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  • Maintaining MV Switchgear Western Mining Electrical

    Association Tucson, AZ

    November 15, 2007

  • Maintenance of MV (Above 1000V and up to 38kV) Switchgear

    Keywords:SafetyDeenergize Lockout/TagoutMaintenance IntervalArc-flashGroundingInterlocksToolsBackfeed

  • Why Maintain Switchgear?

    Its a Hobby!!!!!!!Switchgear is new and doesnt need maintenance!!!Short-Circuit is unpredictable so why bother?

  • Why Maintain Switchgear? Getting Everyones Attention

    Every Electrical Conductor or Circuit is Considered Energized (Unsafe) Until Proven Otherwise (Innocent)

  • Why Maintain Switchgear?

    Reduce Hazards to Life and Property that can result from Failure or Malfunction of Poorly Maintained Electrical SystemsReduce the Outages and Down timeIncrease the efficiency of work force Significant Loss of Revenue until Service is RestoredWell Maintained Switchgear will last long time, More importantly, It is the safest thing to do

  • Factors affecting the Electrical Safety in Coal Mines

    Inadequate or Improper Training Failure to Deenergize, Lockout and TagoutFailure to ensure proper groundingFailure to recognize downstream devices (Possible back feed from downstream device) Defeating and/or Ignoring Mechanical and Electrical Safety InterlocksPoor Grounding

  • Factors affecting the Electrical Safety in Coal Mines

    Failure to Maintain Electrical Distribution Documents (What is that?)Aging Assets (Run to Failure Approach, No one wants to spend Time and Money until it breaks down)Intrusion by Animals into Electric Supply Substations

  • Potential Sources of Animal Outages

    Animals Percentage

    90%

    86%

    57%

    46%

    Cats 43%

    Mice 30%

    Rats 19%

    Opossums 13%

    Survey of 174 Public Utilities.

    114 Responded

    IEEE Std 1264-1993

    IEEE Guide for Animal Deterrents for Electric Power Supply Substations

  • Potential Sources of Animal Outages

    Animals Percentage

    Squirrel 90%

    Birds 86%

    Raccoons 57%

    Snakes 46%

    Cats 43%

    Mice 30%

    Rats 19%

    Opossums 13%

    Survey of 174 Public Utilities.

    114 Responded

    IEEE Std 1264-1993

    IEEE Guide for Animal Deterrents for Electric Power Supply Substations

  • Interrupting Devices and Key Components of MV Mining SwitchgearStationary Mounted or Drawout Vacuum Circuit Breakers Stationary Mounted Load-break and Non Load-break Disconnect SwitchesVacuum ContactorsNeutral Grounding ResistorsSurge ArrestersCurrent Transformers (CTs)

  • Interrupting Devices and Key Components of MV Mining SwitchgearPotential Transformers (PTs)Ground Monitors & Capacitor Trip DevicesStation Service Transformers (CPTs)FusesProtective Relays, Meters, Control Switches and Indicating Lights

  • Mechanical Endurance Capabilities and Maintenance

    Intervals

    Vacuum Circuit Breakers and Air-break Switches

  • Schedule of Operating Endurance Capabilities for Circuit Breakers (ANSI Std C37.06-2000)

    4.76kV, 15kV 600A-2000A (up to 31.5kA SC)No. of NO Load Mechanical Operations = 10,000No. of Load (Rated Current) Operations = 1,000Inrush Current Switching = 750No. of operations Between Servicing = 2,000

    One Closing+One opening = 1 Operation

  • Schedule of Operating Endurance Capabilities for Circuit Breakers (ANSI Std C37.06-2000)

    27kV, 600A- 2000A (up to 25kA SC)No. of NO Load Mechanical Operations = 2,500No. of Load (Rated Current) Operations = 200Inrush Current Switching = 100No. of operations Between Servicing = 500One Closing+One opening = 1 Operation

  • Periodic Inspection of Vacuum Circuit Breakers

    Maintenance Intervals are usually based on both, an elapsed time and no. of operations, whichever Occurs firstIf Short-Circuit Operation Occurs (major event) before the completion of listed operations, maintenance is recommendedAn Annual inspection for serviceability is recommended by most manufacturers

  • What is Recommended for Servicing Between Maintenance Interval (Breakers)

    Cleaning ContactsAdjusting and Tightening ContactsLubricating and Dressing Contacts

  • Mechanical Endurance for MV Switches ANSI Std C37.22-1997

  • Load Current Switching Rating for MV Switches ANSI Std C37.22-1997

  • Recommended Minimum Electrical Clearances for Indoor Switches & Buss

    supports (ANSI C37.32-1996)

  • Use Fluidized Epoxy Buss Insulation for Reducing Electrical Clearances

    Epoxy Powder Aluminum Foil Wrap

  • Silver Plating

    Uniform coating

    Fluidized Epoxy Buss

  • Maintenance/Inspection of Neutral Grounding Resistors

    Damage May Occur from:LighteningStormsEarthquakeWildlifeOverloadsExtended Service Life

  • Maintenance/Inspection of Neutral Grounding Resistors

    Periodic Inspection : Deenergize the system being grounded and break

    the connections between neutral and the grounding resistor

    An Isolation Switch may be used to break this connection

    Remove the front and rear covers for visual inspection of internal components

    Check for cracked insulators or bushings Perform Dielectric Withstand Test (Hi-pot) to

    ensure the insulation isolation

  • Maintenance/Inspection of Neutral Grounding Resistors

    Check the Resistive Element for continuity Check all internal connections for tightness Vacuum any dirt or debris from the inside of the

    enclosure Follow Manufacturers Maintenance Instructions

  • Surge Arresters - Short Cable Length

    BIL Margin is Reduced Appox 1.6kV/Ft

    Skirt-to-Skirt Clearance = 1/30kV BIL

  • Maintain Good Ground (Inspect Grounding Connections for tightness and Absence of

    Corrosion

  • Insulation Coordination When CTs are Mounted on Buss

    C-400 Class CT is bus mounted by using Polyester bottles with full coordination of Insulation and eliminating Corona

  • Disconnect Switches with Fluidized Epoxy Buss Insulation and Inter-phase Barriers

  • When Specifying Switchgear, Consider Unusual Service

    Conditions

  • Application Guide For Switchgear Unless Specified, Usual Service Conditions Apply

    Ambient Air Temp does not exceed 30C or + 40CAltitude does not exceed 1000m above sea levelAir is not significantly polluted (Pollution level 1 for I/D, 2 for O/D per IEEE C37.100.1)Relative Humidity (Average value) does not exceed 95% over 24h period & 90% over 30 day periodVibration does not exceed low level per IEEE- 693Solar Radiation does not exceed 1044 W/m sq (O/D Swgr only)Ice coating for exposed movable parts does not exceed 1mm (O/D only)Wind speed does not exceed 40 m/s or 90 mph (O/D)

  • Application Guide For Switchgear

    Unusual Service ConditionsAmbient Air Temp above 40 CCant exceed total temp (40C + 65C Rise = 105C)Continuous current rating must be de-rated per section 8.4 of C37.20.2Ambient Air Temp below 30 CUse Thermal insulation and Space heatingAltitudeHistorically, switchgear has been successfully applied at altitudes up to 1,000 m without the use of an altitude correction factor

  • Application Guide For Switchgear Unusual Service Conditions (Cont)

    For Altitude higher than 1 000 m, multiply the rated insulation levels at sea level by a factor Ka in accordance with Figure 1 of C37.100.1Hot and Humid ClimatesMake Fungus-resistant by means of:- Heaters & Ventilation- Fungus resistant coating for secondary wiring- Fungus and rust resistant property for paint Solar Radiation (O/D Switchgear)When Solar radiation must be considered for specific geographic location, refer to IEEE Std C37.24 for details

  • Maintain and Update Electrical Distribution Documentation

    Instruction Manual One-Line Diagram Three-Line and schematic Diagrams Wiring Diagrams Material List Utilize Mimic Buss for System Representation

  • System Representation with Mimic Buss

  • Switchgear Looks Nice when its New

  • What Happens if It is not Maintained

  • Reward for those who Maintain MV Switchgear

  • Reward for Maintaining Switchgear

  • References

    NFPA 70B 2000 Recommended Practice for Electrical Equipment Maintenance

    NFPA 70E-2000, Electrical Safety Requirements for Employee Workplace

    IEEE Std 1264-1993, IEEE Guide for Animal Deterrents for Electric Power Supply Substations

    IEEE Std 1584-2002, IEEE Guide for performing Arc-Flash Hazard Calculations

    NFPA 70-2002, National Electric Code

  • Questions?

  • Thank you

    Maintaining MV SwitchgearWestern Mining Electrical AssociationTucson, AZ November 15, 2007Maintenance of MV (Above 1000V and up to 38kV) SwitchgearWhy Maintain Switchgear?Why Maintain Switchgear?Getting Everyones AttentionWhy Maintain Switchgear?Factors affecting the Electrical Safety in Coal MinesFactors affecting the Electrical Safety in Coal MinesPotential Sources of Animal OutagesPotential Sources of Animal OutagesInterrupting Devices and Key Components of MV Mining SwitchgearInterrupting Devices and Key Components of MV Mining SwitchgearMechanical Endurance Capabilities and Maintenance IntervalsSchedule of Operating Endurance Capabilities for Circuit Breakers (ANSI Std C37.06-2000)Schedule of Operating Endurance Capabilities for Circuit Breakers (ANSI Std C37.06-2000)Periodic Inspection of Vacuum Circuit BreakersWhat is Recommended for Servicing Between Maintenance Interval (Breakers)Mechanical Endurance for MV Switches ANSI Std C37.22-1997Load Current Switching Rating for MV Switches ANSI Std C37.22-1997Recommended Minimum Electrical Clearances for Indoor Switches & Buss supports (