Path 15

Portion of the north south power transmission corridor in California

Path 15 is an 84 mile (135 km) portion of the north–south power transmission corridor in California, U. S. It forms a part of the Pacific AC Intertie and the California Oregon Transmission Project. Path 15 is part of The Western Electricity Coordinating Council's links of electrical intertie paths in the western United States. Path 15, along with the Pacific DC Intertie running far to the east, forms an important transmission interconnection with the hydroelectric plants to the north and the fossil fuel plants to the south. Most of the three AC 500 kV lines were built by Pacific Gas and Electric (PG&E) south of Tesla substation. Path 15 consists of three lines at 500 kV and four lines at 230 kV. The 500 kV lines connect Los Banos to Gates and Los Banos to Midway. All four 230 kV lines have Gates at one end with the other ends at Panoche, Gregg, and McCall. There are only two connecting PG&E lines north of Tracy substation that connect Path 15 to Path 66 at the Round Mountain substation. The third line between Los Banos and Gates substation, south of Tracy, is operated by the Western Area Power Administration (WAPA), a division of the United States Department of Energy. This line was constructed away from the other two lines and is often out of sight. Most of the time the lines are in California's Sierra foothills and the Central Valley, but there are some PG&E lines that come from power plants along the shores of the Pacific Ocean and cross the California Coast Ranges and connect with the intertie. The Diablo Canyon Power Plant and the Moss Landing Power Plant are two examples.

The route is generally west of Interstate 5 from the Los Banos substation, west of Los Banos, to the Midway substation, near Buttonwillow.

The two connecting PG&E power lines start at Round Mountain substation at Round Mountain. The parallel PacifiCorp and PG&E lines north of Round Mountain are considered to be Path 66, not Path 15. These connecting lines to Path 15 will consist of two 500 kV lines until south of Tracy. Heading south, the lines run through the foothills of the northern Sierra Nevada mountains towards the Table Mountain Substation
northwest of Oroville. The lines head southeast from Table Mountain Substation; near the Sutter Buttes the two lines separate. One line heads almost due south, passing to the west of Sacramento and east of Davis. The other line continues southwest for some distance and then turns south and enters the Vaca Dixon Substation along Interstate 505. The Vaca Dixon substation
was the world's largest substation at the time of its inauguration in 1922. Just north of the Sacramento River and the city of Antioch the two lines rejoin and head in a south southeasterly direction. The two PG&E lines span across both the Sacramento and San Joaquin Rivers on massive pylons along with the lone 500 kV Western Area Power Administration Path 66 line. Western's Path 66 line then turns east and runs parallel to the two PG&E lines to the west as all three lines head southeast. Both PG&E lines run to the west of the Clifton Court Forebay and cross Interstate 580 before entering the Tesla substation west of Tracy. The same line then heads into the Metcalf substation near San Jose and the Metcalf Energy Center. Leaving Metcalf substation, the line crosses the southern Santa Cruz Mountains with a 230 kV line and enters the large Moss Landing Power Plant substation in Moss Landing. The same line then heads east to rejoin the parallel PG&E lines at the Los Banos substation, effectively forming a 500 kV loop. Exiting the Gates substation , two parallel PG&E lines continue heading southeastward and one line heads southwest with a 230 kV line. This 500 kV line once again crosses the Diablo Range as it heads towards the Pacific Ocean. The line crosses Highway 101 in Atascadero and Highway 1 near Morro Bay. After crossing some rugged coastal hills, the line enters the Diablo Canyon Power Plant substation. Due to the massive amount of power generated by the plant, a second 500 kV line was built alongside the first, as the parallel lines head east to form another 500 kV loop. These parallel lines cross Highway 101 north of Pismo Beach and traverse over some southern coastal mountains. After reaching a height of over 1,200 m or 3,937 feet, Near Antioch the line runs parallel with the two PG&E lines. All three lines cross both the Sacramento and San
Joaquin Rivers on very large pylons. The WAPA line turns away from the PG&E lines and heads for another large substation near Tracy. South of Tracy Substation , it continues as a large, dual circuit 500 kV line that connects with the PG&E lines as they leave Tesla Substation.

Like Western Area Power Administration's 500 kV line, the tower design for the entire transmission system is not the same, although the difference is not as dramatic as on the WAPA line. For the PG&E line, the differences are subtle and from a casual, far away view, it looks like the towers are all the same for the entire power line. It seems to be south of the Table Mountain substation, the tower legs spread apart from the tower bridge (upper section of tower) down to the tower base and there are four guy lines for tower stability. In contrast, the towers to the north of Table Mountain have thinner legs and look like thin sticks from far away. The weaker tower legs have two additional guy lines for stability. As for the tower bridge, the towers south of Table Mountain have five X's in between the tower legs. The towers north of Table Mountain have only four X's. In addition, the tower arms on either side of the towers have smaller steel bars inside for added strength. In the northern towers, they are
positioned like equilateral triangles, but south of Table Mountain, they are shaped like right triangles. In order to do this the maximum south to north transmission capacity is 5,400 MW for most parts, California's governor, Arnold Schwarzenegger attended the commissioning ceremony at California ISO's control center in Folsom.