Recent Entries

  • Arc fault circuit interrupter

    Arc fault circuit interrupter technology was originally developed to protect areas near downed utility lines. As circuit boards were miniaturized, arc fault protection was applied to residential circuits. AFCIs are now commonly designed to protect 15- and 20-amp circuits in single and multi-family...
  • Time-based discrimination

      Protection functions form a consistent system depending on the overall structure of the power distribution system and the neutral earthing arrangement. They should therefore be viewed as a system based on the principle of discrimination, which consists of isolating the faulty part of the p...
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  • Generator Relay Data

      A good starting point is to compile the data needed for setting the various generator protective functions.  Figures provide examples of organizing and massaging or converting the information to a more useful form for generators, step-up transformers, and their associated elec...
  • Performance Evaluation for Ground Relays

     Performance Evaluation for Ground Relays When ground relays are connected in the neutral-to-ground circuits of the power system (3I0), or if I0 is obtained from a transformer delta tertiary,  is not applicable because the positive sequence load current is not involved. If power...
  • Requirements for Switchroom/Substation

      (1)  Facilities for locking Every switchroom  or  substation  should  have  suitable  means  of entrance/exit, which should be so arranged as to prevent unauthorised  entry but give authorised persons ready access at all times. For the purpose ...
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  • Design and type of transformer

    The purpose of transformers is to transfer electrical energy from systems of one voltage U1 to systems of another voltage U2. Transformers can be differentiated according to their manner of operation (Fig): Power transformers, the windings of which are in parallel with the associated systems...
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  • Protection and coordination of transformer

    Generally speaking, it is possible to obtain better transformer protection and better coordination with other protective devices by this means, because both the tripping current and tripping time for relays are much more accurate and consistent than the fuses. Therefore, when the primary breakers ...
  • Switchgear protection

      Switchgear protection has been around for as long as we have had switchgears. The idea of the protection is that when we have an overcurrent or overvoltage, a relay will notice it and react. The relay opens the breaker to avoid damage to the equipment. If the breaker is unable to break the...
  • The DC machine has three main

      Field or excitation system, represented  Armature, represented Commutator, represented   The field system is stationary in DC machines and the field winding is wound on salient poles. The field system produces the magnetization required for the machine and is called as the ...
  • Demands 12/24 kV medium voltage room

    The room where the switchgear will be setup should comply with building standard demands made on electrical rooms as soon as the installation is start. Due to the switchgear’s unique characteristics the room does not need to be equipped with special devices for pressure relief or for the eva...