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Inspection & Preventive maintenance of breakers . Why and what has to be maintained on breakers ?. Case Mechanism Arc chute Main contacts Control unit Connection systems Auxiliary Devices Communication system. Maintenance of case. Function of case :

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why and what has to be maintained on breakers
Why and what has to be maintained on breakers ?
  • Case
  • Mechanism
  • Arc chute
  • Main contacts
  • Control unit
  • Connection systems
  • Auxiliary Devices
  • Communication system
maintenance of case
Maintenance of case
  • Function of case :
    • isolate the main contacts and protect from arcing effects
    • support the mechanism, tripping device, auxiliary devices, terminals
    • Must withstand the stresses during short circuit
  • Damaged case is the consequence of :
    • shocks,
    • moisture,
    • high short circuit,
    • overheating ( loose connection)
  • Preventive maintenance includes :
    • visual inspection of dust, dirt, grease, moisture, cracks, soot,
    • cleaning, ( dust, dirt, soot,) with dry cloth, brush or vacuum cleaner
    • replacement in case of cracks
maintenance of the mechanism
Maintenance of the mechanism
  • Breaker mechanism
    • Spring energy on Masterpact
    • Tumbler on Compact NS
    • operate the contacts to establish and interrupt the circuit
  • Chassis mechanism
    • to rack in and out the breaker, test the breaker
  • Jammed mechanism is the consequence of :
    • dust :
    • shocks : bending of mechanical part
    • corrosive atmosphere : rust and corrosion of metallic part
    • No operation for a long time
  • Preventive maintenance includes :
    • dust removal : vacuum cleaner recommended
    • cleaning : dry cloth, brush, solvent prohibited
    • greasing : only Schneider recommended greases, in small quantity
    • operation of breaker / chassis : to give the spring charged energy and the mechanism their original characteristics
maintenance of the arc chute power breaker only
Maintenance of the arc chute (Power breaker only)
  • Function of arc chute :
    • splitters : extinguish the arc and absorb the energy under normal condition and electric fault
    • filter : blow the pressured gas out , cool down the gas
  • Arc chute deteriorates
    • under In : the insulation material of the arc chamber can perforate
    • under Icc : the metal part is vaporised
  • Arc chute in bad condition may result in a non interruption of the arc, decrease of the isolating function and ultimately destruction in case of high short circuit current.
  • Filters : avoid compound (made of dust + grease) covering the filter
  • Preventive maintenance includes :
    • periodic inspection after a fault : splitters should not present holes and be too thin, plastic part should not have holes ( decrease of insulation level)
    • replacement
    • cleaning of filter
maintenance of main contacts power breaker only
Maintenance of main contacts (Power breaker only)
  • Function of main contacts :
    • To make or break the circuit under normal ( In) or fault conditions (overload and Short-circuit )
  • Contacts get worn during each mechanical and electrical open / close operation and after short circuit ( maxi 2 cycles at Icu)
  • Worn contacts will result in :
    • over heating of the breaker ( increase of contact resistance)
    • decrease of life expectancy
  • Preventive maintenance includes :
    • periodic visual check, control of the mechanical contact wear indicator and electronic wear indicator on Micrologic P & H
    • measurement of individual pole resistance
    • replacement
maintenance of electronic control unit
Maintenance of electronic control unit
  • Function of control unit :
    • permanently analyse the phase current compare it to the protection set and in case of fault trips the breaker
  • Control unit is sensitive to :
    • environment : ambient temperature, humidity, corrosive atmosphere,
    • operating conditions : vibration, electro-magnetic field,
  • A malfunctioning of the trip unit will result in :
    • a non interruption of the fault current
    • damage of equipment and breaker
  • Preventive maintenance includes :
    • periodic push to trip test or trip test
    • control of the complete tripping channel
    • curve adjustment
    • saving of log event, settings ( Micrologic P & H)
maintenance of thermal magnetic trip unit
Maintenance of thermal-magnetic trip unit
  • Function of thermal-magnetic trip unit :
    • Connected permanently in series with the phase currents
    • based on the bending of a bimetal for overload and the movement of a magnet in a strong magnetic field
  • Thermal -magnetic trip unit is sensitive to :
    • ambient temperature, corrosive atmosphere
  • A malfunctioning of the trip unit will result in :
    • a non interruption of the fault current
    • damage of equipment and breaker
  • Preventive maintenance includes :
    • primary injection test to trip the breaker
maintenance of connection systems
Maintenance of connection systems
  • Function of connection systems :
    • Link together various types of devices by mean of electrical distribution systems (bus bars, cables, auxiliary wires, ).
  • Bad connection ( too tight or too loose) will result in :
    • Thermal effect leading to destruction of devices
    • short circuit or fire
  • Preventive maintenance includes :
    • For fixed connectors : No need of control if done with Schneider recommendation . otherwise : check temperature rise, if loose, dismantle and tighten with new screws, bolts & washers
    • For sliding connectors : (mainly chassis)
      • periodic cleaning and greasing with Schneider recommended grease
      • if corrosive atmosphere ( SO2 / H2S) : clean with special solution ( Thiourée) and re grease
    • Wires : check tightening and the insulation material
maintenance of auxiliary devices
Maintenance of auxiliary devices
  • Function of auxiliary devices :
    • Shunt trip release, under voltage release, OF contacts, SD/SDE alarm contacts , electrical motor MCH
  • Malfunctioning of the auxiliary device will result in a wrong operation of the breaker
  • the consequences can be :
    • no safety operation ( emergency)
    • wrong operation in the circuit
  • Preventive maintenance includes :
    • functional test of auxiliary device at nominal voltage
    • replacement
maintenance of communication systems
Maintenance of communication systems
  • Function of communication systems :
    • allow the dialogue with control unit ( read, write)
    • allow the remote control of breaker ( open close)
  • Bad communication will result in :
    • loss of information (status, monitoring, maintenance, production)
    • loss of control of breaker
  • Preventive maintenance includes :
    • testing of reading network parameters
    • testing of reading setting and changing setting
    • testing of remote control