BULLETIN FROM

Dry-type transformers generate heat and cooling air must be allowed to circulate through the passages/air ducts around the windings. Keep cooling air vent openings clear to allow full and free flow of air-verify adequate room ventilation.

Dry-type units can be cleaned by blowing with dry, low pressure (50 p.s.i. max.) air or by vacuuming dust & dirt that will restrict ventilation and cause overheating.

Loose connections will create resistance and heat leading to possible failure. Check and tighten all connections.

Megger winding insulation for resistance - test high to low to ground, particularly if the unit has run hot either normally or due to restrictions of the winding cooling air ducts.

On oil-filled transformers, check oil level and temperature regularly and, test oil for dielectric strength and dissolved gases (250 kva +). This will give information on possible deterioration of the windings, insulation a/o oil.

PCB-filled transformers or other electrical apparatus such as capacitors should be labeled accordingly and have sufficient dyking installed to contain any leakage from the transformer or other device.

Pad or floor-mounted transformers should be adequately protected from damage from such things as vehicle collisions, etc.

Leaks at insulators or on the canister should be repaired as soon as possible.

Electrical/transformer rooms should not be used as storage rooms. Entry should be restricted to custodians a/o maintenance personnel.

Transformer rooms should be kept clean, cooling air filtered and concrete floors painted to keep dust to a minimum.

Caution: All work should be performed by qualified personnel.

Another often unnoticed area/group of objects in some schools are the step-down transformers.