Most "transformer problems" are actually born around the transformer: a poorly ventilated room, a missing oil bund, a mediocre earth. Here is what a successful installation plans for, and when.
In France, a substation connected to the MV distribution network falls under NF C 13-100 (delivery substation) and the downstream LV installation under NF C 15-100; the connection itself follows the distribution system operator's requirements (Enedis or a local DSO), which approves the single-line diagram, handles the metering and sets the access conditions. Electrical work is done by qualified, authorised personnel. Elsewhere in the EU the structure is similar with national wiring rules and your local DSO. This guide gives good practice; the applicable texts and the DSO always have the last word.
A transformer dissipates its losses as heat; the room has to remove it. The rule of the art: low and high grilles creating a natural draught, sized from the unit's losses (the figures are on its routine test report). A confined room means a rising ambient temperature and accelerated ageing: chronic overheating is the leading cause of premature failure. In a tight indoor space, forced ventilation, or a dry-type unit, should be on the table at specification stage.
Use only the lifting lugs and points provided (never sling on bushings or radiators), respect the centre of gravity marked on the nameplate and drawing, and check for impact damage at unloading. For units with a conservator, or shipped without oil, follow the manufacturer's procedure before energisation: filling, radiator bleeding, oil settling time.
Energise at no load first (the magnetising inrush is normal), watch temperatures and noise through the first hours on load, and re-torque the LV connections after a few weeks of operation. Record the starting values (temperatures, currents): they become the reference baseline for maintenance, and for spares when the day comes.
General good practice; it does not replace the manufacturer's manuals, the execution studies, the applicable standards or the DSO's requirements. Confirm each project with your design office and the factory.
For an oil-immersed transformer, yes: provide a bund or pit able to hold the full dielectric volume in case of a leak. It is an environmental requirement, cheap to build into the civil works and expensive to retrofit, so plan it from the structural stage.
Do not. The pre-energisation trio, insulation resistance, ratio and vector group check, functional test of the alarm and trip chains, takes about thirty minutes and prevents months of trouble.
From the unit's actual losses, which appear on its routine test report: low and high grilles create a natural draught that removes the heat. If the room is too confined, forced ventilation or a dry-type unit should be discussed at specification stage.
The distribution system operator (in France, Enedis or a local DSO): it approves the single-line diagram, handles or accepts the metering and sets the access conditions. Electrical work is carried out by qualified, authorised personnel.