IEEE 400.4-2015 pdf download
IEEE 400.4-2015 pdf download.IEEE Guide for Field Testing of Shielded Power Cable Systems Rated 5 kV and Above with Damped Alternating Current (DAC) Voltage.
The DAC attenuation depends on the quality factor of the total resonant circuit. The quality factor is inversely proportional to the losses of the circuit which includes the HV switch, the losses in the cable system. and the losses in the test set inductor.
Due to the symmetrical bipolar ac discharging process, no remaining charges will be introduced to the cable insulation during the oscillating phase.
As a result of the relatively low cable inductance and no occurrence of transient over-voltages due to reflections at joints and cable terminations, the DAC stress applied to the cable capacitance regarding PD inception represents the normal ac stress conditions. This means that the PD inception voltage (PDIV), the PD amplitudes, and the PD behavior are comparable to factory testing conditions, and the following references show that a DAC stress is similar for inhornogeneous insulation defects [B54], [B69], [B86j, [B87].
In the case of PD-free insulation, the application of DAC stress will have the similar effect as at factory testing conditions on the pass/fail outcome of the test [B54].
The DF can be estimated with the decay characteristics of the DAC wave, as shown in Houtepen. et al. [B34], IEEE Std 386TM [B44j, and described in Annex B.
The measurement of the test voltage should be made with an approved measuring system as described in IEEE Std 4 and 1EC 60060-3. The peak value of the test voltage should be measured with an overall uncertainty of ± 5%, and the response time of the measuring system should not be greater than 0.5 s.
6.3 DAC parameters
For a DAC test of a power cable circuit, a number of parameters that are related to the test circuit, the test procedure, the data acquisition and the data analysis have to he considered. The knowledge of these parameters is relevant for the definition of the test conditions and to provide proper evaluation of the test data as obtained for a particular test object. They are as follows:
Test circuit parameters: Depending on the type of DAC test circuit, the total test circuit can be described by a number of parameters. Annex C describes the parameters which are of importance to determine a specific configuration of the test circuit.
— Voltage parameters: Based on the selected test circuit, the type and voltage rating of the test object, as well as the test procedures to be applied and the basic parameters which can he used to characterize the DAC voltage are described in Annex C.
— Test parameters: Performing a DAC test in accordance with the recommended test parameters can be used to describe the test process (See Annex C).
— Evaluation parameters: Performing a DAC test provides a number of parameters that can be used to evaluate the test results. Depending on the type of test, for example withstand test, monitoring test or diagnostic test, these parameters can provide information about the test outcome (Annex C).
The DAC test parameters should be chosen in such a way so as to prevent or reduce the reduction of the service lifetime due to the field test. In the case of a withstand test, the impact on defective insulation needs to be high enough to cause a breakdown or to exceed a critical level of a monitored property but not so high as to cause degradation.
— Voltage level and the number of DAC excitations and the duration of the excitations are important and inseparable elements for the under-test and after-test performance of the cable circuit. The recommended test voltages and number of excitations for tests (Sec Annex A) are based on fieldexperiences obtained by different users of the DAC technology. Arbitrarily increasing voltage or extending the number of excitations from the recommended values could increase the probability of an early failure in service.
