Load Tap Changer (LTC) Condition Assessment

Major problems occur in Load Tap Changers, LTC's, when the contacts become coated with oxides and/or sulfides. This initial coating leads to increased contact resistance and buildup of carbon on the contacts. This "coking" leads to further increased contact resistance, increased contact heating and eventual thermal runaway. Fortunately this process can be detected at an early stage with DGA. Weidmann-ACTI measures both the gas levels and the ratio of heating to arcing gases. This data has been very successful in locating LTC faults. Oil quality assessment and particle count provide additional information about the oil and LTC.