Détecteur de surtension pour génératrice à courant alternatif

摘要

745,964. Running generators in parallel. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Jan. 5, 1954 [Jan. 9, 1953], No. 253/54. Class 38 (4). Means for detecting over-voltage, or overexcitation, of one generator in a system of alternating current generators 1, 2 operating in parallel, and more particularly means for effecting the tripping of the circuit-breaker 4, or 5, of the over-excited machine, comprises a relay 26 for each machine energized from_a line voltage transformer 29 over a circuit including a resistor 31 across which is developed a voltage proportional to the difference between the load currents of the machines, on account of the connection of this resistor across lines 21, 22 interconnecting current transformers 20 associated with each machine and in which flows a current proportional to the unbalanced wattless load currents. The phase of the voltage across resistor 31 is such as to assist the secondary voltage of transformer 29 in the case of an overexcited machine, whilst in the case of an underexcited machine, the two voltages are in opposition. Hence, excessive excitation of any machine, say due to failure of its automatic voltage control system, causes operation of its associated relay 26 and consequent disconnection of the machine, the relays associated with the machines remaining unoperated. Each machine may have an automatic voltage and load sharing control system comprising a carbon pile regulator 12 for an exciter machine 10, the pile being controlled by a winding 15 energized over rectifier 17 and transformer 18 so as to be responsive to the system voltage, a transformer 23 energized from the lines 21, 22 injecting into the rectifier circuit a voltage component proportional to the degree of load unbalance between the generators. In a modified arrangement, the resistor 31 is replaced by the primary winding of a transformer, the secondary winding of which is connected in one phase of a threephase bridge rectifier energizing the relay 26 and supplied in the same manner as rectifier 17.