Eaton 380 VCP-W 16 Instructions For Installation, Operation And Maintenance

Also see for 380 VCP-W 21: Instructions for installation, operation and maintenance

Contents

I.B. 3A74792H08 Page 23Effective 0 9 / 2 0 14CAUTIONTHE PLATE BOLTED TO THE REAR RECTANGULAROPENING ON ALL 2000 AMPERE AND ABOVECIRCUIT BREAKERS AND IDENTIFIED IN FIGURE 5-2MUST BE BOLTED IN POSITION BEFORE PLACING ACIRCUIT BREAKER IN SERVICE TO INSURE PROPEROPERATION WITHIN TEST PROVEN PARAMETERS.Vacuum interrupters are mounted vertically and supportedfrom the fixed stem which is clamped to the topconductor. The exclusive current transfer system consistsof a series of plated, high-conductivity copper leafconductors that are pressed on the movable interrupterstem.This design provides a multipoint contact resulting in lowelectrical and thermal resistance. Utilizing this non-slidingcurrent transfer system between the movable stem andthe circuit breaker main conductor eliminatesmaintenance of this joint.Direct acting insulated operating rods in conjunction withthe circuit breaker’s mechanism provide a fixed amountof interrupter movable stem motion. This motion isdirectly related to the interrupter’s “Wipe” and “Stroke,”each of which is discussed in detail later in this section.5-2.1 VACUUM INTERRUPTERVCP-W and VCP-WR 38kV Vacuum Circuit Breakersutilize vacuum interrupters for interruption and switchingfunctions. The vacuum interrupters use axial-magnetic,copper chrome contacts for superior dielectric strength,better performance characteristics, and lower chop cur-rent. 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 5-3). 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.Figure 5-3 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, togetherwith the fast condensation of metalvapor products, cause the vacuum to be quicklyrestored. Hence, the opened contacts withstand thetransient recovery voltage.5-2.2 CONTACT EROSION INDICATIONThe purpose of a contact erosion indicator is tomonitor the erosion of the vacuum interruptercontacts, which is very minimal over time with vacuuminterrupters utilizing copper-chrome contact material. Ifcontact erosion reaches 1/8 inch, the interrupter mustbe replaced.NOTICEEach phase of the circuit breaker is monitoredindependently.Contact erosion is monitored from the rear of thecircuit breaker. It provides a very accurate indication ofcontact erosion, and is the primary determinant ofcontact condition. A contact erosion indicator mark islocated on the insulated drive rod of each interrupter(Figure 6-2).