The FEA panel contains a Load Source section which determines if FEA is solving just the pole and crossarm deflection (Ruling Span) or is iteratively solving the pole and crossarm deflection along with the changes in conductor tension until an equilibrium is reached (Network Solve).

When the Load Source is set to Ruling Span the conductor tensions and sags are calculated using the ruling span method. These tensions are then applied to the structures which causes deflection.

With this option the deflection will not feed back into recalculating the conductor tensions such that the clearances and tensions calculated using this method will be identical to static analysis calculations.

For example, given a conductor is under high tension.

Once FEA has been run with Load Source set to Ruling Span the pole and crossarm deflect but the conductors stay in the original position.

In this case, the deflection will be overestimated compared to real world conditions which would see conductor tension lower as the pole deflects and thereby reduce the overall deflection.

When the Load Source is set to Network Solve the initial stringing tension is calculated and then the pole deflection is calculated. Deflection of a given pole will be impacted by changes in the deflection of adjacent poles. This requires an iterative process to be conducted until equilibrium is reached.

Using the same example but with Load Source set to Network Solve, the deflection is much smaller because as the pole defects the tension in the conductor drops.