You're right to be thorough and question potential hazards. Even with de-energized and grounded conductors, and grounding the static line, there are still potential concerns, although the risk is likely low. Here's a breakdown of the considerations

Why the Crane Company Might Be Concerned (And Why They Might Be Overreacting):
Induced Voltage (Capacitive and Inductive Coupling)

Even with conductors grounded, energized sources nearby (even if not directly overhead) can induce a small voltage in nearby conductors and objects due to capacitive and inductive coupling. This effect decreases rapidly with distance. However, because all of your conductors are grounded this will not be a source of voltage.

Static Electricity Build-Up

Crane booms, especially in dry conditions, can build up a significant static charge. While you're grounding the static line, the crane itself may not be as effectively grounded through the earth (especially if it's on concrete or asphalt).

Stray Ground Currents

Large substations can have complex grounding systems with circulating ground currents. While unlikely to cause a significant induced voltage, it's a possibility, especially if the crane's grounding is poor.

Crane Stability

Cranes can be unstable and may cause the crane boom to get closer than the required 10 feet.

Why the Risk is Likely Low (Given Your Precautions)



De-energized and Grounded Conductors

This is the most important factor. Grounding the conductors virtually eliminates them as a source of induced voltage.

Grounded Static Line

Grounding the static line is a good practice and further reduces the risk.

Distance to Static Line (30 Feet)

At 30 feet, any induced voltage from the static line, even if it were energized and not grounded, would likely be minimal.

What You Should Do (Beyond What You've Already Done)


Confirm Grounding Integrity

Verify the grounding of the de-energized conductors with a meter before the crane operation begins. Ensure that the crane's grounding is effective. Use a ground resistance tester to measure the crane's grounding impedance to earth. This can be done by checking the resistance of the crane body to the grounding grid in the substation. Visually inspect all ground connections for tightness and cleanliness.2.

Communicate Clearly with the Crane Company

Explain the grounding procedures in detail. Show them the grounding points on the conductors and the static line. Document all grounding tests and measurements. Ask the crane company to explain their specific concerns. Are they worried about a specific type of induced voltage or static build-up? Knowing the source of their concern can help you address it.3.

Consider Additional Precautions (If the Crane Company Remains Concerned)



Barrier/Spotter

Have a spotter dedicated to monitoring the distance between the crane boom and the static line.

Grounding Cable

If they are truly concerned about static buildup, have them provide a ground cable attached to the crane body that is connected to the substation grounding grid.

Important Considerations



Qualified Personnel

Ensure all grounding procedures and crane operations are supervised by qualified electrical personnel familiar with substation safety practices.

Weather

Avoid crane operations in wet or stormy conditions, as these can increase the risk of electrical hazards.

Documentation

Document all procedures, inspections, and measurements.*

Crane Operator's Judgement

The crane operator always has the right to refuse to operate if they feel unsafe. Listen to their concerns and address them appropriately.

In summary, while the risk is likely low given your grounding procedures, it's essential to address the crane company's concerns, verify grounding integrity, and communicate effectively. Document everything, and prioritize safety above all else. Flag for review