This part of GB/T 16935 specifies the requirements for clearances, creepage distances and solid insulation for equipment based upon their performance criteria. lt includes methods of electric testing with respect to insulation coordination.
The minimum clearances specified in this part do not apply where ionized gases occur. Special requirements for such situations may be specified at the discretion of the relevant technical committee.
This part deals with basic, supplementary and reinforced insulation subjected to high-frequency voltage stress within low-voltage equipment. The dimensioning values directly apply for basic insulation; for reinforced insulation additional requirements apply according to IEC 60664-1. It is applicable for the dimensioning of clearances, creepage distances and solid insulation stressed by any type of periodic voltages with a fundamental frequency above 30 kHz and up to 10 MHz.
This part can only be used together with IEC 60664-1 or with IEC 60664-5. By using IEC 60664-1, IEC 60664-5 together with this part the frequency limit of IEC 60664-1 and IEC 60664-5 is extended to frequencies higher than 30 kHz.
This part also applies to IEC 60664-3 for frequencies greater than 30 kHz and protection of type 1. For type 2 protection this question is under consideration.
Notes:
1 Dimensioning values for frequencies above 10 MHz are under consideration.
2 This part does not consider the high-frequency emission to the mains. In normal use of equipment, it is assumed that the interference of high-frequency voltages emitted to the mains is negligible with respect to insulation stress. Therefore it is not necessary to take it into account.
It applies to equipment for use up to 2,000 m above sea level having a rated voltage up to a.c. 1,000 V.
This part does not deal with distances
——through liquid insulation,
——through gases other than air,
——through compressed air.
Notes:
3 Higher voltages may exist in internal circuits of the equipment.
4 Requirements for altitudes exceeding 2,000 m can be derived from Table A.2 of Annex A of IEC 60664-1.
The object of this part is to guide technical committees responsible for different equipment in order to rationalise their requirements so that insulation coordination is achieved when specifying clearances in air, creepage distances and solid insulation for equipment.
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 60112: 2003 Method for Determining the Comparative and the Proof Tracking Indices of Solid Insulating Materials under Moist Conditions
IEC 60664-1: 1992 Insulation Coordination for Equipment within Low-voltage Systems - Part 1: Principles, Requirements and Tests) (Amendment 1 (2000)); (Amendment 2 (2002))
IEC 60664-5: 2003 Insulation Coordination for Equipment within Low-voltage Systems - Part 5: A Comprehensive Method for Determining Clearances and Creepage Distances Equal to or Less than 2 mm
IEC Guide 104: 1997 The Preparation of Safety Publications and the Use of Basic Safety Publications and Group Safety Publications
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in IEC 60664-1, as well as the following terms and definitions, apply.
3.1
approximately homogeneous field
for frequencies exceeding 30 kHz, the field is considered to be approximately homogeneous when the radius of curvature of the conductive parts is equal or greater than 20 % of the clearance
3.2
inhomogeneous field
for frequencies exceeding 30 kHz the field is considered to be inhomogeneous when the radius of curvature of the conductive parts is less than 20 % of the clearance
