Siemens 3AFS Series Instructions, Installation, Operation, Maintenance

Interrupter/Operator - Maintenance Page 24Hydraulic Shock AbsorberThe 3AFS mechanism is equipped with a hydraulic shockabsorber and a stop bar that functions when the breaker opens.See item 61.8 Figure 9. The shock absorber should require noadjustment. Flowever, at maintenance checks, the shockabsorber should be examined for evidence of leaking. If evi-dence of fluid leakage is found, the shock absorber must bereplaced to prevent damage to the vacuum interrupter bellows.Life = Interruptions x CurrentThey must also be replaced before 30,000 mechanical opera-tions or when the contacts have been erroded beyond allowedlimits. Vacuum tube replacement procedures are detailed in thefollowing maintenance instructions.As a guide to life expectancy the curves in Figure 18 are offered.Vacuum InterruptersLife Expectancy3AFS BreakerDesignationVolts kV 5- 5- 7- 15« 15- 15-Nom.mVA 250 350 500 500 750 1000Rated Max. Volts, kV 4.76 8.25 15.0The life expectancy of vacuum interrupters is a function of thenumber of interruptions and magnitude of current interrupted. Rated Short-CircuitCurrent, kA29 41 33 18 28 37Rated ContinuousCurrent, A1200 b fdca e20003000fb da c eb fc eApplicable Curve a Function of Breaker RatingContact ErosionVacuum interrupters should be checked periodically for con-tact shortening, which is normally associated with erosion of con-tact material during high fault current interruptions. Contactshortening or erosion is normally not expected to be significantuntil the number of operations indicated for contact life is ap-proached. When the number of operations reaches the indicatedcontact life or excessive contact shortening or erosion is in-dicated, the interrupter tubes should be replaced. Contact ero-sion or shortening normally is checked by the visibility of theerosion mark. Alternately it may be checked by measuring thecontact stroke.Contact erosion is checked on a closed breaker by visuallyobserving a white dot erosion mark (A) on the exposed movablecontact stem of the interrupter, see Figure 19.NOTEThe tripping springs are charged and the circuitbreaker could open unexpectedly.The mark (A) may be seen above the lower primary connec-tion, and just above the terminal clamp which fastens the flexi-ble connector (29.1) to the movable stem of the vacuum tube.The criteria of acceptance is that as long as the white erosionmark or any part of it can be seen with the breaker closed, con-tact wear is within permissible limits.Figure 18. Typical Primary Interrupter Contact Life Curves