Test and operation of Petersen coil on 100-kv system of public service company of Colorado

THE HISTORIC Shoshone-Denver transmission line of the Public Service Company of Colorado connects the Shoshone Hydro Plant with Denver and serves important loads in the Leadville and Idaho Springs districts in Colorado (figure 1). The line traverses mountainous country for most of its length, crosses the Continental Divide three times (figure 2), and is badly exposed to lightning. The design and construction work on the line was begun in 1906 and 1907, making this line the pioneer in its voltage class. Conductor spacing and tower clearances are very close in comparison with modern standards, and although progressive improvements have been made, the operating record of the line shows an average of 60 tripouts per year, of which 42 are chargeable to lightning.