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1. Mitigation of voltage collapse at Davanagere Receiving Station
V. Chayapathy, G S Anitha
Associate professor, RVCE, Bangalore
Introduction
In transmission and distribution lines, voltage instability may be due to overloading, high
reactive power and low operating power factor. It is possible to control over loading to some
extent by creating a general awareness among public about the scarcity of power.
Reactive power and power factor are interrelated to each other. In electric power systems
real power does useful work while reactive power supports the voltages that must be maintained
for the reliability of the system. Since most of the loads are inductive in nature by default reactive
power requirements will be high at the load side. Reactive power generation at generating end will
increase per unit cost of generation and decreases the reliability of the system because at generating
end generation of excess reactive power that is not utilized for any purpose makes the power
system inefficient. However it is better if the minimum reactive power required by the system is
generated at generation point and the excess requirements are injected at load side [33, 34, 35].
At present there are high voltage capacitor banks (capacitors arranged either in series or
parallel at Davanagere receiving station) to compensate reactive power and power factor. But it is
seen that this equipment will not work efficiently at all conditions of load variations. As the load
increases capacitor banks become inefficient in compensating reactive power and power factor.
The work carried out at Davanagere receiving station aims at improving the voltage
magnitude in a permissible safe limit (0.9 to 1.1 pu IEEE standards) with the help of FACTS
devices. Since both SVC and STATCOM have capacitance and inductive reactance as its
components, they both can regulate the voltage such that when voltages on the bus goes down it
injects reactive power and increases the voltage to the required level.
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2. Transmission Line Details
Table 1 Transmission line data for different voltage levels and conductors
Sl. No.
Name of the
Conductor
Voltage
level in
KV
Current
rating
In Amps
R+jX
In ohm
Current at
Ambient
Temperature in
Amps
30°ċ 50°ċ
01 Coyote 66 487 0.135+j0.104 387 487
02 Coyote 11 367 0.0248+j0.0337 215 367
03 Drake 220 900 0.244+j0.243 745 900
04 Drake 66 487 0.135+j0.104 400 487
05 Drake 11 387 0.038+j0.0260 325 387
Transmission line parameters of different conductors which are used at sub-station for bus
bar connection and also the transmission lines are specified .as shown in Table 4.1
Capacitor Bank Details
Rated current : 69.24amps
Quantity : 484 KVAR
Rated voltage : 13.98KV
Temperature : 50ċ (ambient)
Fuse protection : Internal
Rated capacitance : 31.03μf
Frequency : 50Hz
Insulation level : 28/75
Standard : IS: 19325
Conductance and susceptence: 0.001, 0.004
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3.  At all substations in each phase there are two capacitor cells and for three phases there are
six cells. Each capacitor cell has a capacity of 484 MVAR and the capacity of each capacitor
bank at the substation is (484 x 6=2.904 MVAR). At each substation there are two capacitor
banks of identical rating. Total capacitor rating is 2*2.904 =5.808 MVAR
Ratings of SVC
 Rated system voltage 220 KV/66 KV/11 KV ± 5%, 50 Hz
 Rated power 0-50 MVAR
 Capacitive 0-50 MVAR
 Inductive 0.60 VAR and
Maximum voltage variation at the 400 KV Bus bar is +/- 0.4 %
Analysis of the Systems on the Load side:
Experiments were conducted at Punabhgatta, Chikkajajaur and Davanagere Power Stations
and the results are shown in Tables 4.3, 4.5 and 4.7 respectively with and without connection of
capacitor banks.
Test System-I - Punabhgatta (8 Bus System)
There is one incoming line at 66 KV from Davanagere followed by installation of two
transformers of 12.5 and 8 MVA respectively. There are seven loads and a capacitor bank which is
connected as shunt to the loads. Table 4.2 and 4.3 shown are load flow details and capacitor loading
details conducted at site respectively.
Table 4.2: Load Flow Details of 66/11 KV Sub Station Punabghatta
Bus Nos. Description Load in MW MVAR Load in Amps
1
66 KV Incoming from
Davanagere
10.6 4.95 106
2 Hiremegalgere 2.0 0.46 120
3 Kanchikere 2.5 0.575 150
4 Kyarekatte 3.10 0.713 186
5 Laxmipura 0.80 0.18 48
6 Punabgatta 2.5 0.575 150
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4. 7 Hosakote 2.8 0.644 168
8 Arasikere 1.6 0.368 96
Table 4.3: Loading operations at 66/11KV Substation Punabghatta (Conducted at Site)
Description
Before charging of
Capacitor Banks
After
Charging of
Capacitor Banks
Compensation
Bank 1
F1 and F2
350 amps 290 amps 62 amps
5.86MW 4.80 MW 1.03 MW
Bank2
F5 and F6
190 amps 160 amps 29.16 amps
3.16 MW 2.67 MW 0.49 MW
Total compensation from the shunt capacitor bank of 2.904 MVAR is 0.942 MVAR
The total reactive power compensation at all the receiving stations are evaluated at a load
power factor of 0.85 lagging.
Test System-II - Chikjajur (11 Bus System)
There are three incoming lines at 66KV from Davanagere receiving stations and
Independent wind turbine generators followed by installation of two transformers of 12.5 and 6.3
MVA respectively. There are eight loads and two capacitor banks which are connected as shunt to
the loads. Table 4.4 and 4.5 shown are load flow details and capacitor loading details conducted at
site respectively.
Table : Load Flow Details of 66/11 KV Substation Chickjajur
Designated
Bus Nos.
Description
Load in
MW
MVAR
Load in
Amps
1
66 KV Incoming from
Davanagere
10.3 4.970 103
2 Wind 1 (IPP) 8.0 3.66 80
3 Wind 2 (IPP) 6.0 2.77 60
4 Kadur 1.7 0.34 102
5 Hirekandwadi 3.5 0.50 210
6 BevinaDurga 3.0 0.40 180
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5. 7 Kothehal 1.2 0.30 72
8 Chickjajur 6.1 1.8 366
9 Chikkandwadi 4.0 0.9 240
10 Gangiganur 0.6 0.1 36
11 Water house 0.1 0.001 06
Table 5: Loading operations at Chickjajur 66/11KV Substation Chickjajur(Conducted at Site)
Description
Before charging of
Capacitor Banks
After charging of
Capacitor Banks
Compensation
Bank-1
F1 and F2
102+218=320 Amps
5.34MW
Reduced to 270 Amps
4.5 MW
0.84MW
Bank-2
F6 and F7
202+38=240 Amps
4.0MW
3.2 MW 0.8MW
Total compensation from the shunt capacitor bank of 2.904 MVAR is 1.02 MVAR
Test System-III Davanagere (15 Bus System)
There are five incoming lines at 220 KV, in that three from Guttur (400 KV receiving
station) and two from Shimoga (220 KV Mahatma Ghandi receiving station) followed by
installation of three winding transformers of two 100 and 60 MVArespectively. There are ten loads
at 66 KV and two capacitor banks which are connected as shunt to the loads. Table 4.6 and 4.7
shown are load flow details and capacitor loading details conducted at site respectively.
Table 6: Load Flow Details of 220/66/11 KV Receiving Substation Davanagere.
Bus
No.
Description Load in
MW
MVAR Load in
Amps
1 Incoming from 400KV Guttur-1 131 42.75 327.5
2 Incoming from 400KV Guttur-2 73 23.98 182.5
3 Incoming from 400KV Guttur-3 123 59.419 307.5
4 Incoming from Receiving Station Shimoga-1 131 42.75 327.5
5 Incoming from Receiving Station Shimoga-2 105.6 34.68 564
6 66KV Sokke Line 16.0 12.62 160
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6. 7 66KV Davanagere Line 11.0 6.0 110
8 66KV Avargere Line 13.5 7.0 135
9 66KV Chitrdurga Line 11.0 6.0 110
10 66KV Industrial Line 21.0 18.2 212
11 66KV Harihara Line 20.0 6.00 200
12 66KV Kukwada Line 4.0 4.10 130
13 66KV Yaragunta Line 11.0 6.0 110
14 66KV Shimoga Line 26.0 16.0 260
15 66KV Harappanahalli Line 10.5 2.60 105
Table 7: Capacitor Bank loading operations at 220/66/11KV Receiving Substation Davanagere
(Conducted at Site)
Description Before charging of
Capacitor Banks
After charging of
Capacitor Banks
Compensation
66kv
Feeders
F1-F10
888.9amps 728.9amps 152.6 amps
88.89MW 72.89 MW 15.26MW
Total compensation from the shunt capacitor bank of 2.904 MVAR is 9.46 MVAR
Summary
It is seen that when experiments were conducted at the load sites of Punabhgatta, Chickjajur
and Davanagere receiving station a total reactive power compensation of 0.942, 1.02 and 9.46
MVAR respectively was possible at a power factor of 0.85 lag after using the capacitor banks.
FACTS devices are not used at present at the above mentioned power grids. The experiments
conducted at the site is an unique feature of this thesis.
In the discussions which fallow simulations were done for the above powers systems up to
125% over loading and the reactive power relief on the generator side is evaluated as shown.
Analysis on the Load Side of the Power System.
Test System-I Punabhgatta (8-Bus System)
Load flow simulation tests were conducted at nominal load, 125% of nominal load and for
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7. each case again four sets of results were obtained that is without any compensation, with shunt
capacitors, with SVC and with STATCOMS. All the results are analyzed and the analysis is given
in Table 4.9.
It is assumed that at nominal load conditions system will be healthy and it is not necessary
to use any FACTS devices. It is seen that shunt capacitors are efficient in controlling power factor
and reactive power generation.
Output comparison for healthy Load
Table 8 Variation of Load Voltages.
Bus No
Without Capacitor Banks With Capacitor Banks
Bus
Voltages (pu)
Gen P.F
Bus
Voltages (pu)
Gen P.F
01 1.0000 0.978 1.0000 0.993
02 0.9910 0.978 1.0012 0.993
03 0.9992 0.978 1.0341 0.993
04 1.0178 0.978 1.0215 0.993
05 1.0492 0.978 1.0503 0.993
06 1.0452 0.978 1.0467 0.993
07 1.0509 0.978 1.0517 0.993
08 1.0447 0.978 1.0463 0.993
MVAR gen 5.056 2.860
At Bus 8 of the system with nominal load and without any compensation, variations are as
shown in Table 4.8 and the results are summarized. At Bus 2 and Bus 3 the voltages are reduced,
power factor is 0.978 and reactive power generated is 5.056 MVAR.
With shunt power capacitors of rating 2.904 MVAR, it is seen that voltages at Bus 2 and
Bus 3 the voltages are brought to unity, power factor is increased to 0.993 and reactive power
generated is 2.86 MVAR.
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8. Output comparison for 125% of healthy Load
Table 9 Variation of Load Voltages
Bus
No
Without
Compensation
With Shunt
Capacitors
With SVC With STATCOM
Bus
Voltage (pu)
Gen
P.F
Bus
Voltage (pu)
Gen
PF
Bus
Voltage (pu)
Gen
P.F
Bus
Voltage (pu)
Gen
P.F
01 1.0000 0.976 1.0000 0.989 1.0000 0.994 1.0000 1.000
02 0.9910 0.976 0.9910 0.989 0.9910 0.994 0.9910 1.000
03 0.9992 0.976 0.9992 0.989 0.9992 0.994 0.9992 1.000
04 1.0178 0.976 1.0178 0.989 1.0178 0.994 1.0178 1.000
05 1.0492 0.976 1.0492 0.989 1.0492 0.994 1.0492 1.000
06 1.0452 0.976 1.0452 0.989 1.0452 0.994 1.0452 1.000
07 1.0509 0.976 1.0509 0.989 1.0509 0.994 1.0509 1.000
08 1.0447 0.976 1.0447 0.989 1.0447 0.994 1.0447 1.000
Mvar
Gen
6.321 3.542 1.647 0.827
Without the connection of any capacitor it is seen that at Bus 2 and Bus 3 there is a sag in
Voltage from 1.0 p,u to 0.9 p.u . This sag is considerable since the Base Voltage is in KV.
Summary:
As highlighted earlier at Punabhgatta power grid there is one incoming line at 66 KV from
Davanagere followed by installation two transformers of 12.5 and 8 MVA respectively. There are
seven loads and a capacitor bank which is connected as shunt to the loads. As seen from Tables 4.8
to 4.9 as the loads on the system is increased to 125% the amount of reactive power generated at
the generator end predominantly reduces as the FACTS devices are used. Of the various FACTS
devices used STATCOM reduces the reactive power generated at the generator side to a least value
as reactive power supplied by the STATCOM is high. It is seen that MVAR generation reduces
with reactive power compensation.
Test System-II Chikjajur (11-Bus System)
Output comparison for healthy load
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9. Table 10 Variation of Load Voltages
Bus No
Without Capacitor Banks With Capacitor Banks
Bus
Voltages (pu)
Gen P.F
Bus
Voltages (pu)
Gen P.F
01 1.0000 0.974 1.000∟-1.4 0.981
02 1.0105 0.974 1.0105 0.981
03 1.0020 0.974 1.0020 0.981
04 1.0470 0.974 1.0472 0.981
05 1.0495 0.974 1.0497 0.981
06 1.0382 0.974 1.0384 0.981
07 1.0312 0.974 1.0313 0.981
08 1.0261 0.974 1.0262 0.981
09 1.0308 0.974 1.0309 0.981
10 1.0417 0.974 1.0418 0.981
11 1.0535 0.974 1.0536 0.981
MVAR
gen
4.740 4.421
At Chickajajur receiving station there is no voltage sag at any of the buses as generation
capacity is sufficient at this receiving station.
Output comparison for 125% of healthy load
Table 11 Variation of Load Voltages
Bus No
Without
Compensation
With Shunt
Capacitors With SVC With STATCOM
Bus
Voltage (pu)
Gen
P.F
Bus
Voltage (pu)
Gen
P.F
Bus
Voltage (pu)
Gen
P.F
Bus
Voltage (pu)
Gen
P.F
01 1.0000 0.973 1.0000 0.978 1.0000 0.996 1.0000 1.000
02 1.0068 0.973 1.0069 0.978 1.0069 0.996 1.0070 1.000
03 1.0000 0.973 1.0000 0.978 1.0000 0.996 1.0007 1.000
04 1.0455 0.973 1.0457 0.978 1.0574 0.996 1.0574 1.000
05 1.0486 0.973 1.0488 0.978 1.0534 0.996 1.0534 1.000
06 1.0330 0.973 1.0331 0.978 1.0366 0.996 1.0367 1.000
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10. 07 1.0228 0.973 1.0229 0.978 1.0252 0.996 1.0256 1.000
08 1.0149 0.973 1.0150 0.978 1.0161 0.996 1.0164 1.000
09 1.0195 0.973 1.0196 0.978 1.0198 0.996 1.0201 1.000
10 1.0319 0.973 1.0320 0.978 1.0322 0.996 1.0325 1.000
11 1.0455 0.973 1.0455 0.978 1.0457 0.996 1.0458 1.000
Mvar
gen 6.116 5.898 1.834 0.993
Even at 125% over load at Chickajajur receiving station there is no voltage sag at any of
the buses as sufficient generation supply is there at this Receiving Station.
Summary:
There are three incoming lines at 66 KV from Davanagere and Wind energy power plant is
installed at Chickjajur followed by installation of two transformers of 12.5 and 6.3 MVA
respectively. There are eight loads and two capacitor banks which are connected as shunt to the
loads. Table 4.4 and 4.5 shows load flow details.
As seen in Table 4.13 as the loads on the system is increased to 125% the amount of
reactive power generated at the generator end predominantly reduces as the FACTS devices are
used. Of the various FACTS devices used STATCOM reduces the reactive power generated at the
generator side to a least value as reactive power supplied by the STATCOM is high.
Test System-III Davanagere (15-Bus System)
Output comparison for healthy load
Table 12 Variation of Load Voltages
Bus Nos.
Without Shunt Capacitors With Shunt Capacitors
Bus
Voltage (pu)
Gen
P.F
Bus
Voltage (pu)
Gen
P.F
01 1.0000 0.862 1.0000 0.866
02 1.0493 0.862 1.0493 0.866
03 1.0000 0.862 1.0000 0.866
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11. 04 1.0517 0.862 1.0517 0.866
05 1.0474 0.862 1.0475 0.866
06 0.8713 0.862 0.8715 0.866
07 0.8391 0.862 0.8395 0.866
08 0.8416 0.862 0.8421 0.866
09 0.8741 0.862 0.8744 0.866
10 0.9655 0.862 0.9657 0.866
11 0.9394 0.862 0.9395 0.866
12 0.9198 0.862 0.9200 0.866
13 0.9247 0.862 0.9249 0.866
14 0.9534 0.862 0.9536 0.866
15 1.0376 0.862 1.0377 0.866
Mvar
gen
154.817 152.234
Output comparison for 125% of healthy load
Table 13 Variation of Load Voltages
Bus
No
Without
Compensation
With Shunt
Capacitors With SVC With STATCOM
Bus
Voltage (pu)
Gen
P.F
Bus
Voltage (pu)
Gen
P.F
Bus
Voltage (pu)
Gen
P.F
Bus
Voltage (pu)
Gen
P.F
01 1.0000 0.859 1.0000 0.863 1.000 0.900 1.000 0.930
02 1.0493 0.859 1.0493 0.863 1.009 0.900 1.009 0.930
03 1.0000 0.859 1.0000 0.863 1.0805 0.900 1.0805 0.930
04 1.0517 0.859 1.0517 0.863 1.2241 0.900 1.2241 0.930
05 1.0475 0.859 1.0475 0.863 1.1240 0.900 1.1240 0.930
06 0.8695 0.859 0.8715 0.863 0.9232 0.900 0.9638 0.930
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12. 07 0.8353 0.859 0.8395 0.863 0.8893 0.900 0.9243 0.930
08 0.8394 0.859 0.8421 0.863 0.8943 0.900 0.9351 0.930
09 0.8697 0.859 0.8744 0.863 0.9235 0.900 0.9643 0.930
10 0.9602 0.859 0.9657 0.863 1.0171 0.900 1.0241 0.930
11 0.9347 0.859 0.9395 0.863 0.9841 0.900 1.0013 0.930
12 0.9154 0.859 0.9200 0.863 0.9742 0.900 0.9993 0.930
13 0.9201 0.859 0.9249 0.863 0.9620 0.900 0.9879 0.930
14 0.9503 0.859 0.9536 0.863 0.9921 0.900 1.0136 0.930
15 1.0342 0.859 1.0377 0.863 1.0398 0.900 1.0402 0.930
Mvar
gen 209.234 207.240 108.837 92.362
There is voltage sag at all the buses starting from bus 6 to bus 14 as this receiving station
has heavy loads as compared to Chickjajur and Punabhghatta receiving stations.
Summary:
There are five incoming lines at 220 KV, three from Guttur (400 KV receiving station) and
two from Shimoga (220 KV Mahatma Gandhi receiving station) followed by installation of three
transformers out of which two are 100 MVA and one transformer of 60 MVA. There are ten loads
at 66 KV and two capacitor banks which are connected as shunt to the loads. Table 4.6 and 4.7
shows load flow details and capacitor loading details conducted at site respectively.
The loads on the system are increased to 125%, the amount of reactive power generated at
the generator end predominantly reduces as the FACTS devices are used. Of the various FACTS
devices used STATCOM reduces the reactive power generated at the generator side to a least value
as reactive power supplied by the STATCOM is high.
The contribution of this work is a detailed analysis of effect of loading the system. The
response of the system to the increase in load is analysed.
[1] Renato B. L. Guedes, Luis F. C. Alberto, Newton G. Bretas, Power System Low-Voltage
Solutions Using an Auxiliary Gradient System for voltage collapse Purposes , IEEE
Transactions on Power Systems, Vol. 20, NO. 3, August 2005, Page No. 1528-1537.
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