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Example of Over Current Protection Setting using DIgSILENT PowerFactory

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  • Example of Over Current Protection Setting using DIgSILENT PowerFactory

    This exercise shows how the PF can be used to calculate fault currents and set an overcurrent relay. The coordination graphs will be shown and tripping calculations will be displayed.

    Click image for larger version

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    Last edited by ; 09-04-2010, 08:34 PM.

  • #2
    Modelling of the network using PowerFactory

    The first setp is to model the network. This is done by creating a new project.

    Click image for larger version

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    Last edited by ; 09-04-2010, 08:36 PM.

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    • #3
      Calculation of Maximum and Minimum Fault Currents

      As known from basic power system theory that the maximum fault current occurs at network when we have three phase fault.
      The figure below shows the result when parameters are defined in the PwerFactory model.

      The maximum fault current = 875 A as expected.

      Click image for larger version

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      The minimum fault current = 758 A as expected

      Click image for larger version

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      Last edited by ; 09-04-2010, 08:37 PM.

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      • #4
        The next step is to define the protection relay.

        Right click below the transformer and select New Devices -----> Relay Model

        Click image for larger version

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        At Relay Type click Select Global Type

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        This will take you to library as shown in figure below.
        Choose the following relay as an example in this exercise.
        Other relays can be used if desirable.

        Library ----> Relays ----> Relays ---->
        select then Overcurrent Relays ----> GE Alstom ----> MCGG Series ----> MCGG-22.

        Click image for larger version

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        Last edited by ; 09-04-2010, 08:40 PM.

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        • #5
          Now it is time to define the CT for this relay
          Click on Create CT as shown below

          Click image for larger version

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          Then choose currnet ratio ----> write 800 A in primary. Click OK

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          Last edited by ; 09-04-2010, 08:31 PM.

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          • #6
            Now we need to display the rely using colour.
            Click on colour map as shown below.

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            Then from drop down menu select
            Relays, Current and Voltage Transformers as shown

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            When you click OK, the SLD shows now the line in Red where relay is connected.

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            • #7
              We need now to create the graph for the protection devices.

              Right click on the SLD where the relay is connected as sown below.
              Then select Create Time-Overcurrent Plot.

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              The log graph appears as another sheet as shown below.

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              We can also click right on the graph and add the Transformer Damage Curve as shown.

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              Colour of Transformer Damage Curve can be chosen as shown below.

              Click image for larger version

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              We can also select the voltage base for displaying the graphs, as shown below.

              Click image for larger version

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              There is also of course option to display the fault current (875 A) in different colour (blue)
              and also the tripping time of relay (1.357 s) for that fault current.

              Click image for larger version

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              • #8
                Re: Example of Over Current Protection Setting using DIgSILENT PowerFactory

                Thank you for this topic

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