GB798185A - Improvements relating to transformer tap-change systems - Google Patents

Abstract

798,185. Transformer arrangements. FERRANTI, Ltd. Jan. 27, 1956 [Oct. 30, 1954], No. 31409/54. Class 38 (4). A transformer tap-changing system for the parallel operation of a number of transformers includes a number of switches so associated with the taps on the transformers and so interconnected that when a tap change of one transformer has been completed, a tap change on the next transformer begins and when this is completed a tap change on the next transformer begins and so on until all the transformers have undergone a tap changing operation. Closure of a " raise " push-button 22 in a control unit 10 energizes a raise contactor winding 13 to operate a bank of mercury switches (not shown) which control the motor which drives the tap changing gear. Assuming the tapping position of the transformers from which a change is to take place to be an " even " numbered one, the even " switches 28, 35 will be closed and the odd " switches 25, 34 will be opened. Under such conditions the energizing circuit between the bus-bar 19 and neutral 20 is by way of switch 18, push-button 22, switch 37 in a control unit 24, " even " switch 35 in this unit and " even " switch 28 in the unit 10. The switches are self-maintaining so that when the tap change motor has begun to operate the pushbutton 22 can be released. Shortly after the motor has begun to rotate switch 17 is closed and switches 18, 37 opened. Towards the end of the tap-change operation on the transformer associated with the unit 10 the switch 36 therein closes and the " even " switch 35 opens whilst the " odd " switch 34 closes. The raise contactor winding 13 in the unit 33 now becomes energized and a tap-change operation is carried out on the transformer associated with that unit, the tap-change operations on the succeeding transformers being similarly controlled. If for some reason any control unit fails to respond an appropriate alarm device 32 will be energized. A device 32 will also give an indication of a short-circuit in the connections between its " odd " and " even " switches and those in a preceding control unit. The switch 37 in the last control unit 24 ensures that a further tap change cannot be initiated in the unit 10 until the unit 24 has completed its previous tap change. The lower contactor winding 12 is energized by means of pushbutton 21.