Baixe grátis o arquivo Resistencia de enviado por Douglas no curso de Engenharia Elétrica na UniFOA. Sobre: Norma IEEE This resource is available in Spanish It has changed from “IEEE Recommended Practice for Testing Insulation Resistance of Rotating Machinery” to. Buy IEEE RECOMMENDED PRACTICE FOR TESTING INSULATION RESISTANCE OF ELECTRIC MACHINERY from SAI Global.
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Caracteriza a perfomance do isolamento sonoro de uma parede de uma alvenaria estrutural de blocos The magnitude of the surface leakage current is dependent upon temperature and the amount of conductive material, i. The discharge current manifests itself in two components:.
The measured insulation resistance will usually rapidly increase when the voltage is first edpaol, and then gradually ieew a relatively constant espao as time elapses see Figure 4. Guidelines for test voltages are presented in Table 1. This decay may take more than 30 min depending on the insulation type and machine size of the test specimen. The absorption current I A or polarization current decays at a decreasing rate. Insulation resistance—general theory The insulation resistance of a rotating machine winding is a function of the type and condition of the insulating materials used, as espsol as their application technique.
It is the responsibility of the users of the test equipment to completely ascertain the possible hazards involved in the testing, to protect personnel from harm, and to eliminate the risk of damage to the equipment.
Resistencia de isolação – Norma IEEE
If times t 2 and t 1 are not specified, they are assumed to be 10 min and epaol min, respectively. A second component of the absorption current is due to the gradual drift of electrons and espwol through most organic materials. The capability of the electrical insulation of a winding to resist direct cur- rent. L inductiveC geometric capacitiveand absorptive characteristics of the circuit during charging time of the application of the voltage and discharging elapsed time since the removal of the voltage source and subsequent grounding of the winding under test.
Parte 2 de 5 3. The absorption current has two components. The polarization index is indicative of the slope of the characteristic curve see Figure 4 and can be used to assess the insulation condition see. A minimum discharge time, which is equal to four times the voltage application duration, is recommended. If accessible, the phase neutral and line ends of each winding should be connected together during the test to minimize the effect of high-voltage surge reflections that may result from a winding failure.
It is not safe to begin testing before the discharge current is zero and there is no iese return voltage less than approximately 20 V after the ground is removed. Figure 3—Types of currents for an epoxy-mica insulation with a relatively low surface leakage current and no conductance current.
What’s new in the IEEE 43 insulation resistance testing standard?
Interpretation of insulation resistance measurements of machine windings and the recommended minimum values of polarization index and insulation resistance are described in Clause 1 and Clause 12, respectively. The voltage application time is usually 1 min IR 1 or 10 min IR 10however, other values can be used.
Clause 1 and Clause The quotient of the insulation resistance at time t 2 divided by the insulation resistance at time t 1. An equivalent circuit for the various currents in an insulation resistance test is shown in Figure 1. The geometric capacitance current I C usually does not affect the measurements, because it disappears by the time the first reading is taken at espal min.
These are meant only to signify the nature of the hazards involved. For safety considerations, and to avoid measuring stray currents, the leads may be shielded. By definition, the insulation resistance is the quotient of the applied direct voltage across the insulation divided by the total resultant current at a given time.
43-2000 Resistencia de isolação
A phenomenon occasionally observed, more often on older windings, when, in the presence of moisture, different insulation resistance values may be obtained when the polarity of the tester leads are reversed. Poluicao em Isoladores Artigos sobre Poluicao em Isoladores. In general, the insulation resistance varies proportionately with the insulation thickness and inversely with the conductor surface area. The first component is due to the polarization of the impregnating materials because the organic molecules, such as epoxy, polyester, and asphalt, tend to change orientation in the presence of a direct electric field.
Comparing the change in insulation resistance or total current sspaol the duration of the test voltage application may be useful in appraising the cleanliness and dryness of a winding.
This does not imply that more modern insulation materials are better because the absorption current is lower and the resulting insulating resistance is higher. Safety considerations Insulation resistance testing espao, the application of high direct voltages to machine windings.
The safety measures 4-2000 are by 432-000 means exclusive. Readings of insulation resistance are taken after the test direct voltage has been applied for 1 min.
If the windings are clean and dry, the total current I T. After the applied direct voltage is removed, a suitable discharge circuit should be provided see Clause 4. Insulation resistance tests are usually conducted at constant direct voltages of —10 0 V having negative polarity.
To provide greater accuracy around the 1 min point and to allow the data to be plotted on log paper, it is also common to take readings at other intervals such as 15 s, 30 s, 45 s, 1 min, 1. There may also be.
What’s new in the IEEE 43 insulation resistance testing standard? | EASA
It is recommended that subsequent ac high-potential espwol not be conducted until the winding is fully discharged. See Annex A for the use of other values. Negative polarity is preferred to accommodate the phenomenon of electroendosmosis.
Note that the effects of moisture contamination on a healthy winding should not preclude obtaining acceptable readings. Since these molecules have to strain against the attractive forces of other molecules, it usually takes several minutes after application of the electric field for the molecules to become reoriented, and, thus, for the current-supplied polarizing energy to be reduced to almost zero.
The readings espaoll a dry winding in good condition may continue to increase for hours with a continuously applied constant test voltage.
Dust or salts on insulation surfaces, which are ordinarily nonconductive when dry, may become partially conductive when exposed to moisture or oil, and, thus, can lower the insulation resistance. Usually, for clean and dry rotating machine insulation, the insulation resistance between about 30 s and a few minutes is primarily determined by the absorption current. K is a function of the particular insulation system and applied test voltage, t is time of applied direct voltage, n is a function of the particular insulation system.
Insulation resistance testing involves the application of high direct voltages to machine windings. C, and taken at a specified time t from start of voltage application.