Type test of Overhead transmission lines Suspension and support clamps

Type test

General

Unless otherwise agreed upon the type test shall be in accordance with Clauses 6.2-6.10 on three test samples. The test shall be performed in such a way that the method and equipment do not affect the result.

Dimensions

This test intends to check that the clamp and the counterweight stirrup fulfil the re- quirements in accordance with Clause 5.3 and that they are also in accordance with the manufacturers drawing regarding dimensions.

Thickness of zinc coating

This test shall be performed in accordance with SS-ISO 2178. Each sample shall be subject to, depending on size, 3 to 10 measurements. The points of measurement shall be evenly and randomly distributed over the entire sample surface.

The minimum and average layer thickness requirements in accordance with Clause 5.1.5 shall be fulfilled.

Hardness

Hardness tests on aluminium shall be in accordance with SS-EN ISO 6506-1. Measured hardness value shall conform to the requirements of Clause 5.2.1.

Clamping force

The clamp force shall be measured with one or two load cells located in the conductor supporting groove during a sequence of three installations. The bolts shall be tight- ened with a torque of 60 Nm at suspension clams for phase conductors and with 37 Nm for clamps for earth wires.

The measured clamp force shall during all three installations exceed the requirements of Clause 5.4.6.

Threads

Securing bolts shall be installed in threads to a length equivalent to the minimum length as specified on the workshop drawings. A tensile load of 67 kN shall be applied to the bolt.

Rupture shall not have occurred in the threads and the bolt shall be easily turned by hand.

Permanent deformation

Suspension and support clamp

The clamp shall be installed on conductors with the required strength and same diam- eter as the conductor for which the clamp is designed. The securing bolts shall be tightened with a torque of 60 Nm at clamps for phase conductors respectively with 37 Nm at clamps for earth wires.

The clamp shall be installed in a tensile testing machine in such a way that the conduc- tor turning angle α, conforms to Table 1 during the test. See Figure 4. The load shall be increased in steps. The first step shall be 10 % of the specified deformation load. The clamp shall then be unloaded and measurement of the permanent deformation, if any, carried out and recorded. The second step shall be 20 % of the specified defor- mation load. The clamp shall then be unloaded and measurement of the permanent deformation, if any, carried out and recorded. This procedure shall be  continued until 100 % of the specified deformation load is attained.

The load at which permanent deformation is shown shall exceed the load given in Ta-ble 1 in accordance with Clauses 5.4.1 and 5.4.2.

 Counterweight stirrup
The counterweight stirrup shall be attached to a suspension clamp, or a dummy, in accordance with the installation instructions.

The counterweight stirrup is then to be installed in a tensile testing machine. See Fig-ure 5. The load shall be increased in steps. The first step shall be 10 % of the specified deformation load. The stirrup shall then be unloaded and measurement of the perma- nent deformation, if any, carried out and recorded. The second step shall be 20 % of the specified deformation load. The stirrup shall then be unloaded and measurement of the permanent deformation, if any, carried out and recorded. This procedure shall be continued until 100 % of the specified deformation load is attained.

The load at which permanent deformation is shown shall exceed the load given in Ta-ble 1 in accordance with Clause 5.4.7.

Breaking load

After the clamp has been tested in accordance with Clause 6.7.1 the load shall be in-creased until failure occurs in the clamp.

The attained breaking load shall exceed the load given in Table 1 in accordance with Clauses 5.4.1, 5.4.2 and 5.4.3.

Corona

The intention of this test is to verify the corona extinction voltage in a fully assembled insulator set.

The test shall be performed in accordance with SvK TR 05-10E Clause 6.5.

Fault current

The intention of this test is to verify that the requirements in Clause 5.5.1 are fulfilled. Test performed on other product consisting of the same materials and having equal

contact surfaces is considered to constitute type test for clamps in accordance with this guidelines.