When an underground (Or overhead) cable fault causes a power outage, utilities are often forced to choose between leaving customers without power for days while repairs are completed or finding a faster way to restore service. This challenge has led to the widespread use of temporary power restoration equipment across the utility industry.
A Temporary Power Restoration Autotransformer is a specialized device that allows utilities to quickly restore electrical service to customers at the meter while permanent cable repairs are being made. Instead of waiting for crews to locate and fix the underground fault, utilities can install one of these devices to regenerate the missing hot leg or neutral. This approach can restore power in hours rather than days or weeks.
These devices, also commonly referred to as restoration auto transformers or phase restoration transformers, have become essential tools for modern utility operations. They are especially valuable during storm recovery efforts and routine underground cable faults. Understanding how a Temporary Power Restoration Autotransformer works, when it should be deployed, and what benefits it provides helps utilities reduce outage durations and improve overall service reliability.
Why Temporary Power Restoration Autotransformers Exist
Underground cable faults are one of the leading causes of extended power outages. When a cable fails, it can take significant time for crews to pinpoint the exact location of the fault, excavate the area safely, and complete the repair. During this period, customers remain without power, which often leads to complaints and reduced customer satisfaction.
Traditional repair methods require crews to work methodically through the entire process before power can be restored. While this approach ensures a permanent fix, it creates long outages that impact both residential and commercial customers.
A Temporary Power Restoration Autotransformer addresses this problem by allowing utilities to restore service at the meter quickly and safely. Once power is back on, crews can schedule the permanent repair during regular working hours or when conditions are more favorable, without leaving customers in the dark for extended periods.
How a Temporary Power Restoration Autotransformer Works
When one hot leg or the neutral conductor is lost on a single-phase service, a restoration auto transformer can regenerate the missing voltage using the remaining energized conductors.
The typical process follows these steps:
- A utility crew arrives at a location with partial or complete loss of power.
- The crew installs the Temporary Power Restoration Autotransformer between the meter socket and the meter, usually using a meter adapter.
- The device connects to the available good phases and creates the missing hot leg or neutral.
- Power is restored to the customer while the underground fault is located and repaired.
- Once permanent repairs are completed, the autotransformer is removed and the customer remains on normal utility service.
The device does not repair the cable fault itself. It simply allows the customer to receive power in the meantime, reducing the overall impact of the outage.
Utilities deploy these devices across a wide range of situations. Here are some of the most common use cases:
Common Scenarios Where Temporary Power Restoration Autotransformers Are Used
| Scenario | Typical Cause | Benefit of Using a Temporary Power Restoration Autotransformer | Recommended Device Type |
|---|---|---|---|
| Single home outage | Underground cable fault | Restores power quickly while repair is planned | 15–20 kVA unit |
| Multiple homes affected | Fault on main feeder | Keeps several customers powered during longer repairs | 30–50 kVA multi-home unit |
| Major storm recovery | Widespread underground damage | Enables fast restoration across many locations | Mix of wheeled and modular units |
| Planned maintenance | Cable replacement or upgrades | Minimizes customer outages during work | Size matched to service |
| Difficult access locations | Backyards, alleys, or rough terrain | Avoids delays caused by limited equipment access | Lightweight modular units |
This flexibility allows utilities to respond effectively to different types of outages while maintaining good customer service.
Benefits of Using a Temporary Power Restoration Autotransformer
Deploying these devices offers several important operational and customer service advantages:
- Significantly faster power restoration for customers
- Reduced number of customer complaints and outage-related calls
- More flexible scheduling for permanent repair work
- Lower overtime and emergency response costs in many cases
- Better crew safety by allowing repairs to be completed during daylight hours when possible
- Improved overall system reliability metrics
Because of these benefits, Temporary Power Restoration Autotransformers have become a standard part of utility response strategies across North America.
Types of Temporary Power Restoration Devices
Utilities generally use two main categories of equipment:
Wheeled Units These cart-mounted autotransformers are designed for locations with standard access. They are well suited for routine underground faults where crews can roll the unit directly to the meter. Common sizes include 15kVA, 20 kVA, 30 kVA, and 50 kVA models. Wheeled units are typically faster to set up when access is not restricted and offer good capacity for larger services.
Modular Hand-Carry Units These lighter systems are built for difficult access situations such as backyards, narrow alleys, stairs, or rough terrain. A typical modular system uses two 10 kVA units plus a control unit, allowing one person to carry the equipment where wheeled units cannot go. These are especially useful during storm recovery when many locations may have limited vehicle access.
Most utilities maintain both types of equipment so field crews can select the most appropriate solution for each job.
Temporary Power Restoration Autotransformer vs Waiting for Permanent Repair
Here is a clear comparison of the two approaches:
| Factor | Wait for Permanent Repair Only | Use Temporary Power Restoration Autotransformer |
|---|---|---|
| Time until customer has power | Days to weeks | Typically within hours |
| Customer satisfaction impact | High negative impact | Significantly reduced negative impact |
| Crew scheduling flexibility | Limited | Much higher |
| Risk of extended outages | Higher | Lower |
| Best suited for | Simple, fast-access faults | Most underground faults and storm recovery |
For the majority of underground cable faults, using a Temporary Power Restoration Autotransformer provides a much better outcome for both the utility and the affected customers.
Bridgeport Magnetics Temporary Power Restoration Solutions
Bridgeport Magnetics offers two primary product lines designed specifically for utility temporary power restoration needs.
The PowerBack series includes wheeled units available in 15kVA, 20 kVA, 30 kVA, and 50 kVA sizes. These are designed for standard access locations and are popular for both routine underground faults and larger service restorations. Many models offer optional GPS tracking for fleet management.
The Trident system is a modular, hand-carry solution consisting of two 10 kVA units plus a control unit. It is specifically engineered for difficult access locations where wheeled equipment cannot reach. The lightweight design allows one lineman to carry the components through gates, up stairs, or across rough terrain.
Both product lines are manufactured in Shelton, Connecticut, and are used by utilities throughout the United States.
Product Callout Bridgeport Magnetics PowerBack & Trident Series Temporary power restoration autotransformers for utility use. PowerBack wheeled units available in 15kVA, 20 kVA, 30 kVA, and 50 kVA sizes. Trident modular system uses two 10 kVA hand-carry units for difficult access locations. All units restore missing hot leg or neutral at the meter. Made in Shelton, Connecticut. Optional GPS tracking available on many models.
Learn more about Bridgeport’s temporary power restoration equipment
FAQ
What is a Temporary Power Restoration Autotransformer? A Temporary Power Restoration Autotransformer is a device used by utilities to quickly restore power to customers at the meter while an underground cable fault is being located and repaired. It regenerates the missing hot leg or neutral using the remaining good conductors.
Does the device repair the cable fault? No. It only restores power to the customer temporarily. The actual cable fault must still be located and repaired permanently by utility crews.
How long can these devices remain connected? Most utilities aim to remove temporary devices within a few days to two weeks once permanent repairs are completed. They are designed for short-term use only.
What size device is needed for a typical residential service? Most single-family homes can be restored using a 15 kVA or 20 kVA unit. Larger homes or services with higher loads may require 20-30 kVA units.
Are these devices used during major storms? Yes. Many utilities rely heavily on Temporary Power Restoration Autotransformers during storm recovery to quickly restore service to large numbers of customers while permanent repairs are prioritized.
