Switchgear assemblies ratings

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

Table 13.1 Rated voltages and frequencies for metal enclosed bus systems also applicable for switchgear assemblies...

The temperature rise limits of the various parts of a switchgear assembly during continuous operation at the rated current must conform to the values in Tables 14.5 and 14.6. 

The rating of an indoor or outdoor switchgear assembly is referred to at an ambient temperature of 40°C. For a higher ambient temperature the rating of the assembly will be reduced in the same proportion as for the busbar systems and as shown in Table 28.3. 

The rating of cuiTcnt-carrying equipment (switchgear assemblies, such as for the main bus system), devices (breakers, switches and contactors) and components (connecting links and wiring etc.) is defined by two parameters ... 

The switchgear assembly, its components and the bus system must be designed for the rated voltage and frequency. 

ANSI C-37/20C specifies this rating only for metal-clad switchgear assemblies and not for metal-enclosed bus systems,... 

During the test the main busbars are fed at the rated current, for which the switchgear assembly is designed. They are heated naturally and therefore no resistance of the main bus need be measured. The busbars are shorted at one end and the current is fed from the other through a variable-current injection set at a reduced voltage of 3-10 V, or enough to achieve the rated current. The arrangement saves on power requirement and consum-... 

This will be carried out under similar parameters of room condition and the type of test voltage wave to those for a switchgear assembly (Section 14.3.5). The current in each phase should be within 2% of the specified test value (rated current). 

Checking throughout the assembled switchgear or motor control centre for completeness and conformity to approved drawings, including name/data plates, types and ratings of equipment with corresponding identification labels both inside and on the front panel... 

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