Basic of Power Plant automation system

Power plant Automation system is the complete solution of safe and efficient operation. In a power plant, there are lots of complex system required to work and more complication is that this system are inter related. Not only interrelated, they are required to follow exact time sequence in operation. Say in a heavy oil power plant- the engine run by HFO, at the same time there are at least dozens of direct process need to smoothly operate.

The recognized facts & parameters are – pressure of fuel supply, temperature of fuel, engine cylinder temperature, engine lube oil temperature & pressure, cooling water temperature in different location, engine speed etc.

For the safe and optimal operations, these facts are controlled by automation. These are categorize as per their importance and risk level. Say in Diesel engine based power plant the most severe risk factors are -over speed, engine jacket water high temperature & low lube oil pressure to engine.

Thus, any of this fault occurs there is no waiting for action of operator- automation system directly shut down the engine. With these three fault occurring without sudden action, the engine will be mechanically damaged severely. On the other hand, these three facts are not important for a turbine base power plant.

Power Plant automation with Wartsila Engine

In Wartsila 20V32 diesel engine, there is a processor module named ESM- engine safety module, which handles these three faults directly. The shutdown signal generated by ESM cannot be overridden by the operator. Practically we know that without lube oil flow running a diesel engine is suicidal, the bearing and crank shaft will be permanently damaged. The modern automation system of engine is so advance that you cannot do a speed simulation in a stopped engine.

The speed simulation is to pass a speed signal to ESM to test if it shut down the engine under over speed while practically the engine is idle - it is an automation system check. However, the ESM will not take it until another signal is pass to generate sufficient lube oil pressure simulation- this is done by bypassing in ESM module. So a true automation will not do mistakes whether the operator do it.

Therefore, as discussed above there are categorized fault and facts in a power plant as per risk level and importance. Some minor alarm is raised to alert the operator – do nothing, some major alarm is raised and wait for a certain time to be corrected by operator- if they are unattended there is some schedule task works like lowering the load or shutting down the engine, and some immediate shut down faults.

Power plant automation encircles some typical but vital concept of automation systems like Control by PLCs and UNIC, Protection-by-Protection relays, [1]Supervision by PLC and Monitor by supervisor engineers.

A typical automation diagram of a power plant

PMU-Power monitoring unit. Unitrol 1000 is a Automatic voltage regulator from ABB, Vamp 210 for generator protection and Vamp 265 for Generator differential protection.

Click on the image of a typical automation diagram of a power plant to view large.

                               Fig: Typical Power plant automation system with diesel based engine.