Study On Controlled Gap Of 110kV Transformer Neutral Point

At present, insulation level power system hanging after running 110kV transformers are considering overvoltage and economic determination。 The neutral point of 1 lOkV transformer exists overvoltage protection problems because of its half insulation structure. Damage of neutral insulation are mainly attributed to the atmosphere and internal overvoltages, to ensure the safety and reliable operation of the power system, must ensure that the operation of the electrical equipment hanging on a higher level of insulation to withstand the effect of various types of overvoltage o The arrester parallel discharge gap protection method, widely used now, can’t effectively solve the problems. Accidents occur frequently in practical application. Therefore, to develop a new type of discharge gap fitting arrester to solve transformer neutral point overvoltage protection, so as to achieve the desired protective effect has been imperative=First, select the actual transformer substation parameters of Wuzhong Grid, have a simulation to the neutral point over-voltages. With the simulation results, a kind of new over-voltage classification method has been put forward, that is short-term overvoltage and continuous overvoltage. This new method provides the duties of the protection devices, makes it clear that these overvoltages are needed to protect or not and how to protect. Problem has been solved that the cooperation between the numerous voltage parameters which are calculated by theoretical and empirical formula has great error, it provides a guarantee for the design of new protective gap.Secondly, design a new triggered and controlled discharge gap. The new gap takes the three-electrode system. The control circuit could give a intelligent judgment to neutral overvoltage and issue action instruction, then the controlled gap will be broken down. Meanwhile employing the ball electrodes as discharge electrodes will solve the problem of the discharge dispersion and improve the gap’s ability of resistance to impact and ablation. The PCB circuit board is designed and made, and have a simulation for the discharge time. The results show that the control circuit can effectively distinguish between short-term overvoltage and continuous overvoltage. So the new gap has the same voltage-selected function.Finally, the complete equipment of new gap is machined and assembled, using the high voltage laboratory environment and the existing technical conditions of Ningxia electric power research institute, the machine are successfully detected by experiments. The results show that new gap can act reliably in specified voltage when power frequency voltage test is performed but cannot act just right in the setting voltage when operating surge voltage test is finished. The new gap accords with the design standard. New gap fitting arrester can thoroughly solve many problems of overvoltage protection of the 110kV transformer neutral point, achieves ideal protective effect.