Power system automation
Encyclopedia
Power system automation is the act of automatically controlling the power system via instrumentation and control devices. Substation
automation refers to using data from Intelligent electronic device
s (IED), control and automation capabilities within the substation, and control commands from remote users to control power system devices.
Since full substation automation relies on substation integration, the terms are often used interchangeably. Power system automation includes processes associated with generation and delivery of power. Monitoring and control of power delivery systems in the substation and on the pole top reduce the occurrence of outages and shorten the duration of outages that do occur. The IEDs, communications protocols, and communications methods, work together as a system to perform power system automation.
The term “power system” describes the collection of devices that make up the physical systems that generate, transmit, and distribute power. The term “instrumentation and control (I&C) system” refers to the collection of devices that monitor, control, and protect the power system.
Data acquisition: Data acquisition refers to acquiring, or collecting, data. This data is collected in the form of measured analog current or voltage values or the open or closed status of contact points. Acquired data can be used locally within the device collecting it, sent to another device in a substation, or sent from the substation to one or several databases for use by operators, engineers, planners, and administration.
Supervision: Computer processes and personnel supervise, or monitor, the conditions and status of the power system using this acquired data. Operators and engineers monitor the information remotely on computer displays and graphical wall displays or locally, at the device, on front-panel displays and laptop computers.
Control: Control refers to sending command messages to a device to operate the I&C and power system devices. Traditional supervisory control and data acquisition (SCADA) systems rely on operators to supervise the system and initiate commands from an operator console on the master computer. Field personnel can also control devices using front-panel push buttons or a laptop computer.
In addition, another task is power system integration, which is the act of communicating data to, from, or among IEDs in the I&C system and remote users. Substation integration refers to combining data from the IED’s local to a substation so that there is a single point of contact in the substation for all of the I&C data.
The power system automation processes rely on data acquisition; Power system supervision and power system control all working together in a coordinated automatic fashion. The commands are generated automatically and then transmitted in the same fashion as operator initiated commands.
Main processing instrumentation and control (I&C) device
The I&C devices built using microprocessors are commonly referred to as intelligent electronic devices (IEDs). Microprocessors are single chip computers that allow the devices into which they are built to process data, accept commands, and communicate information like a computer. Automatic processes can be run in the IEDs. Some IEDs used in power system automation are:
Remote Terminal Unit, RTU: A remote terminal unit is an IED that can be installed in a remote location, and acts as a termination point for field contacts. A dedicated pair of copper conductors is used to sense every contact and transducer value. These conductors originate at the power system device, are installed in trenches or overhead cable trays, and are then terminated on panels within the RTU. The RTU can transfer collected data to other devices and receive data and control commands from other devices. User programmable RTUs are referred to as “smart RTUs.”
Meter: A meter
is an IED that is used to create accurate measurements of power system current, voltage, and power values. Metering values such as demand and peak are saved within the meter to create historical information about the activity of the power system.
Digital fault recorder: A digital fault recorder (DFR) is an IED that records information about power system disturbances. It is capable of storing data in a digital format when triggered by conditions detected on the power system. Harmonics, frequency, and voltage are examples of data captured by DFRs.
Programmable logic controller (PLC): A Programmable Logic Controller (PLC)
can be programmed to perform logical control. As with the RTU, a dedicated pair of copper conductors for each contact and transducer value is terminated on panels within the PLC.It is like a work-horse which work upon the command given by their master.
Protective relay
: A protective relay is an IED designed to sense power system disturbances and automatically perform control actions on the I&C system and the power system to protect personnel and equipment. The relay has local termination so that the copper conductors for each contact do not have to be routed to a central termination panel associated with RTUs and PLCs.
changer (LTC): Load tap changers are devices used to change the tap position on transformers. These devices work automatically or can be controlled via another local IED or from a remote operator or process.
Recloser
controller: Recloser controllers remotely control the operation of automated reclosers and switches. These devices monitor and store power system conditions and determine when to perform control actions. They also accept commands from a remote operator or process.
. If the cause of the overcurrent is nearby then automatically that current is interrupted immediately. But if the cause of the overcurrent is outside the local area then a backup
provision automatically disconnects all affected circuit
s after a suitable time delay.
Note that disconnection can, unfortunately, have a cascade
effect, leading to overcurrent in other circuits that then also must therefore disconnect automatically.
Also note that generator
that suddenly have lost their load because of such a protection operation will have to shut down automatically immediately, and it may take many hours to restore a proper balance between demand and supply
in the system, partly because there must be proper synchronization
before any two parts of the system can be reconnected.
Reclosing operations of circuit breakers usually are attempted automatically, and often are successful during thunderstorms, for example.
Some power stations can control other stations via communication links over long distances.
Remote switching, telemetering of home grids (showing voltage, current, power, direction, consumption in kWh, etc.), even automatic synchronization is used in some power systems.
Electrical substation
A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions...
automation refers to using data from Intelligent electronic device
Intelligent electronic device
An Intelligent Electronic Device is a term used in the electric power industry to describe microprocessor-based controllers of power system equipment, such as circuit breakers, transformers, and capacitor banks.-Description:...
s (IED), control and automation capabilities within the substation, and control commands from remote users to control power system devices.
Since full substation automation relies on substation integration, the terms are often used interchangeably. Power system automation includes processes associated with generation and delivery of power. Monitoring and control of power delivery systems in the substation and on the pole top reduce the occurrence of outages and shorten the duration of outages that do occur. The IEDs, communications protocols, and communications methods, work together as a system to perform power system automation.
The term “power system” describes the collection of devices that make up the physical systems that generate, transmit, and distribute power. The term “instrumentation and control (I&C) system” refers to the collection of devices that monitor, control, and protect the power system.
Automation tasks
Power system automation is composed of several tasks.Data acquisition: Data acquisition refers to acquiring, or collecting, data. This data is collected in the form of measured analog current or voltage values or the open or closed status of contact points. Acquired data can be used locally within the device collecting it, sent to another device in a substation, or sent from the substation to one or several databases for use by operators, engineers, planners, and administration.
Supervision: Computer processes and personnel supervise, or monitor, the conditions and status of the power system using this acquired data. Operators and engineers monitor the information remotely on computer displays and graphical wall displays or locally, at the device, on front-panel displays and laptop computers.
Control: Control refers to sending command messages to a device to operate the I&C and power system devices. Traditional supervisory control and data acquisition (SCADA) systems rely on operators to supervise the system and initiate commands from an operator console on the master computer. Field personnel can also control devices using front-panel push buttons or a laptop computer.
In addition, another task is power system integration, which is the act of communicating data to, from, or among IEDs in the I&C system and remote users. Substation integration refers to combining data from the IED’s local to a substation so that there is a single point of contact in the substation for all of the I&C data.
The power system automation processes rely on data acquisition; Power system supervision and power system control all working together in a coordinated automatic fashion. The commands are generated automatically and then transmitted in the same fashion as operator initiated commands.
Data acquisition
The instruments transformers with protective relays are used to sense the power system voltage and current. They are physically connected to power system apparatus and convert the actual power system signals. The transducers convert the analog output of an instrument transformer from one magnitude to another or from one value type to another, such as from an ac current to dc voltage. Also the input data is taken from the auxiliary contacts of switch gears and power system control equipments.Main processing instrumentation and control (I&C) device
The I&C devices built using microprocessors are commonly referred to as intelligent electronic devices (IEDs). Microprocessors are single chip computers that allow the devices into which they are built to process data, accept commands, and communicate information like a computer. Automatic processes can be run in the IEDs. Some IEDs used in power system automation are:
Remote Terminal Unit, RTU: A remote terminal unit is an IED that can be installed in a remote location, and acts as a termination point for field contacts. A dedicated pair of copper conductors is used to sense every contact and transducer value. These conductors originate at the power system device, are installed in trenches or overhead cable trays, and are then terminated on panels within the RTU. The RTU can transfer collected data to other devices and receive data and control commands from other devices. User programmable RTUs are referred to as “smart RTUs.”
Meter: A meter
Smart meter
A smart meter is usually an electrical meter that records consumption of electric energy in intervals of an hour or less and communicates that information at least daily back to the utility for monitoring and billing purposes. Smart meters enable two-way communication between the meter and the...
is an IED that is used to create accurate measurements of power system current, voltage, and power values. Metering values such as demand and peak are saved within the meter to create historical information about the activity of the power system.
Digital fault recorder: A digital fault recorder (DFR) is an IED that records information about power system disturbances. It is capable of storing data in a digital format when triggered by conditions detected on the power system. Harmonics, frequency, and voltage are examples of data captured by DFRs.
Programmable logic controller (PLC): A Programmable Logic Controller (PLC)
Programmable controller
Programmable controller may be:* Programmable logic controller* Programmable automation controller* Programmable Interrupt Controller* Universal remote...
can be programmed to perform logical control. As with the RTU, a dedicated pair of copper conductors for each contact and transducer value is terminated on panels within the PLC.It is like a work-horse which work upon the command given by their master.
Protective relay
Protective relay
In electrical engineering, a protective relay is a complex electromechanical apparatus, often with more than one coil, designed to calculate operating conditions on an electrical circuit and trip circuit breakers when a fault is detected...
: A protective relay is an IED designed to sense power system disturbances and automatically perform control actions on the I&C system and the power system to protect personnel and equipment. The relay has local termination so that the copper conductors for each contact do not have to be routed to a central termination panel associated with RTUs and PLCs.
Controlling (output) devices
Load tapTap (transformer)
A transformer tap is a connection point along a transformer winding that allows a certain number of turns to be selected. This means, a transformer with a variable turns ratio is produced, enabling voltage regulation of the output...
changer (LTC): Load tap changers are devices used to change the tap position on transformers. These devices work automatically or can be controlled via another local IED or from a remote operator or process.
Recloser
Autorecloser
In electric power distribution, a recloser, or autorecloser, is a circuit breaker equipped with a mechanism that can automatically close the breaker after it has been opened due to a fault. Reclosers are used on overhead distribution systems to detect and interrupt momentary faults...
controller: Recloser controllers remotely control the operation of automated reclosers and switches. These devices monitor and store power system conditions and determine when to perform control actions. They also accept commands from a remote operator or process.
Communications devices
Communications processor: A communications processor is a substation controller that incorporates the functions of many other I&C devices into one IED. It has many communications ports to support multiple simultaneous communications links. The communications processor performs data acquisition and control of the other substation IEDs and also concentrates the data it acquires for transmission to one or many masters inside and outside the substation.Overcurrent protection
All lines and all electrical equipment must be protected against prolonged overcurrentOvercurrent
In electricity supply, overcurrent or excess current is a situation where a larger than intended electric current exists through a conductor, leading to excessive generation of heat, and the risk of fire or damage to equipment. Possible causes for overcurrent include short circuits, excessive load,...
. If the cause of the overcurrent is nearby then automatically that current is interrupted immediately. But if the cause of the overcurrent is outside the local area then a backup
Backup
In information technology, a backup or the process of backing up is making copies of data which may be used to restore the original after a data loss event. The verb form is back up in two words, whereas the noun is backup....
provision automatically disconnects all affected circuit
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
s after a suitable time delay.
Note that disconnection can, unfortunately, have a cascade
Cascading failure
A cascading failure is a failure in a system of interconnected parts in which the failure of a part can trigger the failure of successive parts.- Cascading failure in power transmission :...
effect, leading to overcurrent in other circuits that then also must therefore disconnect automatically.
Also note that generator
Generator
Generator may refer to:* Electrical generator* Engine-generator, an electrical generator, but with its own engine.* Generator , any of several closely related usages in mathematics.Computing:...
that suddenly have lost their load because of such a protection operation will have to shut down automatically immediately, and it may take many hours to restore a proper balance between demand and supply
Supply and demand
Supply and demand is an economic model of price determination in a market. It concludes that in a competitive market, the unit price for a particular good will vary until it settles at a point where the quantity demanded by consumers will equal the quantity supplied by producers , resulting in an...
in the system, partly because there must be proper synchronization
Synchronization
Synchronization is timekeeping which requires the coordination of events to operate a system in unison. The familiar conductor of an orchestra serves to keep the orchestra in time....
before any two parts of the system can be reconnected.
Reclosing operations of circuit breakers usually are attempted automatically, and often are successful during thunderstorms, for example.
Supervisory Control and Data Acquisition
It is the system which transmits and receives logic or data from events of controls, metering, measuring, safety and monitoring of process devices such as Electrical equipment, Instrumentation devices, telecommunication on industrial applications.Some power stations can control other stations via communication links over long distances.
Remote switching, telemetering of home grids (showing voltage, current, power, direction, consumption in kWh, etc.), even automatic synchronization is used in some power systems.
See also
- Automatic generation controlAutomatic generation controlIn an electric power system, automatic generation control is a system for adjusting the power output of multiple generators at different power plants, in response to changes in the load. Since a power grid requires that generation and load closely balance moment by moment, frequent adjustments to...
- Smart grid
- Smart meterSmart meterA smart meter is usually an electrical meter that records consumption of electric energy in intervals of an hour or less and communicates that information at least daily back to the utility for monitoring and billing purposes. Smart meters enable two-way communication between the meter and the...
- International Council on Large Electric SystemsInternational Council on Large Electric SystemsThe International Council on Large Electric Systems or CIGRE is a world organization in the field of high voltage electricity. It was founded in Paris, France in 1921...
(CIGRE)