Ramsis Girgis investigated typical x/r ratios for power transformers and transmission lines after a request from the working group to re-evaluate the standard values. He found that: - Transformer x/r ratios range from 15-40 for small transformers, 35-70 for medium transformers, and 40-125 for large transformers. - Transmission line x/r ratios decrease with lower voltage, ranging from 21 for 765kV lines to 9.7 for 161kV lines. - Substation x/r ratios vary depending on the amount of generation but typically range from 10-20, with higher voltages having higher ratios.