Flash memory (EEPROM) reliability in protection relays
Flash memory (EEPROM) reliability in protection relays
(OP)
Does anybody have any thoughts / data or anthing on the reliability of components in modern day digital technology power system protection relays?
I'm particularly interested in flash memory (EEPROM) reliability and electrolytic capacitor reliability.
We have already seen EEPROM problems in two different manufacturers relays (who shall remain nameless - it is the OEM component that is the problem, not the relay itself). Is any particular EEPROM technology better or worse than any other? What affects their reliability - electric fields, mag fields, heat, temperature cycling, number and frequency of re-programs, etc.
I'm particularly interested in flash memory (EEPROM) reliability and electrolytic capacitor reliability.
We have already seen EEPROM problems in two different manufacturers relays (who shall remain nameless - it is the OEM component that is the problem, not the relay itself). Is any particular EEPROM technology better or worse than any other? What affects their reliability - electric fields, mag fields, heat, temperature cycling, number and frequency of re-programs, etc.
Bung
Life is non-linear...





RE: Flash memory (EEPROM) reliability in protection relays
These links do not directly address the matter, but do discuss a noteworthy false operation attributed to an EEPROM.
http://www.ameslab.gov/esha/Lessons_Learned/Blue_Alerts/980204b.htm
http://www.nrc.gov/reading-rm/doc-collections/gen-comm/info-notices/1997/in97082.html
RE: Flash memory (EEPROM) reliability in protection relays
Bung
Life is non-linear...
RE: Flash memory (EEPROM) reliability in protection relays
We have been replacing them with a different brand, and those seem to work fine.
The articles busbar reference are for EPROMs, not EEPROMs.
RE: Flash memory (EEPROM) reliability in protection relays
Lewish -- So noted. My apologies for the mistake.
RE: Flash memory (EEPROM) reliability in protection relays
Reliability of flash (and EEPROM, for that matter) is affected by temperature, noisy power supplies, number of programming cycles, manufacturing quality, and other factors. If the power rails to the memory aren't clean (how clean are they during switching of this relay?), large enough (usually negative) spikes could cause problems by causing current flow in the substrate.
Eletrolytics caps tend to dry out, affecting their performance. This is accelerated by operation at high temp.
RE: Flash memory (EEPROM) reliability in protection relays
The "relay" is essentially just a permanently powered up computer taking in current and voltage analogue signals, doing some fancy footwork inside DSPs, and then issuing a "trip" command if necessary via some small traditional style electromagnetic relays.
Clean power rails could be a challenge in the electrically hostile environment of a substation control room - we just have to rely on the relays being designed with that in mind. But I have seen a relay die from electrostatic discharge when I plugged my laptop into it - and the laptop survived.
Manufacturers tend to get sniffy if you mess with the insides of the failed relays before they have a chance to get their hands on them. Take it out of the case, and they will try to blame the user for doing some damage, and they are not at fault- their relays never fail!. And anyway, we aren't digital electronics experts - I won't necessarily know a flash memory chip from any other kind of chip even if it jumped up and bit me.
Bung
Life is non-linear...
RE: Flash memory (EEPROM) reliability in protection relays
Bung — Interesting point; that most often is probably the case. FWIW, one producer informally admits never having charged a nickel for returned, damaged-relay repairs, although there service guys admit that some come in absolutely incinerated, typically from lightning.
RE: Flash memory (EEPROM) reliability in protection relays
Back in those days the company I worked with had time to try to do basic fault finding inside the transistor logic.
In this particular instance the manufacturer admitted this was a fault that they had seen in these relays only once we had pointed it out to them.
cheers :)
RE: Flash memory (EEPROM) reliability in protection relays
Lewish, What you stated is disturbing to me since we use EEPROM chips from microchip. I have seen a blanked E^2 in one field return. Would you care to elaborate on a part number? (without checking, ours is 93C46, I believe and 93C66-might have 93 screwed up in PN)
RE: Flash memory (EEPROM) reliability in protection relays
buzz — That is good advice. I wonder if that is what happened here.
http://67.115.161.42/pwr/nerc.dawg-96.15brkr.htm (!)
RE: Flash memory (EEPROM) reliability in protection relays
As for CE or any other certification, it really only means that a lmited number of devices got through a limited number of tests once. Relays live their entire working lives being assailed by every transient nasty a substation can throw at them. The testing only gives a modicum of assurance that they will survive in the longer term.
Bung
Life is non-linear...
RE: Flash memory (EEPROM) reliability in protection relays
The EEPROM failures are a little scary. I would hope that the relays would have some type of memory testing that would allow it to shut itself down and alarm without mis-operating.
RE: Flash memory (EEPROM) reliability in protection relays
What date code do you have?