Metering Devices, Electromechanical and Solid-State - Acceptance Test

What it is

The metering-device acceptance test establishes a baseline record of the meter's identity, configuration, and baseline condition, and also verifies the meter's functional accuracy, before it is first energized and connected into the billing or monitoring chain. NETA ATS-2025 section 7.11.1 calls for a complete identification and visual inspection of the metering device - whether electromechanical or solid-state - capturing the manufacturer name, meter type, accuracy class, model or catalog number, meter form, potential transformer (PT) ratio if one is used in the circuit, equipment designation and location, and voltage rating. The inspection also includes a visual check for physical damage, corrosion, or loose fasteners that might affect operation or safety once the unit is in service. Beyond the identification and visual work, the section also calls for verifying the meter's accuracy against manufacturer's published data at one or more test points, calibrating the meter per the manufacturer's procedure, confirming the instrument multipliers (CT ratio, PT ratio, and register multiplier) applied to the raw reading, and verifying that the current- and voltage-transformer secondary circuits feeding the meter are intact.

Why it is performed

A metering device is installed to measure and record electrical energy consumption, power demand, or power factor for billing, load profiling, or system analytics. Before the meter is wired into a live circuit and begins recording readings that will drive billing or operational decisions, a baseline acceptance test confirms that the correct meter model was delivered to the correct location, that its accuracy class and configuration match the application it is about to serve, and that no damage in transit or storage has compromised its ability to measure accurately. Without that pre-energization check, the wrong meter could be installed undetected, or a damaged unit could begin recording invalid data from the moment it is switched on.

When it is performed

Acceptance: performed on every new electromechanical or solid-state metering device before it is first energized and integrated into service, as part of the electrical-acceptance-test sequence for the substation, switchgear, or panel into which it is being installed. The test is usually completed in the field during commissioning, or at the factory for shop-assembled units, and is documented in the project's acceptance test report before the meter is energized.

How it is typically performed

With the meter removed from service (or prior to energization if new), the meter is visually inspected for any signs of physical damage, corrosion, or loose internal or external fasteners that may have occurred during shipping or storage. The manufacturer, model number, meter type (electromechanical or solid-state), accuracy class, meter form, voltage rating, PT ratio if applicable, and equipment designation are recorded directly from the meter's nameplate and any accompanying documentation, and compared against the purchase specification or the metering scope for that location. Where the metering scope calls for it, the meter's accuracy is verified by applying one or more known reference values and comparing the meter's indicated reading against the applied value to compute a percent error, and the meter is calibrated per the manufacturer's published procedure, with as-found and as-left calibration error recorded. The instrument multipliers - CT ratio, PT ratio, and register or display multiplier - are verified against the system design, and the current- and voltage-transformer secondary circuits are checked to confirm they remain intact. The inspection, accuracy, calibration, and identification data are logged on the acceptance test form as a record of what was received, its condition, and its verified performance at the moment of installation.

What gets recorded

Manufacturer name, meter type (electromechanical or solid-state), accuracy class, model or catalog number, meter form designation, PT ratio (if used), equipment location and designation, voltage rating in volts, visual-inspection findings (presence or absence of physical damage, corrosion, loose parts), and the date and initials of the inspector. For units where meter accuracy and calibration are verified: the applied reference value, the meter's indicated reading, and the computed percent error at each test point; the calibration error as-found and as-left; the CT ratio, PT ratio, and register multiplier applied; and confirmation that the current- and voltage-transformer secondary circuits are intact. Any discrepancies between the meter delivered and the specification or a prior purchase order are noted on the form for resolution before the meter is energized.

How results are evaluated

NETA ATS-2025 section 7.11.1 frames the acceptance test as a confirmation that the meter's identification data - manufacturer, type, accuracy class, model, form, PT ratio, and voltage rating - align with the application and installation location, and that the unit is free of visible damage that would prevent accurate measurement. Where accuracy and calibration are verified, the meter's accuracy and calibration error at each test point must fall within the manufacturer's published tolerances, and the instrument multipliers and CT/VT secondary-circuit integrity must match the system design; NETA ATS-2025 does not set an independent numeric accuracy tolerance for this section, deferring instead to the manufacturer's own specification. If the meter found in the field does not match the specification, exhibits physical damage, or fails the accuracy or calibration check, the unit is removed from service and replaced or repaired before acceptance is granted. See the purchased standard for the complete identification, inspection, and test requirements.