Reactor Installation 2

[Edw1n]

What are the necessary testing and commissioning required for a new installation of current limiting reactor in series with the power transformer.We are shutting down one of the transformer and restore power after installation of reactors.

 

[RRaghunath]

Current limiting reactor is quite similar to a transformer and the commissioning checklist for transformer can be applied with appropriate changes. For example, Vector group test, ratio test would not be relevant.

 

[DanDel]

Standard tests are insulation resistance, winding resistance, and optionally, winding inductance.

You should also check all of the connection resistances with a DLRO, which is now a standard test for any electrical device.

 

[scottf]

Since it's a series reactor, I assume it's air core, dry-type?

If so, there's not much to test in the field, past maybe a winding resistance test and an inductance test. You won't be able to generate enough voltage (most likely) to do a meaningful insulation test, plus, since it's a series device, the insulation rarely is an issue.

 

[waross]

The reactor insulation must withstand the same voltage to ground as the transformer. If the reactor is not disconnected for the insulation test, then the test voltage will also be impressed on the transformer windings.
An issue that is more of a problem with air core reactors than most other types of equipment is induction heating of nearby conductors. If large reactors are within several feet of a reinforced concrete wall the stray flux may cause enough current and heating in the re-bars to damage the wall.
A test that is almost unique to air core resistors is an inspection of nearby surfaces for excess heating under high current conditions. In some installations aluminum sheets may be mounted a few inches in front of concrete walls so that the flux bloom will cause heating in the aluminum rather than in the re-bar behind it.
respectfully

 

[scottf]

waross-

With respect, I don't agree with your comments on the aluminum sheets, etc... AL is non-ferrous and would not shield magnetic field heat influences.

I work for an air-core reactor manufacturer and I've never heard of such installations. Can you shed some more light on what you're talking about?

 

[waross]

scottf;
You may be right.
I have seen the aluminum sheets installed and when I asked I was told that the eddy currents set up by the flux in the aluminum created an opposing flux that diverted the flux away from the re-bar in the wall behind the aluminum. This may have been the engineering equivalent of an urban legend.
I understand that the heating effects caused by air core reactors are dependent on the current through the reactors and can be damaging during sustained fault conditions.
I do think that the possibility of heating of anything in the vicinity of an air core reactor is something to be aware of during acceptance tests.
As far as shielding with aluminum, I have only seen it used once and never saw a heavy current on the reactors. I welcome any other information or comments.
respectfully

 

[supermacc]

I would respectfully say that mr waruss is right, the screen is due to induced eddy currents. Please see fig 6 in this paper

http://www.emc.york.ac.uk/cost261/Lille proceedings/Enerpaper.pdf

.

To my knowledge, this technique is occasionally applied to screen substations installed in or near buildings with sensitive electronics, such as hospitals. In addition, to my knowledge the effect from magnetic fields on the human body is not yet well understood, so this may also be one of the reasons to screen.

 

[waross]

Thank you for the information, supermacc.
respectfully

 

[scottf]

supermacc....interesting link.

I'll need to read it in detail, but my knee-jerk comment is that I'm not sure that would be applicable for real-life applications. The magnitudes of mag field being used is extremely low, relative to a real s/s application. Also, the field shape for a bus bar is much different than for an air-core reactor.

I can tell you this....shielding mag field with AL plate for a 2000A, 4 ohm, 230 kV reactor would be a big waste of time

 

[supermacc]

Well, if you look at fig 12.5 in ftp://ftp.elteknik.chalmers.se/Publications/PhD/SalinasEnerPhD.pdf you'll see that they shielded a couple of transformers, no reactors though as fas as I can tell but I have honestly not really read it in detail. That, and some other actions, appeared to work fine. Would you mind sharing some light what your talking about? My experiences within the field is that I have a had few coffee breaks with the author when we had a university related project, so I am not questioning your expertise, I just have a will to learn new things.

 

[Edw1n]

Thanks a lot guys.These are all very helpful.One last thing is that, Do I need to do a seperate test for the power transformer before installing the reactors? According to the records from my client they have done the Zero Sequence impedance test for the power transformer previously

 

[prc]

There are two types of shielding ferrous parts (to avoid overheating and consequent losses ) from straying flux coming from windings or current carrying busbars-magnetic shielding where silicon steel is provided as a path for flux thereby preventing entry of flux in to ferrous parts. Another method is electro-magnetic shielding where a current conducting material (copper or aluminium) is provied to shield flux.The flux generates a counter current in the shield that repels the flux to source.(eg Isolated bus duct,series reactors )

Warros is right-in oil filled series reactors aluminuim shielding is generally used to shield the tank .What scottf may be refering to is dry type reactors where there is no metal container and no need for shielding.

Thank you supermacc for sharing that excellent tutorial.

 

[DanDel]

Edw1n, you should perform the full set of tests on your transformer per NETA, i.e., insulation resistance, Doble PF and excitation, turns ratio, and optionally winding resistance.