IEEE 400-2007 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 a description of the methods and practices to be used when field-testing laminateddielectric power cable systems. There is no requirement that any testing be performed either at the time ofinstallation or periodically thereafter. However, it is well known that direct current (dc) testing of laminateddielectric shielded power cables has been performed for many years, especially for new installations orafter repairs. If the user decides to have a direct voltage test made on the system, the following informationis intended to provide a guide to the methodology, voltages, and concerns to be considered during thetesting.
1.1 Scope
This guide presents the recommended practices and procedures for direct voltage acceptance andmaintenance testing of shielded, laminated dielectric insulated power cable systems rated 5 kV and aboveIt applies to all types of laminated power cable systems such as paper-insulated lead covered, pipe-typeand pressurized cables that are intended for the transmission or distribution of electric power. The tabulatedtest levels assume that the cable systems have an effectively grounded neutral system or a groundedmetallic shield.
1.2 Purpose
The purpose of this guide is to provide uniform practices and procedures for performing direct voltagcacceptance and maintenance tests on shielded, laminated power cable systems in the field and to provideguidelines for evaluation of the test results
2. Normative references
The following referenced documents are indispensable for the application of this document. For datedreferences, only the edition cited applies. For undated references, the latest edition of the referenceddocument (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 elevated temperatures. This necessitates areduction in the test voltages at higher temperatures. Temperature gradients in the cable insulation, causedby heat dissipation from the conductor, can result in abnormal voltage distribution upon application of ahigh direct voltage. For these reasons, high direct voltage tests should be made with the cable at ambienttemperature if possible.
3.12 Atmospheric conditions
High humidity and conditions favoring condensation on exposed surfaces can affect test results to a markeddegree. Contamination of termination surfaces can greatly increase conduction or leakage current andreduce flashover levels. Relative air density affects the measurement of a test voltage by use of rod gapsand 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 prescribedtest voltages. lf excessive corona or air discharges exist during a test, a reduced test voltage may result andhigh 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 electricalrields usually will have little influence on direct voltage test results as long as the voltage measurementcircuit is well shielded. A simple test to see the influence can be made by ungrounding the test system priorto energization and observing any indications on the test system instrumentation on the lowest meteringrange. It is always important to maintain adequate clearances for the dc test voltages anticipated also takinginto consideration the recommended clearance for the energized adjacent circuits.
IEEE 400-2007 pdf download
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