| Type |
Advantages |
Disadvantages |
| Vertical rods |
Simple design. Easy to install in good soils. Hardware readily available.
Can be extended to reach the water table. |
High impedance. Hard to install in rocky soil. Step voltage on earth
surface can be high under large fault currents or during a direct
lightning strike. |
| Plates |
Can achieve low resistance contact in limited area. |
Most difficult to install. Should be installed vertically. |
Horizontal bare wires
(radials) |
Low impulse impedance. Good RF counterpoise when laid in star pattern.
|
Subject to resistance fluctuations with soils drying. Not recommended
with unstable soils. |
Incidental electrodes
(water pipes,
ufer grounds,
buried tanks) |
Can achieve very low resistance in certain applications. |
Little or no control over future alternations. Must be employed
with other electrodes, not as sole electrode. |
| Ring ground |
Straightforward design. Easy to install around existing
facility. Hardware readily available. Very efficient due to volume. |
Problems with asphalt and concrete around the facility?
Not desirable where large rocks are near surface. |
