Requirements and Testing of LPS Components

Introduction:

IEC 62561 series of standards deals with the requirements and testing requirements for different components used for the installation of a lightning protection system (LPS). IEC 62561-2 specifies the requirements and tests for the conductors that are used for air termination, down conductor and earthing other than the natural components.

Requirements of LPS components:

While selecting materials for Lightning protection system applications, the following factors should be considered.

• The material, configuration and cross-sectional area of the conductors and rods should be as per the standard specifications.
• Their mechanical and elect cal characteristics of the materials should be considered. 
• Coated conductors have good corrosion resistance property and the proper adherence of the coating should be ensured.

Earth Rods:

• Earth rods shall be mechanically robust and there should not be any cracking on the material during installation.
• The threads on the coated rods should also be coated. 
• For copper coated rods, it should be ensured that no copper is removed from the steel.

Earth Rod coupler:

The earth rod coupler can be used to extend the length of the earth rods. The material of coupler shall be compatible with that of the earth rod. It should be able to withstand the driving forces generated during installation. It should have good corrosion resistance property. No threads on the earth rod should be exposed when using an external type threaded coupler. In case of an internal type threaded couplers, the mating faces of the earth rods should have proper contact with each other after assembly.

Testing:

Tests specified in IEC 62561-2 standard are type tests. Air termination rods, down conductors and earth conductors shall be subjected to the following tests to confirm that the components are suitable for lightning protection system applications.

Test for thickness coating on conductors:

For performing the coating thickness measurement test, a specimen of 500mm length can be used. The copper or zinc coating over steel core shall be tested using a Magnetic method instrument as per ISO 2178. Zinc coating shall also be measured in accordance with ISO 1460 or ISO 1461.

Test Positions:

The testing is performed at three different positions of the sample and the positions are as follows.

• 50mm from top
• 50mm from bottom
• Mid-point

For rods, the measurement should be made around the circumference of the specimen at 3 points of approximately 120° separation at each position.

For flat specimens, the measurement should be made on both sides of the flat in the middle of the width at each position.

IEC 62561 specifies that there is no requirement to measure the thickness of tin plating on copper where it is applied for aesthetic reasons only.

Acceptance Criteria:

• The coating thickness shall be not less than the values specified in the standard.
• Zinc galvanizing coating shall be smooth, continuous and free from flux strains.
• Minimum weight of zinc should be 350g/m-for solid round specimen and 500g/mfor solid tape specimen.

Bend and Adhesion test:

The coated conductors of 500mm long shall be bent to an angle of 90 degrees. The bending radius should be equal to

• 5 times the diameter for a round conductor. 
• 5 times the thickness for ape conductor.

Acceptance Criteria:

After the test, there should not be any sharp edges, cracks or peeling of coating without magnification.

Environmental test:

The electrical resistance over a length of 100mm shall be measured prior to the environmental tests. After measuring the resistance values, the specimens shall be subjected to below tests.

• Salt mist treatment
• Humid sulphurous atmosphere treatment

Acceptance criteria:

• The difference in the electrical resistance value measured before & after the tests shall not be more than 50%
• There should not be any signs of corrosion on base metal of the specimens without magnification.

Electrical Resistivity Test:

A sample conductor of 1.2m length is taken and the resistance is measured over a Im distance using micro-ohmmeter. The measure value is corrected to a temperature of 20°C.

From the measured resistance value, the resistivity of che material can be calculated by using the below formula,

p= (R*a)/l

Where.

R - Resistance over 1m length (in Ω)

a - Cross sectional area (in m²)

l - Unit length (in m)

Acceptance Criteria:

The specimens are deemed to have passed the test, if they comply with the values specifies in the standard.