IEEE 400.1-2007 pdf download IEEE Guide for Field Testing of Laminated Dielectric, Shielded Power Cable Systems Rated 5 kV and Above with High Direct Current Voltage
1. Overview This guide provides adescription ofthe methods and practices to be used when field-testing laminated dielectric power cable systems.There is no requirement that any testing be performed either at the time of installationorperiodically thereafterHowever it is well known that direct current (de) testing oflaminated dielectric shielded power cables has been performed for many years, especinlly for new installations or after repairs.ifthe user decides to have a direct voltage test made on the system, the following information is intended to provde a gunde to the methodology. voltages, and concens to be consdered during the testing.
1.1 Scope This quide presents the recommended practices and procedures for direct voltage acceptance and maintenance testing ofshielded, aminated dielectric insulated power cable systems rated 5 kV and above. It applies toalltypes oflaminated power cable systems such as paper-insulated lead covered, pipe-type. and pressurized cables that are inended for the transmssion or distribution of electric power. The tabulated test levels assume that the cable systems have an effectively grounded ncutral system or a grounded metallic shield
1.2 Purpose The purpose ofthis guide is to provide uiform practices and procedures for perfonning dircct voltage acceptance and maintenance tests onshieldedlaminated power cable svstems in the field and to provide guidelines for evaluation of the test results. 2.Normative references The follawing referenced documcnts are indispensable for the application of this document, For dated referencesonly the edition cied appies For undated relerences, the lalest edition of the refcrenced document (including any amendments or corrigenda)applics.
3. General
3.1 Environmental influences
3.1.1 Temperature
The dielectric strength of some cable insulations is reduced at elevated temperatures. This necessitates a reduction in the test voltages at higher temperatures. Temperature gradients in the cable insulation, caused by heat dissipation from the conductor, can result in abnormal voltage distribution upon application of a high direct voltage. For these reasons, high direct voltage tests should be made with the cable at ambient temperature if possible.
3.1.2 Atmospheric conditions High humidity and conditions favoring condensation on exposed surfaces can affect test results to a marked degree. Contamination of termination surfaces can greatly increase conduction or leakage current and reduce flashover levels. Relative air density affects the measurement of a test voltage by use of rod gaps and may also affect the flashover voltage of cable terminations. At elevations higher than 1000 m (3280 ft), additional insulation and clearance may be required to withstand both working voltages and the prescribed test voltages. If excessive corona or air discharges exist during a test, a reduced test voltage may result and high leakage current readings will be present. This factor can be compounded by high wind conditions.
3.1.3 Extraneous electric fields Although field tests on cable are often made in the vicinity of energized equipment, extraneous electrical fields usually will have little influence on direct voltage test results as long as the voltage measurement circuit is well shielded. A simple test to see the influence can be made by ungrounding the test system prior to energization and observing any indications on the test system instrumentation on the lowest metering range. It is always important to maintain adequate clearances for the dc test voltages anticipated also taking into consideration the recommended clearance for the energized adjacent circuits.
IEEE 400.1-2007 pdf download
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