Black Start
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A black start is the process of restoring an electric
power station A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the electricity generation, generation of electric power. Power stations are generally connected to an electr ...
, a part of an
electric grid An electrical grid (or electricity network) is an interconnected network for electricity delivery from producers to consumers. Electrical grids consist of power stations, electrical substations to step voltage up or down, electric power tran ...
or an industrial plant, to operation without relying on the external electric power transmission network to recover from a total or partial shutdown.Knight, U.G. ''Power Systems in Emergencies - From Contingency Planning to Crisis Management '' John Wiley & Sons 2001 section 7.5 The 'Black Start' Situation Power to restart a generating station or plant may come from an on-site black start standby generator. Alternatively, where a large amount of power is required, a tie-line to another generating plant or to an emergency generator may be used to start the facility. Once the main generating units are running, the electrical transmission network can be re-connected and electrical loads restored. Black-start power may be ensured by an agreement where a particular energy supplier is paid to make black start power available when required. Not all generating plants are suitable for providing black-start power to a network.


Station service power

Electrical generating plants require electric power to operate systems required in the plant. For example, a coal-fuelled plant requires conveyors, crushers, air compressors, and combustion air fans to operate. Steam cycle plants require large pumps to circulate water for steam boilers and for cooling of condensate water. Hydroelectric plants require power to open intake gates, and to adjust the hydraulic turbines for speed regulation. Even a wind turbine plant may require a relatively small amount of electric power for such things as adjusting blade pitch and direction. Normally, the electric power used within the plant is provided by the station's own generators. If all of the plant's main generators are shut down, station service power is provided by drawing power from the grid through the plant's transmission line. However, during a wide-area outage, off-site power from the grid is not available. In the absence of grid power, a so-called black start needs to be performed to bootstrap the power grid into operation.


Standby power sources

To provide a black start, some power stations or plant have small on-site
diesel generator A diesel generator (DG) (also known as a diesel genset) is the combination of a diesel engine with an electric generator (often an alternator) to generate electrical energy. This is a specific case of an engine generator. A diesel compress ...
s, normally called the ''black start diesel generator'' (BSDG), which can be used to start larger generators (of several
megawatt The watt (symbol: W) is the unit of Power (physics), power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantification (science), quantify the rate of Work ...
s capacity), which in turn can be used to start the main power station generators. Generating plants using steam turbines require station service power of up to 10% of their capacity for boiler feedwater pumps, boiler forced-draft combustion air blowers, and for fuel preparation. It is uneconomical to provide such a large standby capacity at each station, so black-start power must be provided over designated tie lines from another station. Often
hydroelectric Hydroelectricity, or hydroelectric power, is Electricity generation, electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other Renewable energ ...
power plants are designated as the black-start sources to restore network interconnections. A hydroelectric station needs very little initial power for starting purposes (just enough to open the intake gates and provide excitation current to the generator field coils) and can put a large block of power on line very quickly to allow start-up of
fossil fuel A fossil fuel is a flammable carbon compound- or hydrocarbon-containing material formed naturally in the Earth's crust from the buried remains of prehistoric organisms (animals, plants or microplanktons), a process that occurs within geolog ...
or nuclear stations. Certain types of combustion turbine can be configured for a black start, providing another option in places without suitable hydroelectric plants. In 2017, a utility in Southern California successfully demonstrated the use of an energy-storage system based on a lithium-ion battery to provide a black start, firing up a combined-cycle gas turbine from an idle state.


Startup sequence

One method of black start (based on a real scenario) might be as follows: # A battery starts a small
diesel generator A diesel generator (DG) (also known as a diesel genset) is the combination of a diesel engine with an electric generator (often an alternator) to generate electrical energy. This is a specific case of an engine generator. A diesel compress ...
installed in a hydroelectric generating station. # The power from the diesel generator is used to bring the generating station into operation. # Key
transmission Transmission or transmit may refer to: Science and technology * Power transmission ** Electric power transmission ** Transmission (mechanical device), technology that allows controlled application of power *** Automatic transmission *** Manual tra ...
lines between the station and other areas are energized. # The power from the station is used to start one of the nuclear/fossil-fuel-fired
base load The base load (also baseload) is the minimum level of demand on an electrical grid over a span of time, for example, one week. This demand can be met by unvarying power plants or dispatchable generation, depending on which approach has the best m ...
plants. # The power from the base load plant is used to restart all of the other power plants in the system. # Power is finally re-applied to the general
electricity distribution Electric power distribution is the final stage in the delivery of electricity. Electricity is carried from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the transmission ...
network and sent to the consumers. Often this will happen gradually; starting the entire grid at once may be unfeasible. In particular, after a lengthy outage during summer, all buildings will be warm, and if the power were restored at once, the demand from air conditioning units alone would be more than the grid could supply. In colder climates, a similar issue can occur in winter with the use of heating devices. In a larger grid, in addition to this "single island" ("bottom-up") approach, different strategies can be involved: * multiple islands of generation (each with local power supplying local load areas) synchronizing and reconnecting to form a complete grid. The power stations involved have to be able to accept large step changes in load as the grid is reconnected; * anchor ("core") island (also bottom-up); * "backbone island" (bottom-up): backbone is restored first, thus allowing the outside assistance; * top-down: backbone restored first with outside assistance; * a combination of top-down and bottom-up approaches. There are multiple methods of commencing a black start of an island: hydroelectric dams, diesel generators, open cycle gas turbines, grid scale battery stores, compressed air storage, and so on. Different generating networks take different approaches, dependent on factors such as cost, complexity, the availability of local resources (e.g. suitable valleys for dams), the interconnectivity with other generating networks, and the response time necessary for the black start process.


Procurement of black start services

In the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
, the grid operator has commercial agreements in place with some generators to provide black start capacity, recognizing that black start facilities are often not economical in normal grid operation. It is typical of power stations from the era of the
Central Electricity Generating Board The Central Electricity Generating Board (CEGB) was responsible for electricity generation, transmission and bulk sales in England and Wales from 1958 until privatisation of the electricity industry in the 1990s. It was established on 1 Januar ...
to have a number of open-cycle gas turbines (i.e. no heat recovery modules attached) that can run the entirety of the plant necessary to operate a full generating unit; these would normally be started by diesel generators, fed in turn by battery backups. Once up to speed, these gas turbines are capable of running the entire plant associated with the rest of the power station, negating the need to bring power in from other sources. In the North American
independent system operator A regional transmission organization (RTO) in the United States is an electric power transmission system operator (TSO) that coordinates, controls, and monitors a multi-state electric grid. The transfer of electricity between states is consider ...
s, the procurement of black starting varies somewhat. Traditionally, the black-start capability was provided by integrated utilities and the costs were rolled into a broad tariff for cost recovery from ratepayers. In those areas which are not part of organized electricity markets, this is still the usual procurement mechanism. In the deregulated environment, this legacy of cost-based provision has persisted, and even recent overhauls of black-start procurement practices, such as that by the ISO New England, have not necessarily shifted to a competitive procurement, even though deregulated jurisdictions have a bias for market solutions rather than cost-of-service (COS) solutions. In the United States, there are currently three methods of procuring black start. The most common is cost-of-service, as it is the simplest and is the traditional method. It is currently used by the
California Independent System Operator The California Independent System Operator (CAISO) is a non-profit Independent System Operator (ISO) serving California. It oversees the operation of California's bulk electric power system, transmission lines, and electricity market generated ...
(CAISO), the PJM Interconnection and the New York Independent System Operator (NYISO). The exact mechanisms differ somewhat the same approach is used, namely that units are identified for black start and their documented costs are then funded and rolled into a tariff for cost recovery. The second method is a new method used by the Independent System Operator of New England (ISO-NE). The new methodology is a flat-rate payment which increases black-start remuneration to encourage provision. The monthly compensation paid to a generator is determined by multiplying a flat rate (in $/kWyr and referred to as the $Y value) by the unit's Monthly Claimed Capability for that month. The purpose of this change was to simplify procurement and encourage provision of the black start service. The final method of procurement is competitive procurement as used by the Electric Reliability Council of Texas (ERCOT). Under this approach, ERCOT runs a market for black-start services. Interested participants submit an hourly standby cost in $/hr (e.g. $70 per hour), often termed an availability bid, that is unrelated to the capacity of the unit. Using various criteria, ERCOT evaluates these bids and the selected units are paid as bid, presuming an 85% availability. Each black-start unit must be able to demonstrate that it can start another unit in close proximity, in order to begin the islanding and synchronization of the grid. In other jurisdictions there are differing methods of procurement. The New Zealand System Operator procures the blackstart capability via competitive tender. Other jurisdictions also appear to have some sort of competitive procurement, albeit perhaps not as structured as that of ERCOT. These include the Alberta Electric System Operator, as well as Independent Electric System Operator of Ontario, both of which use a long-term "request for proposals" approach similar to New Zealand and ERCOT. The first black start on Germany's grid was tested in 2017 at WEMAG battery power station in Schwerin on a disconnected, isolated grid. The WEMAG battery plant proved that it can restore the power grid after major disruption or blackout.


Limitations on black start sources

Not all generating plants are suitable for black-start capability. With respect to the black-start capabilities, the generators are classified into two groups: * BS generators (also black-start units, BSU) capable of starting quickly using on-site resources. Typical examples are provided by; **
Hydropower Hydropower (from Ancient Greek -, "water"), also known as water power or water energy, is the use of falling or fast-running water to Electricity generation, produce electricity or to power machines. This is achieved by energy transformation, ...
that requires relatively small amounts of power to control the intake gates for its operation; **
Diesel generator A diesel generator (DG) (also known as a diesel genset) is the combination of a diesel engine with an electric generator (often an alternator) to generate electrical energy. This is a specific case of an engine generator. A diesel compress ...
units that can use a pre-charged battery for start; ** Smaller
gas turbine A gas turbine or gas turbine engine is a type of Internal combustion engine#Continuous combustion, continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas gene ...
generators can be started on battery power; * NBS generators ("non-black-start units", NBSU) that require external energy (cranking power) to start. A typical example is a
steam turbine A steam turbine or steam turbine engine is a machine or heat engine that extracts thermal energy from pressurized steam and uses it to do mechanical work utilising a rotating output shaft. Its modern manifestation was invented by Sir Charles Par ...
unit. Micro-hydro generator units usually rely on the grid for the frequency control and reactive power management and cannot be used as BS generators as well. An additional requirement for the BS generator is its ability to support a large reactive load of a long transmission line, so the faraway NBS units can be energized. A typical BS generator is a small (10-50 MW) hydro or gas turbine generation unit. The output of
variable renewable energy Variable renewable energy (VRE) or intermittent renewable energy sources (IRES) are renewable energy sources that are not dispatchable due to their fluctuating nature, such as wind power and solar power, as opposed to controllable renewable ener ...
(VRE) sources is not predictable, this makes them difficult to use for black start or support in the grid restoration, as the lack of control, inherent in VRE sources, might cause a weak grid emerging from a blackout to collapse yet again.
Wind turbine A wind turbine is a device that wind power, converts the kinetic energy of wind into electrical energy. , hundreds of thousands of list of most powerful wind turbines, large turbines, in installations known as wind farms, were generating over ...
s in particular are not always suitable for black start because wind may not be available when needed. Wind turbines, mini-hydro, or micro-hydro plants, are often connected to
induction generator An induction generator (or asynchronous generator) is a type of alternating current (AC) electrical generator that uses the principles of induction motors to produce electric power. Induction generators operate by mechanically turning their roto ...
s which are incapable of providing power to re-energize the network. In 2020, the 69MW Dersalloch
wind farm A wind farm, also called a wind park or wind power plant, is a group of wind turbines in the same location used to produce electricity. Wind farms vary in size from a small number of turbines to several hundred wind turbines covering an exten ...
black-started part of the Scotland grid, using virtual synchronous machines. The black-start unit must also be stable when operated with the large reactive load of a long transmission line. "Classic"
high-voltage direct current A high-voltage direct current (HVDC) electric power transmission system uses direct current (DC) for electric power transmission, in contrast with the more common alternating current (AC) transmission systems. Most HVDC links use voltages betwe ...
(HVDC) converters ( LCC-HVDC) cannot operate into a "dead" system, either, since they require commutation power from the system at the load end. A
pulse-width modulation Pulse-width modulation (PWM), also known as pulse-duration modulation (PDM) or pulse-length modulation (PLM), is any method of representing a signal as a rectangular wave with a varying duty cycle (and for some methods also a varying peri ...
(PWM)-based voltage-source converter HVDC ( VSC-HVDC) scheme has no such restriction.Beaty, H. Wayne; Fink, Donald G. (ed) '' Standard Handbook for Electrical Engineers (15th Edition)'', McGraw-Hill 2007 page 15-22


See also

*
Bootstrapping In general, bootstrapping usually refers to a self-starting process that is supposed to continue or grow without external input. Many analytical techniques are often called bootstrap methods in reference to their self-starting or self-supporting ...
*
Diesel generator A diesel generator (DG) (also known as a diesel genset) is the combination of a diesel engine with an electric generator (often an alternator) to generate electrical energy. This is a specific case of an engine generator. A diesel compress ...
* 2025 Iberian Peninsula blackout *
Power outage A power outage, also called a blackout, a power failure, a power blackout, a power loss, a power cut, or a power out is the complete loss of the electrical power network supply to an end user. There are many causes of power failures in an el ...
* Synchroscope


References


Sources

* * * *


Further reading

* 2007: Isemonger, A.G. "The Viability of the Competitive Procurement of Blackstart: Lessons from the RTOs" The Electricity Journal Volume 20, Issue 8, October 2007, Pages 60–67 * Brendan Kirby and Eric Hirst, Maintaining System Black Start In Competitive Bulk-Power Markets, American Power Conference, Chicago, Illinois, April 1999, available online at
Publications
* Lindsay Morris, Black Start: Preparedness for Any Situation, Power Engineering, Volume 115, Issue 7, July 2011, available online at
Black Start: Preparedness for Any Situation
*Rebecca Smith, Texas Grid Came Close to Bigger Disaster From Freeze, The Wall Street Journal, May 28, 2021, available online at
The Texas Grid Came Close to an Even Bigger Disaster During February Freeze
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