The Correlation and Balance of Material Properties for DC Cable Insulation at Design Field

Abstract

The innovation of materials with disruptive properties can be efficiently guided by improved physical understanding of material design principles. The design of a polymeric insulation depends on the desired requirements of the specific application, which, in the case of DC cable insulation, can be stated in terms of the following properties: controlled electrical conductivity, low space charge accumulation and high breakdown strength. Full characterization and detailed understanding of these properties as well as their correlation and balance may bring the ability to engineer needed dielectric properties for using as DC cable insulation. The aim of this paper is to identify the optimal DC insulation design space and to develop a formalism of the correlation between the conductivity and space charge, guided by a relatively simple model based on two physical parameters, activation energy (ξ) and mean trap separation (λ). With respect to implications for practical material design, the study demonstrates that a polymer material with activation energies in the range of 0.4 to 0.5 eV with relatively high trap density (N) (N= λ-3 , λ=1nm, N=1E+27 m-3) can be suitable for HVDC cable insulation. INDEX TERMS conductivity, material design, direct current (DC), crosslinked polyethylene (XLPE), space charge, cable insulation, thermal gradient.

Large improvement in DC electrical properties of EPDM with 2D platelet nanoclay

“…To improve acoustic impedance matching between the sample and the electrodes, a small amount of silicone oil was put between them. A semiconducting (SC) layer was used between the high voltage electrode and the coated sample to minimize the mismatch of acoustic impedance, while the coated specimen was placed directly on the grounding aluminum electrode [2,6].…”

“…Specimens of 200 µm in thickness were inserted in guarded stainless-steel electrodes for quasi steady-state current measurements by using a Keithley 6517 electrometer for 2000 s. The average reading of the conduction current between 1900 s and 2000 s was used to calculate the electrical conductivity. More details of the space charge and DC conductivity measurements can be found in the previous works [2,6].…”

“…in coal mine, electric power plant, as well as submarine, etc [1][2][3][4]. However, under high voltage direct current (HVDC), the desired characteristics for dielectrics are different and low space charge accumulation is preferred, along with other requirements of controlled electrical conductivity and high breakdown strength [5,6]. As such, EPR shall be properly formulated as a suitable candidate for HVDC cable insulation.…”

Heat Transfer Challenges for MVDC Power Cables Used in Wide Body All Electric Aircraft Under Low Pressures

“…where P is the pressure of the gas (Pa), T is the temperature of the gas (K), and R is the universal gas constant. Expressions ( 10), ( 13), (14), and (18) show that the temperature field and the velocity field of the air, which are significantly depending on the air density, are coupled. At the altitude of 12.2 km, which is a typical altitude of cruising aircraft, and a temperature of 15 • C, air pressure is 18.8 kPa and air density is 0.22 kg.m −3 compared to air density of 1.225 kg.m −3 at atmospheric pressure.…”

“…Also, space charge accumulation is caused by the conductivity gradient across the insulation which in turn depends on the temperature gradient. Space charge accumulation affects the electric field distribution and potentially causes dielectric degradation and failure [16], [17], [18]. Accumulation of the space charge in polymeric insulation materials will accelerate beyond their electric field threshold [19].…”