Measuring methods and measuring apparatus, which determines whether a genuine and lasting errors to an electrical line is present or whether an of errors that was present only briefly the reconnection of a power circuit breaker and the blocks or releases

摘要

The circuit comprises an impulse transmitter and receiver connected to the line. When the circuit breaker opens on a fault a pulse is applied to the line and at the same time to a monostable switch. The echo from the line is detected, amplified and fed to a comparator together with the monostable output pulse. THe timing of the monostable pulse is such that coincidence of pulses only occurs if the echo comes from the line end. - With coincidence the circuit breaker is allowed to reclose. - If there is a time discrepancy between pulses the comparator gives an output which is used to lock out the circuit breaker reclosing circuits.