As the length of the line increases specially in excess high electromotive force ( EHV ) lines, beyond 200km, we observe a phenomenon called Ferranti Effect in no burden or low burden conditions. This is due to the fact that as the line length increases the electrical capacity of the line additions, and the shunt electrical capacity generates the reactive power in the line. Since there is no burden or low burden to devour that inordinate power, this consequences in inordinate reactive power in the line and hence the having terminal electromotive force gets higher than the sending terminal electromotive force. This rise in electromotive force may good travel beyond the operative evaluations of the terminus and hence might give rise to many cascading events damaging the equipments.
The uninterrupted addition of the electromotive force of transmittal, line length and figure of sub-conductors per package has emphasized the importance of the inordinate line MVAR in EHV systems every bit good as associated electromotive force and reactive controls. During the line bear downing vars of the line which have exceeded the inductive VARs consumed and operation at light tonss, there is an unwanted electromotive force rises along the line. This electromotive force rise in bend demands a much higher insularity degree, which poses a great job. Furthermore, if the insularity against these over-voltages were to be provided in the system, so the cost of the line becomes tremendous.
To get the better of this phenomenon, shunt reactors are required to be installed at optimized location to absorb the inordinate reactive power. Though this solution has a fiscal cost, but this is inevitable, since the burden is a random variable and the coevals of the power can non be precisely planned for sudden stumbling off of the tonss.
Purposes and aims:
The purpose of this thesis undertaking is to look into the Ferranti consequence for long length transmittal lines utilizing PowerWorld simulations on a radial system. The following are the cardinal aims covered in this undertaking.
Impact by changing Line lengths:
Investigate the system behavior sing Ferranti consequence with different transmittal line lengths. This was done by look intoing the profile of the consequence for long length lines and therefore distributed theoretical accounts were considered for this analysis.
2-Impact by changing burden degrees:
Since Ferranti consequence is the phenomenon where having terminal electromotive force ( Loads ) is lower than directing terminal, it was of import to look into the lading factor by changing the burden degrees for different line lengths.
3- Investigation for optimal burden degrees to avoid consequence:
A series of experiments were done to happen the minimal values of burden required for varied line lengths in order to avoid Ferranti Effect and to incorporate the terminal electromotive force near 1p.u.
4- Minimum evaluations for reactors for compensation:
With a varied figure of simulations and experiments, the minimal evaluations of required reactors have been realized in order to keep optimized terminal evaluations at having terminal.
Scope of thesis:
This thesis will get down with an overview of the jobs encountered with EHV long transmittal line. This would be followed up by a literature reappraisal that covers the research of utile background theories. The consequence from the performed simulations will be discussed in item. Finally, some recommendation for future plants in this country of research.
The electric lines which are used to transport electric moving ridges are called transmittal lines. The transmittal line parametric quantities like induction and electrical capacity are non dissociable unlike the lumped circuits. The transmittal parametric quantities are distributed all along the length of the transmittal line. Hence the method of analysing the transmittal lines is different from analysing the lumped circuits. In the analysis of the transmittal line, merely steady province currents and electromotive forces are concerned. The analysis includes the measuring of current and electromotive forces at any length of the line, when a known electromotive force is applied at one terminal of the transmittal line. The terminal at which the electromotive forces are applied is called directing terminal and the terminal at which the signals are received is called having terminal of the transmittal line.
For the analysis and design of transmittal lines, it is of import to hold cognition of electric circuit parametric quantities, associated with the transmittal lines. Assorted electric parametric quantities associated with the transmittal lines are as below,
1-Resistance: Depending upon the cross sectional country of the music directors, the transmittal lines has opposition associated with them. The opposition is uniformly distributed all along the transmittal line. Its entire value depends upon the entire length of the transmittal line. Hence its value is given per unit length of the transmittal line. It is denoted as R and is given in ohms per unit length.
2- Induction: When the music directors carry the current, the magnetic flux is produced around the music directors. It depends upon the magnitude of the current flowing throw the music directors. The flux linkages per ampere of the current, gives rise to the consequence called induction of the transmittal line. It is besides distributed wholly along the length of the transmittal line. It is denoted as L and measured in Henry per unit length of the transmittal line.
3- Capacitance: The transmittal lines consist of two parallel music directors or individual line w.r.t Earth separated by insulator like air. Such music directors separated by an insulating dielectric produce a capacitive consequence. Due to this, there exists a electrical capacity associated with the transmittal line which is besides distributed wholly along the length of the music director. It is denoted as C and measured in Farads per unit length of the transmittal line.
4- Conductance: The insulator between the music directors is non perfect. Hence a really little sum of current flows through the insulator called displacement current. This is nil but escape current and this gives rise to the escape conductance associated with the transmittal line. It exists between the music directors and is distributed wholly along the transmittal line. It is denoted as G and measured as siemenss per unit length of the line.
Therefore the four of import parametric quantities of the transmittal line are R, L, C and G. as the current flows from one music director and finish the way through other music director, the opposition of both the wires is included when stipulating the opposition per unit length of the line. These line parametric quantities are changeless and are called the primary invariables of the transmittal line.
Revisit catchs ( 4-16 ( 1 ) )
We can analyse the public presentation of the line on per stage footing. The relationship between current and electromotive force along the one stage of the line in footings of distributed parametric quantities can be seen in the FIG below
= series electric resistance per unit length/phase.
= shunt entree per unit length/phase.
= length of the line.
The electromotive forces and current in the figure are the phasors stand foring sinusoidal clip changing measures.
For a differential subdivision of the line of length at a distance from having terminal, the differential electromotive force can be given as
hence ( 2.1 )
The differential current fluxing through shunt entree can be given as
Similarly ( 2.2 )
Distinguishing eq 1 and 2 yeilds
( 2.3 )
and ( 2.4 )
Now for the general equation for electromotive force and current at distance ten from having terminal, if the having terminal electromotive force and current are known, can be given as
( 2.5 )
( 2.6 )
Whereas this is called characteristic electric resistance.
and = = this is called extension invariable.
The changeless and are complex measures. The existent portion of extension invariable ( ) is called the fading invariable, while the fanciful portion is called the stage invariable.
Now the first term in eq.5 addition in magnitude and progresss in stage as the distance additions. This term is called incident electromotive force. While the 2nd term in eq.5 lessenings in magnitude and distorts in stage from having terminal towards directing terminal, this term is called reflected electromotive force. At any point along the line the electromotive force is the amount of incident and reflected electromotive force. The same is true for eq.6.
If a line is terminated at its characteristic electric resistance, so there is no reflected electromotive force and the line is called a level line or infinite line.
For a typical power line, G is practically zero and R & lt ; & lt ; , hence
Zc = = ( 2.7 )
= = ( 2.8 )
If losingss are wholly neglected the is a existent figure and is an fanciful figure.
Similarly for a lossless line eq.5 and 6 can be simplified as
( 2.9 )
( 2.10 )
The electromotive force and current vary harmonically along the line length. A full rhythm of electromotive force and current along the line length corresponds to 2 radians. If is the stage displacement in radians per metre, the wavelength in metres is
( 2.11 )
A line with length more than 160km is considered a long transmittal line and the parametric quantities are assumed to be distributed uniformly along the line as a consequence of which the currents and electromotive forces would change from point to indicate. Let us see the figure below
series electric resistance per unit length
shunt entree per unit length
length of the line
entire series electric resistance
entire shunt entree
The elemental equivalent of the above figure can be redrawn as follows.
For analysis intent we take having terminal as mention for mensurating the distance. Assume we have an elemental length at the distance of ten from the having terminal. If the electromotive force and current at distance ten are and, so at the distance of so the electromotive force and current becomes + and + severally.
By pull stringsing above equations
With above can be written as
By distinguishing combining weight 2.14
The solution of eq 2.16 is
From eq 2.14 and 2.16
Where is the characteristic electric resistance and is the extension invariable.
Eq 2.17 and 2.18 can be written as
If receiving terminal electromotive force and current are known so
Substituting above values in eq 8 and 9
Again replacing values of A and B in combining weight 2.19 and 2.20
Since and are the electromotive force and current at any point distance x from having terminal as apparent from look and ( magnitude and stage ) are maps of distance, having terminal electromotive force and having terminal current, which means that they vary as we move from having terminal towards directing terminal.
Now the measures and are complex
For a lossless line ;
When covering with high frequences or rushs usually the losingss are neglected and the characteristic electric resistance becomes surge electric resistance. Due to big electrical capacity and lower induction in the overseas telegrams the rush electric resistance values can be really low.
For = = the existent portion of extension invariable ( ) is called the fading invariable, while the fanciful portion is called the stage invariable.
Eq 2.11 can be written as
The first term in the above look is called incident electromotive force moving ridge and its value increases as ten is increased. Since having terminal is our reference terminal and as ten increases the value of electromotive force additions intending the magnitude of electromotive force lessenings as it travel towards the having terminal. That ‘s why the first portion of look is called incident electromotive force and the second is called reflected electromotive force for the similar ground. Lapp can be said about the current look every bit good.
Voltage and current looks can be rearranged as below
And for current
The above derived measures are related by the general equations
Where are such that
Compairing the coefficients of above look with eq 2.28 and 2.29
From this it is clear that
Sing the same two terminal status with sending and having terminal electromotive force and current, the web can be represented as figure below.
From the above web we can deduce the undermentioned looks
By comparing eq 2.30 and 2.31 with eq 2.26 and 2.27
From eq 2.33 we can deduce
We can reason from this that to acquire the series electric resistance should be multiplied with. Now to acquire the shunt arm of tantamount circuit we substitute in combining weight 2.32
Here is the entire shunt entree. So to acquire the entire shunt arm of the tantamount Thursday eshunt arm of the nominal should be multiplied with, so the tantamount circuit can be drawn as below.
2.3.2 Equivalent representation of long line:
A similar derivation of tantamount circuit can be, the tantamount circuit can be represented as Figure below.
By analysing the circuit following look can be extracted
Comparing combining weight 2.36, 2.37 with 2.26, 2.27.
Now utilizing eq 2.40 for shunt subdivision of tantamount circuit we get,
Therefore its evident that to acquire the shunt subdivision of tantamount circuit, we have to multiply with the shunt subdivision of nominal circuit.
For series electric resistance eq 2.40 is substituted in combining weight 2.38, which gives
So here we get the factor for generation with nominal circuit to acquire tantamount circuit electric resistance. And the attendant circuit can be drawn as figure below.
Bulk transmittal of electrical power by Ac in possible merely if the following two cardinal demands are satisfied.
Major synchronal machines must stay stable in synchrony:
The major synchronal machines in a transmittal system are the generators which are incapable of runing usefully other than in synchrony with all the others. And this besides is the fundamental of stableness.
Voltages must be kept near to their rated values:
The 2nd chief demand in ac transmittal is the care of right electromotive force degrees. Power systems are non inherently tolerant of unnatural electromotive forces even for short periods.
Undervoltage: this is by and large associated with heavy lading and/or deficit of coevals, causes debasement in the public presentation of tonss. In heavy laden systems, undervoltage may be an indicant that the burden is nearing the steady province stableness bound. Sudden undervoltages can ensue from the connexion of really big tonss.
Over electromotive forces: this is a unsafe status because of the hazard of flashover or the dislocation of insularity. Over electromotive forces arise from several causes. The decrease of burden during certain parts of the day-to-day burden rhythm causes a gradual electromotive force rise. Uncontrolled, this overvoltage would shorten the utile life of insularity even if the breakdown degree were non reached. Sudden overvoltage can ensue from the disjunction of tonss or other equipment, while overvoltages of extreme quickly and badness can be caused by the line exchanging operation, mistakes and lightning. In the long transmittal line this would restrict the power transportation and the transmittal distance if no compensating steps were taken.
Chapter 3 compensated/uncompensated lines
Despite being able to avoid wire opposition through the usage of superconductors in this “ thought experiment, ” we can non extinguish electrical capacity along the wires ‘ lengths.A AnyA brace of music directors separated by an insulating medium creates electrical capacity between those music directors: ( FigureA )
Voltage applied between two music directors creates an electric field between those music directors. Energy is stored in this electric field, and this storage of energy consequences in an resistance to alter in electromotive force. The reaction of a electrical capacity against alterations in electromotive force is described by the equation I = C ( de/dt ) , which tells us that current will be drawn relative to the electromotive force ‘s rate of alteration over clip. Therefore, when the switch is closed, the electrical capacity between music directors will respond against the sudden electromotive force addition by bear downing up and pulling current from the beginning. Harmonizing to the equation, an instant rise in applied electromotive force ( as produced by perfect switch closing ) gives rise to an infinite charging current.
However, the current drawn by a brace of parallel wires will non be infinite, because there exists series electric resistance along the wires due to inductance. ( FigureA below ) Remember that current throughA anyA music director develops a magnetic field of relative magnitude.A Energy is stored in this magnetic field, ( FigureA below ) and this storage of energy consequences in an resistance to alter in current. Each wire develops a magnetic field as it carries bear downing current for the electrical capacity between the wires, and in so making beads electromotive force harmonizing to the induction equation vitamin E = L ( di/dt ) . This electromotive force bead limits the electromotive force rate-of-change across the distributed electrical capacity, forestalling the current from of all time making an infinite magnitude:
Equivalent circuit demoing isolated electrical capacity and induction.
The consequence of electrical capacity of an overhead transmittal line above 160km long is taken into consideration for all computations. The consequence of the line electrical capacity is to bring forth a current called charging current. This current will be in quadrate of the applied electromotive force. It flows through the line even if the having terminal is open-circuited. The bear downing current of the unfastened circuit line is referred to as the sum of current fluxing into the line from directing terminal to having terminal where there is no burden. In many instances, the entire bear downing current of the line is determined by multiplying the entire entree of the line by the having terminal of the electromotive force. This would be right if the full length of line has the same electromotive force as that of having terminal electromotive force. However this method of happening the bear downing current is sufficiently accurate for most lines.
The existent value of the bear downing current will diminish uniformly from its maximal value at directing terminal to the minimal value at having terminal. Due to the bear downing current, there will be power loss in the line even the line is unfastened circuited.
As power flows along a transmittal line, there is an electrical stage displacement, which
additions with distance and with power flow. As this stage displacement additions, the system in which the line is embedded can go progressively unstable during electrical perturbations. Typically, for really long lines, the power flow must be limited to what is normally called the Surge Impedance Loading ( SIL ) of the line. ( dr ) or SIL is defined as the sum of power delivered by a lossless transmittal line when terminated by a burden opposition equal to “ billow ” or “ features ” electric resistance.
Rush Impedance Loading is equal to the merchandise of the terminal coach electromotive forces divided by the characteristic electric resistance of the line. Since the characteristic electric resistance of assorted HV and EHV lines is non dissimilar, the SIL depends about on the square of system electromotive force.
A transmittal line loaded to its rush electric resistance burden:
( I ) Has no net reactive power flow into or out of the line, and
( two ) Will have about a level electromotive force profile along its length.
( dr ) with burden at the having terminal equal to SIL.
Volts ( 3.1 )
It is clear from the equation that electromotive force magnitude at any point along the transmittal line is changeless with the magnitude equal to the having terminal electromotive force.
Besides, at SIL the general look for current can be rewritten as.
Amperes ( 3.2 )
Using ( 3.1 ) and ( 3.2 ) , the complex power fluxing at any point along the transmittal line can be calculated as.
( 3.3 )
Hence, the sum of existent power fluxing along a lossless transmittal line loaded at SIL is changeless as expected. Besides, noticed that the reactive power fluxing in the line is zero. This point is important in understanding the phenomenon called Ferranti consequence. When the line is terminated at SIL the net reactive power needed to present the existent power by maintaining the electromotive force invariable is zero. In other words, the reactive power internally produced by shunt electrical capacity is merely sufficient to carry through reactive power required. However, when the burden conditions change from SIL or chair burden to light burden to heavy burden, there will be instability in reactive power required to convey the existent power. In the absence of devices to command and counterbalance for reactive power, state of affairs could ensue in deficiency or excess of reactive power. Hence, make a low or high electromotive force profile, severally in the receiving terminal of the transmittal line.
Typically, stableness bounds may find the maximal allowable power flow on lines that are more than 160 kilometers in length. For really long lines, the power flow restriction may be less than the SIL as shown in Table 0-1. Stability limits on power flow can be every bit low as 20 % of the line thermic bound.
Typical stableness bounds as a map of system electromotive force are given in table below:
The lossless line that is energized by the generators at the directing terminal and is unfastened circuited at the having terminal is described by following equation with.
Voltage and current at the directing terminal can be given as
and are in stage, which is in consistent, with the fact that there is no power transportation. The phasor diagram shown in the figure.
The electromotive force and current profiles in equation 1 and 2 are more handily expressed in footings of.
Phasor diagram of unsalaried line on open-circuit
Voltage and current profile at no burden status.
The general signifier of these profiles shown in fig 3.5 above. For a line 300km in the length at 50Hz, 3600 60 per 100km, so ????=6*3=180. Then and based on the SIL. The electromotive force rise on unfastened circuit is called Ferranti Effect.
Although the electromotive force rise of 5 % seems little, the ‘charging ‘ current is appreciable and in such a line it must wholly be supplied by the generator, which is forced to run at taking power factor, for which it must be underexcited. The reactive power soaking up capableness of a synchronal machine is limited for two chief grounds
The warming of the terminals of the stator nucleus additions during the under aroused operation.
The decreased field currents consequences in decreased internal voltage of the machine and this weakens the stableness.
Note that a line for which ????=??›???›?=???‹/2 has a length of I»/4 ( one one-fourth length wavelength, i.e, 1500km at 50Hz ) bring forthing an infinite electromotive force rise. Operation of any line nearing this length is wholly impractical without some agencies of compensation.
In instance of the sudden open-circuit of the line at the having terminal, the directing terminal electromotive force tends to lift instantly to open-circuit electromotive force of the directing terminal generators, which exceeds the terminal electromotive force by about the electromotive force bead due to the anterior current fluxing in their short circuit reactances.
Reactive power compensation means the application of reactive devices
To bring forth a well level electromotive force profile at all degrees of power transmittal.
To better stableness by increasing the upper limit catching power, and/or
To provide the reactive power demands in the most economical manner.
Ideally the compensation would modify the rush electric resistance by modifying the capacitive and/or inductive reactances of the line, so as to bring forth a practical rush electric resistance burden that was ever equal to the existent power being transmitted. Yet this is non sufficient to guarantee the stableness of the transmittal, which depends besides on the electrical line length. The electrical length can itself be modified by the compensation to hold a practical ????’shorter than the unsalaried value, ensuing in an addition in the steady province stableness bound
This consideration suggests two wide categorization strategy, Surge electric resistance compensation and line length compensation. Line length compensation in peculiar is associated with series capacitances used in long distance transmittal. Another compensation is called compensation by segmenting, which is achieved by linking changeless electromotive force compensators at intervals along the line. The maximal catching power is that of the weakest subdivision but since this is needfully shorter than the whole line, an addition in maximal power and, hence, in stableness can expected.
Passive compensators include shunt reactors and capacitances and series capacitances. They modify the induction and electrical capacity of the line. Apart from the shift, they are uncontrolled and incapable of uninterrupted fluctuation. For illustration, shunt reactors are used to counterbalance the line electrical capacity to restrict electromotive force rise at the light burden or no load status. They increase the practical rush electric resistance and cut down the practical natural burden Shunt capacitance may be used to augment the electrical capacity of the line under heavy burden. They generate reactive power which tend to hike the electromotive force. They cut down the practical rush electric resistance and addition. Series capacitances are used for line length compensation. A step of rush electric resistance compensation may be necessary in concurrence with series capacitances, and this may be provided by shunt reactors or by a dynamic compensator.
Active compensators are normally shunt affiliated devices which have the belongings of be givening to keep a well changeless electromotive force at their terminuss. They do this by bring forthing or absorbing exactly the needed sum of disciplinary reactive power in response to any little fluctuation of electromotive force at their point of connexion. They are normally capable of uninterrupted fluctuation and rapid response.
Active compensators may be applied either for rush electric resistance compensation or for compensation by segmenting. In compensation they are capable of all the maps performed by fixed shunt reactors and capacitances and have extra advantages of uninterrupted variableness with rapid response. Compensation by segmenting is basically different in that it is possible merely with active compensators, which must be capable of virtually immediate response to the smallest fluctuation in power transmittal or electromotive force. The tabular array below summarizes the categorization of the chief type of compensators harmonizing to their usual maps.
Shunt reactors are used to restrict the electromotive force rise at the light burden or no load conditions. On long transmittal they may be distributed at intermediate substations in shown in figure below
electromotive force and current profile of shunt compensated system at no burden.
See the simple circuit above in figure, it has a individual shunt reactor of reactance at the having terminal and a pure electromotive force beginning at the directing terminal. The having terminal electromotive force can be given as
Equation 7 shows that and are in stage, in maintaining with the fact that the existent power is zero. For having terminal electromotive force to be equal to directing end electromotive force, must be given by
The sending terminal current can be given as
utilizing equation 3.9 and 3.11
Since, this means that the generator at the directing terminal behaves precisely like the shunt reactor at the having terminal in that both absorb the same sum of reactive which is apparent from equation below.
A long transmittal line draws a significant measure of bear downing current. If such a line is unfastened circuited or really lightly loaded at the having terminal, the electromotive force at having terminal may go greater than electromotive force at directing terminal. This is known as Ferranti Effect and is due to the electromotive force bead across the line induction ( due to bear downing current ) being in stage with the directing terminal electromotive forces. Therefore both electrical capacity and induction is responsible to bring forth this phenomenon.
Another manner of explicating Ferranti consequence is based on net reactive power flow in the line. It is known that if the net reactive power generated in prevarication is more than the reactive power absorbed, the electromotive force at that point in the line becomes higher than the normal value and frailty versa. The inductive reactance behaves like a sink in the line whereas the shunt electrical capacity generates the reactive power. If the line lading corresponds to the rush electric resistance burden, the electromotive force is same everyplace as reactive power absorbed in the line is equal to the reactive power generated. If the burden is less than SIL, generated power is more than generated power absorbed, hence, the having terminal electromotive force is higher than directing end electromotive force.
The electrical capacity ( and bear downing current ) is negligible in short line but important in medium line and appreciable in long line. Therefore this phenomenon occurs in medium and long lines.
Represent line by tantamount theoretical account.
And the vector diagram can be given as
OM = having terminal electromotive force Vr
OC = Current drawn by electrical capacity = Ic
MN = Resistance bead
NP = Inductive reactance bead
OP = Sending terminal electromotive force at no burden and is less than having end electromotive force ( Vr )
Since, opposition is little compared to reactance ; opposition can be neglected in ciphering Ferranti consequence.
From theoretical account,
For unfastened circuit, no burden,
By pretermiting opposition
The measure is changeless in all line and is equal to speed of extension of electromagnetic moving ridges ( = 3 A- 102 km/sec )
By replacing the values in the above derived equation
From the above equation
Receiving terminal electromotive force is greater than directing end electromotive force and this consequence is called Ferranti Effect.
5.1, fig 4.10,4.6,4.4,4.2,4.1,3.5,3.4,2.1
Chapter 5 consequences and treatment
Consequences and treatments:
To imitate for my analysis, a radial system in the undermentioned figure was modeled as trial system. Practical industrial information was acquired from Queensland Electric Commission which follows the Australian criterion for music directors and enforces the transmittal and distribution company to follow the criterions. This acquisition was of import to integrate for more realistic analysis and detect the phenomenon as it is appeared in the existent life transmittal systems.
Conductor types for the simulation were chosen from the provided list of music directors based on conduction, opposition and reactance of a peculiar type. Following tabular array has the types of music directors which were chosen for simulation.
Experiments for no burden:
The aim of these experiments was to detect the having end terminal electromotive force with no burden while changing the length of transmittal line.
In this simulation the length of the line was varied from 100km to 1000km with nominal electromotive force of 138kv. trials were performed on each of the music directors mentioned in the tabular array above.
As shown in the figure below, the terminal electromotive force at having terminal corsets within acceptable scope up-till the length of 200km. It is apparent that as the length increases beyond 300km length, the having terminal electromotive force steps out of the acceptable scope. The terminal electromotive force reaches over its operating scope at 300km and maintain on traveling higher as the length additions.
We can detect the Ferranti Effect and this is consistent with the theoretical reappraisal in above chapters which stated that, if the coevals of reactive power is more than the soaking up the terminal electromotive force will raise, and since the electrical capacity in the line addition with the addition of length doing inordinate reactive power in the line which consequences in the high having terminal electromotive force.
Experiments for low burden:
The aim of these experiments was to detect the having end terminal electromotive force with a fix burden while changing the length of transmittal line. A burden 20MW, 5MVAR was attached at having terminal to contemplate for low burden with nominal electromotive force as 138kv.
In this simulation the length of the line was varied from 100km to 1000km. trials were performed on each of the music directors mentioned in the tabular array above.
As shown in the figure below, the terminal electromotive force at having terminal corsets within acceptable scope up-till the length of 300km. It is apparent that as the length increases beyond 300km length, the having terminal electromotive force steps out of the acceptable scope. The terminal electromotive force reaches over its operating scope at 400km and maintain on traveling higher as the length additions.
Even with a burden of above mentioned evaluations we still observe the Ferranti Effect and this is consistent with the theoretical reappraisal in above chapters which stated that, if the coevals of reactive power is more than the soaking up the terminal electromotive force will raise, and since the electrical capacity in the line addition with the addition of length doing inordinate reactive power in the line which consequences in the high having terminal electromotive force.
Experiment for optimal reactors:
The intent of this experiment was to calculate out the optimal evaluations for reactors required to be installed at having terminal in order to accomplish acceptable terminal electromotive force. It is of import to see that the reactors should be optimized for worst instance, which is no load status, when the terminal electromotive force is maximal.
Figure below gives an thought of optimal capacity of reactors ( MVAR ) required to absorb the inordinate power in the transmittal line with regard to length.
Experiment for minimal burden required:
A figure of experiments were done in order to happen the minimal sum of burden with regard to length in order to accomplish the 1p.u. The figure below summarizes the demands of burden ( MW ) . As the length increases the minimal burden demand increases significantly. In most instances this unrealistic to accomplish at all times to avoid the demand to put in the reactors.