My understanding is that the voltage generated by diesel-electric locomotives is variable, topping out in the low kilovolt range, and it would be counter-produc

My understanding is that the voltage generated by diesel-electric locomotives is variable, topping out in the low kilovolt range, and it would be counter-productive to control for a given voltage (other than to avoid exceeding the equipment maximum rating); the voltage is allowed to vary to match the speed-dependent back-EMF of the traction motors. If so, then a locomotive is unsuitable for patching into a multi-kilovolt network without a suitable transformer, and there will be voltage-matching and regulating problems to be resolved in patching into any level of the network.