1. Field of the Invention
The disclosed concept relates to a switchgear and, more particularly, to a switchgear wherein an enclosure housing assembly includes an extendable conductor assembly and a ground bus bar assembly that does not extend over the path of travel of a movable carriage assembly.
2. Background Information
Electrical switching apparatus, such as but not limited to circuit breakers, are often disposed in an enclosure or housing assembly. The electrical switching apparatus is disposed on, or is incorporated with, a movable carriage assembly. When the electrical switching apparatus need repair or other maintenance, the electrical switching apparatus is drawn, at least partially, from the enclosure. The removal of the electrical switching apparatus from the housing assembly may, or may not, decouple the electrical switching apparatus from the power source (hereinafter “line”) and/or the load. For the safety of the operators, a movable carriage assembly ground connection, i.e. a grounded conductor, is required by various regulations and safety procedures. For example, the frame of the circuit breaker is, typically, an electrically conductive material which needs to be coupled to ground whenever secondary wiring connections mate and/or become energized with electrical power
The ground connection allows the electrical switching apparatus to be in electrical communication with the ground continuously from the fully inserted/connected position until the electrical switching apparatus is drawn out a safe distance from the housing assembly. The purpose of this grounding feature is to protect operators from injury as a result of an electrical issue in the secondary control voltage system, which is typically less than 250 volts. The ground connection is also used with Ground and Test Devices that connect the primary voltage terminals, which typically can carry up to 15,000 volts, to ground so that the operators are protected while working on the conductor buses.
To allow for such a continuous ground connection, the housing assembly includes a large conductive bar (hereinafter “ground bar”), such as, but not limited to a copper bar, secured to the housing assembly. Further, the electrical switching apparatus includes a sliding electrical coupling that is structured to be slidably coupled to, and in electrical communication with, the ground bar. That is, the ground bar extends over the path of travel of the electrical switching apparatus so that as the electrical switching apparatus moves out of, or into, the housing assembly, the sliding electrical coupling moves along the ground bar maintaining the electrical switching apparatus in a grounded state.
Because advancing technology continually reduces the overall size of an electrical switching apparatus and the associated housing assembly, physically locating large conductive bars that extend the full length of the housing assembly is becoming increasingly difficult. Additionally, market demand for copper makes large ground bars expensive. By employing a short ground bar at the rear of the housing assembly, testing equipment can still effectively connect to, and provide the shunted path for, primary voltage and current; however, the requirement for a continuous connection throughout the draw-out range still must be met.
There is, therefore, a need for a housing assembly that provides for a grounded connection over the length of the draw-out path of travel but which does not include a long ground bar. There is a further need for such a housing assembly to accommodate existing electrical switching apparatus.