Should the OPC be disabled for the turbine load rejection test?
Thread Content
Purpose of the turbine load rejection test: 1. To evaluate the dynamic characteristics of the turbine control system. 2 After load rejection, the maximum speed rise of the turbine must not cause the mechanical emergency shutdown device to trip. 3 After load shedding, the unit’s control system (DEH) enables the unit’s speed to stabilize rapidly at idle speed. So, may I ask if it is necessary to disable OPC during the turbine load-shedding test? I believe that evaluating the dynamic characteristics of the turbine’s control system involves ensuring that the turbine can still remain at its rated speed thanks to the speed control system even under load-shedding conditions, with the maximum speed increase not exceeding 5% of the speed variation rate, which is 3150 revolutions per minute. When OPC is active (with an operating speed of 3090 revolutions per minute), it is the protective devices that close the throttle valves, rather than the turbine’s own speed control capabilities; therefore, OPC needs to be disabled.
If you want to try mechanical ejection, then revert to OPC
Thank you. I was asking about the load-shedding test, not mechanical overspeed
It definitely has to be shut down; the oil switch tripping mechanism that causes the turbine to stop operating, as well as the low vacuum protection system, all need to be disabled
Thank you. Does load shedding cause a low vacuum? Why remove the vacuum protection? Loading rejection involves turning off the generator’s output switch – will this cause the oil circuit breaker to trip? Why is there also an oil passage switch? Thank you for the guidance.
Because after load shedding, if adjustments are not made in a timely manner, air will leak through the rear steam seal, resulting in a decrease in vacuum. This may cause the low-vacuum protection to activate at a speed that is not yet the maximum operating speed, leading to the disconnection of the oil switch and thus the shutdown of the turbine. Once load shedding occurs, the oil switch definitely disconnects, causing the turbine to shut down; however, it is not necessarily at the maximum operating speed at that moment
After load shedding, the throttle valve is closed, resulting in a decrease in steam inflow. This reduces the leakage from the front shaft seal, and as a consequence, less steam reaches the rear shaft seal. This leads to air leaking in and a drop in vacuum, right? Thank you for your reply.
Yes, it is to prevent the low vacuum protection from activating before the rotation speed reaches its maximum value
The debugging units nowadays claim that it’s not possible to withdraw the OPC when performing load shedding; they say they’ve never heard of such a requirement. The debugging unit in question is Shandong Zhongneng Electric Power
During debugging, there is a fear of problems occurring and of having to take responsibility; don’t think that just because their skills are high they are willing to carry out load-shedding tests
Thank you to ftl811101 for the answer: handshake