IEEE 400.1-2007 pdf free.IEEE Guide for Field Testing of Laminated Dielectric, Shielded Power Cable Systems Rated 5 kV and Above with High Direct Current Voltage.
This guide presents the recommended practices and procedures for direct voltage acceptance and maintenance testing of shielded, laminated dielectric insulated power cable systems rated 5 kV and above. It applies to all types of laminated power cable systems such as paper-insulated lead covered, pipe-type, and pressurized cables that are intended for the transmission or distribution of electric power. The tabulated test levels assume that the cable systems have an effectively grounded neutral system or a grounded metallic shield.
1.2 Purpose
The purpose of this guide is to provide uniform practices and procedures for performing direct voltage acceptance and maintenance tests on shielded, laminated power cable systems in the field and to provide guidelines for evaluation of the test results.
2. Normative references
The following referenced documents are indispensable for the application of this document. For dated references. only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments or corrigenda) applies.
3. General
3.1 Environmental influences
3.1.1 Temperature
The dielectric strength of some cable insulations is reduced at elcvatcd temperatures. This ncccssitates 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 afkct test results to a marked degree. Contamination of termination surfaces can greatly increase conduction or leakage current and reduce fiashover levels. Relative air density aflcts 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 (32S0 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 tields 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 ungroLinding 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 pdf free download.