Periodic fluctuation of current in the 505 electro-hydraulic converter
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What are the factors that cause periodic fluctuations in the current of the 505 electro-hydraulic converter? I am responsible for the operation of steam turbines. When the load on the turbine remains stable, the current usually fluctuates slightly within the range of 4–20 mA. But a few days ago, for some unknown reason, the current fluctuated between 12.8 mA and 20 mA, which caused significant fluctuations in both the secondary oil pressure and the turbine’s load. The control oil pressure as well as the emergency shutdown oil pressure also decreased. Could slight fluctuations in the power grid at that time have affected such changes in current? It only returned to normal after a significant reduction in load. I’m not very familiar with the speed control system, so I’ve come here to ask for everyone’s advice. What are the causes of current fluctuations?
Test it every time before turning it on, by performing a valve pull test.
Later analysis revealed that the cause was voltage fluctuations on the connection line leading to the main power grid, which resulted in fluctuations in the current of the auxiliary equipment within the plant; as a consequence, the current of the 505 voltage regulator also fluctuated.