IEEE 81.2-1991 pdf download.IEEE Guide for Measurement of Impedance and Safety Characteristics of Large, Extended or Interconnected Grounding Systems.
Practical instrumentation methods are presented for measuring the ac characteristics of large, extended or interconnected grounding systems. Measurements of impedance to remote earth, step and touch potentials, and current distributions are covered for grounding systems ranging in complexity from small grids (less than 900m 2), with only a few connected overhead or direct burial bare concentric (2) neutrals, to large grids (greater than 20 000m 2), with many connected neutrals, overhead ground wires (sky wires), counterpoises, grid tie conductors, cable shields, and metallic pipes. This standard addresses measurement safety; earth-return mutual errors; low-current measurements; power-system staged faults; communication and control cable transfer impedance; current distribution (current splits) in the grounding system; step, touch, mesh, and profile measurements; the foot-equivalent electrode earth resistance; and instrumentation characteristics and limitations.
Keywords: Grounding systems, impedance, safety.
The purpose of IEEE 81.2-1991 is to present practical instrumentation methods that may be used for the measurement of impedance to remote earth, step and touch potentials, and current distributions of large extended or interconnected grounding systems ranging in complexity from small grids (less than 900 rn2), with only a few connected overhead or direct burial bare concentric neutrals, to large grids (greater than 20 000 m2), with many connected neutrals, overhead ground wires (sky wires), counterpoises. grid tie conductors, cable shields, and metallic pipes.
2. Scope
Test methods and instrumentation techniques used to measure the ac characteristics of large grounding systems include the following topics:
I) Measurement safety
2) Earth-return mutual errors
3) Low-current measurements
4) Power-system staged faults
5) Communication and control cable transfer impedance
6) Current distribution (current splits) in the grounding system
7) Step. touch, mesh, and profile measurements
8) The foot-equivalent electrode earth resistance
9) Instrumentation characteristics and limitations
Grounding electrodes consisting of a single ground rod, arrays of ground rods, tower footings, and many grids (if no external grounding is connected) can be measured. interference voltages pemitting. with methods outlined in IEEE Std 81-1983. Even if a large grid has an impedance phase angle of 18° the resistance component will be only 5% lower than its impedance.
Measurement of low-impedance grounding-system characteristics, with injection currents between 0.l—100A, using techniques described in Section 8. is generally preferred. Or, grounding-system parameters may be measured or verified under power-system conditions with the staged-fault methods of Section 9. Due to the diversity in station grounding configurations and the variety of possible test connections, this guide cannot narrowly define the test method for each application. The user must take responsibility for the adequacy of the method selected (see Section I 3. for a review of instrumentation components).IEEE 81.2-1991 pdf download.
IEEE 81.2-1991 pdf download
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