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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.
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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.
The minimum fault current = 758 A as expected
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The next step is to define the protection relay.
Right click below the transformer and select New Devices -----> Relay Model
At Relay Type click Select Global Type
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.
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Now we need to display the rely using colour.
Click on colour map as shown below.
Then from drop down menu select
Relays, Current and Voltage Transformers as shown
When you click OK, the SLD shows now the line in Red where relay is connected.
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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.
The log graph appears as another sheet as shown below.
We can also click right on the graph and add the Transformer Damage Curve as shown.
Colour of Transformer Damage Curve can be chosen as shown below.
We can also select the voltage base for displaying the graphs, as shown below.
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.
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Re: Example of Over Current Protection Setting using DIgSILENT PowerFactory
Thank you for this topicComment
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