Analyzer records 0.1 Power Factor 6

[amaminu]

I installed a power analyzer to monitor the kVARs being drawn at a Water Pumping (Booster Station) site. When the pumps are not running, I get power factor (PF) as low as 0.111 (lagging). The PF rises to about 0.9 when the station is pumping water. I am wondering why I get 0.111PF when the pumps are not running.

 

[slavag]

Hi.
Please think, you have answer in your Q.
Not pumping---not current--- continiue by yourself---
Believe me, you know answer.
Regards.
Slava

 

[amaminu]

Thanks for the quick response.
However, I want to make the following clarifications:
1)I am monitoring the 11kV incomer panel of a 6MVA 33/11kV transformer.
2) The pumping station has offices and lighting system. Even when there is no pumping going on, there is still some load being served. (The Analyzer records about 20kVA).

I hope this additional info throws more light on my previous Q.

 

[slavag]

Yes, of course.
Now Q is clear, and we think about options.
Cheers.

 

[slavag]

O.K.
It's possible becouse few reasons:
1. meas errors, 20VA is about 0.3% of nominal load.
2. big losses on the aux trafos with this low loads.
3. lighting load with serious reactive components.
Wait to others.
Regards.
Slava

 

[jghrist]

Look at measured kvar not power factor. If kvar goes up when the pumps are not running, then worry about the measurements being wrong. If not, don't worry and assume Slava's reasons are the cause of low power factor.

 

[amaminu]

Thanks Slavag, jghrist.
The kVAR values increase when the pump are running. I want to find out the source of the kVARs. If you have huge motors in the "standby" mode, does it draw any VARs?

 

[waross]

Do the pumps run at 11kV? How many KVA of transformers are connected to the 11kV system when the pumps are not running?

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

 

[amaminu]

Waross, the pumps run at 0.433kV. There are a total of 4 transformers with a total capacity of 2860kVA (2x630 + 2x800).

 

[slavag]

Hi.
I think are 4 trafo iron and cooper losses.
Are you have additional aux trafo for lighting and office.
If yes, disconnect trafos on the 11kV side and check your PF.
Regards.
Slava

 

[waross]

With that much unloaded transformer capacity, the low power factor is to be expected. It is caused by the magnetizing VARs drawn by the transformers with little real power being used.
The magnetizing VARs remain constant so as the load drops so also does the power factor.

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

 

[Skogsgurra]

"If you have huge motors in the "standby" mode, does it draw any VARs?"

Yes, definitely. That is almost all they consume when not loaded. Current is mostly magnetizing current, which is 90 degrees lagging. So, expect a very bad power factor. That is if "Standby mode" means running but with no load on shaft.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[rbulsara]

In fact I would worry if the pf of a motor in standy by mode is any more than 0.1 (or 0 for that matter) as I am wasting some watts in losses!!