Based on Low Flux Test to Predict Stator Core High Flux Test Temperature Rise Caused by Lamination Short-Circuit Fault
Abstract
Insulation failure between stator core laminations in large generators often results in catastrophic damage. While the electromagnetic core imperfection detection (ELCID) test is the most widely adopted diagnostic method with low power demand, it sometimes provides false alarm. These inaccuracies frequently necessitate supplementary high flux tests (mega volt ampere (MVA)-level power supplies, 1 MVA $= 1~\times ~10 ^{6}$ VA) to verify temperature rise at fault locations, leading to significant costs in maintenance. A novel method is proposed in this article to predict the temperature rise result of high flux tests based on the results of ELCID. First, a method to calculate the length and width of fault loops is proposed. The effect of the length of fault loop on the ELCID results is analyzed. Second, the fault loop power factor is calculated based on the phasor diagram analysis of ELCID. Based on these detailed parameters of fault loop obtained from ELCID test, the temperature rise under high flux testing of this fault loop can be predicted. The accuracy of the proposed algorithms was validated through finite element method (FEM) simulations and experimental tests on core models. This approach provides engineers with comprehensive fault loop parameters and accurate temperature rise predictions. By offering a reliable criterion for whether a high flux test is truly necessary, this method effectively mitigates the inherent limitations of ELCID, broadens its diagnostic scope, and decreases the costs of operation and maintenance substantially.