Other

Norscan, Inc.

Gilles Aminot

David E Vokey

Kenneth N Sontag

Open circuit faults in a cable are located by applying a step function DC voltage to one end of a conductor along the cable, for example the metallic shield along a fibre optic cable. The DC current along the conductor is measured over a sampling period and integrated to determine the capacitive charge on the cable. The distance between the end of the conductor and the open circuit fault is computed from the calculated charge and the known capacitance per unit length of the conductor. The DC current in the conductor is measured by sampling the current at a predetermined sampling frequency. The sampling frequency is preferably an integral multiple of the local AC mains power frequency, either 60 Hz or 50 Hz to eliminate the effect of induced AC voltages in the calculations. To eliminate the effects of a resistive fault, the method may include the steps of determining the conductor resistance and subtracting from the calculation of capacitive charge a DC fault current that is calculated from the conductor resistance and the DC voltage. An apparatus for carrying out the method is also disclosed.

Open cable locating for sheathed cables

A resistive fault location method and apparatus are used on communication and power cables. Two instruments are connected to opposite ends of the faulted conductor. Each takes a series of voltage and current measurements that are then processed to determine the distance from each end of the conductor to the fault. To eliminate voltage and current transients, the data collected is statistically analyzed and data that is analyzed as being affected by transients is discarded. The remaining data is taken as being steady state data. This eliminates any requirement for simultaneous measurements at opposite ends of the conductor and accounts for any situation where local transients at the two ends of the conductor are different at any given instant.

Method and apparatus for locating resistive faults in communication and

A novel method and apparatus are used for monitoring cables for wear and damage. The system is particularly applicable to a cable system with multiple branch terminations. The cables have detection conductors, for example the metal cable jackets or other detection conductors extending the length of the conductors. These are connected electrically at the splice points in the system. At the end of each branch and at the end of the main cable, the detection conductors are each connected to a novel termination circuit. In the normal monitoring mode, the termination circuit appears as an open circuit. A DC voltage is normally applied to the detection conductors. Any current is a result of current leakage at a resistive fault along the detection conductors. The termination circuits are activated by altering the DC voltage, e.g. by reversing the polarity and increasing the magnitude of the voltage. This causes the termination circuit to perform a series of functional tests. These include a loop test which places a short across the end of the detection conductor for a timed period. The resulting high level loop current is used to calculate the total detection conductor resistance. A second test transmits a coded signal simulating a triggered splice sensor unit. The signal is detected and decoded to verify proper operation of end to end coded signaling after completing a test cycle, the termination circuit turns off and the next termination to be tested is addressed.

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Ile des Chenes, Canada

Gilles Aminot