GB/T 20833.4-2021 English PDFUS$644.00 · In stock
Delivery: <= 4 days. True-PDF full-copy in English will be manually translated and delivered via email. GB/T 20833.4-2021: Rotating electrical machines - The winding insulation - Part 4: Measurement of insulation resistance and polarization index Status: Valid
Basic dataStandard ID: GB/T 20833.4-2021 (GB/T20833.4-2021)Description (Translated English): Rotating electrical machines - The winding insulation - Part 4: Measurement of insulation resistance and polarization index Sector / Industry: National Standard (Recommended) Classification of Chinese Standard: K20 Word Count Estimation: 34,322 Issuing agency(ies): State Administration for Market Regulation, China National Standardization Administration GB/T 20833.4-2021: Rotating electrical machines - The winding insulation - Part 4: Measurement of insulation resistance and polarization index---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order. Rotating electrical machines - The winding insulation - Part 4.Measurement of insulation resistance and polarization index ICS 29.160.01 K20 National Standards of People's Republic of China Rotating motor winding insulation Part 4.Insulation resistance and polarization index measurement (IEC 60034-27-4.2018,Rotatingelectricalmachines- Released on 2021-03-09 2021-10-01 implementation State Administration of Market Supervision and Administration Issued by the National Standardization Management Committee Table of contentsForeword Ⅲ Introduction Ⅳ 1 Scope 1 2 Normative references 1 3 Terms and definitions 1 4 Insulation resistance components and influencing factors 2 5 Polarization index 3 6 Test of insulation resistance 3 7 Explanation of measurement results 8 8 Recommended limit values of insulation resistance and polarization index 9 9 Test report 10 Appendix A (informative appendix) Other DC tests 12 Appendix B (informative appendix) Current component of direct current 16 Appendix C (informative appendix) Example of test results of synthetic resin insulated high-voltage windings 20 Appendix D (informative appendix) Use test data to plot to estimate the slope parameter of temperature correction X 24 Appendix E (informative appendix) Test leakage current to evaluate phase-to-phase insulation resistance 25 Reference 27 Fig. 1 Equivalent circuit of winding insulation in DC voltage test Fig. 3 Figure 2 Connection mode of overall winding test 6 Figure 3 Connection mode for relative ground test 6 Figure A.1 Test of current and insulation resistance when the DAR calculation result is 1.09 Figure A.2 Charging and discharging currents after a 2.5kV step voltage is applied to the three-phase windings of a 50MVA hydraulic generator 13 Figure B.1 The relationship between different currents and time 16 Figure C.1 shows the relationship between the resultant current and time in clean and dry insulation on a logarithmic scale. 20 Figure C.2 The relationship between insulation resistance and time in clean and dry insulation 20 Figure C.3 Relationship between composite current and time in damp and polluted insulation 21 Figure C.4 Relationship between insulation resistance and time in damp and polluted insulation 21 Figure C.5 The relationship between the resultant current and time in the insulation of a dry and clean surface with a continuous end anti-corona layer 23 Figure C.6 The relationship between resistance and time in insulation with end anti-corona layer on a dry and clean surface 23 Figure D.1 Plot on logarithmic graph paper to estimate the slope parameter X 24 Figure E.1 The connection method of the phase-to-phase test, the test equipment is not connected to the ground, and other phase-to-phase combinations can also be used 25 Figure E.2 Measuring the phase-to-phase leakage current using a measuring instrument with a protective connection 26 Figure E.3 Measuring the phase-to-phase leakage current using a measuring instrument without a protective connection 26 Table 1 Value of parameter X used to correct temperature 4 Table 2 Guidelines for applied DC voltage range during insulation resistance measurement 7 Table 3 Minimum recommended value of insulation resistance at a reference temperature of 40°C 9 Table 4 The minimum recommended value of the polarization index of the high-voltage insulation structure 10 Table D.1 Example of insulation resistance test results under different winding temperatures 24 Rotating motor winding insulation Part 4.Insulation resistance and polarization index measurement1 ScopeThis part of GB/T 20833 specifies the test procedures for the insulation resistance and polarization index of the stator and rotor windings of rotating electrical machines. This section specifies the minimum recommended values for the insulation resistance and polarization index of the windings of rotating electrical machines with a rated power of 750W and above. This part Suitable for low-voltage, high-voltage AC and DC rotating motors.2 Normative referencesThe following documents are indispensable for the application of this document. For dated reference documents, only the dated version applies to this article Pieces. For undated reference documents, the latest version (including all amendments) is applicable to this document. IEC 60050-411 International Electrotechnical Vocabulary Chapter 411.Rotating Electric Machine (Internationalelectrotechnicalvocabulary- Chapter411.Rotatingmachinery)3 Terms and definitionsThe following terms and definitions defined by IEC 60050-411 apply to this document. 3.1 Rated voltage For three-phase AC motors, it refers to the rated line voltage between the two phases; for single-phase motors, it refers to the rated line voltage; for DC motors and excitation motors, Refers to the rated DC voltage. 3.2 Insulation resistance Rit The electrical insulation capability of the winding against DC current. At a certain time (t) after the voltage is applied, the applied DC voltage is divided by the The quotient of the total DC current of the insulation. Note 1.The voltage application time is usually 1min (Ri1) and 10min (Ri10), but other values can also be used. The unit of time t is stipulated. the unit of 1 to 10 is Minutes, the unit of 15 and above is seconds. Note 2.Insulation resistance is sometimes abbreviated as IR. 3.3 Polarization index PI The quotient of the insulation resistance measured at two different times. Usually, after applying DC voltage, t2 and t1 are 10min and 1min respectively This is an indicator of the insulation state. Note. For other times, see Appendix A, A.2. 3.4 Polarization current IP5 Polarization indexThe polarization index is the quotient of the insulation resistance at time t2 divided by the insulation resistance at time t1 after applying a DC voltage, see formula (1), where t2= 10min, t1=1min. PI= Ri10 Ri1 (1) In special applications, the quotient calculated from the insulation resistance at other times can also be used as the polarization index. Ming (see Appendix A). Reading more data within 10 minutes can provide more information. The polarization index reflects the change in insulation resistance between two specific time points. Therefore, it is better than a single insulation resistance value. It shows the contaminants and moisture deposits on the winding surface, and the moisture absorption of the windings. But it may not be able to judge due to unreasonable Internal pores caused by impregnation process and thermal damage. The polarization index can be used to evaluate whether the winding can be subjected to a withstand voltage test and whether it can be put into operation, and it can also provide an evaluation of the state of the insulation structure. Set the required information. Since the polarization current is negligible within 1 min to 10 min after the voltage is applied, the polarization index test may not be available It is used in small motors with random winding, field windings of generator rotors, non-insulated excitation, squirrel cage rotor windings and DC motor armatures. The polarization index depends on the type of insulation structure, especially the nature of the insulation material and the winding production process (for synthetic resins, insects, etc.) For paint and asphalt, see 7.1). At the same time, it also depends on the type of end anti-corona layer (see Appendix C, C.3) and the size of the test voltage (See 6.4.1). If the winding temperature is kept constant between 1min and 10min, then the temperature has little effect on the polarization index (see 6.1.2). The polarization index should reach the minimum requirement (see 8.3 for the recommended value) before the withstand voltage test or put into operation.6 Test of insulation resistance6.1 Factors affecting insulation resistance test 6.1.1 Overview Insulation resistance test results depend on environmental factors, mainly winding temperature and air humidity. The influence of winding temperature on insulation resistance can be Evaluate with empirical data or test measurements, which can be used to modify the insulation resistance test results at different temperatures (see 6.1.2). The relative humidity of the air affects the surface leakage current. This effect is usually difficult to evaluate because the relative humidity of the air mainly depends on the air. Slightly disregarded. 6.2 Testing equipment For the direct measurement method, the preferred device is an ohmmeter. When the reading of Ri1 is less than 5000MΩ, the digital high resistance meter should meet the following condition. ---Display. three digits; ---Accuracy. Reading accuracy ±5%, range accuracy ±5. If there is no insulation resistance meter, the insulation resistance can be obtained by measuring voltage and current (indirect method). This method may use regulated DC Power supply, voltmeter, microammeter. In fact, the voltage output by the DC voltage source will fluctuate, causing the current to also change. ic(t)=C0dU0/ dt. Since the capacitance C0 of most high-voltage motors is very large, the DC power supply should have minimal stability and noise to ignore this effect. According to the voltage and current readings, the insulation resistance is calculated according to formula (4). Rit=U/It (4) Where. Rit---Insulation resistance value at time t, in megaohms (MΩ); U ---The measured voltage of the DC voltage source (Voltmeter reading), in volts (V); It --- the measured current (ammeter reading) at time t, in microamperes (μA). When measuring large insulation resistance values, in order to avoid the influence of the leakage current and capacitance of the test cable, it is advisable to use a protective instrument. The whole set of equipment should raise the voltage to the test value within 5s. 6.3 Test product and test circuit 6.3.1 Overview According to the test target and its design, different test circuits are used. In order to check the minimum recommended value of insulation resistance, the entire winding should be checked Test; In order to check the insulation problems between the windings of each phase and the windings, if the windings of each phase can be easily disconnected, it should be carried out phase by phase measuring. In order to achieve the test purpose, the same connection method should be used. If possible, all external devices such as cables, switches, capacitors and current transformers should be disconnected from the windings. To record with Winding connection equipment. For the insulation resistance test of the direct water-cooled winding, it is advisable to completely drain the water to make the internal circuit completely dry. Maybe some water-cooled windings are manufactured The supplier has provided a method for measuring insulation resistance without draining the cooling water. Generally, if the water is not excluded, the conductivity of the water should be less than the production plant Recommended value of home. In this case, the conductivity of water will greatly affect the insulation resistance value, so it can be estimated that PI=1, Ri10= 1MΩ. In any case, untested winding components should be grounded to avoid adverse effects, such as compensation current or induced AC in the test loop Current. 6.3.2 Three-phase stator winding 6.3.2.1 Connection mode of integral winding to ground test The windings of all phases are connected together, as shown in Figure 2. Insulation test is an important part of motor calibration. It should be carried out before and after the test, and check with a high voltage resistance of about 100MΩ. Operation of equipment. This is especially important for battery-powered equipment. 6.7.2 Special procedures In order to obtain more information about the insulation status, other test procedures can also be used, see Appendix A for details.7 Explanation of measurement results7.1 Overview Insulation resistance and polarization index can be used in the following aspects, but not limited to. ---Assess whether a motor is suitable for withstand voltage test or put into operation, it can be based on the minimum estimation of insulation resistance and polarization index. Recommended value (see 7.2); ---As long as the test conditions of the controllable variables involved are the same, the historical data of the insulation resistance and polarization index of a given motor can be used An effective method for judging the change trend of its insulation state after several years (see 7.3); ---As long as the test conditions of the controllable variables involved are the same, compare the windings of each phase by testing the insulation resistance and polarization index or the same Insulation conditions of different motors designed. Based on the above points, the factors that affect the test results should be fully considered when testing (see 7.4). 7.2 Feasibility of test and operation Insulation resistance and polarization index can be used to evaluate the feasibility of the motor withstand voltage test and put into operation. Insulation resistance and poles of the motor The chemical index should be greater than the minimum recommended value (see Table 3 and Table 4). If the test value is less than the minimum recommended value, it is not advisable to carry out a withstand voltage test on the motor Or put into operation, unless there are design reasons or there are records of such lower values. Insulation resistance can also be used to determine whether the winding is damaged in the withstand voltage test. If the insulation resistance value after the withstand voltage test is much smaller than the test Before the test, it indicates that the insulation may be damaged during the withstand voltage test, even if the test voltage does not drop rapidly due to the presence of high fault current. If the test value is lower than the minimum recommended value due to contamination or excessive moisture, after eliminating the possibility of insulation defects, it can be cleaned and Dry measures improve the measurement results. The insulation resistance value can be used to monitor the effectiveness of the drying process. If the insulation resistance Ri1 value at 40°C is greater than 5000MΩ, then the polarization index value may not be specified and may not be considered. For shellac and asphalt-based insulation structures, an excessively high polarization index (such as greater than 8) indicates that the insulation may have been thermally aged and there is a risk of failure It will be very high. If the physical inspection (such as knocking on the insulation) finds that the insulation is dry and brittle, it is best not to clean the winding or conduct a voltage test. If the motor is put back into operation, it may malfunction at any time. 7.3 Trend analysis of insulation conditions If you can get the historical data of the motor insulation resistance (Ri1), comparing the current test results with the previous ones will help you understand the insulation status. However, comparative tests with similar conditions are very important, namely winding temperature, voltage range, test duration and relative humidity (see 6.1). At the same time, use the same test equipment as much as possible. To compare the test results at different winding temperatures, the results should be corrected to The same reference temperature (see 6.1.2). If Ri1 or PI drops sharply compared to the previous reading, it means that the surface is contaminated or damp. When the temperature increases (above 60℃), PI The value is low. In order to check the actual insulation condition, the second measurement should be performed above the dew point and below 40℃. 7.4 Comparison between different motors or different phases If the Ri1 of the entire winding is less than 5000MΩ, the significant difference in Ri1 or PI between the same motors may indicate surface contamination and moisture Or the insulation is damaged. In this case, it is advisable to find out the cause of the discrepancy. The characteristic polarization current IP in can cause significant changes in the insulation resistance values at 1 min and 10 min. If there is a significant change in the winding temperature between the insulation resistance at 1 min and 10 min, the value should be corrected Calculate the polarization index after reaching the reference temperature of 40°C. Table 4 Minimum recommended value of polarization index for high-voltage insulation structure The minimum recommended values in Table 4 do not apply to. ---Small motors with scattered windings, motors with uninsulated field windings, squirrel cage rotor windings and DC motor armatures (see section 5 chapter); --- The winding is connected to a motor with an end anti-corona layer that is in contact with the current (see Appendix B, B.6 and Appendix C, C.3); ---Ri1 value >5000MΩ winding (see 7.5).9 Test report9.1 Winding in operation The test report should provide at least test data and test conclusions. If it is used for trend analysis and comparison of insulation conditions, Result to be explained. The test report should include the following. a) Identification information. ---Factory Name; ---Motor number. b) Date of measurement. c) Environmental conditions. ---Ambient temperature; ---Winding temperature; ---Calculate relative temperature and ambient temperature of absolute humidity and dew point. d) Test equipment. ---Name, model; ---Manufacturer; ---serial number; ---The effective date of measurement. e) Test circuit, instrument settings and test conditions. ---Test voltage and polarity; ---Test duration (if required). f) Test the insulation characteristics under the measurement conditions and correct to the reference temperature. --Insulation resistance at -1min; --Insulation resistance at -10min (if applicable); ---Polarization index (if applicable); ---Temperature correction (if applicable). g) Draw measurement curve (if applicable). ---The relationship between the measured current and time, the logarithmic coordinate is better; ---The relationship between the measured insulation resistance and time, the logarithmic coordinate is better. h) Name of test personnel. i) Record specific information. j) Notes (such as differences from the standard test procedure, phenomena observed during the test, etc.). It is advisable to save all test results in the form of original data for future reference. According to the document type, independent testing and certification, or as part of the status assessment report, the report content can include corresponding additional information, such as Working mode, motor life, etc. 9.2 New winding For brand new windings, the insulation resistance test can be used as a supplement to the withstand voltage test, and the insulation resistance is carried out for 1 min before and after the withstand voltage test. test. Therefore, most of the information required by a complete test report will become part of the withstand voltage test protocol. Defined in 9.1 The required information may be sufficient.Appendix A(Informative appendix) Other DC tests A.1 Overview In the insulation resistance test and polarization index calculation described in this section, the winding is understood through DC voltage and DC cur......Tips & Frequently Asked Questions:Question 1: How long will the true-PDF of GB/T 20833.4-2021_English be delivered?Answer: Upon your order, we will start to translate GB/T 20833.4-2021_English as soon as possible, and keep you informed of the progress. The lead time is typically 2 ~ 4 working days. The lengthier the document the longer the lead time.Question 2: Can I share the purchased PDF of GB/T 20833.4-2021_English with my colleagues?Answer: Yes. The purchased PDF of GB/T 20833.4-2021_English will be deemed to be sold to your employer/organization who actually pays for it, including your colleagues and your employer's intranet.Question 3: Does the price include tax/VAT?Answer: Yes. 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