1. Understanding IEC 60044-2 Standard

• Scope: IEC 60044-2 (Second edition, 2018) is part of the IEC 60044 series, specifying technical requirements for voltage transformers (VTs) used in electrical power systems.

• Focus: Applies to low-voltage (LV) voltage transformers (rated primary voltage ≤ 1 kV) for measuring, protecting, and controlling power systems.

• Key Objectives:

• Ensure safety, accuracy, and reliability in voltage measurement and protection applications.

• Define test methods, performance classes, and marking requirements for LV VTs.

2. Core Requirements for LV Transformer Compliance

2.1 Rated Values

• Rated Primary Voltage (U₁n): Must match the system voltage (e.g., 230V, 400V, 690V for LV grids).

• Rated Secondary Voltage (U₂n): Typically standardized as 100V (for three-phase systems) or 230V (for single-phase systems).

• Rated Frequency: 50/60 Hz (matched to the grid frequency).

2.2 Accuracy Classes

• LV VTs are classified by their voltage error and phase displacement error at rated load and power factor (cosφ = 0.8 lagging).

• Common Accuracy Classes (for measuring VTs):

  Accuracy Class	Maximum Voltage Error (%)	Maximum Phase Displacement (minutes)
  0.1	±0.1	±5
  0.2	±0.2	±10
  0.5	±0.5	±20
  1	±1.0	±40

• Protection VTs: May use classes like 3P or 6P (allow higher errors but emphasize robustness during fault conditions).

2.3 Insulation and Safety

• Dielectric Strength:

• Must withstand voltage tests (e.g., 2 kV AC for 1 minute between primary and secondary windings, or as specified by the standard).

• Creepage and clearance distances must comply with IEC 60664-1 for LV systems.

• Thermal Stability:

• Temperature rise limits depend on insulation class (e.g., Class B: ≤80 K, Class F: ≤105 K).

• Adequate cooling design to prevent overheating under continuous load.

2.4 Environmental and Mechanical Requirements

• Temperature Range: Operational temperature typically -25°C to +55°C (may vary by application).

• Vibration and Mechanical Stress: Designed to withstand transportation and operational vibrations (e.g., IEC 60068-2-6 for mechanical shock and vibration tests).

• IP Rating: Enclosure protection (e.g., IP20 for indoor use, IP54 for outdoor/harsh environments).

2.5 Testing and Certification

• Type Tests:

• Accuracy tests under rated and extreme conditions (e.g., 80–120% of rated voltage).

• Impulse voltage tests (for transient protection).

• Thermal stability and temperature rise tests.

• Routine Tests:

• Winding resistance measurement.

• Dielectric withstand tests.

• Polarity and phase displacement checks.

• Certification: Compliance must be verified by an accredited laboratory, with a test report issued.

3. Design Considerations for Compliance

3.1 Winding and Core Design

• Core Material: Use high-permeability silicon steel or amorphous metal to minimize hysteresis and eddy current losses (critical for accuracy).

• Winding Configuration:

• Single-phase or three-phase (e.g., star/delta connections for three-phase VTs).

• Shielding between primary and secondary windings to reduce electromagnetic interference (EMI).

3.2 Voltage Regulation and Load Effects

• Burden Management: Secondary load (impedance) must not exceed the rated burden (e.g., 10 VA, 25 VA) to maintain accuracy.

• Voltage Regulation: Design with low leakage reactance to minimize voltage drop under varying loads.

3.3 Harmonic Performance

• For renewable energy applications (e.g., solar/wind inverters), VTs must handle harmonic-rich signals without significant error degradation.

• Core saturation margins should be designed to avoid nonlinearity at high harmonic frequencies.

3.4 Marking and Documentation

• Mandatory Markings on the Transformer:

• Manufacturer name/model.

• Rated primary/secondary voltage, frequency, and accuracy class.

• IP rating and insulation class.

• IEC 60044-2 compliance symbol (e.g., “Complies with IEC 60044-2”).

• Technical Documentation:

• Test reports (type and routine tests).

• Installation and maintenance manuals.

• Schematic diagrams (wiring, polarity).

4. Applications of IEC 60044-2 Compliant LV Transformers

• Power Distribution Grids: Voltage measurement in LV switchgear and distribution panels.

• Renewable Energy Systems:

• Solar/wind inverters: Monitoring output voltage for grid synchronization.

• Microgrids: Voltage regulation in hybrid solar-storage systems.

• Industrial Automation: Process control systems requiring accurate voltage sensing.

• Protective Relaying: Feeding voltage signals to overvoltage/undervoltage relays in LV systems.

5. Challenges in Compliance

• Harmonic Distortion: High harmonic content in renewable energy systems can cause core saturation and accuracy degradation.

• Temperature Variations: Extreme temperatures affect winding resistance and core losses, impacting accuracy.

• Miniaturization: Compact LV transformer designs may compromise insulation spacing or cooling, requiring innovative materials (e.g., nanocomposite insulators).

6. Compliance Tips for Manufacturers

1. Early Testing: Conduct prototype testing against IEC 60044-2 early in the design phase to identify issues (e.g., core losses, insulation weaknesses).

2. Material Selection: Use low-loss cores and high-temperature insulation to meet efficiency and thermal requirements.

3. Modular Design: Enable easy replacement of components (e.g., windings) for retesting or upgrades.

4. Software Tools: Use finite element analysis (FEA) to simulate magnetic fields and optimize core/winding layouts for accuracy.

7. Related Standards and Harmonization

• IEC 61869 Series: Standards for instrument transformers (complementary to IEC 60044).

• IEEE C57.13: U.S. equivalent standard for voltage transformers (LV/MV/HV).

• EN 61969: Transformers for wind turbine applications (may reference IEC 60044-2 for VT requirements).

Conclusion