Priniciples of Electromechanical Relay Operation
3.10 Dielectric Considerations
Dielectric ratings for relays are a function of size, the separation between
contacts, and the separation between various parts of the structure. The
ability of a relay to withstand impressed voltage depends on the type of
insulation employed and the severity of the in-service environment. Cold flow
of certain types of insulation at high temperatures or prolonged exposure to
extremely high humidity may result in a substantial reduction of the
dielectric withstanding voltage. Note also that self-induced or externally
developed voltage transients as well as the steady-state voltages impressed on
the winding or contacts should be well within the capability of a
design.