Recent Entries

  • Thermal equivalent short-circuit current (Ith)

      For a proper rating of power conductors and equipment the thermal effects of short-circuit currents  have to be considered. In the majority of cases in  practice the three phase short-circuit currents  have the highest magnitudes and produce the most pronounced the...
  • Zero-sequence ground current sensing

      Zero-sequence ground current sensing has been used for sensitive ground current protection for decades, but questions still are raised by installers and specifiers.  Strictly speaking, any method of ground current sensing involves detecting zero-sequence currents. For solidly grounde...
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  • Differential Protection for Power Transformers

      Current based differential protection has been applied in power systems since the end of the 19th century , and was one of the first protection systems ever used. Faults are detected by comparing the currents flowing into and out of the protected object as shown in Figure .   &nbs...
  • Concept of Grid

      Power Grid is a Network of power lines, transformers, and associated equipment employed in distributing electricity over a geographical area. In other words it can be defined as an interconnected network for delivering electricity from suppliers to consumers. It consists of generating stat...
  • Wind Turbine Generators

      To complete the entire process described above each Wind Turbine Generators will require a step up transformer to reach MV collection voltage. This transformer will either be located in the nacelle at the top of the wind turbine or on a pad at the base of the tower (varies by Wind Turbine ...
  • Broken conductor detection

      A typical unbalanced fault that can occur on the system is an open circuit fault. This fault can arise from a broken conductor, mal-operation of one of the switchgear poles, or blowing of a fuse.   Under / Over voltage protection (27/59)   Under-voltage conditions may occur o...
  • circuit breaker, Breaking capacity of Circuit Breaker

      The breaking capacity of a protection device must be at least equal to the maximum prospective shortcircuit current which may occur at the point at which this device is installed. Breaking capacity < ikmax the maximum prospective short-circuit current to be taken into account is: t...
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  • Power meters

      A power meter is a meter that can measure electrical parameters such as energy, power, voltage, current, power factor, and frequency. A power meter is generally an accurate (e.g. 0.5%) and precise (e.g. 32 samples per cycle) metering device tested to internationally recognized metering sta...
  • Problems caused by inrush:

      Power quality problems: unbalance harmonic   Other disturbances caused by inrush: 1. Incorrect operation and failures of electrical machines and relay systems, 2. Irregular voltage distribution along the transformer windings, 3. High amount of voltage drop at the power syst...
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  • Short-circuit currents

    Calculating the short-circuit current across the terminals of a synchronous  generator is very complicated because the internal impedance of the latter varies  according to time When the power gradually increases, the current reduces passing through three  characte...
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