Power Systems Laboratory
Experiment – 1
Aim:-To observe the power flow and different modes on the network with different Load Variation Curves (LVC) Power System Diagrams:
Important Points:
1. There are 4 modes to operation of the transmission line sensors, based on the MVA power limit of the line: a. Normal Mode: up to 80%
b. Alert Mode: 80%-100%
c. Emergency Mode :100%-150% (The Transmission line will function only for a few hours,
d. Contingency Mode: 150% (Circuit breakers will break the circuit at this point to save transmission line damages)
2. The Software has several errors in garbage collection mechanism. There is need of resetting the values to zero , otherwise we get erroneous results such as 375% power flow through the lines without circuit breaker action.
3. Care has to be taken to maintain the proper circuit and area number in all the components of the po wer system. Otherwise, it leads to miscalculations and illogical results. The SAVE button has to be clicked on changing attributes of any component for proper effect.
4. Proper limits have to set on the generators and transmission lines, for realistic modeling of the given power system. For this experiment we have maintain the generator to have a capability limit of 600MW , the Slack bus Generator to have capability of 1000MW and the transmission lines capacity is 100MVA. All other values are default from the experimental setup
Load Variation Curves
Observations
Load variation : 1.5 Both lines closed
Bus 1 to 2
Bus 2 to 1
Time
MW
MVA
MW
MVA
00
0.26
0.3
-0.26
0.3
30
0.18
0.2
-0.18
0.2
60
0.33
0.3
-0.33
0.3
90
0.48
0.5
-0.48
0.5
120
0.26
0.3
-0.26
0.3
150
0.41
0.4
-0.41
0.4
180
0.48
0.5
-0.48
0.5
210
0.27
0.3
-0.27
0.3
240
0.20
0.2
-0.20
0.2
270
0.20
0.2
-0.20
0.2
300
0.20
0.2
-0.20
0.2
330
0.20
0.2
-0.20
0.2
360
0.20
0.2
-0.20
0.2
Load variation : 2.5 Both lines closed
Bus 1 to 2
Bus 2 to 1
Time
MW
MVA
MW
MVA
00
0.35
0.4
-0.35
0.4
30
0.22
0.2
-0.22
0.2
60
0.32
0.3
-0.32
0.3
90
0.31
0.3
-0.31
0.3
120
0.17
0.2
-0.17
0.2
150
0.29
0.3
-0.29
0.3
180
20.20
20.4
-20.07
20.4
210
45.85
46.1
-45.22
46.1
240
75.27
75.5
-73.57
75.5
255
55.39
56.6
-55.42
56.6
270
40.32
40.6
-39.83
40.6
285
14.84
15.0
-14.77
15.0
300
0.19
0.2
-0.19
0.2
305
-0.31
0.3
0.31
0.3
315
-0.5
0.5
0.5
0.5
330
-0.18
0.2
0.18
0.2
360
-0.38
0.4
0.38
0.4
Load variation : 3 Both lines closed
Bus 1 to 2
Bus 2 to 1
Time
MW
MVA
MW
MVA
00
0.34
0.3
-0.34
0.3
30
0.33
0.3
-0.33
0.3
60
0.28
0.3
-0.28
0.3
90
0.47
0.5
-0.47
0.5
120
0.45
0.5
-0.45
0.5
150
36.90
37.1
-36.49
37.1
180
74.38
74.6
-72.71
74.6
210
94.84
95.0
-92.14
95.0
240
115.69
115.8
-111.67
115.8
255
136.18
136.2
-130.61
136.2
270
149.44
149.4
-142.74
149.4
285
122.98
123.0
-118.44
123.0
300
97.45
97.6
-94.59
97.6
305
66.95
67.2
-65.59
67.2
315
40.69
40.9
-40.19
40.9
330
21.82
22.0
-21.68
22.0
360
-0.91
0.9
0.91
0.9
Load variation : 1.5 One line open
Bus 1 to 2
Bus 2 to 1
Time
MW
MVA
MW
MVA
05
0.96
1
-0.96
1
50
0.78
0.8
-0.78
0.8
100
0.56
0.6
-0.56
0.6
160
0.73
0.8
-0.73
0.8
210
0.76
0.8
-0.76
0.8
240
0.79
0.8
-0.79
0.8
280
0.79
0.8
-0.79
0.8
320
0.79
0.8
-0.79
0.8
360
0.79
0.8
-0.79
0.8
Load variation : 2.5 One Line Open
Bus 1 to 2
Bus 2 to 1
Time
MW
MVA
MW
MVA
10
0.84
0.9
-0.84
0.9
30
0.52
0.5
-0.52
0.5
60
0.66
0.7
-0.66
0.7
90
0.86
0.9
-0.86
0.9
130
0.5
0.5
-0.5
0.5
170
15.13
15.3
-15.06
15.3
190
55.95
56.2
-55.00
56.2
240
147.9
147.9
-141.33
147.9
280
48.12
48.4
-47.42
48.4
300
-0.88
0.9
0.88
0.9
330
-0.67
0.7
0.67
0.7
360
-0.47
0.5
0.47
0.5
Both closed Initial ckt + Extra load ( load variation :1.5)
Bus 1 to 2
Bus 2 to 1
Bus 2 to 3
Bus 3-2
Time MW
MVA MW
MVA
MW
MVA MW
MVA
05
0.44
0.4
-0.44
0.4
104.5
107
-101.07
101.1
15
0.28
0.3
-0.28
0.3
106.7
109.3 -103.11
103.1
25
0.24
0.2
-0.24
0.2
108.93 111.8 -105.19
105.2
35
0.46
0.5
-0.46
0.5
111.26 114.3 -107.34
107.3
45
0.5
0.5
-0.5
0.5
113.7
116.9 -109.59
109.6
60
0.48
0.5
-0.48
0.5
116.8
120.3 -112.43
112.4
75*
Ckt breaker Action on Line between Bus 2 and 3
120
0.21
0.2
-0.21
0.2
0
0
0
0
150
0.16
0.2
-0.16
0.2
0
0
0
0
180
0.34
0.3
-0.34
0.3
0
0
0
0
210
0.49
0.5
-0.49
0.5
0
0
0
0
240
0.25
0.3
-.25
0.3
0
0
0
0
280
0.25
0.3
-.25
0.3
0
0
0
0
320
0.25
0.3
-.25
0.3
0
0
0
0
360
0.25
0.3
-.25
0.3
0
0
0
0
Load variation :3 Both lines closed
Bus 1 to 2
Bus 2 to 1
Time
MW
MVA
MW
MVA
05
0.77
0.8
-0.77
0.8
30
1.05
1.1
-1.05
1.1
45
0.95
1.0
-0.95
1.0
60
0.44
0.4
-0.44
0.4
90
0.46
0.5
-0.46
0.5
120
0.90
0.9
-0.90
0.9
135
36.66
36.9
-36.25
36.9
150
75.07
75.3
-73.38
75.3
160
99.21
99.3
-96.25
99.3
180
155.69
155.7
-148.49
155.7
210
241.9
243.1
-224.17
243.1
225
289.78
293.2
-264
293.2
235
322.7
328.6
-290.33
328.60
245
311.55
316.5
-281.5
316.5
270
191.17
191.4
-180.19
191.4
300
75.14
75.3
-73.44
75.3
320
-0.65
0.7
0.65
0.7
343
-0.19
0.2
0.19
0.2
360
-0.34
0.3
0.34
0.3
Both Closed Initial ckt + Extra load (Load Variation : 2.5)
Bus 1 to 2
Bus 2 to 1
Bus 2 to 3
Bus 3-2
Time MW
MVA MW
MVA MW
MVA MW
MVA
05
0.19
0.2
-0.19
0.2
107.11
109.8 -103.49 103.5
15
0.22
0.2
-0.22
0.2
114.09
117.4 -109.96 110
25
0.31
0.3
-0.31
0.3
120.61
124.5 -115.96 116
35
0.3
0.3
-0.3
0.3
129.13
134
-123.74 123.8
45
Circuit Breaker Action
70
0.21
0.2
-0.21
0.2
0
0
0
0
90
0.46
0.5
-0.46
0.5
0
0
0
0
120
0.21
0.2
-0.21
0.2
150
0.17
0.2
-0.17
0.2
170
7.56
7.6
-7.55
7.6
195
32.49 32.7
-32.19
32.7
240
72.35 72.6
-70.77
72.6
280
26.4
26.6
-26.23
26.6
300
0.83
0.8
-0.83
0.8
330
-0.4
0.4
0.4
0.4
360
-0.34 0.4
0.34
0.4
One open one closed Initial ckt + Extra load (Load Variation : 1.5)
Bus 1 to 2
Bus 2 to 1
Bus 2 to 3
Bus 3-2
Time MW
MVA MW
MVA MW
MVA MW
MVA
30
0.47
0.5
-0.47 0.5
109.86
112.9 -106.04
106.1
60
0.77
0.8
-0.77 0.8
116.84
120.4 -112.49
112.5
70
Ckt brk action Bet.n bus 2 n 3
85
0.64
0.6
-0.64 0.6
0
0
0
0
120
0.72
0.7
-0.72 0.7
160
0.52
0.5
-0.52 0.5
200
0.77
0.8
-0.77 0.8
240
0.74
0.8
-0.74 0.8
280
0.74
0.8
-0.74 0.8
320
0.74
0.8
-0.74 0.8
360
0.74
0.8
-0.74 0.8
Initial ckt + Extra load (LV : 2.5)
One open one closed
Bus 1 to
2
Bus 2 to
1
Bus 2 to
3
Bus 3-2
Time
MW
MVA
MW
MVA
MW
MVA
MW
MVA
15
0.91
0.9
-0.91
0.9
113.46
116.7
-109.38
109.4
45
0.11
0.1
-0.11
0.1
135.03
140.7
-129.09
129.1
75
0.81
0.8
-0.81
0.8
155.8
165.0
-147.63
147.6
90
32.66
32.9
-32.34
32.9
165.09
176.4
-155.75
155.8
120
116.69
116.7
-112.6
116.7
187.7
206
-174.97
175
150
212.67
213.2
-199.04
213.2
213.2
244.4
-195.28
195.3
160
Blackout…..
Initial ckt + Extra load (LV : 3)
One open one closed
Bus 1 to
2
Bus 2 to
1
Bus 2 to
3
Bus 3-2
Time
MW
MVA
MW
MVA
MW
MVA
MW
MVA
10
0.45
0.5
-0.45
0.5
113.91
117.2
-109.79
109.8
25
0.37
0.4
-0.37
0.4
125.54
130
-120.47
120.5
100
0.29
0.3
-0.29
0.3
0
0
0
0
125
9.57
9.7
-9.54
9.7
165
56.51
56.7
-55.54
56.7
205
112.31
112.4
-108.52
112.4
10
0
0
0
0
109.9
112.8
-106.1
106.1
25
0.95
1
-0.95
1
126.69
131.3
-121.51
121.5
50
1.06
1.1
-1.06
1.1
0
0
0
0
85
0.8
0.8
-0.8
0.8
0
0
0
0
125
19.95
20.1
-19.83
20.1
170
134.15
134.2
-128.75
134.2
Inferences1. There are two types of buses in the first part of the experiment. Bus 1 is the Slack bus .Bus 2 is the PV bus. However, during analysis,
we treat the slack bus as PQ bus absorbing negative real power (as discussed in the power systems minor 2). The second part has three buses, Bus 2 is still the PV bus, although now Bus 1 is the slack bus, and Bus 3 is the load bus.
2. The Slack bused take are of any losses incurred on the transmission lines, apart from fulfilling the shortfall by the PV bus. The PV bus
compensate the increasing demand for power .Although the power from the Slack bus could be used, but has to be transmitted fr om another generator leading to more losses and increased economic costs.
3. In the first part, the given experimental setup is designed for the 1.5 load variation, in which the system runs under normal mode ,
for most of the time , drawing bare minimum power from the Slack bus. This is attributed to transients on the network and slo w operation of AGC. The network also adjusts for the load variation case 2.5. However, when there is a high power demand , as in the load variation 3 case, the sensor trigger an alert mode initially and then escalating to emergency, although no contingency mode is detected. (No circuit action is detected.)
4. When the third load is connected, the Transmission line between bus 2 and bus 3 is already overloaded triggering an emergency mode , and finally due to high power transfer on the line. However, the system blackout is not prevalent in the load variation 1.5 case. However, in case ,of load variation 2.5 and 3 , there is a system wide blackout to high power (150 MVA ) on both the li nes , causing circuit breaker action.
5. Contingency Mode was prevalent on the two wire, and the three wire case one of the lines between bus 1 and bus 2 was disconnected.
6. Losses on the power lines are proportional to amount of power flowing through it.
Remedies
As stated formerly, the given circuit was designed for the 1.5 load variation cases , and barely withstands the 2.5 load variation Therefore proper surveying should be conducted for current and future trends in the network.
The power transfer capability of the transmission systems is limited by current (thermal) related constraints, voltage related constraints and operating related constraints . The strategies employed in dealing with these are:
a. Voltage Uprating:Transmission systems are typically submitted to two voltage constraints: a maximum operating voltage equal to 105% of the nominal voltage and a minimum operating voltage equal to 95% of the nominal voltage. It is possible to increase the power transfer capability of a transmission system by increasing the operating voltage
within a voltage class, by controlling reactive power flows and consequently reducing voltage drops, and by increasing the operating voltage of its transmission lines and substation equipment. This is called Voltage Uprating.This kind of uprating can be a good option when: the line loading is limited by voltage drop or stability considerations; the line has margins in terms of electrical clearances; the uprating can be done with minimal line modifications or it will be applied to several circuits simultaneously or the line design criteria can be relaxed. Some of the techniques for voltage uprating are described below : 1. Adding insulator units to transmission line insulator strings
2. Keeping appropriate conductor to ground clearances while increasing transmission line voltage by re –tensioning the string, or by performing sag adjustments.
3. Bundling the original line conductor with another one. or replacing the line conductor by a bigger one, to assure a good corona performance
4. Converting HVAC lines to HVDC lines.
b. Thermal Uprating: It is possible to increase the power transfer capability of a transmission system by increasing the current carrying capacity of its transmission lines and substation equipment. This is called Thermal Uprating. This kind of uprating can be a good option when the line loading is limited by thermal constraints and the line has margin in terms of maximum
allowable conductor temperature. Some effective techniques are as follows: 1. Performing Dynamic Thermal Rating Monitoring.
2. Bundling the original line conductor with another one, or replacing the line conductor by a more conductive me, to increase the line current-carrying capacity.
However , reliance only on circuit breakers isn’t enough to transmission line tripping of a single power line will eventually load the other ( maybe already overloaded ) power lines, into a cascading effect leading to a system wide collapse. In such a case, we need to increase the number of transmission lines , which probably is an expensive and not possible in case of underground power lines . One solution is to increase the capacity of generator near the loading areas, so that less power flows on the transmission lines as shown in the image. This also reduces the economic cost of
the system, since we use the cheaper locally generated power.
Although Series capacitive compensators are used to increase the transmittable active power over a given line but they are unable to control the reactive power flowing, and thus the proper load balancing of the line. With a Inter Line Power Flow Controller (IPFC), it is possible to equalize both active and reactive power flow between the lines, reduce the burden of overloaded lines by active power transfer and increase the effectiveness of the overall compensating system for dynamic disturbances
A Basic IPFC can be modeled as shown above. Here SSSC are the Static Synchronous Series Compensator .
