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Expansion of Power System Corridors Using Tier-1 Technique for Reactive Power Compensation | OMICS International
ISSN: 2332-0796
Journal of Electrical & Electronic Systems
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Expansion of Power System Corridors Using Tier-1 Technique for Reactive Power Compensation

Ezennaya SO1*, Ezechukwu OA1, Anierobi CC1 and Akpe VA2

1Department of Electrical Engineering, Nnamdi Azikiwe University, Awka, Nigeria

2Transmission Company of Nigeria (TCN)

*Corresponding Author:
Ezennaya SO
Department of Electrical Engineering Nnamdi
Azikiwe University, Awka, Nigeria
Tel: +234 806 049 2273
E-mail: [email protected]

Received Date: July 13, 2015; Accepted Date: December 25, 2015; Published Date: January 01, 2016

Citation: Ezennaya SO, Ezechukwu OA, Anierobi CC, Akpe VA (2016) Expansion of Power System Corridors Using Tier-1 Technique for Reactive Power Compensation. J Electr Electron Syst 5:163. doi:10.4172/2332-0796.1000163

Copyright: © 2016 Ezennaya SO, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Abstract

This paper develops a novel strategy for the expansion of the power system corridors for the release of the embedded transmission capacity. Both theoretical and practical network models are presented with a focus on power flow studies which concentrates on the steady state or static behavior of electrical power system. The methodology involves the power flow analysis revalidation of the existing standard IEEE 14 bus system and simulation using Newton- Raphson method in both MATLAB and Powerworld simulator (PWS) environment. This paper therefore establishes that an original designed network could be modified to take more loads without building new generators or transmission lines. The expansion of the existing IEEE 14 bus network to accommodate more load involves the use of static compensators incorporated at the transmission lines. This technique is then analyzed extensively when distributed along the lines through the use of a distributed capacitors compensators, (DCC). DCC can affect significant change in power line impedance to improve the power transfer capacity of an interconnected power system. The application of the DCC on the line is the tier-1 technique. The results obtained show that by applyingthe tier-1 techniques to the transmission line, the system’s capacity will remarkably improve and the transmission line will accept extra loading.

Keywords

Power corridors, Newton-Raphson, Static compensators, DCC, Tier-1 compensation

Overview

Electrical energy efficiency is of prime importance to industrial and commercial companies operating in today’s competitive markets. Optimum use of power system components is one main concern that needs to be balanced with energy efficiency, for both economic and environmental reasons. Electricity plays a fundamental role in the economic development of any country. Every country seeks to ensure supply of electricity that is affordable, reliable and secure in order to sustain modern ways of living. The availability of electricity greatly facilitates industrialization. This is because, electricity is a convenient way to transport energy in which they are also converted into transmission, distribution, and consumption [1]. Investigations are done in this paper to see how capacitors distributed along the transmission lines can expand the transmission line corridor by the release of embedded transmission capacity.

During the past two decades, the increase in electrical energy demand has presented higher requirements from the power industry. In interconnected power systems, it has become important to fully utilize the existing transmission facilities in preference to building new power plants and transmission lines that are costly to implement and involving long construction times. This necessitated the need for alternative technology through the use of solid state electronic devices with fast response characteristics [2]. The requirement was fuelled by worldwide restructuring of electric utilities, increased environmental and efficiency regulations and difficulty in getting permit and right of ways for the construction of overhead power transmission lines. Different approaches such as reactive power compensation and phase shifting have been applied to increase the capacity, stability and security of the power system. This need in conjunction with the development of semiconductor thyristor switch opened the door for the development of flexible alternating current transmission system (FACTS) controllers [3]. FACTS controllers make it possible to control the voltage magnitude of a bus, active and reactive power flows through transmission line of a system.

Power systems control

Reactive power control service should satisfy the following system requirements [4];

1. Satisfy overall system and customer requirements for reactive energy on a continuous basis;

2. Maintaining system voltages within acceptable limits;

3. Provide a reserve to cover the changed reactive requirements caused by contingencies, against which the system is normally secured, and satisfy certain quality criteria in relation to speed of response;

4. Optimize system losses.

Three tiers could be established in reactive power control. These are tier-1, tier-2, and tier-3 controls. However, two or more of the three tiers can simultaneously be applied to form a hybrid tier control. A description of the three tiers of reactive power control could be made;

a. Tier-1 control co-ordinates the action of voltage and reactive power control devices within the transmission zones of the network in order to maintain the requisite voltage level at a certain node points in the system.

b. Tier-2 control involves a process of load optimization by improving load power factors which influence the distribution of reactive power, where the system load is high, and the operator must be certain that, in case of a loss of generation, the remaining facilities will be able to deliver enough reactive power to keep the voltage within the required range. The same applies to the converse situation, where the system load is low and reactive power needs to be absorbed.

c. Tier-3 control is the generator control.

d. Hybrid-Tier control is the simultaneous application of both the tier-1, and tier-2 or tier-3. It can also involve the control at the three tier controls to the power system at the same time.

Sources of reactive power

Reactive power is produced or absorbed by all major components of a power system [4];

1. Generators

2. Power transfer components

3. Loads

4. Reactive power compensation devices

Power Systems Reactive Power Compensation

Reactive power compensation otherwise called reactive var compensation is the management of reactive power to improve the performance of AC power systems, maximizing stability by increasing flow of active power. Compensation can be carried out in series or in parallel (shunt). Series and shunt var compensation are used to modify the natural electrical characteristic of AC transmission or distribution system parameters as well as changes the equivalent impedance of the load.

1. devices for reactive power compensation

2. synchronous condensers

3. Flexible alternating current transmission system (FACTS) controllers.

4. the distributed capacitor compensation (DCC)

The distributed capacitor compensation (Dcc) basis

There are many different methods used for compensation in power systems. Some of these methods include reducing generator and transformer reactance, increasing the number of parallel lines used, using shunt capacitor compensators, or using series capacitor compensators [5].

DCC can be used in series or in parallel on a transmission line. The addition of DCC in series serves multiple purposes, the most important being the improvement in stability along the entire line. Its addition in parallel (shunt compensation) is used to support voltage at certain point on the line as opposed to the entire line and also inject or absorb reactive power to the loads. Series and Shunt compensation have been in use since the early part of the 20th century. The first application of shunt compensation was in 1914 and has been used ever since becoming the most common method of capacitive compensation. Series compensation was first used in the United States for NY Power & Light in 1928, but didn’t become popular until the 1950’s when the voltage levels that could be handled began increasing. By 1968, a 550 kV application had been implemented and today there are applications approaching 800 kV [6].

The principal applications of DCC are;

• Improves voltage regulation

• Expand power transmission corridor of the transmission line

• Improves system stability

The applications previously mentioned are merely a selected few of the uses that DCC devices can provide. These applications and others are used throughout the world to improve the system as a whole. One common location where DCC devices are used heavily is on long transmission lines fed from hydroelectric generating plants. Many of the lines use the DCC devices to improve voltage regulation because the main load area is commonly several hundred kilometers from the generating station, allowing for large voltage decay.

DCC circuit

Capacitor compensator circuit is made up of the capacitor module and its protective scheme. The protective scheme shown in Figure 1 consists of [7];

electrical-electronic-systems-single-line

Figure 1: The single line diagram of a one-capacitor compensator in series.

1. A metal oxide varistor (MOV)

2. Current limiting damping equipment (CLDE)

3. Fast protective Device (FPD) and

4. By-pass switch (B)

The MOV has been designed to withstand the energy from external faults; faults appearing outside the series compensated circuit, without by-passing the DCC. The DCC module may be by-passed for any internal fault, (faults in the same circuit where the DCC is located). Each DCC is connected and disconnected from the line by means of two isolating disconnectors and one by-pass disconnector. The by-pass switch is of Sf6 type, with a spring operating mechanism.

The CLDE consists of a current limiting reactor, a resistor and a varistor in parallel with the reactor. The purpose of the resistor is to add damping to the capacitor discharge current, and thus quickly reduce the voltage across the capacitor after a by-pass operation. The varistor help to avoid fundamental frequency losses in the damping resistor during steady state operation.

The FPD scheme is based on a hermetically sealed and very fast high power switch, which replaces conventional spark gaps. The FPD works in combination with the MOV, and allows by-passing in a very controlled way in order to reduce the energy dissipated in the MOV.

The Mathematical Model of Tier-1 Compensation

Electrical power is transmitted through the transmission line from the sending-end of the line to the receiving-end of the line. This can be analyzed through parameterization and modeling of the transmission line with passive components such as resistors, capacitors and inductors. The quantities of these parameters depend mostly on the line conductors and the physical or geometrical configuration of the lines. These conductors will have certain characteristics such as resistance and reactance both in series (from sending to receiving-ends of the line) and shunts (from the line to ground) associated with them.

Basic principle of power in transmission

Loads are more often expressed in terms of real (watts/KW) and reactive (vars/Kvars) power. It is convenient to deal with transmission line equations for the sending and receiving-end complex power and voltages [8,9].

For a two-bus system shown in Figure 2, the sending and receivingend voltages are represented by the bus voltages while the sending end voltage leads the receiving end voltage by an angle, δ. This angle is called the torque angle. The complex power leaving the receiving end and entering the sending-end of the transmission line can be expressed as

electrical-electronic-systems-bus-system

Figure 2: A two bus system.

Equation and Equation (1)

Where

Equation And

Equation (2)

Similarly,

Equation (3)

Equation (4)

At Equation , the maximum power delivered at the load will be;

Equation (5)

If, Equation (6)

But the resistance R of a transmission line is very small compared to its reactance, so that;

Equation (7)

Where Equation and Equation

Therefore the receiving-end power (Pj) becomes;

Equation and Equation (8)

Hence Equation

For a very small value of δ, cos δ=1 thus;

Equation (9)

where Equation (10)

|ΔV| is called the magnitude of voltage drop across the transmission line.

Therefore;

Equation (11)

Reactive Power compensation of transmission lines

Equations (8) through (11) indicate that the active and reactive power/current flow can be regulated by controlling the voltages, phase angles and line impedances of the transmission system. It has been shown above that the active power flow will reach the maximum when angle δ is 900.

Series Compensation of A Transmission Line: A series-connected capacitor adds a voltage in opposition to the transmission line voltage drop, therefore reducing the series line impedance.

Figure 3 show a simplified model of a transmission system with series compensation. The voltage magnitude of the sending-end is assumed equal as |V|, and the phase angle between them is δ. The transmission line is assumed lossless and represented by the reactance XL. A control capacitor is series-connected in the transmission line with voltage addition Vinj.

electrical-electronic-systems-simplified

Figure 3: A simplified model of transmission system with series compensation.

The Degree Of Series Compensation (Ks): The degree of series compensation or percentage compensation (Ks) is used to analyze a transmission line with the required addition of series capacitor. It is defined as the fraction of Xc, which refers to the total capacitive reactance of series compensators and XL, which refers to the total inductive reactance of the line, as defined in equation 12;

Equation (12)

Therefore, the capacitance, C as a portion of the line react Equation ance can be obtained from

Equation (13)

and

Equation (14)

The overall series reactance, X of the transmission line is;

Equation (15)

Thus the active power transmitted becomes;

Equation (16)

The reactive power supplied by the capacitor is calculated as;

Equation (17)

From the above equation, it can be seen that transmitted active power increases with Ks [10].

Effective line reactance with and without dcc device

Figure 4 shows a simple transmission line without a compensating device. Equation (18) is the effective line reactance in matrix form.

electrical-electronic-systems-transmission

Figure 4: A simple transmission line without compensation.

Equation (18)

Where Xeff is the effective reactance of the line.

The power flow equation becomes

Equation (19)

Inserting a single series capacitor device on the line as in Figure 4 changes the ABCD parameters and the effective reactance of the line becomes (Figure 5)

electrical-electronic-systems-device

Figure 5: A transmission line with single DCC device (compensated line).

Equation (20)

As the power flow equation changes to;

Equation (21)

The ABCD parameters are halved because the DCC is place at exactly midpoint (Figure 6) to the length of the line hence one DCC device is used.

electrical-electronic-systems-multiple

Figure 6: A transmission line with multiple DCC devices.

Inserting several series capacitor devices on the line will change the ABCD parameters hence the more the capacitors on the line are distributed, the better the performance. Figure 6 shows a transmission line with multiple series capacitor devices and equation 21 changes to;

Equation (22)

The ABCD constants are divided by four (Figure 6) when the DCC is placed at quarter of the line hence three Capacitors are used and placed at every quarter of the line.

Power flow including dcc in matrix forms

From equation (21), the transfer admittance matrix of the DCC is given by [11];

Equation (23)

Where

Equation (24)

Equation (23) holds for inductive operation while for capacitive operation, the sign are reversed. The active and reactive power equations at bus j are as in equations (25) and (26) below;

Equation (25)

Equation (26)

In Newton-Raphson solutions, these equations are linearized with respect to the series reactance. For the condition shown in Figure 3 where series reactance regulates the amount of active power flowing from bus i to j at a value P, [11] the set of linearized power equation is,

Equation (27)

Equation (28)

Where, Equation is the active power flow mismatch for the series reactance calculated;

Equation (29)

Equation is the incremental change in series reactance; and Equation is the calculated power given by equation (25). The state variable Xc of the DCC controller is updated at the end of each iterative step according to equation (30);

Equation (30)

The Standard IEEE 14 Bus Test Systems (Revalidation)

One of the international load flow test systems is the IEEE- 14 bus system. Load flow analysis is carried out in IEEE 14 bus test system. Figure 7 show the standard IEEE 14 bus network simulated in Powerworld platform. The run mode of Power world simulator enable the simulation of the existing IEEE 14 bus test system model using N-R iterative method to obtain the bus voltages, phase angles, line losses, real and reactive power flows. The system topology consists of 14 buses, 20 transmission lines or branches, 2 online generators, 3 online synchronous compensators used only for reactive power support, and 11 loads totaling 259 MW and 78.7 Mvar.

electrical-electronic-systems-test-system

Figure 7: Standard IEEE 14 bus test system in Powerworld simulator environment.

The simulated result of the test system in Power world shown in Table 1 gives a very close result when compared with the MATLAB results of Table 2. It was therefore confirmed that the result obtained when DCC is applied on the IEEE 14 bus network using only Power world simulation software due to its flexibility and simplicity.

Line records MW From MW To Max MW Mvar From Mvar To Max Mvar MVA From MVA  To Max MVA Amps From Amps To Max Amps MW Loss Mvar Loss
From NO To NO
1 2 158.4 153.333 158.366 -32.5 42.612 42.612 161.7 159.144 161.633 676.35 671.202 676.35 5.03 10.13
1 5 75.9 -72.8 75.917 -0.1 8.218 8.212 75.9 73.263 75.917 317.615 316.494 317.615 3.12 8.1
2 3 74.3 -71.654 74.289 -3.1 9.958 9.958 74.4 72.342 74.353 313.588 311.998 313.588 2.64 6.89
2 4 56.1 -54.205 56.061 -2.0 4.028 4.028 56.1 54.354 56.096 236.587 235.762 236.587 1.86 2.05
2 5 41.3 -40.295 41.283 -0.3 0.015 0.268 41.3 40.295 41.283 174.116 174.074 174.116 0.99 -0.25
3 4 -22.5 23.019 23.019 11.0 -13.064 13.064 25.1 26.468 26.468 105.256 114.804 114.804 0.48 -2.02
4 5 -62 62.574 62.574 11.1 -10.468 11.074 63 63.443 63.443 273.192 274.074 274.074 0.57 0.61
4 7 29 -28.962 28.962 -3.1 5.033 5.033 29.1 29.396 29.396 126.351 126.351 126.351 0.00 1.91
4 9 16.4 -16.431 16.431 1.1 0.534 1.087 16.5 16.439 16.466 71.424 71.424 71.424 0.00 1.62
5 6 42.9 -42.922 42.922 0.6 4.317 4.317 42.9 43.139 43.139 185.444 185.444 185.444 0.00 4.95
6 11 6.6 -6.584 6.636 2.8 -2.707 2.816 7.2 7.118 7.209 30.988 30.988 30.998 0.05 0.11
6 12 7.7 -7.604 7.688 2.5 -2.278 2.454 8.1 7.938 8.07 34.693 34.693 34.693 0.08 0.18
6 13 17.4 -17.156 17.401 6.9 -6.429 6.911 18.7 18.322 18.724 80.488 80.488 80.488 0.24 0.48
7 8 0 -0.006 0.006 -14.7 15.132 15.132 14.7 15.132 15.132 63.308 63.308 63.308 0.00 0.4
7 9 29 -28.956 28.956 9.7 -8.613 9.695 30.5 30.21 30.536 131.253 131.253 131.253 0.00 1.08
9 10 5.9 -5.922 5.943 5.0 -4.911 4.966 7.7 7.694 7.745 33.649 33.649 33.649 0.02 0.05
9 14 10 -9.973 9.953 4.1 -3.8 4.139 10.8 10.505 10.779 46.831 13.996 13.996 0.16 0.34
10 11 -3.1 3.084 3.084 -0.9 0.907 0.907 3.2 3.215 3.215 13.996 7.215 7.251 0.01 0.02
12 13 1.5 -1.498 1.504 0.7 -0.673 0.679 1.7 1.642 1.651 7.251 23.336 23.366 0.01 0.01
13 14 5.2 -5.103 5.156 1.3 -1.197 1.305 5.3 5.241 5.319 23.336 23.336 23.336 0.05 0.11
Total 490 474.547 666.151 0.1 36.614 148.663 693.3 685.3 696.604 2948.71 2947.414 2956.14 15.31 36.77

Table 1: Line records of the standard IEEE 14 bus system in Power world simulator.15.31-0.25.

Number Name Nom kV PU Volt Volt (kV) Angle (Deg) Load MW Load Mvar Gen MW Gen Mvar s.shtMvar
1 1 138 1.00000 138.00 0.00     234.28 -32.6  
2 2 138 0.99197 136.892 -5.76 21.7 12.7 40 50  
3 3 138 0.97006 133.869 -14.57 94.2 19 0 40  
4 4 138 0.96454 133.107 -11.69 47.8 0      
5 5 138 0.96845 133.646 -9.99 7.6 1.6      
6 6 138 0.97323 134.306 -16.58 11.2 7.5 0 24  
7 7 138 0.97334 134.322 -15.39          
8 8 138 1.00000 138.000 -15.39     0 15.13  
9 9 138 0.96294 132.886 -17.34 29.5 16.6     17.62
10 10 138 0.95663 132.015 -17.55 9 5.8      
11 11 138 0.96106 132.626 -17.23 3.5 1.8      
12 12 138 0.95722 132.097 -17.61 6.1 1.6      
13 13 138 0.95233 132.422 -17.7 13.5 5.8      
14 14 138 0.93845 129.507 -18.71 14.9 5      

Table 2: Bus records of IEEE 14 bus system in Powerworld simulator.

Using codes written in MATLAB and system information exported from Power world simulator, the standard IEEE 14 bus network is revalidated and reconfirmed.

Simulation result

The revalidated Standard IEEE 14 bus network shows that the total real and reactive power loss of the system are 15.31 MW and 36.77 Mvar respectively with the systems maximum current rating totaling 2948.91 Amps. As a result, the system’s maximum MVA loading becomes 696.604 MVA. These results confirmed and agreed with the standard performance of the standard IEEE 14 bus system as shown in Tables 1 and 2 (Power world simulator tool) and Table 2 (MATLAB simulator tool). All bus voltages were also confirmed to fall within the recommended limit (0.9 ≤ V ≤ 1.1 p.u).

Total power loss in Powerworld simulator: 15.31 MW and 36.77 Mvar

The Table 3 confirmed that the standard IEEE 14 bus system total power loss in Powerworld simulator is 15.31 MW and 36.77 Mvar and that of MATLAB is 15.031 MW and 35.348 Mvar. This is a clear indication that the software tool used for this model is validated.

Bus No. Bus Voltage Load Generation Injected Mvar
Magnitude Angle MW MVAR MW MVAR
1 1.050 0 0 0 234.029 61.659 0
2 1.000 -4.664 21.7 12.7 40 -11.307 0
3 0.970 -13.283 94.2 19 0 36.233 0
4 0.964 -10.372 47.8 0 0 0 0
5 0.970 -8.79 7.6 1.6 0 0 0
6 1.000 -15.109 11.2 7.5 0 14.105 0
7 0.979 -13.768 0 0 0 0 0
8 1.000 -13.768 0 0 0 12.064 0
9 0.963 -15.594 29.5 16.6 0 0 0
10 0.962 -15.835 9 5.8 0 0 0
11 0.977 -15.608 3.5 1.8 0 0 0
12 0.982 -16.085 6.1 1.6 0 0 0
13 0.976 -16.134 13.5 5.8 0 0 0
14 0.949 -17.014 14.9 5 0 0 0

Table 3: The bus records of the IEEE 14 bus system in MATLAB tool.

Case 1: Modification of the ieee 14 bus network (addition of an excess load to the network)

To illustrate that an already saturated network can be expanded by the use of capacitors distributed along the lines at strategic places, an existing load of a selected Company in Nigeria was used - the General Steel Mills (GSM), Asaba. The Company’s total maximum active and reactive power demand are 17.80 MW and 25.71 Mvar respectively [12]. These loads were added to bus 6 of the standard IEEE 14 bus system which modified the revalidated results of the system. The active and reactive power losses increased from the normal operating performance of the 14 bus standard network to 59.85 MW and 226.84 Mvar respectively. The system’s maximum amperage was 5658.287 Amps as all the bus voltages dropped below 0.9 p.u except the slack bus-bus 1 (Table 4). The MVA maximum loading also increased to 1062.225 MVA (Overloading). For these reasons, it is enough to say that the modified IEEE 14 bus system got overloaded and cannot accept this extra load (Table 5).

Bus records Nom kV PU Volt Volt (kV) Angle (Deg) Load MW Load MVar Gen MW Gen MVar s.shntsMvar
NO Name
1 1 138 1 138 0     256.71 371.82  
2 2 138 0.82572 113.95 -4.21 21.7 12.7 40 50  
3 3 138 0.62455 83.188 -17.9 91.53 19.72 0 0  
4 4 138 0.59434 82.018 -10.26 45.16 113.38      
5 5 138 0.6584 90.859 -8.27 7.53 1.59      
6 6 138 0.48283 66.63 -24.44 13.9 20.07 0 0  
7 7 138 0.51624 71.241 -19.52          
8 8 138 0.51624 71.241 -25.52     0 0  
9 9 138 0.48187 66.497 -26.41 22.98 12.53     0
10 10 138 0.4696 66.804 -25.93 6.8 4.38      
11 11 138 0.47045 64.923 -27.46 2.65 1.36      
12 12 138 0.45884 63.32 -27.67 4.48 1.18      
13 13 138 0.45279 62.486 -27.67 9.75 4.19      
14 14 138 0.43901 6.583 -30.11 10.35 3.47      

Table 4: Bus records of the modified standard IEEE 14 bus network (with 17.80 MW and 25.71 Mvar extra load addition).

LINE RECORDS MW From MW To Max MW Mvar from Mvar To Max Mvar MVA From MVA To Max MVA Amps From Amps To Max Amps MW loss Mvar loss
From NO To NO
1 2 180.8 163.425 180.84 236.4 187.704 236.434 297.7 248.879 297.665 1234.34 1260.995 1260.995 17.41 48.73
1 5 75.9 -62.494 75.872 135.4 -83.694 135.39 155.2 104.452 155.2 649.309 663.723 663.723 13.38 51.7
2 3 78.9 -70.943 78.86 71.1 -40.085 71.092 106.2 81.485 106.74 537.953 545.84 545.84 7.92 32.01
2 4 59.1 -49.186 59.135 89.1 -60.896 89.147 107 78.279 106.978 542.024 551.028 551.028 9.95 28.25
2 5 43.7 -38.501 43.728 64.8 -50.701 64.764 78.1 63.662 78.144 395.932 404.532 404.532 5.23 14.06
3 4 -20.6 22.075 22.075 20.4 -17.848 20.36 29 28.338 28.953 193.949 199.83 199.83 1.49 2.51
4 5 -55.2 58.335 58.335 -72.6 81.951 81.951 91.2 100.593 100.593 641.907 639.204 641.907 3.13 9.37
4 7 23.6 23.608 23.608 24.1 -17.367 24.107 33.7 29.308 33.741 237.514 237.514 237.514 0.00 6.74
4 9 13.5 -13.546 13.546 13.8 -7.931 13.832 19.4 15.697 19.36 137.283 136.283 136.283 0.00 5.9
5 6 35.1 -35.126 35.126 50.9 -28.647 50.857 61.8 45.326 61.108 392.751 392.751 392.751 0.00 22.21
6 11 3.6 -3.543 3.603 1.3 -1.196 1.322 3.8 3.74 3.838 33.258 33.258 33.258 0.06 0.13
6 12 5.5 -5.339 5.521 2 -1.617 1.995 5.9 5.579 5.87 50.866 50.866 50.866 0.18 0.38
6 13 12.1 -11.607 12.101 5.3 -4.28 5.252 13.2 12.371 13.192 114.305 114.305 114.305 0.49 0.97
7 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0
7 9 23.6 -23.608 23.608 17.4 -13.822 17.367 29.3 27.356 29.308 237.514 237.514 237.514 0.00 3.55
9 10 6 -5.914 5.995 4.8 -4.558 4.772 7.7 7.467 7.662 66.525 66.525 66.525 0.08 0.21
9 14 8.2 -7.718 8.174 4 -3.078 4.047 9.1 8.31 9.121 79.189 79.189 79.189 0.45 0.97
10 11 -0.9 -0.892 0.892 0.2 -0.167 0.175 0.9 0.908 0.908 8.071 8.071 8.071 0.00 0.01
12 13 0.9 -0.847 0.856 0.4 -0.433 0.442 1 0.951 0.964 8.786 8.786 8.786 0.01 0.01
13 14 2.7 -2.633 2.696 0.5 -0.393 0.521 2.7 2.662 2.746 25.37 25.37 25.37 0.06 0.13
Total 496.5 436.736 654.571 669.3 442.466 823.827 1052.9 865.413 1062.25 5596.846 5655.584 5658.287 59.85 226.84

Table 5: Line records of the modified standard IEEE 14 bus network (with 17.80 MW and 25.71 Mvar extra load addition).

Case 2: Application of tier-1 compensation to the modified standard IEEE 14 bus network

The distributed capacitor technology applied on the transmission lines were used in this case to know how much the lines can be freed of their carriage even when the loads were operating. This was verified by placing capacitors on all the lines (interline action) with degree of compensation Ks allowed to operate by 0.7 or 70% of the original line reactance value (Table 6). The bus and line results were compared, from which the total active power loss reduced from 59.85 to 17.79 MW (70.28% reduction) while the total reactive power loss reduced from 226.84 to 59.17 Mvar (73.92% reduction). By this margin, the system’s MVA loading was released from 1062.225 to 744.193 MVA (29.94% released) (Figure 8). This is resulted from the reduction in system’s current from 5658.287 to 3212.958 Amps (43.94% reduction) with all lines still operating within their normal limits. Bus voltages were also restored appreciably (Table 7).

electrical-electronic-systems-standard

Figure 8: Modified standard IEEE 14 bus network with tier-1 compensation.

Bus records Nom kV PU Volt Volt (kV) Angle (Deg) Load MW Load MVar Gen MW Gen MVar s.shntsMvar
NO Name
1 1 138 1.0000 138 0.01     243.29 48.73  
2 2 138 0.96558 133.25 -1.46 21.7 12.7 40 50  
3 3 138 0.9115 125.787 -3.67 94.2 19.0 0 0  
4 4 138 0.92276 127.34 -2.72 47.8 0.00      
5 5 138 0.93304 128.76 -2.25 7.6 1.6      
6 6 138 0.90345 124.676 -4.59 17.8 25.71 0 0  
7 7 138 0.90974 125.544 -4.06          
8 8 138 0.90974 125.544 -4.06     0 0  
9 9 138 0.90309 124.627 -4.78 29.5 16.6     0
10 10 138 0.89828 123.962 -4.78 9 5.8      
11 11 138 0.89837 123.975 -4.7 3.5 1.8      
12 12 138 0.8919 123.028 -4.8 6.1 1.6      
13 13 138 0.88911 122.697 -4.77 13.5 5.8      
14 14 138 0.88218 121.741 -5.01 14.9 5.0      

Table 6: Bus records of the Modified standard IEEE 14 bus network with tier-1 compensation.

LINE RECORDS MW From MW To Max MW Mvar from Mvar To Max Mvar MVA From MVA To Max MVA Amps From Amps To Max Amps MW loss Mvar loss
From NO To NO
1 2 161.1 -156.037 161.15 22.3 -11.831 22.333 162.7 156.49 162.69 677.898 680.23 680.23 5.11 10.5
1 5 82.1 -77.844 82.141 37.9 -24.778 37.889 90.5 81.693 90.459 308.555 375.837 375.837 4.3 13.11
2 3 78 -74.856 78.019 29.9 -19.244 29.875 83.5 77.019 83.544 354.832 350.199 350.199 3.44 10.63
2 4 55.6 -53.473 55.59 17.7 -14.656 17.742 58.4 55.445 58.352 250.09 254.31 254.31 2.12 3.09
2 5 40.7 -39.561 40.278 15.4 -14.892 15.393 43.5 42.271 43.54 186.856 191.631 191.631 1.17 0.5
3 4 -19.6 19.963 19.963 5.7 -5.885 5.885 20.4 20.812 20.812 93.387 94.364 94.364 0.34 0.21
4 5 -63.7 64.349 64.349 -6.9 8.912 8.912 64.1 64.963 64.963 290.858 290.868 290.868 0.65 2.04
4 7 31.4 -31.398 31.398 21.9 -18.51 21.866 38.3 36.448 36.262 167.615 167.615 167.615 0.00 3.36
4 9 18 -18.016 18.016 13.3 -10.317 13.256 22.4 20.761 22.367 96.176 96.176 96.176 0.00 2.94
5 6 45.5 -45.456 45.456 44.5 -34.435 44.476 63.6 57.027 63.595 264.079 264.079 264.079 0.00 10.04
6 11 4.2 -4.222 4.244 1 -0.905 0.951 4.3 4.317 4.349 20.122 20.12 20.12 0.02 0.05
6 12 7.2 -7.106 7.191 2.2 -2.308 2.214 7.5 7.393 7.524 34.677 34.677 34.677 0.8 0.18
6 13 16.2 -15.985 16.244 6 -5.558 6.03 17.3 16.923 17.309 79.633 79.633 79.633 0.24 0.47
7 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0
7 9 31.4 -31.398 31.398 19.7 -17.98 19.745 37.1 36.982 37.091 167.615 167.615 167.615 0.00 1.77
9 10 8.3 -8.277 8.321 6.8 -6.68 6.799 10.7 10.636 10.746 49.539 49.539 49.539 0.04 0.12
9 14 11.7 -11.434 11.686 5.4 -4.821 5.356 12.9 12.409 12.855 58.85 58.85 58.85 0.25 0.53
10 11 -0.7 0.722 0.722 0.9 -0.879 0.882 1.1 1.138 1.139 5.298 5.298 5.298 0.00 0.00
12 13 1.00 -1.033 1.007 0.4 -0.437 0.44 1.1 1.094 1.099 5.15 5.15 5.15 0.00 0.00
13 14 3.5 -3.463 3.489 0.2 -0.179 0.233 3.5 3.468 3.497 16.455 16.455 16.455 0.03 0.05
Total 511.9 494.215 681.092 244.3 185.113 260.278 742.9 706.48 744.193 3187.685 3212.958 3212.958 3212.958 59.17

Table 7: Line Records of the the Modified standard IEEE 14 bus network with tier-1 compensation.

Figures 9A-9D show the graphical plots of line numbers of the Modified standard IEEE 14 bus network (with tier-1 compensation) against the MW, Mvar, MVA loadings and bus p.u voltages with and without compensation.

electrical-electronic-systems-voltages

Figure 9: Show the graphical plots of line numbers of the Modified standard IEEE 14 bus network (with tier-1 compensation) against the MW, Mvar, MVA loadings and bus p.u voltages with and without compensation.

The percentage reduction in MVA loading and savings determines how much the systems corridors have been expanded by the release of the embedded system capacity on which the system can be available for extra loadings (Table 8).

    The modified IEEE 14 bus system (overloaded system) Use of tier-1 compensator
Bus records Nom kV PU Volt Volt (kV)   PU Volt   Volt (kV)
NO Name
1 1 138 1 138 1.0000 138
2 2 138 0.82572 113.95 0.96558 133.25
3 3 138 0.62455 86.188 0.9115 125.787
4 4 138 0.59434 82.018 0.92276 127.34
5 5 138 0.6584 90.859 0.93304 128.76
6 6 138 0.48283 66.63 0.90345 124.676
7 7 138 0.51624 71.241 0.90974 125.544
8 8 138 0.51624 71.241 0.90974 12.544
9 9 138 0.48187 66.497 0.90309 124.627
10 10 138 0.4696 64.804 0.89828 123.962
11 11 138 0.47045 64.923 0.89837 123.975
12 12 138 0.45884 63.32 0.8919 123.082
13 13 138 0.45279 62.486 0.88911 122.697
14 14 138 0.43901 60.583 0.88218 121.741

Table 8: Comparison of the modified IEEE 14 bus system voltage performance against operation results of the tier-1 voltage result as a mean of validating the proposed compensation strategy for the bus records.

Conclusion

The use of DCC creates more loops in the transmission system by providing more active power routes without having to build new generating stations, new transmission stations or dealing with rightof- way issues. Application of the tier-1 compensation was able to accommodate the added load in the existing 14 bus system by releasing the system up to 29.94% MVAof its overloading which remarkably reduced the system’s active losses by 70.28% and reactive losses by 73.92%. Recommendations are made to simultaneously apply also the teir-2 and 3 to the network in other to ensure maximum restoration of the power (up to 100% restoration). This efficient control method can salvage the power system from total collapse and as well serves as a quick way to respond to consumers power satisfaction quest.

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