There are 2 types of defined partitioning class,Class PM & Class PI:
Selection of partition class does not necessarily ensure personnel protection in the case of an internal arc in an adjacent compartment; refer to IEC.
- Partition class PM(partitions metallic=partitions & shutters made of metal):
Medium voltage metal enclosed switchgear providing continuous metallic partitions and/or shutters(if applicable),intended to be earthed, between opened accessible compartments and medium voltage live parts
- Partition class PI(partitions nonmetallic=partitions & shutters made of insulating material):
Medium voltage metal-enclosed switchgear having one or more non-metallic partitions or shutters between opened accessible compartments and medium voltage live parts.
In class PM opened medium voltage compartments are surrounded by metallic partitions and/or shutters that are intended to be earthed. A shutter may or may not be in the opened compartment itself, provided that segregation(is achieved between components in the opened compartment and components in the adjacent compartments)
In pic shown an example PM class AIS switchgear from Siemens SEMOPRIME type