IEEE Std ™ I. EEE Standards. TM. IEEE Guide for Field Testing of Shielded Power. Cable Systems Using Very Low. “IEEE Guide for Field Testing and Evaluation of the Insulation of Shielded Power IEEE “Guide for Testing of Shielded Power Cable Systems using Very. Guided IEEE Series (Bundle) Standards IEEE – • IEEE Guide for Field Testing of Shielded Power Cable Systems Using Very.
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The voltage can either be kept at this level or raised to the withstand level for 20 s to 50 s 2 cycles to 5 cycles where the PD activity is measured before being slowly reduced until the PD extinguish. There are risks associated with high-voltage testing and diagnostics.
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Log In Sign Up. Tangent delta measurements provide a global assessment of the dielectric loss. VLF-PD measurements are a diagnostic tool used to detect, in a nondestructive manner, the location and severity of an insulation defect. The measurement of the test voltage should be made with an approved measuring system, as described in IEC As a general rule the more severe the defects, the lower the ac dielectric strength.
Negative slope loss decreasing with Isolated loss regions such as lossy accessories or heavily water length treed regions within a large proportion of low loss cable 5. In Table 4 to Table 7, U0 is the cable phase to ground operating voltage. For an electrical tree from the tip of a needle in PE insulation in laboratory conditions to completely penetrate the insulation during the test duration, VLF ac voltage test levels and testing time durations have been established for the two most commonly used test voltage sources, the cosine-rectangular and the sinusoidal wave shapes.
Figure 1 —Recommended test hook-up 5. The test is intended to detect installation damage and to show any gross defects or errors in installation of other system components.
For new cable systems, the voltage sensitivity of the tangent delta, the differential tangent delta DTDis expected to be small, as should the temporal stability of tangent delta at constant voltage TDTS.
Refer to Annex H for discussion on determining the percentiles, the confidence limits and the limitations on these percentiles when the data sets are small. This guide addresses VLF ac voltage withstand and dielectric loss testing in the frequency range from 0. Frequencies lower than 0. Dielectric losses can be affected by insulation material parameters such as different materials and the cross-linking by-products, although in older cables the concentration of the latter will be negligible.
The VLF ac voltage test set is turned off to discharge the cable system and test set.
VLF cable testing – Wikiwand
A, and Hernandez-Mejia, J. During the test cycle the leakage current may be monitored and recorded if the necessary equipment is available.
Every detectable partial discharge generated during the testing time is recorded in a computer-based system by magnitude and location of its origin.
The safety practices shall include, but not be limited to, the following requirements: Insulation formed in layers typically from tapes of oeee cellulose paper or polypropylene or a combination of the iee. The tangent delta stability refers to iee variation of tangent delta ueee time at constant voltage.
The mechanisms for the increase or decrease in tangent delta are not fully understood at this time, but the greater the change in tangent delta the more severe is the insulation aging. For new cable systems, the differential tan delta DTD is expected to be small, i. Compliance with the provisions of any IEEE Standards document does not imply compliance to any applicable regulatory requirements.
It is recommended that test procedures be followed according to IEC where possible, to aid in consistency of results. Tables of test voltage levels are included for installation, acceptance, and maintenance tests on cable systems up to 69 kV.
In these cases, it is necessary to recognize the constraint of the Weibull approach in that it is designed to be applied to a single mode idee a time. The metallic shield of the cable to be tested is connected to system ground. Alternatively, the stability values can be calculated from tangent delta measurements taken at each voltage level and at the end of the minute withstand period. These data have been segregated for cable system type.
Tree-like pattern of electro-oxidation that can occur at stress enhancements such as ionic contaminants, protrusions, or voids in polymeric materials subjected to electrical stress and moisture. In these situations it would seem prudent to recognize the limitations in the data and weight the limit towards the data; in this case Furthermore, the viewpoint expressed at the time a standard is approved and issued is subject to change brought about through developments in the state of the art and comments received from users of the standard.
A comparison of results between different phases of the same segment or sequential section will help identify if this is the case.
The voltage should be set at 0. Essential Patent Claims may exist for which a Letter of Assurance has not been received. Diagnostic testing allows the determination of the relative amount of degradation of a cable system section and establishes, by comparison with figures of merit or accumulated data, whether a cable system section is likely to continue to perform properly in service.
The VLF ac voltage test set is turned off to discharge the cable and test set; the cable is then grounded.