5. Isolator chains

The main insulator strings can be made up of cap-and-rod insulators (the most common in France, with the widespread use of tempered glass), or insulators with long ceramic shafts. Insulator strings for HVB lines are shown in figure 6 .

The advantage of tempered glass is that any perforated insulator is visible, which is not the case with insulators with ceramic cap and stem. Under the effects of excessive electrical stress, or even in the event of insulator failure, the skirt of the tempered glass insulator explodes, but the cover and stem remain attached, preventing the conductor from falling out.

In the...