To fully document the primary substations you need to include system earthing.
The objects that represents the system earthings are for example Neutral point, Earthing transformer, Neutral point resistor, Bus bar, neutral point, Circuit breaker, Disconnector, Other disconnecting devices and Earthing switch for the neutral point net.
The objects that are placed in the neutral point is suppose to be connected in the same way as the other objects in primary substations.
1.Neutral point resistor
2.Neutral point reactor
3.Bus bar neutral point
4.Neutral point
5.Earthing switch
6.Earthing
7.Earthing
8.Earhting switch
9.Earhting switch
The neutral point is connected to the downside winding or to a Earthing transformer.
The neutral point is then connected with help from a neutral point switch (see above) towards a neutral point bus bar.
You can then place earthing, neutral point resistor and neutral point reactor and connect them to the bus bar or more earthings. (see above)
Attribute data that can be of importance for network calculations is:
Neutral point: |
Other capacitive current, to document that there are other capacitive generation in the network except for the one obtained from the lines involved in the calculation. |
Neutral point reactor: |
The value for Set current is used in the network calculations to compensate for the capacitive current from the line network. |
Neutral point resistor: |
The value for Set current is used in the network calculations to set the resistive current that will occur during a high voltage fault from the current substation. |
The sum of the above specified currents together with the capacitive generation in the line network will represent the fault current that the network calculations will calculate and present as the electrification in the hidden objects.
If the primary substation contains several transformers a mutual system earthing can be handled by connecting the objects between the neutral points. The calculation program will then consider both opened and closed switches in the neutral point network so that the right values on Set current are summed.