Switchgear assemblies design

Design parameters and service conditions for a switchgear assembly 13/342... 

The fault ctirrents also develop electrodynamic foi ces, Fii, as in equation (28.4) due to the sub-transient d.c. component. These forces play an important role in the meehanical design of the interrupting device, the load-bearing and mounting structuies for the interrupter and the bus system, and the hardware used in a switchgear assembly. All such mechanical parts, supports and hardw-are should be adequate to withstand such forces when they arise, A procedure to arrive at the ideal size of the current-carrying components, mounting structure, type of supports and hardware cte, is discussed in detail in Example 28.12. 

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

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-... 

The subjects covered aim at providing methods to form specihcations and then design a switchgear assembly for all power distribution needs. It also provides coverage of draw-out asseinblies. Establishing the fault level of a system is described including the electrodynamic and electromagnetic forces that arise. 

A switchgear or a controlgear assembly will be designed to fulfil the following design parameters ... 

Below we discuss briefly the constructional requirements and general manufacturing practices for cubicle-type switchgear and controlgear assemblies, and the electrical and the mechanical design considerations to comply with the above design parameters and service conditions. 

The above are the more obvious constructional, design and safety features for a switchgear or a controlgear assembly. For more details and additional requirements refer to lEC 60439-1 for LT, lEC 60298 and lEC 60694 for FIT and ANSI-C-37/20C, common for LT and FIT switchgear and controlgear assemblies. 

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