STS Prepaid Single-Phase Energy Meter AC

Document Version: V1.0

Intended Audience: Utilities, prepaid electricity vending operators, rental property managers, international project purchasers

Core Standard: IEC 62055-41 (STS)

1. Product Overview

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This product is a single-phase smart prepaid electricity meter that strictly complies with the STS (Standard Transfer Specification) international standard. STS is a globally applicable prepaid token transfer specification maintained by the STS Association and incorporated into the IEC 62055 series of international standards. It is currently used in more than 120 countries worldwide. This meter is designed based on the STS standard and uses a 20-digit numeric token to achieve secure, reliable electricity transfer and charge control, completely eliminating the drawbacks of traditional IC card media, such as easy loss, easy copying, and cumbersome operation. The product is aimed at residential users, rental apartments, commercial stalls, and prepaid electricity vending scenarios in emerging markets, providing an integrated metering and charge control solution with high security and high interoperability.

2. Why Choose the STS Standard?

2.1 Global Interoperability

STS is an open system specification. A recharge token generated by any STS-certified vending system (POS) can be used on any STS-certified meter, regardless of manufacturer. Utilities can freely mix and purchase vending terminals and meters from different brands, avoiding lock-in by a single supplier.

2.2 Financial-grade Security

The STS standard is designed to prevent the following fraudulent behaviors:

Stealing electricity by repeatedly entering digits through trial and error;

Generating fraudulent tokens from a stolen vending terminal;

Generating tokens outside the authorized area;

Reusing already-used tokens;

Tampering with the amount value of a legitimate token.

Each recharge token is generated using advanced encryption algorithms and can be used only once and is valid only for the target meter. STS Edition 2 and later versions have fully upgraded to a 128-bit encryption algorithm (EA11) and eliminated the old weak key mechanisms.

2.3 Media-free Recharge

Users do not need to carry a physical card. The recharge token is a 20-digit number that can be obtained through mobile apps, SMS, online banking, convenience store terminals, and other channels, and then entered on the meter keypad to complete recharge. This feature is particularly critical in emerging markets where mobile payment penetration is rising rapidly.

3. Core Functions and Technical Features

3.1 Metering and Charge Control

Function Item Specification:

Metering mode: Forward/reverse active energy metering, combined active energy supported

Charge control mode: STS standard token prepayment, low balance alarm, automatic trip when balance is exhausted

Overdraft function: Configurable overdraft energy quota supported

Event logging: Supports the most recent 50 recharge/bill inquiry records

Load control: Over-power, over-voltage, and under-voltage trip thresholds configurable

3.2 STS Token Compatibility

Supports the IEC 62055-41 application layer protocol, with a 20-digit numeric token carrier.

Compatible with the STS Association Key Management Center (KMC) key loading and update processes.

Supports standardized encoding of Supply Group Code (SGC) and manufacturer code, ensuring strict routing of cross-vendor tokens.

3.3 Security and Protection

ESAM security encryption chip: built-in hardware-level key storage and encryption/decryption engine to prevent side-channel attacks.

Terminal cover open detection: opening the meter terminal cover triggers event logging and optional alarm reporting.

Dual data backup: critical metering and charge control data use a checksummed dual-backup storage mechanism to ensure data is not lost after power failure or abnormal reset.

3.4 Communication and Expansion

Standard RS-485 or infrared local communication interface for parameter setting and data reading.

Optional micro-power wireless or power line carrier (PLC) communication module, supporting remote meter reading and charge control command delivery.

Communication protocol supports DLMS/COSEM.

4. Technical Parameters

Parameter Item: Specification

Rated voltage: 220 V AC (50 Hz)

Current specification: 5(60) A

Accuracy class: Active energy Class A (equivalent to IEC 62053-21 Class 1)

Token standard: IEC 62055-41 (STS)

Token length: 20 decimal digits

Display: LCD with backlight, supports cyclic display of balance, energy, and power

Protection rating: IP54 (indoor type)

Operating temperature: -25°C to +55°C

Design life: ≥10 years

5. Target Application Scenarios

5.1 Emerging Market Electricity Access

In sub-Saharan Africa, Southeast Asia, South Asia, and other regions, the STS standard is the de facto industry standard for prepaid electricity meters. This product can be directly connected to the local existing STS vending ecosystem, enabling plug-and-play without modifying existing vending infrastructure.

5.2 Rental Properties and Sub-metering

In apartments, shops, student dormitories, and other scenarios, owners or operators can use STS tokens to implement pay-before-use, completely eliminating the difficulty of arrears collection. When tenants change, there is no need to replace the meter; only a new token needs to be reissued to complete settlement and restart.

5.3 Utility Prepayment Projects

Suitable as a standard metering unit for utility prepayment projects, supporting large-scale deployment and centralized key management. The interoperability of STS allows utilities to procure meters from different suppliers in phases and batches, reducing procurement risk and cost.

6. Certification and Compliance

STS Association certification: The product has passed compliance testing by an STS-recognized laboratory, can be listed in the STS Association certified products directory, and is permitted to use the STS mark.

IEC 62055 series: Complies with the relevant requirements of IEC 62055-41 (application layer protocol) and IEC 62055-51/-52 (token carrier).

Metering performance: Complies with the active energy metering requirements of IEC 62053-21 or equivalent national standards.

7. Ordering and Support

Ordering information: Please provide the Supply Group Code (SGC) for the target market, manufacturer code configuration requirements, and communication module options (none/PLC/wireless). Before leaving the factory, each meter is written with a unique serial number and initial key, and is accompanied by a Key Load File for import into the vending system.

Technical support: STS token generation test vectors, vending system integration documentation, and key update process guide are provided.

Conclusion:

In the field of prepaid electricity meters, STS is not only a standard but also a global common language of security and interoperability. Choosing this product means choosing a mature technical system that has evolved for more than 30 years, covers more than 120 countries, and is continuously maintained by IEC. Whether for large-scale utility deployment or refined management in rental scenarios, this STS single-phase smart electricity meter can provide reliable, transparent, and future-oriented metering and charge control capabilities.

https://www.zhongyismart.com Wuxi Zhongyi Smart Technology Co., Ltd. focuses on R&D and production of smart water meters, energy meters and gas meters. Our products are available in over 90 countries across the globe. Feel free to contact Zhongyi Intelligent for inquiries about smart water meters, electricity meters and gas meters.