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MULTIFUNCTION POWER METER

Multi-function or extended function refers to a meter that can measure reactive or apparent power (e.g., kvar or kVA) in addition to real power (kW). By virtue of their designs, many electronic meters inherently measure the quantities and relationships that define reactive and apparent power. It is a relatively simple step for designers to add meter intelligence to calculate and display these values.

VOLTAGE RANGING AND MULTIFORM METER

Electronic meter designs have introduced many new features to the watt-hour metering world. Two features, typically found together, offer additional flexibility, simplified application, and opportunities for reduced meter inventories for utilities.

• VOLTAGE RANGING: Many electronic meters incorporate circuitry that can sense the voltage level of the meter input signals and adjust automatically to meter correctly over a wide range of voltages.

For example, a meter with this capability can be installed on either a 120 volt or 277 volt service.

• MULTIFORM: Meter form refers to the specific combination of voltage and current signals, how they are applied to the terminals of the meter, and how the meter uses these signals to measure power and energy. For example, a Form 15 meter would be used for self-contained application on a 120/240 volt 4-wire delta service, while a Form 16 meter would be used on a self-contained 120/208 volt 4-wire wye service. A multiform 15/16 meter can work interchangeably on either of these services.

SITE DIAGNOSTIC METER

Newer meter designs incorporate the ability to measure, display, and evaluate the voltage and current magnitudes and phase relationships of the circuits to which they are attached. This capability offers important advantages:

• At the time of installation or reinstallation, the meter analyzes the voltage and current signals and determines if they represent a recognizable service type.

• Also at installation or reinstallation, the meter performs an initial check for wiring errors such as crossed connections or reversed polarities. If it finds an error, it displays an error message so that corrections can be made.

• Throughout its life, the meter continuously evaluates voltage and current conditions. It can detect a problem that develops weeks, months, or years after installation, such as tampering or deteriorated CT or VT wiring.

• Field personnel can switch the meter display into diagnostic mode. It will display voltage and current magnitudes and phase angles for each phase. This provides a quick and very accurate way to obtain information on service characteristics.

If a diagnostic meter detects any error that might affect the accuracy of its measurements, it will lock its display in error mode. The meter continues to make energy and demand measurements in the background. However, these readings cannot be retrieved from the meter until the error is cleared. This ensures the error will be reported the next time someone tries to read the meter.

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