RESA Power

Stored Energy Hazards in Medium-Voltage Cable Testing

Medium-voltage power cables can store significant electrical energy during 44.0 kVAC VLF withstand testing, Tan Delta testing, partial discharge (PD) testing, and insulation-resistance testing at 5,000 VDC.

Because medium-voltage cables have capacitance, they can retain a potentially hazardous electrical charge even after the test voltage has been removed and the test set has been turned off. This stored energy can keep the power cable charged, until the cable has been properly discharged and grounded.

Stored electrical energy must be treated as a serious electrical hazard. Personnel must follow proper shutdown, discharge, grounding, and verification procedures before handling the cable, removing test leads, or making contact with conductors or terminations.
Always treat the cable as potentially energized until it has been properly discharged, grounded, and verified safe.

Proper shutdown, discharge, grounding, and verification procedures are essential before handling tested cables or disconnecting test leads.

Required controls include:

✅Verify the test set is turned OFF and the test voltage has been removed.
Verify the grounding/discharge equipment is connected to a reliable grounding point before discharging the cable. Always connect ground end first.

✅Allow the cable to discharge for the appropriate amount of time in accordance with the test equipment manufacturer’s instructions and established safety procedures.

✅Maintain a continuous grounding connection on the high-voltage conductor/stud while disconnecting, disassembling, or handling test leads and cable connections.

✅Keep the cable effectively grounded whenever personnel are working on or making contact with the cable. Maintaining the grounding connection provides a continuous path for stored or reappearing charge to dissipate safely.

✅Do not remove the grounding connection until all testing activities are complete and personnel are clear of the cable. After the ground is removed, the cable must again be treated as potentially energized due to the possibility of residual voltage building up.

✅Use the required PPE and properly rated grounding/discharge equipment throughout the process.

✅Treat the cable as potentially energized until it has been properly discharged, grounded, and verified safe.

Following these procedures helps protect personnel from hazardous stored electrical energy and establishes a controlled, electrically safe working condition during medium-voltage cable testing.

Location Spotlight: Huntsville, Alabama

Our RESA Power Huntsville team established a physical location in Cullman, Alabama, within the past year, giving our existing field service operation a local home base.

The team supports regional steel mills and pulp and paper facilities, along with nationwide commissioning and testing projects for EV charger installations.

The team’s capabilities include:

• Infrared (IR) scans
• UPS preventive maintenance
• Arc flash study data collection
• Switchgear installations
• Power monitoring

With these capabilities, our Alabama team helps customers assess equipment condition, plan maintenance and support new installations.

Learn more about our Huntsville team and its capabilities: https://www.resapower.com/locations/huntsville-alabama/

This photo shows part of a transformer degassing project that required 96 hours of oil processing.

Elevated gas levels were identified while the transformer was operating under load. The customer transferred the load to a second unit and took this transformer offline, allowing our team to perform the degassing work.

During the process, the transformer oil was heated and circulated through specialized equipment to remove accumulated gases. The radiator valves remained open so oil throughout the transformer could circulate. The open radiators also allowed heat to escape, so the team covered them with insulated blankets to retain as much heat as possible.

Keeping the transformer warm helps release gases held within its internal insulating materials so they can be removed through the oil processing system. The work continued for four days, requiring careful management of oil circulation and temperature throughout the process.

Degassing is one of the ways our transformer team helps customers manage oil condition and support the reliability of critical equipment.

Learn more about RESA Power’s transformer solutions: https://www.resapower.com/services/transformer-services/

Labor Day weekend is here, and it's a good moment to recognize the people whose work keeps businesses, infrastructure and communities running.

At RESA Power, that means technicians working safely in the field, teams testing, servicing and restoring critical electrical equipment, and the people behind the scenes keeping every job moving.

To our employees, thank you for the expertise, effort, and care you bring to your work and to our customers.

Have a safe and restful long weekend.

Who on your team deserves a shoutout heading into the holiday? Tag them below!

Although it reached 31°C (88°F) outside, safety standards never take a backseat. Jaxon Beier wore full arc flash PPE while switching, isolating, testing for absence of voltage, and applying grounds.

No matter the temperature, proper procedures are non-negotiable. In this photo, Jaxon is visually inspecting the disconnect switch blades to verify they are fully open before accessing the rear of the switchgear to test for absence of voltage and install grounding chains.

High-voltage work in full gear is tough work in the summer heat, which is why strict adherence to our heat stress management protocols including planned cool-down breaks and continuous hydration, is just as essential as the PPE itself.

There are no shortcuts when working on high-voltage equipment, and ensuring our team stays both safe and healthy on the job is always priority number one. Thank you Jaxon for all you do!

We're heading to Michigan Tech!
RESA Power will be at the Michigan Technological University Career Fair. Come meet our team and discover where a career in electrical power services can take you.

Tuesday, September 15, 2026
11 AM – 2 PM
Campus Mall
1400 Townsend Dr, Houghton, MI 49931

Tuesday, September 29, 2026
Noon – 5 PM
Student Development Complex at MTU

We're looking for driven students and soon-to-be grads ready to power what's next. Whether your background is in electrical, mechanical, or industrial engineering, or you're just curious about the field service and power solutions industry, stop by our booth to learn about internships, co-ops, and full-time opportunities.

Let's talk about your future. We'll see you there!

Contact us: [email protected]

Recently, our Transformer Solutions team traveled to Kentucky to perform a critical bushing replacement on a 305 MVA, 138 kV transformer.

Within 48 hours of receiving the call, RESA Power reviewed and analyzed the test results, developed a comprehensive scope of work and proposal, and mobilized a team with the required fluid processing equipment. This response took place over the course of a weekend.

Once the equipment was deenergized and made safe for service, our technicians drained the insulating fluid, removed the existing bottom connected bushings, and installed the replacements. The team then vacuum filled the transformer and performed electrical verification testing.

RESA Power’s large capacity oil processing rig, equipped with dual vacuum and booster pumps, played a key role in the project. The equipment allowed the team to efficiently remove, store, process, and return the transformer fluid during the replacement.

Thanks to the expertise and coordination of the RESA Power team, the project was completed safely, on time, and within budget. This project demonstrates our ability to respond quickly and successfully execute complex transformer work.

Following the successful completion of the project, the customer personally congratulated the team and recognized their efficiency, responsiveness, and commitment to quality and safety.

Learn more about RESA Power’s Transformer Solutions capabilities: https://www.resapower.com/services/transformer-services/

This is what uptime looks like.

Reliable electrical systems don’t happen by accident. Regular inspection and electrical testing of transformers, breakers, and switchgear can uncover developing issues before they lead to unexpected interruptions.

Visual inspections can reveal wear, damage, contamination, and other concerns. Electrical testing provides deeper insight into equipment condition and performance. Tracking results over time helps facility teams spot changes, prioritize maintenance, and plan ahead.

RESA Power field technicians inspect and test critical electrical equipment, giving facility owners the information they need to make informed maintenance decisions and support reliable operation.

Proactive testing is about more than finding problems. It’s about understanding equipment condition and taking action before a problem becomes an outage.

Learn how regular electrical testing can support the reliability of your electrical system: https://www.resapower.com/services/power-system-testing/