Abstract: An electrical communications system is described between a first environment and a second environment, having time-varying ground potential differences. The system includes a wire pair for carrying an electrical signal to be communicated from the first environment to the second environment; a first ground shield surrounding the signal carrying wire pair connected to a ground of the first environment; a second ground shield surrounding the signal carrying wire pair connected to a ground of the second environment; and a resistive element connected between the wires in the signal carrying wire pair having a value chosen so as to suppress any natural resonance characteristics of the cable structure.

Abstract: A master-slave current sensor system for measuring, for example, differential current on a transmission line is described. The slave current sensor can be periodically recalibrated (or have a compensation value re-calculated) based on the master sensor's average output, and the slave sensor can be unpowered and remote from an electronics box which receives its measurements. Health monitoring and fault location can also be performed using the master-slave optical current sensor system, optionally in conjunction with one or more voltage sensors.

Abstract: Systems and methods related to optical current and voltage sensors and, more particularly, to filters for use in such sensors. A fiber optic current sensor comprising: a light source; a polarization beam splitter connected to said light source having a reciprocal port and a non-reciprocal port; a Faraday rotator connected to said polarization beam splitter; a first quarter-wave plate connected to said Faraday rotator; a polarization maintaining fiber connected to said first quarter-wave plate; a second quarter-wave plate connected to said polarization maintaining fiber; a sensing fiber connected to said second quarter-wave plate; a detector connected to said polarization beam splitter via said non-reciprocal port and having an output; and an adaptive filter for filtering said output.

Abstract: A master-slave current sensor system for measuring, for example, differential current on a transmission line is described. The slave current sensor can be periodically recalibrated (or have a compensation value re-calculated) based on the master sensor's average output, and the slave sensor can be unpowered and remote from an electronics box which receives its measurements. Health monitoring and fault location can also be performed using the master-slave optical current sensor system, optionally in conjunction with one or more voltage sensors.

Abstract: Multi-phase, gas insulated electrical switchgear with optical voltage and/or current sensors are described. Compensation for contributions to sensor readings from non-associated conductors is provided. A processor is connected to voltage and/or current sensors which are placed near conductor whose voltages and/or currents are to be measured. The processor can receive outputs from those sensors and compensate the outputs for contributions which are attributable to sources other than the conductors which are intended to be measured.

Abstract: A sensor provides an analog sensor output signal that is first converted by a A/D converter, followed by a digital signal processor having a digital signal output that is converted to an analog signal by way of a D/A converter so as to provide an analog information output signal indicative of a parameter quantity intended to be sensed. An analog dither signal and/or a digital dither signal is provided for modulating the A/D converter input signal and/or D/A converter input signal, respectively, separately, or in combination, to enhance dynamic range accuracy of the resultant analog information output signal representative of the quantity of the parameter intended to be sensed.

Abstract: Multi-phase, gas insulated electrical switchgear with optical voltage and/or current sensors are described.

Abstract: A sensor provides an analog sensor output signal that is first converted by a A/D converter, followed by a digital signal processor having a digital signal output that is converted to an analog signal by way of a D/A converter so as to provide an analog information output signal indicative of a parameter quantity intended to be sensed. An analog dither signal and/or a digital dither signal is provided for modulating the A/D converter input signal and/or D/A converter input signal, respectively, separately, or in combination, to enhance dynamic range accuracy of the resultant analog information output signal representative of the quantity of the parameter intended to be sensed.

Abstract: In accordance with the preset invention, an optical interferometer employed as a current sensor is provided with visibility compensation and scale factor compensation. In accordance with the present invention, the interferometer is constructed so as to propagate a pair of optical beams along a defined optical path, where the optical interferometer includes a pair of optical beams that travel along at least a portion of the defined optical path such that a phase shift is induced between the pair of optical beams in response to a measureand, for example electrical current. At least one photodetector is responsive to at least a portion of the sum of the pair of optical beams and provide a beam output signal indicate thereof. From the beam output signal, a first signal is derived that is indicative of the visibility of the interferometer.

Abstract: A time division multiplexed optical voltage measuring system includes an optical voltage sensing system module including, (i) a plurality of optical sensors where each sensor is responsive to an input interrogation light wave, and (ii) one or more optical outputs affected by sensed electric field thereat. The optical voltage sensing system module includes an optical circuit arrangement having (i) an input for receiving a module specific pulsed light wave derived from a primary pulsed light wave from a remote light source, and (ii) arranged such that each of the plurality of optical sensors receives an interrogation pulsed light wave. The optical circuit arrangement of the optical voltage sensing system module further includes at least one optical wave combiner for combining like-kind of outputs from all of the plurality of optical sensors. The optical circuit is arranged such that the pulsed light waves from the outputs of different optical sensors arrive at the optical wave combiner at differing times.

Abstract: A sensor provides an analog sensor output signal that is first converted by a A/D converter, followed by a digital signal processor having a digital signal output that is converted to an analog signal by way of a D/A converter so as to provide an analog information output signal indicative of a parameter quantity intended to be sensed. An analog dither signal and/or a digital dither signal is provided for modulating the A/D converter input signal and/or D/A converter input signal, respectively, separately, or in combination, to enhance dynamic range accuracy of the resultant analog information output signal representative of the quantity of the parameter intended to be sensed.

Abstract: In accordance with the preset invention, an optical interferometer employed as a current sensor is provided with visibility compensation and scale factor compensation. In accordance with the present invention, the interferometer is constructed so as to propagate a pair of optical beams along a defined optical path, where the optical interferometer includes a pair of optical beams that travel along at least a portion of the defined optical path such that a phase shift is induced between the pair of optical beams in response to a measureand, for example electrical current. At least one photodetector is responsive to at least a portion of the sum of the pair of optical beams and provide a beam output signal indicate thereof. From the beam output signal, a first signal is derived that is indicative of the visibility of the interferometer.

Abstract: A method and system for aligning optical fibers includes aperturing the optical beams from the optical fibers at two points along a path. Photodetectors are placed on the apertures and the positions of the tips of the optical fibers are controlled using actuators to center the optical beams within the apertures.

Abstract: An economical but noisy laser is made to properly operate with a multimode speckle vibration sensing system, which requires very low noise at the frequencies of the vibrations it is to sense, by reflecting a small amount of the laser light back to the laser from an optical distance larger than twice the normal coherence length of the laser.

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: A current sensor coil design for reducing or eliminating long undulations of magnetic sensitivity. Such reduction or elimination improves isolation of the current sensor such that proximate currents and accompanying effects do not affect the accuracy of the current sensor determination of a current being measured. Several designs, which may be incorporated separately or in combination, include modifying the specifications of the quarter waveplate, cutting the fiber of the sensor coil to a proper length, choosing a proper perimeter length of the sensor coil or head, and using a particular length of fiber adjusted to work in conjunction with a multi-wavelength or broadband light source.

Abstract: A current sensor coil design for reducing or eliminating long undulations of magnetic sensitivity. Such reduction or elimination improves isolation of the current sensor such that proximate currents and accompanying effects do not affect the accuracy of the current sensor determination of a current being measured. Several designs, which may be incorporated separately or in combination, include modifying the specifications of the quarter waveplate, cutting the fiber of the sensor coil to a proper length, choosing a proper perimeter length of the sensor coil or head, and using a particular length of fiber adjusted to work in conjunction with a multi-wavelength or broadband light source.

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.

Abstract: A current sensor having an optmized optical fiber coil for sensing the magnetic field of a current of wire passing by or through the coil. The coil is optimally spun such that a particular ratio of the spin rate to the intrinsic polarization beat length is such for best maintenance of the circular polarization state of the light in the coil. The coil fiber may also be Terbium doped for greater sensitivity. The phase or birefringence modulation of the light may be piezoelectric or electro-optic. A Faraday rotator may be used in place of those modulators. The system may be open loop or closed loop. The feedback scheme may be via the modulator or the phase nulling current affecting the sensing coil.

Abstract: A fiber optic gyroscope having polarization error-correcting modulation. Polarization errors originate from the interference of primary waves and secondary cross-coupled waves. Although these error signals are very difficult to remove modulation signals may be applied to the integrated optics chip that minimize the total error over a period of time. By providing distinct but inter-related modulation signals to opposing inputs of the sensing coil, the various polarization errors can be averaged to zero over the period of the modulation signals.