IEEE Std 1870-2019 pdf download – IEEE Guide for the Parameter Measurement of AC Transmission Lines.
6. General considerations during measurement The following items should be considered before conducting off-line measurements: a) Make sure that all the temporary grounding wires along the line are dismantled and nobody is working on the transmission line. b) Pay close attention to the weather condition along the lines during the measurement. The meas urement shall be stopped if the weather is not suitable for measurement, for example, when there is thunderstorm, rain, or snow along the transmission line. c) The leads of shunt reactors, capacitors, and capacitive voltage transformers (CVTs) should be disconnected from the transmission line in the off-line measurement. The transmission line shall be disconnected from bus-bars. d) Any series compensation device used in the transmission line shall be bypassed during the meas urement. e) If the transmission line under measurement is composed of cables and overhead lines, it is recommended to measure the parameters of the overhead lines and cables, respectively. f) The substation grounding grid should serve as protective grounding, neutral point grounding, and short-circuit grounding. The grounding point of a tower is prohibited to be the grounding point of the meas urement.
8. Phase verification and insulation resistance meas urement 8.1 General Phase verification and insulation resistance measurement are performed when all the conductors are not in service. Phase verification is adopted to check the consistency of phase labels at both terminals, so as to prevent the power system from serious impacts when the transmission line is switched into service, especially for newly built or reconfigured lines. The insulation resistance measurement is adopted to check whether any protective grounding wire has been dismantled along the newly built or reconfigured lines. 8.2 Phase verification using dc (or ac) power sources DC power sources are recommended to be used for phase verification if the induced volage of the measured line is about several hundred volts. Take the phase verification of phase c as an example. The procedures are as follows.