INTRODUCTION

One of the major operational hazards that may be encountered whilst operating a current transformer (CT) involves the secondary circuit being left in an open circuit condition, with the primary still energised. Open circuit conditions can occur inadvertently through routine maintenance of the burden or damage to the leads of the secondary circuit. High voltage transients may be generated in these situations and damage the CT winding insulation; possibly rendering it inoperable. In addition, these transients can cause high eddy currents in the CT core. These may be detrimental to the magnetising characteristics of the CT and result in errors in the measurement accuracy. A Metrosil Current Transformer Protection Unit (CTPU) provides protection against potential CT operational hazards. It is designed to permanently connect across the terminals of the CT and operate without the need for user intervention.