A safety device for the protection of the stability of turboalternators operating in parallel connection against excessive rotational speeds and runaways

摘要

782,704. Supply systems comprising a plurality of sources. LICENCIA TALALMANYOKAT ERTEKESITO VALLALAT. March 29, 1955 [March 29, 1954], No. 9090/55. Class 38 (4). A turbo alternator 1 operating in parallel with other sources connected to bus-bars R, S, T, is protected against instability by apparatus responsive to the load angle of the machine, i.e. the phase angle between the bus-bar voltage and the pole voltage of the machine, and which, upon the angle exceeding a limit value, operates contacts to give a warning, effect a regulation of fluid supply to the turbine, or shut the machine down. The apparatus may comprise a contact-making synchroscope 6, the windings of which are fed, respectively, by the bus-bar volts (over transformer 4) and by a reference voltage representative of the pole volts of machine 1. This latter voltage may be provided by a suitably phased auxiliary machine 2 driven with the machine 1, or by an auxiliary unloaded winding on the machine 1 or its exciter. The moving element of the synchroscope thus takes up a position corresponding to the load angle of the machine. Upon the limiting load angle being reached, the synchroscope closes contacts 9 to give a warning. If the angle increases sufficiently for the synscope to close contacts 10, synchronism has been lost, and these contacts cause closure of a switch 13 to energize from the machine 1, the rotor of a motor 7 for regulating the steam supply to the turbine and having a stator energized from the bus-bars. The motor rotates at a rate corresponding to the slip frequency. If this adjustment is inadequate to restore stability, the synchroscope rotates further and closes contacts 11 to operate quick shut-off means for the turbine. A regulating disc 14 may be driven by the motor to operate further control contacts. The synchroscope may be replaced by a slip ring induction motor 12.