Keep Testing Your Underground Power Cable

| In previous Items of Engineering Interest, we have    discussed testing of new underground cable. The Underground Subcommittee of the    NRECA’s T&D Engineering Committee highly recommends that electric utility    operators test underground cable they purchase. The Subcommittee recommends that the    following tests be conducted at a minimum.
- Dimensional analysis of all cable components;
- Microscopic examination for voids, contaminants and protrusions; and
- Insulation shield stripping test.

The Subcommittee also recommends that optional testing of    Tree-Retardant Cross-Linked Polyethylene and Cross-Linked Polyethylene insulated cables    include a Hot Oil Test. The Subcommittee does not recommend conductor shield and    insulation shield resistivity tests because they consistently test well below maximum    specifications.

Subcommittee recommended typical sampling rates are to test one sample,    each, from the first and last reel on orders of 50,000 feet (15 km) or less and one    sample for each additional 50,000 feet (15 km) of cable ordered.

The Subcommittee recommends that purchasers instruct manufacturers to    cut samples and send them to the selected testing laboratory, or the purchaser can cut the    samples upon arrival of the shipment. The Subcommittee further recommended that purchasers    notify suppliers in advance that cable testing will be conducted and purchasers should    establish responsibilities and procedures in case of a failure, such as: Any evidence of    noncompliance with the enclosed specifications shall be justification for:
- Further testing at manufacturer’s expense (each shipping reel);
- Rejection of the tested reel and possibly the reels preceding and following in the        manufacturing process; and
- Rejection of the entire order, depending on the severity and frequency of noncompliance.

A partial list of possible independent testing laboratories provided by    the Subcommittee includes:

Cable Technology Laboratories, Inc.    P.O. Box 708    690 Jersey Ave.    New Brunswick, NJ 08903    (201) 846-3220

Forster Electrical Engineering, Inc.    550 North Burr Oak Ave.    Oregon, WI 53575    (608) 835-9009

NEETRAC    62 Lake Mirror Road, Building 3    Forest Park, GA 30050    (800) 762-6522

All of these laboratories participate in the Cable Acceptance Testing    Program promoted by NRECA’s T&D Underground Subcommittee. The inclusion of a    laboratory in this list does not imply endorsement by RUS. The testing laboratories listed    above have voluntarily agreed to collect electric cooperative test data and provide it to    the NRECA Underground Subcommittee annually for information and publication. To have your    data included, note on your purchase order "INCLUDE IN COOPERATIVE DATA FILE."    Cooperative names will not be published and participation is voluntary.

If you would like more information or have any questions, please call    Trung Hiu, Electrical Engineer, Distribution Branch, at (202) 720-1877.
 

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