Variable impedance energy-saving transformer

Summary

In recent years, the short-circuit current is increasing for the rapid growth of power system load, it may exceed the maximum breaking current of circuit breaker, it’s significant to use economic and efficient technical measures to reduce the impact of short-circuit current. Therefore, a new type of variable impedance energy-saving transformer was designed, this transformer combines the advantages of two common ways for limiting the short circuit current, which consists of high impedance transformer and fault current limiter, it could reduce the impact of short-circuit current and also take the economy into account. Common transformer and current limiting reactor were designed synthetically in variable impedance transformer, this makes variable impedance transformer owns compact structure, and its impedance could be self-regulated through the high-speed switch. The principle of variable impedance transformer was introduced, PSCAD simulation software was used to analyse the current limiting capacity and the distribution of overvoltage of transformer. Transient axial component of electromagnetic force in the windings of transformer was analysed based on three-dimensional finite element method. Researches indicated that variable impedance transformer could increase the ability to withstand short circuit current impulse through the adjustment of the impedance, short circuit current could be reduced by 36.8%. Switching overvoltage would occur in variable impedance transformer for the operating of high-speed switch, this transient overvoltage may do great harm to the variable impedance transformer. In order to achieve an effective protection for this overvoltage, a kind of combined protection method which consists of metal oxide surge arrester and RC absorbing device was proposed in this paper. Dynamical electromagnetic force would occur on copper disks and coils owing to the considerable leakage magnetic field excited by short-circuit current. The magnetic flux density of transformer body could be decreased by 31.1 %, and the axial electromagnetic force of high voltage windings could be suppressed by 56.9 %. The benefits of variable impedance energy-saving transformer in economy and society are remarkable, its extending foreground is roomy.

Additional informations

Keywords

Variable impedance transformer, Energy-saving, Current limiting reactor, Short-circuit current, Electromagnetic force