Handbook of Electrical Installation Practice - BeKnowledge

80 Handbook of Electrical Installation Practice
plant to be identified by their height above Ordnance Datum (O.D.), e.g. ‘The 37.2
metre O.D. Switchboard’. While such systems of identification may be adequate for
the purposes of design and installation they are totally unsuited to the needs of
those who are required to operate the system in a safe manner. Discussion should
take place with the end user to decide on a logical scheme for identifying both the
substations, the switchboards and the individual switchgear and circuits.
With regard to the identification of substations, titles based on geographic or plant
references, e.g. ‘East Substation’, ‘Loading Bay Substation’, etc. are much more
likely to convey meaningful information than cryptic numbering systems. A switchboard
within a particular substation is probably best identified simply by appending
the voltage level at which it operates, e.g. ‘Loading Bay 400V Switchboard’. If
there is more than one switchboard operating at the same voltage at a particular
location it is usually quite easy to decide on a title based on, for example, its function.
When considering the identification of individual items of switchgear the simplest
and most sensible practice is to identify a switch or circuit-breaker by what its
‘circuit’ side is connected to, e.g. ‘Transformer T1’, ‘Administration Block’, ‘Pulp
Pump 3’, etc. Figure 3.12 illustrates a typical example.
It is undesirable to include what for this purpose is superfluous information on
the identity plate. A typical gross bad example would be ‘Circuit-Breaker feeding
1000kVA, 11kV/433V, Star-Delta, 4.75% Impedance Transformer Number 2’. In
order to ensure safe operation the title should appear, in full, in every entry on
switching schedules, permits-to-work and log books. If the identification is so protracted,
the people operating the equipment will be likely to abbreviate the title and
worse still each operator is likely to abbreviate it differently. The circuit-breaker in
the above example need only bear a plate with the inscription: ‘Transformer T2’. All
the other information should of course be available to the operator but it does not
Fig. 3.12 Identification of switchgear.