Basler DECS-200 Not showing/sensing field current, need help

[BigTom209]

I'll keep this short and simple because this got tossed on my lap tens of minutes ago and hopeful someone on here may have some insight


We are in the process of commissioning a new hydro generator, and the vendor supplied (and apparently tested) DECS-200-IC is not displaying or seemingly sensing the field current so we are unable to go into manual mode for control. The consultant on site hasn't seen this issue before, no one we've talked to at Basler really could tell us much besides send it in for testing/repairs, they did have us take the unit apart and inspect for any noticeable problems ie blown ICs or possibly missed solder joints but everything looked fine... we're in a bit of a bind either stopping commissioning or figuring out if something is wrong in the setup or wiring or something.

Does someone on here have experience with these DECS-200's or can give me some idea of things to test/troubleshoot before we send the crews home and send this DECS back to Basler? Maybe it's something simple I don't know... I just downloaded a copy of the manual and am going down to the unit to start reading/trying to learn myself. Any guidance or advice is appreciated

Thanks
Tom

 

[BigTom209]

So looks like the field current and voltage is an internally calculated thing... so if the input wiring is assumed for the moment to be correct, there is nothing we can do for setup is there?

We did notice something, I saw in the manual "Exciter Field Rated Data" and that you could enter in a value for both field voltage/current to calculate the field resistance, right now with the numbers entered it calculates a field resistance of about 18.7ohms, but we measured 16.2ohms, so that seems a bit off but we're not sure where to find the information on the proper field voltage and current... there is a twin unit that was upgraded last year and we had a really good exciter guy do the setup, the values were simply copied from the sister unit to this one as they are identical.

These units are over 80 years old so we're combing thru some old records trying to find more specs...


Is there anything we can do in the program for this field current? Like... what inputs exactly does the DECS use to calculate it and is there any settings for those inputs we need to look into?


Again, sorry for the newbie questions... I've now got about 1hr experience looking into exciters!

 

[catserveng]

This is from the version of the manual I have with me,

Field Current and Field Voltage
These signals are sensed internally. The field voltage signal is used for field overvoltage protection. The
field current signal is used for: off-line and on-line overexcitation limiting, auto-tracking, and field overcurrent
protection

As I remember these reading are measured at the PWM power stage. I have run into this before during a field retrofit, the old system had a field contactor installed that had opened up during initial testing at a fairly high load, causing the PWM power stage to fail.

How are you getting your regulator operating power, from a PMG or a separate source? If from a separate source, did you install an IRCM module? The newer regulators have quite an inrush when powered from a non-PMG source, and in some cases it has caused problems with the regulator.

Have you made sure you are getting power input, as measured at terminals C2, C3 and C4? Is your input power configured correctly? Meaning does it match your actual power source. Remember you have two power sources to this regulator, the control power which powers the "brain" and the operating power, that provides power to the PWM power stage to drive the field output.

You mentioned you had measured the field resistance, did you measure it at the regulator field terminals or at the exciter? You should measure it at both and make sure they are as close together as possible, usually within about 2 ohms from my experience.

Not sure who you have been talking to at Basler, but if you can get a hold of either Terry Gaines or Bill Rainy, they both have a lot of experience with these regulators.

Hope that helps, MikeL.

 

[BigTom209]

MikeL,

The entire reason I joined this forum was because I was google searching DEC-200's and came across some of your posts helping others with the same unit! And I hoped like hell you'd reply back cause you seemingly know them very well! So kudos and many thanks to you for chiming in

It's getting late here right now, and I was just having a beer with the other guy I'm working with from site drowning our sorrows over this unit kicking our ass all day when I got the message you had replied. The other guy working with me actually has a really good understanding of the electrical side of things and knew exactly what you were talking about and the answers to your questions so first thing in the morning I'm going to log in and hand him my laptop to reply. So if you have chance, please check back in with us if you can.

Thanks again

 

[waross]

Welcome to Eng-Tips BigTom209.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[BigTom209]

I'll try to answer some of the questions, buddy is down at the unit they are continuing at the moment with the exciter in auto, they setup/tested the protection relays to trip the unit if there is a over/under voltage if the exciter goes squirrely for some reason.

This is a newly installed DECS, these units are old house units for the hydro plant and pushing 80-90 years old but they've been upgraded with a new control system/governor etc. This is the 15th unit that's been commissioned up here so we are confident in the controls/protection/governor but these 2 baby house units have the DECS-200's which are different than the others so no one has any real experience on them. But, again the sister unit sitting beside this one we're working on was tuned by a very capable exciter guy who worked for us, unfortunately he left the company for personal reasons a couple months ago so we're kindof flying blind on this one

I know the Blaser guy we were talking to whom asked us to open up the DECS and check for any noticeable damage mentioned the PWM circuit and had us looking at a specific groups of IC's, so guessing like your example where the PWM stage of the board failed they were thinking along the same lines. But again visually nothing appeared out of the norm physically, and I used to do board repairs at my old job so I even manually checked all the legs on the IC's to see if they happened to have a bad solder joint but nothing.

I believe we get the PMG from a separate source and yes have a IRCM module installed... electrical buddy talked about that some last night and pretty sure that was the answer

Buddy also went down to the unit this morning and checked the power inputs as you mentioned, and I believe we did check the configuration but will have to confirm. I know buddy said he did go over your message this morning and went down the with meter and said everything metered out fine

Field resistance last night was done at the exciter, but rechecked this morning between terminals and exciter and they were nearly identical readings again around 16.2ohms

I'm not sure the name of the person we were talking with from Basler, wasn't me on the phone at the time. He did seem to know his stuff but basically over the phone couldn't think of a solution, which is why we are now scratching our heads trying to see if there is by some chance something we missed




And of course they no longer sell these DECS200's anymore so we're kindof hooped there. Project started 5+ years ago so even though this is the first time they have been powered up since FAT back in 2011 we can't get a replacement currently. And we don't want to step up to the DECS250 simply because we have one house unit already in operation with the 200 so spare parts and familiarity it's nice to keep them the same.



Keep the ideas coming if you can think of anything else we can check or might have missed! It's all good info and well recieved

 

[BigTom209]

Well, we've basically come to the conclusion it's got internal issues.


So next step, do we pay the big bucks and upgrade to DECS250, or try and hunt down a NIB old DECS200? I can find used ones on Ebay and other sites, but new ones are few and far between. Does anyone on here know where WE CAN LOOK FOR a "spare" somewhere that's NIB and no longer needed.??

 

[catserveng]

Depending on the size of unit you have and complexity of the controls maybe the DECS150 is an option? I have done a few retrofits with these lately on some larger recip engine driven projects and a small (1500 kW) hydro on a sewer plant outfall.

The DECS150 has a lot of the features of the DECS200 in a smaller and less expensive package, drawback is it doesn't have the front panel controls/interface except for some LED's but have been able to test, tune and commission via a laptop with a pretty minimal learning curve.

Have you tried doing a simple bench test on the regulator to see if it is in fact a problem?

I use a 150 watt 130V light bulb connected to the field output, you'll need a power source for the control power and the operating power. I use a variac on the sensing and set the regulator to single phase sensing. The digital AVR's are a bit harder to bench test than the older analog models, but if you are careful it can at least give you an idea if the regulator will output a field signal.

If you can find an older Basler SSR or SR4 manual online it has a diagram of a similar test setup and procedure. You have to add another power source for the controls, and the results are not real smooth, but I have found if the regulator will drive a light bulb dim to bright and follows what you're doing with the sensing voltage input it should work if everything is properly setup.

Basler usually does a pretty good job on repairs, and the regulator is new enough there shouldn't be parts issues. But they do seem to want to push folks to the DECS250 every chance they get.

I have a few customers with spares, but none are willing to let them go. They do show up new on ebay once in a while, of course not usually when you need them.

Regards, MikeL.