IEEE C37.74-2003 pdf download IEEE Standard Requirements for Subsurface, Vault, and Pad-Mounted Load-Interrupter Switchgear and Fused Load-Interrupter Switchgear for Alternating Current Systems Up to 38 kV
3. Definitions
The definitions of terms contained in this standard. or in other standards referenced in this document, are notintended to embrace all the legitimate meanings of the terms. They are applicable only to the subject treatedin this standard. For additional definitions. see IEEE Std C37.100-1992.
A dagger (f) following a definition indicates that while the term is defined in IEEE Std C37.100-1992, thetwo definitions are not identical.
An asterisk (*) indicates that at the time this standard was approved, there were no corresponding definitionsin IEEE Std C37.100-1992
3.1 fused-loadbreak way*: A fused way incorporating an integral switching device operated by openingand closing a fuse assembly.
3.2 fused-switch way*: A way connected to the bus through a three-phase group-operated switch or singlephase switch in series with high-voltage fuses.
33 pad-mounted switchgear, subsurface switchgear, vault-fused switchgear, vault switchgear*: Refeito IEEE Std C37.100-1992. In EEE Std C37.74-2003, pad-mounted switchgear, subsurface switchgear.vault switchgear, with or without protective devices, shall be designated simply as distribution switchgear(DSG).
3.4 protected way*: A way connected to the bus through a protective device.
3.5 subsurface switchgear: A submersible switching assembly suitable for application in a below-gradeenclosure normally surface operable.
3.6 surface operable: A term indicating that the switch and its accessories are operable from above grade
3.7 switched wayt: A way connected to the bus through a three-phase group-operated switch or singlephase switch.
3.8 tapped way: A way solidly connected to the bus.
3.9 vault switchgear: A term indicating that the switch and its accessories are operable from inside a vault
3.10 wayt: A three-phase or single-phase circuit connection to the bus, which may contain combinations ofswitches and protective devices or may be a solid bus.
NOTE-See Figure l for an illustration of the definitions in Clause 3.
4. Service conditions
4.1 Usual service conditions
Apparatus conforming to this standard shall be suitable for operation at nameplate rating provided that
a) The ambient air temperature is not above 40 °C or below –30 °C.
b) The altitude does not exceed 1000 m.
c) The subsurface or vault switchgear that is installed in a below-grade enclosure is subject to occasional flooding to a depth not exceeding 3 m above the top of the switchgear.
NOTE—Fuse time-current characteristics and continuous current ratings are affected by temperature; see IEEE Std C37.48-1997.
4.2 Unusual service conditions
Unusual service conditions shall include, but are not limited to, service conditions that exceed the conditions defined in 4.1 or extremes in
a) Duty cycle or unusual frequency of operation
b) System conditions including high harmonic content currents and voltages
c) Site conditions
d) Shock, vibration, or tilting
e) Damaging fumes, vapors, or corrosive liquids
f) Excessive or abrasive dust
g) Explosive mixtures of dust or gases
IEEE C37.74-2003 pdf download
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