A string of suspension insulators consists of multiple porcelain discs connected by metal links. The potential across each disc is not uniform due to the presence of shunt capacitance between the metal fittings and earth. The disc nearest the conductor has the highest voltage. String efficiency is defined as the ratio of average potential difference across discs to the total potential difference across the string, and indicates how uniformly potential is distributed. Higher string efficiency corresponds to more uniform distribution. Various factors like number of discs, ratios of self to shunt capacitance affect the string efficiency.