Trefoil clamps are used for high voltage single core cables where the current rating is high & 3 core cables are not available . Sumip trefoil clamps are used for laying single core cables in trefoil touching formation which helps to maintain magnetic symmetry thereby avoiding electromagnetic heating and loss of current .Sumip trefoil clamps have been moulded from glass fibre filled material . Advantage of sumip trefoil clamps High mechanical strength Center distance between trefoil clamps can be increased for lower fault level than 50 ka & hence total Requirements of clamps can be reduced thereby reduction in cost. Long service life as practically not affected by all chemicals, acids and alkalis. Design of clamp & good flexural strength gives good grip on cable & accommodates slight deviation in diameter of cable.