Positioning the Cutsforth Shaft Grounding and Contact Assemblies | Series 3

The Cutsforth Shaft Grounding Assembly is installed on the same portion of exposed shaft as the previous grounding equipment.

The Cutsforth Shaft Contact Assembly is installed on an exposed portion of the shaft at the exciter-end of the generator at a location at which a secondary shaft voltage measurement is desired. Both the Shaft Grounding Assembly and Shaft Contact Assembly must be installed on the “uphill” side of the shaft rotation. Installing on this side of the shaft ensures that the rope does not bunch up or bind up inside the rope guide. The following illustration shows the correct orientation on the left.

Verify that there is adequate spacing on all dimensions of the SGA and/or SCA assemblies including the support arm and mounting point. Consider both the hot and cold operational conditions, and account for thermal expansion when installing in narrow clearance locations. Factors such as generator type may affect the clearances needed to account for thermal expansion.

To maximize the effectiveness of the Shaft Grounding Assembly (SGA), the wire run length must be minimized. The 8 AWG wire will run from the Shaft Grounding Assembly directly to unit case ground. Cutsforth requires that the total run length of the ground wire be less than 5 ft (1.5 m).

The goal when choosing a grounding location is to electrically bond the shaft to the unit case. The unit case is defined by the lower half of either the turbine case, generator case, or coupler case near the SGA to which the shaft can be grounded. Cutsforth suggests drilling and tapping into the lower half of the unit case to create a grounding location close to the Shaft Grounding Assembly. The location at which the ground wire will terminate should have all paint removed and should be free of all contaminants in order to create a smooth, conductive surface. Structural steel and station ground are examples of unacceptable grounding locations. It is important to note that it is not necessary for the ground conductor to be grounded to an existing generator grounding pad.