GB/T 16935.1-2023 Insulation coordination for equipment within low-voltage supply systems - Part 1: Principles, requirements and tests
1 Scope
This document deals with insulation coordination for equipment having a rated voltage up to AC 1 000 V or DC 1 500 V connected to low-voltage supply systems.
This document applies to frequencies up to 30 kHz.
Note 1: Requirements for insulation coordination for equipment within low-voltage supply systems with rated frequencies above 30 kHz are given in IEC 60664-4.
Note 2: Higher voltages can exist in internal circuits of the equipment.
This document applies to equipment for use up to 2 000 m above sea level and provides guidance for use at higher altitudes (See 5.2.3.4).
This document provides requirements for technical committees to determine clearances, creepage distances and criteria for solid insulation. It includes methods of electrical testing with respect to insulation coordination.
The minimum clearances specified in this document do not apply where ionized gases are present. Special requirements for such situations can be specified at the discretion of the relevant technical committee.
This document does not deal with distances:
——through liquid insulation;
——through gases other than air;
——through compressed air.
This basic safety publication focusing on safety essential requirements is primarily intended for use by technical committees in the preparation of standards in accordance with the principles laid down in IEC Guide 104 and ISO/EC Guide 51.
One of the responsibilities of a technical committee is, wherever applicable, to make use of basic safety publications in the preparation of its publications.
However, in case of missing specified values for clearances, creepage distances and requirements for solid insulation in the relevant product standards, or even missing standards, this document applies.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions 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.
GB/T 2423.22-2012 Environmental testing - Part 2: Test methods - Test N: Change of temperature (IEC 60068-2-14: 2009, IDT)
IEC 60068-2-2 Environmental testing - Part 2-2: Tests - Test B: Dry heat
Note: GB/T 2423.2-2008 Environmental testing for electric and electronic products - Part 2: Test methods - Test B: Dry heat (IEC 60068-2-2: 2007, IDT)
IEC 60068-2-78 Environmental testing - Part 2-78: Tests-Test Cab: Damp heat, steady state
Note: GB/T 2423.3 - 2016 Environmental testing - Part 2: Testing method - Test Cab: Damp heat, steady state (IEC 60068-2-78: 2012, IDT)
IEC 60270 High-voltage test techniques - Partial discharge measurements
Note: GB/T 7354-2018 High-voltage test techniques - Partial discharge measurements (IEC 60270: 2000, MOD)
IEC 61180: 2016 High-voltage test techniques for low-voltage equipment - Definitions, test and procedure requirements, test equipment
Note: GB/T 17627 - 2019 High-voltage test techniques for low-voltage equipment - Definitions, test and procedure requirements, test equipment (IEC 61180: 2016, MOD)
3 Terms, definitions and abbreviations
3.1 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
?
3.1.1
low-voltage supply system
all installations and plant provided for the purpose of generating, transmitting and distributing electricity
[Source: GB/T 2900.50-2008, 601-01-01, modified]
3.1.2
mains supply
AC or DC power distribution system (external to the equipment) that supplies operating power to the equipment
Note: Mains supply includes public or private utilities and, unless otherwise specified in this document, equivalent sources such as motor-driven generators and uninterruptible power supplies.
3.1.3
insulation coordination
mutual correlation of insulation characteristics of electrical equipment taking into account the expected micro-environment and other influencing stresses
Note: Expected voltage stresses are characterized in terms of the characteristics defined in 3.1.7 to 3.1.16.
[Source: IEC 60050-442: 2014, 442-09-01, modified]
3.1.4
clearance
shortest distance in air between two conductive parts
[Source: GB/T 4210-2015, 581-27-76]
3.1.5
creepage distance
shortest distance along the surface a solid insulating material between two conductive parts
[Source: GB/T 2900.83-2008, 151-15-50]
3.1.6
solid insulation
solid insulating material or a combination of solid insulating materials, placed between two conductive parts or between a conductive part and a body part
[Source: IEC 60050-903: 2015, 903-04-14, modified]
3.1.7
working voltage
highest RMS value of the AC or DC voltage across any particular insulation which can occur when the equipment is supplied at rated voltage
Note 1: Transient overvoltages are disregarded.
Note 2: Both open circuit conditions and normal operating conditions are taken into account.
[Source: IEC 60050-851: 2008, 851-12-31]
3.1.8
steady-state working voltage
working voltage after the transient overvoltage phenomena have subsided and not taking into account short-term voltage variations
3.1.9
steady-state peak voltage
peak value of the steady-state working voltage
3.1.10
recurring peak voltage
Urp
maximum peak value of periodic excursions of the voltage waveform resulting from distortions of an AC voltage or from AC components superimposed on a DC voltage
Note: Random overvoltages, for example due to occasional switching, are not considered to be recurring peak voltages.
[Source: IEC 60050-442: 2014, 442-09-15]
3.1.11
overvoltage
any voltage having a peak value exceeding the corresponding peak value of maximum steady-state working voltage at normal operating conditions
3.1.12
temporary overvoltage
overvoltage at power frequency of relatively long duration
[Source: IEC 60050-614: 2016, 614-03-13, modified]
?
3.1.13
transient overvoltage
short duration overvoltage of a few milliseconds or less, oscillatory or non-oscillatory, usually highly damped
[Source: IEC 60050-614: 2016, 614-03-14, modified]
3.1.14
withstand voltage
voltage to be applied to a specimen under specified test conditions which does not cause breakdown of insulation and/or flashover of a satisfactory specimen
3.1.15
impulse withstand voltage
highest peak value of impulse voltage of prescribed form and polarity, which does not cause breakdown of the insulation under specific conditions
[Source: IEC 60050-442: 2014, 442-09-18, modified]
3.1.16
temporary withstand overvoltage
highest RMS value of a temporary overvoltage which does not cause breakdown of insulation under specified conditions
[Source: IEC 60050-442: 2014, 442-09-19]
3.1.17
rated voltage
Un
value of voltage assigned by the manufacturer, to a component, device or equipment and to which operation and performance characteristics are referred
Note: Equipment may have more than one rated voltage value or may have a rated voltage range.
[Source: IEC 60050-442: 2014, 442-09-10, modified]
3.1.18
rated insulation voltage
Ui
value of the RMS withstand voltage assigned by the manufacturer to the equipment or to apart of it, characterizing the specified (long-term) withstand capability of its insulation
Note: The rated insulation voltage is equal to or greater than the rated voltage of equipment which is primarily related to functional performance.
Foreword i
Introduction iii
1 Scope
2 Normative references
3 Terms, definitions and abbreviations
3.1 Terms and definitions
3.2 Abbreviations
4 Basic technical characteristics for insulation coordination
4.1 General requirements
4.2 Voltages
4.3 Overvoltage categories
4.4 Frequency
4.5 Pollution
4.6 Insulating material
4.7 Environmental aspects
4.8 Duration of voltage stress
4.9 Electrical field distribution
5 Design for insulation coordination
5.1 General requirements
5.2 Dimensioning of clearances
5.3 Dimensioning of creepage distances
5.4 Requirements for design of solid insulation
6 Test and measurement
6.1 General requirements
6.2 Verification of clearances
6.3 Verification of creepage distances
6.4 Verification of solid insulation
6.5 Dielectric test on complete equipment
6.6 Other tests
6.7 Measurement of the attenuation of the transient overvoltages
6.8 Measurement of clearance and creepage distance
Annex A (Informative) Basic parameters on withstand characteristics of clearances
Annex B (Informative) Nominal voltages of mains supply for different modes of overvoltage control
Annex C (Normative) Partial discharge test methods
C.1 Test circuit
C.2 Test parameters
C.3 Requirements for measuring instruments
C.4 Calibration
Anne D (Informative) Additional information on partial discharge test methods
D.1 Measurement of partial discharge (PD), PD inception and extinction voltage
D.2 Description of PD test circuits (see Figure D.1)
D.3 Precautions for reduction of noise
D.4 Application of multiplying factors for test voltages
Annex E (Informative) Comparison of creepage distances specified in Table F.5 and clearances in Table A.1
Annex F (Normative) Tables
Annex G (Informative)Determination of clearance distances according to 5.2
Annex H (Informative) Determination of creepage distances according to 5.3
Bibliography
Figure 1 Recurring peak voltage
Figure 2 Determination of the width (W) and height (H) of a rib
Figure 3 Test voltages
Figure 4 Across the groove
Figure 5 Contour of the groove
Figure 6 Contour of the groove with angle
Figure 7 Contour of rib
Figure 8 Uncemented joint with grooves less than X
Figure 9 Uncemented joint with grooves equal to or more than X
Figure 10 Uncemented joint with a groove on one side less than X
Figure 11 Creepage distance and clearance through an uncemented joint >X mm
Figure 12 Creepage distance and clearance to a head of screw more than X
Figure 13 Creepage distance and clearance to a head of screw less than X
Figure 14 Creepage distance and clearance with conductive floating part
Figure A.1 Withstand voltage at 2 000m above sea level
Figure A.2 Experimental data measured at approximately sea level and their low limits for inhomogeneous field
Figure A.3 Experimental data measured at approximately sea level and their low limits for homogeneous field
Figure C.1 Earthed specimen
Figure C.2 Unearthed specimen
Figure C.3 Calibration of earthed specimen
Figure C.4 Calibration of unearthed specimen
Figure D.1 Partial discharge test circuits
Figure E.1 Comparison between creepage distances specified in Table F.5 and clearances in Table A.1
Figure G.1 Determination of clearance distances according to 5.2
Figure H.1 Determination of creepage distances according to 5.3
Table 1 Dimension of grooves
Table A.1 Withstand voltages for an altitude of 2 000m (kV)
Table A.2 Altitude correction factors for clearance
Table B.1 Inherent control or equivalent protective control
Table B.2 Cases where protective control is necessary and control is provided by surge protective device having a ratio of voltage protection level to rated voltage not smaller than that specified in IEC 61643 (all parts)
Table F.1 Rated impulse withstand voltage for equipment energized directly from the mains supply
Table F.2 Clearances to withstand transient overvoltages
Table F.3 Single-phase (three-wire or two-wire) AC or DC systems
Table F.4 Three-phase (four-wire or three-wire) AC systems
Table F.5 Creepage distances to avoid failure due to tracking
Table F.6 Test voltages for verifying clearances only at different altitudes
Table F.7 Severities for conditioning of solid insulation
Table F.8 Dimensioning of clearances to withstand steady-state peak voltages, temporary overvoltages or recurring peak voltages b
Table F.9 Additional information concerning the dimensioning of clearances to avoid partial discharge
Table F.10 Altitude correction factors for clearance
