• 专利附录
  • 专利说明
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    • 专利摘要:
    Systems and methods for detecting the failure of a precision time source using an independent time source are disclosed. Additionally, detecting the failure of a GNSS based precision time source based on a calculated location of a GNSS receiver is disclosed. Moreover, the system may be further configured to distribute a time derived from the precision time source as a precision time reference to time dependent devices. In the event of a failure of the precision time source, the system may be configured to distribute a time derived from a second precision time source as the precision time signal during a holdover period.
    公开号:ES2565702A2
    申请号:ES201590016
    申请日:2013-09-05
    公开日:2016-04-06
    发明作者:David E. Whitehead；Shankar V ACHANTA；Henry Loehner
    申请人:Schweitzer Engineering Laboratories Inc；
    IPC主号:
    专利说明:

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    DESCRIPTION
    QUALITY OF PRECISION TIME SOURCES
    RELATED APPLICATIONS
    The present application claims the benefit, according to US Code 35, § 119 (e), of US Patent Application 14 / 017,522, filed on September 4, 2013 and entitled "Quality of precision time sources", which claims the benefit of Provisional US Patent Application No. 61 / 698,583, filed on September 8, 2012, and entitled "Quality of precision time sources", both incorporated herein by reference in their entirety.
    TECHNICAL FIELD
    The present disclosure relates to the detection of the failure of a precision time source, using an independent time source. In particular, this disclosure refers to detecting the failure of a precision time source in an electrical energy transmission or distribution system.
    BRIEF DESCRIPTION OF THE DRAWINGS
    Non-limiting and non-exhaustive embodiments of the disclosure are described, including various embodiments of the disclosure with reference to the figures, in which: Fig. 1 is a single-line diagram of an electric power supply system.
    Fig. 2 illustrates a time distribution system that includes communications IEDs, configured to distribute a precision time reference to various IEDs.
    Fig. 3 illustrates an embodiment of a time distribution device, configured to receive, distribute and / or determine a precision time reference.
    Fig. 4 illustrates an embodiment to determine if a primary time source has failed, or the best available one.
    Fig. 5 illustrates another embodiment to determine if a primary time source has failed, or the best available one.
    Fig. 6 illustrates an embodiment to determine whether a primary time source, or the best available one, has failed based on the location of the GNSS.
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    In the following description, numerous specific details are provided for a comprehensive understanding of the various embodiments disclosed herein. However, those skilled in the art will recognize that the systems and procedures disclosed herein may be implemented without one or more of the specific details, or with other procedures, components, materials, etc. In addition, in some cases, well-known structures, materials or operations may not be shown or described in detail, in order to avoid obscuring aspects of the disclosure. In addition, the functions, structures or features described can be combined in any suitable manner in one or more alternative embodiments.
    DETAILED DESCRIPTION
    Electricity transmission and distribution systems can use precision time information to perform various monitoring, protection and communication tasks. In relation to certain applications, intelligent electronic devices (IED) and network communication devices can use time information, which is beyond the range of milliseconds. IEDs within an energy system can be configured to perform reading, control and protection functions that require a certain level of precision between one or more FDI. For example, IEDs may be configured to calculate and communicate time synchronized phasors (synchronizers), which may require that IEDs and network devices be synchronized with each other on the nanosecond scale. Many protection, reading, control and automation algorithms used in energy systems can benefit, or require the reception, of accurate time information.
    Various systems can be used for the distribution of precision time information. According to various embodiments disclosed herein, an energy system may include connected components using a synchronized optical network (SONET). In such embodiments, the precision time information can be distributed using a smcrono transport protocol and smcrono transport modules (STM). According to one embodiment, a precision time reference can be transmitted within a frame of a SONET transmission. In another embodiment, a precision time reference can be incorporated into a header, or an overload part, of a frame of an STM of a SONET. Similarly, the power system may include components connected using the Jerarqda Digital Smcrona (SDH) protocol. Although several embodiments herein are described in terms of a SONET,
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    It should be recognized that the SDH protocol can be used instead of a SONET, unless otherwise specified.
    IEDs, network devices and other devices in an energy system can include local oscillators or other time sources, and can generate a local time signal. In some circumstances, however, external time signals, provided by a time distribution device, may be more accurate and may therefore be preferred over local time signals. An energy system may include a data communications network that transmits a precision time reference from the time distribution device to time-dependent devices, connected to the data communications network. In some embodiments, the communications network may include one or more local area networks (LAN) and one or more wide area networks (WAN). In a system with multiple LANs, multiple time distribution devices (one or more for each LAN) can be connected to the data communications network and each time distribution device can provide a precision time reference to other time distribution devices by WAN In each time distribution device, the precision time reference can be received or obtained from an external precision time signal.
    According to various embodiments, each time distribution device receives multiple precision time signals from various time sources and is configured to provide the best precision time signal available as the precision time reference. Precision time signals can be received using an Inter-gradual Instrumentation Group (IRIG) protocol, a global satellite navigation system (GNSS) such as, for example, the global localization system (GPS), GLONASS or similar , a radio broadcast such as a broadcast from the National Institute of Science and Technology (NIST) (e.g., WWV, WWVB and WWVH radio stations), the IEEE 1588 protocol, an encrypted network chronological protocol (NTP) in RFC 1305, a simple chronological network protocol (SNTP) in RFC 2030 and / or another protocol or time transmission system.
    While the precision time signals listed above may provide an accurate time for a time distribution device, they vary in quality. For example, the accuracy of the NTP and SNTP is limited to the millisecond range, thus making them unsuitable for time distribution applications below the milliseconds. In addition, both protocols lack security and are susceptible to malicious attacks
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    in network. The IEEE 1588 standard includes temporary hardware-assisted seals, which allows hourly accuracy in the nanosecond range. Such precision may be sufficient for more demanding applications (eg, sampling of sinusoidal currents and voltages in power lines to calculate "synchro-phasors"). It is well adapted for the time distribution at the periphery of the networks. of communication, or between individual devices within the network. The GNSS time signals provide a very precise and robust time measurement; however, the GNSS signals are susceptible to falsification. Therefore, it would be advantageous to provide a system and a procedure for detecting a fault in any of the precision time signals received, so that the best precision time reference available to time-dependent devices can be provided.
    In certain embodiments, when the time distribution device determines that the connection with the best available time source has failed, a new best available time source can be selected from the remaining available time sources. In addition to relying on a precision time reference from the time distribution device, when available, the various time-dependent devices can be configured to enter a lag period when the precision time reference is not available. In some embodiments, a device may be configured to monitor the drift of a local time source with respect to the precision time reference and to retain information regarding the drift. During the lag period, an IED or a network device can rely on a local time signal.
    The full reference of this specification to "a realization" indicates that a particular feature, structure or feature, described in relation to the embodiment is included in at least one embodiment. Thus, the occurrences of the phrase " in one embodiment ”in various places throughout the length of this specification they are not necessarily referring to the same embodiment. In particular, an "embodiment" may be a system, a manufacturing article (such as a computer readable storage medium), a process and a product of a process.
    The terms "connected with", "in network" and "in communication with" refer to any form of interaction between two or more entities, including mechanical, electrical, magnetic and electromagnetic interaction. Two components can be connected to each other even though don't be in direct physical contact with each other and even though there may be
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    intermediate devices between the two components.
    Part of the infrastructure that can be used with the embodiments disclosed herein is already available, such as: general purpose computers, computer programming tools and techniques, digital storage media and optical networks. A computer may include a processor such as a microprocessor, a microcontroller, logic circuits or the like. The processor may include a special purpose processing device, such as an ASIC, PAL, PLA, PLD, a Formation of Field Programmable Gates or other custom or programmable device. The computer may also include a computer readable storage device, such as non-volatile memory, static RAM, dynamic RAM, ROM, CD-ROM, disk, tape, magnetic, optical or flash memory, or other computer readable storage media .
    As used herein, the term "IED" may refer to any microprocessor-based device that monitors, controls, automates and / or protects monitored equipment within the system. Such devices may include, for example, remote terminal units, differential relays, remote relays, directional relays, feeder relays, excess current relays, voltage regulator controls, voltage relays, switch failure relays, generator relays, motor relays, automation controllers, compartment controllers, counters, reset controls, communications processors, calculation platforms, programmable logic controllers (PLC), programmable automation controllers, input and output modules and the like. IEDs can be connected to a network, and communication through the network can be facilitated by network-forming devices, which include, but are not limited to, multiplexers, routers, hubs, gateways, firewalls and switches. In addition, networking and communication devices can be incorporated into an IED or be in communication with an IED. The term IED can be used interchangeably to describe an individual IED or a system comprising multiple IEDs.
    IEDs, network devices and time distribution devices can be physically different devices, they can be composite devices or they can be configured in a wide variety of ways to perform overlapping functions. IEDs, network devices and time distribution devices can comprise multi-function hardware (e.g., processors, readable storage media
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    by computer, communications interfaces, etc.) that can be used to perform a wide variety of tasks, including tasks usually associated with an IED, a network device and / or a time distribution device. For example, a network device, such as a multiplexer, can also be configured to issue control instructions to an item of monitored equipment. In another example, an IED can be configured to function as a firewall. The IED may use a network interface, a processor and appropriate software instructions, stored in a computer-readable storage medium, in order to function simultaneously as a firewall and as an IED. In another example, an IED may include the necessary hardware and software instructions to function as a time distribution device for other IEDs on a LAN or a WAN. In order to simplify the exposure, various embodiments disclosed herein are illustrated in relation to time distribution devices; however, one skilled in the art will recognize that the disclosures of the present disclosure, including those disclosures illustrated only in relation to time distribution devices, are also applicable to IEDs and network devices.
    Aspects of certain embodiments described herein may be implemented as software modules or components. As used herein, a software module or component may include any type of computer instruction or computer executable code located within a computer-readable storage medium. A software module, for example, may comprise one or more physical or logical blocks of computer instructions, which may be organized as a routine, a program, an object, a component, a data structure, etc., which performs a or more tasks or implements specific types of abstract data.
    In certain embodiments, a specific software module may comprise dissimilar instructions stored in different locations of a computer-readable storage medium, which together implement the described functionality of the module. Indeed, a module can comprise a single instruction or many instructions, and can be distributed among several different code segments, between different programs and between several computer-readable storage media. Some embodiments may be implemented in a distributed computing environment, where the tasks are performed by a remote processing device linked through a communications network. In a distributed computing environment, software modules can be located on computer-readable, local and / or remote storage media. In addition, the data
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    linked or represented together in a database record may be resident in the same computer-readable storage medium, or between several computer-readable storage media, and may be linked together in fields of a record in a database over a network
    The software modules described herein tangibly perform a program, functions and / or instructions that are executable by one or more computers to perform tasks such as those described herein. The appropriate software, as applicable, can be immediately provided by experts in the relevant technique (s), using the disclosures presented herein, and programming languages and tools, such as XML, Java , Pascal, C ++, C, database languages, API, SDK, assembled code, firmware, micro-code and / or other languages and tools.
    A precision time reference refers to a time signal or time source on which a plurality of devices are supported, and distributed by a time distribution device, and which is supposed to be more accurate than a local time source. Precision determination can be made based on a wide variety of factors. A precision time reference can admit that specific moments in time are described and temporarily compared to each other.
    A time source is any device that is able to track the passage of time. A wide variety of time source types are contemplated, including a temperature compensated and voltage controlled crystal oscillator (VCTCXO), a phase locked loop oscillator, a time locked loop oscillator, a rubidium oscillator, a cesium oscillator, a trained oscillator, a micro-electromechanical device (MEM) and / or another device capable of tracking the passage of time.
    A time signal is a representation of the time indicated by a time source. A time signal can be performed as any form of communication to communicate time information. A wide variety of time signal types are contemplated, such as those listed above. The time source and the time signal may be used interchangeably herein.
    The failure of a precision time source and / or a precision time signal, as used herein, includes falsification and / or signal blocking, mechanical failures
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    or software, blackouts of the entire system, etc.
    In addition, the features, operations or features described can be combined in any suitable manner in one or more embodiments. It will also be immediately understood that the order of the steps or actions of the procedures described in relation to the embodiments disclosed herein may be changed, as will be apparent to those skilled in the art. Thus, any order in the drawings or the detailed description is for illustrative purposes only and is not intended to imply a required order, unless it is specified that an order is required.
    Figure 1 illustrates a single-line diagram of an electric power supply system 10. Supply system 10 includes intelligent electronic devices (IEDs) 102, 104 and 106 that use a precision time reference to monitor, protect and / or control System Components. The transmission and power supply system 10, illustrated in Figure 1, includes three substations 16, 22 and 35, geographically separated. Substations 16 and 35 include generators 12a, 12b and 12c. Generators 12a, 12b and 12c generate electrical energy at a relatively low voltage, such as 12kV. Substations include incremental transformers 14a, 14b and 14c to increase the voltage to a level suitable for transmission. The substations include various switches 18 and buses 19, 23 and 25 for the proper transmission and distribution of electrical energy. Electric power can be transmitted over long distances, using various transmission lines 20a, 20b and 20c.
    Substations 22 and 35 include the decremental transformers 24a, 24b, 24c and 24d to decrease the electrical energy to a level suitable for distribution to various loads 30, 32 and 34, using distribution lines 26, 28 and 29.
    IEDs 102, 104 and 106 are illustrated in substations 16, 22 and 35, configured to protect, control, measure and / or automate certain equipment or devices of the energy system. According to several embodiments, numerous FDI are used in each substation; However, for clarity, only one FDI is illustrated in each substation. IEDs 102, 104 and 106 can be configured to perform various time-dependent tasks that include, but are not limited to, the monitoring and / or protection of a transmission line, a distribution line and / or a generator. Other IEDs included in a substation can be configured as bus protection relays, remote relays, communications processors, automation controllers, protection relays
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    Transformer and the like. Since each IED, or group of IED, can be configured to communicate by a local area area (LAN) or a wide area network (WAN), each IED, or group of IED, can be considered a node in a network of communications
    As stated above, an FDI can be configured to calculate and communicate synchro-phasors with other FDI. To accurately compare the syncro-phasors obtained by geographically diverse IEDs, each IED may need to be synchronized with a precision time reference, with accuracy greater than one millisecond to allow time-aligned comparisons. According to various embodiments, time synchronization, accurate to the range of micro-seconds or nano-seconds, can allow IEDs to make accurate comparisons of synchro-phasors.
    Figure 2 illustrates the system 200 configured to be a highly reliable, redundant and distributed system of distribution devices 204, 206 and 208, capable of providing a precision time reference to various time-dependent IED 212, 214 and 216. Each time distribution device 204, 206 and 208 can be configured to receive and communicate time signals through multiple protocols and procedures. While system 200 is described as capable of performing numerous functions and procedures, it should be understood that various systems are possible that may have additional capabilities, or less capabilities.
    Specifically, a system 200 can operate as desired using only one protocol, or with fewer external or local time signal inputs.
    As illustrated in Figure 2, three time distribution devices 204, 206 and 208 have WAN capabilities and are communicatively connected to a WAN 218, which may comprise one or more physical connections and protocols. Each time distribution device 204, 206 and 208 may also be connected to one or more IEDs within a local network. For example, the time distribution device 204 is connected to the IED 212, the time distribution device 206 is connected to the IEDs 214, and the time distribution device 208 is connected to the IEDs 216. A time distribution device may be located, for example, in a power generation utility, a concentrator, a substation, a charging center or other location where one or more FDI is located. In various embodiments, an IED may include a WAN port, and such an IED may be directly connected to the WAN 218. The IEDs may be connected via the WAN 218 or the LAN 210. The
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    Time distribution devices 204, 206 and 208 can establish and maintain a precision time reference between various system components. Each time distribution device 204, 206 and 208 can be configured to communicate time information with the IEDs connected in its LAN, by means of one or more time distribution protocols, such as IEEE 1588.
    Each time distribution device 204, 206 and 208 is configured to receive time signals from a wide variety of time sources. For example, as illustrated, the time distribution device 204 includes an antenna 220 and is configured to receive a GNSS signal from a GNSS repeater or satellite 202. The time distribution device 204 is also configured to receive a second signal. time 221 from an external time source 201. The external time source may comprise one or more VCTCXO, phase locked loop oscillators, time locked loop oscillators, rubidium oscillators, cesium oscillators, NIST emissions (e.g. ., from WWV and WWVB) and / or other devices capable of generating accurate time signals. In the illustrated embodiment, the time distribution device 208 includes an antenna 220 configured to receive a GNSS signal from the GNSS repeater or satellite 202. As illustrated, the time distribution device 206 does not directly receive an external time signal; however, according to alternative embodiments, any number and variety of external time signals may be available for any of the time distribution devices.
    According to one embodiment, the WAN 218 comprises a SONET configured to integrate a precision time reference in a header, or part of overload, of a frame of a SONET during transmission. Alternatively, a precision time reference can be transported using any number of time communication procedures, including IRIG, NTP, SNTP protocols, smcrono transport protocols (STP) and / or IEEE 1588 protocols. According to various embodiments, Including the transmission via SONET, a precision time reference can be separated and protected from the rest of the WAN network traffic, thus creating a secure time distribution infrastructure. The protocols used for time synchronization between IEDs may be industrial property, or be based on a standard such as the IEEE 1588 Chronological Precision Protocol (PTP).
    According to various embodiments, time distribution devices 204, 206 and 208 are configured to perform at least one of the failure detection procedures
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    of a time source described herein. System 200 may use a single procedure, or a combination of procedures, as described herein.
    It should be noted that even the most accurate time signals can exhibit small discrepancies. For example, according to the length and routing of the GNSS antenna cable, different clocks can exhibit chronological phase shifts at the micro-second level. Some of these offsets may be compensated for by user input of compensation settings, or they may need to be estimated by the time synchronization network. The estimation can be performed during long periods of "quiet" operation (ie periods without any failure), with the results of individual sources stored locally in a non-volatile storage register.
    Figure 3 illustrates a time distribution device 304, according to a realization. A time distribution device 304 may include more or less functionality than in the illustration. For example, the time distribution device 304 may include an interface for monitoring equipment in an electric power supply system, in certain embodiments. Consequently, in various embodiments, the time distribution device 304 may be implemented, either as an IED or as a network device. As illustrated, the time distribution device 304 includes a local time source 302 that provides a local time signal and a time quality module 305 to establish a precision time reference. The time distribution device 304 also includes a pair of ports 312 and 314 for communications with a WAN or LAN. The time information can be shared by a network and can also be supplied to the time quality module 305. In addition, the time distribution device 304 includes a GNSS receiver 310 to receive a precision time signal, such as the time from a GNSS , through an antenna 320 of the GNSS. The time distribution device 304 also includes a WWVB receiver 330 to receive a broadcast from the NIST, which can be used as a precision time signal, by an external antenna 340. The precision time signal received from any source is communicated to the module. of 305 time quality, for use in determining and distributing the precision time reference.
    Another time source that can be supplied to the time quality module 305 includes an external time source 306 that can be in accordance with a time distribution protocol, such as IRIG. External time source 306 can communicate with another chronological port,
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    such as an IRIG input 308.
    The various time information from the WAN (from lmea ports 312 and / or 314), GNSS receiver 310, WWVB receiver 330 and IRIG input 308 are entered into time quality module 305. In one realization, The inputs can be supplied to a multiplexer (not shown) before being entered into the 305 time quality module. The 305 time quality module works to determine a precision time reference, for use by the various devices connected to the device. time distribution 304. The precision time reference is then communicated from the time quality module 305 to the various devices 322, using the IRIG protocol (via output 316 of IRIG-B), or to the various devices 325, using another protocol 313 , such as IEEE 1588, which uses Ethernet Ports 318. The Ethernet Ports 318 can also include network communications for the various devices connected to the time distribution device 304. The time distribution device 304 may also include connections with SONET networks and transmit the precision time reference in a header, or part of excess, of SONET frames.
    The time distribution device 304 may also comprise a time signal adjustment subsystem 324. The time signal adjustment subsystem 324 may be configured to track degrees of drift associated with various external time sources with respect to the local time source 302. The 324 time signal adjustment subsystem can also communicate time signals according to a wide variety of protocols. Such protocols may include the protocols of the Inter-Gradual Instrumentation Group, IEEE 1588, the Network Chronological Protocol, the Simple Network Chronological Protocol, the smchronous transport protocol and the like. In various embodiments, the time signal setting subsystem 324 can be implemented using a processor in communication with a computer-readable storage medium, which contains machine-executable instructions. In other embodiments, the time signal adjustment subsystem 324 may be performed as hardware, such as a specific integrated circuit of the application, or a combination of hardware and software.
    According to various embodiments, the time quality module 305 determines whether a primary time source is reliable or not, or "best available", that is, if it has not failed, and distributes the time signal from the best available time source as the precision time reference to time-dependent devices in the system.
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    The best available time source has failed, time quality module 305 provides an error alert to a user and, in some embodiments, enters a lag period where an alternative time signal is used for precision time reference. These techniques allow the best available time source to be used as the precision time reference, provided to time-dependent devices, in a robust manner, so that there is a high probability that the precision time reference is accurate. In addition, in certain embodiments, relying on a secondary time source, provided to the time quality module 305 as the precision time reference during a lag time when the primary time reference has failed, can provide more accurate time information than in the situation of lag described above, where a local oscillator is used in each time-dependent device during the lag.
    In some embodiments, after a period of time using the secondary time source, a primary time source may become available again. The 305 time quality module can determine whether the primary time source is reliable or not. If the primary time source is reliable, the time distribution device 304 may start using the primary time source for precision time reference. However, if it is determined that the primary time source is unreliable, the time distribution device 304 may continue to use the secondary time source for precision time reference and provide an error alert to a user, indicating the availability and lack of reliability of the primary time source.
    Figure 4 illustrates a realization to determine whether or not a primary time source has failed or the best available one. While the time signals in the example in Figure 4 are described as specific signals, other signals can be used with similar results. In 402 the time distribution device receives a first time signal from a first time source, or the best available time source, and provides the time signal to the time quality module. In one embodiment, the first time source is a time signal received from a GNSS system. GNSS time has the advantages of relying on extremely precise procedures to provide the time signal to GNSS receivers, being immediately available worldwide (in particular, in remote locations) 24 hours a day, and is expected to be stable. for many decades to come. GNSS receivers can maintain an internal time, based on the GNSS signal that is accurate to more than nano-seconds, and the time output at the dedicated 1 PPS (Pulse Per Second) chronological port is usually
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    more accurate than 1 micro-second.
    In 404 the time distribution device receives a second time signal from a second time source. In a realization, the second time source is an NIST broadcast, such as that of WWVB. While it is not as accurate as a time reference obtained from a GNSS signal, a time reference obtained from a WWVB broadcast is still very accurate. While the example in Figure 4 specifically uses a WWVB broadcast as the second time source, a person skilled in the art will recognize that other time sources, such as those described above, may be used instead of the WWVB broadcast. .
    In 406 the time quality module compares the first time signal with the second time signal. Each of the time signals received by the time quality module has an inherent error rate related to the accuracy of the time signal. In one embodiment, the time quality module compares the time signals with respect to their respective error rates, to determine whether the first time source has failed or not. For example, given the relatively smaller error level, found in the time obtained from a GNSS signal, compared to that found in an hour obtained from a WWVB broadcast, the time based on the GNSS signal should fall within the time error rate based on the WWVB broadcast. However, if the GNSS-based time signal falls outside the WWVB-based time signal error level, the time quality module detects, at 408, that there is an error in the GNSS-based time signal.
    If, in 408, the time quality module determines that the first time source has not failed, the time quality module distributes the time from the first time signal, such as the precision time reference, in 410. If, in 408, the Time quality module determines that the first time source has failed, in 412 the time quality module alerts a user that the best available time source has failed and that the time may not be accurate. In addition to alerting a user of the fault, the time quality module, in 414, can optionally distribute the time from the second time signal, as the precision time reference.
    While the example in Figure 4 is limited to a first and second time signal, the time quality module can continue comparing time signals, in the order of relative error rates, beyond just a first and second time signal. For example, the WWVB based time can be compared to the time of a local oscillator
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    (taking into account the degree of oscillator drift) to determine if the WWVB source has failed or not, etc.
    Figure 5 illustrates a second realization to determine whether a primary time source, or the best available one, has failed or not. While the time signals in the example in Figure 5 are described as specific signals, other signals with similar results can be used. In 502 the time distribution device receives a first time signal from a first time source, or the best available time source, and provides the time signal to the time quality module. In one embodiment, the first time source is a time signal received from a GNSS system.
    In 504 the time distribution device uses the first time signal to train an unlocked oscillator to track the time provided in the first time signal. While the oscillator is trained to track the time of the first time source, because the oscillator is unlocked, the time provided by the trained oscillator will be derived from that of the first time signal. However, the degree of drift is low and the time distribution device maintains the training relationship between the first signal and the oscillator, so that the drift is corrected.
    In 506 the time quality module compares the first time signal with the trained oscillator (again, taking into account the degree of drift associated with the trained oscillator). In one embodiment, a counter tracks the number of oscillator oscillations between each PPS received from the first time signal. Because the oscillator is trained for the first time signal, any variation in the oscillation counter between PPS and PPS should be low. If there is a big jump in the variation in the oscillation counter, the time quality module, at 508, detects a failure of the first time source. The threshold to determine whether or not the time quality module detects a failure of the time source may depend on the characteristics of the oscillator used. For example, a temperature compensated crystal oscillator (TCXO) can have a degree of drift in the range of parts per million, while oven-controlled crystal oscillators and cesium-based oscillators can have a degree of drift in the range of parts per billion. Thus, the threshold for the most accurate oscillator can be higher. If the variation in the oscillation counter exceeds the threshold, the time quality module may indicate a failure of the first time source.
    In another embodiment, the oscillator can be used to validate time quality measurements.
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    transmitted as part of the time source. For example, an IRIG signal includes an indication of Hourly Quality and Continuous Hourly Quality. The time quality module can use the oscillator to validate the received time quality signal as part of the time source.
    If, in 508, the time quality module determines that the first time source has not failed, the time quality module distributes the time from the first time signal as a precision time reference, in 510. If, in 508, the Time quality module determines that the first time source has failed, in 512 the time quality module alerts a user that the best available time source has failed and that the time may not be accurate. In addition to alerting a user of the fault, the time quality module, in 514, can optionally distribute the time from the trained oscillator, or from a second time source, as the precision time reference during a lag period.
    In some embodiments, if a second time source is to be used for precision time reference, the time quality module can determine whether the second time source is acceptable or not. For example, the time quality module can determine whether or not the time provided by the second time source falls within an acceptable environment of the current time provided by the time distribution device (e.g., the time set by the oscillator internal). If the time falls within the acceptable environment, the second time source can be used to provide the precision time reference.
    The preceding exemplary embodiments provide a robust system for providing a precision time reference to time-dependent devices, comparing several time signals to determine whether the best available time source has failed or not. Figure 6 illustrates a realization to determine whether a primary time source, or the best available one, has failed or not, based on the location of the GNSS. In embodiments where the GNSS is the best available time source, the location obtained from the GNSS signal can be used to verify the failure of the GNSS time source. This procedure is particularly useful in embodiments where the time distribution device is in a known and fixed location. In one embodiment, the known location of the time distribution device may be entered by a user at the time of configuration and may be modified as necessary. In another embodiment, the known location of the time distribution device can be calculated using GNSS signals.
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    In 602, the time distribution device receives the GNSS signal. While the example in Figure 6 is described in terms of a single GNSS signal, for clarity, someone moderately skilled in the art will recognize that multiple signals from various GNSS satellites are commonly used in determining the location of the receiver of the GNSS. GNSS, and can be used to more accurately calculate the location of the GNSS receiver. In 604, the GNSS receiver calculates the location of the time distribution device, based on the GNSS signal received. The time quality module, at 606, compares the calculated location of the time distribution device with the known location of the time distribution device and determines whether or not the calculated location falls within a threshold distance from the known location. Because the calculation of GNSS locations varies based on the techniques employed by the GNSS receiver, the threshold distance may vary between one device and another.
    If, in 608, the time quality module determines that the location of the GNSS falls within the threshold, the time quality module distributes the GNSS time as the precision time reference, in 610. If, in 608, the quality module time determines that the location of the GNSS falls outside the threshold and, therefore, the time source of the GNSS has failed, in 612 the time quality module alerts a user that the best available time source has failed and that the Time may not be exact. In addition to alerting a user of the fault, the time quality module, in 614, can optionally distribute the time from a secondary time source, such as the precision time reference during a lag period.
    In another embodiment, the hourly quality module can calculate a degree of drift from the location using the GNSS signal, and compare the degree of drift from the location with a defined threshold. If the degree of drift of the location exceeds the defined threshold, the time quality module can determine, in 608, that the GNSS time source has failed.
    In one embodiment, the time quality module monitors the instantaneous and average signal strength of the GNSS signal. If the instantaneous signal strength is greater than a set threshold for a set number of samples, then the time quality module can determine that the GNSS time source has failed. In this case, the time quality module can alert a user and / or rely on a secondary time signal.
    In another embodiment, the satellite constellation can be monitored. The constellation of
    Satellite repeats every 24 hours. The time quality module can determine that the GNSS time source has failed to detect a change in satellite constellation. In this case, the time quality module can alert a user and / or rely on a secondary time signal.
    5
    The above description provides numerous specific details for a comprehensive understanding of the embodiments described herein. However, those skilled in the art will recognize that one or more of the specific details may be omitted, or that other procedures, components or materials may be used. In some cases, 10 operations are not shown or described in detail.
    While specific embodiments and applications of the disclosure have been illustrated and described, it should be understood that the disclosure is not limited to the precise configuration and components disclosed herein. Various modifications, changes and variations, evident to those skilled in the art, can be made in the arrangement, operation and details of the procedures and systems of the disclosure, without departing from the spirit and scope of the disclosure.
    权利要求:
    Claims (20)
    [1]
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    1. A procedure comprising:
    receive, on a time distribution device, a first time signal from a first precision time source;
    receive, on the time distribution device, a second time signal from a second precision time source, independent of the first precision time source;
    compare, by a time quality component of the time distribution device, the first time signal with the second time signal; Y
    detecting, by the time quality component, a failure of the first precision time source, in response to the comparison showing that a variation of the first time signal with respect to the second time signal exceeds a defined margin.
    [2]
    2. The method of claim 1, wherein the first precision time source is a time source of the global satellite navigation system (GNSS) and the first time signal is a pulse signal per second (PPS) of the GNSS.
    [3]
    3. The method of claim 1, wherein the second precision time source is a WWVB time source and the second time signal is a WWVB PPS.
    [4]
    4. The method of claim 1, further comprising:
    in response to the detection of a failure of the first precision time source, rely on the second precision time source.
    [5]
    5. A system comprising:
    a first receiver configured to receive a first signal that includes a first precision time signal;
    a second receiver configured to receive a second signal that includes a second precision time signal, independent of the first precision time signal, in which the second precision time signal is relatively less accurate than the first precision time signal;
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    an output configured to provide an output time signal to an intelligent electronic device (IED); Y
    a time quality module configured to compare the first precision time signal with the second precision time signal and detect an error condition of the first precision time signal, in response to a variation of the first precision time signal with respect to the second precision time signal, which exceeds a defined threshold.
    [6]
    6. The system of claim 5, wherein the first signal is a signal from the global satellite navigation system (GNSS).
    [7]
    7. The system of claim 5, wherein the second signal is a WWVB signal.
    [8]
    8. The system of claim 5, wherein the second signal is a network time signal.
    [9]
    9. The system of claim 5, further comprising an unlocked oscillator, trained for the first precision time signal, wherein the second precision time signal comprises a time signal from the unlocked oscillator.
    [10]
    10. The system of claim 5, wherein, in response to the detection of an error condition, the output is configured to provide the second precision time signal to the IED.
    [11]
    11. A procedure comprising:
    receive a signal from the global satellite navigation system (GNSS), which includes a time signal from the GNSS, on a time distribution device;
    determine, by the time distribution device, whether the GNSS has failed or not;
    in response to the determination that the GNSS has failed, indicate to a user an error condition; Y
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    in response to the determination that the GNSS has not failed, issue a time based on the GNSS time signal.
    [12]
    12. The procedure of claim 11, wherein determining whether the GNSS has failed or does not include:
    compare a given location from the GNSS signal with a known location of the time distribution device; Y
    determine that the GNSS has failed, in response to the fact that the location of the GNSS varies with respect to the known location in more than one defined threshold.
    [13]
    13. The procedure of claim 11, wherein determining whether the GNSS has failed or does not include:
    compare the GNSS time signal with an independent time signal; Y
    determine that the GNSS has failed, in response that the GNSS time signal varies with respect to the independent time signal by more than a defined threshold.
    [14]
    14. The procedure of claim 13, wherein the independent time signal is an emission signal from the National Institute of Science and Technology (NIST).
    [15]
    15. The method of claim 13, wherein the independent time signal is generated by an oscillator.
    [16]
    16. The method of claim 13, wherein the independent time signal is received by a network protocol.
    [17]
    17. The method of claim 13, further comprising:
    In response to the determination that the GNSS has failed, issue a time based on the independent time signal.
    [18]
    18. The procedure of claim 11, wherein determining whether the GNSS has failed or does not include:
    calculate a degree of location drift, based on the GNSS signal;
    compare the degree of location drift with a defined threshold; Y
    5
    determine that the GNSS has failed in response to the degree of location drift exceeding the defined threshold.
    [19]
    19. The procedure of claim 11, wherein determining whether the GNSS has failed or does not include:
    monitor the signal power, instantaneous and average, of the GNSS; Y
    determine that the GNSS has failed in response to the instantaneous signal power 15 exceeding a defined threshold for a fixed number of samples.
    [20]
    20. The procedure of claim 11, wherein determining whether the GNSS has failed or does not include:
    20 monitor satellite constellation; Y
    determine that the GNSS time source has failed, in response to the detection of a change in satellite constellation.
    类似技术:
    公开号 | 公开日 | 专利标题
    ES2565702B1|2018-07-04|QUALITY OF PRECISION TIME SOURCES
    ES2552829B1|2017-03-23|Time Distribution Switch
    US10379500B2|2019-08-13|Time distribution device with multi-band antenna
    US9813173B2|2017-11-07|Time signal verification and distribution
    US20100254225A1|2010-10-07|Fault tolerant time synchronization
    ES2391861B2|2014-01-09|Differential protection of line current after the loss of an external time reference
    US10375108B2|2019-08-06|Time signal manipulation and spoofing detection based on a latency of a communication system
    ES2538014A2|2015-06-16|Manipulation resilient time distribution network
    US9425652B2|2016-08-23|Adaptive holdover timing error estimation and correction
    US10527732B2|2020-01-07|Verification of time sources
    Kasztenny et al.2012|Fallback algorithms for line current differential protection applied with asymmetrical channels upon the loss of time reference
    同族专利:
    公开号 | 公开日
    WO2014039700A1|2014-03-13|
    ES2565702R1|2017-09-27|
    BR112015004585A2|2017-07-04|
    AU2013312463A1|2015-02-12|
    ES2565702B1|2018-07-04|
    US9709680B2|2017-07-18|
    MX2015001972A|2015-06-02|
    CA2882548A1|2014-03-13|
    US20140250972A1|2014-09-11|
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    US201261698583P| true| 2012-09-08|2012-09-08|
    US61/698,583|2012-09-08|
    US14/017,522|2013-09-04|
    US14/017,522|US9709680B2|2012-09-08|2013-09-04|Quality of precision time sources|
    PCT/US2013/058297|WO2014039700A1|2012-09-08|2013-09-05|Quality of precision time sources|
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