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Life expectancy of microprocessor-based protective relays (IED)

Life expectancy of microprocessor-based protective relays (IED)

Life expectancy of microprocessor-based protective relays (IED)

The question has arisen at my workplace as to what we expect out of these things. I have devices installed in excess of twenty years ago.

What do I tell our managers about their life expectancy? We're starting to see sporadic failures on devices.

That is not to mention that software, firmware and hardware revisions have passed up my installed devices long ago. My employer replaces laptop computers at five years. What am I supposed to believe about IED's that protect the plant power system that have been in service twenty years?

What's the industry consensus?

old field guy

RE: Life expectancy of microprocessor-based protective relays (IED)

Good question. I would like to add that most manufacturers stop supporting the relay communication software when they stop supporting the relays. That is a real problem if the software uses proprietary protocols to communicate with the relay and the software only runs on obsolete versions of windows (NT).

RE: Life expectancy of microprocessor-based protective relays (IED)

After 20 years I would be getting concerned about support and be thinking seriously about replacement. IC's become obsolete, and continued support simply isn't possible in all instances. Based on our failure rates, not many Alstom / Areva / GE Grid MiCOM relays will see their 20th birthdays without intervention. The best I can hope for is that a newer, more reliable product is developed which is physically interchangeable with the current generation.

The software is a very good point: at my previous employer I was running MS-DOS as one boot option on my laptop so I could talk to the ABB REG216 relays in our HV substation. The REOR100 event recorder software ran under Win 3.11. That was at 17 years or so into their life, and in software and operating system terms that is forever.

RE: Life expectancy of microprocessor-based protective relays (IED)

Of course there's the support software as mentioned. That can render good hardware useless for a company's use if adjustment and service tasks become troublesome or undoable.

Microcontrollers that are not re-programmable will probably run happily for about 20~25 years.
Microcontrollers that are programmable.. Twenty years is pushing it especially if it is a safety device and not, say, a pinball machine where one might lose a game and 25⊄ in a failure. You can expect about 8~10 years before soft errors can start coming out of the firmware due to the re-programmable memory starting to 'forget' due to multiple physical mechanisms.

This can be mitigated by reprogramming the processors via reading them out while they're still viable and simply reprogramming them. Some companies bright enough to understand this offer re-programming service where they'll send out a new set of chips and you return yours so they can reprogram them and send them to the next guy. That has your 'machine' down only long enough to swap the firmware chips. Other companies have to keep updating their firmware and this gets done automatically with no one catching on until they stop updating the firmware because they finally (think) they've reached nirvana.

The above usually works well only for systems with plug-in EPROMs and in some cases plug-in EPROM based microcontrollers. For other systems the only alternative would be a new set of control boards with 'freshly programmed firmware'.

OTPROMs or One-Time-Programmable-Read-Only-Memory can last indefinitely if it is the type that blows fuses during programming as then there are no memory cells to forget with. However other companies have OTPROMs that are merely windowless and therefore un-eraseable but still have memory cells that will forget. Often they can still be re-programmed to freshen them up but, of course, you can only exactly reprogram them as no values can actually be changed.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Life expectancy of microprocessor-based protective relays (IED)

We're using relays that can be interacted with using a terminal emulator as well as somewhat friendlier setting software. We're seeing equipment failures at 22-24 years of age that are requiring the relays to go back to the factory for refurbishment. The one's we're having the most issue with wire up very differently from what we'd replace them with, so an update is a full project. Grabbing a refurbished replacement is quicker.

RE: Life expectancy of microprocessor-based protective relays (IED)

I believe both Multilin and SEL offer 10 year warranties so those relays should be serviceable for at least 10 years. Relays developed today using any decently thought out and planned architecture will not have software that becomes outdated until long after you cease to care. The software will be modular and basically include a definition that will continue to carry forward into the core software which can continually be updated to match the current version of Windows.

RE: Life expectancy of microprocessor-based protective relays (IED)

SEL's 10 year warranty is effectively much longer; they're still covering relays that over 20 years old, no questions asked. We're preemptively sending in spares for refurbishment, including a new main board, so that we can replace pairs when one finally dies. That's much easier than sending in one failed relay for repair and then turning around in a few months having to do the same with its mate. The 25 year old designs have the two relays so interconnected that it's as much work to replace one as it is to replace both.

RE: Life expectancy of microprocessor-based protective relays (IED)

I would not say no questions asked, as we had some that were water damaged, and we had to pay to fix them, but other than that SEL has replaced all the failed ones we had.

But I agree that 20 to 25 is looking like the end of the bathtub.

The microprocessors are not like the EMs we took out of service at 75 years.

RE: Life expectancy of microprocessor-based protective relays (IED)

So its safe to say EMs are outlasting the microprocessors?

RE: Life expectancy of microprocessor-based protective relays (IED)

Sad but true. But since event analysis is a core part of my job I have no interest in going back to the EM days. The relay feature set has increased so much that I’m ready to replace everything more than 7 years old or so, but funding for that doesn’t exist.

RE: Life expectancy of microprocessor-based protective relays (IED)

Sad indeed. But then again the reduced need for testing makes up for it. Seen POCOs go as far as eliminating test switches.

FWIW, can you still buy new EM relays like distance and time over current?

RE: Life expectancy of microprocessor-based protective relays (IED)

Eliminating test switches is extraordinarily shortsighted as far as I can tell. I'll accept opening and closing of test switches as an acceptable difference between the as-tested and as-operated conditions. Not sure how anybody can equate as-tested and as-operated conditions without test switches. Perhaps a lack of imagination on my part, or something else on the part of those will operate in a condition that was never tested. A wire reterminated after testing does not leave the protection system in an as-tested condition. At least in NERC/FERC land we've move way past relay testing into the realm of protection system testing and I'm in the camp that doesn't see testing in a non-operational condition as relevant.

Last I heard you could still buy new EM replacements for IAC, CO, and KD relays, if not others. A brand new KD might well cost as much as a brand new SEL-411L, but as far as I know they can be had. Other than having to remove the mothballs from the factory, a new KD is nearly 100% profit at what ever cost; anybody that actually wants one really, really, really wants one and will pay any price so why not the top price? The ones we have are sunk costs, fully amortized. Can't possibly imagine going there again; they don't do so well with two breaker (ring, BAAH, DBDB, etc.) applications when compared with the modern relays. That's why the two breaker configurations didn't really take off until newer relays could provide two electrically independent trip contacts.

oh, but the EM relays don't give a sh!t about EMP and other esoteric threats to the power system. My gut feeling is that if an EMP event takes out our relays there probably is a whole heck of a lot of load left serve in the immediate aftermath either.

RE: Life expectancy of microprocessor-based protective relays (IED)

David, have a look at this:


It is being entertained and there are POCOs that are more even more optimistic then the writers.

In terms of single breaker designs, I think PGE got it right initially- they are still being built all over the world. BAAH is over-rated in my book :P

EMPs- not sure how credible the concern is- but I would imagine you would have mach larger issues if that truly was to happen. FWIW, there is a rumor that the 1965 blackout was cuased by EMPs from UFOs.

RE: Life expectancy of microprocessor-based protective relays (IED)

Quote (The microprocessors are not like the EMs we took out of service at 75 years. )

It is like the human beings of new generation with fast food culture and the older generation of traditional (ethnic food) food culture. even though the life expectancy has improved now, the modern generation is much more sick as compared to the older generation.

I find some similarities between the relays and the humans beings!

RE: Life expectancy of microprocessor-based protective relays (IED)

I do as well- I agree with your analogy.

RE: Life expectancy of microprocessor-based protective relays (IED)

A few years ago I was asked to set up and test a replacement ABB/West HU (EM-87T) Relay to replace a unit deemed failed by others. I was told the cost was $9k for the relay alone. This was at a nuke plant and I believe this was cheaper than redesigning a new scheme, with all of the approvals required.

RE: Life expectancy of microprocessor-based protective relays (IED)

If I had to set some kind of industry policy for lifecycling IEDs - which I'm surprised NERC and other regulators haven't done yet - I'd go with a cycle between 5 to 10 years. I would like to see the manufacturers make the IEDs more 'rackable' - being on tracks or whatever, with a 'plug in module' for ALL connections to the relay. This way you could swap out an IED that has already been bench tested and commissioned with settings in about 2 minutes.

I think this discussion naturally leads into discussions regarding maintenance cycles for IEDs as well. I think the industry will start moving towards ditching maintenance on IEDs and just swapping them out for fresh models at some regular interval.

RE: Life expectancy of microprocessor-based protective relays (IED)

For sake of discussion, my problem is that I have an installed base of GE IED's. they range in capability from SR-369 (Motor protection) up through the UR series for feeders, transformers, motors,and one sad old generator.

Age on these range from late 1990's to 2005.

The present software offered by GE for current relays does not communicate with 1990'vintage SR series installed in a facility I 'inherited'. I had to get an older DOS-based program and run it under an emulator to deal with these.

Some UR series installed in the early 2000's are a different hardware and firmware revision than the newer versions we installed in 2005. The UR platform is modular but modules do not interchange from the older to the newer versions, or vice versa.

Since I'm now dealing with a large company with a wide installed base of devices, we're looking at codifying a maintenance and replacement policy.

old field guy

RE: Life expectancy of microprocessor-based protective relays (IED)

From above, at least one relay manufacturer makes their relays that are change able with plugs. We don't use them because they seemed flimsley and not to our standards.
So we use test switches.

As far as problems with GE software, and other also, That's exactly one of the reasons we don't use GE relays.
I can still plug a dumb terminal into any of my standard microprocessor relays from the 80's through a new one.
That's not to say the versions, or microprocessor are the same, but I can still communicate with all of them.

And here is where I say, price is not everything. And you need to make your management understand that.

Besides, old dos requirements are a new securty feature from young hackers.

RE: Life expectancy of microprocessor-based protective relays (IED)

Though I am motorhead/generatorhead, I found this thread quite interesting and informative.

Thank you all.


RE: Life expectancy of microprocessor-based protective relays (IED)

Below is from a paper by PSRC on end of useful life estimation:
Quote "The IEC describes useful life as “the time interval beginning at a given moment in time, and ending when the failure intensity becomes unacceptable or when the item is considered to be unrepairable as a result of a fault (IEV 191‐19‐06) [1].” Therefore, according to this definition the end‐of‐life is when the failure intensity becomes unacceptable or when the [recovery/repair] time is considered to be unacceptable as a result of a fault. Some examples for end of life include the loss of life of capacitors (loss of capacitance because of electrolyte drying and leakage), and loss of semiconductors (mainly ICs) that degrade because of thermal, vibration and humidity. The ability to determine the end‐of‐life will better prepare the utility for a successful asset management strategy as well as bolstering their rate case application." Unquote.
It seems not easy to give a figure like 20-years with the dynamics of technology and various factors involved in assessing the end of useful life for numerical relays.
Most of the vendors offer 10-years warranty and hence, what we can definitely say is 10-years as a minimum. Beyond that, every utility needs to evolve their own strategy it seems.
The above technical paper can be downloaded from

Rompicherla Raghunath

RE: Life expectancy of microprocessor-based protective relays (IED)

I would create an upgrades group at your company. Start quoting upgrades and point out the manufacturers are starting to not support this product. This will generate fear in your customers which will generate upgrade projects. Which will generate a revenue stream for your company. Everyone wins and you can use your expertise in selecting a better product to support your customers with in future.

RE: Life expectancy of microprocessor-based protective relays (IED)

Are you guys changing out the electrolytic capacitors? That is what fails on first gen microprocessor relays. At conferences this was pointed at as the week link. My former employer would change them out on ge relays.

Once the relays get that old, you probably want to change them out to match the system and stock in the warehouse.

RE: Life expectancy of microprocessor-based protective relays (IED)

If someone is buying the new relay or ordering the equipments containing the protection relays, it is better obtain the life cycle and obsolescence strategy from the relay vendor.

Sometimes, the offered generation of relays series may be at its final stages of obsoleting by the manufacturer. But, there may be some inventory left with them and they need to clear it out. So the relay vendor may give discount to the main equipment manufacturer. But the end user suffers due to this. If it is a long gestation project, before you commission, the relay vendor may tell you that now these relay series is obsolete even during the commissioning. Thus everything they supply (spares, service etc.) on that relay will be at premium for that relay.

It is like writing the obituary before the child is even born!

So to avoid this, the buyer should always ask the vendor to submit the obsolescence strategy showing in the bar chart, where the subject relays are located.

Normally, these are in four stages, like,
a) development & trial run stage (this is where lot of troubles coming in the product)
b) People should buy when the product is in the initial stage of stabilization of the product.
c) Matured stage (stabilized stage, where the relay is well established)
d) Phase out stage (where the manufacturer will be planning to develop a new series of product and planning to obsolete this series. One should not buy the product at this stage)
e) Obsolete, but manufacturer has not declared, and waiting to clear out his inventory (this is a very problematic area, where the un-suspecting customers fall to the trap!

RE: Life expectancy of microprocessor-based protective relays (IED)

The end user selects the relays. Anything else is madness.

RE: Life expectancy of microprocessor-based protective relays (IED)

You always take a risk on anything you buy. You look at the company and evaluate the history and make a decision if this is a risk you can take.

If you have had poor results from buying from a company, and you keep buying from them because they are cheaper, or the salesperson takes you out for lunch, then you are foolish.

On the other hand, you should look at buying from two or more manufactures just so you know you have a backup source if your chosen company fails.
I sort of do this.

No we do not replace capacitors. We replace the whole device. The cost of having someone sit down and un-solder, and re-solder another one is more than a replacement or the failed devices.

RE: Life expectancy of microprocessor-based protective relays (IED)

obtaining the obsolescence strategy at least gives you a clue, what model not to buy, if the offered model is already in its later stage of matured stage of the product.

This approach will protect you (sort of an assurance) to some extent. You must request this from the vendor during the bidding stage itself.

I am not talking here only for the protection relays. This is also applicable for few other systems, like PLC systems, PMS/ECMS, switchgears etc.

May be not that relevant when it comes to totally custom deigned equipments, such as transformers, distribution boards etc.

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