CAN CSA C156.3-M86:2018 pdf download.Test Methods for Station Post Insulators
2.1 Definitions
The following definitions apply in this Standard:
Batch (lot) means an identifiable collection of items, or quantity of material of a single type,grade, class, size, or composition produced in the same plant under essentially the same conditions at essentially the same time.
Creepage distance (leakage) (of an insulator) is the shortest distance or the sum of the shortest distances along the contours of the external surfaces of the insulating parts of the insulator, between those parts that normally have the operating voltage between them. A distance measured over the surface of cement or other conducting jointing material shall not be considered as forming part of creepage distance. If high-resistance coatings are applied to parts of the insulator, such coatings shall be considered effective creepage surfaces and the distances over them shall be included in the creepage distance.
Dry-arcing distance (of an insulator) is the shortest distance through the surrounding medium between terminal electrodes, or the sum of the distances between intermediate electrodes, whichever is shorter, with the insulator mounted for the dry flashover test.
Fast front (lightning) impulse withstand voltage (dry) is the peak value of lightning impulse voltage that the post insulator or post insulator unit withstands dry under the prescribed conditions of test.
Fast front (lightning) surge is a phase-to-phase or a phase-to-ground voltage that has a virtual front time of 1.2 μS and a time-to-half-value of 50 μS as defined in IEC Standard 60.
Flashover means a disruptive discharge (see IEC Standard 60) external to the post insulator or post insulator unit, connecting those parts that normally have the operating voltage between them.
Note: The term“flashover" used in this Standard includes flashover across the insulator surface as well as disruptive discharges by sparkover through air adjacent to the insulator. Disruptive discharges should only occur occasionally elsewhere (for instance to other structures or to earth), in which case they should not be taken into account for the purposes of this Standard.
3.7 Residual Deflection Test
Residual deflection tests shall be made with the test specimen adequately secured to the testing machine so that there shall be no relative movement between the machine mounting face for the insulator and the bottom hardware of the insulator. A dial indicator shall be positioned in contact with the topmost shed of the insulator, as shown in Figure 2. A cantilever load equal to 20% of the rated value shall be applied first in one direction and then released, after which the indicated dial reading shall be recorded. Without resetting the indicator, a 20% of rated cantilever load is then to be applied in the opposite direction and then released again recording the indicated dial reading. The residual deflection is the sum of the two indicated dial readings. A typical deflection curve demonstrating the residual deflection measurement is given in Figure 3.CAN CSA C156.3-M86 pdf download.