Farnoosh Rahmatian

Integrated optics Pockels cell high-voltage sensor

The operation of the integrated optics Pockels cell and its application as a high-voltage power system sensor are explained. The effects of the waveguides geometry on the intrinsic phase-difference of the device is investigated. Properly biased devices as short as 7 mm have been fabricated and tested. While the piezoelectric behaviour of the sensor-heads affects the useful bandwidths of these devices, samples with bandwidths on the order of 1 MHz have been fabricated. Also, devices capable of reproducing lightning impulses with front-times as short as 0.5 /spl mu/s have been demonstrated. >

An ultrahigh-speed AlGaAs-GaAs polarization converter using slow-wave coplanar electrodes

A wide-band electrooptic polarization converter has been fabricated using slow-wave coplanar-strip electrodes on an AlGaAs-GaAs substrate. Microwave characteristics of the electrode have been measured up to 40 GHz. The microwave loss and the microwave index at 40 GHz are 0.4 Np/cm and 3.4, respectively. The optical measurements were done up to 20 GHz; a flat frequency response was observed.

230 kV Optical Voltage Transducers Using Multiple Electric Field Sensors

230 kV optical voltage transducers were constructed and tested. These transducers use three electric field sensors whose positions and outputs are selected and combined, respectively, in accordance with the quadrature method to obtain a voltage measurement. They meet IEC 0.2% class specifications and maintain 0.2% class accuracies even in the presence of electric field disturbances caused by local changes in geometry extemal to the transducer. The local changes in geometry used in the testing mimic those that may occur in a substation, e.g., installation or movement of equipment.

A new hybrid current sensor for high-voltage applications

This article presents a new hybrid electro-optic/inductive current sensor for metering and protective relaying applications. The sensor combines a Rogowski coil with a passive integrator located in the high-voltage environment. An integrated-optic Pockels cell (IOPC) having integrated electrodes provides optical isolation. Test results from 30 A to 30 kA show the sensor to be highly linear, exceeding 0.2% linearity standards. Temperature cycling tests show the ratio error to have a maximum value of 0.3% over the -30 to +70/spl deg/C range.

Accurate voltage measurement by the quadrature method

This paper introduces the quadrature method for measuring voltage using one or more electric field sensors. To date, all high-voltage sensors, from conventional inductive transformers to modern optical voltage transducers, have one or more of the following traits in common: large size and weight, high-voltage electrodes in close proximity, expensive and potentially hazardous insulation, and capacitive voltage division. Combined with the use of small electro-optic field sensors, the quadrature method enables voltage sensor designs that are free of these traits and that are, therefore, particularly ideal for high-voltage applications. It also allows for a trade-off between the accuracy of the voltage measurement and the number of required electric field sensors. Numerical simulations demonstrate the effectiveness of this technique.

Applications of Optical Current and Voltage Sensors in High-Voltage Systems

Various applications of optical current and voltage sensors are explored. Wide bandwidth, linearity, high accuracy, and light weight of these sensors make this technology suitable for numerous applications: high-accuracy wide dynamic range revenue metering, regular protection applications, capacitor bank unbalance protection (low ratio CTs), current measurement in HVDC systems, and power quality monitoring including measurement of harmonics near static VAR compensators and fast transient measurements. The fiber optic CT with a unique flexible head packaging (rope-shaped wrap-around sensor head) has novel application in generator monitoring and protection. Due to their light weight and ease of deployment, both the flexible-head optical CT and the optical VT are great tools as portable calibration systems for live in-situ calibration and monitoring applications

Velocity-matched electrodes for compound semiconductor traveling-wave electrooptic modulators: experimental results

Coplanar strips, capacitively loaded with fins and pads and capable of achieving the microwave/optical wave velocity-match condition in GaAs- and InP-based electrooptic modulators, are described. Measurements on electrodes, fabricated to have dimensions appropriate for use in conventional, Mach-Zehnder-type modulators in the 5-40 GHz range, show that these electrode structures can be made to obtain the desired match between the microwave effective index and the effective indexes of AlGaAs and InGaAsP optical waveguides, while having loss coefficients ~0.7 Np/cm at 40 GHz.

138 kV and 345 kV wide-band SF/sub 6/-free optical voltage transducers

This paper describes the design and testing of novel, environmentally friendly, 138 kV and 345 kV optical voltage transducers (OVTs) for metering and protection relaying applications in high-voltage electric power transmission systems. Each OVT uses three miniature optical electric field sensors housed inside a resistive shield. The locations of the electric field sensors, the electrical and geometrical parameters of the resistive shield, and the formula for deriving voltage from the electric field measurements are all chosen using the quadrature method to achieve very accurate voltage measurements. The resistive shield is, in turn, housed inside a hollow composite insulator filled with low-pressure dry nitrogen. Conventional accuracy and dielectric withstand tests demonstrate that the OVTs meet IEC 60044-7 0.2 and IEEE/ANSI C57.13 0.3 accuracy class standards and insulation requirements. Further tests demonstrate their wide bandwidth (>40 kHz) and show that they successfully reject the effects of the severest possible electric field disturbances on the voltage measurement.

Integrated optics pockels Cell as a High Voltage Sensor

The theory of operation of the integrated optics Pockels cell, for use as a high voltage sensor, is described. The results of measurements on various samples for bias, extinction ratio, and piezoelectric resonance are presented.

Wide-band 138 kV distributed-sensor optical voltage transducer: study of accuracy under pollution and other field disturbances

A 138 kV optical voltage transducer (VT) using shielded distributed electric field sensors is presented for use in high-voltage (HV) electric power transmission systems. Since HV and ground are kept far apart, the VT does not require oil or SF/sub 6/ for insulation; instead, it uses the environmentally friendly dry nitrogen as an insulating gas. A prototype has been tested for accuracy under various severe field disturbances including the presence of conductive pollution-like layers on the insulator and the presence of other HV sources nearby. The test results show that the VT meets IEC 0.2% and IEEE 0.3% accuracy classes under these extreme field disturbances. Data that demonstrates wide bandwidth of the VT are also presented. Another prototype has been tested and has successfully passed standard IEC HV dielectric withstand tests including power frequency withstand at 275 kV, partial discharge <5 pC, lightning impulse tests (BIL) at /spl plusmn/650 kV, and chopped impulse tests at -750 kV.