Research Of 10kV Anti-ferromagnetic Combined Voltage Transformer

In HV grid, ferroresonance overvoltage is often appear a kind of internal overvoltage. Ferromagnetic resonance will make overvoltage, under voltage transformer core flux increased exponentially, excitation current, under voltage divider, as a result of rising voltage at the same time, the frequency is reduced, iron core saturation quickly, a transformer winding through the current will be far more than the normal capacity, cause the winding overheating or even burning, make serious disruption to the safe operation of power grids, threats to personal safety.Standard 3-phase-5-pole voltage transformers could neither eliminate resonance nor suppress ultra-low-frequency resonant current. Chinese patent ZL 01308962.5 published a 3-phase-5-pole voltage transformer which is built by molded anti-climate epoxy, it is equipped with external resonance-suppressor and fuse to eliminate resonance and to protect circuit. However, the result is not so satisfying.According to the theories of ferroresonance generation and electromagnetic induction of voltage transformers, the product discussed in this paper uses series-connected single-phase PT at PT high voltage side(also called 4PT method), to connect single-phase voltage transformers to the neutral point of voltage transformer, in order to eliminate resonance. In this way, the equivalent impedance of voltage transformer is increased, since the put-in of single-phase voltage transformers is equivalent to put-in of high impedance load.Once there is a single-phase grounding failure, the single-phase voltage transformers will share zero sequence voltage in the system, to avoid core saturation of the transformer. This also helps to prevent ferroresonance happening, which could lead to ferroresonance overvoltage.In this paper, Matlab is used as simulation platform, to establish the model of voltage transformer ferroresonance;Using dalian enterprise power equipment co., LTD.Test equipment for electrical performance testing.The test results comply with all related GB standards. This product contributes to the realization of smart electricity grid system.