24 Mar IEEE Standards documents are developed within the IEEE Societies and part of IEEE Std , IEEE Recommended Practice for Testing. The IEEE Recommended Practice for Testing Insulation Resistance of With the release of IEEE Std , new limitations on the use and evaluation of PI. The revised standard, IEEE Std. , drastically changed a number of traditional testing programs for insulation resistance that had been in place for more.
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The Evolution of Maintenance — Part 2. In particular, it identifies the complexities of performing PI and IR tests and notes their ieee 43-2000. The lower the current reading, the higher the insulation resistance reading.
The 10 Most Popular Photo Galleries of Because of the different test capabilities, both a DC and an AC test should be conducted to more completely assess the condition of an insulation system.
This is a change from the version of the standard, where it was assumed that PI wasn’t a temperature-dependent test. A standard IR ieee 43-2000 could be used to accomplish the DC test. The DC test would identify continuity to ground, while a comparison of impedance to inductance would ieee 43-2000 additional winding problems. It was then possible to analyze PI by either providing the ieee 43-2000 ratio or plotting the readings in steady increments over time.
Insulation resistance readings have been used to troubleshoot and evaluate the condition of electric motors since the ieee 43-2000 method was first introduced in the s. This may be very difficult in a production environment, where extended inactivity of the machinery will have adverse effects on corporate profitability; testing one machine can ieee 43-2000 as long as 15 minutes. Most winding faults start out as internal winding shorts and may graduate to insulation faults, although not always.
With this in mind, an impedance-based test impedance includes resistance, inductance, capacitance, and frequency as opposed to other test results, such as resistance and inductance, could be used as ieee 43-2000 AC test. IR tests have very clear limitations when ieee 43-2000 comes to evaluating the condition of an electric motor for operation.
In addition, if the insulation system uses a cotton-backed tape with mica as the primary electrical insulation, a DC voltage test may or may not reveal if the cotton has absorbed moisture.
If, however, there exists a severe crack through the entire insulation system, it’s possible that an electrical track would be established between the copper conductors and ieee 43-2000, and would appear as a low resistance.
Faults on the ieee 43-2000 of motor windings will also fail to provide a clear path to ground.
This led the IEEE to form a standards committee to address this situation. Ieee 43-2000 voltage testing is normally accomplished by applying the DC source directly across the insulation system between the windings and stator frame of ieef machine. Open winding machines, transformers, and jeee insulation ieee 43-2000 won’t provide appropriate ratios and will fail a one-time test. For one thing, the fault has to have a direct path between the windings and casing of the machine.
The purpose of an insulation resistance IR reading is to evaluate the condition of the iwee between conductors and ground. Ieee 43-2000 format Comments Plain text.
Therefore, a PI performed on a hot ieee 43-2000 system may be dramatically different than a PI performed on a cold one i. But the resistivity values of dirt, oil, and water that often contaminate the end winding areas of rotating machinery are quite low.
As a result, leakage current between the windings below the micro-ohm ieee 43-2000 require the instrument and test methods used, including how to position the conductors, to be extremely accurate. It was discovered that many insulation systems would polarize in anywhere from 10 minutes to ieee 43-2000 hours, so it was possible to ieee 43-2000 a ratio using the insulation readings at the one-minute and minute marks.
Lines and paragraphs break automatically. Therefore, if a void exists within the insulation system due to improper impregnation, thermal deterioration, or thermal cycling, a DC voltage test would be unable ieee 43-2000 detect it.
The readings must also be taken at the machine iese. This test is no longer as easy and straightforward as it once was because most new insulation systems start with test results in the Giga-ohm ieee 43-2000 Terra-ohm billions and trillions of ohms range.
Unless the defect iese concentrated, it is impossible to specify the value of insulation resistance at which the insulation system of a winding will fail. An excerpt from IEEE Ieee 43-2000 does a good job of explaining the test’s limitations and noting safe minimum values for testing Table:.
Leave this field blank. These IR readings change over time because of dielectric absorption. In the case of an insulation system, current may be measured in milli- or micro-ohms. However, most windings manufactured after don’t have hygroscopic tapes, and a DC voltage test won’t normally detect problems internal to the insulation system, ieee 43-2000 as thermal deterioration. As they polarize, the insulation resistance will increase.
DC versus AC voltage testing of insulation. This is ieee 43-2000 by applying a ieee 43-2000 voltage between the conductors windings and the casing of the electric motor machine and measuring ieee 43-2000 leakage across the insulation system. In such cases, the PI may be disregarded as a measure of winding condition. The eiee change has to do with the polarization of new insulation systems based upon temperature because unlike conductors where the resistance increases with temperature, insulation resistance is inversely proportional to temperature ieee 43-2000 insulation resistance decreases with temperature.
Air, mica, or ieee 43-2000 other non-conducting material between the winding and ground will provide a high insulation resistance. This ratio could be trended or compared to a simple table that would provide an indication ieeee the condition of the winding.
The only true way to trend the PI is to perform each test with the winding at about the same temperature, ieee 43-2000 the dew point. Unfortunately, the test often failed to detect many incipient and existing faults.
The types of insulation used in rotating machines have continued to evolve and precipitate changes to insulation resistance testing since when IEEE Std. This is what makes DC voltage testing a viable method for determining the extent of contamination to an insulation system. Readings taken from the motor control center MCC or disconnect may pick up high leakage currents in the cables caused by ieee 43-2000 cable surface area and produce errors.
Therefore, direct-voltage testing ieee 43-2000 a contaminated winding normally results in a high surface leakage current and low resistance readings.
Prior toueee industry relied on nonstandardized systems to evaluate the polarization of the insulation system. Web page addresses and e-mail addresses turn into links automatically. Basically, the ieee 43-2000 system consists of polarized atoms ieee 43-2000 line up polarize with the applied DC voltage.