Design construction and tests of an artificial power transmission line for the Telluride Power Company of Provo, Utah

A description is given of an artificial power-transmission line which duplicates, in considerable detail, an actual transmission system. Each unit of the artificial line represents about ten miles of the actual line. Methods are given of calculating the correct distribution of inductance between self and mutual, and of calculating the correct distribution of capacity between wire and wire, and wire and ground. It is shown that this artificial system will duplicate very closely, even under extreme conditions of short circuits and grounds, many of the phenomena occurring on the actual system. A description is given of some oscillographic tests, made on this line, of the magnitudes and phase relations of current and voltage at different points, when the line was subjected to various types of short circuits and grounds. The data are presented in the form of vector diagrams; one for each point of the line where readings were taken. In addition to the diagrams, arrow-headed lines are shown at each station. These indicate the magnitudes and directions of power flow for each phase (as shown by star-connected wattmeters) and the total power flow. It is shown that the total power flow is not always toward the short circuit (or ground). Hence, two-wattmeter principle relays will not always indicate toward the short circuit (or ground) and may sometimes operate the wrong switch. With a three-phase short circuit the direction of power flow for each phase, and consequently the direction of total power flow, is always toward the short circuit. With a two-wire short circuit, if the phase rotation is A — B — C, and the short circuit is between wires B and C the power flow indication of the B phase wattmeter is, at all stations, toward the short circuit. The wattmeters for the other phases may indicate away from the short circuit. A ground on a single wire does not appreciably alter the power flow indication of any of the wattmeters, if the neutral is ungrounded. If the neutral is grounded, the power flow indication for the grounded phase is toward the ground at all points. If two wires are grounded at the same time, with the neutral grounded, the power flow indications are practically the same as for the two-wire short circuit.