Control And Automation Of Electrical Power Distribution Systems Pdf


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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.

Those familiar with industrial instrumentation will find much within the electric power industry remarkably familiar in concept. Within each of those smaller processes in a large electrical power system there exist automatic monitoring and control systems very similar to industrial process controls. A general block diagram showing the essential components of a feedback control system used elsewhere in this book applies to electrical power system automation as well:. Measurement devices in an electrical power system usually take the form of instrument transformers designed to represent high voltage and high current quantities as smaller, proportionate electrical signals. Controllers take the form of protective relays and other control systems designed to display and record the measured quantities, as well as take an automatic control action.

Power-system automation

Those familiar with industrial instrumentation will find much within the electric power industry remarkably familiar in concept. Within each of those smaller processes in a large electrical power system there exist automatic monitoring and control systems very similar to industrial process controls.

A general block diagram showing the essential components of a feedback control system used elsewhere in this book applies to electrical power system automation as well:. Measurement devices in an electrical power system usually take the form of instrument transformers designed to represent high voltage and high current quantities as smaller, proportionate electrical signals.

Controllers take the form of protective relays and other control systems designed to display and record the measured quantities, as well as take an automatic control action. Modern electrical power automation systems, like industrial automation, also employ sophisticated digital communication subsystems to exchange critical data such as power flow and fault diagnosis across wide regions.

Let us examine electric power substations as an example of automation. An example of a single-line diagram showing multiple substations appears here:.

Loads also appear as circles, but labeled uniquely. Circuit breakers used to interrupt the flow of power during full-load and fault conditions appear as squares, shown here with color-coded states. Disconnect switches used to isolate components from power during maintenance operations appear as standard schematic switch symbols: a line broken by a diagonal line segment.

Short line segments joining circuit breakers and disconnects with other devices in each station represent busses , which are sets of rigid metal conductors suspended by insulators. Longer lines connecting stations to each other represent transmission or distribution power lines. Transformers , used to step voltage up and current down for efficient long-distance transmission, or vice-versa for distribution and end-use, appear as standard schematic winding symbols.

This simplification is similar to the way road maps show streets and highways as single lines but generally do not show the number of lanes within each road. Within each of these substations you can see circuit breakers and disconnect switches used to route the flow of electricity from sources to loads.

These devices are analogous to control valves and block valves used to control fluid motion in industrial processes. These protective relays sense voltage and current conditions through instrument transformers stepping high voltage down to safe sensing levels Potential Transformers, or PTs and stepping line current down to safe levels Current Transformers, or CTs. An example of a single-line diagram showing such an automated protection system for one of the power transformers in this system appears here:.

Each protective relay function appears as a small circle enclosing a number, representing an industry-standardized code for that protective function e. In this particular case, any condition of overcurrent or current imbalance for this transformer causes the lockout relay 86 to trip, which in turn commands both line and load circuit breakers to trip, isolating the power transformer and thereby protecting it from harm.

A single potential transformer array PT steps down the high line voltage to a safe level typically volts nominal for the wattmeter to read. A set of current transformers CTs step line current down to safe levels typically 5 amps at full load for the wattmeter and protective relays to read.

As you can see, the disconnect switches have no connection to the automated system because they are manually-controlled devices, analogous to manual block valves flanking an automatic control valve in a process pipe. Now that we know the functions of instrument transformers, protective relays, circuit breakers, and disconnect switches, we may examine some photographs of these power system components. First, we will examine some potential transformers PTs , sometimes referred to as voltage transformers VTs.

The left-hand photograph shows a set of three PTs, each one used to sense phase-to-ground voltage in a kV 3-phase power bus within a substation. The right-hand photograph shows a single PT sensing phase-to-phase voltage i.

This is analogous to the industrial instrumentation signal standard of mA representing such things as pressure, flow, and temperature: a relatively small electrical signal is used as a representation of some other real-world measurement. Next we will examine some current transformers CTs. The left-hand photograph shows a current transformer with a amp ratio, which means a line current of amps AC passing through the horizontal metal bar will induce a secondary winding current of 5 amps AC available at the screw terminals on top of this CT.

All of these CTs output a nominal current of 5 amps AC at full load rating, which is a common CT signal standard within the electrical power industry, like volts is for PT output signals. Together, PTs and CTs constitute the primary sensing elements of electrical power measurement, control, and protection systems. One of the tasks of metering and protection technicians in the electric power industry is to periodically check the accuracy and performance of these instrument transformers, just as an industrial instrument technician periodically checks the calibration of process sensing elements and transmitters.

Next we will examine some of the panel-mounted instruments receiving signals from PTs and CTs. First are simple meters, designed to display system measurements to human operators. These instruments are labeled with high ranges despite the fact that their actual driving signals are relatively small e. This provides operators with remote viewing of device status, which is then displayed as different colors red or green on a graphic single-line diagram of the power system. The scale of this particular display is such that individual circuit breakers are not represented, showing entire substations as single colored squares.

However, more detailed diagrams are viewable by selecting a particular substation on this screen, these detailed displays showing individual circuit breakers and other associated equipment within that substation:. These automatic control devices have existed in one form or another for over a century, beginning with crude electromechanical designs and now culminating in state-of-the-art microprocessor-based computing machines.

Relay functions are commonly designated by numerical codes standardized by ANSI , some of which will be listed in this section. A series of electromechanical protective relays appears in the following photographs, taken at a large substation.

The middle photograph shows a set of transformer differential current relays ANSI code 87 designed to compare the amount of current in the primary and secondary windings of a transformer, tripping circuit breakers on both sides of the transformer in the event a transformer fault is detected i. The right-hand photograph shows a set of overpressure relays ANSI code 63 designed to trip circuit breakers feeding power to a device if the pressure inside that device rises to unacceptable levels:.

A routine task for relay technicians working on electromechanical relays is periodic recalibration of these devices. Since they contain potentiometers, magnets, inductive coils, and moving parts they are susceptible to calibration drift just like any other analog electronic or mechanical device. Modern digital electronic protective relays are also panel-mounted, but of course contain no moving parts and are much more capable in terms of their ability to discriminate between normal operating conditions and faulted conditions meriting the tripping of circuit breakers.

The following photographs show some examples of these devices. The left-hand photograph shows a transformer protection relay, incorporating the differential current ANSI code 87 protection of the previous electromechanical relay plus a number of other features including instantaneous and time-overcurrent functions.

The right-hand photograph shows a pair of digital relays, the upper one providing instantaneous overcurrent ANSI code 50 plus time-overcurrent ANSI code 51 plus circuit breaker reclosing ANSI code 79 functionality, tripping the circuit breaker in the event of excessive current, and then re-closing that same circuit breaker a short moment after to check if the fault has cleared.

One of the benefits of digital protective relays is their remarkable stability compared to electromechanical relays, being virtually immune to calibration drift.

This translates to less routine maintenance for relay technicians. Not only do modern protective relays perform their basic system protection functions, but they also record data for later retrieval and analysis by relay technicians and protection engineers. These relays, being microprocessor based, may also be interconnected using high-speed data networks to exchange data with each other as part of certain protection strategies.

These new capabilities, coupled with the need to maintain accurate archives of digital relay configuration files, means the job of the relay technician has evolved: there is less routine calibration work, but more routine record-keeping and high-level diagnostic work.

Finally, we have the final control elements of the electric power industry: circuit breakers and disconnects. These two types of devices are common in that they both serve to connect and disconnect portions of a power system.

They differ in their ability to interrupt current: circuit breakers are built with very rugged electrical contacts capable of safely and reliably interrupting huge magnitudes of electric current including currents arising from short-circuit faults in the power system , whereas disconnects are switches that cannot make or break such large currents, and are intended to be operated only when the series-connected circuit breaker is open tripped.

The following photographs show sets of three-phase kV disconnects, the left-hand photograph showing a set in the closed position and the right-hand photograph showing a set in the open position:. As you can see, a high-voltage disconnect is nothing more than an open-air knife switch. Some are manually operated by a lever or a hand crank while others use an electric motor for remote operation by a SCADA system or by an operator in a substation control room.

Medium-voltage and high-voltage circuit breakers come in a variety of shapes and sizes. Perhaps the most significant difference between them is the method s employed to extinguish the electric arc formed when the contacts separate to interrupt line current. The photograph on the left shows a legacy oil-tank circuit breaker in a kV substation yard, consisting of three separate tanks containing contacts to interrupt one phase each.

All three contacts operate simultaneously by the same mechanism. Safe and effective interruption of electric current at these elevated potentials demands quick contact action, and this is possible only with some form of stored-energy mechanism inside the circuit breaker. Some large circuit breakers use reservoirs filled with compressed air as the actuating medium, the reservoir maintained in a state of high pressure by an electric air compressor.

Other circuit breakers use mechanical springs pre-charged by an electric motor and gear mechanism. This volt battery bank is maintained in a continuous state of charge by an AC-DC battery charger fed from the AC power source not shown. In summary, electric power systems employ automation to measure power conditions and take protective action when needed in the event of major line or device faults.

These automated systems resemble industrial process control and safety systems in their three-part division sensing, control, and final action as well as in their graphical representation, calibration, and other maintenance. Don't have an Control account? Create one now. Forgot your password? Click here. Latest Projects Education. I - Fundamentals Vol. II - Instrumentation Vol. III - Measurement Vol. IV - Control Vol. V - Reference Worksheets.

Textbook Introduction to Power System Automation. A general block diagram showing the essential components of a feedback control system used elsewhere in this book applies to electrical power system automation as well: Measurement devices in an electrical power system usually take the form of instrument transformers designed to represent high voltage and high current quantities as smaller, proportionate electrical signals. An example of a single-line diagram showing such an automated protection system for one of the power transformers in this system appears here: Each protective relay function appears as a small circle enclosing a number, representing an industry-standardized code for that protective function e.

The right-hand photograph shows a set of overpressure relays ANSI code 63 designed to trip circuit breakers feeding power to a device if the pressure inside that device rises to unacceptable levels: A routine task for relay technicians working on electromechanical relays is periodic recalibration of these devices. The following photographs show sets of three-phase kV disconnects, the left-hand photograph showing a set in the closed position and the right-hand photograph showing a set in the open position: As you can see, a high-voltage disconnect is nothing more than an open-air knife switch.

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Application of wireless power system automation for electrical distribution system of Van, Turkey

We have extensive experience in all areas of industrial electrical systems for both greenfield projects and the expansion of existing facilities. Process equipment is often considered to be the longest lead item, but with the quantity of major projects now being constructed worldwide, the major electrical items such as substations and transformers are now on the critical path. We are constantly in touch with suppliers and have current information on the lead times of such equipment. In addition, the negotiations with the power utility can have a critical influence on a schedule. Our skill in developing options and identifying solutions is particularly valuable in the modernization of operating facilities, where changeover risks must be successfully managed. We work with customers to implement plans and procedures that minimize downtime and loss of income. We are experts in protective coordination, arc flash, load flow, harmonics, insulation coordination, reliability, motor starting, grounding, and short circuit studies.

Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. Many of the most promising technologies under development for improving the power system may not harden it against terrorist attack, but they often will improve grid resilience and response and recovery. This chapter assesses research needs for reducing the risk from terrorist attacks in the context of overall power delivery system needs. It also notes alternative strategies by which the electric power system could be guided to greater robustness. As discussed in Chapter 2, recent decades have witnessed chronic underinvestment in sustaining and upgrading the U.

Journal of Control, Automation and Electrical Systems publishes original research papers as well as tutorials on industrial automation, intelligent systems, robotics, instrumentation, power electronics, power systems and control theory and applications. Issue 2, April Rights and permissions. Springer policies. Combines theoretical developments and application studies on highly promising themes involving the state-of-the-art research Offers a truly interdisciplinary forum in industrial automation, intelligent systems, robotics, control theory and power systems. Offers a highly respected and reliable international forum and efficient peer-review. Excellent response time from submission to first decision.

International Journal of Electrical Power & Energy Systems

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A multi-agent framework for power system automation free download With the growing scale of power transmission grids, the complexity of power system automation has increased dramatically during the past two decades. Over the last decade, there have been many changes in power systems in terms of their fundamental. Power system insulator condition monitoring automation using mean shift tracker-FIS combined approach free download Within the hierarchy of power system , distribution system automation plays a crucial role to provide reliable service to customers. Though initially computer aided automation started as substation monitoring system SMS just for monitoring some key parameters such as.

Power systems

Electric power distribution is the final stage in the delivery of electric power ; it carries electricity from the transmission system to individual consumers. Distribution transformers again lower the voltage to the utilization voltage used by lighting, industrial equipment and household appliances. Often several customers are supplied from one transformer through secondary distribution lines. Commercial and residential customers are connected to the secondary distribution lines through service drops. Customers demanding a much larger amount of power may be connected directly to the primary distribution level or the subtransmission level. The transition from transmission to distribution happens in a power substation , which has the following functions: [2].

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Electric power distribution

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