The paper analyzes the explosive reasons of 35kV voltage transformer in Qingdong Mine and puts forward some specific measures to eliminate the resonance over-voltage in view of the neutral-point non-grounded running mode which is mainly used for the current distribution network of 35kV or under 35kV in China.

Measures preventing from iron core magnetic resonance caused by iron core saturation of potential transformer;

Single-phase check methed of potential transformer for on-site check;

Time-domain measuring method for wide-frequency transfer characteristic ofpotential transformer;

Voltage Mutual Inductor Grounding and Its Function in Transformer Substation;

Taking the case of voltage mutual inductor exploration of TYD-110/3-0.

Ferromagnetic resonance of voltage mutual inductors for 6 kV power supply system of the oil refinery took place several times, resulting in burn- out of voltage mutual inductors of 6 kV substation, explosion of lightning guards, breakdown of electric equipment, fusing of high voltage fuses and misoperation of relaying protection.

Site test and analysis of 220 kV metrical voltage transformer;

Analysis of voltage transformer secondary loop grounding point;

Verifying the voltage ratio of voltage transformer (discharge coil) by method of adding the high voltage;

Harm done by the failure of the circuitry PT to the power system;

PT Secondary Circuit Reducing Reform and its Reducing Mothod;

Analysis and Solution of the 6～10 kV Power Distribution Grid PT Resonance Elimination

The Cause of TV Secondary Wire Abnormity and Its Countermeasures;

Analysis of the Fusing on Primary Side of TV and Treatment;

The structure of Changdu power grid and the process of frequency oscillation accident are summed up,it is analyzed theoretically that the reason of the system oscillation is the ferromagnetic saturation of TV,low-frequency load reduction scheme for Changdu power grid is also analyzed,and the method against misoperation of low-frequency load reduction is put forward.