Maintenance Best Practices, Intervals, and Asset Management for Substation Equipment Presented by: Paul Schlies, President Energis Holdings, LLC
Background - 40 Years in the Industry • Education • NWTC (Northeast WI Technical College) • Work History • Wisconsin Public Service (WPS) – 24 years • American Transmission Company (ATC) – 6 years • Energis Holdings, LLC – 13 years • Formerly known as Energis High Voltage Resources, Inc.
Not One Right Way • There is not only one answer to a perfect Substation Maintenance Schedule. Today we’ll be using our industry and utility experience, but your engineering firm, the manufacturer’s equipment specifications, insurance requirements, and NETA Standards should also be considered. • Along with our recommendations, we’ve included survey results of maintenance schedules from individuals within the electrical utility. The information is included in the handout for your review, but because of today’s time limitations we will not discuss. • Electronic copies of this presentation are available.
Why Perform Substation Equipment Testing and Maintenance? • Safety • Public • Employees • Improve Reliability • Reduce customer outages • Reduce Costs • Reduce unplanned maintenance cost • Reduce insurance/liability cost • Plan and Budget Asset Upgrades • Bulk Electric Assets, NERC Compliance
Transformer Testing • Power Factor • Ratio • Insulation • Winding Resistance • SFRA (Sweep Frequency Response Analysis) • DGA and Oil Quality • Arresters
Transformer Maintenance Frequency • Monthly • Verify oil level in main tank & LTC • Verify oil level in bushings • Monthly • Verify insulator integrity • Monthly • Verify tank integrity and free of oil leaks • Monthly • Inspect surge arresters • Monthly • Verify paint is in good condition • Monthly • Record winding/liquid temperatures (current & max) • Monthly • Record LTC position indicator & operation counter • Monthly (current & max raise/lower) • Monthly • Verify correct operation of fans and free of bird nests • Monthly • Verify correct operation pumps (if applicable) • Monthly • Verify nitrogen pressure (if applicable) • Monthly • Verify transformer and pad are level • Monthly • Verify control cabinet is free of moisture • Verify cabinet heater operation • Monthly
Transformer Maintenance Frequency • Thermographic imaging (Infrared) • Annual • Transformer oil analysis (DGA and Oil Quality) • Annual • Power factor test • Every 5 years • Winding resistance test • Every 5 years • Transformer turns ratio test • Every 5 years • Insulation test • Every 5 years • Arresters • Every 5 years • Calibrate temperature gauges • Every 5 years • Verify alarm points • Every 5 years • Verify Buchholz relay operation • Every 5 years • Verify rapid pressure rise relay operation • Every 5 years • SFRA (Sweep Frequency Response Analysis) • New install & after fault operation • Vibration & acoustic testing • Dependent on criticality of equipment • LTC Internal Inspection • Every 5-10 Years
Industry Survey Results Transformers
Industry Survey Results Transformers
Industry Survey Results LTC
Circuit Breaker Testing • Power Factor ( 345kV) • Timing and Motion • Micro-ohm • Ratio Bushing Current Transformer (New, Suspect, Relocated) • SF6 Gas
Circuit Breaker Maintenance Frequency • Verify breaker is level • Monthly • Verify paint is in good condition • Monthly • Verify insulator integrity • Monthly • Verify SF6 gas pressure (check oil level in oil • Monthly breaker) • Record operation counter number • Monthly • Verify control cabinet is free of moisture and • Monthly cabinet is working • Annual • Check control voltages & operation of breaker • Annual • Thermographic imaging (Infrared) • Annual • Verify tank heaters (if applicable) • Every 5 years • Motion testing (speed test) • Every 5 years • Micro-ohm (ductor) contacts • Every 5 years • Test SF6 gas for moisture, purity & SO2 content • Check alarm points in control house • Every 5 years
Industry Survey Results Circuit Breakers
Industry Survey Results Circuit Breakers
Industry Survey Results Circuit Breakers
Industry Survey Results Circuit Breakers
Distribution Breaker Testing • Thermographic Imaging (Infrared) • Insulation Resistance Test • Micro-ohm Contact Resistance • Hi-pot Vacuum Bottles
Frequency Distribution Breaker Maintenance • Verify insulator integrity • Monthly • Verify control cabinet is free of moisture • Monthly • Verify cabinet heater operation • Monthly • Record operation counter number • Monthly • Thermographic imaging (Infrared) • Annually • Insulation resistance test • Every 5 years • Micro-ohm (ductor) contacts • Every 5 years • Hi-pot vacuum bottles • Every 5 years • Hi-pot oil • Every 5 years
Relay Testing • Perform as found test • Perform as left test • Test relays to installed setting • Trip test relays
Relay Maintenance Frequency • Check relays for damage • Monthly • Record targets found and reset • Monthly • As found test • 5-10 years • As left test • 5-10 years • Trip test relays • 5-10 years • Programmable relays • 5-10 years • Mechanical relays • Varies depending on environment
Voltage Regulator Testing • Maintenance usually based on manufacturer’s recommended operations and load. • DGA Oil Analysis • Frequency - Annual or Bi-annual
Disconnects & Surge Arrester • Disconnects • Micro-ohm • Insulation Test • Verify Mechanical Operation • Verify Electrical Operation (if applicable) • Frequency for All – Every 5 years • Surge Arrester • Check for arcs and burns • Check electrical connections
Circuit Switcher • Perform Monthly Inspections • Check for targets • Check insulators for cracks • Check blade is closed properly • Check heater in MOD is working • Check for moisture in MOD • Perform Yearly Inspections • Perform 5 Year Maintenance
Battery & Charger Testing • Specific Gravity • Cell Strap Connection Flooded Cell Resistance • Internal Cell Resistance • Voltage Readings Nickel kel Cadmium
Frequency Batteries & Charger Maintenance • Visual inspection of electrolyte levels • Monthly • Visual inspection of battery jars • Monthly • Verify no battery grounds exist • Monthly • Record battery voltage & current • Monthly • Specific gravity • Annual • Intercell impedance/resistance • Annual • Strap resistance • Annual • Individual cell voltages/total cell voltage • Annual • Equalize voltages • Dependent on battery test results • Verify charger alarms • Annual • Check voltage ripple • Annual
Industry Survey Results Batteries
Questions to Think About • How do you document the performed maintenance & testing results? • What type of test forms do you have? • Where do you have this information at your facility? • What are good utility practices? • What are the reasons for documentation of all testing and maintenance work performed?
Asset Management • What fits your company needs? • How big is your system • What are you going to want to track • Computerized system • Spreadsheet type system • What can it do? • Name plate information by substation • Inspection reports • Maintenance reports • Maintenance schedules • Build annual budgets • Justify asset replacement • Levelize maintenance cost
Reminder to all! Preventative Maintenance Plan Report (5-GF-113) PSC 113.0607(2)(b)6. Is due on or before May 1 (odd numbered years)
Failures and Their Cause “The why we do maintenance”
SF6 Breaker Leak (Video)
SF6 Breaker Leak Cont. • Cause: Age, lack of maintenance • Fault: None, SF6 moisture greater than 4x manufacture acceptable limits • Damage: • Corrosion on sealing surface was so severe • bushing top needed to be sent off to be machined • Increasing outage time. • Post Failure Assessment: SF6 leak was neglected for years, gas was added on regular basis by multiple un- qualified personal which ultimately led to increase in moisture and soon to be certain, fault.
Feeder Breaker • Cause: Animal • Fault: Started phase to phase, went phase to ground. • Post Failure Assessment: • Relay was not tested after new settings were uploaded. • Five (5) year maintenance was not performed on the relay. • Relay never saw the fault • System operations opened up down stream breakers • Damage: Feeder breaker, Power transformer, Station transformer, Underground cable, Arresters, Oil circuit breaker, Bus work, Bus PT’s, Disconnects and Steel structure.
Heating Connection • Cause: Dirty connection • Fault: None, excessive heating • Post Failure Assessment: • Terminations were not cleaned during assembly • annual infrared scanning was not performed • Damage: Aluminum conductor and breaker bushing top
GSU Transformer • Cause: Internal failure • Fault: Started phase to phase, went phase to ground • Post Failure Assessment: • Transformer was tested 7 years prior to faul • DGA showed signs of gas increase • Damage: 345kV GSU Transformer, Lost generation time
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