IEEE C37.108-2002 pdf download IEEE Guide for the Protection of Network Transformers
3. Definitions
The following definitions are found in The Authoritative Dictionary of lEEE Standards Terms, SeventhEdition (B9] and may aid in the understanding of this guide.
3.1 network feeder: A feeder that supplies energy to a network.
3.2 network limiter: An enclosed fuse for disconnecting a faulted cable from a low-oltage network distri-bution system and for protecting the unfaulted portions of that cable against serious thermal damage.
3.3 network master relay: A relay that functions as a protective relay by opening a network protector whenpower is backfed into the supply system and as a programming relay by closing the protector in conjunctionwith the network phasing relay when polyphase voltage phasors are within prescribed limits.
3.4 network phase relay: A monitoring relay that has as its function to limit the operation of a network mas-ter relay so the network protector may close only when the voltages on the two sides of the protector are in apredetermined phasor relationship.
3.5 network protector (power and distribution transformers): An assembly comprising a circuit breakerand its complete control equipment for automatically disconnecting a transformer from a secondary networin response to predetermined electrical conditions on the primary feeder or transformer, and for connecting atransformer to a secondary network either through manual control or automatic control responsive to prede-termined electrical conditions on the feeder and the secondary network.
3.6 network protector fuse: A backup device for the network protector.
3.7 network secondary distribution system: A system of alternating current distribution in which the secondaries of the distribution transformers are connected to a common network for supplying light and powetdirectly to consumers’ services.
3.8 network transformer (power and distribution transformers): A transformer designed for use in avault to feed a variable capacity system of interconnected secondaries.
3.9 network tripping and reclosing equipment: A piece of equipment that automatically connects its associated power transformer to an ac network when conditions are such that the transformer, when connected will supply power to the network and automatically disconnects the transformer from the network whenpower flows from the network to the transformer.
3.10 spot network: A small network, usually at one location, consisting of two or more primary feeders,with network units and one or more load service connections.
3.11 spot-network type: A unit substation, which has two step-down transformers, each connected to anincoming high-voltage circuit. The outgoing side of each transformer is connected to a common bus throughcircuit breakers equipped with relays that are arranged to trip the circuit breaker on reverse power flow to thetransformer and to reclose the circuit breaker upon the restoration of the correct voltage, phase angle, andphase sequence at the transformer secondary.
3.12 vault: A structurally solid enclosure above or below ground with access limited to personnel qualifiedto install, maintain, operate, or inspect the equipment or cable enclosed.
3.13 vault-type transformer (power and distribution transformers): A transformer that is constructed soas to be suitable for occasional submerged operation in water under specified conditions of time and externapressure.
4. General background
The physical and electrical characteristics of network transformer vaults have evolved over time, as have thecharacteristics of the load that they serve. This clause gives a brief description of this evolution. Theapplication considerations of grid versus spot-network vaults and of 208Y/120 V versus 480Y/277 Vsecondaries are also discussed.
IEEE C37.108-2002 pdf download
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