Mountainview in a nutshell

(Click on photo to enlarge) This is a simplification of the power distribution at Mountainview, but generally this is how the plant works. When the plant is not generating power, it still needs power to run the systems necessary to start, so power is brought into the plant by the very same power lines it will use to feed the grid. This condition is called "back feeding". 230,000 volts is applied to the main transformer which steps the voltage down to 18,000 volts. The power is then fed to the Unit auxiliary Transformer or UAT which steps the voltage down to 4,160 volts. This voltage allows the Circulation Pumps, which are the large motors in front of the cooling towers to move cooling water through the plant, as well as the gas compressors and feed water pumps. The voltage is also stepped down to 480 volts through the load center transformer, which provides power for smaller motors, UPS systems, and other lower voltage systems to run the plant. Strange as it may seem, in order to make AC power, you need DC power, so the Excitation Transformer steps the 4160 volts down to 380 volts and rectifies it. It then sends this voltage to slip rings in the Generator Collector. When the north and south poles in the rotor spin past the stator polls, an alternating current will develop, generating 18,000 volts AC. In order to get the rotor spinning, however, we must first start the turbine. This is done through the Static Start transformer, which steps up the 4,160 volts to 2,080 volts and then through a variable frequency drive directly to the Isophase bus. This will turn the generator temporarily into a motor which will spin the combustion turbine. Once the turbine is up to speed, fuel is applied and ignited and the generator will begin making power. The last step in the process is closing the generator breaker. In order to do this, the generator and grid must be in synchronization. A special relay called a synch relay watches both the rotating magnetic field of the grid and the generator. The generator will spin slightly faster than 60 hertz, and when the phases are within a critical angle and voltage, the breaker switch is closed and the phases will be locked together.
Posted by Hello