Very High PF Test Results on Stator Windings

I’m power factor testing stator windings that belong to a 420kW, 4.16kV brushless alternator. The unit is old, is absolutely covered in dirt and dust (operates outside in the desert where it also occasionally rains), and has never been PF tested before to my knowledge. I’m getting a PF of 25% when I apply 2.4kV between all 3 phases plus the neutral and ground. I’m used to 0.2-1% on equipment, not 25%. I’m isolating and shorting all 3 phases and the neutral together. I’m also shorting and grounding all of the rotor windings, IAW Doble instructions. Has anyone else gotten such high PF results on equipment that seems to run decently? I know dirt and water will raise both the PF and the capacitance, but this seems excessive.

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