Powersystemautomationintroduction-170829144034 (1).pdf

POWER SYSTEM AUTOMATION Mohammed Naser Automation and Control Engineer

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 devices (IED), control and automation capabilities within the substation, and control commands from remote users to control power-system devices.

Electrical 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. Between the generating station and consumer, electric power may flow through several substations at different voltage levels. A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages. Substations may be owned and operated by an electrical utility, or may be owned by a large industrial or commercial customer. Generally substations are unattended, relying on SCADA for remote supervision and control.

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Intelligent electronic devices (IED) 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.

circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current, typically resulting from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected. transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. capacitor is a passive two-terminal electrical component that stores electrical energy in an electric field microprocessor is a computer processor which incorporates the functions of a computer's central processing unit (CPU) on a single integrated circuit (IC), or at most a few integrated circuits. The microprocessor is a multipurpose, clock driven, register based, digital-integrated circuit which accepts binary data as input, processes it according to instructions stored in its memory, and provides results as output. Microprocessors contain both combinational logic and sequential digital logic. Microprocessors operate on numbers and symbols represented in the binary numeral system. 3

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. 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.

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Hardware structure of the power-system automation

1-( Data acquisition ) The instrument 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 equipment. 2- ( Main processing instrumentation and control (I&C) device - Remote Terminal Unit (RTU) 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.”

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- 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 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) 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 RTU

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4- Controlling (output) devices - Load tap changer (LTC) 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.

5- 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.

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Applications

1- Overcurrent protection All lines and all electrical equipment must be protected against prolonged Overcurrent. 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 circuits after a suitable time delay.

2- Supervisory control and data acquisition (SCADA) 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. Power system elements ranging from pole-mounted switches to entire power plants can be controlled remotely over long distance communication links. Remote switching, telemetering of grids (showing voltage, current, power, direction, consumption in kWh, etc.), even automatic synchronization is used in some power systems.

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THANK YOU

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