PROTECTING POWER TRANSFORMERS FROM COMMON ADVERSE CONDITIONS PDF

PROTECTING POWER TRANSFORMERS FROM COMMON ADVERSE CONDITIONS PDF
Power transformers play a significant role in power system delivery. Proper application of relay elements that monitor a transformer’s thermal state and through-faults can provide both short and long term benefits. These benefits include:

• Transformer overload protection, including cyclic
overloads
• Continuous transformer thermal status indication that
allows the system operator to make transformer loading decisions based on transformer thermal state
• Cooling system efficiency indication
• Records of cumulative per phase I2t values as seen by the transformer
• Settable I2t alarm thresholds that can notify the system operator of excessive through-fault current seen
by the transformer
• Cumulative I2tvalues as a measure to prioritize transformer maintenance

Overexcitation is a system condition and is not limited to generating stations. Proper application of Volts/Hz elements can prevent damage to transformers resulting from system overvoltage or underfrequency conditions.

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PARTS OF A POWER TRANSFORMER

What are the name of the basic parts of a Power Transformer? We can not deny the fact that only a handful of electrical engineering students are presently familiar with power transformers especially on what it looks like. Unlike a transformer we found in our homes, a power transformer’s appearance and construction is somewhat more complicated. It is not just a simple winding with a primary and secondary terminal although basically any transformer has one. The function that a power transformer plays in an electrical system is very important that an electric utility can not afford to loss it during its operation. Our discussion here will focus more on the basic parts and functions of a power transformer that are usually tangible whenever you go to a substation . Although not all power transformers are identical, nonetheless they all have the following listed parts in which the way of construction may differ.

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ELECTRIC MOTOR FRAME SIZE STANDARD SPECIFICATIONS

ELECTRIC MOTOR FRAME SIZE STANDARD SPECIFICATIONS How is electric motor frame size being specified? Motor frame dimensions have been standardized with a uniform frame size numbering system. This system was developed by NEMA and specific frame sizes have been assigned to standard motor ratings based on enclosure, horsepower and speed. The current standardized frames for integral horsepower induction motors ranges from 143T to 445T. These standards cover most motors in the range of one through two hundred horsepower. Typical example of where you can locate the frame is shown in Fig 1.2.D – Frame No. The numbers used to designate frame sizes have specific meanings based on the physical size of the motor. Some digits are related to the motor shaft height and the remaining digit or digits relate to the length of the motor. The rerate, or frame size reduction programs were brought about by advancements in motor technology relating mainly to higher temperature ratings of insulating mate

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ELECTRIC MOTOR NAMEPLATE SPECIFICATIONS

How do we interpret an electric motor nameplate? Motor standards are established on a country by country basis.Fortunately though, the standards can be grouped into two major categories: NEMA and IEC (and its derivatives). In North America, the National Electric Manufacturers Association (NEMA) sets motor standards, including what should go on the nameplate (NEMA Standard MG 1-10.40 "Nameplate Marking for Medium Single-Phase and Polyphase Induction Motors").

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