Each region implements procedures to ensure the adequacy of the grounds of protection and will periodically review the grounding system in each facility to determine the appropriate size, length, and number (if parallel grounds are required) of grounds protection.
Regions must maintain and periodically update a list of maximum fault currents at each facility or location where Reclamation employees apply protection grounds.
These reviews should be performed every five years1 or earlier if changes in equipment or system conditions require a specific overhaul.
Earthing of cables and associated cables Earthing the equipment mus
meet the following requirements:
Capable of directing the maximum fault current that could occur at the earthed work site if the de-energized line or equipment is energized from any source and during fault resolution hours
Earth or jumper that is sized to conduct the maximum fault current available must be sufficient to safely conduct currents from other hazardous energy sources, including steady-state currents induced by electromagnetic coupling from lines or live equipment nearby.
Capable of withstanding the maximum available fault current including shifted DC-current due to waveform asymmetry for high X / R ratio values of fault circuit impedance Refer to Section 5 for cable ampacity information and section 6 for conductor sizing procedure.
Capable of withstanding a second activation within 30 cycles of inadvertent first activation.
Applied on the job site in such a way that the worker exposure or the body contact voltage does not exceed the values given in paragraph 4.1 as long as the earth cables conduct a fault current. Refer to Section 6 for the procedure to determine operator exposure voltage.
Connected directly to the equipment, bus or conductor to be grounded. No impedance or device (circuit-breaker, disconnector, transformer, siphon, etc.) must be authorized in series between the point of connection of the protective earth and the location of the contact by the workers.
Be easy to apply, meet the requirements of field application conditions, use minimal time and preparation for installation, and cover a wide range of uses. Standardization, where possible, is desirable at each site to minimize the number of sizes and types.
Manufactured as an assembly of appropriately sized components (conductor, ferrules, hose clamps) to withstand the thermal and electromechanical stresses imposed when conducting a fault current.
Stored and transported properly to prevent damage and maintained in good working order.
Equipment and terminal ground switches are not a substitute for reasons of personal protection. However, earth switches can be closed in parallel with protective grounds in order to reduce fault current through the earth cables and lower the exposure voltage of workers on the job site.
The earth cables must be sized for the maximum fault current available, without any reduction in current due to closed earth switches.
Certain types of earthing switches are designed for static earthing of equipment and do not withstand fault currents. Check the characteristics of the earth switch before closing in parallel with the protective earth.
Temporary removal of protective grounding system for unauthorized testing of de-energized equipment. Rather, protective grounds should be installed so that de-energized equipment under test is safely isolated from grounded circuits for the duration of the test.