¹ The instantaneous maximum rms voltage difference at any time between two sources. Common causes of voltage differences would include disturbances such as large load, transformer tap changer or capacitor switching at some point upstream from the network transformer. Utility should be able to provide this information.
² While there will be differing amounts of phase-shift based on different lengths of lines for the two sources, you must insure that the original sources have identical phase shift and phase rotation where they originate. Phase shift is affected by different transformer winding connections. All transformers paralleled must have the same winding connections (Delta-Wye, for example). Phase rotation is affected by accidentially swapping phase conductors causing a C-B-A versus an A-B-C (for example) rotation.
³If X/R ratio not provided directly, check on the network transformer to see if reactance (X) and resistance (R) is given instead. If so, then divide the reactance (X) value by the resistance (R) value to compute the X/R ratio. If you still cannot locate this data, estimate 6 to 8 for a transformer less than 2000 kVA and estimate 12 for a transformer 2000 kVA and greater.