| The converter valve plays a key role in HVDC,and it bears the function of interchanging between the alternating current and the direct current.But the fault in the converter valve also caused a lot of trouble to HVDC.Through the converter valve fault analysis,the fault in the inner cooling water system is the greatest danger,and main fault in the valve inner cooling water system is mainly because of the corrosion behavior in a certain extent.The corrosion products of the inner cooling water system of HVDC converter valve mainly are deposited on the surface of the voltage-sharing electrode.The depositions fall in the inner cooling water system,and the depositions could cause inner cooling water system breakdowns such as blocking and leakage,which may cause tripping operation of HVDC equipment in severe.In order to solve the problem of blocking,the corrosion behavior of the inner cold water system should be suppressed.In order to study the corrosion behavior of aluminum alloy which causes in thyristor heat sinks,a converter valve cooling system simulation platform is set up.By changing the conditions of water quality in the water system to analyze the influencing factors of aluminum alloy corrosion: the effect of adding nitrogen protection device for corrosion behavior,the effect of ion exchange resin bed for corrosion behavior and the effect of additional voltage at both ends of thyristor heat sinks for corrosion behavior.By changing these conditions,the measured of conductivity,p H,dissolved oxygen,temperature,chloride ion content,total aluminum ion content and total iron ion content to reveal corrosion behavior in the inner cold water system.The measured of temperature,pH,conductivity and dissolved oxygen content are online monitored data through the device on the converter valve cooling system simulation platform.Chloride ion content direct determinates by chlorine ion meter,and the total aluminum ion content and total iron ion content determinates by spectrophotometry,Through drawing trend chart,the influence factors of the corrosion behavior of the inner cold water system are analyzed.Study the effects of different conditions on the corrosion behavior of inner cooling water system,we could have a further understanding of the corrosion behavior of the inner cooling water of HVDC,and the fault of inner cooling water system provides the basis for improvement. |
