MV Surge Arrester upto 45kV for substation protection from lightening and switching over voltages. In past 15 years, almost all high-voltage networks used MO arresters.  However, in medium-voltage networks,   a   substantial number of conventional gapped arresters (SiC resistors and series spark gaps) were  installed until  a few years ago. Today MO (Metal-Oxide) arresters without spark gaps have gained popularity. Networks require improved protection level and better performance in polluted environments. The switch to polymeric housings made it possible to do without the previously necessary spark gaps. Polymeric housings   are reliable against ingress of moisture and provide minimal risk of failures (violent shattering of the housing). MVSA are manufactured using high quality MOV blocks which display excellent thermal and current handling characteristics due to guaranteed homogeneity of the varistor volume.  In the wrap design surge arresters, the MOV blocks are wrapped with fiberglass ribbons impregnated with epoxy resin to create stacks of MOV blocks.