Manfred Mauntz

Abstract:

The online oil sensor system measures the components conductivity kappa, the relative permittivity epsilon r and the temperature T independently from each other. For insulation oils, the system calculates the loss factor tan delta with a very high precision. Changes in acidification, humidity, and break down voltage can be identified in real time. The new approach utilizes sensor detection of chemical aging of the insulating oil and its inhibitors. Based on a very sensitive measurement method with high accuracy, even small changes in the conductivity and dielectric constant of the transformer oil composition can be detected reliably. The new sensor system effectively controls the proper operation conditions of High Voltage Transformers, oil-filled circuit breakers, oil regeneration, and filtration systems. In wind turbine applications, the system enables damage prevention of the gearbox by an advanced warning time of critical operation conditions and an enhanced oil exchange interval realized by a precise measurement of the electrical conductivity, the relative permittivity, and the oil temperature. A new parameter, the WearSens® Index (WSi) is introduced. The mathematical model of the WSi combines all measured values and its gradients in one single parameter for a comprehensive monitoring to prevent wind turbines from damage. Furthermore, the WSi enables a long-term prognosis on the next oil change by 24/7 server data logging. Corrective procedures and/or maintenance can be carried out before actual damage occurs. Raw data and WSi results of wind turbine installations with different lubrication oils are shown. Short-term and long-term analysis of the data show significant trends and events, which are discussed more in detail. Once the oil condition monitoring sensor systems are installed on the high voltage transformer or a wind turbine's gearbox, the measured data can be displayed and evaluated elsewhere in sense of a full online condition monitoring system. 24/7 monitoring of the system (HV transformer or gearbox) during operation enables specific preventive and condition based maintenance independent of rigid inspection intervals.