IEC 61211-2004 pdf – Insulators of ceramic material or glass for overhead lines with a nominal voltage greater than 1 000 V – Impulse puncture testing in air

IEC 61211-2004 pdf – Insulators of ceramic material or glass for overhead lines with a nominal voltage greater than 1 000 V – Impulse puncture testing in air.
1 Scope and object This International Standard deals with impulse puncture testing in air of ceramic and glass insulator units of class B (see IEC 60383-1): cap and pin, pin type (including pin-post type) and class B long rod insulators. This standard may be applied also in tests on Class B insulators of other materials (e.g. polymers and composites). However, it may be useful to consider the possible need to adjust the test procedure accordingly. This standard is published with the object of specifying a standard procedure for impulse voltage puncture tests on insulators in air. Both type and sample test procedures are given. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60050-471, International Electrotechnical Vocabulary – Chapter 471: Insulators IEC 60060-1, High voltage test techniques – Part 1: General definitions and test requirements IEC 60060-2, High voltage test techniques – Part 2: Measuring systems IEC 60305, Insulators for overhead lines with a nominal voltage above 1 000 V – Ceramic or glass insulator units for a.c. systems – Characteristics of insulator units of the cap and pin type IEC 60383-1, Insulators for overhead lines with a nominal voltage above 1 000 V – Ceramic or glass insulator units for a.c. systems – Definitions, test methods and acceptance criteria IEC 61083-1, Instruments and software used for measurement in high-voltage impulse tests – Part 1: Requirements for instruments 3 Terms and definitions For the purposes of this document, the definitions of IEC 60383-1 or IEC 60050(471) shall apply unless otherwise specified, as well as the following definitions.
3.1 impulse puncture withstand voltage specified peak voltage that the insulator withstands when applied according to this standard 3.2 test voltage actual peak voltage value determined by flashover of the applied impulse voltage 4 Abbreviations D divider G generator k coverage factor (according to IEC 60060-2) U 50 50 % flashover voltage at standard lightning impulse p.u. per unit relation of the test voltage and U 50 . 5 Impulse voltage puncture test on insulators in air 5.1 General requirements for the test Unless otherwise specified, IEC 60060-1, IEC 60060-2 and 60383-1 are applicable. The test specimen shall be clean and dry, and in thermal equilibrium with the surrounding environment before starting the test. 5.2 Mounting arrangements 5.2.1 General The mounting arrangement depends on the type of the insulator unit and on its possible integral metallic parts. The ground return conductor between the insulator and the divider shall be a plate. It is advisable to use a plate also in other parts of the ground return circuit. The test voltage shall be applied between the generator connector and ground return. 5.2.2 Cap and pin insulators Cap and pin insulators (Figure 1) shall be mounted with the cap towards an earthed plate whose smallest dimension is at least twice the diameter of the insulator to be tested. The distance from this plate to the insulator dielectric shall be as small as possible but sufficient to avoid direct flashover to the plate. On the pin side, a ball socket having approximately the same dimensions as the actual cap of the insulator shall be mounted to avoid electrical over- stress in the critical area at the level of the cement around the pin. The divider (D) and generator (G) shall be connected to this ball socket. A similar method shall be used for clevis and tongue type fittings. 5.2.3 Long rod insulators Long rod insulators (Figure 1) shall be mounted accordingly on an earthed plate.
a) For pin insulators with the insulating component in service being supported without contact with the supporting structure: The test specimen shall be mounted on a metal pin approximately 25 mm in diameter of such length that the shortest dry-arcing distance from the upper electrode and connected metallic parts to the supporting cross arm shall be 25 % to 50 % greater than the similar distance to the pin. The pin shall be coaxial with the test specimen. If the insulator has an integral pin, this shall be used. b) For pin insulators with the insulating component in service being in contact with the supporting structure (pin-post): The test specimen shall be attached directly to the supporting cross arm. For the top connection of pin insulators without a metallic clamp, a circular metallic spring 18 mm in diameter shall be placed in the side groove. A suitable plate with smooth connections in the side groove shall be mounted over the top or in the top groove if any. This plate shall be provided with two connectors, one for the generator circuit and the other for the divider. If the pin insulator is provided with a means of clamping, the connectors for the generator circuit and for the divider shall be placed in a clamp.