Eagle Pass

The tie is helping to mitigate voltage instability, and enabling power exchanges between stations at Eagle Pass, Texas and Piedras Negras, Mexico.

The installation comprises two 36 MVA VSCs equipped with insulated gate bipolar transistors (IGBTs), operated with pulse width modulation (PWM). Ordered by the Central Power and Light Company (CPL), a subsidiary of American Electric Power Company (AEP), the project was executed jointly by EPRI, AEP, and Hitachi Energy.

Eagle Pass load is served by two 138 kV transmission lines, and load growth earlier made the area prone to voltage instability during peak periods, reducing the reliable power delivery on the U.S. side. During emergencies, load could be transferred from the U.S. into the Mexican transmission grid operated by CFE over a 138 kV cross-border tie but had to be interrupted because the two grids are asynchronous.

Commissioned in September 2000, the Hitachi Energy’S HVDC Light^® installation at Eagle Pass now mitigates any voltage instability and enables uninterrupted bidirectional active power transfer between the US and Mexican grid. This enhances the reliability of power supply on both sides of the border, without first having to disrupt service to distribution system customers.

In addition, the tie can be used to energize the Eagle Pass load area from the Mexican grid as the VSC technology has an inherent black-start capability.

The Eagle Pass HVDC Light tie is a first-of-its-kind installation, using VSC technology to both transfer active power between two asynchronous transmission systems and provide dynamic voltage support to the respective grids. It provides unprecedented operational capability, controlled bi-directional power transfer and voltage control.