General Electric Multilin Protective Relaying

Multilins SR745 & SR750 Model Power Supply Issues:

Recently, I have been tasked to perform some relay testing on multiple General Electric SR relay models. But in particular, the issues experienced have been with the original model SR745 (Transformer Protection Relay) and the SR750 (Feeder Protection Relay) models.

Here are examples of the Original and the Later model (Enhanced).

The years specified are the dates when these particular relays were made. The date is located on a sticker on the side of the relay when it is removed from the case.

GE Multilin 745 Protective Relay

SR745 Original (~2002)

GE Enhanced 745 Relay

SR745 Enhanced (~2013)

The first thing you need to do is isolate the trip power. When removing the trip fuses from the circuit, the relay should power down. After it’s powered down, it is safe to draw the relay out of the case. The issue identified is when temporary test power is restored to the relay, all LED’s flash or flicker and the relay never powers up. This is only present on some of the original models. Eventually all original model relays will have power supply failures if they don’t have a hardware failure first.

Upon speaking with General Electric, they know there are issues with the power supplies of the ~2006 SR750’s but this particular SR745 probably has a bad power supply AND bad hardware. In order to repair a broken relay, it can be shipped back to General Electric.

The cost is astronomical to repair one of these. It costs about 2/3 the cost of a brand new relay of the same model. Not only is it that expensive, there are no warranties on the repairs being made. The way General Electric sees it, this relay has exceeded it’s life expectancy of 15 years. They do not recommend any repairs.

Don’t be surprised if more original model relays begin to fail in the future. It is bound to happen. If you have any of the original models installed in your facility, you should begin buying the new enhanced relays as a backup. Lead time on a purchase can take a few weeks.

This product line comes from Canada. If you are in the US, not only do they assemble your product, it has to be shipped and sent through US Customs. Can you afford to be down a few weeks?

Here are a few examples of what you might see when a power supply fails:

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