Power system time synchronization device and method for sequence of event recording
DCFirst Claim
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1. A time synchronization device of a power monitor for synchronizing a time of an internal clock to a line frequency, the internal time advancing at a predetermined rate, the device comprising:
- a counter operative to count cycles of the line frequency after each elapse of a predetermined time period, said elapse of said predetermined time period defining a present window and a previous window;
a processor operative to calculate a counting error and a change in counting error, said change in counting error being the difference of a counting error calculated for said present window and a counting error calculated for said previous window;
wherein said processor detects when said change in counting error is within a predetermined range; and
adjusting means for adjusting the internal clock to the line frequency according to said counting error calculated for said present window when said change in counting error is within said predetermined range.
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Abstract
A time synchronization device and method is provided for synchronizing an internal clock of the power monitor. The internal clock may be adjusted to a periodically stable frequency according to a calculated counting error. Also, a time of the internal clock may be synchronized to a universal time, the time of the internal clock advancing at a determined rate. The determined rate may be adjusted if the internal time differs from the universal time plus a processing time.
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Citations
93 Claims
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1. A time synchronization device of a power monitor for synchronizing a time of an internal clock to a line frequency, the internal time advancing at a predetermined rate, the device comprising:
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a counter operative to count cycles of the line frequency after each elapse of a predetermined time period, said elapse of said predetermined time period defining a present window and a previous window;
a processor operative to calculate a counting error and a change in counting error, said change in counting error being the difference of a counting error calculated for said present window and a counting error calculated for said previous window;
wherein said processor detects when said change in counting error is within a predetermined range; and
adjusting means for adjusting the internal clock to the line frequency according to said counting error calculated for said present window when said change in counting error is within said predetermined range. - View Dependent Claims (2)
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3. A method for synchronizing a time of an internal clock to a periodically stable frequency which provides accurate time intervals, the method comprising the steps of:
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counting cycles of the periodically stable frequency after each elapse of a predetermined time period, said elapse of said predetermined time period defining a present window and a previous window;
calculating a counting error and a change in counting error, said change in counting error being the difference of a counting error calculated for said present window and a counting error calculated for said previous window;
detecting when said change in counting error is within a predetermined range; and
adjusting the internal clock to the periodically stable frequency according to said counting error calculated for said present window, when said change in counting error is within said predetermined range. - View Dependent Claims (4, 5, 6, 7, 8)
receiving a time synchronization message from an entity at a first free running counter count, said time synchronization message containing a universal time when the time synchronization message was sent;
processing said time synchronization message at a second free running counter count to determine said universal time.
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7. The method according to claim 6, wherein said entity is a master computer.
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8. The method according to claim 6, wherein said entity is a global positioning system.
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9. A method of maintaining time synchronization in a power monitoring device, the power monitoring device being coupled to a power system operating at a first frequency and comprising at least one processor operating at a second frequency, the method comprising:
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receiving at least one time message from a time source;
accumulating counts in a free running counter in response to the second frequency;
wherein said free running counter is implemented by said processor;
advancing the internal time of the power monitoring device by a predetermined amount in response to said accumulation; and
adjusting said amount in response to indications from a time synchronization source. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
determining a difference between said time message and said internal time;
calculating a rate of change of said difference; and
adjusting said amount in response to said difference and said rate of change.
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13. The method of claim 10 further comprising:
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recording a first value of said free running counter in response to said receiving; and
subtracting a second value of said free running counter from said first value to compensate for passage of time from said receiving to said adjusting.
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14. The method of claim 9 wherein said time synchronization source comprises a computer.
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15. The method of claim 9 wherein said time synchronization source comprises a global positioning system.
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16. The method of claim 9 wherein said time synchronization source comprises said first frequency.
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17. The method of claim 9 wherein said indications comprise periods of said first frequency.
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18. The method of claim 9 wherein said indications comprise communication packets received from a master computer.
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19. The method of claim 9 wherein said indications comprise communications packets received from a GPS receiver.
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20. A method of maintaining synchronization between a clock in a power monitoring device and a clock in an entity, the power monitoring device being coupled to a power system, the method comprising:
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monitoring at least one power parameter in the power system with the power monitoring device;
receiving an indication of time by the power monitoring device from said entity;
implementing a free running counter with a processor within the power monitoring device;
recording a value of the free running counter when the indication is received; and
adjusting the rate of accumulation of time in the clock in the power monitoring device to track the clock in the entity. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
comparing said time in the clock in the power monitoring device with said indication of time, said comparison adjusted in accordance with an elapsed time between said receiving and said adjusting.
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22. The method of claim 21, wherein said indication comprises a timestamp and an on time mark.
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23. The method of claim 22, wherein said comparing further comprises:
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computing an adjusted difference in time between the clock in the power monitoring device and the clock in the entity;
setting the clock in the power monitoring device directly to the timestamp if said difference is more than a predetermined amount;
said timestamp being adjusted for the elapsed time between said receiving and said setting.
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24. The method of claim 23, wherein said predetermined amount comprises about one second.
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25. The method of claim 23, wherein said indication comprises a communications packet and said entity comprises a master computer.
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26. The method of claim 25, wherein said adjusting is further in accordance with a rate of change of said difference from one reception to a next reception.
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27. The method of claim 26, further comprising:
recording a time of occurrence of a fault in the power system using the clock.
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28. The method of claim 25, further comprising:
recording a time of occurrence of a fault in the power system using the clock.
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29. The method of claim 23, wherein the entity comprises at least one GPS satellite.
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30. The method of claim 29, further comprising:
recording a time of occurrence of a fault in the power system using the clock.
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31. The method of claim 28, wherein said indication comprises a communications packet and the entity comprises a GPS receiver.
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32. The method of claim 31, further comprising:
recording a time of occurrence of a fault in the power system using the clock in the power monitoring device.
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33. The method of claim 23, wherein said adjusting is further in accordance with a rate of change of said difference from one reception to a next reception.
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34. The method of claim 33, wherein the entity comprises at least one GPS satellite.
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35. The method of claim 33, wherein said indication comprises a communications packet and the entity comprises a GPS receiver.
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36. The method of claim 20, wherein said indication comprises a communications packet and the entity comprises a master computer.
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37. The method of claim 36, further comprising:
recording a time of occurrence of a fault in the power system using the clock.
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38. The method of claim 20, wherein the entity comprises at least one GPS satellite.
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39. The method of claim 38, further comprising:
recording a time of occurrence of a fault in the power system using the clock.
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40. The method of claim 20, wherein said indication comprises a communications packet and the entity comprises a GPS receiver.
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41. The method of claim 40, further comprising:
recording a time of occurrence of a fault in the power system using the clock in the power monitoring device.
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42. The method of claim 20, wherein said receiving further comprises:
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receiving a message comprising a timestamp and an on time mark; and
recording a first value of the free running counter upon reception of said on time mark.
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43. The method of claim 42, wherein said adjusting further comprises:
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recording a second value of said free running counter at a later time;
calculating a first difference in time between said second value and said first value, said timestamp being adjusted for said first difference; and
adjusting the rate of accumulation in accordance with a second difference in time between said timestamp and a time in the clock in the power monitoring device.
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44. The method of claim 43, wherein said adjusting is further in accordance with a rate of change of said second difference from one reception to a next reception.
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45. The method of claim 44, wherein said indication comprises a communications packet.
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46. The method of claim 45, wherein said communications packet is generated by a GPS receiver.
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47. The method of claim 46, further comprising:
recording a time of occurrence of a fault in the power system using the clock.
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48. The method of claim 45, further comprising:
recording a time of occurrence of a fault in the power system using the clock.
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49. The method of claim 43, further comprising:
recording a time of occurrence of a fault in the power system using the clock.
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50. The method of claim 42, further comprising:
recording a time of occurrence of a fault in the power system using the clock.
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51. A system for maintaining time synchronization between a plurality devices comprising:
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an entity, said entity comprising a master clock and said entity generating time synchronization messages;
a plurality of power monitoring devices coupled to a power system;
said power monitoring devices comprising;
a receiver operative to receive said time synchronization messages from said entity;
a processor operative to implement a clock and a free running counter;
wherein said processor adjusts a rate of accumulation of time in said clock in response to the reception of said time synchronization messages; and
wherein said processor monitors at least one power parameter in said power system. - View Dependent Claims (52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74)
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75. A method of maintaining synchronizaton between a clock in a power monitoring device and a clock in an entity, the power monitoring device being coupled to a power system, the method comprising:
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monitoring at least one power parameter in the power system with the power monitoring device;
receiving an indication of time by the power monitoring device from said entity;
adjusting the rate of accumulation of time in the clock in the power monitoring device to track the clock in the entity;
recording a time of occurrence of a fault in the power system using the clock;
wherein the entity comprises at least one GPS satellite.
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76. A method of maintaining synchronization between a clock in a power monitoring device and a clock in an entity, the power monitoring device being coupled to a power system, the method comprising:
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monitoring at least one power parameter in the power system with the power monitoring device;
receiving an indication of time by the power monitoring device from said entity;
wherein said receiving further comprises;
receiving a message comprising a timestamp and an on time mark; and
recording a first value of a free running counter upon reception of said on time mark;
adjusting the rate of accumulation of time in the clock in the power monitoring device to track the clock in the entity;
recording a second value of said free running counter at a later time;
calculating a first difference in time between said second value and said first value, said timestamp being adjusted for said first difference;
adjusting the rate of accumulation in accordance with a second difference in time between said timestamp and a time in the clock in the power monitoring device; and
recording a time of occurrence of a fault in the power system using the clock.
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77. A system for maintaining time synchronization between a plurality devices comprising:
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an entity, said entity comprising a master clock and said entity generating time synchronization messages;
a plurality of power monitoring devices coupled to a power system;
said power monitoring devices comprising;
a receiver operative to receive said time synchronization messages from said entity;
a processor operative to implement a clock;
wherein said processor adjusts a rate of accumulation of time in said clock in response to the reception of said time synchronization messages; and
wherein said processor monitors at least one power parameter in said power system;
wherein said processor compares the time in said clock with said time synchronization message;
said comparison being adjusted in accordance with a processing time of said time synchronization message;
wherein said processor records a time of said clock when a fault occurs in said power system. - View Dependent Claims (78, 79, 80, 81)
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82. A system for maintaining time synchronization between a plurality devices comprising:
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an entity, said entity comprising a master clock and said entity generating time synchronization messages;
a plurality of power monitoring devices coupled to a power system;
said power monitoring devices comprising;
a receiver operative to receive said time synchronization messages from said entity;
a processor operative to implement a clock;
wherein said processor adjusts a rate of accumulation of time in said clock in response to the reception of said time synchronization messages; and
wherein said processor monitors at least one power parameter in said power system;
wherein said processor records a time of said clock when a fault occurs in said power system. - View Dependent Claims (83, 84, 85, 86)
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87. A method of maintaining time synchronization in a power monitoring device, the power monitoring device being coupled to a power system operating at a first frequency and comprising at least one processor operating at a second frequency, the method comprising:
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receiving at least one time message from a time source;
accumulating counts in a free running counter in response to the second frequency;
advancing the internal time of the power monitoring device by a predetermined amount in response to said accumulation; and
adjusting said amount in response to indications from a time synchronization source;
wherein said time synchronization source comprises said time source; and
wherein said adjusting further comprises;
determining a difference between said time message and said internal time;
calculating a rate of change of said difference; and
adjusting said amount in response to said difference and said rate of change.
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88. A method of maintaining synchronization between a clock in a power monitoring device and a clock in an entity, the power monitoring device being coupled to a power system, the method comprising:
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monitoring at least one power parameter in the power system with the power monitoring device;
receiving an indication of time by the power monitoring device from said entity;
wherein said receiving further comprises;
receiving a message comprising a timestamp and an on time mark; and
recording a first value of a free running counter upon reception of said on time mark;
adjusting the rate of accumulation of time in the clock in the power monitoring device to track the clock in the entity;
recording a second value of said free running counter at a later time;
calculating a first difference in time between said second value and said first value, said timestamp being adjusted for said first difference;
adjusting the rate of accumulation in accordance with a second difference in time between said timestamp and a time in the clock in the power monitoring device; and
wherein said adjusting is further in accordance with a rate of change of said second difference from one reception to a next reception. - View Dependent Claims (89, 90, 91, 92)
recording a time of occurrence of a fault in the power system using the clock.
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92. The method of claim 89, further comprising:
recording a time of occurrence of a fault in the power system using the clock.
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93. A system for maintaining time synchronization between a plurality devices comprising:
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an entity, said entity comprising a master clock and said entity generating time synchronization messages;
a plurality of power monitoring devices coupled to a power system;
said power monitoring devices comprising;
a receiver operative to receive said time synchronization messages from said entity;
a processor operative to implement a clock;
wherein said processor adjusts a rate of accumulation of time in said clock in response to the reception of said time synchronization messages; and
wherein said processor monitors at least one power parameter in said power system;
wherein said processor is further operative to implement a free running counter;
said processor being operative to record the value of said free running counter when said messages are received and when said processor adjusts the rate of accumulation of time; and
wherein said processor adjusts said time synchronization message for the difference between said two free running counter values before said processor adjusts the rate of accumulation of time;
wherein said processor adjusts the rate of accumulation of time in said power monitoring device in accordance with a difference in time between said clock and said time synchronization message and further wherein said processor adjusts the rate of accumulation of time in accordance with a rate of change of the difference in time.
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Specification