There may be a serious risk of electric shock when carrying out construction in areas adjacent to the AC power system, for which it is the responsibility of professionals to be safe. The responsible person shall be fully aware of the correct grounding procedures and the hazardous effects of inductive coupling, capacitive coupling, fault currents and lightning on above- and below-ground structures, shall be equipped with relevant instrumentation and equipment, and shall have the authority to achieve and maintain safe working conditions. Grounding and bridging for construction safety depends on the size, form, and duration of the alternating current present. In each case, a professional should be analyzed, and safe operating procedures should be implemented throughout the construction operation.
When carrying out the construction of metal structures in the area affected by AC interference, the following minimum protection requirements shall be met:
The grounding resistance of the grounding electrode should be less than 30. In some cases, individual structural joints or end segments may require the installation of a grounding electrode prior to handling.
The temporary grounding electrode can be a grounding rod, screw sleeve or other suitable metal grounding body, which is used to reduce the AC voltage, but must not be connected to the adjacent utility power line grounding system, otherwise the probability of danger may be increased in the event of a switch shock, lightning or failure. If there is AC current flowing through this grounding system, it may also increase the normal static effect.
Connecting cables for jumper and grounding devices should have good mechanical strength and conductivity. Temporary connection cables can be made of stranded copper conductors with their cross-sectional area.
Temporary connecting cables to the structure and the grounding electrode should be reliably connected with a clamp that is under constant pressure and whose current carrying capacity is equal to or greater than that of the grounding conductor. The clamp should be installed securely so that it will not be accidentally disconnected. All permanent cable connections should be thoroughly inspected to ensure that they are mechanically strong, conductive and have an anti-corrosion layer before backfilling.
The grounding cable should first be connected to the grounding electrode and then reliably to the affected structure. The order of disassembly is reversed, and the connector connecting the grounding electrode should be disassembled last. Care should also be taken to operate with appropriate insulating tools or insulating gloves to reduce the risk of electric shock.
If a dangerous AC voltage is measured on both sides of the insulating flange or insulating joint, grounding or jumping should be performed on both sides of the joint or flange. If necessary, a permanent connection should be made before removing the temporary grounding.
Before removing the temporary grounding device, protective measures must be provided to control the effects of AC voltage on the structure, depending on the type of cathodic protection, the type of structure, and the expected amount of AC voltage. All temporary grounding devices should remain in place until the backfill is in place and until the permanent grounding has been connected.
When vehicles and other construction equipment are working in the vicinity of power lines, the current electrical safety regulations for operations in the area of high-voltage transmission lines shall be observed. Metal sheds or trailers, fence walls, or other temporary structures should be grounded if they are affected by disturbances.
The use of electrical insulation for above-ground accessories can reduce the click hazard in special occasions. It should be noted that wires that are not permanently connected to the structure are still highly likely to be subjected to electric shock, as there is no way to isolate and insulate the structure.