Project brief
A multi-functional smart energy meter for residential and commercial billing, measuring per-phase voltage, current, active/reactive/apparent power, power factor, total harmonic distortion, and cumulative energy consumption. The meter connects via NB-IoT Cat-NB1 to a cloud metering server, supports STS prepaid token operations, and includes comprehensive tamper detection.
The case study explains how measurement and operational functions fit together. It adds no billing-accuracy certification or communications-volume evidence.
The engineering challenge
Combine phase-level metering, demand records, prepaid functions, and remote communications.
Engineering approach
- Separate electrical measurement from token handling and communications.
- Associate power-quality quantities with interval demand records.
- Route tamper events and meter data through local and network interfaces.
Features & capabilities
- 3-phase: voltage (±0.1% accuracy), current (0.001A–100A), energy (Class 0.5S)
- Power quality analysis: THD up to 63rd harmonic, power factor, unbalance
- NB-IoT Cat-NB1 (Cat-M fallback) cloud connectivity — <1KB/day data usage
- STS ANSI C12.19 compliant prepaid token encoder/decoder
- Tamper detection: cover open, magnetic field, earth fault, phase reversal
- Demand recording: 15-minute intervals, 12-month profile storage
- Optical port (IEC 62056-21) for local meter reading
- End-to-end AES-128 encrypted communication with metering server
Software & engineering tools
STM32G4, ATM90E36A 3-phase metering IC, SIM7080G NB-IoT module, custom 4-layer PCB, Altium Designer