Beam Pump Oilfield High Frequency Power Spikes

[MDAust]

Hi All,
I am not an Electrical Engineer so apologise for any incorrect terminology.
We have a 60 well oil field with a mixture of beam pump and LRPs - all about 20-40kW (33kV-415V transformers at each site) each with no harmonic filtering installed. There is also a waterflood with a number of subsurface and surface ESP style pumps
We have a very large oversized GTA driving the 33kV overhead power system. Proposal is to replace the big GTA with a smaller reciprocating gas driven set with a bi-fuel back-up.
We took some detailed load data (no waterflood operating) and have a base load of 650kW with a 150kW added load appearing over a 200ms period. This is occurring on average once per second. The Power Factor moves from 0.1 leading to 0.6 leading over 4 minutes at start-up but is 0.7 to 0.9 when running.
Does anybody know why this is happening - and if so, how we can fix it - has a number of experts stumped here.
If we do install the gas engine (with 415V-33kV transformers) - will it operate Ok. Supplier is talking of a load back - which will be needed for later life loads anyway. Would a mechanical or solid state load bank have any effect of the spiking load?
Appreciate any help. I will pass on any info and can probably dig out further information on the system.
Thank you.
Mark

 

[waross]

The first thing is to start checking the individual units for current spikes. Have you checked to see if the added load is real power or reactive power?
If the motors reverse on the LRPs when the stroke reverses, that 150 KW (or KVA) may be normal staring current as the motor reverses.

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

 

[jraef]

Might it be the beam pumps going into regen on the down strokes? That's a constant problem with those. You mention them not having harmonic mitigation, so does that mean they have VFDs?


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[MDAust]

Hi All,
All of the LRPs have a dynamic brake resistor and a smaller version on the beam pumps – they have the counter weight to minimise that effect. Nearly all wells are driven through a VSD/VFD.
Thank you for the replies. The overhead 33kV system was designed for 3 times the wells/load.
Thanks, Mark