Network protector

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Electric Utilities use Network Protectors in a specialized version of their Electricity distribution systems called secondary networks. The function of the Network Protector is to automatically connect and disconnect its associated network transformer from the secondary network.

Typically the network protector is set to close when the voltage difference and phase angle are such that the transformer will supply power to the secondary grid. Conversely the network protector is set to open when the voltage difference and phasing angle is such that the secondary grid would backfeed through the transformer and supply power to the primary circuit. They are applied on both Spot Networks and Grid Networks.

Typically, Network Protectors are contained inside a submersible enclosure which is bolted to the throat of the network transformer and placed in underground vaults. IEEE standard C57.12.44 covers network protectors.