What are the standards for calibration of online power quality monitoring devices?

Core Standards for Calibration of Online Power Quality Monitoring Devices

The calibration of online power quality monitoring devices follows a comprehensive standard system, encompassing mandatory national standards, industry technical specifications, international guidelines, and requirements for calibration methods and equipment. The following provides a structured overview with practical recommendations for real-world applications.

I. Core Domestic Standards

1. DL/T 1228-2023 – Technical Requirements and Test Methods for Online Power Quality Monitoring Devices

Status: Mandatory standard in China's power industry, replacing the 2013 edition, fully covering technical requirements, calibration methods, and testing procedures.

Key Provisions:

• Calibration Interval: ≤3 years under normal conditions; shortened to 1–2 years in harsh environments (e.g., high EMI, high temperature/humidity) or when device performance is unstable.

• Calibration Parameters: Voltage, current, frequency, harmonics (2nd–50th), interharmonics, flicker, three-phase unbalance, voltage sags/swells/interruptions. Calibration equipment must have accuracy better than 1/3 of the allowable error of the device under test (e.g., using a 0.05-class standard source).

• Functional Verification: Data sampling cycle, communication stability (e.g., IEC 61850 compatibility), and alarm threshold accuracy must be validated.

• Application: Calibration for monitoring devices in grid companies, power plants, and renewable energy grid-connection points.

2. GB/T 19862-2016 – General Requirements for Power Quality Monitoring Equipment

Role: National standard defining general technical requirements, including calibration methods, error limits, and environmental adaptability.

Key Requirements:

• Measurement Accuracy: RMS voltage/current error ≤ ±0.5%, frequency error ≤ ±0.01 Hz, harmonic amplitude error ≤ ±2% (Class A devices).

• Calibration Method: "Standard Source Injection Method" – comparing the output of a calibrated source with the device’s reading.

• Application: Reference for equipment selection and calibration in industrial users and research institutions.

3. GB/T 14549-1993 – Power Quality: Harmonics in Public Power Systems

Role: Defines allowable harmonic voltage and current levels in public grids, and specifies accuracy requirements for harmonic measurement instruments.

Calibration Focus:

• Harmonic Accuracy: A-class instruments require harmonic voltage error ≤ ±0.05% UN, current error ≤ ±0.15% IN. Must cover 2nd–50th harmonics.

• Immunity Testing: Validate device stability under harmonic-rich conditions to ensure immunity to field interference.

• Application: Harmonic mitigation projects and monitoring of industrial harmonic sources.

4. GB/T 17626 Series – Electromagnetic Compatibility (EMC) Testing

Environmental Robustness:

• GB/T 17626.2-2018: Electrostatic discharge immunity (contact ±6kV, air ±8kV).

• GB/T 17626.5-2019: Surge immunity (line-line ±2kV, line-earth ±4kV).

• GB/T 17626.6-2008: Conducted RF immunity (0.15–80 MHz).

Calibration Significance: Ensures measurement stability under high EMI conditions, preventing data drift due to interference.

Application: Calibration of devices in substations and industrial environments with strong electromagnetic interference.

II. International Standards

1. IEC 61000-4 Series – EMC Testing

Global Relevance:

• IEC 61000-4-2:2025: ESD immunity, includes guidance for wearable devices.

• IEC 61000-4-6:2013: Conducted RF immunity (0.15–80 MHz), standardized interference injection.

Advantage: Enables international recognition of calibration results.

Application: Exported equipment and cross-border power projects.

2. IEC 62053-21:2020 – Electricity Metering Equipment – Part 21: Static Active Energy Meters (Classes 0.2S and 0.5S)

High-Accuracy Reference:

• Error Limits: 0.2S class ≤ ±0.2%, 0.5S class ≤ ±0.5%.

• Calibration Method: "Standard Meter Method" – comparing readings from a high-accuracy reference meter and the device under test.

• Application: Trade settlement and high-precision research applications.

3. IEEE Std 1159-2019 – Guide for Monitoring Electric Power Quality

Technical Guidance:

• Defines measurement methods and data logging requirements for sags, harmonics, flicker, etc.

• Recommends the "Dual Standard Source Comparison Method" for cross-validation of device accuracy.

• Application: Reference for monitoring devices in North America and international engineering projects.

III. Calibration Methods & Equipment Standards

1. JJF 1848-2020 – Calibration Specification for Power Quality Monitoring Equipment

Metrological Traceability: National technical specification requiring calibration equipment uncertainty ≤ 1/3 of the device’s allowable error.

Key Steps:

• Visual inspection (labels, connectors).

• Preheating (30 min) and factory reset.

• Inject standard signals per DL/T 1228-2023.

• Calculate expanded uncertainty and issue calibration certificate.

Application: Basis for calibration in metrology institutes and third-party labs.

2. JJG 597-2016 – Verification Regulation for AC Electrical Energy Meter Test Equipment

Equipment Benchmark:

• 0.05-class source: voltage/current error ≤ ±0.05%, power error ≤ ±0.05%.

• Must support harmonic injection and phase adjustment.

Application: Selection and traceability of standard sources in calibration labs.

IV. Supplementary Standards for Special Scenarios

1. GB/T 24337-2009 – Power Quality: Interharmonics in Public Power Systems

• Defines interharmonic voltage limits (e.g., ≤1.5% for 19th interharmonic in 10kV+ grids).

• Validates measurement accuracy for non-integer harmonics (>50 Hz).

• Application: Renewable integration and industrial sites with variable frequency drives.

2. Q/GDW 10 J393-2009 – Technical Specification for Online Power Quality Monitoring Devices

• State Grid enterprise standard.

• Requires data storage ≥31 days, PQDIF format support.

• Validates data transmission accuracy (e.g., voltage deviation ≤ ±0.5%).

• Application: Calibration within State Grid systems.

V. Calibration Process & Compliance Recommendations

Qualification Requirements: Calibration labs must hold CNAS accreditation or provincial metrology authorization for legally valid results.

Dynamic Calibration Strategy:

• Standard interval: 3 years (per DL/T 1228-2023).

• Shortened to 1 year in harsh environments (e.g., chemical, metallurgical plants) or if historical drift > ±5%.

Record Keeping:

• Required: Calibration certificate, raw data, maintenance logs.

• Legal value: Used for regulatory compliance and incident investigation.

VI. Standard Prioritization & Application Strategy

• Domestic Projects: DL/T 1228-2023 + GB/T 19862-2016 + GB/T 14549-1993.

• International Projects: IEC 61000 series + IEEE Std 1159-2019.

• Special Cases:

• Harmonics: GB/T 14549-1993 + GB/T 24337-2009.

• EMC: GB/T 17626 + IEC 61000-4.

Summary

Calibration of online power quality monitoring devices must follow three principles: regulatory compliance, technical standardization, and scenario-specific adaptation. The core framework should be built on DL/T 1228-2023 and GB/T 19862-2016, enhanced by GB/T 14549-1993 and IEC 61000 for environmental robustness, and traceable via JJF 1848-2020. For specialized industries (e.g., renewables, healthcare), supplementary standards like GB/T 24337-2009 should be applied. The ultimate goal is accurate data, regulatory compliance, and international recognition.