Investigation of electrical treeing in cable grade crosslinked polyethylene (XLPE) insulations

Abstract

Using PC-based on-line monitoring system, extensive measurements were performed in insulation blocks cut from the crosslinked polyethylene (XLPE) insulation of 36, 69 and 132 kV rated cables produced in Saudi Arabia. A needle-plane electrode system was used with a needle radius of 10 m. The role of 'applied voltage step-time duration' and associated time resolved initiation and growth of different types of tree structures were evaluated. Results show that a step of 3 kV/10 min duration provides good comparison to evaluate service aged and new XLPE insulation of different voltage ratings. Velocity of propagation of electrical trees is fast at initiation, but declines exponentially to a constant rate within 20 s of its initiation. Fractal analysis of such trees was also carried out using different types of technical grade XLPE insulations. This paper presents discussion on these results and sheds light on the electrical treeing phenomenon.

Pechukas-Yukawa formalism for Landau-Zener transitions in the presence of external noise

“…It is especially convenient for AQC, taking λ to be an adiabatically evolving parameter. An extension of the formalism describes the dynamics of the quantum states of the system 11,17 through the evolution of C(t), a vector of the expansion coefficients of the quantum state over the orthonormal state of instantaneous eigenstates of the Hamiltonian. A wavefunction, expanded in the instantaneous eigenstates, is described by the following: |ψ = n C n (t)|n .…”

Considerable Different Frequency Dependence of Dynamic Tensile Modulus between Self-Heating (Joule Heat) and External Heating for Polymer–Nickel-Coated Carbon Fiber Composites

“…Judging from the different mechanical behaviors by self-heating and external heating as discussed above, the composites by Joule heat offers a caution that the horrors of low-frequency earthquake (0.1–2 Hz) must be taken into consideration for collapse of construction by PTC materials. The detailed mechanisms were analyzed in terms of crystal dispersions, thermal fluctuation-induced tunneling effect, , and electrical treeing. − …”