated along the entire length of the sensor/power cable.