Substation Acceptance and Pre-Operational Testing Plan

Presented By:
Kenneth G. Peterson
Hampton Tedder Technical Services Inc.
TechCon 2018


Utilities have the right to verify that the services provided conform to their contractual requirements. A Utility may monitor the performance of the tests and test equipment certification in relation to the work performed as contractually required. The Contractor should develop an approved procedural test description/plan for the assets outlined within a contract or request for proposal. Current accredited National Institute of Standards and Technology (NIST) traceable calibration certificates for the equipment utilized during test of all assets should be provided upon request.

Today, more utilities are turning to contractors to build and commission their substation; as a result, having a detailed commissioning plan can eliminate costly downtime from undiscovered engineering design problems, manufacturing defects, and construction wiring errors. Examples of a proper test plan and illustrations of non-conformance to design will be shared with the audience.


Today more utilities are turning to General Engineering Firms and Contractors to perform turnkey construction services. Since the late 90’s, the utility industry as a whole has decreased their craft labor and/or in-house schools/apprenticeship programs. We at Hampton Tedder Technical Services have been a part of this shift since the late 90’s and have continued to utilize in-house programs as well as local IBEW union apprenticeships.

In general, utility companies are requiring more and more procedure specific documentation from contractors prior to performing work. Utilities have the right to verify that the service provided conforms to their contractual requirements. As a part of these contractual requirements, we have been tasked to provide test plans to ensure proper commissioning and safety standards are accepted. We have put together three examples of test plans on SF6 Gas Circuit Breakers to demonstrate basic standards and guidelines.

Example One (1) is a general outline layout based on in-house best practices developed with safety and general test procedures. This procedure demonstrates the best practices to follow with the test technician’s safety, equipment manufacturer’s guidelines, and the end user’s specifications, if applicable.

Prior to the start of the described test methodology, Hampton Tedder personnel are to check the equipment for the presence of voltage and confirm proper grounding has been installed within the project equipment and associated apparatuses.

The area under test shall have, at a minimum, a 6-foot caution tape barrier for each apparatus under test during over potential testing and/or as required to safe-off any area under test.

Position No. 1 – 66kV CB

  1. Safety
    1. Energized AC – wear appropriate PPE
    2. Energized DC – wear appropriate PPE
    3. Stored Energy – Keep clear of moving parts while operating
      and try to keep cabinet door closed as much as possible while
    4. SF6 – Read SDS for Hazards
    5. High AC and DC Test Voltages – safety switches, barrier
      tape, two people
  2. SF6 Filling and Testing
    1. Caution: Any unintentional releases of SF6 must be reported with an estimate of amount that is released. SF6 is considered a greenhouse gas.
    2. Fill SF6 to pressure as outlined by manufacturer’s guidelines
    3. Test SF6
  3. Timing Circuit Breaker
    1. Use manufacturer’s guidelines for timing results.
    2. Perform necessary tests as per UTILITY standards
  4. Power Factor Testing
    1. Use manufacturer’s guidelines for power factor results.
  5. Perform necessary tests as per UTILITY standards.
  6. DC Insulation Resistance Testing
    1. Apply DC volts as per manufacturer’s guidelines
    2. Perform necessary tests as per UTILITY standards
  7. Test Alarms and Controls of Circuit Breaker
    1. Follow manufacturer’s drawings to test all alarms
      1. Set any alarm set points as per drawings and UTILITY standards. – Record values
    2. Test Anti-Pump and Trip Free
  8. Current Transformer Testing
    1. Ratio
    2. Polarity
    3. DC Insulation Resistance
    4. Saturation Curve
    5. Resistance

Example Two (2) is a general overview to demonstrate using pre-established standards from a general engineering firm and/or utility company standard. As in Example One, general safety guidelines should be discussed in a preface section prior to the testing procedures.


  1. 3.1 SF6 Circuit Breakers and Circuit Switchers
    1. Perform all applicable tests and complete forms as described in Utility Company Specification 16833 Section 5.5
    2. Perform UTILITY COMPANY SOP: 521.420, Adding SF6 to gas circuit breakers, as required.
    3. Perform all applicable tests and complete forms as described in UTILITY COMPANY SOP: 521.161, GCB installation inspection & maintenance
    4. Perform Offline test instructions per section 9 of the Kelvatek Profile P3 operation manual. Complete the following forms/files
      1. HTE – High Voltage Breaker SF6
      2. Utility Company 521.161 GCB Check Sheet
        1. Note: Hampton Tedder shall utilize the HV Breaker SF6 data form for the HV Circuit Switcher SF6. This form has the same relevant field test data entries and is applicable to both types of hardware
    5. Track all SF6 Inventory and provide a final report to GENERAL ENGINEERING/UTILITY COMPANY
    6. Conduct visual inspection as per manufacturer’s recommendation
    7. Verify that nameplate data is in accordance with drawings
    8. Confirm correct application of manufacturer’srecommended lubricants
    9. Verify gas pressure gauges were within acceptable ranges
    10. Inspect anchorage, alignment, and grounding
    11. Perform all mechanical operational tests on both the Circuit Breaker and its operating mechanism
    12. Inspect bolted electrical connections and perform resistance measurements on all high voltage bolted connections, using a low-resistance ohmmeter
    13. Perform time travel tests
    14. Record as-found and as-left counter readings
    15. Perform test confirming that the Circuit Breaker opened and closed at the specified lowest control voltage
    16. Confirm auxiliary contacts per drawings provided by manufacturer
    17. Perform insulation resistance tests pole-to-pole, pole-to-ground, and across open poles
    18. Perform Doble Power Factor Test
    19. Check for gas leaks
    20. Verify correct operation of all air and SF6 gas pressure alarms and cutouts
    21. Verify tightness of all bolted connections using a calibrated torque-wrench
    22. Verify anti-pump function
    23. Verify operation of all heaters, gas pressure alarms and cutouts, as applicable
    24. Verify cable connections between poles
    25. Verify all additional alarms were ringing back to relays
    26. Test all pole-pole cables and control cabinet, as applicable

Example Three (3) is an example of an alternate source of specifications to follow published by the International Electrical Testing Association. As in the first two examples, general guidelines for safety should be discussed in a preface prior to the testing procedures.


  1. 3.2 SF6 Circuit Breakers
    1. 3.2.1 Visual and Mechanical Inspection
      1. Compare equipment nameplate data with drawings and specifications.
      2. Inspect physical and mechanical condition.
      3. Inspect anchorage, alignment, and grounding.
      4. Verify the bushing and insulators are clean.
      5. Verify both the circuit switcher and its operating mechanism mechanically operate in accordance with the manufacturer’s published data.
      6. Inspect bolted electrical connections for high resistance using one or more of the following methods:
        1. Use of low-resistance ohmmeter. See Section 7.7.2.
        2. Verify tightness of accessible bolted electrical
          connections by calibrated torque-wrench method in
          accordance with manufacturer’s published data or Table 100.12.
      7. Verify operation of SF6 interrupters is in accordance with manufacturer’s published data.
      8. Verify SF6 pressure is in accordance with manufacturer’s published data.
      9. Verify operation of isolating switch is in accordance with system design and manufacturer’s published data.
      10. Verify all interlocking systems operate and sequence per system design and manufacturer’s published data.
      11. Verify appropriate lubrication on moving current-carrying parts and on moving and sliding surfaces.
      12. Record as-found and as-left operation counter readings.
    2. 3.2.2 Electrical Tests
      1. Perform resistance measurements through all connections with a low-resistance ohmmeter, if applicable, in accordance with Section 7.7.1.
      2. Perform contact-resistance test of interrupters and isolating switches.
      3. Perform insulation-resistance tests on each pole phase-to ground.
      4. Perform minimum pickup voltage tests on trip and close coils in accordance with manufacturer’s published data.
      5. Verify correct operation of any auxiliary features such as electrical close and trip operation, trip-free, and anti-pump function. Reset all trip logs and indicators.
      6. Trip circuit switcher by operation of each protective device.
      7. Verify correct operation of electrical trip of interrupters.
      8. Perform dielectric withstand voltage test in accordance with the manufacturer’s published data.
      9. Verify operation of heaters.


The following illustrations were captured after a client put a 69~12kV transformer bank in service. The client commissioned the 69kV switchyard utilizing similar procedures discussed prior. The end user did not follow test practices described and tripped off-line after just a few days of in-service. The below photos were captured after discovering the differential protection tripped due to an open circuit current transformer.

Open Circuit CT Terminal Block
Transformer Control Cabinet Damage


  1. Field Data Forms HTE: High Voltage Breaker ANSI/NETA ATS: Standard for Acceptance Testing Specifications

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