For a default voltage of 25 V and a default current of 30 mA, this rod must be of a minimum length of: see table below
Nature of ground
Length of
rod in
metres
Thick arable land,
moist compact ballast
1
Lean arable land,
Gravel, coarse ballast
1
Bare stony soils, dry sand,
impermeable rock
3.6
To obtain an equivalent length, you can use several earthing rods
connected in parallel and set apart by at least their length.
Example: 4 interconnected 1 metre rods separated by 1 metre.
Note: For the United States (National Electrical Code reference NFPA-70).
The generating set must be earthed. To do this, use a copper wire with a minimum cross-section of 13.3 mm² (or AWG 6, at most)
connected to the generating set earth socket and a galvanised steel earthing rod fully embedded into the ground vertically.
This earthing rod embedded fully in the ground must have a minimum length of 2.5 m.
3.5.2 Earthing system principle
The Earthing system, or SLT (formerly Neutral system) of the electrical facility defines the situation of the generating set neutral in
relation to earth and the grounds of the electrical facility at the user end.
The purpose of the earthing systems is to protect personnel and equipment by managing risks posed by insulation defects. For safety
reasons, any live conducting part of a facility must be insulated from the earth. This insulation may be achieved by distance, or by using
insulating materials. But with time, insulation may deteriorate (due to vibrations, mechanical impacts, dust, etc.), and therefore generate
an earth with dangerous potential. This defect poses risks for personnel and property, but also continuity of service.
Earthing systems are codified by two letters that define the connections:
 The first letter defines the neutral connection:
I Insulated or earthed via an impedance device
T Connected to earth
 The second letter defines the grounding situation of the electrical facility:
T Connected to earth
N Connected to neutral
E.g.: IT = Isolated Neutral + Ground earthed
Speed
Number of
conductors
Detection Note
TT 4 poles Measurement of residual current Triggering of 1
s
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