In Stephen King’s 1994 made-for-TV movie “The Stand,” most of the human race is wiped out by a deadly virus. As a result, power stations are unmanned and Americans are left without electricity for months. That is, until a husband and wife team works engineering magic at a power plant, flipping the right switches to bring the entire grid back online.
Anyone familiar with the black start process knows that in real life, it doesn’t happen with quite so much Hollywood pizzazz. But black start is a remarkable process and the controls and instrumentation used during a black start must operate with the utmost precision and speed.
A black start unit is one that can start its own power without support from the grid in the event of a major system collapse or a system-wide blackout. In the U.S., every region within the North American Electric Reliability Corp. (NERC) has its own black start plan and procedures. Each region also designates certain plants as black start units. The controls used on a black start unit include a DC auxiliary support system, an ignition source, a gas turbine and a diesel generator.
Carlo Barrera, senior consulting engineer at PAL Turbine Services LLC, has overseen several conversions of gas turbines to have black start capabilities, including projects for Puget Sound Energy and Massachusetts Municipal Wholesale Electric Co. For the city of Gardner, Kan., PAL installed its own programmable logic controller for turbine control. At a later date, black start capability was incorporated and proved out using a load bank.
Barrera said the DC auxiliary support system is perhaps the most important part of the control system. The battery system must have enough capability to provide DC power for multiple start attempts in case the gas turbine fails to start or fire the first time. “The battery systems need to have the capability in reserve power for two or three firing attempts if a true blackout emergency happens, since gas turbines don’t always start on the first attempt in a blackout situation,” Barrera said.
When the loss of AC power in the grid is noticed on a black-start turbine, an undervoltage relay initiates the start of numerous DC motor-driven auxiliaries. Devices like the turbine lube oil pump, liquid fuel forwarding pump, atomizing air compressor, starting clutch, diesel starting motor and shaft turning ratchet all require DC power to operate. DC auxiliary support system suppliers include GE, Siemens and ABB.
Source: Black Start: Preparedness for Any Situation
