DIY Ring Light: Grounding Bulbs in Series
Assuming that it is an inhouse installation.

In practice, for lamps under 40~60W does not required grounding. For lamps 100W, grounding it is mandatory, as well as the use of porcelain socket. This fixtures provides a third screw for ground.



The main reason is to increase the safety in case of socket melting because of high temperature caused by lamp itself.

In any case sould be ensured that the live wire does not connected to the collar of the socket.



The main reason is to provide additional safety in case of removal of a brocken lamp.