ABSTRACTAutomaticsynchronization is widely used to connect more than one alternators or analternator with busbar. The main task of a synchronizer is to capture thevoltage, frequency and phase sequence between the alternators accurately andrapidly. The manual methods of synchronization demand a skilled operator.
Underemergency condition such as synchronizing of large machine a very fastoperation become more difficult which may not be possible for human operation.Thus, there is a need of auto synchronizer in a power station. This projectdescribes a microprocessor based setup for synchronizing a three-phasealternator to bus bar. The developed automatic synchronization unit is fast,cost effective and reliable.
CHAPTER 1INTRODUCTIONIntroductionElectricalpower system mainly consists of an alternators/generator, transmission lines,and supplies large numbers of widely distributed loads. In many cases, there isa need to connect more than one generator to the system. It is known that loadon a power system not remain constant and varies in a discreate manner. To copewith requirement of variable load and continuity of supply, synchronization ofalternator is necessary. Some of thebenefits of operating alternator in parallel with another alternator or bus barare increased reliability, expandability, flexibility, serviceability andefficiency. For, an efficient operation of synchronization, the voltage, phase sequenceand frequency must be in a suitable limit.
Severe damage to the alternator aswell as system may result if it is allowed to connect to the system above andbelow the safe levels. Therefore, theautomatic synchronizing device plays an important role in synchronization. Formany years, the researchers have done so much work to develop the high performance-synchronizingdevice. The main problems of connecting an alternator to an electrical system arethe limits of the delta phase sequence, the delta frequency, and the deltavoltage magnitude. These problemsare summarized below: 1) DeltaFrequency Delta frequency is the relativefrequency of an alternator with respect to the busbar. If the differencebetween frequency of alternator and bus bar then this also cause a shock. 2) DeltaVoltage Magnitude Delta voltage magnitude is therelative magnitude of an alternator with respect to bus bar. There are twocases that may occur in this case i.
Lowalternator voltage ii. Highalternator voltage Excessively low alternator terminalvoltage during the synchronization could cause stability problems due to theweak magnetic circuit between the generator and the system. Excessively high alternator terminalvoltage during the synchronization will create a large reactive power flow fromthe system to the generator which can damage the generator shaft and mechanicalshock to the stator windings.
3) DeltaPhase SequenceWhen we connect an alternator to anelectrical system with a high delta phase sequence between the alternator andthe bus bar causes a shock to the alternator. This shock may create stress onprime shaft. Therefore, it is necessary to keep the three synchronizingparameters within acceptable limits. There are several methods available forgenerator parameters measurements; most of them can be categorized into eitherhardware based or software based methods.
Problem StatementSynchronization means all the parametersare matched before the circuit breaker is closed. All the conditions areclearly illustrated in the previous section. If there is difference between thefrequencies of alternator and bus bar this is called “Slip”.A faulty synchronization isthat in which all the three conditions are not in acceptable limits. Accordingto IEEE C50.12 and IEEE C50.13 the faulty synchronization as closing thebreaker outside the following limits: • Phase: ±10 degrees.
• Voltage: 0 to +5 percent. • Slip: ±0.067 Hz. For a fast synchronization,manual methods become insufficient for the synchronization process to do inrequired limits that may result in the sever damage or loss. These problems areserious especially when the alternators are far away from each other.Objective Our mainobjective of our project is to make an efficient synchronization device thatwill able to connect the alternator to busbar within permissible limits thatare defined.
Proposed model is developed with microprocessor 8085. A singlemicroprocessor can efficiently measure and control the parameters ofsynchronization. This project will be able to measureand compare the voltage and frequency between an alternator and the busbar andable to make necessary changes in the frequency and voltage if any required.When these two limits become satisfied Instant Inphase Detector will find thecorrect instant to shut down the circuit breaker. CHAPTER 2LITERATURE REVIEW 2.1 Synchronization In dictionary synchronization is the operation or activity of two ormore things at the same time or rate.
In simple words, it is a process ofelectrically connecting and matching one alternator with another or to thebusbar. If we talk in a precisemanner then it is an act of matching two different alternator’s phase, voltagesand frequencies.Illustrating the words mathematically, voltages provided by the alternatoris in the formAnd the voltage from the busbar that we are obtaining areFor synchronization, the voltages of alternator and bus barmust be equal that is=That implies =So all these parameters should be matched. 2.
2 Synchronizing methods We can categorize it into two methods which aremanual synchronization and automatic synchronization. Manual synchronizationIn manual synchronization, the operator has a full control overgenerator speed, and after meeting the synchronization conditions, he isresponsible to operate the breaker closure command. Manual synchronizing iscompletely performed by the operator. This type of synchronizing method isquite simple. The maindisadvantage of this method is that it requires well trained operators at thecontrols to prevent sever damage to system due to improper synchronization. Manual synchronization can beperformed by the two different ways1. Synchronizing lamps2. SynchroscopeSynchronizing lamps This is the oldest methodused to synchronize the alternator with another alternator or to busbar.
This method uses three lamps connected across like phases of the openbreaker, and two voltmeters one to measure the first alternator voltage, andthe other one is used to measure second alternator or busbar voltage to satisfythe first condition of paralleling. Other conditions canbe satisfied using lamps, As the generator speed changes, the lights willflicker at the frequency proportional to the difference between alternator frequency andbusbar frequency. The lamp would be at maximum brilliance when the alternatoris completely out of phase and completely extinguished when the two voltageswere in phase with identical magnitudes. The procedure steps to follow for thesynchronization in this method are given belowStep1:The prime mover of the incoming machine starts, and the generator isbrought up to near its rated speed. Step2:By adjusting the field current, the terminal voltage of the alternatoris made the same as that of the busbar. The lamp in the circuit will nowflicker at a rate equal to the difference in frequency of the alternator andbusbar.
Correct connection of the phases result on synchronous brightening andblacking of the lamps. If this is not the case, then it means two of the linesare connected wrongly and they need to be interchanged. Step3:Further adjustment of the incoming prime mover is now necessary, until thelamps flicker at a very low rate, the lamps pulsed as the alternator voltagerotated with respect to the system voltage at slip frequency.
Step4:After taking final adjustments, the operator would initiate a breakerclose when the lamps were dark, indicating matching voltages and phase arematched together and ready to synchronize. SynchroscopeSynchroscope is a device that indicates the degree to which twosystems are synchronized with each other. It plays a vital role in ensuringthat the two power supplies which are being synchronized are “inphase” with each other. The Synchroscope has a dial witha pointer which can occupy different positions according to the difference inthe phase angle. The positions are usually compared with themarkings on the clock. 3 ‘O’clock position indicate that the voltages are apart by an angle of30 degrees.6 ‘O’clock position indicate that the voltages are apart by an angle of180 degrees.When the pointer is at the 12’O’clock position, it indicates that thedifference in phase angle between the two sources is zero.
The breakerconnecting the two sources can now be closed. Working Principle The synchroscopeconsists of a small motor with coils on the two poles connected across twophases i.e incoming alternator and bus bar. The bus bar circuit consists of aninductance and resistance connected in parallel. The inductor circuit has thedelaying current effect by 90 degrees relative to current in resistance.
These dual currentsare fed into the synchroscope to the armature windings which produces arotating magnetic field. The polarity of the poles will change alternatively innorth/south direction with changes in red and yellow phases of the incomingmachine. The rotating field will react with the poles by turning the rotoreither in clockwise or anticlockwise direction. If the rotor is movingin clockwise direction this means that the incoming machine is running fasterthan the bus bar and slower when running in anticlockwise direction. Generally,it is preferred to adjust the alternator speed slightly higher, which will movethe pointer on synchroscope is in clockwise direction. The breaker is closedjust before the pointer reaches 12 o clock position, at which the incomingmachine is in phase with the bus bar. Sometimes as aprecaution against out-of-step connection of a machine to a system, a “synchrocheck” relay is installed that prevents closing the generator circuit breaker unless the machine is within a fewelectrical degrees of being in-phase with the system.
The manual system uses two types of sync-check relay:a) electromechanical sync-check relaysb) solid-state sync-check relay Automatic synchronizationDesign of an automatic synchronizing device mainly adopt several kindsof controllers and these are listed below 1) PLC2) DSP 3) Microcontroller4) Microprocessor Using sensors and PLCin the control unit increases the cost of the system. But it is most effectiveway to do the synchronization. Using DSP can realizethe high arithmetic rate, but the cost is expensive, and the developing periodis long. An automaticsynchronizer based on dual principles and dual microcontroller is developed.Both modules monitor the parameters of alternators, and switch is connectedwhen all parameters are synchronized. Using Microprocessor,we can easily control the voltage, frequency and phase by using some axillarydevices just like Frequency Controlling Unit Voltage Controlling Unit Circuit Breaker with Switching Circuit Signal Conditioning Unit Display unit In order to improve the celerity, veracity and security of thealternator synchronizing operation, an alternator synchronizing device based on8085 microprocessors, is developed.This device is simple in structure and cheap. Only one microprocess isrequired to do the required task.
AlternatorAn alternator is a machine designed to generate alternating current (AC). Specificallyit convers mechanical energy to electrical energy. This machine is the majorelectrical unit in power plants.Thealternator converts the mechanical energy of a prime mover such as a diesel engine, steam turbine, or waterturbine into electrical energy.Working Principle