Prepare for Maintenance Costs Today or Face Consequences Tomorrow

It’s worth noting that insurance providers may integrate NFPA 70B 2023 into their underwriting criteria. Failing to adhere to this standard could lead to heightened premium expenses and the potential for unexpected losses that regular maintenance can prevent.

NFPA 70B and ANSI/NETA MTS Guide for Electrical Maintenance Best Practices

Chapter 11 covers the maintenance requirements for “Power and Distribution Transformers”. There are 3 type of transformers covered;

• Dry Type, Air Cooled, Small, ≤ 600 Volts, ≤167 kVA single phase, ≤500kVA three phase Transformers
• Dry Type, Air Cooled, Large, > 600 Volts, >167 kVA single phase, >500kVA three phase Transformers
• Liquid Filled Transformers

Periodic maintenance is essential for safe and reliable operation of these critical parts of an electrical distribution system. Below are the highlights of the Power and Distribution Transformer chapter:

• Scope dry type and oil filled transformers.
• Maintenance Interval, refers to Chapter 9, Condition 1 = 60 Months. For liquid filled transformers there is an additional critical maintenance interval (Table 11.2) for sampling the insulation fluid. Insulation fluid samples should be done at least once a year.
• Visual Inspections
• Cleaning
• Mechanical Servicing
• Electrical Testing

One of the key elements of NFPA is Chapter 9 – Maintenance Intervals. Table 9.2.2 provides a minimum standard of maintenance intervals for all types of electrical equipment. This table is new and was not available in previous version of NFPA 70B. The table has three equipment condition assessments. Condition 1 is new installations or like new condition of the equipment. Condition 2 maintenance results deviated from past results, previous maintenance cycle revealed issues that require a repair or replacement condition or there has been notifications from the continuous monitoring system since the prior assessment. Condition 3 has missed two successive maintenance cycles that reported issues or there is an active or unaddressed notification from the continuous monitoring system.

ANSI/NETA MTS Standard for Maintenance and Testing Specifications has three separate chapters that transformer maintenance; Chapter 7.2.1.1 Transformers, Dry-Type, Air-Cooled, Low-Voltage Small, Chapter 7.2.1.2 Transformers, Dry-Type, Air-Cooled, Large and Chapter 7.2.2 Transformers Liquid-filled. These maintenance procedures are similar to NFPA 70B with the additions of several testing standards to follow:

• Scope Dry-Type Transformers
  • Visual and Mechanical Inspection
    • Visual Inspections
    • Cleaning
    • Mechanical Servicing
  • Electrical Tests
    • Small Dry-Type Transformers
      • Contact resistance
      • Insulation resistance
      • Turns ratio
    • Large Dry-Type Transformers
      • Contact resistance
      • Insulation resistance
      • Windings Insulation Power Factor
      • Turns ratio
      • Excitation current
    • Oil-Filled Transformers
      • Contact resistance
      • Insulation resistance
      • Windings Insulation Power Factor
      • Turns ratio
      • Excitation current
      • Sample the insulation liquid in accordance with ASTM D923, ASTM D3612 & ASTM D3613
    • Test Values – Visual and Mechanical
    • Test Values – Electrical

If your distribution system is served by an oil filled transformer, an annual oil sample analysis is the single most important test that can be done to determine the health of the transformer. EEE uses a well know Transformer Oil Analysis Laboratory to analyze and provides a preliminary assessment of the samples. The lab will run various tests to determine the breakdown voltage of the oil as well as other physical and chemical properties. Generally, the results will include measurements for color, dielectric breakdown voltage, dissolved gas analysis, dissolved metals, flash point, furan, inhibitor content, interfacial tension, moisture, PCB’s, power factor and specific gravity.

NFPA 70B provides guidance for the maintenance Intervals, equipment condition assessment, Maintenance Procedure and the minimum requirements for an Electrical Maintenance Program. ANSI/NETA MTS provides direction on how to perform the maintenance. Using both of these standards forms a successful path to a comprehensive Electrical Maintenance Program.