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klik.system | Specification guide to prefabricated wiring systems
16
Protective conductor arrangement for high
protective conductor currents
Regulation 543.7.1.103 stipulates that, when the cumulative
protective conductor current of the circuit is likely to exceed
10 mA, it shall have a high integrity protective connection
complying with one or more of the five listed options.
Therefore, the designer should evaluate the likely
protective conductor currents in relevant parts of the
prefabricated wiring system, including those supplying
luminaires. This is because it is recognized, that some
luminaires can produce currents in the protective conductor
e.g. high-frequency fluorescent luminaires. When a significant
number of luminaires are supplied from a common system,
the protective conductor current may exceed 10 mA.
Wherever possible, protective conductor current should be
determined by consulting information provided by the
luminaire manufacturer.
A protective conductor current not exceeding 10 mA may be
difficult to avoid in particular sections of a prefabricated
wiring system e.g. the home run cable and link lead to a
Lighting Distribution Unit (LDU) therefore, a high integrity
protective connection would be required. However, the
system arrangement after the home run / LDU link lead could
be configured using LDUs supplying a suitable number of
luminaires, thus avoiding cumulative protective conductor
currents above 10 mA. Table 3 provides examples of
luminaire leakage current values.
Example
Luminaire type
Maximum
protective
conductor
current
(mA, r.m.s.)
BS EN 60598-1:2008 Class I intended for
permanent
connection. Supply
current ≤ 7 A.
3.5
Test result for specific
luminaire
Fluorescent with HF
ballast
0.2
Manufacturers data
Per fluorescent HF
ballast
0.5
Manufacturers data
LED driver: output
power 150 W
0.7
Table 3 - Examples of leakage current values
for conventional luminaires
“ A high integrity protective connection
may be required ”.