Surge arrester module and surge arrester

A surge arrester module comprising:

• a varistor stack comprising a plurality of varistor blocks stacked along a longitudinal direction of the surge arrester module;
• a pair of electrodes configured for sandwiching the varistor stack therebetween in the longitudinal direction, each electrode comprising at least one receiving hole;
• and
• a coupling assembly configured for coupling the pair of electrodes and holding the pair of electrodes and the varistor stack together, the coupling assembly comprising at least one rod, each rod comprising:
• a rod body extending in the longitudinal direction and extending into the receiving holes of the pair of electrodes, the rod body being made of insulating material and comprising a first interlocking portion in the form of a circumferential groove, wherein the groove lies within a plane having a normal vector parallel to the longitudinal direction;
• at least one sleeve being sleeved outside the rod body for attaching the rod to the electrodes, the sleeve being made of metal and comprising a second interlocking portion, the second interlocking portion in the form of a circumferential protrusion being adapted to fit with the first interlocking portion for preventing relative movement of the rod body and the sleeve in the longitudinal direction, and
• wherein the coupling assembly further comprises at least one nut and wherein the sleeve is threadedly connected to the nut.