Electrical phase computation using RF media
Techniques for computing electrical phase of electrical metering devices are described. In an example, data indicating zero-crossing times at first and second metering devices is obtained. A time-difference between the zero-crossing times may be determined. In a first example, the time-difference may be based at least in part on calculations involving a first value of a first free-run timer on a first metering device, a second value of a second free-run timer on a second metering device, and a time of a transmission between the metering devices. In a second example, the time-difference may be based at least in part on calculations involving a start or end time of a time-slot of a spread spectrum radio frequency transmission scheme. A phase difference between the first zero-crossing and the second zero-crossing may be determined, based at least in part on the determined time-difference.
1. A method, comprising:
obtaining first data, at a processor of a first metering device and from a metrology unit of the first metering device, indicating a first zero-crossing of the first metering device at a first time;
sending, from a second metering device, a packet comprising second data indicating a second zero-crossing to a powerline communication (PLC) process and to a radio frequency (RF) process;
obtaining, at the first metering device, the packet comprising the second data indicating the second zero-crossing of the second metering device at a second time, wherein the packet comprises a free-run timer value defining a period between the second zero-crossing until a time of transmission of the packet;
recording, at the first metering device, a time of reception of the packet, the time of reception being based on the reception of a middle portion of the packet;
determining, by operation of the processor of the first metering device, a time-difference between the first zero-crossing and the second zero-crossing, wherein the time-difference is based at least in part on the first data and the second data and the time of reception of the packet; and
determining, by operation of the processor of the first metering device, a phase difference between the first zero-crossing and the second zero-crossing based at least in part on the determined time-difference.
2. The method of claim 1 , wherein:
the second data is obtained from a message sent to the first metering device by the second metering device.
3. The method of claim 1 , wherein determining the time-difference comprises:
determining a first time-difference between a start time or an end time of a time-slot of a spread spectrum RF transmission scheme and the first zero-crossing; and
determining a second time-difference between the start time or the end time of the time-slot and the second zero-crossing.
4. The method of claim 1 , wherein the time-difference is based at least in part on:
a first value of a first free-run timer on a first device representing a first elapsed time from the first zero-crossing to a start time of a time-slot or an end time of the time-slot of a spread spectrum RF transmission scheme; and
a second value of a second free-run timer on a second device representing a second elapsed time from the second zero-crossing to the start time of the time-slot or the end time of the time-slot of the spread spectrum RF transmission scheme.
5. The method of claim 1 , wherein:
the time-difference is based on a start time of a time-slot and not on an end time of the time-slot of a spread spectrum RF transmission scheme.
6. The method of claim 1 , additionally comprising:
generating a network topology comprising at least a first transformer powered by current having a first electrical phase and the first zero-crossing and a second transformer powered by current having a second electrical phase and the second zero-crossing; and
balancing a load of the first electrical phase with a load of the second electrical phase based at least in part on the network topology.
7. The method of claim 1 , wherein:
the first zero-crossing is measured at a first electricity meter;
the second zero-crossing is measured at a second electricity meter; and
the phase difference is either +120 degrees, −120 degrees, or zero degrees.
8. A network, comprising:
a first metrology unit of a first network node to obtain first data indicating a first zero-crossing at a first time;
a second metrology unit of a second network node to obtain a packet comprising second data indicating a second zero-crossing at a second time and to send zero-crossing information to a powerline communication (PLC) process and to a radio frequency (RF) process; and
a processor of the first network node to:
obtain the packet comprising the second data, the packet comprising at least one free-run timer value defining a period between the second zero-crossing until a time of transmission of the packet;
record, at the first network node, a time of reception of the packet, the time of reception being based on the reception of a middle portion of the packet; and
determine a time-difference between the first zero-crossing and the second zero-crossing, wherein the time-difference is based at least in part on:
the first data, the second data and the time of reception of the packet; and
a first value of a first free-run timer of a first device and a second value of a second free-run timer of a second device;
wherein the processor of the first network node is configured to determine a phase difference between the first zero-crossing and the second zero-crossing based at least in part on the determined time-difference.
9. The network of claim 8 , wherein the time-difference is based at least in part on:
an adjustment of at least one of the first time and the second time to compensate for time required to move through one or more network layers.
10. The network of claim 8 , wherein the time-difference is based at least in part on:
a time-slot of a spread spectrum radio frequency transmission scheme.
11. The network of claim 8 , additionally comprising:
starting or ending a timer based on a time-slot used in a spread spectrum RF transmission scheme.
12. The network of claim 8 , wherein:
the first zero-crossing is measured at a first electricity meter;
the second zero-crossing is measured at a second electricity meter; and
the phase difference is either +120 degrees, −120 degrees, or zero degrees.
13. The network of claim 8 , additionally comprising:
generating a network topology comprising at least a first transformer having voltage of a first electrical phase and the first zero-crossing and a second transformer having voltage of a second electrical phase and the second zero-crossing; and
balancing a load of the first transformer with a load of the second transformer based at least in part on the network topology.
14. The network of claim 8 , wherein:
the first zero-crossing and the second zero-crossing are based on a first electrical phase and a second electrical phase, respectively, that are offset by 120 degrees; and
the network balances a load of the first electrical phase and a load of the second electrical phase.
15. One or more non-transitory computer-readable media storing computer-executable instructions that, when executed, cause one or more processors to perform acts comprising:
sending, at a first network node, zero-crossing information to a powerline communication (PLC) process and to a radio frequency (RF) process;
obtaining, at the first network node, first data indicating a first zero-crossing at a first time at the first network node;
obtaining, from a second network node, a packet comprising second data indicating a second zero-crossing at a second time, the packet comprising a free-run timer value defining a period between the second zero-crossing until a time of transmission of the packet;
recording, at the first network node, a time of reception of the packet, the time of reception being based on the reception of a middle portion of the packet;
determining, by operation of a processor of the first network node, a time-difference between the first zero-crossing and the second zero-crossing, wherein the time-difference is based at least in part on the first data and the second data and the time of reception of the packet; and
determining, by operation of the processor of the first network node, a phase difference between the first zero-crossing and the second zero-crossing based at least in part on the determined time-difference.
16. The one or more non-transitory computer-readable media of claim 15 , wherein the acts additionally comprise:
starting or ending a timer based on a time-slot used in a spread spectrum RF transmission scheme.
17. The one or more non-transitory computer-readable media of claim 15 , wherein:
a first value of a first free-run timer on a first device represents a first elapsed time from the first zero-crossing to a start time of a time-slot or an end time of the time-slot of a spread spectrum RF transmission scheme;
a second value of a second free-run timer on a second device represents a second elapsed time from the second zero-crossing to the start time of the time-slot or the end time of the time-slot of the spread spectrum RF transmission scheme; and
the time-difference is a difference between the first value and the second value.
18. The one or more non-transitory computer-readable media of claim 15 , wherein:
determining the time-difference is based at least in part on a first value of a first free-run timer on a first device, a second value of a second free-run timer on a second device, and a start time of a time-slot or an end time of the time-slot of a spread spectrum RF transmission scheme.
19. The one or more non-transitory computer-readable media of claim 15 , wherein:
the first zero-crossing is measured at a first electricity meter;
the second zero-crossing is measured at a second electricity meter; and
the phase difference is either +120 degrees, −120 degrees, or zero degrees.
20. The one or more non-transitory computer-readable media of claim 15 , wherein the acts additionally comprise:
generating a network topology comprising at least a first transformer powered by current having a first electrical phase and the first zero-crossing and a second transformer powered by current having a second electrical phase and the second zero-crossing; and
balancing a load of the first transformer with a load of the second transformer based at least in part on the network topology.