Current transformer upgrades power analysis

Unit offers a high-precision alternative to current clamps in applications where current measurements need to be made on already installed conductors.

The SC1000 is a split-core DC current transformer that greatly increases the versatility of the Yokogawa WT3000 precision power analyser.

The new unit is designed to offer a high-precision alternative to current clamps in applications where current measurements need to be made on already installed conductors where disconnecting the cable is impossible or impracticable.

The accuracy of current clamps is limited to around 1%, which negates the main benefit of the WT3000 - its exceptionally high accuracy - but by using the SC1000 in conjunction with the WT3000 it is possible to achieve accuracy levels down to 1ppm.

The SC1000 is the first precision DC current transformer with a core that can be split to allow installation on an existing cable or busbar.

It is based on the zero-flux principle, in which the magnetic field around the primary conductor is balanced by the output current.

The unit features built-in electronics which generates a voltage output that is a precision scaled copy of the primary current over the full DC-100kHz bandwidth of the instrument.

It can carry out bipolar measurements over an input current range of 1000A.

Other features include automatic re-establishment of zero flux after a temporary loss of supply voltage or overcurrent, and an extra open-collector output to indicate that the unit is working properly.

It can withstand primary currents of up to 3kA.

The transformer can be mounted in any position, provided that the closing force on the gap is between 2 and 4kg.

The SC1000 was developed for Yokogawa by the Special Measuring Systems Division of Hitec Power Protection of Almelo, The Netherlands.

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