Abstract
Due to necessity of enforcing the electrical transmission network, a long distance gas insulated transmission line (GIL) has been developed as a new alternative underground technology, and has shown an ever-increasing usage worldwide. The main failure modes of the GIL are performance degradation due to air leakage, and random shocks caused by partial discharge. The failure of the GIL subject to both soft failure and hard failure is the result of their competition. Considering that the degradation occurs only after a certain delay, i.e. there is a random degradation initiation time before the air in the GIL begins to leak, this paper presents a new reliability model for the GIL subject to competing failure modes. Its reliability is assessed through analytical derivation and numerical calculation methods. And a numerical study is conducted to illustrate the implementation of the proposed model.
Highlights
To meet the necessity of enforcing the electrical transmission network, and considering that erecting new overhead lines may encounter many insurmountable difficulties for some specific environment and terrain, a new alternative underground technology is developed as a long distance gas insulated transmission line (GIL) [1]
Besides hard failure caused by partial discharge, soft failure caused by air leakage can be found in many applications, e.g., Jinping-I Hydropower Station in China
Considering the competing failure modes of the GIL, i.e., hard failure due to partial discharge and soft failure caused by air leakage, this paper proposes a new reliability model with random degradation initiation time before the air in GIL begins to leak
Summary
To meet the necessity of enforcing the electrical transmission network, and considering that erecting new overhead lines may encounter many insurmountable difficulties for some specific environment and terrain, a new alternative underground technology is developed as a long distance GIL [1]. Based on practical failure analysis in [7], it can be indicated that the defect of the sealing ring will not cause air leakage as soon as the GIL is put into service. Considering the competing failure modes of the GIL, i.e., hard failure due to partial discharge and soft failure caused by air leakage, this paper proposes a new reliability model with random degradation initiation time before the air in GIL begins to leak. A nonlinear general path model is developed to model the aging of the GIL sealing rings, which is assumed to be the primary cause of air leakage. A competing failure model is proposed to assess the reliability of GIL system.
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