IEC TR 63434:2023

IEC TR 63434 ®
Edition 1.0 2023-09
TECHNICAL
REPORT
Low voltage switchgear and controlgear – Partial discharge voltages and PD-
level in low voltage switchgear and controlgear

IEC TR TR 63434:2023-09(en)
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IEC TR 63434 ®
Edition 1.0 2023-09
TECHNICAL
REPORT
Low voltage switchgear and controlgear – Partial discharge voltages and PD-

level in low voltage switchgear and controlgear

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.130.20  ISBN 978-2-8322-7573-3

– 2 – IEC TR 63434:2023 © IEC 2023
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Basic information (physics) . 10
4.1 Discharge phenomena . 10
4.1.1 General . 10
4.1.2 Homogeneous electric fields . 10
4.1.3 Inhomogeneous electric fields. 11
4.2 Dimensioning examples . 14
4.2.1 General . 14
4.2.2 Influence of design and temperature on a series connection of
clearances and solid insulation for AC voltage . 17
4.2.3 Series connection of clearances and solid insulation by design for DC
voltage . 24
4.2.4 Solid insulation – dimensioning – material characteristics . 24
5 Application rules . 29
5.1 General . 29
5.2 Partial discharge considerations . 30
5.3 Measures to prevent/reduce the probability of partial discharges . 30
Annex A (informative) Research on partial discharge in low-voltage switchgear and
controlgear . 31
A.1 General . 31
A.2 Investigations on switchgear . 31
A.3 Reference to other products relevant for applications . 35
Annex B (informative) Voltage factors when considering partial discharge effects . 36
Bibliography . 38

Figure 1 – Temperature dependent variation of the breakdown field strength Ê of air
d
per Equation (1), α = 0,8, θ = 20 °C, p = p = 1 013 mbar . 11
Figure 2 – Inception voltage U depending on the electrode radius r, R ≫ r . 12
i,RMS
Figure 3 – Maximum electrical field strength Ê depending on the electrode edge radius r . 13
Figure 4 – Paschen curve Ê = f (p × d) for air . 13
d
Figure 5 – Principle terminal / contact arrangement of a 3-pole device, capacitive
voltage divider . 15
Figure 6 – Field strength in the air gap, inhomogeneous, η = 0,5 , ε = 4, cold state . 19
r2
Figure 7 – Field strength in the solid insulation, inhomogeneous, η = 0,5, ε = 4, cold
r2
state . 19
Figure 8 – Field strength in the air gap, inhomogeneous, ƞ = 0,5, ε = 12 at 130 °C
r2
operational temperature . 20
Figure 9 – Field strength in the solid insulation, inhomogeneous, ƞ = 0,5, ε = 12
r2
operational temperature . 20
Figure 10 – Gaps and voids in a solid and combined solid / gaseous insulation [7] . 21

Figure 11 – Model of a void of thickness t in an insulation wall of defined thickness d [20] . 23
Figure 12 – Principle arrangement of electrodes and insulation walls of a 3-pole device . 24
Figure 13 – Permissible field strength for dimensioning of solid insulation according to
Equation (18) . 25
Figure 14 – Breakdown at high frequency, solid insulation; d = 0,75 mm [23] . 26
Figure 15 – Breakdown at high frequency, solid insulation, influence of humidity;
conditioning at 50 °C; 1: mica-filled phenolic, d = 0,75 mm; 2: glass-silicone laminate, d
= 1,5 mm [24] . 27
Figure 16 – Dielectric strength Ê of different types of thermoplastic insulation material
d
depending on the temperature . 28
Figure 17 – Dielectric strength E of PA6-GF30 in dry and moist condition
d,RMS
(equilibrium moisture content at 23 °C/50 % RH) depending on the temperature θ (°C) . 29
Figure A.1 – Example of phase resolved partial discharge measurement on a MPSD at
room temperature and at elevated operational temperatures . 31
Figure A.2 – PD Testing (690 V, basic insulation, 20°C). 32
Figure A.3 – Inception (U ) and extinction (U ) voltage during partial discharge
i e
measurements on motor protection switching devices (MPSD) at elevated
temperatures . 33

Table 1 – Relationship between electrode radius r and corona inception voltage
U . 12
i,RMS
Table 2 – Ranking of the internal field strength of different gap and void shapes [7] . 22
Table A.1 – Inception U and extinction U voltage depending on the temperature as
i e
per Figure A.1 and Figure A.2 . 32
Table A.2 – Maximum discharge values and number of events observed at the test
voltage as per Figure A.1 and Figure A.2 . 32
Table A.3 – Ratings and design parameters of the investigated motor protection
switching devices (MPSD). 34
Table A.4 – Partial Discharge (PD) acceptance levels in different IEC documents. 35
Table B.1 – Coordination of rated RMS voltage with partial discharge voltage and
extinction voltage . 37

– 4 – IEC TR 63434:2023 © IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LOW VOLTAGE SWITCHGEAR AND CONTROLGEAR –

PARTIAL DISCHARGE VOLTAGES AND PD-LEVEL IN
LOW VOLTAGE SWITCHGEAR AND CONTROLGEAR

FOREWORD
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