The composite insulators are applied on distribution and transmission lines since over 30 years. However, polymer materials can suffer from deterioration and aging especially in heavy polluted areas. The water-induced corona was also found as an important aging mechanism even in location with low contamination severities. Therefore the grading rings are often used to decrease electrical field near energized ends or even near grounded ends. Less popular is application of cap and pin insulator to decrease the potential on the HV electrode of composite insulator. This additional disc insulator can also be utilized as an indicator of composite insulator failure. The paper shows a few methods of indicator improvement or its sensitivity enhancement. Finally, the indicator for 110 kV line was designed and tested.