Technical state control of on-load tap changing transformer of ultra high power electric arc furnace

The article deals with technical characteristics of “TAMINI” FTOHBR-150200/35 transformers installed at the 180 t electric arc furnaces (EAF-180) of the electric steelmaking shop of “Magnitogorsk metallurgical Plant” OJSC. The authors analyzed the design and arrangement of the transformer on-load tap changer (OLTC) and the reactor providing secondary voltage control. The main features of OLTC modes were noted, such as a great number of switchovers (up to 1000 times per day), current and voltage surges at switching. The research group proved that it is necessary to develop and implement the systems of technical state monitoring for furnace transformer OLTCs. The researchers introduced the functional block diagram and description of TDMS diagnostic system implemented at EAF № 1 and EAF № 2 of the electric steelmaking shop. Brief characteristics of the OLTC diagnostic parameters sensor and TAP-Monitor logger installed in the developed monitoring systems were listed in the article. The authors carried out the analysis of online control methods of the OLTC technical state implemented in TDMS system: switchover number control, control of moving parts technical state, technical state vibration monitoring method. Time diagrams of control parameter changes and switching averages are also given in the article. It was concluded that it is necessary to make a rational choice of meaningful diagnostic parameters and consequently optimal number of input signals of the technical state monitoring system.