OHL-Corona - Corona and Field Effects

Danna Liebhaber

This guide identifies the mechanisms and analysis approach fo 1 r ac interference effects 2 on conductive linear facilities due to the operation of co-located electric transmission lines. The 3 common mechanisms for ac interference including magnetic inductive coupling, capacitive 4 coupling, and conductive voltage transfer through soil are discussed. Included are general 5 guidelines and considerations for performing detailed ac interference analyses, with sections 6 specific to the analysis of co-located pipeline and railroad facilities. This guide does not dictate 7 specific compliance limits, direct when an ac interference analysis must be performed, or cover 8 other issues that may need to be considered in joint-use corridors, such as effects due to 9 lightning striking the line or dc corrosion on structures.

The document defines terms related to the areas of corona and the electromagnetic environment of overhead power lines. Its scope is to define some of the most widely used terms specific to or associated with overhead power-line corona and fields. This includes terms used in electric and magnetic fields, ions, radio frequency propagation, electromagnetic signals and noise, audible noise, coupled voltages and currents, shock and perception, weather and related statistical terms, and measurements and measuring devices.

This standard establishes uniform procedures for the measurement of electric-field strength, ion-current density, conductivity, monopolar space-charge density and net space-charge density in the vicinity of high-voltage dc (HVDC) sources.

This recommended practice identifies specifications that should be provided to characterize instrumentation used to measure the steady state Root mean square (rms) values of magnetic and electric fields with sinusoidal frequency content in the range 10 Hz to 3 kHz in residential and occupational settings as well as in transportation systems. The dynamic ranges of interest are 0.01 ?T (0.1 mG) to 10 mT (100 G) and 1 V/m to 30 kV/m for magnetic and electric fields, respectively. In addition, this recommended practice ? Defines terminology. ? Describes general characteristics of fields. ? Surveys operational principles of instrumentation. ? Indicates methods of calibration. ? Identifies significant sources of error. While field meter specifications are identified, frequencies and field levels that should be used for calibration purposes, and limits on measurement uncertainty are not recommended in this standard. Rather, it is left to standards that describe measurement protocols for different environments to indicate specific calibration points and uncertainty requirements. However, sources of uncertainty during calibration and measurements are identified and guidance is provided on how they should be combined to determine total measurement uncertainty.

Definitions and usage of terms used in the measurement and analysis of corona and field effects of overhead power lines are presented in this standard. Correlation between measurements from equipment to standard terms is defined. Weather conditions such as rain, snow, fog, and drizzle are defined and their measurement standards discussed. The intent is to assist in correlating standard terms found in literature and requirements to standard engineering practice.

Uniform procedures for the measurement of power frequency electric and magnetic fields from alternating current 9ac) overhead power lines and for the calibration of the meters used in these measurements are established. The procedures apply to the measurement of electric and magnetic fields close to ground level. The procedures can also be tentatively applied (with limitations, as specified in the standard) to electric fields near an energized conductor or structure.

Uniform procedures are established for manual and automatic measurement of audible noise from overhead transmission lines. Their purpose is to allow valid evaluation and comparison of the audible noise performance of various overhead lines. Definitions are provided, and instruments are specified. Measurement procedure are set forth, and precautions are given. Supporting data that should accompany the measurement data are specified, and methods for presenting the latter are described.

A set of procedures to be followed to cope with reradiation of AM broadcast signals from power lines and other large metallic structures is provided. Reradiation may be described as electromagnetic waves radiated from a structure that has parasitically picked up a signal from the environment. A simplified prediction technique called a survey is described to determine which structures could possibly cause a problem. Guidelines for measurements and data analysis are included.

Specifications that should be provided to characterize instrumentation used to measure the steady state rms value of magnetic and electric fields with sinusoidal frequency content in the range 10 Hz to 3 kHz in residential and occupational settings as well as in transportation systems are identified. The instrumentation, recommended calibration methods, and sources of measurement uncertainty are also described.

The guide is based on industry practices, and guidelines for installation, maintenance and operation of irrigation equipment near or under power lines as they pertain to minimum distance to energized conductors and proper grounding to minimize nuisance shocks are presented. A variety of conditions in general terms is covered in this guide. Specific recommendations are made for the type of irrigation systems and power line parameters most commonly found.

Uniform procedures for the measurement of radio noise generated by corona from overhead power lines and substations are established in this standard. Measurement procedures in this standard are also valid for other power-line noise sources such as gaps and harmonics; however, most of the precautionary information, analysis, and data plotting techniques were written and developed primarily for corona discharges. The procedures are not valid for measuring transient radio noise sources that occur during breaker or disconnect switching operations. The procedures apply in the frequency range of 0.010 MHz to 1000 MHz; however, the emphasis is on the standard amplitude-modulation broadcasting (0.535 MHz to 1.605 MHz) and television broadcasting (54 MHz to 72 MHz, 76 MHz to 88 MHz, 174 MHz to 216 MHz, and 470 MHz to 698 MHz) bands. This standard is applicable to both ac and dc transmission lines and substations.

Uniform procedures for the testing of transmission line and station bus hardware in high voltage laboratories are established in this guide. Two tests are described: the first is a visual corona test, the second is a radio interference voltage (RIV) test. This guide does not address the permissible radio interference (RI) limits or specified corona extinction voltages. They are set either by regulation or by agreement between the utility and hardware manufacturer.

Uniform procedures are established for manual and automatic measurement of audible noise from overhead transmission lines. Their purpose is to allow valid evaluation and comparison of the audible noise performance of various overhead lines. Definitions are provided, and instruments are specified. Measurement procedures are set forth, and precautions are given. Supporting data that should accompany the measurement data are specified, and methods for presenting the latter are described.

Uniform procedures for the measurement of power frequency electric and magnetic fields from alternating current (ac) overhead power lines and for the calibration of the meters used in these measurements are established. The procedures apply to the measurement of electric and magnetic fields close to ground level. The procedures can also be tentatively applied (with limitations, as specified in the standard) to electric fields near an energized conductor or structure.

Industry practices and guidelines for installation, maintenance, and operation of irrigation equipment near or under power lines as they pertain to minimum distance to energized conductors and proper grounding to help minimize nuisance shocks are presented in this guide. A variety of conditions in general terms is covered in this guide. Specific recommendations are made for the type of irrigation systems and power line parameters most commonly found.

A set of procedures to be followed to cope with reradiation of AM broadcast signals from power lines and other large metallic structures is provided. Reradiation may be described as electromagnetic waves radiated from a structure that has parasitically picked up a signal from the environment. A simplified prediction technique called a survey is described to determine which structures could possibly cause a problem. Guidelines for measurements and data analysis are included.