Zinc Sleeve
Contaminated and wet insulators display a biased leakage current having DC component. This DC component causes electrolytic corrosion and reduction of pin diameter.
Pin Corrosion of suspension (disc) insulator
- Resultant reduction of mechanical strength
- Breakage of ceramic body due to expansion of pin
NGK developed Zinc Sleeve to prevent pin corrosion.
- Galvanically positive
- Large potential difference from iron
- Sacrificial electrode at cement boundary
- Bonded area of sleeve: Min. 80% of sleeve/pin interfacial area to prevent corona discharges
- Purity of zinc >- 99.8% to prevent granular corrosion
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