Our thoughts and prayers are with everyone affected by Hurricane Harvey and Hurricane Irma. Heavy rains and subsequent flooding has stalled operations throughout affected areas.

Transformer faults are common after major weather events. Transformers have been pulled out of service and many more face imminent faults and failures due to submerged and weather-damaged equipment. The remediation and reenergizing of affected electrical systems is a complex and potentially dangerous process.  

Experts from SDMyers are here to help you bounce back. 



(Lines are open from 9 a.m. through 4 p.m. EST weekdays until October 1, 2017)

FREE 15-minute consultations for transformer owners who are dealing with deenergized, storm-damaged and waterlogged equipment. Call our hotline to speak with a Transformer Specialist about your situation and we will help you develop a plan to bring your operation back online.


These instructions outline the steps needed to inspect, test, remediate and energize systems after flooding.

These resources are not limited to SDMyers customers.

Please be safe. We wish you well in your continuing recovery efforts.



IMPORTANT: This information is provided for guidance only. Each piece of equipment is unique and for that reason manufacturer’s instructions for assessment, testing, maintenance, and energizing/de-energizing should be consulted and adhered to. As always, safety should be your number one priority and only qualified personnel should be permitted to perform services on your electrical equipment. SDMyers assumes no responsibility or liability for use of this information.


Has the transformer already had LOTO (lock-out tag-out) applied?

If the transformer was taken down by the storm, follow LOTO procedure to ensure safety of personnel working on and around the unit and to protect connected equipment.

Follow all safety procedures when entering the area. Additional precautions may be necessary if the unit is still underwater.


  • Ensure the unit is grounded.
  • Be careful of debris surrounding the transformer, especially in the vicinity of the conductor.
  • Check for evidence of a water line – how high is it? Was the transformer submerged?
  • Check pressure gauge and level gauge. If the level has changed and it is at ambient temperature and has a high level, water is likely in the bottom.
  • Open and inspect all electrical enclosures, junction boxes and conduit for water, debris, or visible signs of damage. Rigid conduit access covers should be removed as water can follow conduit.
  • Inspect insulators and bushings. Clean as required with denatured alcohol and cotton cloths.
  • Dry thoroughly.
  • Open and inspect Load Tap Changers and Bushing compartments. Most LTCs are free breathers and will require service and inspection following a hurricane. If water entered the LTC it will require service and an internal inspection. It will probably be necessary to drain and refill with new oil.

Any transformer with a lid seal (such as pole mount, pop-top types) should be inspected as bottom valves are not always on the bottom.

Cabinet (pad-mount) transformers are usually sealed and have a nitrogen blanket. Inspect all conduits and compartments. 


Draw a full oil test package.

A Karl Fisher water sample with an oil temperature will enable your testing vendor to calculate a Percent Saturation of the oil and provide an indication of the presence of excessive water.


If suspect or elevated moisture is found, the following steps are suggested:

ELECTRICAL TESTING: If free water or Percent Saturation is over 50 percent, perform an electrical test on the transformer. An Insulation Power Factor and a tip-up test and megger at a minimum.

OIL PROCESSING: If free water is determined, the unit will at a minimum require oil processing. Depending on the condition of the transformer, a vacuum dryout may be required (if the transformer is rated for such). 

Service aged and higher voltage transformers will have varying levels of power factor tolerance. Consult a transformer expert for guidance.

MOISTURE REDUCTION: The paper insulation retains more water than oil. An online dryer is needed to complete the drying of the insulation and to keep the oil dry.



IMPORTANT: The National Fire Protection Association recommends that all energizing procedures be carried out by responsible and qualified personnel (as stated in NFPA 70B)

  • With the above information, a determination for energizing is made.
  • Remove load for the energizing process as is possible.
  • Follow OEM manual for required set or idle times.
  • Ref: IEEE C57.93 and IEEE C57.140 Guides from Transformers Committee.


C57.93-2007 - IEEE Guide for Installation and Maintenance of Liquid-Immersed Power Transformers.

This guide provides guidance and recommended practices on the installation and maintenance of liquid-immersed power transformers rated 501 kVA and above with secondary voltages of 1000 V and above.

C57.140-2017 - IEEE Approved Draft Guide for Evaluation and Reconditioning of Liquid Immersed Power Transformers.

This guide provides guidance on insulating liquid maintenance and diagnostics, liquid reclamation, testing methods for the determination of remaining insulation (paper) life, and upgrades of auxiliary equipment such as bushings, gauges, de-energized tap changers (DETCs), load tap changers (LTCs), and coil re-clamping.

NFPA 70B - Recommended Practice for Electrical Equipment Maintenance.

This guide helps facility managers (and contractors) develop and carry out effective Electrical Preventive Maintenance (EPM) programs for all types of equipment and assemblies.

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