The NxtPhase electric field sensor forms the basis of the of the NXVT optical voltage instrument transformer. This innovative, patented device, utilizes the Pockels effect (linear change in the refractive index of a crystal in direct proportion to the applied electric field). Based on light passed through a crystal, the sensor uses with a titanium-diffused waveguide bonded to integrated optical fibers.

Linearly polarized light is coupled at 45o to the two fundamental modes of the crystal. The crystal is biased such that light exiting the crystal is circularly polarized with no field present; polarization becomes elliptical as the field is applied. Then a highly accurate, linear representation of that field is derived from the measurement of the dimensions of the ellipse.

The structure of the crystal & the method by which a normalized, two-channel signal travels down a single fiber allows measurements which are immune to temperature variation, vibration & changes in light intensity from the laser source.

Even more significant, this method derives a highly accurate voltage measurement from a field sensor without applying the entire voltage across the crystal. NxtPhase constructs optical columns with widely separate electrodes & no need for a capacitive divider or SF6 insulating gas.