In this system of earthing, the neutral point is earthed through a single phase voltage transformer. The system thus acts as an insulated neutral system. Avery high reactance earthing is provided due to the voltage transformer.
The connection diagram is shown in the Fig.1.
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| Fig. 1 |
The voltage transformer shown in the above figure measures the voltage so that earth fault on the system is indicated. The travelling waves passing through the machine winding are reflected through voltage transformer. A surge divertor is used between neutral and earth to avoid the rise of voltage.
The voltage transformer is used normally in generator circuits which are directly connected to step up transformers. The generator circuits are physically isolated from the main distribution system. The electrostatic capacity of the circuit is negligible as the interconnecting cables between the generator and transformer windings are normally short. The risk of overvoltage conditions arising due to arcing ground is eliminated.
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