(1)Disadvantage and advantage comparison of YN three phases at same side and YN phase by phase measurement
Measure three phase resistance at same time, greatly shorten working time;
Data are collected for three phases at same time when the high temperature is just shut down, avoid influence of temperature change on the balance degree of three phases;
Reduce influence of oxidation film of voltage regulation switch contact on the unbalance degree of three phases.
(2)Disadvantage of comparison between YN three phases at same side and YN phase by phase measurement
Because magnetic circuit is firstly established for first group data and there is mutual influence between three phases, so stability time is slightly longer;
For the transformer with voltage regulation switch, there is great error in resistance value because of influence of oxidation film even though balance degree of three phases is qualified, be careful when data are filled in test report;
No current passes through leading part of the neutral point, it can't demonstrate whether leading line of the neutral point is normal, one data of each phase shall be demonstrated according to single phase way.
The measurement value doesn't include leading resistance of the neutral point. In order that the coil resistance is approximated, there is error between ex-work values of the transformer, analyze as following in detail.