ELPRO's Zinc Oxide discs, the prime elements for gapless surge arresters, incorporate the latest developments in metal oxide technologies and meet the stringent requirements of the relevant International standards.
The metal oxide discs are composed of a specially formulated compound of zinc oxide and proportionate amount of other selected metal oxides, a composition which has been arrived at through years of Research and Development. These ingredients are mixed in a powdered form, pressed to form a disc, and fired at high temperatures, resulting in a dense polycrystalline ceramic. The basic molecular structure is a matrix of highly conductive zinc oxide grains, surrounded by resistive intergranular layers of metal oxide elements. Under electrical stress, the inter-granular layers conduct, resulting in a highly non-linear characteristic.

Zinc oxide discs in MOGARD Arresters maintain a stable characteristic. Accelerated ageing tests show that arrester losses will not increase during an arrester’s service elife when exposed to a continuous steady state voltage. Stable Zinc Oxide Disc characteristics enable the MOGARD Arresters to maintain their low protective characteristics. As a result, equipment protection is never compromised. Factory tests are performed on each disc. Stability tests are conducted on each manufacturing lot to verify that the disc formulation and production processes are optimized. Every disc is submitted to an impulse current of 10 Ka, 8/20 microseconds to measure its discharge voltage. A disc strength test, consisting of multiple transmission line impulse is performed to ensure the disc has full energy capability. Resistive power loss is measured at maximum continuous operating voltage and visual inspection of the discs completed the routine tests

ELPRO's range of ZnO discs, manufactured in different diameter and height combinations, meet the specific requirements of Distribution Class and Station Class-I to Class-IV of lightning Arrester as specified in IEC 99-4, ANSI C62-11 and IS-3070 (Pt.3)1993 standards. Elpro’s Zinc Oxide Discs have been successfully type tested at CESI, Italy & KEMA, Netherlands. ELPRO's Zinc Oxide Discs, have been satisfactorily utilised by leading Lightning Arrester manufacturers in different countries including Italy, Korea, Russia, South Africa, Turkey Taiwan, Greece, France & USA amongst others.