Abstract: At an end (11) of a power transmission line (10), a fault detecting system monitors variations resulting from a fault in voltage and current being transmitted through the line and calculates the distance between the end and location (20) of the fault by the use of the variations and a line constant inherent to the line, such as that given by the characteristic impedance and the propagation constant, to thereby locate the fault with a sufficient accuracy by directly using the commercial frequency and without affected by the impedance that accompanies the fault. The system can calculate the fault impedance from the distance and those backward impedances seen at the end and an opposing end (12) of the line backwardly of the location of fault.

Abstract: A protective relaying system including a protected AC transmission line and detection means for detecting a change in propagation mode of a traveling wave propagating along the transmission line. The transmission line has a pair of line ends and a surge propagation time .tau., and the detection means is effective for comparing a value of the traveling wave as it passes one of the line ends at a time t-.tau. and a value of the traveling wave as it passes the other of the line ends at a time t after the surge propagation time has elapsed for detecting a change in wave value resulting from a change in wave propagation mode.

Abstract: A supervisory control system for an electric power system comprises a synchronized encoder for producing digital signals from voltage and/or current data detected by at least one of a number of detecting devices for such data coupled to the power system at various points. Inherently stationary data detected by similar detecting devices are converted into digital signals by asynchronous encoders. Responsive to such digital signals, data processing means produces address signals representative of the addresses of the detecting devices and processes the digital signals in compliance with programs for various supervisory control and with reference to the address signals to produce control signals, which are sent to circuit breakers, voltage regulators, and the like to protect the power system against troubles.

Abstract: A read-out signal generator supplies read-out signals through a read-out bus bar to sources of first data signals and buffer memories storing second data signals produced by accompanying central processing units (CPU's) to make the read-out bus bar transmit also the first and second data signals in timed relation to the read-out signals. A coupling device supplies read-in signals with reference to the read-out signals and transfers the first and second data signals from the read-out bus bar to a read-in bus bar, which supplies the transferred data signals to the CPU's in predetermined time relation to the read-in signals. The coupling device may either be a mere connection (in which case the read-out signals serve as the read-in signals) or a data bank.