Epoxy materials are excellent products for certain applications but not well suited for most leak repairs on transformers and circuit breakers, as shown. (This example is not at United Illuminating.)
The United Illuminating Co. (UI) regards the repair of oil and SF6 leaks as a critical component in its apparatus maintenance program. When a new leak is identified and immediate regasketing or replacement is not feasible, a temporary solution is scheduled to stop the leak. More than 10 years ago, UI began using outside specialists to seal oil leaks in its transformers and circuit breakers.
Previously, a special epoxy mixture was used to seal leaks at seams, pin holes, cracks and pipe connections. This option was easy to perform and inexpensive. However, the results were inconsistent. With proper preparation, the epoxy repairs were effective about 50% of the time. In addition, removal of the epoxy for regasketing or replacement was extremely labor intensive. The utility’s fleet was aging, and UI engineers were interested in a better solution.
The utility had an initial experience with an outside contractor to repair a leaking circuit breaker that was going to be removed from service soon. As a test case, UI tested a leak repair technique as a temporary fix. The intent was to get by until the unit was changed out. The contractor used a flexible sealant material that had advantages over epoxy and was more effective in sealing the leak. The results were good, and UI has used the outside contractor approach elsewhere. The time and total cost savings were substantial.
Leaks Are Serious
Oil leaks need to be taken seriously and addressed with a proactive and ongoing maintenance program. The major issues addressed with leak repair are as follows:
- Environmental issues. Some of UI’s substations are located adjacent to the Long Island Sound, streams or wetlands; therefore, environmental impact absolutely must be avoided and cleanup costs kept to a minimum.
- Public perception. In reality, leaks may be contained and not be an environmental concern. But, if they are visible to the public, perception becomes an issue.
- Equipment outages. The extended outages required for conventional repairs are often difficult to obtain. Leak repairs can be done in areas with limited access and require shorter outage durations. In many instances, repairs can be made with the equipment energized.
- Resource availability. Resources are limited, whether people, time or money, and UI needs to maximize these resources. Additionally, staffing levels are influenced by the state of Connecticut’s Public Utilities Regulatory Authority.
- Replacement parts. As with any aging infrastructure, original equipment parts are often scarce, difficult to locate, expensive or simply no longer available.
- Delivery times. Along with the availability issue, parts that are available or need to be custom manufactured often have long lead times.