TECHNICAL FIELD

This disclosure relates to electric meters generally and, more particularly, to electric meters that can measure the length of time of electrical power interruptions in power lines that the electric meter monitors.

BACKGROUND

Electricity meters are devices that measure and/or meter aspects of energy provided to a load. The load may be a residence, business, or even part of a larger electricity distribution system. Commonly available meters include electromechanical meters and electronic meters. Electromechanical meters employ a rotating disk that rotates in response to electric and magnetic fields induced by the electricity passing to the load. As is known in the art, the disk rotation speed is a function of the amount of electricity delivered to the load. Mechanical counters accumulate the number of disk rotations, which is indicative of energy consumed by the load. In some cases, an electromechanical meter can employ processing circuitry to perform additional operations with the consumption information provided by the rotating disk.

Electronic meters typically employ processing circuitry instead of the rotating disk and mechanical counters. In such meters, sensors within the meter detect the voltage and current that is delivered to the load. Circuitry within the meter converts the sensed voltage and current into digital values. Processing circuitry then employs digital signal processing to calculate consumed energy, among other things, from the digital values. Electronic meters provide greater flexibility in the types of energy consumption information that they may calculate, track, and store.

During operation, the electric lines that an electric meter monitors may experience interruptions in providing power due to power outages that occur in a power grid. In many instances, electrical utilities are required to provide aggregate information about an average amount of time that different portions of a power grid experience an interruption to electrical power. This measurement can refer to an average amount of time that the power grid experiences a power loss during a predetermined time span, such as a monthly or annual time span, where of course in many instances only a portion of the power grid experiences an interruption at any one time. One example of such a measurement is the System Average Interruption Duration Index (SAIDI), which is expressed mathematically as:

SAIDI=∑Ui⁢NiNT⁢
where Nirefers to a total number of customers at a particular location i, Uiis the total duration of power interruptions at the location i, and NTis the total number of customer locations. The SAIDI measurement is generally calculated over a one year period to provide an average duration of power interruptions for a power grid that provides power to multiple locations and customers.

In some existing electrical systems, interruptions to electrical power delivery are monitored from a centralized system, but while such monitoring can identify large-scale power outages effectively, the monitoring process may not identify smaller-scale power outages that have shorter durations accurately. Consequently, improvements to systems that monitor the consumption of electrical power to increase the accuracy of measuring periods of power interruption would be beneficial.

SUMMARY

In one embodiment, a method of identifying power interruptions has been developed. The method includes receiving, with an external monitoring system, a load profile from an electric meter that includes at least one of an accumulated frequency measurement and an accumulated number of zero crossing events that the electric meter records in an AC power signal during a predetermined monitoring period, and identifying, with a processor in the external monitoring system, a total duration of at least one power interruption during the predetermined monitoring period based on at least one of a deviation of the accumulated frequency measurement in the load profile from a predetermined accumulated frequency value or a deviation of the accumulated number of zero crossing events in the load profile from a predetermined number of zero crossing events during the predetermined monitoring period.

In another embodiment, a method of operating an electric meter to identify power interruptions has been developed. The method includes operating, with a battery in the electric meter, at least one component in the electric meter in response to a first power interruption in a power line connected to the electric meter, identifying, with a control device in the electric meter, a duration of the first power interruption based on a duration of a time on battery while operating with the battery in the electric meter after the first power interruption, and transmitting, with an output device in the electric meter, a message including a total duration of power interruptions including the duration of the first power interruption to an external monitoring system.

In another embodiment, a system for monitoring power interruptions has been developed. The system includes an electric meter. The electric meter includes a voltage sensor, an output device, and a control device operatively connected to the voltage sensor and the output device. The control device is configured to monitor an AC power signal in a power line that is connected to the electric meter using the voltage sensor, identify at least one of an accumulated frequency measurement of the AC power signal during a predetermined monitoring period or an accumulated number of zero crossing events in the AC power signal during the predetermined monitoring period, and transmit a load profile that includes at least one of the accumulated frequency measurement and the accumulated number of zero crossing events with the output device to an external monitoring system to enable the external monitoring system to identify a total duration of at least one power interruption in the AC power signal that occurs during the predetermined monitoring period.

