Inspection and Maintenance

Phase 1 – Online Inspection and Testing

Online inspection and testing allows plant operators to better plan for the maintenance of isolated phase bus systems by evaluating the condition of the bus while it is still in operation. A combination of visual inspection, Infra-Red thermography, and proprietary Electromagnetic Signature Analysis (EMSA) testing allows maintenance to be prioritized when needed to reduce occurrences of un-planned outages.

Visual Inspection:

Visual inspection of the bus system exterior will be performed to determine general condition and locate areas of concern for further inspection. The primary focus areas will include:


  • Condition of rubber bellows, evidence of water entry or degradation due to UV rays

  • Integrity of welds at duct connection and expansion joints

  • Effective low point drains

  • Evidence of overheating at grounds or steel supports

  • Condition of gaskets and covers, evidence of degradation which could allow water intrusion.

  • Alignment and settling of civil construction


IR Inspection:

With the unit operating at or near rated load, Infra-Red Thermography can be performed to locate any potential heating issues or circulating ground currents. The thermography will target the isolated-phase bus system enclosures, grounding, and steel supports while the bus is carrying near-rated current. This test can identify potential hotspots so maintenance can be planned at the next available outage.

In addition to the IR Inspection, a clamp on meter may be applied to exposed grounds that are accessible while energized to record current readings. If current or temperature is elevated there may be grounding issues causing circulating currents.


EMSA Testing:

EMSA (Electromagnetic Signature Analysis) testing can be performed to locate electrical partial discharge and arcing at defects. EMSA diagnostics measures a broad spectrum of radio frequencies to allow the EMSA engineer to view various patterns at each frequency including but not limited to corona, gap discharges, random noise and arcing. This test can be used in conjunction with local electromagnetic devices to identify and pinpoint defect locations.


Schedule: 1-2 technicians onsite for 1-2 days per unit


An inspection report documenting any issues discovered during the online testing will be provided, including areas flagged for additional inspections, pictures, measurements, and other condition details.


Phase 2 – Offline Inspection and Testing

General Condition Assessment: (Level 1)

A condition assessment inspection is a minimally invasive inspection used to follow up online testing if no major areas of concerns found. This assessment will look closer at common problem areas and areas flagged during the online inspection by removing covers to access the internal components of the bus to determine the overall system condition. A full exterior inspection of enclosures, rubber bellows, expansion joints, and access covers will also be performed to ensure there are defects or areas of potential water entry. Proper operation of heaters, forced-air cooling, or air pressurization systems will be checked. No gaskets or hardware will be replaced during this inspection unless an issue is discovered or they are damaged during entry.

Schedule: 1-2 technicians for 2-3 days per unit


An inspection report documenting any issues discovered during the online testing will be provided, including areas flagged for additional inspections, pictures, measurements, and other condition details.

Full Offline Inspection and Maintenance: (Level 2)

During a full offline inspection, all accessible interior and exterior areas of the bus are inspected and primary components are cleaned by hand, including insulators, flexible braids, and bushings. All gaskets and hardware on access covers will be replaced, as well as hardware at bolted connections. A borescope is used to reach inaccessible areas to ensure there are no hidden issues. A full exterior inspection is completed as described in the general condition assessment. Insulation Resistance and Dielectric Withstand (Hi-Pot) testing of the bus will be performed to evaluate the insulation system and detect deteriorating conditions that could lead to a ground fault.

Schedule: 4-5 Technicians for 5-8 days per unit


All primary components are cleaned by hand, gaskets and hardware replaced. If a serious issue is discovered, it will be immediately brought to the owner’s attention with mitigation or replacement recommendations. A report is delivered documenting condition of the bus, electrical testing reports, and recommendations for future repairs or system improvements.

Cryogenic cleaning: (Level 3)

Cryogenic cleaning utilizes pressurized dry ice blasting to clean dust and debris from the interior of the bus duct. This can be performed in addition to the hand cleaning to remove any potential contaminants and buildup within the bus. This service should be performed on bus systems where heavy foreign material and debris build up are expected within the bus, or after an arcing or fire event within the bus.

Schedule: 1-2 additional technicians per unit.


Optional: Replacement Rubber Bellows  


Over time, rubber bellows will wear from the elements, exposure to UV rays, and vibration. To prevent moisture ingress within the bus system, bellows should be replaced if they show signs of cracking and splitting. Temporary protection can be added to bellows for replacement of styles with longer lead times.


Optional: Replacement Flexible Braids

Flexible braids at component connections should be in good condition with no signs of corrosion, fraying, or deterioration of silver plating. Replacement braids can be provided for many sizes and ratings with quick turnaround (2-3 days).



Phase 3 – Follow-up Online Testing/Life Extension Evaluation/Engineered Solutions

If significant issues were found during preliminary online testing and mitigation efforts made during inspection and maintenance, a follow-up online testing and inspection can be performed. Before and after results are compared and analyzed to determine if the life of the bus has been extended or if additional repairs or replacement should be considered.

Bus condition can be evaluated and modifications proposed to extend the life of the bus, including addition of heaters, drain ports, and dry-air for moisture issues, or replacement of failing components such as expansion joints and rubber bellows discovered during inspection.

Upgrades to the bus ratings through cooling studies and the addition of FAC or sunshades can also be evaluated, or additions of online monitoring, heater circuit indicators, and other upgrades reviewed to ensuring the bus is operating at peak performance and free from defects or potential failure points.


Schedule: 1-2 technicians onsite for 1-2 days



Test reports and Recommendations




Online Testing and Inspection


Online testing and inspection to be performed while the unit is in service to evaluate condition of the bus and potential need for further inspections, allowing for better outage planning and scheduling of maintenance:


  • Visually inspect Bus Enclosure and supporting structure to verify conformance with as-constructed drawings. Check condition of all external bolted connections, supports, and concrete anchors.

  • With Unit operating at or near rated load for a minimum of 8 hours, and with ventilation system operating normally, perform Infrared thermal imaging measurement of the Isolated-Phase Bus Duct equipment, grounding, and supports to identify temperature hot spots.

  • Inspect the bus enclosure for proper grounding. Check grounding points with infrared camera, visually inspect cable and connection points for any abnormalities

  • Apply clamp-on meter to accessible grounds and record current measurements. (List potential issues as a result of circulating currents)

  • Check Steel connections and anchor bolts with infrared camera and visually inspect hotspots. Identify and mark all steel connections and concrete anchors which show evidence of heating. Visually inspect the concrete around anchors/supports for signs of cracking, spalling, discoloration.

  • Note the location of loose connections, damaged components, and faulty anchors on the as-built drawings.

  • Document hotspots or heating issues throughout the run with locations noted. Generate inspection reports on finding for each bus run

  • Optional: Perform EMSA (Electromagnetic Signature Analysis) testing to locate electrical partial discharge and arcing at defects. EMSA diagnostics measures a broad spectrum of radio frequencies to allow the EMSA engineer to view various patterns at each frequency including but not limited to corona, gap discharges, random noise and arcing. This test can be used in conjunction with local electromagnetic devices to identify and pinpoint defect locations.


Offline Testing and Inspection


  1. General Condition Assessment (Level 1)


Visually inspect the bus system interior and exterior to determine general condition or areas of concern for further inspection. The primary focus areas will include:


  • Inspection of any areas flagged during online testing, if applicable

  • General interior cleanliness

  • Presence of moisture or high humidity within the bus

  • Operation of heaters, if applicable

  • Signs of partial discharge or overheating connections

  • Clean undamaged insulators (Spot Check, 10-20% of system)

  • Undamaged, effective gaskets (Spot Check, 10-20% of system)

  • Condition of rubber bellows, evidence of water entry

  • Integrity of welds at duct connection and expansion joints

  • Operation of forced cooling unit (if applicable)

  • Operation of pressurized air system (if applicable)

  • Effective low point drains


   2. Full System Inspection and Maintenance (Level 2)


Exterior Inspections:


  • Inspect condition of rubber bellows, looking for evidence of water entry or degradation due to UV rays

  • Inspect integrity of welds at duct connections expansion joints, looking for cracks, pin holes, and other damage

  • Inspect low point drains obstructions (if inspection reveals low points where drains are not installed; drains should be added)

  • Evidence of overheating at ground straps or steel supports

  • Evaluate condition of gaskets and expansion/isolation joint deterioration, ground strap connections

  • Gasketed areas should not show degradation which could allow water intrusion. Gaskets and hardware on access doors will be replaced at all openings


Interior Inspections:

  • Using scaffolding (preferred) or scissor lift for access, open all covers and access portals and inspect all reachable components of the Isolated Phase Bus system interior, including but not limited to insulators, seal off bushings, termination assemblies, silver plated connections, conductor/enclosure assemblies, ground and expansion joints.

  • Interior should be free from dust, oil, contaminants, excessive moisture, and foreign material.

  • Insulators should be free from chipping, cracking, arcing, surface contamination, weld spatter, and discoloration. Hand clean accessible components with denatured alcohol and lint free rags to identify any cracks or deficiencies.

  • Insulator mounting hardware should be secure and free from corrosion

  • Seal off bushings should be inspected for evidence of contaminations build up. Disassembly could be required if issues are suspected.

  • Flexible braids should be in good condition with no signs of corrosion or fraying.

  • Silver plating on bolted electrical connections should be intact with no evidence of blistering, peeling, wear, or damage.

  • No evidence of corrosion (usually green in color) or discoloration from overheating at electrical connections.

  • Using a torque wrench, check hardware at bolted connections for proper tightness. No loose connections, no evidence of overtightened bolts or cold flow of materials around washers.

  • Check condition of laminated flexible joints for evidence of cracking at welds, fraying at material bends, or signs of material fatigue on conductor or enclosure.

  • Hand-held borescope will be used for inspection of hard to reach components. If location is inaccessible by borescope, an access hole can be cut to allow for inspection and sealed after, or an access panel added for future access.

  • If applicable, check for proper operation of forced-air cooling system.  The inspection of the forced air cooling unit may need to be a separate item.

    • With unit off-line and ventilating fans operating normally, measure air velocity and pressure drop across the cooling air heat exchanger.

    • Measure IPB internal air pressure with ventilation fans operating to evaluate whether IPB is airtight.

    • Check for balanced air flow at louvers, if so equipped, at generator connection area and GSU connection

    • Inspection of bus crossover deionizer screens (clean/repair/replace as required) if applicable

    • Inspection of the bus crossover damper louvers, actuator arm, and linkages for overall integrity (repair/replace as required) if applicable

  • If applicable, inspect air-pressurization system for proper functionality, positive pressure, and insect for locations of air leaks.

  • After all inspection, cleaning and testing activities are complete the bus will be returned to complete operating conditions as designed by the manufacturer. All inspection doors returned with proper gaskets and all hardware installed. Isolation bellows installed and sealed.

  • Any deficiencies will immediately be reported to contract representative with best practice ways to resolve the issues and plan of action for mitigation.

  • Pictures of as found and as left conditions will be taken for final report

  • An inspection report shall be generated with all findings and events logged for review. The report on findings will include written description of technical deficiencies with photographs, and markups on drawings. Recommendations will be provided for system improvement.

Electrical Testing:


  • Testing is to be completed prior to any cleaning and inspection, and after all inspection and cleaning work is complete.

  • Place an electrical clearance on the Unit to be tested.

    • Any electrical testing will be done with the bus completely disconnected from all other equipment including the generator, GSU, GCB, Stations Service Transformers, PT’s, etc.

  • Using a low resistance digital ohmmeter, measure bus mechanical joint resistance where applicable

    • If test results are high, disassemble the mechanical joints to perform a visual inspection of the mating joint surfaces for signs of sliver plating degradation or corrosion.

  • Measure Insulation resistance to ground for all three buses, one phase at a time.

  • Assuming IR is acceptable, perform high potential testing and measure leakage current at various excitation voltages.

    • High Potential Testing is the preferred method to test the dielectric integrity of the system after a complete and thorough inspection and cleaning. An AC or DC Hipot may be used.

    • AC High Potential tests will be performed at test values recommended per IEEE C37.23

    • DC High Potential tests will be performed at equivalent peak voltage of AC Hipot values

    • Hipot acceptance testing is pass/fail test if the bus can sustain a certain voltage for one minute. If leakage current differs greatly between phases (>50% difference), the cause for the differences will be investigated and the plant personnel notified.

    • A high capacity (5KVA minimum) AC Hi-Pot is required due to the capacitance of the system.

  • Reconnect flexible braids to generator, transformer, and auxiliary components. Close inspection cover plates.


   3. Cryogenic Cleaning (Level 3)


Level 2 Maintenance and inspection plan with addition of dry-ice cleaning.


Utilize low impact dry-ice blasting equipment to polish internal components and blow debris and contaminants out of the bus system, leaving behind no residue or moisture within the bus system.


Optional: Addition of inspection and cleaning ports in inaccessible areas for cleaning and to allow future inspection. Typical areas that this may be beneficial are at seal-off bushings and firestops that have a higher risk of failure and inspection covers are not commonly added.



  1. System Studies, Life Assessment, and Upgrades


  • Examine the IPB design, identify and confirm existing isolated phase bus ratings to include existing rated ampacity at self-cooled ratings and the existing rated fault current (rated withstand current, both momentary and short-time) per IEEE C37.23.

  • Evaluate bus system for increased cooling capacity, proposed solutions

    • Cooling study, addition of FAC

    • Addition of Sun Shields

  • Online monitoring options and installations

    • EMSA Online

    • PD Sensors

    • Humidity Sensors

    • IR or Fiber Temperature sensors

  • Life Extension assessment and solutions

    • Addition of pressurization or dry-air feeds, dessicant breathers

    • Addition of heaters, heater monitoring

    • Addition of drain ports

    • Replace failing components (Expansion bellows, seal off bushings, fire stops, etc.)

    • Add shrouds to bellow connections

    • Add access covers or viewing ports

  • Retrofit or replace existing components

    • Replace GCB, Transformers, Auxiliary compartments, CT, PT, etc.

    • Add GCB to existing iso-phase run

    • Add bus taps to new equipment



General Comments/Clarifications:

  • Pricing provided is firm.  Pricing is valid for ninety (90) days from the date of quotation.

  • Scaffold to be provided by site and is not included in this proposal

  • Pricing reflects site mobilization costs for equipment and personnel, one mob/demob is included in the proposal

  • Removal, handling, temporary storage and reinstallation of all covers, access doors/panels, bracing, supports, and other items required to be moved in order to perform the specified inspections and tests will be performed by RMS.

  • This pricing assumes non-union labor and does not consider prevailing wage

  • Up to 4 hours per person online or site-specific training included in budgetary price

  • Pricing does not include standby time, if encountered, standby time will be billed additionally per man, per hour, plus per diem

  • Travel, accommodations and living expenses for quoted personnel is included in pricing provided

  • Any delays/deviations/weather delays, beyond RMS Energy’s control, will be considered a change order and billed per the current RMS Energy standard rate sheet.

  • RMS assumes that the equipment is accessible, functioning as intended with no major issues and free of obstructions. If additional repairs required to ensure system functions as originally intended, additional charges may apply.

  • Any delays beyond RMS Energy’s control will be considered a change order and billed per the current RMS Energy standard rate sheet.

  • RMS assumes that the equipment is functioning as intended with no major issues. If additional repairs required to ensure system functions as originally intended, additional charges may apply.

  • RMS assumes that any deviation from the referenced scope of work will be billed on a T&M basis per the current RMS Energy standard rate sheet.

  • Requirements provided by site:

    • All switching, LO/TO, and isolation

    • Scaffolding

    • Sanitary Facilities

    • Power (120v, 480v)

    • Dumpsters

    • Access to RMS Energy equipment and materials

    • ccess and parking space near the equipment required for the inspection trailer. Equipment specifications:

      • Weight – 7,000lbs

      • Dimensions – 8ft x 16ft

    • Material transport from laydown area to work site

    • Adequate lighting is available, or temporary lighting is provided by others.

  • All testing and work performed by RMS Energy will be per applicable standards, requirements, or recommendations of: 

  • ANSI/NETA ATS-2017 Standard for Standards for Acceptance Testing Specifications 

  • National Electrical Code (NEC) 

  • Institute of Electrical and Electronic Engineers (IEEE) 

  • National Fire Protection Association (NFPA) Article 70 

  • Customer Specific Test Specifications 

  • Services to be performed pursuant to terms and conditions agreed upon by both parties or

  • RMS requires an executed purchase order or written notice to proceed prior to commencement of work.

  • Any applicable taxes are not included in our price.

  • Bonding not included in our price

  • If within (24) hours of scheduled work, the project is cancelled, RMS will bill for travel and per diems. This includes weather delays.

Copyright 2020 RMS Energy Co., LLC


Phone: 1-888-683-3630 | 24-Hours A Day




RMS Energy Co., LLC
201 1st Street
Randall, MN 56475


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