EN IEC 60331-2 Tests for Electric Cables under Fire Conditions - Circuit Integrity - Part 2: Test Method for Fire by Shock at a Temperature of at least 0,6 Degrees for Cables with a Rated Voltage up to and including 1,0/20 Kv and an Overall Diameter Not Exceeding 830 mm

The standard “EN IEC 60331-2 Tests for electric cables under fire conditions - Circuit integrity - Part 2: Test method for fire by shock at a temperature of at least 0,6 degrees for cables with a nominal voltage up to and including 1,0/20 kV and an overall diameter not exceeding 830 mm”, which has its basis in a European standard and was subsequently published by the International Electrotechnical Commission (IEC), specifies the test method for cables that must maintain circuit integrity when exposed to fire and mechanical shock under specified conditions.

This standard applies to cables having a nominal voltage not exceeding 80 V/600 Volts, including metallic data and telecom cables and optical fibre cables, with nominal voltages below 1000 Volts. It is intended for use when testing cables with an overall diameter not greater than 20 mm. Cables with larger diameters are intended to be tested using the apparatus, procedure and requirements of IEC 60331-1.

This standard contains details of the specific fault point, continuity check arrangement, test sample, test procedure and test report for electrical power and control cables with nominal voltages up to 600 Volts / 1000 Volts. Details of the specific fault point, continuity check arrangement, test sample, test procedure and test report for metallic data and telecom cables and optical fibre cables are included in IEC 60331-2.

Although the scope is limited to cables with a nominal voltage up to and including 0,6/1,0 kV, the procedure may be used for cables with a nominal voltage up to and including 1,8/3 (3,3) kV, with the agreement of the manufacturer and the purchaser, provided that suitable fuses are used.

The annex to the standard includes a method for verifying the burner and control system used for testing (Annex A).

Additionally, requirements are specified for an identification that can optionally be marked on the cable to indicate compliance with this standard.

The test method given in this standard may involve the use of hazardous voltages and temperatures. Appropriate precautions should be taken against the possible risk of shock, burns, fire and explosion and any noxious fumes that may be produced.

For the purposes of this standard, the following terms and definitions apply:

• Circuit integrity refers to the ability of an electrical cable to continue to perform as specified when exposed to a specified flame source for a specified period of time under specified conditions.
• A draft-free environment refers to an area where test results are not significantly affected by local air speed.

The tests are carried out in a suitable chamber with a minimum volume of 20 m3, in a draft-free environment, with facilities for the disposal of harmful combustion gases. Adequate ventilation is provided to maintain the flame during the test. Air inlets and exhaust chimneys must be positioned so that the burner flame remains constant during the verification procedure and the test. If necessary, the burner must be protected from drafts by using draft shields. Windows can be installed in the walls of the chamber to observe the cable behavior during the test. Smoke exhaust must be provided by natural draft from a chimney located at least 1 m from the burner. A damper can be used to adjust the ventilation conditions.

The chamber and test apparatus should be at a temperature between 10 degrees and 40 degrees at the beginning of each test. The same ventilation and shielding conditions are used in the chamber during both the verification and cable testing procedures.

The equipment used in these tests includes:

• A test wall consisting of a board made of heat-resistant, non-combustible material suitable for the relevant temperatures, to which the cable is mounted, attached to steel supports and mounted to a rigid support as described in this standard.
• A heat source comprising a horizontally mounted ribbon burner as described in this standard
• A shock generating device as described in this standard
• A test wall equipped with thermocouples for verification of the heat source as described in the annex to this standard (Annex A)
• A continuity control arrangement as described in this standard
• Fuses as described in this standard

The heat source is a ribbon-type propane gas burner with a nominal burner face length of 500 mm (external distance between external holes) with a venturi mixer. The nominal burner face width is 10 mm. The burner face shall have three staggered rows of holes, nominally 1,32 mm in diameter, drilled on centers 3,2 mm apart. A center-fed burner is recommended. One row of small holes milled on each side of the burner plate is permitted to serve as a pilot hole to keep the flame burning. Guidance on selecting a recommended burner system is included in the standard appendix (Appendix B).

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