what_and_why_maintaining_breakers.ppt Inspection & �Preventive maintenance�of breakers

what_and_why_maintaining_breakers.ppt

1. Inspection &
Preventive maintenance
of breakers

2. DDI - Department - Name - Date 2
Developments - Industry
Why and what has to be maintained
on breakers ?
Case
Mechanism
Arc chute
Main contacts
Control unit
Connection systems
 Auxiliary Devices
Communication system

3. DDI - Department - Name - Date 3
Developments - Industry
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. DDI - Department - Name - Date 4
Developments - Industry
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. DDI - Department - Name - Date 5
Developments - Industry
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. DDI - Department - Name - Date 6
Developments - Industry
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. DDI - Department - Name - Date 7
Developments - Industry
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. DDI - Department - Name - Date 8
Developments - Industry
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. DDI - Department - Name - Date 9
Developments - Industry
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. DDI - Department - Name - Date 10
Developments - Industry
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. DDI - Department - Name - Date 11
Developments - Industry
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