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PD CISPR TR 18 — Radio Interference Characteristics of Overhead Power Lines and High-Voltage Equipment Technical Report Series
Radio Interference Characteristics of Overhead Power Lines and High-Voltage Equipment
⚡ PD CISPR TR 18 is the British Standards Institution (BSI) Published Document implementing the International Special Committee on Radio Interference (CISPR) technical report CISPR/TR 18, systematically describing the radio interference (radio noise) characteristics of overhead power lines and high-voltage equipment. Prepared by Subcommittee GEL/210/11 “EMC product standards” under UK technical committee GEL/210 “EMC — Policy committee,” it is classified under ICS 29.240.20 (overhead lines) and 33.100.01 (general electromagnetic compatibility), superseding the withdrawn BS 5049 series. It covers description of phenomena, measurement methods and limit-determination procedures, and a code of practice for minimising radio-noise generation — a key basis for electromagnetic-environment design and EMC compliance of transmission lines.
💡 High-voltage lines generate broadband radio noise during corona discharge, which can interfere with broadcasting, television, and communications reception. CISPR TR 18 quantifies this “invisible electromagnetic pollution” into engineering metrics that can be predicted, measured, and suppressed.
1. Series Structure and Overall Framework 📌
The PD CISPR TR 18 series consists of 3 parts, corresponding respectively to “description of phenomena,” “measurement and limits,” and “suppression practice” — forming a complete chain from mechanism understanding to engineering application.
| Part | Year | Title | Core Content |
|---|---|---|---|
| PD CISPR/TR 18-1 | 2010 | Description of phenomena | Describes the generation mechanisms, physical characteristics, and statistical distribution of radio noise from lines and HV equipment |
| PD CISPR/TR 18-2 | 2010 | Methods of measurement and procedure for determining limits | Specifies measuring instruments, on-site measurement methods, and limit-determination procedures |
| PD CISPR/TR 18-3 | 2010 | Code of practice for minimizing the generation of radio noise | Provides engineering practice for controlling radio noise and protecting broadcasting and television reception |
⚠️ This series is a Technical Report (TR) of reference nature, not a mandatory limit document. Always reference the current BSI version and consider its linkage with relevant EMC product standards and grid design codes.
2. Description of Noise Phenomena: Part 1 Mechanism 🎛️
Part 1 systematically describes the physical phenomena of radio noise from power lines, centred on conductor corona and partial discharges in high-voltage equipment:
- Noise-field formation mechanism: corona discharge produces pulse currents at the conductor surface, radiating an electromagnetic field into the surroundings as noise.
- Frequency-domain characteristics: the noise spectrum spans a wide band from low frequency (0.15 MHz) to very high frequency (300 MHz), attenuating with increasing frequency.
- Lateral profile: noise intensity decreases with lateral distance from the line, forming a lateral attenuation distribution.
- Seasonal and weather statistics: noise levels vary with weather (rain, snow, fog) and season, showing statistical distribution characteristics.
Part 1 also describes the influence of external parameters (conductor surface gradient, altitude, humidity, etc.) on noise level, providing the physical basis for prediction models.
3. Measurement Methods and Limit Determination: Part 2 Procedures 📏
Part 2 specifies methods for measuring radio noise, including instrument requirements, on-site measurement procedures, and limit-determination methods:
| Measurement Element | Description |
|---|---|
| Measuring instruments | Use a standard quasi-peak CISPR measuring receiver, considering its response characteristics |
| Low-frequency measurement (0.15–30 MHz) | Specifies on-site measurement layout and methods for lines in the low-frequency band |
| High-frequency measurement (30–300 MHz) | Specifies methods covering television and FM broadcasting bands |
| Statistical evaluation | Statistically evaluates line noise levels to give representative values |
Part 2 also specifies the additional information to be included in measurement reports and the requirements for measuring HV equipment (e.g., substations, insulators).
4. Code of Practice for Noise Suppression: Part 3 Engineering Guidance 🛠️
Part 3 provides a Code of Practice for controlling radio noise and protecting broadcasting and television reception, giving suppression measures from both design and operation-maintenance perspectives:
- Conductor corona suppression: choose appropriate conductor diameter, bundle configuration, and surface gradient to reduce conductor corona.
- Hardware corona suppression: optimise hardware shapes and use corona rings / grading rings to reduce point discharges.
- Insulator surface discharge: control surface discharges on clean or slightly polluted insulators, with special measures for heavily polluted ones.
- Bad contacts and microsparks: address sparking and microsparks from bad contacts and commutation effects by improving connections and maintenance.
- In-service defects: detect and remedy defects on lines and associated equipment in service to suppress intermittent noise.
Part 3 also gives methods for predicting the reference level of an overhead line, supporting noise-impact assessment at the design stage.
✅ Part 1 explains “what it is” (mechanism and characteristics), Part 2 “how to measure” (measurement and limits), and Part 3 “how to prevent” (suppression practice) — together forming a complete technical system for transmission-line radio-noise control.
5. Engineering Practice and Application Notes 🛠️
- 🔍 Line design stage: predict the reference level per Part 3 and optimise conductor and hardware design to control noise at source.
- 🔧 Environmental assessment: compare noise levels with broadcasting, television, and communications reception quality requirements to assess electromagnetic impact.
- 📊 Site acceptance and monitoring: perform on-site measurements per Part 2 to verify that line noise meets limits.
- 📋 Alignment with EMC standards: the series works with CISPR emission/immunity standards and grid design codes to form a complete EMC system.
6. Frequently Asked Questions ❓
❓ Q: What is the main source of radio noise from transmission lines?
A: Mainly conductor corona, followed by discharges on hardware and insulator surfaces and microsparks from poor contacts. The spectrum spans low to very high frequencies.
A: Mainly conductor corona, followed by discharges on hardware and insulator surfaces and microsparks from poor contacts. The spectrum spans low to very high frequencies.
❓ Q: How does noise level vary with weather?
A: Wet weather (rain, snow, fog) enhances corona, raising noise levels; clear dry weather gives lower levels. Therefore evaluation must be statistical.
A: Wet weather (rain, snow, fog) enhances corona, raising noise levels; clear dry weather gives lower levels. Therefore evaluation must be statistical.
❓ Q: How can line radio noise be reduced?
A: Reduce surface gradient by increasing conductor diameter, using bundle conductors, optimising hardware shapes, and adding corona rings; improve connections and maintenance to reduce discharge points.
A: Reduce surface gradient by increasing conductor diameter, using bundle conductors, optimising hardware shapes, and adding corona rings; improve connections and maintenance to reduce discharge points.
🔍 Q: Why is this series published as a Technical Report (TR)?
A: Because it is a CISPR technical report providing background information and guidance rather than mandatory limits, for reference in engineering design and EMC assessment.
A: Because it is a CISPR technical report providing background information and guidance rather than mandatory limits, for reference in engineering design and EMC assessment.