Two three phase transformers are said to be connected in parallel if their primary windings are connected to supply bus bars and secondary windings are connected to the load bus bars. While connecting two or more than two three phase transformers for parallel operation, it is essential that their terminals of similar polarities are joined to the same bus bars because the improper connections...
Sunday, June 30, 2013
Friday, June 28, 2013
Skin Effect in Transmission Lines
The phenomena arising due to unequal distribution of current over the entire cross section of the conductor being used for long distance power transmission is referred as the skin effect in transmission lines. Such a phenomena does not have much role to play in case of a very short line, but...
The Ferranti effect
In electrical engineering, the Ferranti effect is an increase in voltage occurring at the receiving end of a long transmission line,to the voltage at the sending end. This occurs when the line is energized but there is a very light load or the load is disconnected. The capacitive line charging current produces a voltage drop across the line inductance that is in-phase with the sending end...
String Effeciency and methods to improve String Effeciency
The ratio of voltage across the whole string to the product of number of discs and the voltage across the disc nearest to the conductor is known as string efficiency i.e., where n = number of discs in the string. String efficiency is an important consideration since it decides the...
Step & Touch potential
In electrical engineering, earth potential rise (EPR) also called ground potential rise (GPR) occurs when a large current flows to earth through an earth grid impedance. The potential relative to a distant point on the Earth is highest at the point where current enters the ground, and declines...
Low voltage systems
Requirements for Electrical Installations, more commonly known as the Wiring Regulations, nominal a.c. voltages are defined as follows: · Extra-low voltage: not exceeding 50 V a.c., whether between conductors or to earth. · Low voltage: exceeding extra-low voltage, but not exceeding...
New harmonized color code
Old color code New color code: ...
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