Transformer oil sampling under full-load conditions?
Transformer oil sampling under full-load conditions?
(OP)
All, we've been reviewing our safety procedures and standard practices for taking oil samples on our pad mounted 4.16 kV/0.48 kV transformers. Is there any reason why the sample should be take under full-load conditions?






RE: Transformer oil sampling under full-load conditions?
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Transformer oil sampling under full-load conditions?
The sample should be taken on load or very soon after de-energising to ensure that contaminants including water are in suspension, rather than settling in the tank bottom. Short of attaching a load bank at each transformer it might prove difficult to apply full load in any case.
Regards
Marmite
RE: Transformer oil sampling under full-load conditions?
Pad mounted transformer oil sampling with the sample valve inside the cabinet is one of the toughest tasks to comply with the 70E.
Best solution, if you are the owner, is to install exterior sample valves, there are several aftermarket modification kits available because of the 70E issues.
RE: Transformer oil sampling under full-load conditions?
I may be out of line on NFPA70E as it is not applicable in the country I operate in, if so I apologize in advance.
My understanding is that where the work is done by qualified persons related to the task, exceptions can be made to the Energized Electrical Work Permit provided there are appropriate safe work practices (Article 130.1 (A)(3))pg 24 of 70E.
If I was doing the work, I would start with the Hazard / Risk Evaluation Procedure on pg 107.
Most industrial transformers have enclosed metal terminal boxes, in this case approach boundaries are not an issue as there are no exposed conductors.
Where LV terminals are exposed, they are usually taped up, thus reducing the risk. At 4.16kV the RAB would be 660.4mm.
If any of the terminals are exposed, the Approach Boundaries of Table 130.2(C) come into play.
RE: Transformer oil sampling under full-load conditions?
RE: Transformer oil sampling under full-load conditions?
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Transformer oil sampling under full-load conditions?
EastB