Patent Application
20070133724
This invention relates generally to electrical power systems, and more specifically to methods and apparatus for time synchronization of devices within electrical powers systems.
At least some known electrical power systems are spread over geographical areas spanning from power generation stations, through voltage transmission facilities, to voltage distribution networks and electrical loads. Components of such electrical power systems may be monitored, for example, to protect assets, for example disconnecting an asset in case of an internal failure or operating conditions that may jeopardize the asset, may be monitored for overall system protection, for example disconnecting loads and/or generators to protect an integrity of the electrical power system, and/or may be monitored for general control of the electrical power system, for example adjusting operating parameters and/or conditions of the system. Furthermore, components of such known electrical power systems may be monitored to record operating parameters and/or conditions of the system, for example to generate a time record of system parameters for post-mortem analysis, and/or may be monitored for metering, for example measuring parameters and/or operating conditions of the system for operation and/or revenue. Moreover, components of such known electrical power systems may be monitored to measure, store, and/or alarm with respect to operating parameters and/or conditions of the system.
Devices used to monitor known electrical power systems may include a processor, and are sometimes referred to as Intelligent Electronic Devices (IEDs). However, to facilitate monitoring of the electrical power system, at least some known IEDs may need to be synchronized with respect to time. One known level of synchronization is wherein one or more devices act as a master for other devices to synchronize to. More specifically, devices are not synchronized to a universal external time base. Another level of synchronization is an explicit time synchronization of a number of devices to a common time reference, for example Corrected Universal Time (UTC). A universal external time base may be used across geographically distributed areas, for example between devices in the same substation or facility, between various substations of a given electric utility, between utilities, and/or between power system interconnections.
At least one known method of time synchronization includes using an internal clock in each device that is manually synchronized every few days or so. However, some known internal clocks that are synchronized every few days or so may be less accurate than is sometimes desired because of limited synchronization accuracy and/or drift of the internal clock between two consecutive synchronization instances. For example, some known internal clocks may only provide time synchronization at the level of a few seconds or minutes. At least some known voltage level may require more precise synchronization than the level of a few seconds or minutes. For example, synchronization error below about ten microseconds is sometimes desired for some known voltage levels. Synchronization error below about ten microseconds is sometimes achieved by synchronizing an internal clock of each device with an external time signal received from an external time generator, for example a Global Positioning System (GPS)—driven clock. The time signals are sometimes distributed to the devices using metallic and/or fiber-optic distribution networks. However, such a synchronization method may require at least one time generator per facility as well as other infrastructure, for example amplifiers, signal converters, signal repeaters, and/or wiring, to distribute the timing signals to each device, thereby possibly increasing a cost and/or decreasing a reliability of the time synchronization system.
In one aspect, a method is provided for distributing a timing signal to a device. The method includes receiving a timing signal from a timing source, receiving a power signal, superimposing the timing signal on the power signal to facilitate creating a different power signal to be distributed to the device, decoding the timing signal from the power signal within the device, and adjusting an internal clock of the device to facilitate synchronizing the internal clock with the decoded timing signal.
In another aspect, a method is provided for receiving timing information from at least one of a radio source and a satellite source with a device. The method includes receiving an electromagnetic wave signal that includes the timing information, decoding the timing information from the received signal within the device, and adjusting an internal clock of the device to facilitate synchronizing the internal clock with the decoded timing information.
In another aspect, a system includes a power source, a timing source, and merging circuitry operatively connected to the power source to receive a power signal therefrom and operatively connected to the timing source to receive a timing signal therefrom. The merging circuitry is configured to superimpose the timing signal onto the power signal. The system also includes at least one device operatively connected to the merging circuitry to receive the power signal that includes the superimposed timing signal from the merging circuitry. The at least one device is configured to decode the timing signal from the power signal and adjust an internal clock of the at least one device based on the decoded timing signal to facilitate synchronizing the internal clock with the decoded timing signal.
In another aspect, a device operatively connectable to a power source to receive a power signal therefrom is provided. The device includes an antenna for receiving an electromagnetic wave signal that includes timing information from a timing source. The device is configured to decode the timing information from the electromagnetic wave signal and adjust an internal clock of the device based on the decoded timing signal to facilitate synchronizing the internal clock with the decoded timing signal.
Devices 18 and 19 may be any suitable device, such as, but not limited to, any protection, control, monitoring, metering, and/or recording device, such as, but not limited to, protective relays, programmable logic controllers, meters, sequence of event recorders, digital fault recorders, diagnostic devices, and/or monitoring devices. In the exemplary embodiment, devices 18 and 19 are Intelligent Electronic Devices (IEDs).
Timing source 16 may be any suitable timing source that is capable of performing the functions described herein. Timing source 16 may receive a signal containing timing information, sometimes referred to herein as a timing signal, from an external source (not shown), for example via a standard signal format, a proprietary signal format, and/or a synchronization method. Moreover, and for example, in some embodiments the timing source may receive a signal provided via a dedicated signal and/or a packet-based synchronization mechanism. In other embodiments, timing source 16 may generate the timing signal internally based on a radio and/or satellite signal, such as, but not limited to a publicly available radio signal, a publicly available satellite signal, an atomic clock signal, a weather radio signal, a specialized terrestrial timing wave, and/or a cellular phone signal.
Merging circuitry 12 is operatively coupled to power source 14 and timing source 16 for superimposing a timing signal received from timing source 16 onto a power signal received from power source 14.
Merging circuitry 12 superimposes the timing signal received from timing source 16 onto the power signal received from power source 14, using any suitable modulation technique, to facilitate creating a different power signal that includes the timing signal. Merging circuitry 12 includes a coupling circuit 26 that communicates with a coupling circuit 28 in devices 18 to deliver the power signal that includes the timing signal to devices 18. In some embodiments, merging circuitry 12 includes an isolation circuit 30 that facilitates isolating components of system 10. For example, in some embodiments isolation circuit 30 monitors system 10 and the dc voltage of power source 14 for short circuits with ground that may damage components of system 10.
In the exemplary embodiment, system 10 includes one or more of devices 19, which do not receive timing signals superimposed onto the power signal, but rather are operatively connected directly to timing source 16 to receive the timing signal directly from timing source 16, similar to known methods. In some embodiments, some or all of devices 19 may not be operatively connected to timing source 16 and/or may not receive a timing signal from timing source 16. In some embodiments, merging circuitry 12 superimposes the timing signal onto the power signal in such a way that facilitates a superimposing a timing signal of a low enough energy such that the superimposed timing signal may not degrade the power signal, and therefore may not interfere with operation of devices 19, which may not expect and/or recognize the timing information in the power signal. Moreover, in some embodiments merging circuitry 12 superimposes the timing signal onto the power signal in such a way that facilitates superimposing a timing signal that may be at least partially immune to transients in system 10, such as, but not limited to, breakers (not shown) and/or short-circuits. Furthermore, in some embodiments merging circuitry 12 superimposes the timing signal onto the power signal in such a way that facilitates superimposing a timing signal that may not interfere with ground monitoring systems (not shown) and/or may not interfere with breaker monitoring systems (not shown).
Devices 18 receive the power signal that includes the superimposed timing signal and decode the timing signal from the power signal. More specifically, devices 18 separate the timing signal from the power signal. Devices 18 then adjust an internal clock 32 thereof based on the timing signal to facilitate synchronizing internal clock 32 with the decoded timing signal. As such, the timing signal is distributed to devices 18 without a dedicated connection, but rather using the existing power supply connections 20. Accordingly, system 10 may facilitate reducing an overall cost of timing synchronization as well as may facilitate increasing a reliability of timing synchronization. In some embodiments, time synchronization is performed by devices 18 within seconds or tens of seconds. Moreover, in some embodiments devices 18 may skip synchronization for several seconds if devices 18 include ride-through capabilities. Furthermore, in some embodiments, the timing signal may be checked for consistency and/or errors, which may be detected and/or rejected. In some embodiments, system 10 may facilitate of accuracy of time synchronization in a range of microseconds. Moreover, in some embodiments a reduction or elimination of cabling and the associated capacitances, for example due to proximity of devices 18 to power source 14, may facilitate improving an accuracy of the time synchronization.
Devices 54 and 19 may be any suitable device, such as, but not limited to, any protection, control, monitoring, metering, and/or recording device, such as, but not limited to, protective relays, programmable logic controllers, meters, sequence of event recorders, digital fault recorders, diagnostic devices, and/or monitoring devices. In the exemplary embodiment, devices 54 and 19 are Intelligent Electronic Devices (IEDs). Moreover, devices 54 each include an antenna for receiving the electromagnetic wave signal transmitted by timing source 52.
In the exemplary embodiment, system 50 includes one or more of devices 19, which do not receive the electromagnetic wave signal transmitted by timing source 52, but rather are operatively connected directly to timing source 16 to receive a timing signal directly from timing source 16, similar to known methods. In some embodiments, some or all of devices 19 may not be operatively connected to timing source and/or may not receive a timing signal from timing source 16.
Devices 54 receive the electromagnetic wave signal that includes the timing information and decode the timing information from the electromagnetic wave signal. Devices 54 then adjust an internal clock (not shown) thereof based on the timing information to facilitate synchronizing the internal clock with the decoded timing information. As such, the timing signal may be distributed to devices 54 without a dedicated connection, but rather using the electromagnetic wave signal transmitted by timing source 52. Accordingly, system 50 may facilitate reducing an overall cost of timing synchronization as well as may facilitate increasing a reliability of timing synchronization. In some embodiments, time synchronization is performed by devices 54 within seconds or tens of seconds. Moreover, in some embodiments devices 54 may skip synchronization for several seconds if devices 54 include ride-through capabilities. Furthermore, in some embodiments, the timing signal may be checked for consistency and/or errors, which may be detected and/or rejected.
In some embodiments, system 50 includes a plurality of timing sources 52 that each transmit an electromagnetic wave signal. Each of the signals may be averaged, monitored, amplified, and/or responded to by system 50. Moreover, in some embodiments, one or more of the timing sources 52 may be automatically selected by system 50 and/or may be pre-selected based on a reception of each of the signals and/or an accuracy of the timing information of each of the signals. In some embodiments, system 50 may facilitate of accuracy of time synchronization in a range of microseconds.
Exemplary embodiments of systems and methods are described and/or illustrated herein in detail. The systems and methods are not limited to the specific embodiments described herein, but rather, components of each system, as well as steps of each method, may be utilized independently and separately from other components and steps described herein. Each component, and each method step, can also be used in combination with other components and/or method steps. For example, portions or all of the timing synchronization methods of systems 10 and 50 may be combined, for example to provide a primary and a backup mode of timing synchronization. Portions or all of the timing synchronization methods of systems 10 and/or 50 may also be combined with known timing synchronization methods.
When introducing elements/components/etc. of the systems and methods described and/or illustrated herein, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the element(s)/component(s)/etc. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional element(s)/component(s)/etc. other than the listed element(s)/component(s)/etc.
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
