Implementation of New Scheme on Indian Power System for Distance Relay Operation in Zone 3 to Avoid Power System Blackout

Table of contents

Abstract

List of tables

List of figures

Chapter. 1 Introduction of Indian Power System Blackout
1.1 Research background and significance
1.2 Approximate Model of Indian Grid
1.3 Power Flow during Grid Disturbance
1.4 Analysis of the Grid Disturbance and Blackout
1.4.1 Depletion of Power Transmission Network
1.4.2 Frequency Control of System
1.4.3 Load Management on Gwalior-Bina Line
1.4.4 Flaws in Protection Schemes specifically zone 3
1.5 Main Work of This Paper

Chapter. 2 Study of System under Different Cases and Solutions
2.1 Introduction
2.2 General Situation of Indian Power System
2.3 Improvement in System Frequency and Rotor Angle Change because of Thermal Generation in Northern Grid
2.3.1 Improvement in System Frequency
2.3.2 Change in Rotor Angle
2.4 Improvement in system frequency and Rotor Angle Change because of Wind Generation in Western Grid
2.4.1 Improvement in System Frequency
2.4.2 Change in Rotor Angle
2.5 Tripping of Gwalior-Bina Line and System Blackout
2.6 Conclusion

Chapter. 3 Zone Three Protection
3.1 Introduction
3.2 Distance Relay Settings of Northern Region and Western Region Line
3.3 Power Swing Detection Algorithm
3.3.1 System Operation under Normal Conditions
3.3.2 System Operation under Power Swing
3.3.3 Simulation Results
3.4 Synchronous Fault Detection Algorithm
3.4.1 System Operation under Synchronous Fault Conditions
3.4.2 Simulation Results
3.5 Asynchronous Fault Detection Algorithm
3.5.1 System Operation under Asynchronous Fault Conditions
3.5.2 Simulation Results
3.6 Conclusion

Chapter. 4 Advance Scheme to Avoid Blackout
4.1 Introduction
4.2 Power Swing Detection Algorithm
4.2.1 Principle of Algorithm
4.2.2 Simulation Results
4.2.3 Phase Voltage at the Beginning of Line
4.3 Three Phase Fault Detection Algorithm
4.3.1 Principle of Algorithm
4.3.2 Simulation Results
4.4 Unbalanced Fault Detection Algorithm
4.4.1 Principle of Algorithm
4.4.2 Simulation Results
4.5 Conclusion

Chapter. 5 Summary and Prospect
5.1 Summary
5.2 Prospect

References

Acknowledgment

Abstract

In July 2012 there was blackout in India. As the result of this disturbance there were two blackouts. In first blackout only the Northern Grid was affected but in the second blackout Northern, Eastern and North-Eastern grid collapsed. A committee formed by the government analyzed the events that resulted in the collapse of system and pointed out no of factors that lead to disturbance.

Whole grid collapsed under load encroachment condition. In this thesis different factors have been analyzed using PSCAD simulation and solutions have been proposed.

Approximate model of Indian power system has been developed in PSCAD using approximate parameters given in Grid Failure Report issued by the Indian government. Increase in installed capacity of power system and its impact on system frequency and rotor angle has been studied.

A new algorithm has been proposed for distance relay operation in Zone 3 to avoid power system blackout using Indian grid model. One of the main factors that lead to the collapse of whole system was the operation of zone 3 distance relay on 400kV Bina-Gwalior Line. This scheme will improve system stability under heavy load conditions. A simplified model in PSCAD was established in order to study the zone 3 protection of distance relay.

Keywords: Distance Relay, Zone 3, System Frequency, Power Swing, Load Encroachment.

List of tables

Table 1-1: Installed Generation Capacity

Table 1-2: Line parameters of Bina-Gwalior Line

Table 1-3: Power Imported by Northern Grid

Table 2-1 Installed capacity of Northern, Eastern and Western Regions

Table 2-2 Pre-disturbance conditions of northern, eastern and western regions

Table 2-3: Maximum and Minimum value of rotor angle in Northern region when thermal power is changing.

List of figures

Figure 1-1 Approximated model of Indian Grid

Figure 2-1 Northern Region frequency fluctuation at 100% thermal generation capacity

Figure 2-2 Northern region frequency fluctuation at 115% thermal generation capacity

Figure 2-3 Northern Region frequency fluctuation at 130% thermal generation capacity

Figure 2-4 Northern Region frequency fluctuation at 140% thermal generation capacity

Figure 2-5 Northern Region frequency fluctuation at 150% thermal generation capacity

Figure 2-6 Rotor angle at 100% thermal capacity is 53.52 degrees

Figure 2-7 Rotor angle at 115% thermal capacity is 48.65 degrees

Figure 2-8 Rotor angle at 145% thermal capacity is 45.1 degrees.

Figure 2-9 Wind power generation at 0% of thermal generation

Figure 2-10 Wind power generation at 10% of thermal generation

Figure 2-11 Wind power generation at 20% of thermal generation

Figure 2-12 Wind power generations at 30% of thermal generation

Figure 2-13 Rotor angle at 10% penetration of wind

Figure 2-14 Rotor angle at 20% penetration of wind

Figure 2-15 Rotor angle at 30% penetration of wind

Figure 2-16 Northern Region frequency when Gwalior-Bina Line Tripped

Figure 2-17 Western Region frequency when Gwalior-Bina Line Tripped

Figure 3-1 Approximate Model of Indian Grid

Figure 3-2 System operation under normal condition

Figure 3-3 System operation under power swing

Figure 3-4 Condition I for normal operation U > 0.3*

Figure 3-5 Condition II for normal operation 0.05* In > I2.

Figure 3-6 Condition III for normal operation 0.05* In > I0

Figure 3-7 Waveform of current during normal system operation

Figure 3-8 Line to line voltage waveform during normal system operation

Figure 3-9 Synchronous Fault Detection Algorithms

Figure 3-10 Condition I for synchronous fault detection U < 0.3*Vn

Figure 3-11 Condition II for synchronous fault from 1.0 - 3.0 s, Z<Z3

Figure 3-12 Current waveforms in case of synchronous fault

Figure 3-13 Line to line voltage in case of synchronous fault

Figure 3-14 Asynchronous Fault Detection Algorithms

Figure 3-15 Condition I for asynchronous fault detection t=1s to t=3s, I0 > 0.05* In

Figure 3-16 Condition I for asynchronous fault detection from t=1s to t=3s, I0 > 0.05* In

Figure 3-17 Condition II For asynchronous fault detection t=1s to t=3s, I2 > 0.05* In

Figure 3-18 Condition II for asynchronous fault detection t=0.0s to t=0.5s, I2 > 0.05* In

Figure 3-19 Condition III for asynchronous fault detection Z < Z3 from time t=1s to t=3s

Figure 3-20 Line to Line Voltage waveform from 1.0-3.0 in case of asynchronous fault

Figure 3-21 Current waveforms from 1.0-3.0 in case of asynchronous fault

Figure 4-1: Advance Power Swing Detection Algorithm

Figure 4-2: 5% of phase voltage at the beginning of line

Figure 4-3: Value of phase voltage multiplied by power factor

Figure 4-4: 5% of is greater than cos for t<0.1 sec just after power swing at 0.2s

Figure 4-5: Increase in I I0+I2 I just after the power swing from 0.1s to 0.15s

Figure 4-6: Increase in K2*I1 just after power swing from 0.1s to 0.15s

Figure 4-7: During Power Swing from 0.1s to 0.15s, K2*I1I >I I0+I2 I

Figure 4-8: Three Phase Fault Detection Algorithm

Figure 4-9: Value of cos becomes very low after fault inception at 1.0s

Figure 4-10: Value of 5%* goes down after fault inspection at 1.0s

Figure 4-11: For t>5s, 5%* >VnCos

Figure 4-12: Value of I I0+I2 I for fault from 0.2s to 1.0s

Figure 4-13: Value of K2*I1 for fault from 0.2s-1.0s

Figure 4-14: Unbalanced fault detection algorithm

Figure 4-15: Value of K1*I1 for fault from 1.0s to 3.0s

Figure 4-16: Value of I I0+I2 I for fault from 1.0 to 3.0s

Figure 4-17: Comparison of both values shows I I0+I2 I>K1*I1 for fault from 1.0s to 3.0 s

Chapter. 1 Introduction of Indian Power System Blackout

1.1 Research background and significance

India is the world’s third largest electricity producer and consumer of electricity after the China and USA, the electrical infrastructure is generally considered unreliable .The northern electrical grid had previously collapsed in 2001.An estimated 27% of energy generated is lost in transmission or stolen, while peak supply falls short of demand by an average of 9%.The nation suffers from frequent power outages that last as long as 10hours.Further,about 25% of the population, about 300 Million people, have no electricity at all. Efforts are underway to reduce transmission and distribution losses and increase production further.

In July 2012 there was great disturbance in Indian grid. It resulted in two blackouts. In first blackout 36000MW load was disturbed in Northern region while in second blackout 48000MW load was disturbed in Northern, Eastern and Western regions. It affected millions of homes and industrial as well as transportation operations were shut down. In an investigation by the committee formed by the government there were number of factors responsible for this blackout. Some important factors as listed below:

1. Peak load during hot summer days.
2. Weak infrastructure of Indian grid.
3. Low hydro power generation.
4. Tripping of Bina-Gwalior line in zone 3 protection of distance relay.

Northern Region and Western Region are connected by 2 400kV lines between Bina and Gwalior. One of the lines was down for maintenance purpose to upgrade it to 765kV line. One of the main factors that lead to the collapse of whole system was the operation of zone 3 distance relay on 400kV Bina-Gwalior Line. Bina-Gwalior Line was under heavy load and it collapsed in zone 3 without any fault. Zone 3 distance relay scheme could not distinguish between faults. Load encroachment and tripped under heavy load condition. Ideally it should not have tripped that would have avoided greater disturbance and collapse of whole system. Zone 3 should not trip unless there is a fault in the system. When Bina-Gwalior Line tripped power started flowing through eastern link which resulted in overloading in Eastern grid. It caused power swing and finally eastern link collapsed.

The Study about the Implementation of New Scheme in Indian Power System for Distance Relay Operation in Zone 3 to Avoid Power System blackout can be a stepping stone to recognize easier the conditions and factors of blackouts in India particularly in Zone3. This study is significant in analyzing the disturbances and contributing factors that allow a blackout to spread. Additionally, it helps contribute data and possible solutions to deflect mass power system blackout. It might also serve a big contribution go capture the general patterns of the propagation of cascading failures in Power System and help better understand how and why cascading failures occur and propagate. The main goal of this study is to convey key solutions to avoid Power System Blackout and this goal is attainable through different kinds of algorithms.

In this paper this situation has been analyzed and a solution has been proposed to avoid tripping of line under heavy load and power swing. Line should only trip under fault. This new scheme will enhance the stability of system under such disturbances.

1.2 Approximate Model of Indian Grid

Mainly Indian grid can be categorized in Northern, Western and Eastern regions. Northern region is connected with Western region through two 400kV links between Bina-Gwalior. One of the links was in operation during blackout while the other link was down for up gradation. Eastern region is connected to both Northern and Western region.

Northern, Eastern and Western region have hydro and thermal power generation. Installed hydro and thermal capacity is as follows:

Installed generation capacity of Northern, Eastern and Western Grids are as follows.

Table1-1: Installed Generation Capacity

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Approximate model generation capacity of every grid is represented by two generators named as hydro generation and Thermal Generation. Load, Thermal and Hydro generation all have been connected to bus representing a particular regional grid as shown in Figure 1-1.

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Figure 1-1: Approximated model of Indian Grid

Each link between different grids has its own line parameters given is table 1-1. Western Region and Northern Region length has been taken 350km for better realization of zone 3 tripping problem under load encroachment.

Table 1-2: Line parameters of Bina-Gwalior Line

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1.3 Power Flow during Grid Disturbance

Northern region has the highest load attached to it as compared to Western region and Eastern region. Installed capacity of Northern region is lesser than it demand. In this condition it imports power from Western Region and Eastern region. Following table shows the power that was being imported by Northern region at the time of grid disturbance. As seen from the above sequence, this tripping is essentially a Zone 3 tripping on load encroachment. After the tripping of 400 kV Bina-Gwalior-1, the system has collapsed within seconds and beyond the control of the operator.

Table 1-3: Power Imported by Northern Grid

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1.4 Analysis of the Grid Disturbance and Blackout

In this grid disturbance there was not a single factor responsible for blackout. There were many factors started from overloading of system, mismanagement of load and eventually collapse of whole system. In some cases the impedance measured by a distance relay at one end of the line may reduce to a point where it is less than the tripping condition for that relay for back-up protection (Zone 3). This may happen even if there is no fault in the nearby transmission system, and may occur when the line carries a very heavy load. Number of factors responsible for blackout was pointed out in report published by the government and some of the factors are as follows.

1.4.1 Depletion of Power Transmission Network

Numbers of lines were out of service between Northern region and western region because of various issues. One line between Northern region and western i.e. Gwalior- Bina line was out of service because of up gradation and some other lines were also out of service because of insulator problems. This situation made the Gwalior-Bina line network weaker.

1.4.2 Frequency Control of System

Utilities have been trying to meet more loads within the limited generation at the cost of poor frequency control. Frequency has been varying between 48 to 51.5 Hz. This is also one of the causes that compromise system stability. The Northern-Eastern and North Eastern regions after separation from the NEW grid should ideally have survived due to Under Frequency Relay and relay load-shedding. In fact the frequency stabilized at 48.12 Hz for nearly a minute before it collapsed. The UFR load shedding was not adequate to bring the frequency back to a safer level of 49.5 Hz and above. Any unit tripping at 48.12 Hz and/or onset of load could have caused the frequency to decline below 47.5 Hz where most of the generators trip out leading to a collapse. This is a matter of concern and needs to be examined separately.

1.4.3 Load Management on Gwalior-Bina Line

July is one of the hottest months in India. In this hot summer there was high demand of power for cooling systems/fans etc. that overloaded the system. System was unable to handle high demand because of inefficiencies, bad coordination between utilities, maintenance problems and relay settings etc. During high loading there was no coordinated load shedding. Load shedding was being done but system was still under high loading. Utilities did not have effective communication among each other. It has also been observed that Gwalior-Bina line was under high load and load shedding schemes were in-effective. Despite some of load shedding done by the system operators system was still under high stress.

1.4.4 Flaws in Protection Schemes specifically zone 3

Distance relay settings have also played an important role in making the situation complex. Distance relay in zone 3 tripped while the Gwalior-Bina line was not thermally overloaded loaded. In other words current ratings of the conductor were not exceeded. Relay settings could not distinguish between fault and load encroachment.

The first tripping occurred on 400kv Gwalior-Bina line. This tripping occurred on zone 3. The system was not thermally loaded and it was expected to survive but it collapsed in zone 3. Zone 3 distance relay perceived load encroachment as fault. It is noted that on both days, the grid disturbance was initiated by tripping of 400 kV Bina-Gwalior line on zone-3 of Main-II protection, though there were several other concurrent conditions, which ultimately led to collapse of grid. There is no doubt that this tripping is attributable to load encroachment i.e. the current and voltage conditions were such that the protection system perceived it as fault (during fault, current becomes very high and voltage goes down to very low levels). Thereafter, there were several tripping on load encroachment and power swing. It is also noted that on both days, only Main-II protections operated and Main-I protection did not pick up.

Distances relay settings for zone 3 needs to carefully set. It should be able to distinguish load encroachment and fault. a new protection scheme for improving the performance of the distance protective relays in transmission systems. The determination of fault zone by the proposed scheme is based on data sheared locally with other distance relays at the same station, in addition to a command from the distance relay on the other end of the protected line. In some cases the impedance measured by a distance relay at one end of the line may reduce to a point where it is less than the tripping condition for that relay for back-up protection (Zone 3). This may happen even if there is no fault in the nearby transmission system, and may occur when the line carries a very heavy load. This phenomenon of the mal-operation of the distance relays is known as ‘Load Encroachment’. Generally, it is an unintended tripping for distance relays since no fault has actually occurred. It may be noted that at the time of disturbance, the 400 kV Bina-Gwalior line experienced a lower voltage and higher load current (resulting in less impedance, seen by the relay, which, possibly, was below the zone-3 reach setting of the relay) caused the relay operation under load encroachment.

1.5 Main Work of This Paper

The main work of this paper is new algorithm has been proposed for distance relay operation in Zone 3 to avoid power system blackout using Indian grid model. The work has been studied and a solution has been proposed to avoid tripping of line under heavy load and power swing. Line should only trip under fault. This new scheme will enhance the stability of system under such disturbances. This scheme will improve system stability under heavy load conditions. A simplified model in PSCAD was established in order to study the zone 3 protection of distance relay.

Chapter. 2 Study of System under Different Cases and Solutions

2.1 Introduction

This chapter shows the study system under different cases and solutions These Includes the general situation of Indian Power system which has three parts, Installed capacity of Northern ,Eastern and Western regions, the pre Disturbance conditions of Northern ,Eastern and Western regions and the Grid frequency prior to Disturbance. One of the major focuses in chapter is the improvement and the change system and Rotor angle because of the power Generation in Northern Grid. This part has summarizes the increase of Thermal generation in different percentage. The percentage is enumerated as 100%,110%.115%,130%,!40%and 150%.the improvement in the system frequency and Rotor angle because of wind generation western grid starting from 0 to 20%.there are number of other contributing factors that allow a blackout to spread, including lack of coordinated response among control areas. Each region focus primarily on its own transmission system .Each of the individual system have boundaries, electric power and critical communication do not obey these boundaries. Intertie separation is not pre-planned for serve emergencies, leaving operate to decide very difficult during a fast developing disturbance. In order to avoid load encroachment on northern region and western region grid it has been simulated that if the generation capacity of northern region is increased it can make the system stable and frequency fluctuation in the system can be Minimum.

2.2 General Situation of Indian Power System

The utility electricity sector in India had an installed capacity of 298 GW as of 31 March 2016.Renewable Power plants constituted 28% of total installed capacity and Non-Renewable Power Plants constituted the remaining 72%. The gross electricity generated by utilities is 1,106 TWh (1,106,000 GWh) and 166 TWh by captive power plants during the 2014–2015 fiscal. The gross electricity generation includes auxiliary power consumption of power generation plants. India became the world's third largest producer of electricity in the year 2013 with 4.8% global share in electricity generation surpassing Japan and Russia. By the end of calendar year 2015, despite poor hydro electricity generation, India has become power surplus country with huge power generation capacity idling for want of electricity demand. The calendar year 2016 started with steep fall in the international price of energy commodities such as coal, diesel oil, naphtha, bunker fuel and LNG which are used in electricity generation in India.

The table 2.1 shows the installed capacity of Northern, Eastern and West Regions .The capacity include the totally of Hydro capacity, Thermal capacity and nuclear and renewable .The table shows that Northern Region acquires the highest Hydro capacity with a total of 19830MW preceded by western Region with 7448MW while the eastern Region acquires the lowest with the 3882MW the total of Hydro capacities in the North, East and west falls into 31160 MW. In terms of thermal capacity Western Region uses the highest MW of 49402 followed by the Northern with 34608 MW and the Eastern with the lowest MW of 22545.vivdly the total Thermal capacity of these three regions is 106555MW.The west gets 9750 MW for the Nuclear and renewable while the north acquires 1620 MW. The East is clearly getting at least of MW in three of the installed capacities while Western Region acquires the most MW in Hydro .Thermal Capacities and Nuclear and Renewable follower by the Northern Region.

Installed capacity of Northern, Eastern and Western Regions are as follows:

Table 2-1 Installed capacity of Northern, Eastern and Western Regions

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Pre-Disturbance Conditions of Northern, Eastern and Western Regions are shown in the table 2-2. Northern, Eastern and western and North Eastern Regions, Generation, Demand .Import (+) and export (-) and the remarks .the pre disturbance shows the total demand this four regions is 79479MW while the total MW generation is 79902 MW. Northern region imports 5686 MW while the Eastern, Western and North Eastern export. Western export the highest of 6229MW ,followed by eastern region of 239MW while the Northern Eastern Region Export the lowest of 53MW.The Eastern Region has a remark of important from Bhutan for 1127MW.

2.3 Improvement in System Frequency and Rotor Angle Change because of Thermal Generation in Northern Grid

Northern region had higher demand. Higher demand of northern region was met by importing power from southern and eastern regions. It was overloading the system. In order to avoid Load encroachment on northern region and western region grid it has been simulated that if the generation capacity of northern region is increased it can make the system stable and frequency fluctuation in the system can be minimize.

2.3.1 Improvement in System Frequency

Different cases have been studied by increasing thermal generation. For following values frequency fluctuations has been discussed.

a. when thermal power is 100%; b. when thermal power is 115%; c. when thermal power is 130%; d. when thermal power is 140%; e. when thermal power is 150%.

Following are the results:

a. Northern Region100% thermal generation capacity When the Thermal power is 100% the frequency fluctuation is Minimum and generation capacity of northern region increased.it can make system stable.

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Figure 2-1 Northern Region frequency fluctuation at 100% thermal generation capacity

Northern Region 115% thermal generation capacity

When the Thermal power is 115% the frequency fluctuation is Minimum and generation capacity of northern region increased.it can make system stable.

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Figure 2-2 Northern region frequency fluctuation at 115% thermal generation capacity

b. Northern Region 130% thermal generation capacity When the Thermal power is 130% the frequency fluctuation is Minimum and generation capacity of northern region increased.it can make system stable.

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Figure 2-3 Northern Region frequency fluctuation at 130% thermal generation capacity

c. Northern Region 140% thermal generation capacity

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Figure 2-4 Northern Region frequency fluctuation at 140% thermal generation capacity

When the Thermal power is 140% the frequency fluctuation is Minimum and generation capacity of northern region increased.it can make system stable.

d. Northern Region 150% thermal generation capacity When the Thermal power is 150% the frequency fluctuation is Minimum and generation capacity of northern region increased.it can make system stable.

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Figure 2-5 Northern Region frequency fluctuation at 150% thermal generation capacity

2.3.2 Change in Rotor Angle

It is observed that even though the frequency of the NEW grid (49.68 Hz) was near to its nominal value (50 Hz), a number of lines were not available due to either forced outages, planned outages or kept out to control high voltages. This resulted in a depleted transmission network, which, coupled with high demand in the Northern Region, resulted in an insecure state of the system operation.

a Northern region Rotor angle at 100% thermal capacity

When rotor angle is at 100% thermal capacity is 53.52 degrees.

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Figure 2-6 Rotor angle at 100% thermal capacity is 53.52 degrees

b Northern Region Rotor angle at 115% thermal capacity

When rotor angle is at 115% thermal capacity is 48.65 degrees.

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Figure 2-7 Rotor angle at 115% thermal capacity is 48.65 degrees

c Northern Region Rotor angle at 130% thermal capacity

Rotor angle at 130% thermal capacity is 45.10 degrees.

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Figure 2-8 Rotor angle at 130% thermal capacity is 45.10 degrees.

Table 2-3: Maximum and Minimum value of rotor angle in Northern region when thermal power is changing.

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In the table 2-3 shows the Thermal power of North region with three Rotor angle 100%, 115%, 130% .get the minimum and maximum values.

2.4 Improvement in system frequency and Rotor Angle Change because of Wind Generation in Western Grid

The Northern Grid is the vital power supply line to the entire North India. This part focuses on the improvement of system frequency and Rotor Angle change because of power generation in northern grid. How does the power generation change the Rotor angle? Basically when two synchronous generators running in parallel, load shading between them depends on Rotor Angle. In equilibrium, both the generators will run at equal speeds. If balance is disturbed, acceleration or deceleration will take place and lead to oscillations in Rotor angle .This may lead to instability and eventually falls out of synchronism. This part will clarify the change in the North Region Rotor Angle different percentage and the changes in Rotor angle due to the wind generation in western grid using 10 to 30 percent of wind penetration .Graphs have been provided the vividly discuss the main important points in the Changes of Rotor Angle because of the Power Generation and the changes in Rotor angle due to wind Generation in Western Grid.

2.4.1 Improvement in System Frequency

In western region wind power intake has been considered. By adding wind power generation in western grid, frequency fluctuation becomes smaller and smaller while power is being transmitted from western to northern grid. It has been considered that the wind power is reaches to 30% of thermal power of southern grid. Wind power penetration has been considered at the rate of 0%, 10%, 20% and 30% of thermal generation of western grid.

a. Wind Power generation at 0% of thermal generation

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Figure 2-9 Wind power generation at 0% of thermal generation

b. Wind power generation at 10% of thermal generation

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Figure 2-10 Wind power generation at 10% of thermal generation

The changes of Rotor Angle because of the Power Generation and the changes in Rotor angle due to wind Generation in Western Grid.

c. Wind power generation at 20% of thermal generation

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Figure 2-11 Wind power generation at 20% of thermal generation

d. Wind power generation at 30% of thermal generation

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Figure 2-12 Wind power generations at 30% of thermal generation

2.4.2 Change in Rotor Angle

With the increase in wind power penetration rotor angle difference also started decreasing. a Rotor angle at 10% penetration of wind

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Figure 2-13 Rotor angle at 10% penetration of wind

b Rotor angle at 20% penetration of wind

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Figure 2-14 Rotor angle at 20% penetration of wind

c Rotor angle at 30% penetration of wind

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Figure 2-15 Rotor angle at 30% penetration of wind

2.5 Tripping of Gwalior-Bina Line and System Blackout

System behavior i.e. System frequency has been observed when Northern Region (NR)-Western Region line tripped and power started flowing through WR, Eastern Region (ER) and NR.

Frequency of system in Northern region has been studied as shown in figure below when line trips at 1.5s. The frequency over shoots and system shuts down as shown in figure 2-16.

Similarly frequency in Western region has been analyzed and it can be seen in figure 2-17 that after the line trips frequency over shoots and black out happen.

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Figure 2-16 Northern Region frequency when Gwalior-Bina Line Tripped

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Figure 2-17 Western Region frequency when Gwalior-Bina Line Tripped

In this situation when the frequency is changing at a very high rate relays could have been effectively used and after separation load shedding could have been done in northern region and blackout could have been avoided.

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