Oven Replacement - RCD?

[brianmoooore]

If you're quick enough with the megger after the RCD trips, you will see a rapidly increasing resistance. The resistance when measured cold is orders of magnitude higher than when the hot element trips the RCD. Presumably caused by the element moving by expansion/contraction.
On the type of elements we are discussing, the live and neutral terminals have a foot or so of element between them, so L - N shorts aren't normally possible.
I was around long before RCDs, and it wasn't at all unusual to see holes blown in the outer sheath of these elements, or even severed completely.