Odd that with all the talk about the health hazards, the advantages that PCB
compounds brought to HV capacitors isn't mentioned. PCB is an additive that
raised the flash point of oils to the point were they were often considered
inflammable. In capacitors and transformers,of course, this was a great safety
advantage. We disposed of all our PCB-oil capacitors at work years ago - many
hundreds of large 45 kV units at great expense. Subsequently, the end-of-life
failures of the replacement capacitors (in pulsed load application, charged at
line frequency) became ruptures followed by fire. About 8 years ago, we were
getting a fire every month, plus cleanup, until we replaced 350 of the
Dielektrol-filled (GE) units with new ones. All of the new oils are easily set
afire if there is a significant spark inside the capacitor.
I wish the country hadn't done that (outlawed PCBs) without having industry
coming up with something as good or better for dielectric fluid. Nowadays
capacitor mfrs. are using stuff like Rape Seed oil. You could drink it, and you
can burn in it.
73
John
K5PRO
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