Eaton VacClad-W Instruction Booklet

Also see for VacClad-W: Instructions for installation, operation, maintenance

15Instruction Booklet IB32267ARCEffective December 2010VacClad-W 38 kV arc-resistantswitchgear indoor housingseaton Corporation www.eaton.comSection 8: a further description ofarc-resistant VacClad-W switchgearFigure 16. Typical 38 kV Arc-Resistant Switchgear Assembly(Arc Skirts Not Shown)8.1 Arc-resistant switchgear general discussionArc-resistant metal-clad switchgear is metal-clad switchgear testedfor resistance to the effects of arcing due to an internal faultThe occurrence of arcing inside switchgear produces a variety ofphysical phenomena For example, the arc energy resulting froman arc developed in air at atmospheric pressure will cause a suddenpressure increase inside the enclosure and localized overheatingThis results in both severe mechanical and thermal stresses onthe equipment Moreover, the materials involved in or exposed tothe arc may produce hot decomposition products, either gaseousor particulate, which may be discharged to the outside of theenclosure IEEE guide PC37 20 7, draft 15d, 200X, and EEMACstandard G14-1, 1987, provide procedure for testing the resistanceof metal-clad and metal-enclosed medium voltage switchgear underconditions of arcing due to an internal fault The arc-resistantswitchgear is classified by accessibility types in the twodocuments as follows:IEEE PC37 20 7, draft 15d, 200X—Guide for testing mediumvoltage metal-enclosed switchgear for internal arcing faultsAccessibility Type 1Switchgear with arc-resistant designs or features at the freelyaccessible front of the equipment onlyAccessibility Type 2Switchgear with arc-resistant designs or features at the freelyaccessible exterior (front, back, and sides) of the equipment onlyAccessibility Type 1 or Type 2 with Suffix “C”The application of suffix “C” to Accessibility Type 1 orType 2 indicates that the equipment meets the additionalrequirements of the Annex given in the standard It doesnot imply that the equipment may be operated with doors,covers, or panels opened or removed and maintain its intendeddegree of protection This additional performance is intendedto reduce the collateral damage to adjacent compartmentsand equipment, and should not be interpreted to indicateany additional degree of protection for personnel Equipmentqualified to the conditions described is labeled as Type 1C orType 2C (as appropriate)Type 1C—Type 1 equipment subjected to additional testing andassessment to verify that the internal arcing does not causeholes in the freely accessible front of the enclosure or in thewalls separating the compartment in which the arc is initiated,and all adjacent compartmentsType 2C—Type 2 equipment subjected to additional testing andassessment to verify that the internal arcing does not causeholes in the freely accessible front, sides, and rear of theenclosure or in the walls separating the compartment in whichthe arc is initiated, and all adjacent compartments Exception:In metal-clad (C37 20 2) equipment, a fault in a main bus barcompartment of a vertical section is allowed to propagate intothe main bus bar compartment of the adjacent vertical sectionsif the main bus bars are in the same circuit, but not if the mainbus bars are in different circuits Connections from the main busbar to switchgear components are not considered to be part ofthe main bus and propagation of a fault along these connectionsinto the compartment containing the component is not allowedEEMAC G14-1, 1987—Procedure for testing the resistanceof metal-clad switchgear under conditions of arcing due toan internal faultAccessibility Type ASwitchgear with arc-resistant construction at the front onlyAccessibility Type BSwitchgear with arc-resistant construction at the front, backand sidesAccessibility Type CSwitchgear with arc resistant construction at the front, backand sides and between compartments within the same cell oradjacent cells The only exception is that a fault in a bus barcompartment of feeder cell is allowed to break into the bus barcompartment of an adjacent feeder cellThe IEEE standard defines Internal arcing short-circuit current as themaximum value of the rms symmetrical prospective current appliedto the equipment under conditions of an arcing fault for the arcingduration specified by the manufacturer The preferred value of theinternal arcing short-circuit current is the rated short-time current ofthe equipment The preferred arcing duration is indicated as 0 5 sec-onds at the rated power frequency of the equipment A single test isdone to verify resistance of switchgear against pressure as well asburn through The actual values (which may be higher or lower thanthe preferred values) of the internal short-circuit current and arcingduration are specified by the manufacturer on the equipmentratings nameplateIn EEMAC standard, internal arc short-circuit current is indicated asthe prospective short-circuit current applied during the calibrationprior to testing and may be equal to or lower than the rated short-time capability of the equipment This standard requires testing toprove resistance of switchgear against pressure (arcing duration10 cycles), and testing to prove the resistance of switchgear toburn through (arcing duration 1 second)There are also differences in the two standards in the way test-ing is conducted and assessed It is not possible to list differencesbetween the two standards in this instruction book Refer to thedrawings supplied for the equipment for internal arc short-circuitcurrent, duration, accessibility type, and standard to which theequipment is tested User should then refer to the applicablestandard for details of guidelines under which the equipmentis tested and qualifiedDoor HandleOpen PositionDoor ClosedOpen Position