ALTERNATING-CURRENT POWER DELIVERY SYSTEM

摘要

A power delivery system comprises a main circuit controller and a plurality of branch circuits that are in parallel with each other and in series with the main circuit controller. Each branch circuit has its own branch circuit breaker that can be opened to disconnect the associated branch from the remainder of the system. The main circuit controller comprises normally-conducting, current-limiting interrupting means and a resistor shunting said interrupting means. Means responsive to fault current through said main circuit controller and any one of said branch circuit breakers causes the interrupting means to operate with a current-limiting action that diverts the main circuit-controller current from the interrupting means into the shunting resistor. Means responsive to said fault current causes said one branch circuit to open while the main circuit-controller current is following a path through the shunting resistor. The interrupting means of the main circuit controller is reclosed immediately after the branch circuit breaker opens and interrupts the current therethrough. The resistor has an impedance no higher than about 18 percent of normal load impedance but sufficiently high to limit fault current therethrough under short circuit conditions to a value such that the current through any of said branch circuit breakers is within the maximum current-interrupting capacity of the branch circuit breaker.