Inspection & Preventive maintenance of breakers

1. Inspection & Preventive maintenanceof breakers

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

3. 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

4. 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

5. 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

6. 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

7. 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)

8. 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

9. 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

10. 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

11. 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