Power quality utility metering system having waveform capture

An electrical energy meter for detecting line voltage variations in real-time, comprising:

• a voltage digitizing circuit operable to obtain analog line voltage information and generate digital line voltage information therefrom;
• a current digitizing circuit operable to obtain analog line current information and generate digital line current information therefrom;
• a metering circuit operable to receive the digital line voltage information and the digital line current information and generate metering information therefrom;
• a power quality circuit operable to
• receive the digital line voltage information and obtain magnitude information therefrom, the magnitude information representative of the magnitude of the line voltage, detect a variation in the magnitude of the line voltage relative to an acceptable voltage level, wherein said variation exceeds a first variation threshold,
• capture a first waveform in the form of a first set of digital line voltage information corresponding to the time when said variation is detected,
• detect a subsequent reduction in the variation of the magnitude of the line voltage such that the variation is equal to or less than the first variation threshold,
• capture a second waveform in the form of a second set of digital line voltage information corresponding to the time when the subsequent reduction in the variation is detected.

In an electrical energy meter containing means therein for metering a quantity of electrical energy generated by a supplier and transferred via a power supply line to a load of a customer during an energy measurement time interval, a method of monitoring variations in the metered quantity of electrical energy, comprising the steps of:

• a) sensing a line voltage transferred via the power supply line to the load during the energy measurement time interval;
• b) detecting a variation in a magnitude of the sensed line voltage relative to an acceptable voltage level, wherein said variation exceeds a first variation threshold;
• c) capturing a first waveform of the sensed line voltage corresponding to the time when said variation is detected;
• d) detecting a subsequent variation in the magnitude of the sensed line voltage relative to the acceptable voltage level, wherein said subsequent variation exceeds a second variation threshold;
• and
• e) capturing a second waveform of the sensed line voltage corresponding to the time when the subsequent variation is detected
• wherein the subsequent variation exceeds the acceptable voltage level when the variation exceeds the acceptable voltage level, and the subsequent variation is less than the acceptable voltage level when the variation is less than the acceptable voltage level.

An electrical energy meter for detecting line voltage variation in real-time, comprising:

• a voltage digitizing circuit operable to obtain analog line voltage information and generated digital line voltage information therefrom;
• a current digitizing circuit operable to obtain analog line current information and generate digital line current information therefrom;
• a metering circuit operable to receive the digital line voltage information and the digital line current information and generate metering information therefrom;
• a power quality circuit operable to
• receive the digital line voltage information and obtain magnitude information therefrom, the magnitude information representative of the magnitude of the line voltage,
• detect a variation in the magnitude of the line voltage relative to an acceptable voltage level, wherein said variation exceeds a first variation threshold,
• capture a first waveform in the form of a first set of digital line voltage information corresponding to the time when said variation is detected,
• detect a subsequent variation of the magnitude of the line voltage, wherein said subsequent variation exceeds a second variation threshold, and
• capture a second waveform in the form of a second set of digital line voltage information corresponding to the time when the subsequent variation is detected
• wherein the subsequent variation exceeds the acceptable voltage level when the variation exceeds the acceptable voltage level, and the subsequent variation is less than the acceptable voltage level when the variation is less than the acceptable voltage level.

In an electrical energy meter containing means therein for metering a quantity of electrical energy generated by a supplier and transferred via a power supply line to a load during an energy measurement time interval, a method of monitoring variations in the electrical energy, comprising the steps of:

• a) sensing a line energy signal transferred via the power supply line to the load during the energy measurement time interval;
• b) detecting a variation in a magnitude of the sensed line energy signal relative to an acceptable line energy level, wherein the variation exceeds a first variation threshold;
• c) capturing a first waveform of the sensed line energy signal corresponding to the time when said variation is detected;
• d) detecting a subsequent reduction in the variation of the magnitude of the sensed line energy signal such that the variation is equal to or less than the first variation threshold;
• and
• e) capturing a second waveform of the sensed line energy signal corresponding to the time when the subsequent reduction in the variation is detected.