What is meant by a "dead tank breaker?"

A "dead tank breaker" refers to a type of circuit breaker that is designed such that its insulating structure is grounded. This means that the entire external structure of the breaker is at earth potential, which enhances safety by mitigating the risk of electric shock during maintenance, as the components are not energized.

In a dead tank breaker, the live parts, including the operating mechanism, are housed within a grounded tank, which is insulated from the ground by the porcelain or composite materials. This design creates a safer working environment when personnel are required to conduct maintenance or inspections. The grounding helps ensure that if there is any equipment failure or inadvertent contact with live parts, the current will safely dissipate to the earth, reducing the chance of electric shock.

The other options do not accurately describe the fundamental characteristic of a dead tank breaker. The arrangement of contacts through porcelain housing, the condition of the breaker operating mechanism, and whether personal protective equipment (PPE) is necessary when racking in or out the breaker while under load pertain to other operational or safety features but do not define what constitutes a dead tank breaker.