Current Transformers

As high accuracy is required for measurement purpose and high operating values required for protection purpose, these two functions are met distinctly in a current transformer by providing metering core and protection cores separately with different functional properties. Now a days in view of high cost production of electrical energy, utilities specify very high accuracy class such as 0.5S & 0.2S (as per established standards) which measure energy accurately at a value as low as 1% of the transmitted current.

We at Suman Controls manufacture the class of cores also.

DESIGN We at Suman, depending on customer specification, manufacture two type designs.Live Tank Design & Dead Tank Design.

We also meet the customer requirement of provision to select different ratios on different Cores. The ratio of can be selected on Primary Side Selection Secondary Side Selection and a combination of the above two.

CONSTRUCTION OF CURRENT TRANSFORMER In addition to the above, a current transformer, being a series element has to withstand large dynamic forces and high thermal stresses during short circuit currents appearing in the lines at the incidence of a faults on the main lines to help clearing of such disturbance as early as possible. Adequate short circuit tests have been conducted on our Current transformers. We also under take to conduct these tests on specific request from buyers.

INSULATION High voltage, impulse and partial discharge tests to determine the quality of insulation between primary and other parts have been specified by standards to ensure the quality of insulation between primary and other parts. High quality insulation paper is used for main insulation of the CT between primary winding and secondary winding. In case of EHV Current transformers, the insulation will be segregated and sectionalised with introduction of semi conducting tape in between to see that the voltage distribution is uniform thus avoiding high level of electrical stresses. To eliminate dust settlement on the insulation during the process of manufacture endangering insulation, entire process of insulation is carried out in dust free chambers.

CORE and SECONDARY WINDING CRGO Silicon steel toroidal cores of high saturation and high permeability Mu metal are used for secondary winding and winding is equally distributed on the periphery of the core to reduce leakage reactance. Modified polyester enamelled copper wires of high purity are used in windings.

PRIMARY WINDING Primary winding used is of either flexible electrolytic copper conductor with double cotton covered or pure copper flats as per the requirement. Fibre sleeves are used for protection for primary conductor from inter turn faults.

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