Patent Number: 047479949
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention is illustrated in FIG. 1 which utilizes a switchgear mechanism 10 as a reactor trip breaker RTB. The switchgear mechanism 10 receives power from an AC power bus 12 in a reactor control system and supplies power to a rod positioner 14 which controls the position of control rods in a pressurized light water nuclear reactor. The switchgear 10 can be a conventional switchgear mechanism, such as Westinghouse Part No. DS206 or DS4l6. Such a switchgear mechanism 10 conventionally includes an undervoltage trip coil 16 which is de-energized while the shunt trip coil 18 is energized, when an undesirable condition is detected in the nuclear reactor. According to the present invention, the shunt trip coil 18 in the switchgear 10 is provided power via a potential transformer 20, such as a Westinghouse type PXA, style No. 592A78lG0A, and a rectifier 22 which may comprise diodes 28, each diode may be a 1N3990, available from Westinghouse Electric Corporation. The shunt trip coil 18 is energized by activation of either a manual trip switch 24 or an automatic trip switch 26 connected to an automatic protection system. Since the potential transformer 20 is supplied with power by the switchgear 10, when the shunt trip coil 18 is energized to interrupt the supply of power to the rod positioner 14, the supply of power to the potential transformer 20 is also interrupted, thereby de-energizing the shunt trip coil 18. The rectifier 22 outputs a DC voltage which can be monitored to determine the ability of the trip coil control system to activate the shunt trip coil 18 and the condition of the power supplied to the rod positioner 14. The DC voltage will have a ripple, as illustrated in FIG. 1, if just three diodes 28 are used in the rectifier 22. One embodiment of the present invention includes a power monitoring device 30 to monitor the DC voltage output by the rectifier 22. The power monitoring device 30 comprises a voltage/optical converter 32, such as a Hewlett-Packard # HFBR-1201, which provides isolation between the trip coil control system and monitoring devices in the reactor control system. The voltage/optical converter 32 outputs a light signal which can be tranmitted over an optical cable 34, such as a Hewlett-Packard # HFBR-300. The light signal generated by a simple voltage/optical converter 32 is sufficient to transmit information regarding whether the rectifier 22 is outputting a DC voltage and further provides an indication regarding the condition of the power supply to the rod positioner 14, such as missing phases in the AC power. If additional information, such as voltage level, is desired, an analog/digital converter 36 can be added to the monitoring device 30. The monitoring device 30 may also include additional components at a remote distance from the switchgear 10. Such components are illustrated in FIG. 2 as receiving the light signal via the optical cable 34. An optical/voltage converter 40, such as a Hewlett-Packard # HFBR-2201, converts the light signal back into a DC voltage which is supplied to a microprocessor board 42, such as an Intel 88/40. The microprocessor board 42 includes a signal conditioner 44, microprocessor 46 and an output interface 48 for interfacing with other devices 50 in the reactor control system. Each reactor trip breaker 10 in a conventional reactor control system may be connected to several signal processing units such as the microprocessor board 42 illustrated in FIG. 2. With the addition of more voltage optical voltage/converters 32 to receive the output of the rectifier 22, several microprocessor boards 42 can be connected to monitor a single reactor trip breaker 10. The many features and advantages of the present invention are apparent from the detailed specification, and thus it is intended by the appended claims to cover all such features and advantages of the control system which fall within the true spirit and scope of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope and spirit of the invention.