Diesel Generators play a major role in the Power Generation Industry. This article describes a few of the ways they are commonly used in power plants and substations.
Coal, Natural Gas, Oil and Nuclear Generation
Diesel generators are widely used at most Coal, Gas and Oil Fired Power Plants and virtually all Nuclear Power Plants in the United States has an emergency backup power source for the station's auxiliary needs. These auxiliaries include critical pumps, fans, hydraulic units, battery chargers, turning gear motors for steam turbines and much more.
In large Power Plants, there is usually at least one emergency diesel generator set per unit. These diesel generators are automatically started when an under-voltage relay is activated, usually due to a failed station service transfer when a generating unit is tripped offline. In Coal Fired Power Plants this scenario is not unusual. Electrical systems such as relays for transformers and/or circuit breakers can and do go to ground and fail due to the water, coal dust and ash debris that inherently finds its way into equipment.
In a typical Nuclear Power Plant during a power interruption, a backup battery bank powers much of the critical equipment such as the reactor cooling pumps. Then the backup diesel generators start and power the station auxiliaries and battery chargers. More backup systems can be used, these include portable diesel powered pumps for reactor cooling.
At Hydro Generation facilities, another very important use of diesel generators can be noted. They not only provide back-up power for the generating units, but in most cases also provide emergency power to the spillway gates that are used to prevent over topping of a dam when flooding conditions exist and threaten populated areas downstream of these facilities. There are usually two or more diesel generators at modern dam sites due to the distances between the spillway controls and the Power Plant.
Substations and Switchyards
Substations and switchyards contain the components needed to distribute and deliver electricity at a desired voltage to the power companies customers. Circuit breakers, transformers, protective relaying and the communication systems that control these devices, all require a backup power source whenever power is lost to the station. These power outages happen frequently in many geographical areas and are usually caused by storms, lightning and high winds that can cause downed power lines. Battery banks are used to temporarily power the protective relaying, but will only provide backup for a short time. In these critical times, backup Diesel Generators will automatically come online and power the battery chargers to keep the battery banks voltage from dropping too low, avoiding battery and station equipment failure.
United States Federal law mandates that all electric power generators (electric power companies) follow NERC-North American Electric Reliability Corporation guidelines for electric power restoration in the event of a total electric blackout of the electrical grid and to their customers. This power restoration procedure is called a “Blackstart”. The vast majority of Blackstart procedures involve the use of diesel generator sets. Hydro generators may also be used as they have horsepower at the ready, but Hydro’s also use backup diesel generator sets to run their auxiliaries during a Blackstart.
Total system grid blackouts are rare, but NERC requires power generating utilities to practice or rehearse Blackstarts on a set schedule to remain in compliance, or they could face heavy fines.
Diesel Power Plants
In many parts of the world, including the United States, there are geographical areas where using Diesel Generators is the only viable option for providing reliable power to the local population. Alaska is an example where this practice is common and power companies there use Diesel Generating Plants as a major component of their power generation portfolio. Many of these sites are not hooked into a power grid and must control their own frequency and voltage.
Green Energy is a fast growing and obviously popular endeavor throughout the world. There are power plants that use landfill gases which contain 40%-60% methane and other gases to provide fuel for Power Plants. Many, if not the majority of these are diesel plants. These power plants are called LFGTE Projects (Landfill Gas-to Energy) and are a renewable resource. As of July 2013, there were 621 Landfill Gas Energy Projects in the United States.
Planned and In Service LFGTE Sites
*Click map image for link to EPA site.
These projects are usually located around high population density areas.