Voltage Variations

[humble2000]

Customer is fed through a 2.5MVA transformer with three 400HP DC Drives as large loads and couple 50-100HP HVAC motors, some small AC drives and SCR heaters. Ofcourse there is a office building and computer,fax machine and scanners.
I have attached the flicker caused by a load at the main service.
I was told that SMPS can cause this voltage variations.
I appreciate any comment on this.

 

[ramsy]

This makes a nice troubleshooting excercise in hunting.

If no one is going to recognize the patern for you, and solve the mystery, you could start heading down stream with your scope.

Try logging each feeder seperately until you find the right panel. You might log a few branches before you find your culprit. If your scope permits logging a group of circuits in parrallel, that may narrow it down faster.

BTW, what problems is this flicker causing?

 

[humble2000]

The flicker is not causing any problems,as a matter of fact Pst and plt are within the acceptable levels, I am just curious what can cause this voltage variations on the main service. There are 10 feeders off the main and during the two weeks period ,this only happened 3-4 times with no time pattern. I just need to know if you have an experience with the type of load that can cause this, and eliminate the other loads that can not behave like that.

Thanks

 

[wirenut1980]

If I am seeing your drawing correctly, it looks like you have some higher than normal voltage peaks ~490 V and some higher than normal current peaks. Sounds like something is contributing harmonic currents and voltage which you are seeing at the main. You just have to find the culprit(s). There are many non-linear loads that can cause these distortions including SMPS, all of which are listed ad-nauseum on this forum.

 

[humble2000]

The system is 600/347V.
has anybody had experince with loads that can create this type of voltage variations?

 

[ramsy]

Hanging out on this forum during the last year, I've seen more than a handfull of remarks that struck me as originating from extraordinary and specialized experience. But, no one seems to engage them further, and the people rarely return to post again. I noticed a PQ expert that posted here a few weeks back, so they could still be lurking.

It's quite possible some specialized experts will not participate after attempts to market themselves or post contact info. was deleted, but they still might be found privately.

Holt's April newsletter Electrical Experts Needed announced a special Experts forum for this, but nothing became of it.

So, if you search around, and find a dialog by the PQ expert that meets your needs, try contacting that person privately thru their profile. Some of these people do connect and reciprocate privately with members. Like Hogan's hero's in the Nazi camp, it's not impossible to get help from, or to the people getting deleted.

 

[catchtwentytwo]

I thought Dranetz-BMI and/or Electrotek Concepts once looked at (and commented) on emailed PQ waveforms.

I think you sent them to waveform@electrotek.com . There's more detail here http://www.pqsoft.com/waveforms/index.htm

 

[ramsy]

There's more detail here http://www.pqsoft.com/waveforms/index.htm

Catchtwentytwo, you have saved the begging bugger with one of the sweetest PQ resource I've seen. Shultz yells "Ausgezeichnet!" and Hogan has promoted you to 2nd Lieutenant.

 

[catchtwentytwo]

Hanging out on this forum during the last year, I've seen more than a handfull of remarks that struck me as originating from extraordinary and specialized experience. But, no one seems to engage them further, and the people rarely return to post again.

Roger,

It is a shame that some interesting threads often "die" and we never hear what the final result was.

I've found that the Electrotek and Dranetz-BMI folks (like most of us) love a good mystery and are more than happy to offer opinions.

Too bad access to the PQSoft Power Quality Waveform Library is by subscription only. I've tried their TOP, The Output Processor? but found the learning curve a little tough. And dependent on the format of the PQ data.

Regards,
John H

 

[ramsy]

Too bad access to the PQSoft Power Quality Waveform Library is by subscription only. I've tried their TOP, The Output Processor? but found the learning curve a little tough. And dependent on the format of the PQ data.

Yes, I see that too, the data can be displayed and filtered in endless ways. It seems comparing new PQ data to any signature library in TOP demands identical settings between new vs library data. I hope the PQSoft libraries describe what settings to use.

Subcriptions to a well maintained library of PQ signatures, may not be a bad thing. Valid or repeatable results may not happen without a revenue model for peer-review and technical support. What's seems unfortunate to me, is how internet forums ignore revenue models as they rely on generous acts of expert time & charity, without reciprocating even a link for their effort.

Without allowing experts some referral to their business, the forums seems to be getting overwhelmed with a desperate public that demands free technical support. Many new members are dangerously under-qualified and refuse when asked to get a code book. When they seem to be someone elses exploit, or illegally operating from free advice, more experts may get disgusted, and prefer selective lurking, to engaged participation.

 

[humble2000]

the forums seems to be getting overwhelmed with a desperate public that demands free technical support. Many new members are dangerously under-qualified and refuse when asked to get a code book. When they seem to be someone elses exploit, or illegally operating from free advice, more experts may get disgusted, and prefer selective lurking, to engaged participation.

Well,
I think the purpose of every forum is to share experience and knowledge. This is a very cheap way of looking at the subject of asking for an expert opinion" desperate public that demands free technical support".
Obviously, this information is not in any code book or technical library.
I have always been grateful of people who share their knowledge to new members like myself and give me the courage to share what I have gained with other people to build a better world.

 

[robbietan]

looks like the DC drives could have caused those variations that you've picked up. BTW, what type of equipment do the DC drives run? Are they 6 or 12 or 18 pulse? And you can check if they have a built-in reactor located at the line side. If there is none, installing one between the supply and drive will lessen those variations.