Testing for harmonics

[Darkwood]

Im sending in a request to DNO for a supply increase from 200KVA to 400KVA to allow for 3 machines im bringing from other premises, all simple enough if it wasnt for the fact that these are large machines with hefty DC motors all running off Drives, although they are screened and earthed correctly i foresee a field day for Harmonics back down the supply.
Part of the information they now require is a detailed breakdown of the harmonics (only if the installation is prone to them) which the machines will create, im aware this is a specialist area and i may have to draft someone in to estimate it but just wondering if anyone has seeked and gained this info themselves and who to use, plus how to gauge the harmonics of old machinery not yet built up and running, i can only think off ringing VSD manufacturers for some info?

 

[netblindpaul]

What drives Darkwood?
How old are the machines?
Can you get a PQ analysis done before they are moved?

 

[Darkwood]

Machines 60 yrs + no traceble bumf with them but have been modernised electrically with VSD's but these are probably 15yrs old, but i'll have to go check them out as to brand as its slipped my mind. PQ analysis only possible on one but others in storage in bits, also got 3 large existing machines in factory all running with VSD's of different brands and sizes and probably another 20 <1.5kw units again various brands.... so hopfully i can have a PQ analysis done on existing installation and predict what additional will occur.
Bloody nightmare rush job and usual DNO slowing down for xmas :13:

 

[netblindpaul]

In 94/95 our servo / vs drives had front end filtration that prevented most of the harmonics "leaking", mind ours were a.c. by this time, we left d.c. servo / vs drives back in the late 80's.

 

[i=p/u]

sounds real technical guys

 

[Darkwood]

Just a tad worried the filters will have degraded over the years, but no personal means of checking this so might just play safe and get PQ analysis done as i become liable for the info i supply to DNO and if i ignore this and their transformer overheats etc it wont be good for me :sad3:, but i could leave it out as though its not a issue and then get PQ analysis when all is running that way i can just replace any filters and if need be fit an active harmonic filter in parallel at the front end although it wont be cheap.

Ps @ i=p/u...... me and paul just make things up on here it all drivel to make us sound intelligent, a bit like those skin care adverts that use 'never heard of before' scientific words to make their pound shop grade product sound fantastic

 

[Knobhead]

About the only thing I can suggest is taking PQ readings from the one working machine and work from there.

I don’t know if Paul would agree with this but it’s something I’ve come across in the past is a separate isolation transformer for each machine. This was a row of 15 machines each with it’s own 30KVA transformer, a bit of a daunting thing at the time but it seemed to work out.

 

[Darkwood]

can see your angle Tony but kinda want to avoid fitting isolation tranformers as they create harmonics themselves although not at the same scale as a VSD's with a shot filter might do, would expect as i suggested putting an 'active harmonic filter' in series or parallel at the front end busbar would be easier cheaper and designed for the job, just want to avoid all the hassle at mo of all the organising it would take to supply them with said info etc just so i can submit a form and they turn around and say they dont have the capacity available. It has history this supply and im doubtful they can increase it from this knowledge as they fitted highest available supply 10yrs ago at a cost of 12k but you never know

 

[netblindpaul]

Have seen the individual transformer thing done too.
At 15yrs old though if the mods were done correctly they may have sufficient front end filtration?