Spain Achieves Superior Transmission Protection and Monitoring

Challenge

Red Eléctrica de España is the transmission grid owner and operator for Spain. They own 220 and 400 kV lines and are responsible for the interconnection between France, Portugal, and Morocco. The Spanish power grid consists of long lines that are often heavily loaded. It has two submarine interconnections with Morocco and produces the second largest amount of wind power in Europe.Several factors caused protection challenges for the Red Eléctrica system:

Complex transmission—Frequent out-of-step conditions can damage equipment and cause system outages.
Renewables—The erratic nature of wind power can create system instability.
Single-pole switching—Careful coordination and special algorithms are needed to ensure proper protection under all conditions.

Red Eléctrica required an advanced protection and monitoring solution to improve system stability and address the system’s high level of complexity.

Solution

Red Eléctrica installed about 2,500 SEL-421 Protection, Automation, and Control System Relays across their system. By adopting the SEL-421 Relays, Red Eléctrica can maintain system stability. The SEL-421 solution provides advanced protection capability—including secure subcycle distance protection, single-pole tripping, and out-of-step blocking and tripping. Additionally, the 2,500 SEL-421 Relays provide synchrophasor measurements that enhance Red Eléctrica’s understanding and control of their transmission system.

Results

Using the synchrophasor capability of the SEL-421 Relays, Red Eléctrica can now measure their system’s behavior in near real time, which improves their system stability. The SEL solution addresses Red Eléctrica’s unique power system challenges by providing comprehensive, reliable, and secure protection for their transmission system.

Customer ProfileCustomer: Red Eléctrica de EspañaLocation: SpainIndustry: Electric UtilityApplication: Transmission Protection and Monitoring

“Our experience with SEL is good. We are very satisfied. We are using currently a central system to collect the records of the behavior of our relays.”

Julio Muñoz FlorezRed Eléctrica de España

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