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I agree with RalphChristie: don't replace just because the relays are older EM-type. I would want to know a bit more about the system you are controling: LV, MV, HV? What is the industry? Is the application utility, industrial or commercial? If you do upgrade relays, this will determine what...

electricpete: I used to work in utility relay engineering, and recognize this GE relay as a very old EN type and most likely obsolete. If you intend to keep your system isolated (ungrounded) for reliability, you may want to consider 'monitoring' for grounds vs. 'detecting' them. If so, I...

What is the make/model of the relay(s)?

In many cases - and locations - 'the old days' are still here (as rhatcher mentioned). Because there is a perception by many supervisors and technicians that ground detection methods have not improved since the 3-lightbulb technique; ungrounded systems have received a bad rep and are continuing...

MakeItSpin: Careful with using 'voltage' relays to detect grounds in ungrounded systems. That method is somewhat outdated and ineffective - especially when you are trying to identify balanced/symetrical grounds and grounds within the DC portions of VFDs and VSDs. Not to wave their flag again...

There are many monitors manufactured today which are specifically designed for ground detection & location on ungrounded AC and DC systems. Rather than ground 'detectors' they are now referred to as Insulation Monitoring Devices (IMDs), because they accurately measure the insulation level of...

I agree with nukeman - there have been plenty of advancements in GF detection & location technology over the past 10-20 years - especially in Europe. Hospitals use this sort of isolated system in many applications. Along with the Ground Hog & the Megger unit, I would like to add Bender...

...one more thing - what is 'Forum 238' and where can I find it?

busbar: Thanks for the links to the papers/reports. Have you had any experience with online ground fault 'location' systems for 480VAC ungrounded (delta) systems in heavy industrial locations? Bender does make one, but seems to have limitations when it comes to large conductors and conduits...

Our experience with Bender (www.bender.org) has been good. They have been manufacturing Insulation Monitoring Devices (IMDs) for just this specific application for over 50 years. Does your AC system have DC components like VFDs or VSDs? If so, make sure the monitor you choose will 'see...