Eaton MVS Instructional Booklet

Contents

16Instructional Booklet IB02102006EEffective May 2011Type MVS (previously WLImetal-enclosed switchgear4.76 kV, 15.0 kV, 27.0 kV, and 38.0 kVeaton corporation www.eaton.comoperationMechanical safety interlocksThe MVS switch is equipped with switch interlocks and door inter-locks, as well as provisions for padlocking in either the “Open” or the“Closed” position WARNINGDEFEATING OR DISENGAGING SAFETy INTERLOCKS ON AN MVS SWITCHTHAT IS CONNECTED TO A POWER SOURCE MAy RESULT IN PROPERTyDAMAGE, BODILy INJURy, OR DEATH.DO NOT DEFEAT OR DISENGAGE ANy SAFETy INTERLOCKS.Switch interlockThe switch interlock prevents inadvertent closure of the switch if theenclosure door is open When the door is closed, the pointed latchlug welded to the inside of the door causes the safety latch to moveout of the blocking position (see Figure 21)Figure 21. Door/Switch Mechanism and Shaft InterlockLocationsDoor interlockThe door interlock prevents the door of the enclosure from beingopened when the switch is “Closed ” When the switch is “Closed,” acam welded to the operating shaft engages a bracket welded to theinside of the switch door, preventing the door from being opened(see Figure 21)Key interlockingKey interlocks are supplied when specified Certain MVS switchgearconfigurations require key interlocks and they are therefore includedStandard schemes are available for locking the switch in the “Open”or the “Closed” position, as well as locking the main door closedNumerous other schemes are available for special requirements thatcan coordinate with upstream or downstream devices supplied byEaton or other equipmentSwitch operationThe quick-make mechanism provides power to overcome blowoutforces that occur if the switch is “Closed” into a fault However, theseforces are not transmitted to the operating handle because it isnot rigidly connected to the blades Therefore, the switch can besafely closed under short-circuit conditions within its fault-close ratingMechanism CoverDoor/Switch Shaft InterlockDoor/Switch Mechanism InterlockLoad interruption is accomplished by a flicker blade and engagingcontact fingers located inside a DE-IONT arc chute On opening theswitch, the main blades open first and all current is shunted throughthe spring-loaded flicker blades Further travel of the main bladescauses the flicker blades to snap out of their contact fingers whereassociated arcing takes place within the arc chutes See Figure 22for the sequence of operationFigure 22. Main and Flicker Blade OperationFuse replacement WARNINGWHEN ACCESSING FUSES, FAILURE TO ENSURE THAT THE FUSES AREDE-ENERGIzED MAy RESULT IN EQUIPMENT DAMAGE, BODILy INJURy,OR DEATH.MAKE SURE THAT ALL POWER SOURCES ARE DE-ENERGIzED BEFOREATTEMPTING TO ACCESS THE FUSES.Step 1e: All upstream devices that could energize the fuse should beopened, padlocked, and tagged so that inadvertent closure cannotcreate a hazardStep 2e: The MVS switch should be in the “Open” position This isaccomplished by rotating the operating handle downwardStep 3e: Before opening the door, look through a viewing windowto visually verify that all blades are disengaged from their break jawsStep 4e: After opening the door, an appropriate medium voltagesensing device should be used to determine if voltage is presentStep 5e: If no voltage is present, a suitable grounding device shouldbe attached to the fuse terminals to discharge any static charge andensure that the fuse terminals remain at ground potentialStep 6e: The fuses are removed by loosening the plastic handknobs and removing the locking bars The fuses are then free to beremoved When the fuses are re-installed, the hand knobs should beretightened hand tightLeft Pole: Main Blade and Flicker Blade Colsed.Center Pole: Main Blade Open, Flicker Blade Closed.Right Pole: Main Blade and Flicker Blade Open.