If you need to place a current transformer in the neutral of a transformer, you should first distribute the neutral of the transformer. This is achieved by going to the Grounding/Neutral Conductor tab of the basic data page of the transformer element dialogue. Either the option "At terminals (ABC-N)" or "Separate on...." should be selected for the N-Connection setting.

The first option distributes the neutral to the connected busbar. In order to accept the transformer's neutral connection, the connected busbar should be configured with a phase technology parameter value including a neutral. e.g. ABC-N.

The second option distributes the neutral to a busbar other than the one to which the transformer's phase connections are terminated. Usually, this will be a dedicated busbar with the phase technology parameter value set to N. When selecting this option it is usually easier to leave the cubicle selection empty to start with. First place your dedicated neutral busbar then right-click on the transformer and choose the option "connect element". If you now connect the transformer to the new busbar you will find that the cubicle selection in the transformer is now populated with the correct cubicle.

Irrespective of the option selected, once the neutral has been distributed to an appropriate busbar, the neutral of the busbar should then be explicitly connected to earth using additional network elements which represent the solid, reactance or resistance earthing as required. Take care to ensure that that the connected elements are configured as single phase elements. You may also find it helpful to press the "Figure" button on the right side of branch element dialogues.

The current transformer can now be placed in the network model in exactly the same way as any other CT. Right-click in the region of an appropriate cubicle in the newly created neutral circuit, choose the optioned New Devices>>>Current Transformer. The CT should be configured as single phase device with the phase set to N.

Two projects are attached illustrating typical configurations.

In example 1, a neutral CT has been placed in the neutral of the autotransformer T3. The first option for distributing the transformer neutral has been selected. The autotransformer is earthed via a series reactor. The series reactor has been selected as a single phase element and has been connected to the neutral bar of busbar St_6. The neutral connection was selected in the cubicle Cub_8 of busbar St_6. The CT was placed in the same cubicle.

In example 2, a neutral CT has been placed in the 20kV neutral of the two winding transformer T3. The second option for distributing the transformer neutral has been selected. The transformer is again earthed via a series reactor. The series reactor has been selected as a single phase element and has been connected to the dedicated neutral busbar 'Neutral Busbar'. The CT was placed in Cub_2 of the busbar Neutral Busbar.

The diagram layout tool was used to add the relaying elements to the single line diagram.