Eaton 380 VCP-Wind Instructions For The Use, Operation And Maintenance

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I.B. 70A2580H02 Page 15Effective November 2012SECTION 5: DESCRIPTION AND OPERATION5-1 INTRODUCTIONThe Type VCP-Wind 38kV Vacuum Circuit Breaker is ahorizontal drawout roll on the floor design for use in newswitchgear, as well as for modernization and lifeextension of existing switchgear. The circuit breakersmeet or exceed all applicable IEEE Standards.Circuit breakers are operated by a motor chargedspring type stored energy mechanism, chargednormally by an electric motor or manually by a manualcharging tool. The primary disconnecting contacts areself-aligning, silver plated copper. VCP-Wind CircuitBreakers are of a modular type construction containinga front accessible mechanism with unobstructed accessto control components.The primary insulation used in the circuit breaker designis epoxy. Type SIS, AWG #14 control wire with cross-linked polyolefin insulation is used throughout thecontrol circuits with all terminals being of the screwtype. This section describes the overall operation of thecircuit breaker as well as the function and operation ofall major sub-assemblies and/or parts.5-2 VACUUM INTERRUPTERVCP-Wind 38kV Vacuum Circuit Breakers utilize vacuuminterrupters for interruption and switching functions. Thevacuum interrupters use axial-magnetic, copper chromecontacts for superior dielectric strength, betterperformance characteristics, and lower chop current.Vacuum interruption provides the advantages ofenclosed interrupters, reduced size and weight, shortinterrupting time, long life, reduced maintenance, andenvironmental compatibility.Arc interruption is simple and fast (Figure 5-1). In theclosed position, current flows through the interrupter.When the contacts are opened, the arc is drawn betweenthe contact surfaces. It is moved rapidly around theslotted contact surfaces by a self-induced magnetic forcewhich prevents gross contact erosion as well as theformation of hot spots on contact surfaces. The arc burnsin an ionized metal vapor which continually leaves thecontact area and condenses on the surrounding metalshield.5-2.1 INTERRUPTER ASSEMBLYThe VCP-Wind design utilizes three individuallymounted pole units. Each pole unit is encapsulatedin an epoxy support molding. (Figure 3-3). Thedisconnecting ends of the primary conductors utilizeround, floating type primary disconnecting fingerclusters for interfacing with the switchgear structuremounted primary conductors.Figure 5-1 Graphic Representation of Arc InterruptionAt current zero, the arc is extinguished and vaporproduction ceases. Very rapid dispersion, cooling,recombination, and deionization of the metal vaporplasma, together with the fast condensation of metalvapor products, cause the vacuum to be quicklyrestored. Hence, the opened contacts withstand thetransient recovery voltage.5-2.2 CONTACT EROSIONContact erosion for the vacuum interrupter isnegligible and no re-adjustment of the breaker isneeded after initial assembly and no additionalcontact wipe to compensate for contact erosionduring the entire life of the circuit breaker.