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Understanding the Model Structure of a Watt-Hour Meter

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1. Overview of the Watt-Hour Meter Model

The watt-hour meter model is structured with a combination of letters and numbers in the format: category code + group code + design serial number + derivative number.

For instance, common household single-phase watt-hour meters include models like DD862-4, DDS97l, DDSY97l, etc.

Key Components of the Watt-Hour Meter Model:

• Category Code:
  • D – Electricity meter
• Group Code (Phase and Function):
  • Phase Lines:
    • D – Single-phase
    • S – Three-phase, three-wire
    • T – Three-phase, four-wire
  • Usage Classification:
    • D – Multi-function
    • S – Electronic
    • X – Reactive
    • Y – Prepaid
    • F – Multi-rate
• Design Serial Number: Represented by Arabic numerals; varies by manufacturer.

Examples:

• DD – Single-phase watt-hour meter (e.g., DD971, DD862)
• DS – Three-phase, three-wire active watt-hour meter (e.g., DS862, DS97l)
• DT – Three-phase, four-wire active watt-hour meter (e.g., DT862, DT971)
• DX – Reactive watt-hour meter (e.g., DX97l, DX864)
• DDS – Single-phase electronic watt-hour meter (e.g., DDS97l)
• DTS – Three-phase, four-wire electronic active watt-hour meter (e.g., DTS97l)
• DDSY – Single-phase electronic prepaid watt-hour meter (e.g., DDSY97l)
• DTSF – Three-phase, four-wire electronic multi-rate active watt-hour meter (e.g., DTSF97l)
• DSSD – Three-phase, three-wire multi-function watt-hour meter (e.g., DSSD97l)

2. Basic Current and Rated Maximum Current

• Basic Current: The current value that defines the primary characteristics of the watt-hour meter.
• Rated Maximum Current: The highest current value for which the meter maintains specified accuracy.

For example, a rating of 5(20)A indicates a basic current of 5A and a maximum current of 20A. For three-phase watt-hour meters, multiply the number of phases, such as 3×5(20)A.

3. Reference Voltage

The reference voltage determines the meter’s characteristics and is represented as follows:

• For a three-phase, three-wire meter: 3x380V
• For a three-phase, four-wire meter: 3×220/380V
• For a single-phase meter: The voltage at the terminal, e.g., 220V.

4. Reading a Two-Phase or Three-Phase Four-Wire Watt-Hour Meter

1. Reading Boxes:
   • If no red reading box is present, the black boxes indicate integer values, with the scale on the right showing decimal values.
   • If a red box is present, it displays decimal readings.
2. With or Without Current Transformer:
   • If no current transformer is used, the reading reflects actual consumption.
   • If a transformer is used, adjust the reading by the transformer’s multiplier. For example:
     • A 100/5 transformer has a multiplier of 20, a 200/5 has 40, and a 500/5 has 100.
     • Actual power consumption = meter reading × multiplier.
3. Transformer with Multiple Turns:
   • If the transformer is wound for multiple turns, actual power consumption = (transformer ratio / number of turns) × meter reading.

Generally, decimal places are omitted in billing calculations.

5. Understanding Kilowatt-Hour (kWh) Costs

One kilowatt-hour (kWh) represents the energy used by a 1000-watt appliance running for one hour. For instance, if 1 kWh costs 1 yuan, then a 1000-watt appliance will cost 1 yuan to operate for an hour.

For example, a rice cooker rated at 1000W and 220V will cost 1 yuan for each hour of use.