System and method for a power meter to communicate through a power line
The disclosure relates to a meter for monitoring usage of power provided by a power transmission system to a site and a related method. The meter comprises: a meter module connected to a power feed associated with the transmission system to provide readings relating to the power; a connection to a household AC power supply providing power to the meter; a rectifier circuit connected to the AC power to generate a DC power signal; a voltage detection circuit to detect a low voltage condition where an output from the rectifier circuit drops below an operational threshold for the meter and to generate a low voltage signal upon detection of same; and a message generation module for receiving the low voltage signal and for generating a power loss message for transmission carried on a message carrier having on a carrier having frequency between approximately 2 MHz and 30 MHz.
1. A meter for monitoring usage of power provided by a power transmission system to a site, the meter comprising:
a meter module connected to a power feed associated with the power transmission system to provide readings relating to the power;
a connection to a household alternating current (AC) power supply providing power to the meter;
a rectifier circuit connected to the household AC power supply to generate a direct current (DC) power signal;
a voltage detection circuit to detect a low voltage condition where an output from the rectifier circuit drops below an operational threshold for the meter and to generate a low voltage signal upon detection of the low voltage condition; and
a communication module for receiving the low voltage signal and for generating a power loss message for transmission from the meter and carried on a message carrier having a carrier frequency between 2 MHz and 30 MHz to bridge a discontinuity in the power transmission system.
2. The meter for monitoring usage of power as claimed in claim 1 , further comprising:
a capacitive circuit to generate a voltage signal to replace the DC power signal when the household AC power supply fails.
3. The meter for monitoring usage of power as claimed in claim 1 , wherein:
the meter module maintains an internal clock for synchronization with a clock maintained by a head end.
4. The meter for monitoring usage of power as claimed in claim 3 , wherein:
the meter module adjusts the internal clock with the clock maintained by the head end when a discrepancy between the internal clock and the clock maintained by the head end is detected.
5. The meter for monitoring usage of power as claimed in claim 1 , wherein upon detection of the low voltage condition, the meter module:
tracks an unsynchronized time for the meter, the unsynchronized time beginning at a time associated with detection of the low voltage condition.
6. The meter for monitoring usage of power as claimed in claim 5 , wherein upon a re-boot of the meter, the meter module:
compares the unsynchronized time with a clock maintained by a head end.
7. The meter for monitoring usage of power provided by a power transmission system to a site as claimed in claim 1 , further comprising:
a disconnect manager module that controls the connection to the household AC power supply to connect and disconnect the meter from the household AC power supply based on a control action signal received by the disconnect manager module.
8. The meter for monitoring usage of power provided by a power transmission system to a site as claimed in claim 7 , wherein:
the disconnect manager module controls the connection to disconnect the meter from the household AC power supply when either an over-voltage or an over-current situation is detected on the household AC power supply.
9. The meter for monitoring usage of power provided by a power transmission system to a site as claimed in claim 7 , wherein:
the disconnect manager module receives and responds to simple network management protocol (SNMP) command signals sent from a head end of the power transmission system.
10. The meter for monitoring usage of power provided by a power transmission system to a site as claimed in claim 1 , wherein:
the disconnect manager module also controls the connection to disconnect the meter from the household AC power supply when a total power reading for the meter for a period of time exceeds a threshold.
11. The meter for monitoring usage of power provided by a power transmission system to a site as claimed in claim 1 , further comprising:
a schedule manager module that schedules for the meter, meter readings, power rate switching and synchronization of an internal clock with a clock maintained by a head end.
12. The meter for monitoring usage of power provided by a power transmission system to a site as claimed in claim 2 , further comprising:
a switching regulator circuit connected to the output of the rectifier circuit and the capacitive circuit, the switching regulator converting the DC voltage signal to a stepped down voltage signal for the meter module.
13. A method for monitoring usage of power provided by a power transmission system to a site at a meter, the method comprising:
rectifying a household alternating current (AC) power supply connected to the meter to generate a direct current (DC) power signal;
when the household AC power supply fails, detecting a low voltage condition where the DC power signal drops below an operational threshold for the meter; and
generating and sending a power loss message upon detection of the low voltage condition to the power transmission system from the meter carried on a message carrier having a carrier frequency between 2 MHz and 30 MHz to bridge a discontinuity in the power transmission system.
14. The method for monitoring usage of power provided by a power transmission system to a site at a meter as claimed in claim 13 , further comprising:
charging a capacitive circuit located between a rectifier circuit connected to the household AC power supply that generates a backup DC power signal for the meter; and
converting the DC voltage signal to a stepped down voltage signal for the meter.
15. The method for monitoring usage of power provided by a power transmission system to a site at a meter as claimed in claim 13 , further comprising:
maintaining an internal clock in the meter for synchronization with a clock maintained by a head end; and
adjusting the internal clock with the clock maintained by the head end when a discrepancy between the internal clock and the clock maintained by the head end is detected.
16. The method for monitoring usage of power provided by a power transmission system to a site at a meter as claimed in claim 13 , further comprising:
controlling the connection to the household AC power supply to connect and disconnect the meter from the household AC power supply based on a control action signal.
17. The method for monitoring usage of power provided by a power transmission system to a site at a meter as claimed in claim 16 , wherein:
the meter is disconnected from the household AC power supply when either an over-voltage or an over-current situation is detected on the household AC power supply.
18. The method for monitoring usage of power provided by a power transmission system to a site at a meter as claimed in claim 17 , further comprising:
disconnecting the meter from the household AC power supply when a total power reading for the meter for a period of time exceeds a threshold.
19. The method for monitoring usage of power provided by a power transmission system to a site at a meter as claimed in claim 17 , wherein:
the meter receives and responds to simple network management protocol (SNMP) command signals sent from a head end of the power transmission system.
20. The method for monitoring usage of power provided by a power transmission system to a site at a meter as claimed in claim 13 , further comprising:
scheduling for the meter, meter readings, power rate switching and synchronization of an internal clock with a clock maintained by a head end.