The Dielectrics and Electrical Insulations Society Standards Committee

The aim of this recommended practice is to establish a protocol for the measurement of partial discharges using ac voltages and VHF/UHF electromagnetic sensors, for quality control during routine tests on factory and pre-molded joints of high-voltage direct-current (HVDC) extruded cable systems having voltage ratings up to 800 kV. The various steps of the protocol for the measurement of partial discharges in such cables are carefully described. Details are given about the procedure for a sensor performance check, test setup preparation, and success criteria. The ultimate goal of this recommended practice is not verifying the compliance with any maximum acceptable limit of partial discharge amplitude, but rather focusing on the whole phenomenon of partial discharges, in order to assess whether critical partial discharges are present in the tested object (either a factory joint or a pre-molded joint of a HVDC extruded cable system). “Critical partial discharge” is used here to mean a discharge within the insulation of the object under test, excluding all external discharges that can be present during the ac voltage test, (e.g., corona discharges due to HV electrodes, conducting leads related to the test setup).

The aim of this recommended practice is establishing a protocol for the measurement of space charges in high-voltage direct-current (HVDC) extruded cables having rated voltage up to 550 kV. Such measurements are prescribed to be carried out at the beginning and at the end of load cycle qualification tests (either the long-duration voltage test of prequalification tests or the load cycle test of type tests). The various steps of the protocol for the measurement of space charges in such cables are carefully described. Details are given about the procedure for applying and switching off the voltage, the preparation and conditioning of specimens, the measurement times during poling and depolarization, and the calculations for checking electric field stabilization. The ultimate goal of this recommended practice is not verifying the compliance with any maximum acceptable limit of either space charge or electric field, but rather assessing the variation of the electric field profile in the cable insulation wall during load cycle qualification tests.