Inspection & Preventive maintenance of breakers 1

Why and what has to be maintained on breakers ? Case Mechanism Arc chute Main contacts Control unit Connection systems Auxiliary Devices Communication system 2

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 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) 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) 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 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 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 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 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 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