CONDUCTOR APPLICATIONS

INTRODUCTION

Conductors are an essential component of a Lightning Protection System.

They form part of the:

  • Air Termination Network
    – arresting the lightning strike
  • Down Conductor System
    – taking the lightning discharge to ground
  • Earth Termination/Network
    – safely dissipating the lightning discharge into the ground

Conductors are also an integral and important component of an earthing system, whether this be for a power station, sub-station, cell site, solar PV array etc.

Conductors provide a low impedance path and they must be:

  • Correctly sized for fault current
  • Sufficiently robust to resist mechanical damage
  • Able to resist the effects of corrosion

Our comprehensive range of conductors enables the Lightning Protection Designer greater freedom to: conceal conductors, aesthetically blend conductors into the building facade, as well as offering lower cost alternatives – Strikeband and aluminium etc.

Our Insulated Lightning Conductor also allows the designer to resolve spacing problems when there is insufficient room to install a “conventional” conductor whilst maintaining the required separation distance between it and the electrically conductive parts of the structure that require protection. The Kingsmill Insulated Lightning Conductor effectively simulates an equivalent separation distance of ≤0.75m in air and ≤1.5m in solid material.

Guide to Conductor Selection

Conductors are the most important part of a Lightning Protection and Earthing system. They:

  • Intercept the lightning current
  • Carry and safely dissipate the lightning current/earth fault to earth

It is important, therefore, that they:

  • Are corrosion resistant
  • Carry the current required
  • Are mechanically robust
  • Provide a low resistivity path to earth

From BS:EN 62305 . . .

The most common cross-section areas for above ground lightning protection conductors are 8mm dia (50mm2 – BS:EN 62305 min) and 25 x 3mm (75mm2) rectangular section.

Selecting the Best Conductor

Selecting the best conductor for the application

When choosing the material for “above ground” Lightning Conductors, it is important to take into account the avoidance of any bimetallic corrosion. For example, one should avoid the installation of copper conductors over aluminium or steel cladding.

  • Galvanic corrosion – happens when there is a potential difference between dissimilar metals
  • When the materials are in contact in the presence of an electrolyte, corrosion occurs. One metal becomes the anode, the other the cathode. The anode will tend to go into solution and therefore corrode. The electrolyte can be water with impurities from the air.
  • In the instance of water run-off from copper – the water carries fine copper corrosion particles which, when they drip on to aluminium or zinc, may result in corrosion. The direct contact of the  dissimilar metals is not required for corrosion to occur in such a case.

Whilst there are cautions with respect to the use of aluminium, these can generally be overcome with the use of PVC covered aluminium conductor, in an above ground Lightning Conductor setting.

CONDUCTOR SECTION OPTIONS

STRIKEBAND and aluminium conductors combine the benefits to the installer of light weight and easy installation. Such materials exhibit little “spring back” and so are easier to dress to the contours and shapes of the structure.

strikeband bimetallic conductor

Solid circular section conductors are the easiest to install since they can be bent through any plane (360º) whereas tape can only be bent in two directions.

360º overcomes problems that are presented by complex geometry buildings.

strikeband bimetallic conductor
strikeband bimetallic conductor

PVC COVERED CONDUCTOR

PVC covering is often used as a decorative cover when blending in external conductors to building aesthetics. Thought must be given however, to using such conductors in areas of high UV, due to colour bleaching and the life of modern UV stabilisation compounds.

Kingsmill copper tape conductor pvc covered

CONDUCTOR COLOUR CHART

The decision to be made on the colour of PVC covered conductor is governed by the aesthetics of the building to be protected.

To reduce the impact of an external system, Kingsmill offer a range of colours designed to match the colours of common building materials.

OTHER COLOURS ARE AVAILABLE UPON REQUEST- PLEASE SPEAK TO A MEMBER OF THE SALES OFFICE.

COLOURSTANDARDSCOLOUR
Black18B29*
GreenBS 6746C
Grey00A07*
Stone08B23*
White10B15*
Brown06C39*
Green/YellowN/A

*PVC colours to BS 5252, green to BS 6746C

CONDUCTOR SIZING

Earth conductors are sized according to the maximum fault that they are to carry. When carrying out this calculation, it is important to take into account the type of connectors used – exothermic joints will take 100% of the fault current, whereas bolted, braided and crimp connections do not (a chain is only as good as its weakest link).

COPPER CONDUCTOR RATINGS: FAULT CURRENT

The following conductor ratings are based upon the recommendations of BS 7430 with an initial conductor temperature of 30ºC and a maximum temperature of 250ºC.

CONDUCTOR SIZE
CSA (mm²)
kA for 1 sec
kA for 3 sec
12.5 x 1.5
18.75
3.3
1.9
12.5 x 3
37.5
6.6
3.8
20 x 1.5
30
5.3
3.0
20 x 3
60
10.6
6.1
25 x 1.5
37.5
6.6
3.8
25 x 3
75
13.2
7.6
25 x 4
100
17.6
10.2
25 x 6
150
26.4
15.2
30 x 2
60
10.6
6.1
30 x 3
90
15.8
9.1
30 x 4
120
21.1
12.2
30 x 5
150
26.4
15.2
31 x 3
93
16.4
9.5
31 x 6
186
32.7
18.9
38 x 3
114
20.1
11.6
38 x 5
190
33.4
19.3
38 x 6
228
40.1
23.2
40 x 3
120
21.1
12.2
40 x 4
160
28.2
16.3
40 x 5
200
35.2
20.3
40 x 6
240
42.2
24.4
50 x 3
150
26.4
15.2
50 x 4
200
35.2
20.3
50 x 5
250
44.0
25.4
50 x 6
300
52.8
30.5