FINAL DATA SHEET
Experiment No. 1 – Short Line Investigation
Name: Carvey Ehren R. Maigue
Table 1 – Resistive Load
R
(ohm)
50
45
40
35
30
25
20
15
10
Vs
(peak)
140∠90
140∠90
140∠90
140∠90
140∠90
140∠90
140∠90
140∠90
140∠90
Is
(peak)
2.75∠97.94
3.04∠98.8
3.41∠99.87
3.87∠102.22
4.48∠103.01
5.3∠105.45
6.47∠108.98
8.25∠114.48
11.11∠123.95
Ps
(rms)
190.55
210.58
235.16
265.97
305.53
357.74
428.51
525.38
645.35
Vd
(peak)
19.37∠11.6
21.46∠12.46
24.04∠13.53
27.31∠14.88
31.58∠16.67
37.38∠19.11
45.63∠22.64
58.13∠28.14
78.34∠37.61
Vr
(peak)
137.42∠97.94
136.98∠98.8
136.4∠99.87
135.58∠101.22
134.39∠103.01
132.55∠105.45
129.47∠108.98
123.7∠114.48
111.14∠123.95
Ir
(peak)
2.75∠97.94
3.04∠98.8
3.41∠99.87
3.87∠101.22
4.48∠103.01
5.3∠105.45
6.47∠108.98
8.25∠114.48
11.11∠123.95
Vr
(peak)
134.81∠97.54
133.83∠98.27
132.54∠99.14
130.77∠100.19
128.28∠101.47
124.65∠103.02
119.16∠104.82
Ir
(peak)
2.67∠106.11
2.93∠107.78
3.26∠109.81
3.65∠112.35
4.15∠115.58
4.77∠119.8
5.58∠125.48
Pr
(rms)
%VR
%Eff
188.85
1.877456 99.10785
208.49
2.204701 99.0075
232.55
2.639296 98.89012
262.6
3.260068 98.73294
301.02
4.174418 98.52388
351.41
5.620521 98.23056
419.08
8.133158 97.79935
510.18
13.17704 97.10686
617.56
25.96725 95.69381
Table 2 – Resistive Load and Inductive Load
R
(ohm)
50
45
40
35
30
25
20
Vs
(peak)
140∠90
140∠90
140∠90
140∠90
140∠90
140∠90
140∠90
Is
(peak)
2.67∠106.11
2.93∠107.78
3.26∠109.81
3.65∠112.35
4.15∠115.58
4.77∠119.8
5.58∠125.48
Ps
(rms)
179.29
195.52
214.44
236.48
261.85
289.97
317.8
Vd
(peak)
18.79∠19.77
20.68∠21.44
22.95∠23.47
25.75∠26.01
29.23∠29.24
33.65∠33.46
39.3∠39.14
Pr
(rms)
%VR
%Eff
177.69
3.849863 99.10759
193.58
4.610327 99.00777
212.05
5.62849
233.47
7.058194 98.72717
257.98
9.136264 98.52205
284.84
12.31448 98.23085
310.81
17.48909 97.8005
98.88547
15
10
140∠90
140∠90
6.59∠133.33
7.81∠144.36
335.63
318.42
46.46∠46.99
55.03∠58.02
110.66∠106.64
97.77∠107.34
6.59∠133.33
7.81∠144.36
325.86
26.51365 97.08906
304.71
43.19321 95.69437
DIAGRAMS & CIRCUITS USED
Experiment No. 1 – Short Line Investigation
Fig 1.0
Fig 1.1
Fig 1.2
Fig 1.3
Fig 1.4
Fig 1.5
Fig 1.6
GRAPHS, CHARTS & CURVES
Experiment No. 1 – Short Line Investigation
Fig 2.0
Fig 2.1
Fig 2.2
Fig 2.3
Fig 2.4
Fig 2.5
Fig 2.6
Fig 2.7
Fig 2.8
Fig 2.9
Fig 2.10
Fig 2.11
DISCUSSION
Experiment No. 1 – Short Line Investigation
Software and Circuit
For this experiment, Tina Version 9.3.50.47 SF-DS has been used. The students were tasked to
determine the characteristics of the short line system under three conditions namely a.) No Load
Condition, b.) Purely Resistive Full Load Condition, c.) Partially Inductive Full Load Condition. To facilitate
ease of comparison between values and simulation curves under different conditions, figure 1.2 has been
used as an interpretation of figures 1.0 and 1.1. In this circuit, a 140 Vpeak 60 Hz Sinusoidal power supply
has been used. The short line transmission system has been modeled as a 0.45 Ohm Resistor in Series to
an 18.66 mH Inductor. The load side is modeled as a single resistive (range 10 – 50 Ohms) load (Purely
Resistive Full Load Condition) and as a resistive (range 10 -50 Ohms) load in series to a 20 mH inductor
(Partially inductive Full Load Condition). Some additional features have been added arbitrarily and as
follows:
Load Disconnect
To facilitate a no-load condition a disconnect switch labeled as “load disconnect” has been added.
It is placed after the wattmeter, ammeter and voltmeter of the receiving end to allow the meters measure
the open circuit parameters of the system. Placing the disconnect before the meters would yield
erroneous readings since the meters would also be disconnected from the system. The load disconnect
switch would allow ease of switching between a no load and full load condition.
Induction Load Transfer Switch
Another feature of the circuit is the inductive load transfer switch. It is used to connect the
resistive load either directly to ground (Purely Resistive Full Load Condition) or to the inductive load in
series (Partially Inductive Full Load Condition). This is useful for switching between conditions B and C
while viewing the phasor diagrams in real time to see the effect of increased induction in the load side.
Meters and Parameters
Additional meters have been arbitrarily added. A voltmeter has been added to measure the
voltage drop across the short line model. Two watt meters was also added both in the sending and
receiving end. However, caution should be applied as the meters output varying types of parameters. It
has been observed that the watt meters used RMS values, while the voltmeter and ammeter output peak
values. To obtain identical values to the wattmeter using the voltmeter and ammeter results, the apparent
power S should be divided in 2 beforehand. Figure 2.0 shows the time based simulation result of the six
meters showing the peak values and the phase differences. It can be observed that the peaks of the
amplitude for both ammeter and voltmeter are the same to the results using AC simulation Figure 1.3,
while the wattmeter peak is different from the result of the AC simulation and has a ratio of 2:1. This is
accurate with the equations:
𝑃𝑜𝑤𝑒𝑟𝑅𝑀𝑆 = (𝑉𝑜𝑙𝑡𝑎𝑔𝑒𝑅𝑀𝑆 )(𝐶𝑢𝑟𝑟𝑒𝑛𝑡𝑅𝑀𝑆 )
𝟏
𝟏
√𝟐
√𝟐
𝑉𝑜𝑙𝑡𝑎𝑔𝑒𝑅𝑀𝑆 = ( )(𝑉𝑜𝑙𝑡𝑎𝑔𝑒𝑝𝑒𝑎𝑘 ) and 𝐶𝑢𝑟𝑟𝑒𝑛𝑡𝑅𝑀𝑆 = ( )(𝐶𝑢𝑟𝑟𝑒𝑛𝑡𝑝𝑒𝑎𝑘 )
1
1
√
√
1
𝑃𝑜𝑤𝑒𝑟𝑅𝑀𝑆 = ( 2)(𝑉𝑜𝑙𝑡𝑎𝑔𝑒𝑝𝑒𝑎𝑘 )( 2)(𝐶𝑢𝑟𝑟𝑒𝑛𝑡𝑝𝑒𝑎𝑘 ) = (2)(𝑉𝑜𝑙𝑡𝑎𝑔𝑒𝑝𝑒𝑎𝑘 )(𝐶𝑢𝑟𝑟𝑒𝑛𝑡𝑝𝑒𝑎𝑘 )
No load condition
The no load condition has been achieved by disconnecting the load models from the system via
the load disconnect switch. Its corresponding AC simulation was shown in figure 1.4. Several observations
can be drawn from the result. First, the voltages, both in magnitude and phase, remained the same both
in the receiving and the sending end as shown by the phasor diagram in figure 2.1. Second, there is no
significant voltage drop across the short line model. Third, there is no significant current reading through
the circuit, and lastly, there is no significant power reading across the watt meters.
The absence of load causes no significant current to flow through the circuit. Without current,
through the short line model or through the load, no voltage drops would occur. This would result to the
voltage of the sending end to equal the voltage of the receiving end. Without significant current through
the system, the watt meters would also not yield any output since the current is virtually zero.
Full load condition
Under full load condition both cases (fully resistive and partially inductive), showed immense
changes in the phasor diagrams shown in figure 2.2 and figure 2.3. Several observations can be drawn.
First, in both cases, one of the voltage phasors became offset by a certain angle. Second, new sets of
vectors emerged. These are caused by power readings from the watt meter and current readings in the
ammeter. Third, a voltage drop now occurs in the short line model. Fourth, upon AC analysis in both cases
as shown in figure 1.5 and figure 1.6, the current reading through the sending end and the receiving end
are the same but the voltages are different. Fifth, it is important to also take note that the angle of the
receiving and voltage is in phase with the current.
The presence of load causes current to flow. As current flows through the circuit, the impedance
from the short line model causes a voltage drop. This voltage drop explains the difference between the
sending and the receiving end value. Quantitatively it can be observed that the sending end voltage is the
summation of the voltage drop in the short line model and the receiving end voltage. Consequently, it can
also be derived that the difference in power reading between the sending and receiving end of the system
can be found as the power loss along the short line model. Quantitatively, it can be drawn that the sending
end power is the summation of the power loss along the short line model and the receiving end power.
These observations are consistent both under fully resistive conditions and under partially inductive
conditions. A main difference is the behavior of the receiving voltage angles and the current. Under the
fully resistive load condition, they are the same indicating a unity power factor. Under the partially
inductive load condition the angles are not in phase. These would later affect the presence or absence of
a reactive power component.
Magnitude of Voltages under varying loads
The experiment requires the students to sweep the resistive load values within the range of 10
Ohms to 50 Ohms, while observing the changes in parameters. Voltage effects can be seen in figure 2.4.
For both conditions, the sending voltage remained constant across varying R conditions. In terms of
magnitude of the receiving voltage, both under fully resistive and partially inductive load conditions
exhibited a direct proportionality to increasing load R. However, it is important to note that the fully
resistive load consistently has a higher magnitude than the partially inductive load across varying R values.
Lastly, it can also be seen that as the R value increases, the difference between the sending and receiving
voltage for both conditions decreases. This is accurate to the fact that no load can also be seen as an
infinite resistance R which would mean that increasing R values would tend to cause smaller differences
between the sending and the receiving voltage. A decrease between the sending and receiving voltage is
indicative that the voltage drop across the short line model is getting smaller due to voltage divider
between short line model and the load. This correlation is furthered by the horizontal symmetry between
the voltage drop trend line and the voltage values on the receiving end.
Magnitude of Currents under varying loads
The resulting currents after varying the loads across multiple values can be seen in figure 2.5.
Several observations can be drawn from the figure. First, in general, the current increases proportionally
to increasing load R. Second, the values are the same for the sending and receiving end for both conditions
across varying loads. It is an indicator that the load can be seen to be in series with the short line model
and the supply. Third, comparing the values of the Fully Resistive load condition and the Partially Inductive
condition, the former condition allows the current to increase at a higher rate as compared to the later.
This can be seen as an effect of introducing inductive impedance in the load side.
Power and Phasors
The resulting power readings after varying the loads across multiple values can be seen in figure
2.6 figure 2.7 and figure 2.8. The later are presented using apparent power values with both real and
reactive power component included. This was done to illustrate the effect of inductive loading to a short
line and can be used as a base case for further investigations. It can be revisited once medium and long
line transmissions are investigated where capacitance will be considered.
From the former figure it can be observed that the power values generally follow an inverse
relationship with increasing R values. This is accurate with the relationship of P and R with V held constant.
It can be observed that the fully resistive condition exhibits high power values compared to the partially
inductive condition particularly in the lower R values. It can be drawn that the absence of L as additional
impedance to the fully resistive load causes the power values to approach short circuit conditions more
drastically. This exhibits the use of the inductor in the load as additional impedance. It can also be seen in
general that the additional inductor of 20mH still impacts as an impedance in the overall system which
causes lower power values in general for the partially inductive condition test case.
From the two later figures it can observed that the purely resistive load condition does not exhibit
a reactive power component while the partially inductive load condition has a reactive component. This
is further evidenced by the difference in the behavior of phasor angle values in the receiving end voltage
and current under both conditions. Phasor angles are the same in the V and I parameters of the receiving
end under fully resistive conditions while the same does not hold true under partially inductive conditions.
Another notable characteristic can be seen on figure 2.8, there is a inflection in the real power
output as R is swept between 10 and 15. As shown in figures 2.9 and 2.10, after further investigation, by
sweeping values in the range within 10 and 15 with a higher resolution it was found that maximum real
power output occurs at around 13.88 Ohms such inflection does not appear to exist under purely resistive
full load condition.
Efficiencies and Voltage Regulation
It can be observed from figure 2.11 that as R load increases, efficiencies increase and voltage
regulation decreases. It is important to note that the partially inductive load condition tends to have
higher voltage regulation vs the purely resistive load condition.
CONCLUSION
Experiment No. 1 – Short Line Investigation
From the observations, analysis of results and discussion, the following can be drawn:





Under no load conditions the sending and receiving voltage are the same
For short line transmission systems, with the absence of significant capacitance value, the
line impedance can be seen to be in series with the load thus, the same current flow
through the system
Inductive load causes the load side to have a reactive power component and by increasing
the ratio induction to resistivity, the phase tends to lag further
For both purely resistive and partially inductive condition, the efficiency increases as the
load mix becomes more resistive while the voltage regulation exponentially decreases
Adding inductive load will cause the system to have an inflection point in terms of its
power and load curve. This might be related to maximum power transfer but further
investigation must be done to be conclusive.
Overall, the experiment has been successful. It allowed the students to determine short line
characteristics, identify the efficiency and voltage regulation of an inductive line and construct
phasor diagrams.
QUESTION AND ANSWERS
Experiment No. 1 – Short Line Investigation
1. What parameters are being considered in the analysis of the performance of short transmission lines?
Ans. The parameters considered are line resistance and line reactance, along with the sending end
parameters and load characteristic, efficiency and voltage regulation can be used to design and quantify
performance.
2. Why is the capacitance of the line not being considered in the analysis of the performance of short
transmission lines?
Ans. At short lengths, the capacitive impedance is too high as if it is an open line and thus no current will
flow through it.
3. What is the relationship between the sending end current and receiving end current in a short
transmission line?
Ans. They are the same because the load and the line are essentially in series
4. Why is the measured VD different from the difference between the sending end voltage and receiving
end voltages?
Ans. Because of the inductive component of the line where voltage drop is measured, the phasor angle
causes the magnitude to have an imaginary component thus skewing the magnitude.
5. Why is the power measured at the receiving end less than the power measured at the sending end?
Ans. Because there is a voltage drop and thereby a power loss in the line itself due to line impedance.
6. What is the significance of the series impedance in the transmission line?
Ans. The series impedance is significant because it represents inherent characteristics of the cabling, line
design, material type and other factors. It is significant because if it is not considered in the design, large
power losses can occur thus causing the system to be inefficient affecting service costs and ultimately
financial feasibility of the system as a means of delivering electricity. This can be seen as the “transmission
losses” in electric bills.
7. A short, three-phase transmission line with resistance and reactance of 8  and 11 respectively, is
supplied with a voltage of 11 kV. A balanced load P kW at 0.8 power factor is connected at the end of the
line. For what value of P is the voltage regulation of the line zero?
Ans.
Zline = 8 + j11 , Vs = 11kV , PFload = 0.8, P = ?
Vr = 11kV for %VR = 0
%VR =
√VrCosθr + IR2 + VrSinθr + IX 2
Vr
0=
√[(11000)(0.8) + I(8)]2 + [11000(0.6) + I(11)]2
11000