Vikram Janardhan and Dudley Galloway, ABB Inc.
Every day, across the entire North American power grid, transmission and distribution system losses consume as much as eight to ten percent of the total net generation. About two-thirds of those losses are associated with wires, and the remaining one-third with transformers. Just over half the losses-around 55 percent- occur within the distribution system.
Distribution transformers dissipate about 45 billion kWh of electricity each year via load and no-load losses-enough power to require an additional 5,100 MW of generation capacity. You don’t have to be a rocket scientist, or even a power engineer, to know that those losses (and the associated generation needed to overcome them) add up to millions of dollars.
Now, imagine if there were a way to eke out a 10 percent reduction in losses on all distribution transformers in North America. The corresponding gains in efficiency would translate to 500 MW of freed generation capacity and savings of $300 to $500 million annually. But how does one expect to cut losses on distribution transformers by 10 percent and still maintain a reliable, steady flow of electricity?
This is not a perfect world, and there is no single answer to that question. However, there are a variety of options that a distribution company (disco) or local utility might pursue to mitigate transformer losses. Some of these involve leveraging new technologies, but others focus on simply building on the relationship discos have with energy customers.
- Take a close look at economic evaluation methodology and capital budgeting processes. Have they been the same for the last 10 years? Look at the ROI (return on investment) for all capital budgeting in light of the utility’s new post-deregulation charter.
- Encourage customers to alter their own load shapes. Most state public utilities commissions have programs to help utilities fund load curtailment initiatives. Tap into these resources to provide customers with energy information services that will educate them as to their usage patterns and enable them to shave some of their peak power consumption.
- Start obtaining interval meter data from the commercial and industrial (C&I) customer base. This process is minimally expensive, and can provide insights into the capacity loading of transformers. Meter data can be aggregated up to the zone/district level to provide valuable information on the projected load current that will flow through a distribution transformer.
- Be proactive about identifying overloaded transformers and take the opportunity to optimize systems by replacing them before an outage occurs.
- Call the manufacturer. Get educated on all types of performance information regarding transformers-maximum loading, thermal limits, no-load loss information, anything that will help optimize the transformer fleet.
- Make the best use of investments in SCADA/EMS systems. Use any capability for running single phase and three phase power flows to determine the projected losses in the distribution grid as well as the predicted power that will flow through transformers. (Remember that load losses of a distribution transformer vary with the square of the load current).
- Look into modern online diagnostic technologies for transformers-new sensors, new transducers, new data collection gateways. They cost much less than a transformer, but provide valuable information about loading patterns. This diagnostic technology has not reached D/T ratings yet, but it may in the future.
- Educate the C&I customer base about their obligation to maintain a particular power factor and penalize them if they don’t conform. Power quality can help extend the longevity of a transformer fleet. Large industrial customers that have a poor power factor inhibit the ability of the transformer fleet to ship ‘real power’ through them. Also, harmonic producing current may reduce the life of the apparatus and causes more losses.
- Keep an eye on industry-lead research and development initiatives to build and produce the next generation of distribution transformers. Some manufacturers are leading the way with development of technologies like superconducting cable and solid state devices that would produce a ‘clean’ sinusoidal wave shape.
- Look into buying advanced meters with loss compensation. As defined in the Handbook for Electricity Metering (EEI), loss compensation is “a means for correcting the reading of a meter when the metering point and the point of service are physically separated resulting in measurable losses including I2R losses in conductors and transformers, and iron-core losses.” For example, it may be desirable to measure the energy usage on the low voltage side of a distribution transformer that serves an industrial customer even though the end-point customer actually owns the transformer and is responsible for any transformer losses. In this case the utility billing point is actually the high voltage side of the transformer. Using loss compensation, the meter on the low voltage side of the transformer can actively adjust the energy registration to account for the losses in the transformer.
Obviously, some of these measures carry implications beyond the efficient operation of distribution transformers. But therein lies the point-distribution transformers are part of the larger distribution system and as the system changes, the methods used to evaluate and enhance transformer efficiency need to be reexamined.
Janardhan is a group marketing manager within ABB’s utilities division, focusing on IT solutions for retail, wholesale and central markets. He has an extensive background in power engineering and software product development. Dudley Galloway, formerly a project manager in ABB’s power technology products division, focused on distribution transformer technologies.
Janardhan can be contacted at email@example.com or 408-205-7377.