Power system time synchronization device and method for sequence of event recording
AssigneePower Measurement Ltd.
InventorsH. Kurtulus Ozcetin, Simon H. Lightbody, Peter M. Van Doorn, Rene T. Jonker
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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.
Claims93
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.
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:
- 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.
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:
- 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.
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:
- 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.
A system for maintaining time synchronization between a plurality devices comprising:
- 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.
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:
- 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.
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:
- 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.
A system for maintaining time synchronization between a plurality devices comprising:
- 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.
A system for maintaining time synchronization between a plurality devices comprising:
- 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.
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:
- 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.
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:
- 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.
A system for maintaining time synchronization between a plurality devices comprising:
- 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.
Dependencies are inferred from the claim text.