New load shedding program

In these situations, overall demand must be lowered, either by turning off service to some devices or cutting back the supply voltage brownouts , in order to prevent uncontrolled service disruptions such as power outages widespread blackouts or equipment damage. Distribution control centers may impose load shedding on service areas via rolling blackouts or by agreements with specific high-use industrial consumers to turn off equipment at times of system-wide peak demand.

The major disadvantage of load shedding is that the consumers are totally restricted from using electric power. This project mainly aims to address this problem by dividing the loads of the consumer into different priority groups and when it is required to do load shedding then the lowest priority loads of the consumer will only get disconnected from the power supply.

Thus providing consumers with the benefit of using electric power for their most needed high priority loads, even when load shedding is done. In this project when it is required to do load shedding, Power Line Communication is used for switching the loads of consumer.

Power Line Communication has proven to be a reliable communications technology for high bandwidth distribution of entertainment-grade HD video, gaming, internet access and other applications in homes. This same proven technology will allow the Conceptual design and also sourcing for the main components will also be included in this state.

In hardware design, design and building of associated circuitry, like interfacing relays, switches with microcontroller and power supply. Whereas, the software design, is to develop and program the microcontroller as per the project requirement. Full integrated hardware model showing the actual operating process of smart load shedding will be presented. Such action must be taken promptly and must be of sufficient magnitude to conserve essential load and enable the remainder of the system to recover from the under frequency condition.

Also, by preventing a major shutdown, restoration of the entire system to normal operation is greatly facilitated and expedited. Where individual operating utility companies are inter-connected, resulting in a power pool, it is essential that system planning and operating procedures be coordinated to provide a uniform automatic load shedding scheme.

The numbers of steps, the frequency levels and the amount of load to be shed at each step are established by agreement between the power pool members. This recovery is assisted by governor action on available spinning reserve generation, or by the addition of other generation to the system.

The recovery of system frequency to normal is likely to be quite slow and may extend over a period of several minutes. When 50 Hz operation has been restored to an island, then interconnecting tie lines with other systems or portions of systems can be synchronized and closed in.

The amount of load that can be restored is determined by the ability of the system to serve it. The criterion is that the available generation must always exceed the amount of load being restored so that the system frequency will continue to recover towards 50 Hz. Any serious decrease in system frequency at this point could lead to undesirable load shedding repetition, which could start a system oscillation between shedding and restoration. This would be a highly undesirable condition.

The availability of generation, either locally or through system interconnections, determines whether or not the shed load can be successfully restored. Therefore, a load restoration program usually incorporates time delay, which is related to the amount of time required to add generation or to close tie- lines during emergency conditions.

Also, both the time delay and the restoration frequency set points should be staggered so that the entire load is not reconnected at the same time. Reconnecting loads on a distributed basis also minimizes power swings across the system and thereby minimizes the possibility of initiating a new disturbance.

There should also be adequate time delay provided between load restoration steps to allow the system to stabilize before an additional block of load is picked up. They are the static relay, and electromechanical relay.

The operating characteristics and features of each of these relays are described in the following paragraphs. Basically, this relay consists of a highly stable, crystal-controlled oscillator which continuously supplies two mHz pulses to a binary counter. The counter, in conjunction with other logic circuitry, determines system frequency by counting the number of two mHz pulses which occur during a full cycle one period of power system voltage.

For any preset frequency, a specific number of pulses should occur during a one-cycle period. If the number of pulses is less than this specific number, it would indicate that system frequency is above the setting. Conversely, if the number of pulses is greater than this specific number, it indicates that the system frequency is less than the setting. For security reasons, an under frequency indication must occur for a minimum of three consecutive cycles before the relay produces an output.

This minimum time can be extended to 80 cycles by means of an adjustable auxiliary timer. If the system frequency should recover even for one cycle during the timing period, the timing circuits will be reset and the relay will immediately start monitoring system frequency again. The relay operating time is independent of the rate of change of the system frequency. Its basic principle of operation is the use of two separate coil circuits which provide increasing phase displacement of fluxes as the frequency decreases, thereby causing torque to be developed in the cup unit to close the tripping contacts.

The quantity of torque produced is proportional to the sine of the angle between these two fluxes. As the frequency decays the angular displacement increases, thereby increasing the torque produced. If the frequency decays rapidly the torque will increase rapidly and cause the relay to close its contacts in less time.

Thus the relay operating time is a function of the rate-of-change of frequency. The CFF relay setting is continuously adjustable over a range of 56 to A literature review has been carried out as per this requirement and summarized as follows: 3. A low to high digital pulse will be modulated over the power line in this case and the receiving side will simply demodulate this pulse back from the carrier and the trigger circuit will then activate ON or OFF operation.

This is not a practical approach as a noise signal may be wrongly interpreted as ON or OFF signal by the modem circuit. To prevent false triggering, addresses are given for the PLC modems. In this project we will have same address for all the PLC modems, since every consumer connected to a centre is expected to receive and interpret the data sent from the distribution centre in the same manner.

M-ary Modulation a. M-ASK b. M-PSK c. M-ASK 2. Spread Spectrum Techniques a. Multiplexing Techniques a. For low cost, low data rate applications, such as power line protection and telemetering, FSK is seen as a good solution. For data rates up to 1Mbps, the It is deemed necessary to make dynamic simulations of the particular group of machines in the system that have major influence on system operation.

A combined system for monitoring of generation and load demand to load shedding in case of unbalance between them has been developed. An integrated software has been designed to perform this vital task. The developed system is composed of three different modules; input and general studies modules are constructed and carried out supported by the Electrical Transient Analyzer Program ETAP.

Outputs of these modules are automatically collected and indexed within the knowledge base module. The knowledge base module contains mainly the generator power chart constraints, generator thermal limitations and load shedding design rules.

Also it contains switching events rules as well as a list of load categories recommended by process engineers. The knowledge base and output modules are developed using Matlab Simulink. As well a graphic module has been developed to visualize the system and record generator frequency, generator exciter voltage, generator output power and generator current.

The developed system is designed in a modular form and consists mainly of three modules as described in the following sections. This module constructs the data base which represents the plant. The input module specifies the plant description, edits the single line diagram and defines the operation of different loads using colour code.

Using this module, the power plant will be fully described and the following data is transferred to the knowledge base module automatically:. Design active power is defined as the active power for a driven machine or load in its normal mode of operation,. Design particular power is defined as the active power for a driven machine or load in a load in a special loading conditions,. This module is responsible for carrying out all plant calculations such as load flow study and transient stability study.

The load flow calculation tool specifies the plant operating conditions. It generates branch current loading, branch losses, bus loading and transformer loading. It generates also alarms for critical equipment and critical buses.

For monitoring of motors operation in large plants, the load flow runs are made based on possible load and their results are considered as initial operating conditions. These runs are then repeated for load shedding steps to check the power system operating conditions at these circumstances. This is performed to investigate dynamic conditions on power system during generation drop. The dynamic simulations of a particular group of machines in the system that are known to have important influence on the system operation is performed.

The aim of this study is to calculate system frequency variations, power output…etc. This module is the heart of the system. It consists of two types of the rule base that manipulates the load shedding steps. Type I is a time event of generation dropping and load shedding actions in the plant. Type II is concerned with generator stability check. This expert knowledge is normally stored separately from the procedural part of the program.

If it is desired to shed network by opening a circuit breaker, a rule could be formed expressing such knowledge in the form of IF X THEN Y , where X is the premise or antecedent and Y is the conclusion or consequent, which is either True or false. The rule base specifies the process constraints and the events expected in each plant. This part of the rule base has a storage capacity of time events from t1 to t Each time event allows 10 actions to be defined.

This type of rule base identifies the level of control and monitoring for generation and load demand as well as recommended settings. It may include up to rules for a similar number of motors. It classifies the motors based on motor type, motor ratings and operation criteria as well. The following constraints are some rules in the rule base:. The generator thermal withstand monitoring unit: This part covers many items such as generator manufacturers thermal withstand characteristics as related to the fault current and duration that the machine can withstand.

This unit is of prime importance to check continuously the generator loading to decide the instant of load shedding initiation. Generator power angle check unit: This unit provides the check for power angle as a stability index for operating generator. Load shedding control unit: This unit determines the number of loads, the steps, and the duration of each step to apply a proper load shedding scheme.

Each Rule corresponds to a path in the decision tree in Fig 3 that provides an established technique for solving classification problems, which have a small number of categories stable versus unstable. Rule 1: IF the power angle of each generator in the system with respect to fixed reference in the system increases to a maximum value and then decreases THEN the system is considered as synchronously stable no load shedding.

AND the final voltage profile of the system is unacceptable due to violation of the voltage limit in one more of the system bus THEN load shedding is needed to correct the final voltage profile. Rule 5: IF the power angle of one or more generators in the system with respect to fixed reference in the system increases indefinitely THEN the system is considered as synchronously unstable.

The components of the new expert system are shown in Fig. Wrong email address. You're going to remove this assignment. Are you sure? Yes No. Politecnico di Milano, Milan. Keywords power distribution economics load shedding electrical system operation power plant DILS distributed interruptible load shedding Power outages Supply and demand Demand forecasting Stochastic processes Approximation methods Uncertainty handling Load management uncertain system Black out demand side management interruptible load stochastic approximation power distribution economics load shedding electrical system operation power plant DILS distributed interruptible load shedding Power outages Supply and demand Demand forecasting Stochastic processes Approximation methods Uncertainty handling Load management uncertain system Black out demand side management interruptible load stochastic approximation.

Additional information Data set: ieee. Publisher IEEE. Fields of science No field of science has been suggested yet. You have to log in to notify your friend by e-mail Login or register account. Outreach Education. Load-shedding Ballast A load-shedding ballast reduces power demand by dimming the lighting in a building when the building's peak electric demand is high or when the available supply is limited.

Read more about this device: Lighting Research Center paves the way for commercially viable, high efficiency demand response ballast Lighting Research Center and OSRAM SYLVANIA demonstrate new load-shedding technology to help reduce peak electric loads on the nation's stressed grid Energy-efficient, load-shedding lighting technology: A cost-effective means of reducing peak electric demand!

Advancing the effective use of light for society and the environment.