Partial discharge measurement in transmission-class cable terminations

Abstract

This paper describes on-line and off-line partial discharge (PO) measuring techniques applicable to transmission cable terminations. The on-line technique can be utilized for both extruded and pipe-type cable terminations. In pipe-type cable terminations, the on-line technique is only applicable to newly installed terminations, as it requires an internal inductive sensor. In the case of extruded cable terminations, on-line testing is made possible by using an external inductive coupler around the ground connection at the base of termination.Off-line PD measurements utilize high-frequency capacitive couplers. The coupler is attached to the overhead line within 4-feet from the termination under test. The off-line testing is applicable to new and existing cable terminations. I: IntroductionTransmission-class cable terminations are classified in two groups depending on the type of cables that terminated to namely, extruded-dielectric cable terminations and pipe-type cable terminations. Terminations are required where cables are connected to overhead lines or electrical apparatus. Terminations are designed to possess the same integrity as their associated cables. Cable terminations are designed to eliminate stress concentration resulting from the ending of cable insulation and shield. The utilization of a stress cone effectively separates the shield away from the insulation surface and distributes the stress. All cable terminations, independently of operation voltage utilize a stress control cone. However, for sub-transmission and transmission type terminations, 60 kV and up, in addition to a stress cone, a secondary stress relief control unit is necessary to distribute dielectric stress over the length of the porcelain insulator. A porcelain stress control unit is utilized in conventional, nongraded type terminations for 69 to 161 kV. This cannot be utilized in higher voltage due to excessive internal diameter requirements. In these cases capacitance graded termination are used. These can be coaxial type and doughnut type. The former consists -of a series of cylindrical electrodes coaxial to the cable formed by intercalating aluminum foils between the paper layers, while the latter consist of a stack of toroidal capacitors connected in parallel. 0-7803-5515-6/99/$10.00 0 1999 IEEE 2 Terminations are the second weakest component in underground transmission cables, cable splices are the weakest cable component. Cable terminations normally failed as the result of aging or improper installations. Failure of terminations, results in chattering of the porcelain insulator with pieces scattered over a wide area in addition to fluid leaks. All high voltage terminations are filled with dielectric fluids with the exception of SF6 indoor terminations and terminations in HPGF cables.Condition assessment of terminations is a difficult task.Since all transmission type terminations contain a dielectric fluid, sampling of this fluid for dissolved gas analysis presents an effective approach to termination diagnosis. However, only HPFF...

Partial Discharge Measurement for Cable Terminators of XLPE Power Cable

“…The voltage levels are 12 kV and 24 kV. The dielectric losses of cable are not presented in this section, but they are calculated by using Equation (1). Obviously, it can be noticed that the dielectric loss depends on rated voltage and material inside the tube (power cable).…”

“…Most solid insulations are developed from polymeric materials. There are two important electrical characteristics for polymeric insulations, which are the partial discharge level and the dielectric loss (tan 6) [1,2]. It is necessary for cable manufacturers to perform tests on the partial discharge level as well as on the dielectric loss.…”

“…It is necessary for cable manufacturers to perform tests on the partial discharge level as well as on the dielectric loss. In order to perform such tests, a cable connector is required [1]. The cable connector is available in the commercial sectors.…”

Partial discharge and noise separation in combined cable–OHLs based on three‐phase power ratios

“…High-frequency current transformers (HFCTs) have great advantages in this situation. PDs can be detected at cable joints and terminations using removable or permanent HFCTs without de-energising the power transmission network [4,5]. The HFCTs are usually clamped around the crossbonding wires or earth bonding wires of the cable.…”