AC pro's, Utility Relay company problem.

[cornbread]

Background we retrofited a bunch of our 480 volt draw out breakers with AC Pros microcontroller solid state trip units. We are currently having to replace them as they arbitrarily change their trip settings (software version 5.1). Luckily for us the trip setting defaulted to a lower setting causing a unwanted trip. My questions to the forum are

What do you think of microprocessor trip devices?

Any one else experiencing problems with the AC Pros?

What trip device would you use in facility?

 

[zog]

Background we retrofited a bunch of our 480 volt draw out breakers with AC Pros microcontroller solid state trip units. We are currently having to replace them as they arbitrarily change their trip settings (software version 5.1). Luckily for us the trip setting defaulted to a lower setting causing a unwanted trip. My questions to the forum are

Really suprised to hear about this, I have never seen an AC PRO fail. I will be doign some homework on this one. When did you purchase them? Black or Silver?

What do you think of microprocessor trip devices?

Cats meow. Now some OEM's have had some very serious manufacturing issues and recalls, guess that happens. And the older generation that used dials/switches would default to the minumum setting if they were in a dirty envoronment but they are all better than the old Electro mechanical devices, we see thos with around a 30% failure rate based on tens of thouands of tests.

Any one else experiencing problems with the AC Pros?

Never, and I have dealt with thousands of them.

 

[cornbread]

They were purchased and installed earlier this year. I think in April.

 

[wdemos]

Any one else experiencing problems with the AC Pros?


Wow, that is interesting; we must have hundreds of these retrofit units at our facility and haven't heard of any issues.

I would contact URC to get some feedback on this issue.

 

[zog]

They were purchased and installed earlier this year. I think in April.

Metal box or black plastic?

 

[zog]

(software version 5.1).

Is that 5.10 or 5.01? Big difference.

 

[TxEngr]

We've been retrofitting GE AK25 breakers with the ACPros with no problems at all. Some are new enough that they haven't been through a test cycle, but we haven't had any issues with them at all.

Microprocesser based devices is the way to go. There have been some problems in the past when they first came out (ABB units) but they are very reliable now. Plus, they normally tell you when they have a problem - something an electromechanical device won't do.

TxEngr

 

[zog]

I will get some hard data but I would estimate we have done around 5-10,000 AC PRO retrofits and have not heard of a single failure like this. Cornbread, was this a single failure or several? Was were the conditions during the failure? I find it very odd this happened, there has to be some logical reason.

Now I know the URC guys very well, and they never argue, say you have a problem, bam, you get a replacement sent out no questions. They are helpful to a fault perhaps. I suspect there is something else at play here, but who knows, could be a bad production batch you got.

 

[zog]

There have been some problems in the past when they first came out (ABB units)

Funny you say that, I assume you mean Power Sheilds, and they are some of the most reliable ones ever made, in fact, one of the few allowed on nuclear safety related breakers.

The most failures (Solid state) I have seen are GE MVT+ and Siemens STIII. The MVT+ has had several recalls.

 

[cornbread]

We had three failures all on Hardware ver 4.7 and firmware ver 5.1. We have been talking to folks at AC Pro and they were aware of the problems. According to them they thought they had tracked down all the defective units. Here is what they said the problem was "The problem was a lookup table index pointer in the firmware that became corrupted."

Given the severity of the problem I would have thought they would have had some sort of techinical advisory on their web site.

How does that old song go "if it weren't for bad luck I would have no luck at all".

 

[cornbread]

Some additional info I just recieved from the engineer taking care of replacing the units.

We have 21 ACpro trip devices on site, 17 of them have firmware version ?5.10?. We have had 5 spurious trips out of 3 different trip devices.

As mentioned in my previous post; this is a known issue to Utility relay company. They have stated that when the breaker is run at low current (<12% ct ratio) that firmware versions 5.10, 5.11 and 5.12 could have a ?problem was a lookup table index pointer in the firmware that became corrupted.?

This problem manifests itself as the LTPU, LTD, STPU, STD, etc all reset to their lowest values. The new value of time pickup could be less than the load on the breaker, and the breaker trips on long time after a period. The reset also turns on unbalanced pickup at 50%

As I stated, we had 5 trips, because of this firmware problem . In one case, a breaker reset it?s LTPU to 160 while it was under a 200 amp load. We have also had a pair of trips because of the unbalance pickup.

The problem doesn?t seem to be isolated to breakers at <12% load. We had a breaker trip at 30% of its CT ratio.

 

[zog]

OK, got scoop. There were a few of these that shipped with this software version, the issue was only with units using communications. URC contacted everyone that had purchased these and replaced them for no cost. I guess cornbreads slipped through the cracks. Most of these went to the flooding in the Midwest.

If you have any concerns you can call URC with your serial numbers off your trip units for verification. I have ran all the serial #'s from the ones we installed during that time period and did not have any of those units.