SuperPower will optimize their second-generation high-temperature superconducting (2G HTS) wire to provide a unique ‘low ac loss’ conductor that will significantly reduce energy losses in the proposed 28 megavolt ampere utility-scale transformer. It is estimated that 40 percent of the nation’s total grid energy losses are from aging conventional transformers and that the use of superconducting transformers could reduce energy losses on the grid by one-third – equivalent to eliminating about 15 million tons of CO2 annually.
The 28 megavolt-ampere three-phase medium-power transformer will be installed at the Southern California Edison utility substation by the end of 2012 and will integrate Smart Grid communication and control instrumentation. Following installation, a two-year test period will provide real-time data to validate Smart Grid business models, system performance, energy savings and improvements in power quality and reliability.
A transformer that incorporates superconducting wire can eliminate up to half the energy losses of transformers wound with conventional copper wire and results in a device that is about one-half the physical size and weight of a conventional transformer. This enables increased power handling capability without the requirement for more or larger substations in already crowded urban areas.
Beyond the energy savings, there are substantial environmental benefits. According to Drew Hazelton, principal engineer and project lead for SuperPower, “Conventional transformers are filled with toxic and flammable oil for cooling. Approximately one transformer catches fire or explodes each day in the United States. A FCL superconducting transformer mitigates both of these risks because it is cooled with liquid nitrogen, an inexpensive, readily available and benign substance that will result in a safer and ‘green’ device.”
Protecting the electrical grid from faults that result from lightning strikes, downed power lines and other system interruptions is critical to ensure a safe and reliable flow of power for consumers. By incorporating fault current limiting capability, the transformer is better able to handle fault currents that may arise from the Smart Grid goal of accommodating new generation and energy storage options such as renewable energy resources like wind and photovoltaic systems. The fault current limiting feature of the transformer provides critical protection and significantly reduces wear and tear for circuit breakers and other power equipment in existing substations. This reduces capital equipment costs for replacement or upgrade of such equipment and provides flexibility in routing power during emergency situations.
All power transformers are large, heavy, expensive, and generally use a paper/oil–based or hybrid paper/oil/solid insulation system. High-side voltage levels range from 35 to 765 kV. Prices for even the smallest units approach $100K, and several 100–200 MVA units easily sell for $1M. The large (up to 1100 MVA) GSU and HV transmission units are now approaching $3–5M or higher. Medium-power transformers for use in conventional substations have a nominal price of about $600K for a 50-MVA unit, but prices vary according to specifications, such as desired loss level and associated value of losses (A and B factors), impedance requirements, tap changers, cooling requirements, and accessories.
High-side voltages range from 35 to 245 kV with sizes ranging from 5 MVA to 100 MVA. Estimates by transformer manufacturers indicate that there are roughly 500 to 600 mobile transformers in service (slightly greater than 1% of the medium-power transformer inventory). Some of these transformers are quite old but are still serviceable because the number of hours that the mobile transformers are used is much lower than that of fixed installations.
So about 45,000 medium power transformers in the USA.
Peak electricity demand in the United States in 2004 was 700 GW (NERC, 2005). Assuming that an average of 2.5 medium- or large-power transformations are required from power plant to distribution system and an average size of 35 MVA per transformer, this suggests that there are roughly 50,000 high- and medium-voltage transformers in the United States.
Given a total installed market of 50,000 transformers, a 2% growth rate in electricity demand would require an additional 1000 transformers each year even without a replacement market.
MTS (mobile transformers and mobile substations) systems can serve a vital role in protecting the Nation’s electrical infrastructure. Their flexibility allows them to switch from one purpose to another relatively easily. When needed, the MTS enables temporary restoration of grid service while circumventing damaged substation equipment, allowing time to procure certain long lead-time grid components.
However, for seamless continuity of operation, it is critical that there is virtually a continuous supply of electricity. This can only occur through uninterruptible power supplies (e.g. batteries), redundant power feeds, and on-site generation. Yet, where disruption is prolonged due to equipment failure or total destruction from a war or act of terrorism, and especially where the problems are isolated to the substation, the MTS can play a critical role in reestablishing grid connections.