Switchgear assemblies installation

Since it is not practical to manufacture a llameproof enclosure due to its size and bulk and the number of knockouts and openings on the doors for switches, metering, indicators, and pushbuttons (PBs) etc., it is common practice to locate the.se assemblies some distance from the affected area in a separate well-ventilated room. Depending upon the location and intensity ol contamination, it may be permissible to meet the requirement by using a pressurized enclosure by maintaining a positive pressure inside the enclosure similar to that for motors (Section 7.1.3..3). When there arc many switchgear assemblies, the room itself can be pressurized, which is safer and easier. Small enclosures, however, such as a PB station, switch or a switch fuse unit or an individual starter unit etc., which can be easily made of MS plates or cast iron, as discussed in Section 7.13, can be mounted in the hazardous area while the main MCC can be installed in the control room, away from the contaminated area and from where the process can be monitored. 

In the cubicle construction of a switchgear assembly the busbar chamber is normally located at the top of the assembly and runs through the length of it. It is usually suitable for extension, through fish joints at either end, if required at a later date. For installations having top cable entry, the busbar chamber may also be located at the bottom of the assembly or the depth of the panel increased, with an additional shroud between the top busbar chamber and cable chamber. From these main busbars are tapped the vertical buses for each vertical panel. Manufacturers may adopt different practices for horizontal and vertical busbar arrangements to economize on their cost of production. We illustrate the most common types of busbar arrangements. 

Figure 13.48(b) A typical installation of a low-rating switchgear assembly on a cable trench... 

The same conditions would apply as for a switchgear assembly (Section 13.4.2). Unlike a controlgear or a switchgear assembly, a bus system may be required to be partly located outdoors. This is true for most installations, as the switchyard is normally located outdoors as is the feeding transformer, while, the switchgears are located indoors, to which the bus system is connected. 

General guidelines during installation and maintenance of a switchgear or a controlgear assembly 13/384... 

Installations prone to heavy vibrations and shocks stich as on the mounting platform near a laige power-generating unit, on a ship, locomotive and similar installations may require provisions to absorb shocks and dampen vibrations to prevent loosening of components and wire connections in a switchgear or a controlgear assembly. Some economical methods to achieve this can be by providing ... 

Particular requirements for low-voltage switchgear and controlgear assemblies intended to be installed in places where unskilled persons have access to their use. Distribution boards 8623-3/1993 BSEN 604.39-3/1991 ... 

Circuits are controlled by switchgear which is assembled so that the circuit may be operated safely under normal conditions, isolated automatically under fault conditions, or isolated manually for safe maintenance. These requirements are met by good workmanship carried out by electrically skilled persons and the installation of approved British Standard materials such as switches, isolators, fuses or circuit-breakers (IET Regulation 131.1.1). The switchgear must also be non-combustible or housed in a non-combustible cabinet or enclosure (IET Regulation 421.1.200). The equipment belonging to the supply authority is sealed to prevent unauthorized entry, because if connection were made to... 

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