IEEE C57.12.80-2002 pdf download

IEEE C57.12.80-2002 pdf download.IEEE Standard Terminology for Power and Distribution Transformers.
3.54 Class 220 insulation system: Materials or combinations of materials, which by experience or accepted tests, have been shown to give the required life at a continuous temperature of 220 °C.
3.55 Class over-220 insulation system: Materials or combinations of materials, which by experience or accepted tests, have been shown to give the required life at a continuous temperature at temperatures over 220 °C.
NOTE—The six class insulation system temperatures dened above are and have been, in most cases over a long period of time, benchmarks descriptive of the various classes of insulating materials, and various accepted test procedures have been or are being developed for use in their identication.
They should not be confused with the actual temperatures at which these same classes of insulating materials may be used in the various specic types of equipment, nor with the temperatures on which specied temperature rises in equipment standards are based.
n the previous denitions the words “accepted tests” are intended to refer to recognized test procedures established for the thermal evaluation of materials by themselves or in simple combinations. Experience or test data, used in classifying insulating materials, are distinct from the experience or test data derived for the use of materials in complete insulation systems. The thermal endurance of complete systems may be determined by test procedures specied by the responsible technical committees. A material that is classied as suitable for a given temperature may be found suitable for a different temperature, either higher or lower, by an insulation system test procedure. For example, it has been found that some materials suitable for operation at one temperature in air may be suitable for a higher temperature when used in a system operated in an inert gas atmosphere.
Likewise, some insulating materials when operated in dielectric liquids will have lower or higher thermal endurance than in air. It is important to recognize that other characteristics, in addition to thermal endurance, such as mechanical strength, moisture resistance, and partial discharge (corona) endurance, are required in varying degrees in different applications for the successful use of insulating materials.
3.56 Class A insulation:See:class 105 insulation system.
3.57 Class B insulation:See:class 130 insulation system.
3.58 Class F insulation:See:class 155 insulation system.
3.59 Class H insulation:See:class 180 insulation system.
3.60 Class >H insulation:See:class 220 insulation system.
3.61 coefcient of grounding: The ratio (E LG /E LL ) expressed as a percentage, of the highest root-mean- square line-to-ground power-frequency voltage (E LG ) on a sound phase, at a selected location, during a fault to earth affecting one or more phases to the line-to-line power-frequency voltage (E LL ) that would be obtained, at the selected location, with the fault removed.
NOTES: 1—Coefcients of grounding for three-phase systems are calculated from the phase-sequence impedance components as viewed from the selected location. For machines, use the subtransient reactance.
2—The coefcient of grounding is useful in the determination of a surge arrester rating for a selected location.
3—A value not exceeding 80 percent is obtained approximately when for all system conditions the ratio of zero- sequence reactance to positive-sequence reactance is positive and less than three, and the ratio of zero-sequence resistance to positive-sequence reactance is positive and less than one.
3.62 coil (of a transformer): The assemblage of windings that encircle a ferromagnetic core leg (limb) for the purpose of producing or linking magnetic ux. See also: winding of a transformer.
3.63 combustible material: Materials that are external to the apparatus and made of or surfaced with wood, compressed paper, plant ers, or other materials that will ignite and support ame.
3.64 common winding of an autotransformer: That part of the autotransformer winding that is common to both the primary and the secondary circuits.IEEE C57.12.80 pdf download.IEEE C57.12.80-2002 pdf download