Described below are various sources of oil spills within substations. Spills from any of these devices are possible. The user should evaluate the quantity of oil present, the potential impact of a spill, and the need for oil containment associated with each oil-filled device.

Large oil-filled equipment
Power transformers, oil-filled reactors, large regulators, and circuit breakers are the greatest potential source of major oil spills in substations, since they typically contain the largest quantity of oil. Spills may be caused by electrical failure, leaks, vandalism, sabotage, or accident.

Power transformers, reactors, and regulators may contain anywhere from a few hundred to 100 000 L or more of oil (500 to approximately 30,000 gal), with 7500Ð38,000 L (approximately 2000Ð10 000 gal) being typical. Substations usually contain one to four power transformers, but may have more.

The higher voltage oil circuit breakers may have three independent tanks, each containing 400Ð15 000 L (approximately 100Ð4000 gal) of oil, depending on their rating. However, most circuit breaker tanks contain less than 4500 L (approximately 1200 gal) of oil. Substations may have 10Ð20 or more oil circuit breakers.

Substation pumping facilities and cable terminations (potheads) that maintain oil pressure in pipe-type cable installations are another source of oil spills. Again, spills are caused by electrical failure, leaks, vandalism, sabotage, or accidents.

Depending on its length and rating, a pipe-type cable system may contain anywhere from 5000 L (approximately 1500 gal) up to 38 000 L (approximately 10 000 gal) or more of oil.

Mobile equipment
Although mobile equipment and emergency facilities may be used infrequently, consideration should be given to the quantity of oil contained and associated risk of oil spill. Mobile equipment may contain up to 30 000 L (approximately 7500 gal) of oil.

Oil-handling equipment
Oil filling of transformers, circuit breakers, cables, etc., occurs when the equipment is initially installed. In addition, periodic reprocessing or replacement of the oil may be necessary to ensure that proper insulation qualities are maintained. .

Oil pumps, temporary storage facilities, hoses, etc., are brought in to accomplish this task. Although oil

Oil storage tanks
Some consideration should be given to the presence of bulk oil storage tanks (either above ground or below ground) in substations as these oil tanks could be responsible for an oil spill of signiÞcant magnitude.

Also, the resulting applicability of the 40CFR, Part 112 rules for those storage tanks could require increased secondary oil containment for the entire substation facility. The user may want to reconsider storage of bulk oil at substation sites.

Other sources
Station service, voltage, and current transformers, as well as smaller voltage regulators, oil circuit reclosers, capacitor banks, and other pieces of electrical equipment typically found in substations, contain small amounts of insulating oil, usually less than the 2500 L (660 gal) minimum for a single container. Only under most unusual circumstances could they be responsible for an oil spill of the magnitude described in 40CFR.

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