Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Using radiant energy
Reexamination Certificate
1998-12-08
2001-09-04
Oda, Christine (Department: 2862)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Using radiant energy
C324S750010, C324S754120
Reexamination Certificate
active
06285182
ABSTRACT:
BACKGROUND
The invention pertains to sensors for measuring voltages. Particularly, it pertains to fiber optic sensors, and more particularly to such sensors not having a ground reference for measurements, and more particularly to such sensors have a time delayed self-reference.
One of the main difficulties of optical methods of sensing high voltage is related to the fact that optical sensors are typically inherent electric field sensors. In order to measure a ground-to-line voltage, the typical optical sensor needs to integrate the electric field over the entire distance from the ground to the voltage line. This approach requires that the entire voltage be dropped across the optical sensor. This is difficult and dangerous for application areas such as high voltage transmission lines. One solution to this problem is to implement a form of field control (e.g., capacitive dividers) such that a local electric field spanning the optical sensor is a fixed or a well-known proportion of the entire field. However, the latter approach adds considerable complexity and uncertainty to voltage measurements.
SUMMARY OF THE INVENTION
The present invention is a true dV/dt voltage sensor. There is no need for using a ground reference to measure high voltages with the present sensor. The sensor is connected at two places on the voltage line to be measured. The voltage wave has a delay between the two places on the line and the difference is optically sensed and converted into a voltage measurement.
Another approach is to connect the sensor at only one place on the voltage line. The other connection to the sensor is through time delay circuit that has an input connected to the same place. The delay between the one connection and the output of the time delay circuit is optically 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 or an integrated optic circuit (IOC), which is a light medium that has a birefringence that varies with changes of applied voltage. The variation of birefringence changes the polarization state of the light going through the device. The intensity of at least one polarization of light is detected and converted to an electrical signal.
Still another approach is to have the sensing device as an IOC which includes a Mach Zehnder interferometer, which is a pair of optical wave guides that has a phase modulation that varies with changes in applied voltage. This phase modulated beam interferes with an unmodulated or differently modulated beam producing an intensity modulation. The intensity is detected and converted to an electrical signal. The electrical signal is integrated into a signal indicative of the voltage being measured.
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Blake James N.
Lange Charles H.
Nxtphase Technologies SRL
Oda Christine
Pajak Robert A.
Zaveri Subhash
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