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GB/T 20833.1-2021 English PDF (GBT20833.1-2021)

GB/T 20833.1-2021 English PDF (GBT20833.1-2021)

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GB/T 20833.1-2021: Rotating electrical machines -- The winding insulation -- Part 1: Off-line partial discharge measurements

GB/T 20833.1-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 29.160.01
K 20
GB/T 20833.1-2021 / IEC 60034-27-1:2017
Replacing GB/T 20833.1-2016
Rotating Electrical Machines – The Winding Insulation –
Part 1: Off-Line Partial Discharge Measurements
(IEC 60034-27-1:2017, Rotating Electrical Machines – Part 27-1: Off-
Line Partial Discharge Measurements on the Winding Insulation, IDT)
ISSUED ON: MARCH 09, 2021
IMPLEMENTED ON: OCTOBER 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
Introduction ... 6
1 Scope ... 8
2 Normative References ... 9
3 Terms and Definitions ... 9
4 Nature of PD in Rotating Machines ... 12
5 Measuring Technologies and Instrumentation ... 15
6 Visualization of Measurements ... 18
7 Test Circuits ... 21
8 Normalization of Measurements ... 27
9 Test Procedures ... 30
10 Interpretation of Test Results ... 36
11 Test Report ... 42
Annex A (Informative) Influence Parameters of Test Frequency to Testing Procedure ... 46
Annex B (Informative) Alternative Methods to Determine Discharge Magnitudes ... 48 Annex C (Informative) Other Off-Line Methods for PD Detection and Methods for Localization ... 51
Annex D (informative) External noise, Disturbance and Sensitivity ... 53 Annex E (informative) Methods of Disturbance Suppression ... 57
Annex F (informative) Interpretation of PD Magnitude Data and Phase Resolved PD Patterns ... 63
Annex G (informative) Test Circuits for Complete Windings ... 68
Annex H (Informative) Wide-Band and Narrow-Band Measuring Systems ... 74 Bibliography ... 76
Foreword
GB/T 20833 Rotating Electrical Machines – The Winding Insulation can be divided into the following 4 parts:
--- Part 1: Off-Line Partial Discharge Measurements;
--- Part 2: On-Line Partial Discharge Measurements;
--- Part 3: Dielectric Dissipation Factor Measurement;
--- Part 4: Measurement of Insulation Resistance Polarization Index.
This Part is Part 1 of GB/T 20833.
This Part was drafted as per the rules stipulated in GB/T 1.1-2009.
This Part replaced GB/T 20833.1-2016 Rotating Electrical Machines – The Stator Winding Insulation of Rotating Electrical Machines – Part 1: Off-Line Partial Discharge Measurements. Compared with GB/T 20833.1-2016, the major technical changes of this Part are as follows: --- Modify the Scope of the standard and Normative References (see Clause 1 and Clause 2 of this Edition; Clause 1 and Clause 2 of the 2016 Edition);
--- Add Terms and Definitions (see Clause 3 of this Edition);
--- Modify the nature of partial discharge in the motor (see Clause 4 of this Edition; Clause 4 of the 2016 Edition);
--- Modify the impact of measuring instruments (see 5.4 of this Edition; 5.4 of the 2016 Edition);
--- Modify the minimum range of partial discharge data expression (see 6.2 of this Edition; 6.2 of the 2016 Edition);
--- Add calibration pulse level and tolerance (see 7.1 of this Edition); ---Modify the standard measurement (see 7.3.2 and 7.3.3 of this Edition; 7.3.2 of the 2016 Edition);
--- Add the use of integrated test equipment (see 7.3.4 of this Edition); --- Modify the partial discharge measurement of windings and winding components (see 9.1 of this Edition; 9.1 of the 2016 Edition);
--- Delete the electromagnetic probe (see 9.2.2 of the 2016 Edition);
--- Modified the evaluation of test results (see 10.1, 10.2.1 and 10.3.1 of this Edition; 10.1, 10.2.1 and 10.3.1 of the 2016 Edition);
--- Delete the annex of on-line partial discharge measurement (see Annex A of the 2016 Edition);
--- Add the influence of the test frequency parameter on the test process (see Annex A of this Edition);
--- Add other methods for determining the amplitude of partial discharge (see Annex B of this Edition);
--- Modify the method of off-line partial discharge detection and off-line location (see Annex C of this Edition, Annex B of the 2016 Edition);
--- Add interpretation of partial discharge measurement and induction discharge/vibration spark from terminal and star-connected neutral point (see Annex D of this Edition); --- Add the complete winding measurement connection circuit (see Annex G of this Edition); --- Modify the broadband and narrowband systems (see Annex H, 5.4 of the 2016 Edition). This Part used translation method to equivalently adopt IEC 60034-27-1:2017 Rotating Electrical Machines – Part 27-1: Off-Line Partial Discharge Measurements on the Winding Insulation.
The Chinese documents that have consistent correspondence with the international documents cited in this part are as follows:
--- GB/T 7354-2018 High-voltage test techniques - Partial discharge measurements (IEC 60270-2000, MOD);
--- GB/T 16927.1-2011 High-voltage test techniques—Part 1: General definitions and test requirements (IEC 60060-1:2010, MOD);
--- GB/T 16927.2-2013 High-voltage test techniques - Part 2: Measuring systems (IEC 60060-2:2010, MOD);
--- GB/T 17948.4-2016 Rotating electrical machines - Functional evaluation of insulation systems - Test procedures for form-wound windings - Evaluation by electrical endurance (IEC 60034-18-32:2010, IDT);
--- GB/T 22720.2-2019 Rotating electrical machines - Qualification tests for the partial discharge resistant electrical insulation systems (Type Ⅱ) used in rotating electrical machines fed from voltage converters (IEC 60034-18-42:2017, IDT);
--- GB/T 20833.2-2016 Rotating electrical machines - The stator winding insulation of Rotating Electrical Machines – The Winding Insulation –
Part 1: Off-Line Partial Discharge Measurements
1 Scope
This Part of GB/T 20833 provides a common basis with respect to partial discharge off-line measurements on the winding insulation of rotating electrical machines: – measuring techniques and instruments;
– the arrangement of test circuits;
– normalization and testing procedures;
– noise reduction;
– the documentation of test results;
– the interpretation of test results.
The measurement methods described in this document are applicable to stator windings of machines with or without conductive slot coating and to the stator windings of machines made with form wound or random wound windings. In special cases like high voltage rotor field windings, this document is applicable as well. The measurement methods are applicable when testing with alternating sinusoidal voltages from 0.1 Hz up to 400 Hz; see Annex A. Interpretation guidelines are given in this document and are applicable only if all the following requirements are fulfilled:
– Measurements performed with power frequency of 50 Hz or 60 Hz, or when testing with power supply within a frequency range of 45 Hz to 65 Hz.
– Form wound windings and winding components such as bars and coils.
– Winding with conductive slot coating. This is usually valid for machines with voltage rating of 6 kV and higher.
For machines with random wound windings, form-wound windings without conductive slot coating, and testing at frequencies differing from power frequencies, the interpretation guidelines are not applicable. The testing procedures for off-line PD-measurements of this document can be used for assessing the uniform quality of manufacturing or/and the trending of these kind of windings as well as converter driven machine windings. NOTE: Testing of low voltage machines with so called Type I insulation systems is defined in IEC 60034- 18-41. Testing procedures for qualification of converter driven high voltage machines with so called Type II insulation systems are dealt with in IEC 60034-18-42 (in addition to the optional electric tests described therein).
2 Normative References
The following documents are essential to the application of this Document. For the dated documents, only the versions with the dates indicated are applicable to this Document; for the undated documents, only the latest version (including all the amendments) is applicable to this Document.
IEC 60034-18-32 Rotating Electrical Machines – Part 18-32: Functional Evaluation of Insulation Systems – Test Procedures for Form-Wound Windings – Evaluation by Electrical Endurance
IEC 60034-18-42 Rotating Electrical Machines – Part 18-42: Partial Discharge Resistant Electrical Insulation Systems (Type II) Used in Rotating Electrical Machines Fed from Voltage Converters – Qualification Tests
IEC TS 60034-27-2 Rotating Electrical Machines – Part 27-2: On-Line Partial Discharge Measurements on the Stator Winding Insulation of Rotating Electrical Machines IEC 60034-27-4 Rotating Electrical Machines – Part 27-4: Measurement of Insulation Resistance and Polarization Index of Winding Insulation of Rotating Electrical Machines IEC 60060-1 High-Voltage Test Techniques – Part 1: General Definitions and Test Requirements
IEC 60060-2 High-Voltage Test Techniques – Part 2: Measuring Systems
IEC 60270:2000 High-Voltage Test Techniques – Partial Discharge Measurements 3 Terms and Definitions
For the purposes of this document, the terms and definitions given in IEC 60270 and the following apply.
3.1 Partial discharge; PD
Localized electrical discharge that only partially bridges the insulation between conductors and which can or cannot occur adjacent to a conductor.
3.2 Off-line measurement
at phase terminal side of stator winding. The PD activity results in increased ageing through erosion of the main insulation. Coil loosening can also lead to mechanical abrasion in a severe case.
As insulation erosion is caused by high voltage induced slot discharges, it will occur more severely at bars/coils near HV terminals. Therefore, off-line PD measurements will provide different PD intensity and, sometimes, patterns at terminal and neutral side, in the presence of slot discharges.
Bar or coil vibration within the slots during operation, caused e.g., by forces due to the electromagnetic field and in the condition that the bars and coils are not tight anymore, may be the initial state of slot portion coating damage. Under certain conditions vibration sparking may occur during machine operation. This is caused by intermitted interruption of driven currents which are caused by electromagnetically induced voltages. Although it is not a PD phenomenon it may occur similarly during measurements.
When the conductive slot coating is deteriorated by the vibration sparking, in standstill these can be measured as slot discharges. Since vibration sparking is driven by the magnetic field this phenomenon can occur mainly in the slot section of each bar or coil, from terminal side to neutral side, the effect may be measured on both sides of the winding. Comparative measurements including pattern analysis on terminal and neutral side may give an indication for vibration sparking. F.1.4 provides more background information.
4.2.4 End-winding gap and surface discharges
Partial discharges in the end-winding area may occur at several locations with high local electric field strengths. Such discharges usually occur at interfaces between different elements of the stator winding overhang. If the stress control coating of the end-winding becomes ineffective because of poorly designed interfaces, contamination, porosity, thermal effects, etc., reliable field grading is no longer ensured and surface discharges will develop, which may gradually erode the insulation and surface materials. This is normally a slow ageing mechanism. The PD behavior might be subjected to relatively fast changes due to surface effects. In addition, PD may occur between phases, for example due to inadequate interface clearance, at elements of the overhang support system, or as phase to ground discharges on the end- winding surface.
4.2.5 Foreign conductive materials discharges
Conductive contamination of the winding may result in a strong local concentration of partial discharges. These may result in a localized damage in the insulation. More dangerous may be larger metal pieces such as broken bolts or screws, as well as unintentionally forgotten tools. Beside the local concentration of PD and its potentially damaging effect it may lead to secondary impact such as immediate mechanical damage or abrasion driven by the impact of the magnetic field to such metal pieces.

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