A little more on generators

So on Friday, the 10^th of June 2011, I was taken to the Genset Room ( generator set room) for the test run that is scheduled weekly. What I got from this experience was pretty interesting as I hadn’t been given this kind of opportunity before. I was briefed on how the generator works and how to use a load bank. On top of that I was allowed to play with the switches and use the load bank for a hands on experience with the machines.

 I had been previously briefed on the basic works of a generator set, and this time a little more was shared. Information such as the synchronization of the generators was explained to me. There are four factors that have to be considered in order for synchronization to take place. These four factors include voltage, frequency, phase, and phase angle.

In the past, synchronization was performed manually using three-lamp method. Nowadays, the process is automatically operated and controlled with the aid of synchronization relays. During installation of a generator, careful checks are made to ensure the generator terminals and all control wiring are correct so that the order of phases (phase sequence) matches the system. Connecting a generator with the wrong phase sequence will result in a short circuit as the system voltages are opposite to those of the generator terminal voltages. 

The sequence of events is similar for manual or automatic synchronization. The generator is brought up to approximate synchronous speed by supplying more energy to its shaft - for example, opening the valves on a steam turbine, opening the gates on a hydraulic turbine, or increasing the fuel rack setting on a diesel engine. The field of the generator is energized and the voltage at the terminals of the generator is observed and compared with the system. The voltage magnitude must be the same as the system voltage.


  Synchronization is essential for running generators on a parallel bus with other generators or the utility. The generator must be synchronized to the bus voltage reference before the paralleling switchgear will close it onto the bus. This is accomplished using a synchronizer unit, which drives the generator’s governor to control its engine speed and output voltage frequency. A generator synchronizer is also used with all closed transition transfer switches.

The synchronizer will sync the generator when a utility reference is presented to the line side of the transfer switch. This accommodates the closed transition from generator to utility. This technology has been used for many years and has evolved to greater speed of action with advancements in electronic synchronization control and governors over mechanical units. A generator synchronizer unit can also be used to hold distributed generators in sync with the utility or each other. This assures the upstream synchronization required in a distributed redundant design that utilizes Delta Conversion Technology. A PLC controller is used to sense each of the generator and utility voltage references. If a valid utility reference is available, the PLC will provide this reference to the synchronizer units that are connected to the distributed generators. If no utility is available, the PLC will pick an operating generator and use its output as the reference for the others. This will enable system synchronization in any operating condition.

               

Attached with this post are some pictures or the generator sets and the load bank. I was allowed to manipulate the testing of these generators with load. I also was introduced to the circuit breakers as well as the way powering up the generator up.I’ve also included a video (very shaky recording) of my experience in the generator room. Enjoy!