Oil filled transformers

Transformers filled with combustible oils pose a fire hazard. Transformers should be adequately spaced from other critical or manned facilities per the requirements of NFPA 70 and IEEE. Adequate containment and removal of spillages should be provided. Spillage immediately at a transformer should drain into a gravel covered basin which prevents spillage from being exposed but allows drainage to be collected. 

Depending on the criticality and value additional fire suppression systems are provided for protection. NFPA 850 section 5-8.6 recommends that oil-filled station and start-up transformers at power generation plants be protected with a water or foamwater spray system. The most common installation is a fixed water spray. Where several transformers are provided, a firewall is commonly used to separate and protect one unit from another. 

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Oil filled transformer failed resulting in a fire which spread into the process plant. 14,700,000 loss. 

Oil Filled Transformer Liquid Spill NFPA 850 NFPA 70 1. Hydrants 2. Deluge Waterspray 1. NFPA 24 2. NFPA 15... 

Oil filled transformers with a relatively low concentration of PCBs. 

Environmental releases of PCBs often accompany releases of carriers from utility equipment. An example would be mineral oil released from oil filled transformers. When PCBs are present in a mineral oil-PCB mixture the aqueous solubility of the PCBs is reduced significantly. Two factors play a role in this reduction partitioning of the lipophilic (oil-loving) PCBs into the oil phase, and the reduced interaction of the PCBs with precipitation or groundwater caused by the hydrophobic nature of the oil matrix. Interpretation of aqueous PCB concentrations in the field must consider the presence of dissolved organic carbon (DOC) [382,386,397,403]. 

Oil-filled transformers shall not be used underground unless they are located in a fire-resistant enclosure suitably vented to the outside and surrounded by a dike to retain the contents of the transformers in the event of rupture. 

Dry-chemical extinguishing systems are used to protect flammable-liquid storage rooms, dip tanks, kitchen range hoods, deep-fat fryers, and similar hazardous areas and appliances. Because dry chemical is nonconductive, these systems are useful in the protection of oil-filled transformers and circuit breakers. Dry-chemical systems are not recommended for tele-phone-switchboard or computer protection. Dry chemicals are also widely used in portable fire extinguishers. 

These deteetors can also be used on sensitive equipment known for their frequeney of serious ineidents. Ion implanters have had electrical problems with their power supplies overheating, causing a fire. This is eritieal with the new ion implanters which have oil filled transformers. The fire will attack plastic lines used to supply the doping gas to the reactor chamber. This type of detector is sensitive enough to detect the overfieating and prevent the ignition and release materials that would seriously contaminate the eleanroom. 

Sharbaugh, A. H. and Walker, G. W., The design and evaluation of an ion-drag dielectric pump to enhance cooling in a small oil-filled transformer, IEEE Trans. Ind. AppL, 21, 950, 1985. 

This topic has proven to be of great interest in particular for the applications of paper as insulation systems in power transformers. Most of the literature concerning this subject was published by Emsley and co-workers [3,15-26]. In particular, Emsley [3] carried out numerous studies for better understanding the thermal degradation of papers for power transformers. In nearly all industrial oil-filled transformers, Kraft paper tapes... 

Figure 15.9 A typical outdoor type oil-filled 11 kV control transformer...

ASTM standard method D2283-86 defines the Askarel mixtures used by the utility industry (Table 5). The result of retrofilling older Askarel transformers is the presence of trace PCBs in refurbished oil filled equipment. McGraw [369]... 

Then we decided to try using the DC of the Microwave Transformer set. We wired in the bank of diodes that had been used with the microwave transformer and its capacitor (a 10.000 volt oil filled) before our bank of diodes. We put in a current-limiting resistor between our bank of diodes and the microwave s bank after the capacitor. We started with 1000 ohms here and gradually reduced it down to about 40 ohms (we where afraid to go lower for fear of blowing our diode bank). Each time we reduced it and tested it we got a louder bang when the spark occurred. At one point we had two 500 ohm resistors in parallel and one opened up. This was the loudest bang of... 

Converter-transformers are available either as wet transformers or as dry transformers. Dry transformers are air cooled. Wet or oil transformers are mounted in an oil-filled casing. The oil provides higher heat capacity and better heat removal. Thus an oil transformer can be more heavily loaded. 

Technical oils find uses in different industries but in particular the electrical industry, where there is frequent use of transformer oil. Transformer oil can be divided into two main groups (a) oils for transformers and switch gear and (b) oils for power cables this latter group can be further subdivided into thin oils, for use in oil-filled hollow core) cables, and more viscous oils, sometimes used as such in cable insulation but more commonly as components of cable impregnation compounds. 

The overall construction of oil and liquid filled transformers would be IP55 as defined... 

The same applies to the supply transformers, i.e. the converter and auxiliary transformers. However, transformers that are more than fifteen years old will most likely be of the oil-filled type and on some modern sites, the requirement is for transformers of the dry type. These would, of necessity, have to be imported from Europe or the far east and their delivery could have a negative effect on the availability of the winder being upgraded or refurbished and would also add quite considerably to the bottom-line cost of the upgrade or refurbishment. 

IEEE Std 62-1995, IEEE Guide for Diagnostic Field Testing of Electric Power Apparatus—Part 1 Oil Filled Power Transformers, Regulators, and Reactors. 

PCB contaminated Any electric equipment that contains more than 50, but less than 500 ppm of PCBs. (Oil-filled electrical equipment other than circuit breakers, reclosers, and cable whose PCB concentration is unknown must be assumed to be PCB-contaminated equipment.) Transformers, capacitors, circuit breakers, reclosers, voltage regulators, switches, cable, electromagnets... 

The retrofill of a PCB filled transformer involves the replacement of the original PCB dielectric fluid with a substitute oil. The main advantage of retrofilling is that an owner s liability is minimized at minimum cost. In addition, record keeping and reporting requirements are reduced or eliminated and servicing is allowed. 

The retrofill operation, as it is conventionally practiced today consists of multiple stages, each of which involves draining, flushing and filling. The process can apply to two different situations, viz. (1) contaminated mineral oil transformers with >500 ppm PCB and (2) asharel filled transformers in which the coils are impregnated with PCB. 

Many transformers are oil filled and this is a special hazard. It is preferred that utility transformers utilize less hazardous fluids for cooling. Semiconductor facilities should avoid building near or utilizing a substation with transformers using PCB s. While you can no longer buy this type of transformer, there are still some in operation. 

NFPA 850, Par 7.8.6 recommends that oil-filled main, station service, and startup transformers at power generation plants not meeting the separation or fire barrier recommendations should be protected with automatic water spray or foam-water spray systems. Additionally, it recommends that substations and switchyards located at the generating facility and utilizing combustible oil-filled equipment should be protected by fire hydrants where practical and consideration should be given to water spray protection of transformers critical to the transmission of the generated power. 

Industrial applications of SPS take advantage of the heat, dimensional stability, and chemical resistance of SPS. For example, liquid-filled transformer components require long-term exposure to the mineral oils used for coolants as well as heat resistance to handle the elevated temperatures that occur during peak demand periods. 

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