Protection of a surge arrester with a better protection against failure from thermal overload in case of a temporary overvoltage in an electrical grid line

A disconnector device comprising:

• a first terminal configured to be electrically connected to one of a surge arrester or a ground potential;
• a second terminal configured to be electrically connected to the other of the surge arrester and the ground potential;
• a disconnector cartridge connected between the first terminal and the second terminal, the disconnector cartridge configured to operate in response to a current from an electrical line flowing across the disconnector cartridge;
• an outer housing defining a cavity around the disconnector cartridge, the outer housing configured to facilitate escape of gases and inhibit escape of solid particles from the outer housing, such that operation of the disconnector cartridge is configured to produce heated solid particles having enough energy to ignite a fire in a predetermined environment, wherein the heated solid particles have a minimum particle size, the outer housing further defining at least one outer ventilation opening connecting the cavity to an outside of the outer housing, the at least one outer ventilation opening being smaller than the minimum particle size to facilitate escape of gases from the outer housing and preventing escape of the heated solid particles;
• and
• an inner housing disposed within the cavity and disposed at least partially around the disconnector cartridge to define an inner cavity, the inner housing defining at least one inner ventilation opening configured to facilitate escape of gases from the inner cavity into the cavity, the at least one inner ventilation opening further configured to prevent escape of the heated solid particles.

An overvoltage protection assembly comprising:

• a surge arrester coupled to an electric line;
• and
• a disconnector unit comprising:
• a blank cartridge;
• and
• a first varistor element coupled between the surge arrester and a ground potential, the surge arrester configured to enter a conductive state in response to an overvoltage such that a current flows through the first varistor element to the ground potential to heat the blank cartridge to a predetermined temperature in response to the current flowing across the first varistor element before the current causes a thermal overload of the surge arrester, the blank cartridge configured to ignite at the predetermined temperature to forcibly disconnect the surge arrester from the ground potential before the current causes a thermal overload of the surge arrester.