IEEE 433-2009 en Recommended Practice for Insulation Testing of AC Electric Machinery with High Voltage at Very Low Frequency《高压甚低频大型旋转电机绝缘试验的推荐规程》.pdf
《IEEE 433-2009 en Recommended Practice for Insulation Testing of AC Electric Machinery with High Voltage at Very Low Frequency《高压甚低频大型旋转电机绝缘试验的推荐规程》.pdf》由会员分享,可在线阅读,更多相关《IEEE 433-2009 en Recommended Practice for Insulation Testing of AC Electric Machinery with High Voltage at Very Low Frequency《高压甚低频大型旋转电机绝缘试验的推荐规程》.pdf(30页珍藏版)》请在麦多课文档分享上搜索。
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3、g85g76g70g3g48g68g70g75g76g81g72g85g92g3g38g82g80g80g76g87g87g72g72g44g40g40g40g22g3g51g68g85g78g3g36g89g72g81g88g72g3g49g72g90g3g60g82g85g78g15g3g49g60g3g20g19g19g20g25g16g24g28g28g26g15g3g56g54g36g3g3g21g23g3g41g72g69g85g88g68g85g92g3g21g19g20g19g23g22g22g55g48IEEE Std 433-2009 (Revision of IEEE S
4、td 433-1974) IEEE Recommended Practice for Insulation Testing of AC Electric Machinery with High Voltage at Very Low Frequency Sponsor Electric Machinery Committee of the IEEE Power +1 978 750 8400. Permission to photocopy portions of any individual standard for educational classroom use can also be
5、 obtained through the Copyright Clearance Center. Introduction This introduction is not part of IEEE Std 433-2009, IEEE Recommended Practice for Insulation Testing of AC Electric Machinery with High Voltage at Very Low Frequency. Voltage withstand tests, particularly in the field, are generally carr
6、ied out with dc power sources, because in terms of weight, size, and cost they have a decided advantage. However the dc test data obtained on ac machines have a serious disadvantage in that the dc breakdown mechanism differs appreciably from that which occurs under ac conditions. In practice, it is
7、found that the dc breakdown strength is substantially higher than the ac breakdown strength. The dc breakdown process is principally an electronic conduction mechanism, with the free electrons injected into the insulation from either sharp points or the electrodes (where high field enhancement is cr
8、eated) or at space charge build-up sites within the dielectric. In contradistinction, the ac breakdown process involves a thermally controlled-type mechanism and results directly either from the thermal losses associated with the dielectric losses or from the partial discharge (PD) induced heating a
9、nd physical erosion mechanism at the sites where repeated discharges can take place. Both of these are frequency- and voltage-dependent effects; also note that the dissipation factor at a given insulation site is determined by the dielectric losses of both the solid insulation and the power loss con
10、tribution from the repetitive PD pulses. Evidently, it is more meaningful to evaluate the insulating systems of ac machines using ac voltage sources. For tests in the field, such ac voltage sources must be readily transportable, low weight, moderate size, and requiring lower amounts of power. This i
11、s accomplished by making use of low-frequency ac power supplies, which were first introduced in the 1950s for the purpose of high-potential testing and insulation resistance and capacitance measurements (see Bhimani B3, B4).aAlthough since that time, the low-frequency source equipment has undergone
12、substantial improvements, some uncertainties remain when it is attempted to relate the test data obtained at low frequencies to that at power frequencies. This becomes particularly apparent when one considers the dissipation factor and PD measurements at low frequencies with respect to those at the
13、power frequency. The dissipation factor may be expressed by the quotient, /, where represents the conductivity, represents the real permittivity (dielectric constant) of the dielectric, and is the frequency term. At power frequencies under constant ambient temperature, the conductivity is more or le
14、ss constant and governed by the conduction losses of free-charge carriers. Since is also relatively constant, then as the frequency is first decreased , the dissipation factor will exhibit an increase with falling frequency, . Once the falling frequency enters the space charge polarization region ov
15、er the lower frequencies, the conductivity will commence increasing, thereby further augmenting the value of the dissipation factor. As a consequence, the low-frequency value of the dissipation factor will be substantially higher than that at the power frequencies (see Engineering Dielectrics, Vol.
16、IIB, Electrical Properties of Solid Insulating Materials: Measurement Techniques B5). When diagnostic measurements are carried out in terms of the dissipation factor to determine the dielectric loss behavior of an insulating system, it must be borne in mind that the measured tan value is an indicato
17、r of the total loss in the insulating system. The PD contribution can be calculated in terms of the PD pulse-phase distribution at a given applied voltage and frequency or be measured using the pulse charge-voltage parallelogram technique (see Engineering Dielectrics, Vol. I, Corona Measurement and
18、Interpretation B6). The dielectric loss component in the solid insulation of the ac machine can then be determined by subtracting the dissipation factor value due to the PD loss from that resulting from that of the overall insulation system loss. a The numbers in brackets correspond to those of the
19、bibliography in Annex C. iv Copyright 2010 IEEE. All rights reserved. The PD intensity at power frequencies is substantially greater than at 0.1 Hz, because there are more discharges occurring per unit time, i.e., per 1 s, at 60 Hz. However, it is most remarkable that studies, which have been carrie
20、d out over an extended frequency range, indicate that as the frequency of the power source is reduced, the total PD pulse charge transfer per cycle is augmented as the number of PD pulses per cycle exhibits an increase with falling frequency (see Bartnikas and Morin B2 and Radu et al. B18. It is lik
21、ely that the observed behavior is due to the change in the rate of dielectric surface charging and discharging within the cavities. Nevertheless, the total PD energy dissipated over a 1 s period at the power frequency is appreciably higher than that at 0.1 Hz; if the ac breakdown strength at 60 Hz i
22、s a result of thermal instability and degradation caused by PDs, then it will be lower than that at 0.1 Hz, which in turn will be still lower than the dc breakdown strength. Notice to users Laws and regulations Users of these documents should consult all applicable laws and regulations. Compliance w
23、ith the provisions of this standard does not imply compliance to any applicable regulatory requirements. Implementers of the standard are responsible for observing or referring to the applicable regulatory requirements. IEEE does not, by the publication of its standards, intend to urge action that i
24、s not in compliance with applicable laws, and these documents may not be construed as doing so. Copyrights This document is copyrighted by the IEEE. It is made available for a wide variety of both public and private uses. These include both use, by reference, in laws and regulations, and use in priv
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