BS EN 61952-2008 pdf download.Insulators for overhead lines Composite line post insulators for A.C. systems with a nominal voltage greater than 1 000 V Definitions, test methods and acceptance criteria.
10.2 Test specimens for IEC 62217
10.2.1 Tests on Interfaces and connections of end fittings
Three insulators assembled on the production line shall be tested. The insulation length (metal to metal spacing) shall be at least 15 times the core diameter. Both end fittings shall be the same as on standard production insulators. The end fittings shall be assembled so that the insulating part from the fitting to the closest shed shall be identical to that of the production line insulator. If spacers, joining rings or other features are used in the insulator design (notably for longer insulators), the samples for this test shall include any such devices in a typical position.
If the manufacturer only has facilities to produce insulators shorter than 15 times the core diameter, the design tests may be performed on insulators of those lengths available to him, but the results are only valid for up to the lengths tested.
10.2.2 Tracking and erosion test
If spacers, joining rings or other features are used in the Insulator design (notably for longer insulators), the samples for this test shall include any such devices in a typical position.
IEC 62217 specifies that the creepage distance of the sample shall be between 500 mm and 800 mm. If the inclusion of spacers or joints, as mentioned above, requires a longer creepage distance, the design tests may be performed on insulators of lengths as close to 800 mm as possible. If the manufacturer only has facilities to produce insulators with creepage shorter than 500 mm, the design tests may be performed on insulators of those lengths he has available, but the results are only valid for up to the tested lengths.
10.3.1 Thermal-mechanical pre-stressing
The three specimens shall be submitted to a mechanical load in two opposite directions and to temperature cycles as described in Figure 1. The 24 h temperature cycle shall be performed twice. Each 24 h temperature cycle has two temperature levels with a duration of at least 8 h. one at (+50 ± 5) °C, the other at (—35 ± 5) °C. The cold period shall be at a temperature at least 85 K below the value actually applied in the hot period. The pre-stressing can be conducted in air or any other suitable medium.
The load applied to the specimens shall correspond to the MDCL.
The load shall be applied to the insulator at the conductor position. The initial direction shall be appropriate for the end fittings, and approximately perpendicular to the axis of the insulator at the point of application
When the load is not applied at the normal application point, it shall be corrected to produce the same bending moment at the base of the insulator as the one exerted by the MDCL.
The direction of the cantilever load applied to the specimens shall be reversed once, generally at the cooling passage through ambient temperature as described in Figure 1.
NOTE The temperatures and loads in this pre-stressing are not intended to represent service conditions, they are designed to produce specific reproducible stresses in the interlaces on the insulator.
The cycles may be interrupted for the load direction reversal and for maintenance of the test equipment for a total duration of 2 h. The starting point after any interruption shall be the beginning of the interrupted cycle.
10.4 Assembled core load tests
10.4.1 Test for the verification of the maximum design cantilever load (MDCL)
10.4.1.1 Test specimens
Three insulators made on the production line using standard end fittings shall be selected. The overall length of the insulators shall be between 15 and 18 times the diameter of the core, unless the manufacturer does not have facilities to make such a length. In this case, the length of insulator shall be as near as possible to the prescribed length range.
It not already routine tested, the insulators shall be examined visually and their conformity with the drawing shall be checked. They shall then be subjected to the tensile load routine test according to 13.1.BS EN 61952-2008 pdf download.