- CBs have a switching capability for switching on and off any kind of current up to the rated current, that is, load current and short circuit currents.
- CBs installed in overhead systems should have the capability of operating sequences for successful and unsuccessful auto reclosing.
- LBS are capable of switching load currents under normal operating conditions, but have no capability for switching short – circuit currents.
- DSs can be operated only under no load conditions. Currents of busbars without load and no – load currents of transformers with low rating can be switched on and off as well. Interlocking with the CB is necessary.
- ES s are used for earthing of equipment. The combination of ES with DS is common.
- Fuse are installed in LV and MV systems only. They interrupt currents of any kind by the melting of a specially designed conductor and must thereafter be replaced. Combination of fuses with DSs can be found especially in LV systems.
Pic show a typical feeder arrangement for HV switchgear: (a)Overhead line feeder with double busbar; (b)transformer feeder with double busbar. 1:Busbar DS; 2:CB; 3:feeder DS; 4:ES, 5:CT; 6:VT 7:CVT; 8:blocking reactor.