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Thanks, now I see it. I would check all the measuring circuit, something is wrong.

First we should separate both aspects of your problem, on one hand the current unbalance and in the other the presence of harmonics. For the current unbalance part, as already said, not necessarily a phase current unbalance will result in a neutral current (only if the sum of the current...

You can always ask for a higher efficient transformer but be aware that it's cost will increase aswell, maybe considerably. I don't have USA references in this case (DOE 2016 does not apply here), but for your information, in IEC world (IEC 60076-20: Power transformers - Part 20: Energy...

Weird... I thought I had already answered to this thread... [ponder] Here it goes again: Usual storage time for N2 filled transformer is around 3~6 months, depending on the manufacturer's instruction (which you should always refer to first). For longer periods it is recommended to fill with...

As both main designs are valid, I would go with the one more common in your country/area. That way you will avoid surprises later on with the installation, maintenance and eventual need for spare parts.

For a proper analysis you will need to consider all relevant gases and not only Ethane. I recommend you to check the following standards that will help you in interpreting the DGA results and identifying the problem (if any) or ruled it out: - ANSI C57.104-2019: IEEE Guide for the...

If the neutral will be ungrounded, then you must consider a fully insulated wye, with same insulation for neutral and phase bushings (and fully insulated windings). In the standards is not so clear, because the statement is not of the form: When neutral ungrounded --> go fully insulated But...

prc, good to know, I will check it out!

Not a book, but a publication that always has something interesting to read: Transformers magazine

If it helps you to understand the switching sequence, yes it's something like that. Just be aware that the OLTC actual circuit is not like your drawing, for instance the OLCT doesn't have one switch per tap, but instead two moving contacts and only one set of switchs per phase. The two moving...

As prc said, for reactive type OLTC (usual for US), you will have a tap winding of +/-8x1.25% as the preventive autotransformer can be connected mid tap providing half tap voltages, increasing the total number of tap positions to the standardized +/-16x0.625%. So, in your example, the tap...

Are you sure that the transformer is free-breathing type? It doesn't have a rubber bag or bladder inside the conservator? That's the only time I can imagine a pressure-vacuum gauge might be of some use (In IEC world these gauges are never used for transformers with conservator, with or without...

To answer your question: If you are looking just the organizational chart (I mean the diagram), with some luck you might find some in the companies website. But I think is not the general case. To know more about a company structure and the interaction between its departments, you will need to...

Very interesting. May I ask if the existing CT/PT are connected to the MV or the LV side? Energy meters take into account not only the currents but the voltages, if the PTs are connected on LV side of the transformers and you have to choose one for the exporting meter you may introduce some...

Yes, you are correct. The impulse generator is used to test the transformer insulation withstand regarding voltage transients. In very simple terms, the generator charges a series of capacitors and then discharges them over the test subject when the charge level is right. Some resistors are...

Eduardo, remember that an unloaded transformer demands a no-load current for two reasons: 1 - To account for the iron losses: hysteresis and eddy (active component of no-load current, in phase with the applied voltage). 2 - To magnetize the core (magnetizing component of no-load current...

Hi Pgee630, In-rush current testing is not required by the main transformer standards: IEC 60076 and ANSI/IEEE C57.12.00, not even as a design or special test. Hope it helps.

Check this out. It gives a pretty comprehensive guide for all kind of field testing for arresters. Hope it helps.

Very strange, I cannot see anything in your circuit that could cause it. The MV cable lenght (10 m) is too low to produce the 20 kVAr measured, I've made an aprox calculation and you would need a 2.5 km cable to produce that value (and I'm not even taking into account the inductance of the...

I would supply the single phase loads from the 25 kVA trx directly. Its a simpler solution.