From 3KV to 36KV switchgear system; it is categorized like medium voltage switchgear or MV switchgear. These switchgears are of various kinds. They might possibly be of outdoor type with no metal enclosure, metal enclosed indoor type, metal enclosed outdoor type, and so on. The interruption medium of this switchgear may be SF6, vacuum and oil. The main obligation and necessity of MV power network is to interrupt the current in faulty condition irrespective of what type of CB is used in the MV switchgear system. It might possibly be capable of functioning in also other conditions. Medium Voltage Switchgear ought to be highly capable of:
- Short circuit current disruption.
- Usual ON/OFF switching operation.
- Switching of capacitive and inductive currents.
- Various special applications.
All the above mentioned function ought to be carried with high degree of consistency and security.
The main focus of circuit breaker design is that every circuit breaker ought to be capable of interrupting short circuit current with high degree of consistency and protection. The number of faulty tripping occurred in total life period of circuit breaker usually depends on the location of the system, value of environment state and system. If the tripping number is high, the outstanding alternative is vacuum circuit breaker as it may not require any maintenance till 100 faulty tripping with short circuit current till 25KA. Whilst other circuit requires maintenance after 15 to 20 faulty tripping with same short circuit CB current.
The joint substations in rural areas are more often than not of outdoor type, and the best part of them is unattended sort. Hence for this type of applications maintenance free outdoor form, medium voltage switchgear is most suitable. Porcelain clad vacuum circuit breaker meets this obligation against the customary indoor kiosks.