Patent GB-1282222-A (GB)
Title: Power regulation system
IPC: G21C7/36
Filed: 1970-01-19
Abstract: 1282222 Protective systems WESTING- HOUSE ELECTRIC CORP 19 Jan 1970 [13 Feb 1969] 2418/70 Heading H2K [Also in Divisions G3 and G6] A control system for the operating coils of the control rods of a nuclear reactor, wherein the coils are supplied from a three phase A.C. source through a rectifier which is controlled to maintain the coil current at a desired reference value (see Divisions G2-G3), is provided with protection circuits to raise an alarm in the event of: (1) Deviation of the coil current by more than a predetermined amount. As shown in Fig. 8, error detector circuits 201, 203, 205 receive respective error signals 212 from each control system for a group of coils, the error signal representing the deviation of the current from the reference value. When an error signal exceeds a preset value, a lamp 211 is lit and the signal is transmitted to light a lamp 216 in the control room and a lamp 217 which identifies the faulty power unit. The signal also controls a reference current generator 219 which causes the coil currents to be adjusted to prevent the rods being dropped. (2) Existance of the reference signal for more than a predetermined time. The signal is fed to an integrator supplying a level detector whose output is fed to a memory unit controlling an alarm lamp, Fig. 9 (not shown). The output of the memory unit is also passed to the OR gate 213 in Fig. 8. (3) Failure of the coil current to change to the new reference value (when this is altered) in a predetermined time. The error signal is applied to a saturable amplifier Fig. 11 (not shown) which always saturates when the reference signal changes. If this saturated condition lasts longer than a predetermined time the amplifier output which is passed to a bidirectional saturation detector supplying a constant signal to an integrator, causes the latter to actuate a level detector controlling a memory unit similar to that previously described for condition (2). (4) Loss of one of the phases of the supply. As shown in Fig. 13A, the output of the rectifier is applied to a ripple detector 270 whose signal is proportional to the amplitude of the ripple voltage and is applied to a level detector 274 through an AND gate 272. The latter ensures that the signal is only applied during periods when the ripple is normal, corresponding to the change of current from one value to another. Thus the second input to the gate 272 is obtained from the saturable amplifier 242<SP>1</SP> and saturation detector 244<SP>1</SP> previously described for condition (3). Loss of a phase alters the amplitude of the ripple voltage to cause actuation of a memory unit 276 similar to that previously described. To ensure reliability during periods of current decrease, a negative clipping circuit may be interposed between the rectifier output and the ripple detector. Fig. 13B (not shown), which circuit reduces the ripple signal produced under these conditions but does not affect the signal produced during periods of current increase. Typical waveforms produced by the rectifier are described, Fig. 12 (not shown) and their effect on the protection circuit is discussed.