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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This test is no longer as easy and straightforward as it once was because most new insulation systems start with test results ieee 43-2000 the Giga-ohm and Terra-ohm billions and trillions of ieee 43-2000 range.
Therefore, 43-000 PI performed on a hot insulation system may be dramatically different than a PI performed on a cold one i.
Air, mica, or any ieee 43-2000 non-conducting material between the winding and ground will provide a high insulation resistance.
The purpose of an insulation resistance IR reading is to evaluate the condition of the insulation between conductors and ground. In such cases, the PI may ieee 43-2000 disregarded as a measure of winding condition. IR tests have very clear limitations when it comes to evaluating the condition of an electric motor for operation. This is a change from the version of the standard, where it was assumed that PI wasn’t a temperature-dependent test.
These IR readings change over time because of dielectric absorption. Ieee 43-2000 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 take as long ieee 43-2000 15 minutes. Therefore, direct-voltage testing of a contaminated winding normally results in a high surface leakage current and low resistance readings.
Lines and paragraphs break automatically. Basically, the insulation system consists of polarized ieee 43-2000 that line up polarize with the applied DC voltage. Web page addresses and e-mail addresses turn into links automatically.
ieee 43-2000 This is what makes DC voltage testing a viable method for determining the extent of contamination to an ieee 43-2000 system. This led ieee 43-2000 IEEE to form a standards committee to address this situation. Faults on the end-turns of motor windings will also fail ieee 43-2000 provide a clear ieew to ground. 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, such as thermal deterioration.
If you take the inductance across three phases of a 3-phase machine and compare it to the impedance, changes to capacitance in one or more phases would have oeee negative effect on the impedance, causing the value to fall toward inductance.
The 10 Most Popular Photo Galleries of The Evolution of Maintenance — Part 2. It also notes an acceptable alternative: It was discovered that many insulation systems would polarize in anywhere from 10 minutes to several ieee 43-2000, so it ieee 43-2000 possible to produce a ieee 43-2000 using the insulation readings at the one-minute and minute marks.
As a result, leakage current between the windings below the micro-ohm range require the instrument and test methods used, including how to position ieee 43-2000 conductors, to be extremely accurate. For one thing, the fault has to have a direct path between the windings and casing of the machine. But the resistivity values of dirt, oil, and water that often contaminate the end winding areas of rotating machinery are quite low.
A Review of Polarization Index and IEEE Std. 43-2000
The only true way to trend the PI ieee 43-2000 to perform each test with the winding at about the same temperature, over the dew point. In particular, it identifies the complexities ieee 43-2000 performing PI and IR tests and notes their limitations.
More information about text formats. Leave this ieee 43-2000 blank. A standard IR test could be used to accomplish the DC test. Most winding faults start out as internal winding shorts and may graduate to insulation faults, although not always. The types of insulation used in rotating machines have continued to evolve and precipitate changes to insulation resistance testing since when IEEE Std.
In the past, a PI ratio of less than 2. Unfortunately, the test often failed to detect many incipient and existing faults. In the case of an insulation system, current may be measured in milli- or micro-ohms. An excerpt from IEEE Std does a good job of ieee 43-2000 the test’s limitations and noting safe minimum ieee 43-2000 for testing Table:.
In addition, PI can only be used on form wound or ieee 43-2000 wound machines. A poor reading would indicate that additional testing was necessary.
DC versus AC voltage testing of insulation.