IEC 60099-8-2017 pdf free download.Surge arresters – Part 8: Metal-oxide surge arresters with external series gap (EGL A) for overhead transmission and distribution lines of a.c. systems above 1 kV.
This part of IEC 60099 covers metal-oxide surge arresters with external series gap (externally gapped line arresters (EGLA)) that are applied on overhead transmission and distribution lines, only to protect insulator assemblies from lightning-caused flashovers.
This document defines surge arresters to protect the insulator assembly from lightning-caused over-voltages only. Therefore, and since metal-oxide resistors are not permanently connected to the line, the following items are not considered for this document:
• switching impulse spark-over voltage:
• residual voltage at steep current and switching current impulse;
• thermal stability;
• long-duration current impulse withstand duty;
• power-frequency voltage versus time characteristics of an arrester;
• disconnector test:
• aging duties by power-frequency voltage.
Considering the particular design concept and the special application on overhead transmission and distribution lines, some unique requirements and tests are introduced, such as the verification test for coordination between insulator withstand and EGLA protective level, the follow current interrupting test, mechanical load tests. etc.
Designs with the EGLAs external series gap installed in parallel to an insulator are not covered by this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements 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.
lEG 60060-1:2010. High-voltage test techniques — Part 1: General definitions and lest requirements
IEC 60060-2:2010, High-voltage lest techniques — Part 2: Measuring systems
IEC 60068-2-11:1981. Basic environmental testing procedures — Part 2-11: Tests — Test Ka: Salt mist
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org!
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 externally gapped line arrester EGLA arrester designed for installation on overhead lines to protect an insulator assembly from lightning-caused fast-front over-voltages only
Note 1 to entry: This is accomplished by raising the spark-over level of the external series gap to a level that Isolates the arrester tram power-frequency over-voltages and from the worst case slow-front over-voltages due to switching and fault events expected on the line to which it is applied.
3.2 series varistor unit svu non-linear metal-oxide resistor part, contained in a housing, which must be connected with an external series gap to construct the complete arrester
Note 1 to entry: The series varistor unit may include several units.
3.3 sectIon of an EGLA complete, suitably assembled part of a complete EGLA necessary to represent the behaviour of a complete EGLA with respect to a particular test.IEC 60099-8 pdf free download.