The use of auxiliary current-transformers for extending the range of metering equipment

The paper deals with methods of extending the normal range of alternating-current metering equipments. The various methods which have hithertobeen available for the purpose are first mentioned, and the reasons for their not having been brought into general use are briefly indicated. Results of an investigation employing small auxiliary transformers are then given, and details of the design and performance of such transformers are stated. Reference is also made to the methods of compensation which were used to overcome errors encountered under certain conditions, particularly in the case of low-grade main current-transformers. Finally, it is shown that the method is capable of giving accurate results over a range of 80/1 instead of the normal range of 20/1.