Modeling Humidity Impact on PDIV for Turn-to-Turn Insulation of Inverter-Fed Motors at Different Temperatures

Naderiallaf, H.; Ji, Y.; Giangrande, P.; Galea, M.

Abstract

This paper models the partial discharge inception voltage (PDIV) as a function of ambient humidity ( H ) at various temperatures ( Ts ) using Schumann’s streamer inception criterion (SCSIC) for turn-to-turn insulation, which is the most vulnerable part in inverter-fed motors’ insulation system. The Schumann constant (i.e., the natural logarithm of the critical electron number defining the Townsend-to-streamer discharge transition, K ) varies with H , showing distinct patterns at low and high Ts . The K equations are derived across a wide range of relative humidity (RH) levels (20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90%) at four Ts (25°C, 40°C, 60°C, and 90°C). These equations can be used in finite element analysis software to predict PDIV under varying H with outstanding accuracy. Additionally, a novel approach is presented for partial discharge (PD) phenomenology under H variations at different Ts using SCSIC-derived streamer inception parameters (SIPs): critical field line length (CFLL), air effective ionization coefficient (α eff ), partial discharge (PD) inception field ( E inc ) and firing voltage ( V firing ). Notably, at high Ts (e.g., 90°C), a transition phase emerges concerning RH, leading to significant SIP changes due to the disappearance of a critical region (CritR) in α eff at specific electric field intensities. The developed humidity-dependent PDIV model supports insulation designers in achieving PD-free designs that account for H variations and sheds light on SIPs variations concerning H changes.

• Journal Article Type: Article
• Acceptance Date: Nov 27, 2023
• Online Publication Date: Nov 30, 2023
• Publication Date: 2024-06
• Deposit Date: Dec 2, 2023
• Publicly Available Date: Dec 4, 2023
• Journal: IEEE Transactions on Dielectrics and Electrical Insulation
• Print ISSN: 1070-9878
• Electronic ISSN: 1558-4135
• Publisher: Institute of Electrical and Electronics Engineers
• Peer Reviewed: Peer Reviewed
• Volume: 31
• Issue: 3
• Pages: 1573-1582
• DOI: https://doi.org/10.1109/tdei.2023.3338138
• Keywords: Electrical and Electronic Engineering
• Public URL: https://nottingham-repository.worktribe.com/output/27872020
• Publisher URL: https://ieeexplore.ieee.org/document/10335747