ELECTRIC METERING

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REQUIREMENTS AND USE

Metering electrical energy involves use of many types of meters and associated devices. In many cases, totalizing of kilowatthour (kWh) usage during a time interval is adequate for studies and billing purposes. Many more parameters of electric power can be measured to provide insight into electrical demand requirements. Some parameters measured to complete a more accurate and informative analysis of an electrical system are as follows:

• Voltage
• Ampere
• Phase angle
• Kilowatt
• Kilowatthour
• Onpeak kW demand
• Mid-peak kW demand
• Offpeak kW demand
• Time-of-use
• Power factor
• Real power
• Apparent power

IMPORTANCE OF METERING: Metering electrical energy serves three important purposes: provides energy audit data, identifies distribution of costs to users, and sets standards to be used to evaluate performance. Meter installation can be costly, but the return in savings usually is worth the investment. Based on data from 1980, the cost of installing a kilowatthour meter ranges between $300 and $1,000.

1. Audits: To obtain useful information for an audit, a survey requires a metering system and a formally standardized method of collecting and reducing data. Percentages of energy efficiency and pinpointing inefficient equipment are results that an audit will produce. An energy profile will do the following:

• Aid in establishing and refining energy use by department or area.
• Establish and improve accountability.
• Measure cost reductions.
• Determine equipment capabilities and load factors.
• Help in planning facility modifications and expansions.
• Provide data to analyze variance from standards.
• Identify successful energy management projects.

2. Accurate Charges: Accurate distribution of charges to energy users is needed. Contrary to limited metering of the past, sufficient and discriminate placement of meters today allows the identification and charging of individual users. Items to take into consideration when planning for metering system are:

• Sufficient money to monitor the desired number of circuits.
• Staff with time and qualifications to read meters.
• Placement of conductors for efficient connection to potential and current transformers.
• Loads that cannot be shut down for meter installation.
• Placement of meters for easy access in safe locations.
• Design engineers knowledgeable in metering system requirements.
• Training of maintenance personnel.
• Funding for maintenance and spare parts.
• Cross reference method to determine need for meter calibration.

3. Standards: Energy consumption standards can be developed from historical data. Once a standard has been set, periodic monitoring and plotting may reveal a variance that requires further investigation.
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