Abstract: A monitoring system for an electrical power transmission network or grid provides a recording network that can capture data on the response of the electrical power system over a wide geographical area to de-stabilizing electrical events. The captured data is obtained from multiple recording locations provided by individual recording units storing data on voltage and current on respective power transmission lines of the network. When an event is detected by one of the units, the central station interrogates the other units to obtain data based upon the same time as determined by a GPS clock at each unit and is thus automatically time-synchronized so that an overall coordinated snapshot of the power system dynamics is achieved. The wide-area capture is achieved through standard non-dedicated Internet, Intranet, and/or switched telephone network communication links.

Abstract: In many optics applications, it is desirable to retard the polarization of a light wave, i.e., to change the polarization state of a light wave. In a method for retarding polarization of a light wave, a first linear polarization-maintaining fiber having a first beat length is spliced to a second polarization-maintaining fiber having a high birefringence and a second beat length. The second fiber is then cleaved to a length which is a fraction of the second beat length. The first fiber and the second fiber may be secured in a removable or permanent capillary. A light wave is transmitted into the first fiber and the polarization state of the light wave is determined. To adjust the polarization state, the second fiber may be lapped against an abrasive substance. The second fiber may be repeatedly lapped until a desired polarization state is achieved.

Abstract: A sensor that measures a difference of currents at two locations along a conductor. The sensor uses two fiber optic current sensors. One current sensor at the first location measures current and has a nulling coil about its sensing loop, which carries current to null out the reading of current. Another current sensor at the second location measures current and also has a nulling coil about its sensing loop. The nulling coil of the latter sensor has the same current as the nulling coil of the sensor at the first location. For similar current sensors sensing the same magnitudes of current at their respective locations will have their outputs nulled to zero.

Abstract: An apparatus for monitoring and controlling the operation of an electrical power transformer includes a processor with input transducers for providing to the processor inputs indicative of electrical current in a winding of the transformer and ambient temperature outside the transformer. The processor is arranged using an algorithm based upon heat transfer to repeatedly calculate a first prediction, based upon the present values of electrical current and ambient temperature, of a time period before the hot spot temperature exceeds a pre-set allowable maximum and a second prediction, based upon the current value of power, of a time period before the accumulated loss of life exceeds a pre-set allowable maximum. If the shorter time period of the two calculations is less than a pre-set value, for example one half hour, the processor generates an alarm signal and a display counting down the time remaining in the period, together with a second alarm signal at a shorter second time of for example one quarter hour.

Abstract: An interferometric sensor having an optic fiber which forms a sensing loop optical path and a second loop that is wound in the opposite direction of the sensor loop. Circularly polarized light propagates along the optical path of the sensing loop. A differential phase shift is induced in the light waves by a magnetic field of the current in a conductor. The light waves with their phase relationship are detected by a photo detector which outputs an electrical signal that is processed by loop closure electronics into a signal indicative of the current's magnitude and direction. If the phase shift due to rotation is sensed in the sensing loop, then that phase shift is canceled by an opposite phase shift from the compensating loop. The compensating loop or coil may be reversed in connections, or flipped over, for calibrating the current sensor.

Abstract: A true dV/dt voltage sensor having no need for a ground reference for measurement. The sensor is connected at two places on the electric line to be measured. The voltage wave has a delay between the two places on the line and the difference is sensed and converted into a voltage measurement. Another approach is to connect the sensor at one place on the electric line. This approach has the second connection through a phase delay circuit that has an input connected to the same place. The delay between the one connection and the output of the phase delay circuit is sensed and converted into a voltage measurement. The sensed difference is a voltage, which is applied across a device, such as an electro-optic crystal, an integrated optic circuit (IOC) or a Mach Zehnder interferometer, which is a light medium that has a birefringence or an index of refraction that varies with changes of applied voltage. The variation of birefringence changes the polarization state of the light going through the device.