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Copyright AIST Reprinted with Permission. Presented at the 2013 Iron and Steel Technology Conference and Exposition (AISTech 2013). In an industrial facility, nothing operates without a reliable flow of electricity. Therefore, it is critical to properly maintain the switchgear and switchboards that distribute electricity through the power system. Switchboards are more commonly used in commercial and light industrial Low Voltage applications, while switchgear is usually specified in heavy industrial Medium Voltage applications, where the demands on the equipment require more robust construction.
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Miklos J OroszSenior Staff Engineer
Schneider Electric
Extending the life of existing switchgear
In an industrial facility, nothing operates without a reliable flow of electricity
With increasing dependence on computers and automated processes, most modern facilities cannot afford downtime
Electrical Systems are Serious Business
Switchgear Reliability and Longevity
Requires two fundamental activities Preventive Maintenance Periodic Updating
Preventive Maintenance
Having a preventive maintenance program in place can, in many cases, double the life of existing switchgear.
According to IEEE, the rate of electrical component failures is three times higher in facilities that do not perform preventative maintenance on their electrical systems.
Contributing factors Mechanical failure (43%)
Loose connections, overheating, load changes/additions
Environmental conditions (17%) Humidity, dirt/dust or corrosive environments May impace the OEM’s recommended maintenance
schedule
Work improperly performed (17%) NFPA 70B 3.3.58 states that equipment maintenance
is to be performed by a qualified person
Inspection Cleaning and lubrication Adjustments Over-current protective device testing Insulation testing Charge/close/trip circuit testing Dielectric testing Time and speed testing
Fundamental Circuit Breaker Maintenance Activities
Circuit Breaker Technology Essentially four types of medium voltage
circuit breakers
Based on the arc quenching medium
Oil Air SF6 Gas Vacuum
Typically are draw-out type
Modernization
Retrofitting is a general term that is used to define any process which allows for modernization and life extension of electrical equipment
Maintaining the core switchgear structure, conduits, cabling and footprint are left intact, which saves time and money
Modern circuit breaker technology have a longer life-cycle helping extend overall switchgear life
Eight Reasons to ModernizeUpgrade Circuit Breaker
Improve ratings Environmental impact and hazards Performance and safety improvements Meet current ANSI Standards Improve reliability Reduce maintenance cost Reduce size and weight Unforeseen cost considerations
Eight Reasons to ModernizeUpgrade Circuit Breaker
1.Improve Ratings Switchgear frame or enclosure, and bussing, are usually higher
rated than the circuit breakers
Circuit breakers can be upgraded at least one class i.e. from 25kA short circuit interrupting capability to 40kA In many cases even higher up to 50kA
Modern vacuum circuit breakers are also faster, most of them have short circuit current interrupting rating of 3 cycles or less
Older circuit breakers have interrupting time of 5 or 8 cycles, or more
Eight Reasons to ModernizeUpgrade Circuit Breaker
2. Environmental impact and hazards Many old design air magnetic circuit breakers used
asbestos based arc chutes
The oil used in oil circuit breakers may contain hazardous chemicals
SF6 gas was recently declared a green house gas
New technology of vacuum interrupters can help resolve environmental concerns
Eight Reasons to ModernizeUpgrade Circuit Breaker
3. Performance and safety improvements Fault current interruption
New circuit breakers are available with higher ratings In most cases, the interruption capacity of the entire
switchgear can be increased with an engineering study and a circuit breaker upgrade or replacement
Arc flash limiting circuit breaker availability Trip unit accuracy and repeatability with new circuit
breakers Power metering, monitoring, and communication
Eight Reasons to ModernizeUpgrade Circuit Breaker
4. Meet current ANSI Standards Vacuum circuit breakers are operating with the
voltage factor K=1 Interrupting capability is not affected by the system voltage
Vacuum circuit breakers with an assigned short circuit current interrupting capability will function at any voltage level without reducing the assigned short circuit interrupting rating
More flexibility for interchangeability of the new circuit breakers
Eight Reasons to ModernizeUpgrade Circuit Breaker
5. Improve Reliability Electromechanical trip interrupting devices on existing
circuit breakers may have reliability issues: Many do not trip at all Those that trip are not repeatable and may be well
outside the time-current coordination parameters
Aging materials reduce equipment reliability due to: Dielectric breakdown of insulating components Degradation of aging mechanical parts
Eight Reasons to ModernizeUpgrade Circuit Breaker
6.Reduce Maintenance cost Older power circuit breakers require extensive periodic
maintenance and overhaul Expensive and time consuming Lengthens outages May require extensive outside support
Many components for existing and older circuit breakers are no longer available Quantity and quality of used or reconditioned parts is
decreasing and unreliable Prices of replacement parts are increasing
Eight Reasons to ModernizeUpgrade Circuit Breaker
7. Reduce size and weight 30% to 60% weight reduction can be achieved by
using new vacuum technology. Can improve maintenance access and transportability
Eight Reasons to ModernizeUpgrade Circuit Breaker
8. Unforeseen cost considerations Several factors influence the cost when considering upgrades
Cost of new equipment VS. retrofit/ upgraded equipment Plant maintenance cost analysis Additional space requirements Construction cost Installation cost Removal of existing equipment Disposal of existing equipment Labor cost of training maintenance personnel Downtime cost Cost of Production loss
Updated with New Technology
Original air magnetic circuit breaker with asbestos based arc chutes
Direct replacement modern vacuum circuit breaker
Thank You
Miklos J OroszSenior Staff Engineer
Schneider Electric