Switchgear assemblies application

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

The bus system of a switchgear assembly, its interconnecting links and wires are the protected type components, whereas an interrupter (breaker, switch or a fuse) may be a protecting or protected type, depending upon their application and location in the circuit. A contactor and an OCR are therefore protected devices in the same context, for they provide no short-time protection. A protecting device may become protected when it is also provided with a back-up protection. 

This test is applicable to all outdoor metal-enclosed switchgear and controlgear assemblies, as in lEC 60298, lEC 60694 and ANSI C-37/20C. The enclosure to be tested should be complete in all respects including its mounts, bushings (for HT switchgear assemblies, 1 kV and above) and wiring. One or more vertical units can be tested simultaneously as may be convenient, but not more than 3 m panel width can be tested at a time. For a multiple unit switchboard, however, at least two vertical units should be tested together to check the joints between the units. 

This may be 50 or 60 Hz as the system may require. The permissible variation may be eonsideied as 2% for measuring as well as protection VTs. These limits are based on the recommended variations applicable for a switchgear assembly (lEC 60429-1) or an electric motor (Section 1.6.2),... 

The procedure will be the same as that discussed for switchgear assemblies (Section 14.3.3). The test voltage may be applied for one minute as shown in Tables 32.1 (A) or (B) for series I and Table 32.2 for series II voltage systems. Any disruptive discharge or insulation breakdown during the application of high voltage will be considered to be dielectric failure. 

Instrument transformers (CTs, class PS, CT, VTs and CVTs etc.) form important components of a switchgear assembly for measurement and protection. They are covered for their specifications, selection and application. 

Depending upon their application, a switchgear or a controlgear assembly can be one of the following types ... 

No derating is applicable in case of insulated switchgear (GI.S) assemblies. 

Uses. The major applications of phenol are phenolic resins, Bisphenol A, and caprolactam. The reaction of phenol with formaldehyde gives liquid phenolic resins (used extensively as the adhesive in plywood) and solid resins (used as engineering plastics in electrical applications). In powder form, the phenolic resin can be molded easily and are completely nonconductive. These phenolic resins or plastics can be found in panel boards, switchgears, and telephone assemblies. The agitator in your washing machine is probably a phenolic resin. 

Switchgears can serve as main secondary service equipment, as main primary service equipment, and as load center equipment when located near load concentrations. The assembly and its devices provide for the control and distribution of electricity to utilization or subdistribution equipment. Most switchgear manufactured since 1955 has been metal-enclosed, dead-front, free-standing type, with its circuit protective devices enclosed each in its own compartment. For certain types of load applications, the protective devices are group-mounted in separate cubicles instead of individual compartments. 

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