Document: NRC Regulatory Guide
Document ID: 31f5b507-4290-458f-9233-049d79b5ff59
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:
hat the cable must be disconnected to perform the test and the high voltages involved during testing may damage the cable insulation. Recent research by the Electric Power Research Institute (EPRI) on medium-voltage cross-linked polyethylene (XLPE)- and ethylene propylene rubber (EPR)-insulated cables has shown that a dc HPT of field-aged cables could potentially damage or cause extruded cables, especially field-aged XLPE- insulated cable, to fail prematurely. Among the conclusions reached in the EPRI study are that dc HPTs of field-aged cables can reduce cable life, dc HPTs of field-aged cables generally increases water tree growth, and pre-energization dc HPTs of new medium-voltage cable does not significantly reduce in cable life. 2. Step Voltage Test (dc High Voltage) The step voltage test (SVT) is a diagnostic test that can be applied to low- and medium-voltage cable and all insulation and jacket material. The SVT is capable of detecting aging mechanisms such as thermally induced embrittlement and cracking, radiation-induced embrittlement and cracking, mechanical damage, water treeing, moisture intrusion, and surface contamination. The advantages of SVT are that it is relatively easy to perform, it provides trendable data on commonly used cable insulation materials, and it does not require access to the entire length of the cable. The disadvantages of SVT are that the cable must be disconnected to perform the test, and the high voltages involved during testing may damage the cable insulation. The potential problems with the dc HPT identified by the recent EPRI research study are also applicable to the SVT. 3. Illuminated Borescope The illuminated borescope (IB) inspection technique is a screening method that can be applied to inaccessible low-voltage cables, de-energized medium-voltage cables, and all types of cable insulation and jacket materials. The IB inspection technique is essentially an optically enhanced visual inspection using the IB tool to visually