Preliminary Assessment of Joining the Sonora Power Network and Arizona System: Technical and Environmental Issues

1. Preliminary Assessment of Joining the Sonora Power Network and Arizona System: Technical and Environmental Issues PI: G. Heydt, Arizona State University, Tempe, Arizona Researchers: G. Karady, Arizona State University, Tempe, Arizona Jorge Ramírez Hernández, Universidad Autónoma de Baja California, Mexicali, Baja California Graduate researcher: Raúl Pérez Guerrero, Arizona State University, Tempe, Arizona Project duration: August 2005 – October 2006 Industry advisors: Dr. Arturo Messina, CINVESTAV, Guadalajara, Jalisco Dr. Jesús Rico Melgoza, Comisión Federal de Electricidad, Morelia, Michoacán Sr. J. Manuel Garcia, Comisión Federal de Electricidad, Hermosillo, Sonora Dr. B. Agrawal of Arizona Public Service, Phoenix, Arizona

2. The Present At present, there is no continuously operative electric power interconnection across the US-Mexico border in New Mexico or Arizona. On the Mexican side, the Comisión Federal de Electricidad (CFE) serves the electrical demand mainly from transmission circuits from southern Sonora. The rapid industrial growth in the southwest border region, on the US and Mexican sides of the border, suggests that an electrical connection across the border would enhance efficiency, reliability, and economy of operation. Electrical infrastructure is an important part of the local economy. A high voltage DC (HVDC) connection is proposed and studied.

3. In Mexico, the power system is a federal enterprise with a main AC network covering most of the republic. The extreme NW region is isolated from the remainder of Mexico and is connected to the USA at San Diego

4. The Texas AC system is asynchronous to the rest of the US Transborder connections in Texas are low power and all ACDCAC ties because the Mexican AC system is asynchronous to the US AC system The Baja California system is connected directly to the US near San Diego California – and this system is synchronous to the US system.

5. Factors favoring electrical interconnection • Industrialization in the border states of Mexico • Steady load Increase • Mexican state of Sonora one of the most impacted by this growth • Proposed interconnection to allow energy exchange between systems – sales of electrical energy across the border will allow both partners to utilize the cheapest available energy • Enhanced system reliability and conditions for future area development • Existing CFE system pressed to its limits in northern Sonora

6. Two logical intertie points, Nogales and San Luis • Nogales allows tie to the Mexican system better – shorter distances • Tie must be asynchronous (ACDCAC) • Studies show that ties in the 300 MW range are most cost effective. Modularity would allow upgrades at a later date • A tie at 138 kV or 69 kV would allow connection with existing systems on both sides of the border Point of intertie

7. Environmental issues • Electric fields: Exposure to electric fields has been a cause of concern due to their association with health issues. It has been reported that HVDC does not present the typical discomfort experienced by AC lines such as spark discharges from humans to vegetation. Ionic current streaming to humans standing under transmission lines is greater for AC systems than DC (approximately 100 times) for comparable systems. • Magnetic fields: Magnetic fields in HVDC systems are less significant than in AC lines and normally lie in the range of the Earth’s natural magnetic field. The maximum value of a 450 kV system (either monopolar or bipolar) is approximately 25 µT while the earth’s natural magnetic field is of 40 µT. This suggests that magnetic fields from HVDC should have little or no effect on humans or the environment. • Radio interference: The main source for radio interference in transmission lines is the corona effect due to the high electric potential of the lines. Corona discharges occur only at positive polarity showing that AC lines will suffer from this effect throughout all phases, while DC will only be limited to the positive pole conductors. • Audible noise: Although the noise produced by an HVDC installation is comparable to other sources, the high frequency component makes these installations to be a nuisance. Noise allowance depends on the geometry of the installation, but noise is generally limited to values lower than 35 – 40 dB immediately adjacent to the converter station. • Ground currents and corrosion effects: Corrosion is a relevant environmental issue in HVDC. This arises when the ground is used as a current path, corroding metal objects. This can be seen in monopolar HVDC configurations (not used in the U.S.) or emergency cases. Also, concentrations of chlorine and other compounds can be found in the vicinity of the electrodes but in negligible proportions. None of these effects occur in bipolar installations.

8. HVDC cable A typical AC  DC  AC facility

9. Estimated Converter Cost: 216.5 kUS$/MW • 86.6 MUS$ for total converter • Transmission Line Cost: 500 $/MW.km • Alternative 1: Length 90 km, 18 MUS$ • Alternative 2: Length 6.5 km 1.2 - 2.0 MUS$ • Differential Energy Cost: 10$/MWh • Average Load Factor: 0.7 • Expected HVDC income: 24,528 kUS$/year • Approximate payback period (300 MW installation, short DC transmission line): ~4.3 years

10. Benefits of an HVDC tie • Increase in power quality – and the potential to entice manufacturers to locate on the Mexican side of the border • Increase in power quality and reliability in the Nogales Arizona region and / or the San Luis Rio Colorado region, and the concomitant benefits to the communities nearby. • Potential for sale of electric energy generated in Mexico in the USA – and the potential benefits to the utility companies that enter into such an agreement and vice-versa • The increase in jobs that could result, on both sides of the border • The potential for the delay of construction of new generating facilities on both sides of the border due to transborder power sales • The effect of time zone differences (for about six months of the year, Sonora is one hour different from Arizona, thereby resulting in a different peak power demand time).

11. Acknowledgements This work was supported by the Southwest Center for Environmental Research and Policy The authors acknowledge the help of their colleagues at Arizona State University and the Universidad Autónoma de Baja California. Acknowledgement is also due to Dr. Arturo Messina of CINVESTAV in Guadalajara, Jalisco, and Dr. Jesús Rico Melgoza of the Comisión Federal de Electricidad in Morelia, Michoacán. Also, Sr. J. Manuel García of the Comisión Federal de Electricidad in Hermosillo, Sonora is acknowledged for sending valuable project data. The supportive comments of Dr. B. Agrawal of Arizona Public Service, Phoenix Arizona are appreciated.

12. Full engineering report available electronically –request from: heydt@asu.edu Questions? Comments?