Document: NRC Regulatory Guide
Document ID: 9547afbc-5a01-4bff-a41f-8300f5ba922b
Document Type: regulatory_guide
Title: Condition Monitoring Techniques for Electric Cables Used in Nuclear Power Plants
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1007/ML100760364.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.218
CFR Part: 
CFR Title: 

Content:
-dissipation factor technique are that it is relatively easy to perform, it provides trendable data on commonly used cable insulation materials, it does not require access to the entire cable, and the results can be correlated to known measures of cable condition. Disadvantages include that the end terminations of the cable must be disconnected to perform the test, the test is applicable to cables that have shielded or sheath construction because it requires a defined ground return path of the loss (leakage) current back to the test set (supply source), the test should not be performed on low-voltage (600 volt) and 5,000 volt unshielded cables because of safety concerns and unreliable test results resulting from an undefined ground return path, and the amount of capacitance in the cable circuit limits the test such that standard test equipment cannot test very long and larger conductor cables. 7. Insulation Resistance/Polarization Index The insulation resistance/polarization index test is a diagnostic test that is relatively effective with low- and medium-voltage cables and all insulation and jacket materials. The insulation resistance test is a standard test used to measure the dielectric integrity of cable insulation; because of its sensitivity to temperature and humidity, it frequently is used as a pass/fail test because of the difficulties in obtaining an accurate and consistent absolute insulation resistance measurement. The polarization index test, which is the ratio of the insulation resistance measured at 10 minutes to the insulation resistance measured at DG-1240, Page 7 1 minute, successfully detects aging mechanisms such as thermally induced cracking and radiation- induced cracking in the presence of moisture, moisture intrusion, and surface contamination. Advantages of the test are that it is relatively easy to perform, it does not require access to the entire cable, it does not need to be corrected for temperature effects, and it can provide trendable