Study Based On Orthogonal Test For Generator Stator Coil Cooling Water PH Control

Because of the requirement of water pH in new national standard GB/T7064-2008, itis necessary for the power plant to control the pH of generator stator coil cooling water. Ingenerator normal operation, injecting NaOH solution into the stator coil cooling watersystem is an effective method. The pH on-line meter doesn’t work stably and reliably athigh purity water with pressure condition, so it’s impossible to control the pH directly by apH meter. But conductivity has some relationship with pH, so this article gives a method tocontrol pH indirectly through conductivity controlling.For the generator stator cooling water, the conductivity is affected by four mainfactors: temperature, oxygen dissolution, treated water flow, ion concentration andcomposition. These four factors change very complexly，so, an orthogonal experimentshould be done if we want to know whether the stator cooling water system pH controlmethod can satisfy our requirement.This article gives a four factors and three levels orthogonal experiment, takes9groups of27days test which nearly cover all the complex conditions in generator normaloperation. Then uses bypass treatment system as a process, ion exchange and alkalizer asadjust equipments to regulate the water conductivity which is affected by temperature,oxygen dissolution, treated water flow, ion concentration and composition in differentconditions. Finally ensure the stator cooling water system pH control methods can beworked well after analyzing from orthogonal test, it can maintain the water conductivity at1.5μS/cm, that is pH8.8up to the national standard of high quality.