A Practical Approach for Distribution Transformer Loss of Life Assessment Considering Electric Vehicles Penetration

The rapid and massive acceptance of electric vehicles (EVs) is causing challenges for distribution transformers (DTs) to operate over their expected lifespan. Unlike substation power transformers, whose life consumed/loss of life (LOL) is monitored by directly measuring winding temperature, the winding temperature of DTs cannot be measured in practice due to their massive population, inexpensive cost, and lack of remote communication. Thus, the LOL of residential DTs are required to be estimated by IEEE Standard C57.91-2011. This work proposes a hardware-free two-stage practical approach to assess the real-time LOL of a distribution transformer in residential premises. The first stage determines the kVA load of a DT, without the need of fixed power factor assumption. The DT kVA load along with the ambient temperature and DT thermal parameters are used for DT LOL assessment. Numerical validation is conducted on real-world data utilizing electricity consumption and ambient temperature of fifteen households in London, Ontario, Canada. The study in this work also includes the penetration of the most popular EVs in Canada, along with the service drop cable data as well as practical secondary distribution circuit configuration.