Handbook of Electrical Installation Practice - BeKnowledge

100 Handbook of Electrical Installation Practice
Fig. 5.1 Incoming supply assembly.
access to authorised personnel. The metering compartment houses the supply
authority’s equipment and can be sealed. The consumer’s main switch compartment
comprises the main isolator (lockable in the OFF position) and protective equipment.
Sufficient facilities are afforded for the maximum cable size likely to be
terminated.
If the metering equipment is housed within a substation or the authority’s own
enclosure, then the ISA provides the main site protection and control only. Figure
5.1 shows typical forms of ISA.
Incoming supply and distribution assembly (ISDA)
The ISDA comprises a compartment for the incoming feeder cable and metering
equipment; a main/isolation compartment for main control; and an outgoing compartment
housing sub-circuit control and protection devices.
Incoming feeder compartment
The incoming feeder compartment provides facilities for the incoming cable termination
and the Electricity Distributor’s cut-out. When called for, the facility must
exist for incorporation of current transformers (CTs) and metering equipment, as
well as potential fuses. All the equipment contained in this section belongs to the
supply authority and access is restricted to their authorised personnel.