GB/T 20833.2-2025Rotating electrical machines - Winding insulation - Part 2: On-line partial discharge measurements on the stator winding insulation (English PDF)

Foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for standardization work Part 1: Structure and drafting rules for standardization documents" Drafting.

This document is Part 2 of GB/T 20833 "Insulation of rotating electrical machines windings". GB/T 20833 has been published in the following parts.

--- Part 1: Offline partial discharge measurement;

--- Part 2: On-line partial discharge measurement of stator winding insulation;

--- Part 3: Measurement of dielectric loss factor;

--- Part 4: Measurement of insulation resistance and polarization index;

--- Part 5: Off-line measurement of partial discharge inception voltage under repetitive impulse voltage.

This document replaces GB/T 20833.2-2016 "Rotating electrical machines - Insulation of stator windings of rotating electrical machines - Part 2: On-line partial discharge Compared with GB/T 20833.2-2016, in addition to structural adjustments and editorial changes, the main technical changes are as follows.

--- Added the characteristics of signal transmission in online measurement of partial discharge of rotating motors (see 6.3);

--- Changed the design requirements of PD sensors (see 6.4, 6.4 of the 2016 edition);

--- Added standardization requirements for partial discharge measurement systems (see Chapter 8);

--- Changed the limiting conditions of the insulation structure to be evaluated in Figure 1 (see Figure 1, 4.2 of the 2016 edition);

--- Changed the partial discharge online measurement parameters, results, and partial discharge mode assessment rules (see Chapter 11, 2016 Edition Chapter 11);

--- Changed the test report requirements (see Chapter 12, Chapter 12 of the 2016 edition);

--- Added Table 1 to obtain the stable operating conditions of the effective trend of partial discharge (see Table 1);

--- Added Figure 1 partial discharge measurement system and its subsystems (see Figure 1);

--- Added Figure 2 frequency response channel hierarchy (see Figure 2);

--- Changed Figures 5, 7 and 9 (see Figures 5, 7 and 9, 2016 edition);

--- Added Figure 8 PRPD spectrum example (see Figure 8);

--- Added normative Appendix D Technical requirements for conventional partial discharge coupling capacitors (see Appendix D).

The following minimal editorial changes have been made to this document.

--- In order to coordinate with the existing standards, the name of the standard is changed to "Insulation of rotating electrical machines - Part 2: Insulation of stator windings" Internal Discharge Measurement.

This document is equivalent to IEC 60034-27-2:2023 "Rotating electrical machines - Part 27-2.On-line partial discharge in stator winding insulation" Measurement".

Introduction

Since online measurement of partial discharge (PD) of rotating electrical machines can reveal local weaknesses in the stator insulation structure and various arc and spark phenomena, However, several studies have shown that there are not only many different measurement methods, but also many different ways to analyze and ultimately evaluate the measurement data.

The standards and methods used for data collection are often very different and cannot be truly compared. Therefore, it is necessary to develop an international standard for online local amplification.

It gives clear guidance to users of electrical measurements to assess the condition of their insulation structures.

On-line partial discharge measurements are performed when the rotating machine is subjected to all the operating stresses, thermal, electrical, environmental and mechanical.

The winding will be affected by real stress during the measurement process, and the measurement is carried out under the normal action of basic load and peak load.

Partial discharge online testing can identify changes in winding insulation structure at an early stage and make real-time condition assessment a key component of predictive maintenance strategies.

Part.

It is recommended to use the same test equipment to measure partial discharges on motors of similar design and insulation structure under similar conditions.

Trend evaluation and comparison to ensure reliable assessment of stator winding insulation condition. Trend information provides a good metric to Indicates changes in insulation condition at an early stage. This provides the opportunity for further visual inspection at rest and offline testing during the next outage inspection.

Plan your time.

This document does not cover on-line partial discharge measurements of inverter-driven motors, as different measurement techniques are required to distinguish between the partial discharge from the inverter and the Noise from partial discharge between windings.

Limitations. The stator winding partial discharge online test produces relative measurement values, not absolute measurement values. This fundamentally limits Therefore, it is not possible to establish acceptance criteria with simple limits for new or rewound stator windings because as follows.

---There are many types of partial discharge sensors (PD sensors) and recording and analysis instruments. Often these instruments are incompatible and the same partial discharge activity can produce different results.

---Even if the same measurement system is used, the high-frequency partial discharge pulse will contact the winding on the way from the starting point to the measurement point, such as the winding end.

Therefore, even if the actual type of partial discharge source (PD source) is the same, the difference between different winding designs may PD measurements on motors with different rated values will produce different PD results.

---Different types of winding defects produce different partial discharge amplitudes and have different effects on insulation breakdown.

There is no strong correlation between the risk of edge failure.

---Partial discharge activity can occur close to or far from the PD sensor. Generally, if the PD source is far from the PD sensor Due to the pulse attenuation, it produces a larger pulse at the PD sensor at the end compared with the PD source at the adjacent phase connection.

The response of students is small.

The user should also be aware that there is no evidence that the time to stator winding insulation failure can be predicted using any partial discharge amplitude, either alone or in combination.

To provide a more complete picture of the condition of the stator insulation, partial discharge measurements need to be supplemented with other electrical tests.

Technology is developing rapidly, and partial discharge pattern recognition is being used to determine the root cause of insulation degradation processes, especially when multiple processes occur simultaneously.

There is still a certain degree of subjectivity.

The noise and interference of the electrical environment have a great impact on the online partial discharge measurement. Partial discharge and noise cross coupling between different phases Therefore, different analog and digital noise suppression techniques should be used to improve the sensitivity of partial discharge measurement and improve the accuracy of partial discharge measurement.

Advanced partial discharge analysis methods.

Users should note that due to the principle of the partial discharge measurement method, not all insulation-related problems in the stator winding can be detected by online Partial discharge measurement detection. For example, due to continuous leakage current insulation faults caused by conductive paths between different potentials in the insulation structure, or with Normal delamination partial discharge is much smaller than the partial discharge activity caused by tiny main insulation cracks, or there is no pulse discharge phenomenon.

GB/T 20833 provides functional assessment and special test procedures for the insulation of rotating electrical machine windings and is intended to consist of five parts.

--- Part 1: Off-line partial discharge measurement. The purpose is to specify the general basic method for off-line partial discharge measurement of rotating electrical machine winding insulation.

Basic specifications include. measurement methods and instruments, test circuit layout, standardization of test procedures, noise reduction, test result documentation, Preparation of test materials and evaluation of test results.

--- Part 2: On-line partial discharge measurement of stator winding insulation. The purpose is to specify the rated voltage of 3kV and above, non-variable frequency on-line measurement of partial discharge of stator winding insulation of rotating electrical machines powered by a DC motor, including. measurement technology and instruments, layout of test circuit, standard Standardization and sensitivity assessment, measurement procedures, noise reduction, test result documentation, and test result evaluation.

--- Part 3: Dielectric loss factor measurement. The purpose is to establish the dielectric loss factor of the rated voltage of 6kV and above under power frequency AC voltage.

Necessary conditions for measuring dielectric loss factor of single formed stator bars and coils of the machine.

--- Part 4: Insulation resistance and polarization index measurement. The purpose is to specify the low voltage, Recommended minimum values of insulation resistance and polarization index for windings of high-voltage AC and DC rotating electrical machines.

--- Part 5: Off-line measurement of partial discharge inception voltage under repetitive impulse voltage. The purpose is to specify the voltage type frequency conversion Off-line measurement method for the inception and extinction voltages of partial discharges in the winding insulation of rotating electrical machines fed by a DC motor and subjected to repetitive impulse voltages.

Winding insulation of rotating electrical machines Part 2.

Online partial discharge measurement of stator winding insulation

1 Scope

This document specifies the online measurement of partial discharge in the stator winding insulation of rotating electrical machines with rated voltage of 3kV and above and non-inverter powered.

include.

---Measurement techniques and instruments;

--- Layout of the test circuit;

---Standardization and sensitivity assessment;

---Measurement procedures;

---Noise reduction;

--- Preparation of test result documents;

---Evaluation of test results.

This document specifies a partial discharge test system and a method for detecting electrical partial discharges. The same measuring equipment and procedures can also be used to detect Measure sparks and arcs.

2 Normative references

The contents of the following documents constitute the essential clauses of this document through normative references in this document.

For referenced documents without a date, only the version corresponding to that date applies to this document; for referenced documents without a date, the latest version (including all amendments) applies to this document.

ISO 8528-9 Reciprocating internal combustion alternating current generating sets — Part 9: Measurement and evaluation of mechanical vibration Note. GB/T 2820.1-2022 Reciprocating internal combustion engine driven AC generating sets Part 1: Application, rating and performance (ISO 8528-1.

2018, IDT)

IEC 60034-27-1 Rotating electrical machines Part 27-1.Off-line partial discharge measurements on stator winding insulation Note. GB/T 20833.1-2021 Rotating electrical machine winding insulation Part 1: Off-line partial discharge measurement (IEC 60034-27-1:2017, IDT) IEC 60034-27-3 Rotating electrical machines - Part 27-3.Measurement of dielectric loss factor of stator windings of rotating electrical machines Note. GB/T 20833.3-2018 Rotating electrical machines - Measurement of dielectric loss factor of stator windings of rotating electrical machines (IEC 60034-27-3:2015, IDT) Note. GB/T 16927.1-2011 High voltage test technology Part 1: General definitions and test requirements (IEC 60060-1:2010, MOD) IEC 60068-2-6 Environmental testing Part 2-6.Test methods Test Fc. Vibration (sinusoidal)