Since Hydro-Québec has been specifying IFDs in all new pole-mounted transformers for three years, total penetration is about 12%. Nevertheless, even with this fractional penetration, the company is seeing results.

After using the IFD for three years, Hydro-Québec wanted to assess the financial impact of introducing the IFD on pole-mounted transformers. To do this evaluation, Hydro-Québec first looked into events influenced by the presence of IFDs in transformers.

Experts were consulted to establish the impact of having, or not having, IFDs in transformers. These experts used reliability data, frequency and duration of events to build the business model for a single year of purchase of transformers equipped with IFDs. Finally, they built cash-flow models based on the impact of their data analysis.

The data showed that, typically, replacing a transformer requires:

• Four hours for a two-linemen team if they can use their equipment, such as a boom truck

• Six hours for a five-linemen team if the transformer is situated in a back-lot location.

In the case where there is no evident cause for the fuse operation, testing or inspection is required before re-energizing the transformer. These experts estimated that 70% of the time having an IFD-equipped transformer, diagnostic, testing and inspection prior to closing the fuse, can be reduced by 30 minutes to 1 hour.

When calculating the net present value of having certain transformer populations equipped with IFDs, the following hypotheses were used:

• Additional cost of the IFD: US$40

• Transformer life expectancy: 30 years

• Transformer's fuses operation rate: 3.8% (spread evenly over the life of the transformer)

• Annual purchase: 10,000 transformers

• Hourly linemen team rate: $232

• No dollar value for incident/accident reduction

• No dollar value for positive reliability impact (downtime reduction).

The resulting business case showed that on a 30-year planning horizon, the net present value for an additional dollar spent toward IFD installation in pole-mounted distribution transformers is estimated at $1.55. Additionally, in the long term, Hydro-Québec expects the IFD to provide better diagnostic information that should prevent nonrequired replacements of transformers (300 units per year estimated).

Furthermore, no dollar value was attributed to downtime reduction for customers and lower risks for linemen since these issues are strategic in nature.

From this data, the conclusion is that including IFDs in transformers is not only a good risk-reduction practice, but also produces an excellent return on the initial investment. More strategically, the IFD represents another small step on the journey to a distribution system where, more and more, information is used to improve customer service and the effective utilization and safety of valuable resources.

Daniel Desrosiers is manager of Research & Development and Special Projects at Hydro-Québec Distribution, and business risks coordinator for the Distribution Network business unit. He has more than 25 years experience in planning, engineering and operation of both transmission and distribution systems in Canada. Desrosiers is also acting as a designated expert on the IEC international standard committee related to network design, chairman of the Canadian National Committee, and he contributes actively to CEA technical committees. Desrosiers is a registered professional engineer. sdesrosiers.daniel@hydro.qc.ca

CEA Technologies Inc. analyzed how pole-mounted transformer tanks actually fail in service. Their report documents that of a population of more than 400,000 units, there were approximately 20,000 (5% of population) fuse operations per year. In these fuse operations, a total of 4000 units (1% of total population) failed per year. About one in 270 of the failed unit operations was explosive in nature. Or, there are about 15 explosive failed unit reclose operations annually. The population was in eastern Canada and the researchers expect that in areas with greater lightning activity, the percentage of failed units would be greater.

There are more than 50 million distribution transformers in service in North America. And, applying the CEA Technologies Inc. findings about failure incidence to this larger population, one would expect between 1100 and 1800 explosive transformer reclosings annually without IFD applications or if no checks or precautions were taken.