Abstract
Although synchronous generators are robust and long-lasting equipment of power plants, consistent electricity production depends on their health conditions. Static and dynamic eccentricity faults are among the prevalent faults that may have a costly effect. Although several methods have been proposed in the literature to detect static and dynamic eccentricity faults in salient pole synchronous generators (SPSGs), they are non-sensitive to a low degree of failure and require a predefined threshold to recognise the fault occurrence that may vary based on machine configuration. This article presents a detailed magnetic analysis of the SPSGs with static and dynamic eccentricity faults by focusing on the external magnetic field. The external magnetic field was measured using two search coils installed on the backside of the stator yoke. Also, advanced signal processing tools based on wavelet entropy were used to analyse the induced electromotive force (emf) in search coils to extract the fault index. The proposed index required no threshold to recognise the starting point of fault occurrence and was sensitive to a low degree of fault. It was also non-sensitive to load variation and noise that may induce a false alarm.
Highlights
Periodic evaluation of critical components of large synchronous generators provides a reliable condition monitoring system that prevents severe unexpected failure in power plants [1]
The complex configuration of the salient pole synchronous generator (SPSG) requires an accurate condition monitoring system to avoid an unplanned stoppage of the power plant
The mentioned signals in SPSG are robust to a low degree of fault; the only reliable source of fault detection is based on either the magnetic field in the air gap or external magnetic field
Summary
Periodic evaluation of critical components of large synchronous generators provides a reliable condition monitoring system that prevents severe unexpected failure in power plants [1]. The same approach based on the machine parameter was applied to SPSG It was shown in [13,14] that self‐inductance and mutual inductance of stator and rotor winding change under eccentricity fault. The air‐gap magnetic field is the most reliable source for fault detection regardless of fault type, it is an invasive approach It is not a practical approach for a generator under operation because sensors need to be installed at a standstill and cope with the environment in the air gap. The effectiveness of applying the external magnetic field to induction motors has been validated and explained in [22,23,24,25,26,27] for broken rotor bar, eccentricity, short circuit and bearing fault, respectively. To avoid additional computation complexity, the eddy effect is neglected, except for the damper winding, because a current
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