Rotating electrical machines - Part 27-5: Off-line measurement of partial discharge inception voltage on winding insulation under repetitive impulse voltage

IEC TS 60034-27-5:2021 provides an off-line measurement method of the partial discharge inception and extinction voltage on winding insulation under repetitive impulse voltage. This document is relevant to rotating machines supplied by a voltage source converter.

General Information

Status
Published
Publication Date
06-Apr-2021
Technical Committee
Current Stage
PPUB - Publication issued
Completion Date
07-Apr-2021
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IEC TS 60034-27-5:2021 - Rotating electrical machines - Part 27-5: Off-line measurement of partial discharge inception voltage on winding insulation under repetitive impulse voltage
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IEC TS 60034-27-5
Edition 1.0 2021-04
TECHNICAL
SPECIFICATION
colour
inside
Rotating electrical machines –
Part 27-5: Off-line measurement of partial discharge inception voltage on
winding insulation under repetitive impulse voltage
IEC TS 60034-27-5:2021-04(en)
---------------------- Page: 1 ----------------------
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IEC TS 60034-27-5
Edition 1.0 2021-04
TECHNICAL
SPECIFICATION
colour
inside
Rotating electrical machines –
Part 27-5: Off-line measurement of partial discharge inception voltage on
winding insulation under repetitive impulse voltage
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.160.01 ISBN 978-2-8322-9648-6

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TS 60034-27-5:2021 © IEC 2021
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms, definitions, symbols and abbreviated terms ......................................................... 8

4 Repetitive impulse voltages for PD measurement .......................................................... 11

4.1 General ................................................................................................................. 11

4.2 Waveform of single impulse voltage ...................................................................... 12

4.2.1 Waveform at impulse generator terminal without test object ........................... 12

4.2.2 Typical distortions of impulse waveform at the terminals of test object ........... 14

4.3 Train of single impulse voltage .............................................................................. 17

4.4 Step-by-step voltage increase and decrease using trains of single impulse

voltage .................................................................................................................. 18

4.5 Impulse voltage distribution inside rotating machines ............................................ 22

5 PD measurement methods with impulse voltage ............................................................ 23

5.1 General ................................................................................................................. 23

5.2 Electrical PD measurements ................................................................................. 23

5.2.1 General ......................................................................................................... 23

5.2.2 Coupling capacitor with higher order analogue filter ....................................... 23

5.2.3 HFCT with higher order analogue filter .......................................................... 24

5.2.4 Electromagnetic couplers ............................................................................... 25

5.3 Threshold level of PD detection ............................................................................ 26

5.4 Measuring system with impulse generator and computer ....................................... 27

5.5 Calculation and interpretation of RPDIV and RPDEV ............................................ 27

6 Impulse PD test procedure ............................................................................................ 28

6.1 Test object ............................................................................................................ 28

6.1.1 Twisted-pair or equivalent .............................................................................. 28

6.1.2 Motorette or formette ..................................................................................... 29

6.1.3 Complete winding and connection .................................................................. 29

6.2 Safety and environment during PD test ................................................................. 31

6.2.1 Grounding and floating of test objects during tests ......................................... 31

6.2.2 Environment during test ................................................................................. 31

6.3 Test procedure and reports ................................................................................... 32

Annex A (informative) Typical PD measurements on a complete winding ............................. 33

Annex B (informative) Example of PD data analysis using phase angle ................................ 35

Annex C (informative) Example of connection of complete windings .................................... 37

C.1 General ................................................................................................................. 37

C.2 Connections for three-terminal machines .............................................................. 37

C.3 Connections for four-terminal machines ................................................................ 40

Annex D (informative) Example of SBS voltage increase pattern of repetitive impulse ......... 41

Bibliography .......................................................................................................................... 42

Figure 1 – Block representation of measurement circuit for RPDIV and RPDEV .................... 11

Figure 2 – Simplified impulse generator (IG) circuit with a single switch S ............................ 12

Figure 3 – Output voltage at open terminal of IG with single switch ....................................... 13

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IEC TS 60034-27-5:2021 © IEC 2021 – 3 –

Figure 4 – Two impulses at open terminal of IG with single switch ........................................ 13

Figure 5 – Simplified IG circuit with four-arm (switch) bridge circuit ....................................... 13

Figure 6 – Output voltages at open terminal of four-arm bridge circuit ................................... 14

Figure 7 – Increase of rise time and decrease of peak voltage of triangular impulse ............. 15

Figure 8 – Increase of rise time and decrease of peak voltage of rectangular impulse........... 15

Figure 9 – Overshoot of peak and following fast oscillation of triangular impulse ................... 15

Figure 10 – Overshoot of peak and following fast oscillation of rectangular impulse .............. 16

Figure 11 – Typical "ringing" observed during bipolar rectangular voltage test ...................... 16

Figure 12 – Slow oscillating decay of triangular impulse ....................................................... 17

Figure 13 – Slow oscillating decay of rectangular impulse ..................................................... 17

Figure 14 – Schematic representation of train parameters of positive unipolar impulses ....... 18

Figure 15 – Schematic representation of train parameters of bipolar impulses ...................... 18

Figure 16 – SBS parameters of positive unipolar impulses .................................................... 19

Figure 17 – SBS voltage pattern of positive unipolar impulses for RPDIV and RPDEV .......... 19

Figure 18 – SBS voltage pattern of bipolarly distorted positive unipolar impulse ................... 20

Figure 19 – SBS voltage increase of bipolar impulses ........................................................... 20

Figure 20 – Representative scheme of conditioning procedure before RPDIV

measurement ........................................................................................................................ 21

Figure 21 – Schematic representation of phase/phase, phase/ground and turn/turn

voltages of the winding of a rotating machine fed from a two-level converter [2] ..................... 23

Figure 22 – Coupling capacitor with higher order analogue filter ........................................... 24

Figure 23 – Example of voltage impulse and PD pulse frequency spectra before (left)

and after (right) filtering ........................................................................................................ 24

Figure 24 – HFCT between supply and test object with higher order analogue filter .............. 25

Figure 25 – HFCT between test object and earth with higher order analogue filter ................ 25

Figure 26 – Circuit using an electromagnetic coupler (for example an antenna) to

suppress impulses from the test supply ................................................................................. 25

Figure 27 – Circuit using an electromagnetic UHF antenna ................................................... 26

Figure 28 – Schematic representation of noise, disturbance and threshold values ................ 26

Figure 29 – Example diagram of PD measurements with PC ................................................. 27

Figure 30 – Example of RPDIV and RPDEV calculation using a 50 % PD probability

against repetitive impulse voltage (Figure 12 of IEC TS 61934:2011, modified)..................... 28

Figure 31 – Representative scheme of voltage terminals for three-terminal machine

and four-terminal machine .................................................................................................... 30

Figure A.1 – Block diagram of PD measurement system used in RRT ................................... 33

Figure A.2 – Impulse pattern used in RRT and PD inception ................................................. 33

Figure B.1 – Example of PD phase angle pattern of sinusoidal voltage ................................. 35

Figure B.2 – Example of PD phase angle pattern of PWM voltage on the phase angle

of a sinusoidal one ................................................................................................................ 36

Figure B.3 – Example of PD phase angle pattern of PWM voltage on rectangular

voltage angle (PRPD pattern) ............................................................................................... 36

Figure C.1 – Connection of six-terminal machines................................................................. 37

Figure C.2 – Connection of three- or four-terminal machines (with N terminal) ...................... 37

Figure C.3 – Three-terminal machine connection, Type A (Table 2) ...................................... 38

Figure C.4 – Three-terminal machine connection, Type B (Table 2) ...................................... 38

Figure C.5 – Three-terminal machine connection, Type C (Table 2) ...................................... 38

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– 4 – IEC TS 60034-27-5:2021 © IEC 2021

Figure C.6 – Three-terminal machine connection, Type D (Table 2) ...................................... 39

Figure C.7 – Three-terminal machine connection, Type E (Table 2) ...................................... 39

Figure C.8 – Three-terminal machine connection, Type F (Table 2) ...................................... 39

Figure C.9 – Four-terminal machine with earthed N terminal – Connection types

(Table 3) ............................................................................................................................... 40

Figure D.1 – SBS voltage increase of alternating train of unipolar impulses .......................... 41

Table 1 – Typical ranges of impulse voltage parameters at terminal of test object to be

reported ................................................................................................................................ 21

Table 2 – Connection of complete winding of three-terminal machine ................................... 30

Table 3 – Connection of complete winding of four-terminal machine ..................................... 31

Table A.1 – Parameters used in RRT .................................................................................... 33

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IEC TS 60034-27-5:2021 © IEC 2021 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ROTATING ELECTRICAL MACHINES –
Part 27-5: Off-line measurement of partial discharge inception
voltage on winding insulation under repetitive impulse voltage
FOREWORD

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9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent

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The main task of IEC technical committees is to prepare International Standards. In exceptional

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Technical specifications are subject to review within three years of publication to decide whether

they can be transformed into International Standards.

IEC TS 60034-27-5, which is a Technical Specification, has been prepared by IEC technical

committee 2: Rotating machinery.
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– 6 – IEC TS 60034-27-5:2021 © IEC 2021
The text of this Technical Specification is based on the following documents:
Draft TS Report on voting
2/1955/DTS 2/1962A/RVDTS

Full information on the voting for the approval of this Technical Specification can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

NOTE A table of cross-references of all IEC TC 2 publications can be found on the IEC TC 2 dashboard on the IEC

website.

The committee has decided that the contents of this document will remain unchanged until the

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IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

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of its contents. Users should therefore print this document using a colour printer.

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IEC TS 60034-27-5:2021 © IEC 2021 – 7 –
INTRODUCTION

The recent development of power electronics technology has led to various power drive systems

(PDS) of variable-speed rotating electrical machines. The new influences of PDS on rotating

machines are introduced in IEC TS 60034-25 [1] . This document points out that electrical

insulation of machine winding is exposed to numerous voltage impulses due to the repetitive

fast switching of power devices in PDS. The severity of the impulses depends on ratings of

converter and machines, converter topology, length of cable between machine and converter,

filtering equipment and so on.

IEC 60034-18-41 [2], published in 2014, is the first International Standard which describes

design qualification and type tests for Type I (partial discharge free) insulation systems used in

converter-fed rotating electrical machines. In this document, both tests require partial discharge

(PD) tests with power frequency voltage or impulse excitation. As for PD measurements with

impulse excitation, IEC 60034-18-41 cites IEC TS 61934, which provides a technical

explanation and several PD measuring methods, in general. For practical test guidance specific

to winding insulation of rotating machines, this document was prepared as an off-line

measurement of PD inception and extinction voltages during repetitive impulse condition,

RPDIV and RPDEV.
___________
Numbers in square brackets refer to the Bibliography
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– 8 – IEC TS 60034-27-5:2021 © IEC 2021
ROTATING ELECTRICAL MACHINES –
Part 27-5: Off-line measurement of partial discharge inception
voltage on winding insulation under repetitive impulse voltage
1 Scope

This document provides an off-line measurement method of the partial discharge inception and

extinction voltage on winding insulation under repetitive impulse voltage. This document is

relevant to rotating machines supplied by a voltage source converter.
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.

IEC 60034-27-1, Rotating electrical machines – Part 27-1: Off-line partial discharge

measurements on the winding insulation

IEC TS 61934:2011, Electrical insulating materials and systems – Electrical measurement of

partial discharges (PD) under short rise time and repetitive voltage impulses

IEC TS 62478, High voltage test techniques – Measurement of partial discharges by

electromagnetic and acoustic methods
3 Terms, definitions, symbols and abbreviated terms

For the purposes of this document, the terms, definitions, symbols and abbreviated terms given

in IEC 60034-27-1, IEC TS 61934, and the following 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
partial discharge

localized electrical discharge that only partially bridges the insulation between conductors and

which can or cannot occur adjacent to a conductor
3.2
repetitive partial discharge inception voltage
RPDIV

minimum peak-to-peak impulse voltage at which more than five PD pulses occur on ten voltage

impulses of the same peak-to-peak values when the impulse voltage applied to the test object

is increased with step-by-step method

Note 1 to entry: This is a mean value for the specified test time and a test arrangement where the voltage applied

to the test object is increased with the step-by-step method. Details are mentioned in 5.5.

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IEC TS 60034-27-5:2021 © IEC 2021 – 9 –
3.3
repetitive partial discharge extinction voltage
RPDEV

maximum peak-to-peak impulse voltage at which fewer than five PD pulses occur on ten voltage

impulses of the same peak-to-peak values when the voltage applied to the test object is

decreased with step-by-step method from a higher value at which such discharges are observed

Note 1 to entry: This is a mean value for the specified test time and a test arrangement where the voltage applied

to the test object is decreased with the step-by-step method. Details are mentioned in 5.5.

3.4
unipolar impulse
voltage impulse, the polarity of which is either positive or negative
Note 1 to entry: Details are mentioned in 4.2.
3.5
bipolar impulse

voltage impulse, the polarity of which changes alternately from positive to negative or vice versa

3.6
peak-to-peak impulse voltage
pk/pk
maximum numerical value of voltage reached from the lowest value impulse

Note 1 to entry: The definition of peak-to-peak voltage is clarified in Clause 4.

Note 2 to entry: U is used for the entire waveform of the impulse including distorted impulses.

pk/pk
3.7
impulse rise time
time for the voltage to rise from 10 % to 90 % of its final value
3.8
impulse decay time

time interval between the instants at which the instantaneous values of a triangular impulse

decrease from a specified upper value to a specified lower value
3.9
impulse fall time

time for the voltage of a rectangular impulse to fall from 90 % to 10 % of its initial value

3.10
impulse width

interval of time between the first and last instants at which the instantaneous value of a single

impulse reaches a specified fraction of its impulse magnitude or a specified threshold

3.11
time between two successive impulses

time between two successive impulses with the same waveform – in a considered set of pulses,

for example, for one period
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– 10 – IEC TS 60034-27-5:2021 © IEC 2021
3.12
impulse voltage repetition rate
average of the inverse of the time between two successive impulses t
3.13
train of impulse

sequence of repetitive impulse voltages with the same waveform parameters, including peak-

to-peak impulse voltage, rise time, decay time, impulse width, fall time, polarity and time interval

between impulses
Note 1 to entry: Details are mentioned in 4.3.
3.14
step-by-step method
SBS method

method of impulse voltage application of trains of repetitive impulse with step-by-step increase

and decrease of peak values
Note 1 to entry: Details are mentioned in 4.4.
3.15
starting applied voltage U during step-by-step method
pk/pk
Note 1 to entry: See Figure 16 and Figure 17.
3.16
maximum applied voltage U during step-by-step method
pk/pk
Note 1 to entry: See Figure 16 and Figure 17.
3.17
increase or decrease voltage U during step-by-step method
pk/pk
Note 1 to entry: See Figure 16 and Figure 17.
3.18
number of impulses in a train during step-by-step method
Note 1 to entry: See Figure 16.
3.19

rest time between two trains of impulses with voltage step ∆U during step-by-step method

Note 1 to entry: See Figure 16.
3.20

ratio of U value of distorted waveform to original U at open terminal of an impulse

pk/pk pk/pk
generator
3.21
conditioning

pre-application of conditioning voltage before PD test for stable measurement condition

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IEC TS 60034-27-5:2021 © IEC 2021 – 11 –
3.22
ringing

transient oscillation of impulse voltage that is influenced by the circuit impedance

3.23
noise

electric noise caused by thermal white noise from PD detection circuit or impulse generator

which may lower PD detection sensitivity
3.24
disturbance

electric and electromagnetic transient impulse from impulse generator or adjacent electric

devices which may disturb PD pulse waveform observation
3.25
motorette

special test model used for the evaluation of the electrical insulation systems of random-wound

windings
3.26
formette

special test model used for the evaluation of the electrical insulation systems for form-wound

windings
3.27
parallel winding

special test winding in which the turn/turn insulation is simulated by at least two electrically

isolated conductors wound in parallel, one of which is grounded and the other is energized

4 Repetitive impulse voltages for PD measurement
4.1 General

This document describes RPDIV and RPDEV as repetitive partial discharge inception and

extinction voltage of test objects under repetitive impulse voltage. They were first defined in

IEC TS 61934 and are redefined in this document. Both RPDIV and RPDEV have two features

compared with the conventional PDIV and PDEV under sinusoidal voltage defined in IEC 60034-

27-1. The first feature is the clear definition of repetitive impulse voltage with distortion and the

second one is 50 % PD occurrence probability.
Figure 1 – Block representation of measurement circuit for RPDIV and RPDEV

Figure 1 shows a representative scheme of a measurement circuit for RPDIV and RPDEV as a

block diagram. Repetitive impulse voltage from an impulse generator (IG) are mentioned in

detail in this Clause 4. PD measuring methods are mentioned in Clause 5. Subclause 6.1

describes test objects of both model samples and complete windings. A four-terminal test object

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– 12 – IEC TS 60034-27-5:2021 © IEC 2021
is illustrated in
...

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