pos
New member
- Location
- Boise, Idaho
Hello...first time poster, long time viewer and this forum has been very helpful.
My question is about grounding of duct banks and manhole/handhole/vault in the airfield where FAA has jurisdiction. FAA standard for duct bank require installation of a counterpoise (or guard wire) approximately 4-12 inches above the duct bank (concrete encased) and at every 500 feet the counterpoise is bonded to a ground rod. All of this is done for lightning protection. At the manhole structure, the counterpoise and manhole (including all metallic parts and ground bus) is bonded to three ground rods installed around the perimeter of the structure. This type of grounding is performed to airfield lighting, power (all voltages) and communication systems.
My problem is the airport has slighting different standard for grounding medium voltage duct banks. For medium voltage duct banks, a bare cu conductor is encased inside the duct bank, and runs the length of the duct bank before it is bonded to the ground bus and all metallic parts of the manhole structure. At no point along the duct bank is the cu conductor bonded to ground rods like the FAA counterpoise system. However, at the manhole structure, both the counterpoise and the (airport's) bare cu conductor are bonded in the same way.
Does anyone foresee an issue with installing both the counterpoise and the bare cu conductor for the same MV power duct bank. Could there be a potential difference created by the two type of ground systems anywhere along the duct bank path. Is it even necessary to have the bare cu conductor if the counterpoise system is already there? This is in the airfield, so FAA has jurisdiction and their counterpoise system requirement will be enforced. I am just wondering about the additional bare cu conductor and whether that is necessary or will it create a more hazardous (grounding) environment.
Please let me know what you think. Appreciate any response. Thank you.
My question is about grounding of duct banks and manhole/handhole/vault in the airfield where FAA has jurisdiction. FAA standard for duct bank require installation of a counterpoise (or guard wire) approximately 4-12 inches above the duct bank (concrete encased) and at every 500 feet the counterpoise is bonded to a ground rod. All of this is done for lightning protection. At the manhole structure, the counterpoise and manhole (including all metallic parts and ground bus) is bonded to three ground rods installed around the perimeter of the structure. This type of grounding is performed to airfield lighting, power (all voltages) and communication systems.
My problem is the airport has slighting different standard for grounding medium voltage duct banks. For medium voltage duct banks, a bare cu conductor is encased inside the duct bank, and runs the length of the duct bank before it is bonded to the ground bus and all metallic parts of the manhole structure. At no point along the duct bank is the cu conductor bonded to ground rods like the FAA counterpoise system. However, at the manhole structure, both the counterpoise and the (airport's) bare cu conductor are bonded in the same way.
Does anyone foresee an issue with installing both the counterpoise and the bare cu conductor for the same MV power duct bank. Could there be a potential difference created by the two type of ground systems anywhere along the duct bank path. Is it even necessary to have the bare cu conductor if the counterpoise system is already there? This is in the airfield, so FAA has jurisdiction and their counterpoise system requirement will be enforced. I am just wondering about the additional bare cu conductor and whether that is necessary or will it create a more hazardous (grounding) environment.
Please let me know what you think. Appreciate any response. Thank you.
