A Survey on Testing and Monitoring Methods for Stator Insulation Systems of Low-Voltage Induction Machines Focusing on Turn Insulation Problems

Abstract

Abstract-A breakdown of the electrical insulation system causes catastrophic failure of the electrical machine and brings large process downtime losses. To determine the conditions of the stator insulation system of motor drive systems, various testing and monitoring methods have been developed. This paper presents an in-depth literature review of testing and monitoring methods, categorizing them into online and offline methods, each of which is further grouped into specific areas according to their physical nature. The main focus of this paper is on testing and monitoring techniques that diagnose the condition of the turn-to-turn insulation of low-voltage machines, which is a rapidly expanding area for both research and product development efforts. In order to give a compact overview, the results are summarized in two tables. In addition to monitoring methods on turn-to-turn insulation, some of the most common methods to assess the stator's phase-to-ground and phase-to-phase insulation conditions are included in the tables as well.

Overview of condition monitoring and operation control of electric power conversion systems in direct-drive wind turbines under faults

“…When the temperature in the DD-WT exceeds a certain value, the DD-WT must be shut down for maintenance. At present, thermistors and thermocouples are used to monitor the temperature in the stator slot, base, and cooling system [30]. Determining the best installation location for the temperature sensors for improved monitoring effectiveness is the main challenge in this type of method.…”

“…Temperature signal analysis [25][26][27][28][29][30] Monitoring of inter-turn short-circuit fault and phase-to-ground insulation deterioration…”

Stator windings condition diagnosis of voltage inverter-fed induction motor in open and closed-loop control structures

“…According to [1], stator winding faults are one of the most common reasons of induction motor breakdowns and comprise about 36% of all failures. The stator winding damage begins with unnoticeable inter-turn short circuit, that eventually spread over the whole winding, causing main short circuit.…”

“…For that reason, other solutions, based on measurements and digital processing of diagnostic signals, are still looked for. They should allow on-line monitoring of the machine condition and alarm the user at the initial phase of the short circuit [1,3,4].…”

Estimation of temperature dependent equivalent circuit parameters for traction-based electric machines

“…The predominant applications for models in this field are in machine design [1,2], condition monitoring for diagnosis [3,4], ageing [5], modelling the machine temperature for cooling purposes [6,7], and for control systems [8].…”