PFC equipment not registering current use despite working 2

[seanleed]

Hi all,

We have a lot of PFC equipment on site, but one of them, despite working away does not show any current use on its supply meter.
This is a 1MVA Schneider Electric PFC with capacitors and inductors internal. It is fed through a Masterpact MTZ2 breaker at 400V. Neither the separate power meter or the Micrologic controller on the masterpact show any current flowing. I have put our Fluke PQA on the outgoing tails and it also doesn't show any current use.

The meters on the two sections on the PFC were showing 400ish amps on each side, so 800A, but still nothing showing on the supply side.

Can anybody tell me why? It's doing my head in.

 

[thermionic1]

Check for CT shorting screws (or shorting devices) still installed on a terminal block that feeds the power meter. New equipment is generally shipped with shorting devices in place and need to be removed once the circuit is complete.

 

[waross]

My first reaction was;
"Fix the meter."
I think that Thermionic has given you the most probable cause and fix.
By may be well to check the integrity and continuity of the CT field wiring before removing the shorting link or screw.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[che12345]

"..It is fed through a Masterpact MTZ2 breaker at 400V. Neither the separate power meter or the Micrologic controller on the masterpact show any current flowing. I have put our Fluke PQA on the outgoing tails and it also doesn't show any current use"

I have the following opinion for your consideration.
1. You had used i) separate power meter, ii) Micrologic controller on the masterpact and iii) Fluke PQA meter ... These are respective instruments having their own CT.
Note: Ensure that the Fluke PQA meter CT clamped over the main cables, NOT on the secondary of the panel CT.
2. Observation from above 1., it may? NOT be that the measuring CT shorting link is not removed, wire open circuited or the panel meter is faulty.
Note: More likely the pf regulator is faulty or not properly set, i.e. CT/bank ratio k-factor, cut in/cut out pf setting, step ratio 1:1.., or a constant pre-step setting etc... The unit is NOT in operation !
3. It is a 400V 1MVA PFC with capacitors and inductors internal, NOT a small low cost unit. Strongly suggest call the OEM for assistance immediately, if heavy penalty is being imposed due to running on low pf.
Che Kuan Yau (Singapore)

 

[seanleed]

Thanks all,

I forgot to mention that i have checked the CTs are physically there, they are not shorted, they are wired correctly, in the correct orientation and I have continuity to the meter. I have swapped the meter with one in the panel next to it and still nothing. The CTs are wired the same as others in the panelboard (which show current use) and the PQA CTs are on the outgoing cables.

@che12345 we have no reactive power penalties as we are supplied at 11kV and have our own HV distribution network, but obviously we are still paying extra if the PF is low as we are paying for our own losses.
I'd never thought about the meters in the unit itself being set with the wrong ratio, I'll try and have a look into that today, thank you.

 

[Parchie]

Assume that the meter is fine. Check if the PFC unit is really "working".
My experience in my other life was that the PFC unit was set wrongly; the PFC unit inserted more capacitors for a certain power factor resulting to over-correction. Then, the contactors were pulling in and then dropping out quickly as they kicked in. The fix was to divide the capacitor into small values at the latter steps and transfer some to the first steps.

 

[che12345]

I have following additional information your your consideration.
1. I presumed that if there is NO current, the Unit is NOT in operation.
2. Please read the Regulator installation and setting manual carefully. Some basic I had covered in my earlier posting. Pay particular attention on the location of PT and CT and on which part of the system you are improving.
3. Attention: Some Regulator takes the Current from phase A and Voltage from phase AN. Others may take the Current from phase A but Voltage from phase BC etc... Observe the relative polarity.
Che Kuan Yau (Singapore)

 

[seanleed]

Been back at it this morning. Turns out to be a really simple solution- it's the wrong spec.

The whole thing would work as it should if the spec was correct, and during auto initialisation the meter reads current spikes as the various steps are switched in. After this is goes back to no current use. A bit of further digging through the setup and I discovered the minimum step is 100KVAR, and our current reactive load is only 63KVAR, so it's never reaching a stage where it needs to switch anything in.

So, if anyone has a need for a 1MVA Schneider Electric VARSET we've got one doing literally nothing .

Thanks again for the pointers of things to check over.

 

[waross]

The meters on the two sections on the PFC were showing 400ish amps on each side, so 800A, but still nothing showing on the supply side.

Isn't that about 554 KVAR?
The whole thing would work as it should if the spec was correct, and during auto initialisation the meter reads current spikes as the various steps are switched in.

our current reactive load is only 63KVAR, so it's never reaching a stage where it needs to switch anything in.

The previous statements, taken together, do not work and play together well.
"so it's never reaching a stage where it needs to switch anything in.
Would that be because you already have over 550 KVAR of correction on-line?

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[seanleed]

I was wrong with the meters. It's not metering each side, they are both fed from the same CT at the main LV input to the panel. So it was 400A in total.