METHODS AND SYSTEMS RELATING TO AC CURRENT MEASUREMENTS

摘要

Accurate measurements of electrical power at various points of a power grid is becoming more important and, at the same time, is getting more difficult as the old power distribution model of a few, large power generating stations and a multitude of relatively linear loads is replaced by a newer model containing a multitude of smaller, and to some degree unpredictable power sources, as well as a multitude of not always linear and often smart (essentially also unpredictable) loads. Embodiments of the invention provide for management of AC current measurements in the presence of a DC current. Such current measurement management including at least alarms, feedback, and forward correction techniques exploiting magnetic field measurements from within the magnetic core or upon the surface of magnetic elements and/or shields within the current transducer.

主权项

1. A method of improving the AC accuracy of a dual stage transformer comprising:
providing the dual stage current transformer comprising a plurality of magnetic cores, a primary winding, a first secondary winding, and a second secondary winding; at least one of:
providing a first resistor across the first secondary winding to generate a first voltage and providing a second resistor across the second secondary winding, the second resistor disposed in series with the first resistor in order to add a compensating voltage to the first voltage; andconnecting a first end of the first secondary winding to a first end of the second secondary winding and to ground and connecting a second end of the first secondary winding to a second end of the second secondary winding and to an input of a differential amplifier that has its other input coupled to ground, where the first ends of the first and second secondary windings are both disposed in the same direction along a magnetic core of the plurality of magnetic cores relative to their respective second ends; measuring a DC signal within the second stage of the dual stage transformer, the DC signal generated in dependence upon a DC aspect of a signal applied to the first stage of stage of the dual stage transformer; measuring an AC signal applied to the first stage of stage of the dual stage transformer, the AC signal measurement being made across the first and second resistors; and generating with a processing circuit a corrected AC signal measurement in dependence upon the measured DC signal and the measured AC signal.