Relay Issue with High Voltage

If it's a DC relay, one of the possibilities is the collapse of the magnetic field as the relay turns off. To suppress it, connect an appropriately-rated silicon rectifier reverse-biased across the terminals of the coil.

This may be the case of poor design or not designed with min max analysis.

May be coil temp rises to too high, that leads to significant increase in resistance causing decrease in coil current.also this increase in temp will deteriorate the magnetic properties of magnetic path.

Every 100Deg increase in coil temp will add 40%(approx) on coil Resistance.

You should think before choosing a relay.Do you know how to choose a relay.

See the link :

http://www.4engr.com/forum/view_topic-pid-612.html#p612

Relay contacts can arc at high voltages and the contacts will get worst with time. But you need to give more data. What is normal and high voltage? How are you driving the coil? What current are we talking about? What are the ratings of the relay? What is the application? Post more detail otherwise it is difficult for us to help!

Is it not switching or switching and not making (or breaking) contact? Or is it making contact but has too high contact resistance (poor contact integrity)? Is the relay failsafe (returns to original position when de-energized) or latching (stay in selected position). Give us a clue and we can probably help you to resolve your problem.