Transformer Loading Considerations and Future Implications Conventional Concepts and Challenges

1. Transformer Loading Considerations and Future Implications Conventional Concepts and Challenges By Henry Amy, EIT CPS Energy Underground Engineering Tulsa, Oklahoma SWEDE Conference 2018

2. Conventional Loading Considerations • Although transformers do not contain any moving parts, transformer components are still subject to degradation or wear that may lead internal damage rendering the transformer unserviceable. • Common points of failure for aged transformers exposed to prolonged use and substantial loading include the following: • Insulation Degradation • Winding Failure • Transformer Laminations • Transformer Oil • Primary Goal is the delivery of electrons to the end user in as reliable and as safe a manner as possible!!

3. Analysis and Process of Transformer Asset Dynamics Outputs • Database of vetted assets in need of replacement and delineated by risk associated with respective asset. • Asset Replacement Plans • Short-Term • Mid-Term • Long Range • Means to increase or sustain the fidelity of asset management files • Refined transformer records • Scrubbed transformer databases • Successes and Challenges encountered Feedback Asset Management and Power Quality Teams

4. Power Quality and Thermal Imaging • Thermal fault detection techniques provide the ability to diagnose potential concerns with equipment operation in a safe manner that does not require outages for the end user • Concerns When Delta T Threshold is exceeded • Presence of over-current conditions • Insulation breakdown/failure • Unbalanced load conditions • Core saturation, inducing voltage sag

5. Power Quality and Thermal Imaging (cont.) LF= 465 0.33

6. What’s the Bigger Picture?

7. Transformer Loading and Mobile Electrification • CPS Energy is at 95% penetration of AMI metering installations. Complete penetration will allow CPS Energy to leverage the benefits of AMI metering in anticipation of real-time load monitoring and the effects of EV Charging Load Dynamics. • Electric vehicles and charging stations will soon begin to densely penetrate many areas impacting transformers and related infrastructure assets • CPS Energy is will soon be engaged in several pilot projects and studies with AMI metering as the focal point in accommodating EV Charging loads to realize the impact to respective transformersand load profiles • AMI meters will serve CPS Energy well as the ability to monitor demand, consumption, hourly and/or 15-minute intervals to better address reliability concerns and load

8. Transformer Loading and Mobile Electrification • Electric vehicle charging will place new demands on padmount residential transformers however, AMI capabilities will allow us to better determine EV charging characteristics • As Electric Vehicles are flexible loads, the ability to load-shift with optimized charging will greatly benefit Utilities when meeting load demands • CPS Energy advocates a proactive approach to better prepare for the inevitable market penetration of electric vehicles and it’s impact to upstream transformer loads. • AMI meters are an integral component in alleviating the concerns of clustered EV chargers in residential areas and charging hubs in commercial areas (Figure 1) • Residential areas - Level 1 and Level 2 EV Chargers • Commercial area - Level 2 or Level 3 EV Chargers Figure 1. Types of EV Chargers

9. Grid Impact of EV Charging Load demand profile and electric car charging in the European Union a typical day, B2DS, 2030 Sources: IEA (2017b).

10. Questions ?

11. San Antonio, Texas