Power plant Earthing Guidelines 1

[Flashover]

Hi folks
Besides the usual standards available, are there any sites where guidelines for earthing procedures in power plants are laid out. im espeically interested in following guidelines for construction of the earth grid during plant construction, bonding procedures and sizing of earthing ropes etc
many thanks
flashover

Flashover

 

[busbar]

Chapter 2 of ANSI/IEEE Std 142-1991 may be appropriate.

 

[jghrist]

Also see Chapter 9, Principal Design Considerations, Chapter 18, Construction of a Grounding System, and Chapter 19, Field Measurements of a Constructed Grounding System, in IEEE Std 80-2000, IEEE Guide for Safety in AC Substation Grounding.

 

[jbartos]

Suggestion: In addition to the previous posting, mesh voltage, step voltage and touch voltage are supposed to be calculated and known before any construction takes place. IEEE Std 80-2000 Annex D "Simplified step and mesh equations" is a good start.

 

[cuky2000]

Enclose are few advise to be considered:

a- Interconnection of the power plant ground grid with HV substation ground grid.
b- Provide a perimeter buried ground conductor 3 ft (1 m) around chain link fence or any metallic ground structure.
c- Ground grid at the center could be wider than at the perimeter where the maximum current is expected.
d- Check if 24 “ bellow grade works for you. Typically this could be a good starting.
e- Use 3” to 4” crushed stone (2000 to 3000 Ohm-m). Asphalt (10,000 Ohm-m) for road and other surface are excellent insulator.
f- Bring to the surface pigtails for equipment and structure grounding.
g- Copper bare conductor # 2/0 or 4/0 AWG are in many cases sufficient. Check the fraction of injected current to earth and time duration to operate protective devices.
h- Beware that power plant may have different surfaces (concrete, asphalt, crushed rock, native soil, etc). The allowable step and touch potentials are different been lower for concrete (~50 Ohm-m).
i- It is ok to use the foundation, piles or concrete slab as an auxiliary grounding electrode.
j- Special attention is requiring for cooling tower area and water retention pond if applicable.
k- Check possible transfer potentials (GPR) on railroad, extended metallic fences, phone line, etc. Proper isolation should be considered.
l- Isolated ground for DCS and sensitive electronic equipment.
m- Take advantage of powerful modeling tools software to model the entire grounding system could save significant resources and minimize the guess factor using conventional calcs.