1. The document discusses the Southern Grid which transmits power across five states in Southern India. 2. It has an installed capacity of 50,164 MW from various sources including thermal, hydro, gas etc. distributed across states. 3. The grid ensures stability through interconnected regional grids using HVDC links and maintains frequency, voltage levels through mechanisms like AGC, reactive power support etc.

1. Know about Southern Grid
M. G. Morshad , ADGM / Electrical
TPS II ( 7 x 210MW) NLC India Ltd

2. Indian Power Grid
1. Electrical power system consist of – Generation, transmission , Distribution
& Consumption.
2. The transmission network (interconnections) that transmits the electrical
power generated by various generating station to the distribution point for
the customers is know as power grid.
3. In India there are five regional power grids – Northern Region
( NR), Western Region (WR), Eastern Region (ER), Southern Region (SR) &
North East Region (NER)
4. For proper distribution of power and grid stability all regional grids are
interconnected through HVDC links
Standard Generating
Voltage ( KV)
10.5 KV
15.75 KV
21 KV
26 KV
Standard Transmission
Voltage ( KV)
110 KV
132 KV
220 KV
400 KV
765 KV
Standard Distribution
Voltage ( KV)
11 KV
33 KV
66 KV

13. Inter Grid connection through HVDC link

14. KHAMMAM
VIJAYAWADA
N’SAGAR
VISAKHAPATNAM
HYDERABAD
RAICHUR
GOOTY
HOODY
SALEM
TRICHUR
MADURAI
TRICHY
SPBDR
NLC II
CUDDAPAH
DVNGRE(KN)
KAIGA
RAMAGUNDAM
CHANDRAPUR
PONDICHERY
BANGALORE
SIRSI
MUNIRABAD
KOLAR
PALLOM
KAYANKULAM
EDAMON
TALCHER
HOSUR
KRNL(AP)
NARENDRA
TRIVANDRUM
HIRIYUR
NLC -1 EXP.
NELLORE
JEYPORE
NELAMANGALA
KOZIKODE
MYSORE
ARASUR
PUGALUR
MELKTYR
ALMTI(TN)
UDUMALPET
+ 500kV HVDC BIPOLE LINE 2738 ckm
400kV LINES EXISTING 8360 ckm
400kV LINES UNDER CONSTRUCTION 2400 ckm
400kV LINES PROPOSED 4000 ckm
220kV LINES EXISTING 366 ckm
OTHER UTILITIES LINE
+ 500kV HVDC BIPOLE TERMINAL AT KOLAR 1
+ 500kV HVDC BACK TO BACK AT VIZAG 1
LEGEND
NLC II EXP
WARANGAL
SRSLM(AP)
SOUTHERN REGION GRID MAP
AS ON SEP 2004
178
200
189
150
317
279
242
155
267
308
258
61
221
181
151
341
189
78
47
130
127
130
172
14
164
178
182
BAHOOR
53
126
6951
178
97 211
302
172
115
1369
174
110 158
160
98
210
10
254
50
215
136
50
43
30
225
140
217
43
78
3
5
TALAGUPPA
HASSAN
COCHIN
TIRUNELVELI
KUDAKULAM
APP
KARRIKUDI
Southern Grid – salient points
Beneficiary
States
1. Andhra Pradesh,
2. Karnataka,
3. Kerala
4. Tamil Nadu
5. Pondicherry
Total area 6,51,000 sq .km
Installed Capacity 50,164 MW
Thermal – Hydro
Ratio
67: 33
Transmission
Network 400 /
220 KV
37,500 Kms
Generators –
(Thermal/Hydro/
Gas/IPP
422 Nos
Peak / off peak
Load Demands
34000 MW /
13000 MW
Inter Grid HVDC
Links
1. SR – ER (Bi pole)
2. SR – ER ( B – B)
3. SR – WR (B – B)

15. 0.00%
5.00%
10.00%
15.00%
20.00%
25.00%
30.00%
35.00%
40.00% Industry 37.25%
Agriculture 30.10%
Domestic 22.51%
Commercial 6.34%
Others 3.80%
Southern Grid – Load profile

16. Southern Grid – Installed capacity
MW %
Tamil Nadu 17,222 32%
Andhra Pradesh 14,057 26%
Karnataka 11,603 21%
Kerala 2,818 5 %
Central Sector (ISGS) 8,810 16 %
Total Installed capacity ( As on 30.1.2013) 54, 510 MW
32%
26%
21%
5% 16% Tamil Nadu
Andhra Pradesh
Karnataka
Kerala
Central Sector (ISGS)

17. Total Thermal : 4420 MW
1.Ennore TPS : 450 MW
2.North Chennai TPS : 630 MW
3. Tutucorin TPS : 1050 MW
4. Mettur TPS : 1440 MW
5. Neyveli-I (IPP) : 600 MW
6. ST-CMS : 250 MW
Total Hydro : 2224 MW
1. Kadamparai (G) : 400 MW
2. Kadamparai (P) : 400 MW
3. Other Hydro : 1824 MW
Total Gas/Naptha/Diesel : 2732 MW
1. Basin Bridge : 120 MW
2. Kovilkalappal : 108 MW
3. Kuttalam : 101MW
4. Valattur(Stg 1&2) : 187 MW
5. Samalpatty : 106 MW
6. P P Nallur : 331 MW
7. Madurai Power CL : 106 MW
8. GMR Vasavi : 196 MW
9. Other Gas/Naptha/Diesel : 1477 MW
1. Wind : 7040 MW
2. Others : 806 MW
INSTALLED CAPACITY - TAMIL NADU: 17,222 MW
INSTALLED CAPACITY - CENTRAL SECTOR (ISGS) : 8810 MW
1. Ramagundam,NTPC : 2600 MW
2. Neyveli TPS II : 1470 MW
3. Neyveli TPS I (EXP) : 420 MW
4. Madras APS : 440 MW
5. Kaiga STGI : 440 MW
6. Kaiga Unit 3 & 4 : 440 MW
7. Talcher II, NTPC : 2000 MW
8. Simhadri II, NTPC : 1000 MW

18. INSTALLED CAPACITY - ANDHRA PRADESH: 14,057 MW
Total Thermal 6301 MW
1. Vijayawada TPS : 1760 MW
2. Kothagudam TPS : 1720 MW
3. Rayalaseema TPS : 1050 MW
4. Simhadri (IPP) : 1000 MW
5. Kakatiya TPP : 500 MW
6.Other Thermal* : 271 MW
Total Gas/Naptha/Diesel : 3073 MW
1. Vijjeswaram Gas : 272 MW
2. Reliance Energy Ltd. : 220 MW
3. Jegrupadu : 217 MW
4. Spectrum : 208 MW
5. LANCO : 351MW
6. Vemegiri (GMR) : 370 MW
7. Jegrupadu Ext. : 220 MW
8. Konaseema : 445 MW
9. Gauthami : 464 MW
10. GMR(BRG) : 237 MW
11. Other Gas/Naptha/Diesel : 69 MW
Total Hydro: 3935 MW
1. N'Sagar : 816 MW
2. Srisailam LB (Gen) : 900 MW
3. Srisailam RB : 770 MW
4. Srisailam LB (Pump) : 900 MW
5. Lower Sileru : 460 MW
6. Upper Sileru : 240 MW
7. Other Hydro : 749 MW
1. Wind : 216 MW
2. Others : 532 MW

19. INSTALLED CAPACITY - KARNATAKA: 11,603 MW
Total Thermal : 3320 MW
1. Raichur TPS : 1720 MW
2. Bellary TPS : 1000 MW
3. UPCL(IPP) : 600 MW
Total Hydro : 4148 MW
1. Sharavathi : 1035 MW
2. Nagjher : 885 MW
3. Varahi : 460 MW
4. Other Hydro : 1768 MW
Total Gas/Naptha/Diesel : 1625 MW
1. Yelehanka Diesel : 128 MW
2. Jindal : 1390 MW
3. Other Gas/Naptha/Diesel : 107 MW
1. Wind : 1818 MW
2. Others : 692 MW
INSTALLED CAPACITY - KERALA : 2818 MW
Total Hydro : 1989 MW
1. Iddukki :780 MW
2. Sabarigiri : 280 MW
3. Lower Periyar : 180 MW
4. Other Hydro : 749 MW
Total Gas/Naptha/Diesel : 774 MW
1. Kayamkulam : 360 MW
2. Reliance Energy Ltd : 157 MW
3. Brahmapuram DPP : 107 MW
4. Kozhikode DPP : 128 MW
5. Other Gas/Naptha/Diesel : 22 MW1. Wind : 35 MW
2. Others : 20 MW

20. Typical SR Demand with Frequency
17000
18000
19000
20000
21000
22000
23000 12:00AM
2:00AM
4:00AM
6:00AM
8:00AM
10:00AM
12:00PM
2:00PM
4:00PM
6:00PM
8:00PM
10:00PM
Time (In Hrs)
Demand(InMW)
48.5
49
49.5
50
50.5
Demand Frequency

21. DailyConsumption of Southern Region for 2003-07
280
330
380
430
480
530
580
Apr
May
Jun
Jul
Aug
Sep
Nov
Dec
Jan
Feb
Mar
Months ---->
Consumption(InMUs)---->
2003-04 2004-05 2005-06 2006-07

22. Generation cluster
around Ramagundam
(2600 MW)
Generation cluster
around Neyveli
(2490 MW)
Generation cluster
around Simhadri
(1000 MW)
Southern zone
( Karnataka, Tamil Nadu , Kerala)
(High Load demand)
Northern zone
(Andhara Pradesh)
(Low Load demand)
Southern Grid – Inter Grid connection

23. Southern Grid – HVDC Link ( Asynchronous )
HVDC
LINK
TYPE
CAPACITY
(MW)
PURPOSE
Talcher (ER) -
Kolar (SR)
Bi polar
(1367 Km
line)
2500
To draw power from eastern grid to
southern grid
Jeypore (ER ) -
Gazuwaka (SR)
Back to
back
1000
Bidirectional power flow between
Eastern & Southern grids for
exchanging surplus power
Chandrapur (WR ) -
Bhadrawati (SR)
Back to
back
1000
Bidirectional power flow between
Western & southern grids for
exchanging surplus power

24. Grid Stability criteria
1. Frequency Stability
a) Short-term frequency stability
b) Long-term frequency stability
2.Voltage Stability
a) Large-disturbance Voltage Stability
b) Small-disturbance Voltage Stability
3. Load Angle Stability
a) Small-disturbance Angle Stability
b) Large-disturbance Angle Stability (Transient Stability)

25. Grid stability – Frequency
Frequency instability occurs due to mismatch between load
demand and generation
a. High Frequency : High generation but low load demand due to
improper load demand forecasting
b. Low frequency : High load demand but low generation due to non
availability of generator / sudden tripping of generator / HVDC link
supplying power to the grid.
Frequency stability is ensured by taking following steps
a. Implementing ABT ( Declaration of generator availability based on
load forecasting & imposing of strict UI mechanism)
b. Running generation unit with free governing mode so that unit can
automatically increase / decrease generation depending on the grid
frequency.
c. Installing protection for automatic under frequency load shedding
and islanding

26. Grid frequency band and MW
correction in FGMO
Frequency ( In Hz) MW Correction (In MW)
49.6 +30.0
49.7 +25.2
49.8 +16.8
49.9 + 8.4
50.0 0.0
50.1 -8.4
50.2 -16.8
50.3 -25.2
50.4 -30.0

27. Grid stability – Low Voltage
Voltage Instability in grid causes mainly due to lack of adequate
reactive power support . It could be due to
(a) Sudden change in the network topology redirecting the power flows.
(b) Gradual increase of power demand in such a way that VAR requirement
of some of the buses may not be met locally.
Voltage collapse getting initiated from a node/set of nodes could
result Into wide area voltage instability and can be classified as
a. Transient (varying from 1 to 3 sec.)
Transient voltage instability remedial measures require fast and automatic
actions viz. power system stabilizers and static VAR Compensators
b. Steady-state (varying from tens of seconds to several minutes).
Steady-state voltage instability which occurs mainly due to gradual VAR deficit
can be controlled to a large extent by the timely and prompt intervention of the
system operator and utilities.

28. Basic function of power System Stabilizer ( PSS) provided in
excitation system (I)
Sudden changes in load cause grid to oscillate at very low frequency.
Since rotor inertia acts as weight connected to the grid through spring
force - this frequency induced in the machine and causes low
frequency (o.2 to 2.5 Hz) power oscillation.
This phenomenon is known as Dynamic Oscillations and it gets
damped within one second by the inherent damping forces, friction and
windage force present in the system.
The power oscillation will be stronger and may cause the machine to
go out of steps when machine is
a. Delivering high active and reactive power to the grid
b. Connected with tie line having high reactance
c. Having high AVR gain and low time constant

29. Basic function of power System Stabilizer ( PSS)
provided in excitation system (II)
This phenomenon of power oscillation in machine caused by minor
disturbance in grid is known as dynamic instability or oscillatory instability.
It can be damped and improved the stability of the grid & machine by
introducing power system stabilizer (PSS) or slip stabilized for all large
size machine connected to large network.
Power swing equation for any machine connected to the grid is
MA - ME = H (d2δ/dt2)
Where -
MA = Mechanical torque delivered by prime mover
ME = Electrical torque delivered by generator
H (d2δ/dt2) = Acceleration
H = Inertia constant of the rotor (Stored kinetic energy in MJ at
synchronous speed / Machine rating in MVA)
δ = Load angle

30. S
N
R
DC source for
excitation current
Y
B
Stator axis
Rotor axis
Load
angle (δ)
Synchronous speed of
the rotor at operating
frequency
Oscillatory motion of rotor due to
power swing
Damping force

31. Basic function of power System Stabilizer ( PSS)
provided in excitation system (III)
Power swing due to incremental changes in ME causes oscillatory motion in rotor.
Friction & windage force and magnetic attraction force between stator & rotor act
in opposite direction and damp this oscillatory motion after a time gap depending
on the magnitude of oscillation.
Since the magnetic attraction force between stator and rotor can be controlled by
changing excitation voltage therefore total damping force acting on rotor motion
can be controlled effectively by imposing excitation voltage proportional to the
incremental power ME.
PSS acts on this principle and damps the dynamic oscillation of the machine
within a shortest possible, which help to keep the machine stable even during
minor disturbance in the grid.
Power oscillation without PSS Power oscillation with PSS

32. Basic function of power System Stabilizer ( PSS)
provided in excitation system (III)
Automatic
Voltage
Regulator
Generator
PT
Set
Voltage
Actual
Voltage
Error
Voltage
Power System
Stabilizer (PSS)
Gen Field
ΔP (Active power)
Δf (Gen frequency)
During power swing, power system stabilizer (PSS) senses the incremental changes in active
power & frequency at generator terminal and converts it to electrical signal for input to AVR.
Influenced by the input signal AVR impose the excitation voltage proportional to the
incremental active power across the field winding so that magnetic attraction between
stator and rotor gets increased and damps the oscillatory motion of rotor within the
shortest possible time.
@ PSS is made for damping oscillation within the limited range. Beyond this range limiters
and protection are taken care of the situation
@ PSS is kept activated only when generator load is more than 50%, because the magnitude
of oscillation increases with the increase of generator load.

33. Grid stability – Over Voltage
Reasons for over voltage
1. Low demand & high supply of VAR
2. Light loading / idle charging of long lines
Disadvantages of over voltage
1. Running generator at leading PF with possibility of pole slipping
2. Possibility of failure of system insulation due to over voltage stress during switching /
line to ground fault
Measures for avoiding over voltage
1. Decreasing the Tap position of Transformers
2. Switching off capacitor banks
3. Disconnecting lightly loaded / idle charging long lines .
4. Switching on reactors .
Calculation of reactive power Formula Data
System Voltage Skv 420 KV
Fault Current level FkA 40 KA
Short Ckt MVA Scc= 1.732 X Skv X FkA 29097 MVA
Max Bus voltage V1 = 441 KV or (441/420) PU 1.05 PU
Acceptable Bus voltage V2 = 416 KV or (416/420)PU 0.99 PU
Total reactive power Sr = Scc{ ( V2 – V1)/V1} 1763 MVAR
Standard capacity Sst 63 MVAR
Nos of reactor required Sr / Sst 27 Nos

34. Reactors in southern grid
* BUS REACTORS
PGCIL
1. Hosur
2. Kolar
3. Hiriyur
4.Salem
5. Munirabad
6. Hyderabad
7. Sriperumbudur
NTPC
8. Ramagundam
NPCIL
9. Kaiga
NLC
10. TPS II
11. TPS II Expn
* BUS REACTORS
KPTCL
12. Raichur TS
13. Talaguppa
14.Devanagere
15.Neelamangala
APTRANCO
16. Simhadri
17. Srisailam
18. Kurnool
19. Vizag
* LINE REACTORS
PGCIL
1. Neyveli – Trichy I
2. Madurai – Trichy I
3.Salem – Udumalpet II
4.Madurai – Trivandram I
APTRANCO
5. Khammam - Hydrabad
Existing Reactors = 8 Bus + 56 Line = 64 Nos ( 3500 MVAR)
* New addition (2008-11) = 19 Bus + 5 Line = 24 Nos ( 1763 MVAR)

35. Maximum – Minimum operating voltage limit for
transmission & distribution - as per Indian grid
code

36. Grid stability – Load angle
Angular instability is mainly responsible for power oscillations in the system. It
occurs as a result of
 Transient angular instability (varying from 1 to 3 sec.) due to sudden tripping
of load/generator .
Measures : it can be prevented only by automatic actions like fast auto
reclosing, dynamic breaking, switching of series capacitors, power system
stabilizer and static VAR compensators
 Steady state angular instability is mainly experienced when power flow
through the long tie lines interconnecting two large networks increase
beyond its capacity limits. In such cases frequency oscillations of low
intensity is observed. But if this low intensity frequency oscillation is not
controlled, it may trip the tie line leading to grid disturbance.
Measures : Continuous monitoring the load angle and initiating corrective
measures accordingly to the situation

37. Load Angle
Sending end
Bus voltage = V1
Load Angle = δ1
Receiving End
Bus Voltage = V2
Load Angle = δ2
Power transfer = P
Line Impedance = X
V1 . V2
P = Sin (δ1 - δ2)
X
V1 . V2
= Sin δ
X
-1 P . X
Load Angle δ = Sin
V1.V2
•Load angle increases with the decrease
of voltage & frequency resulting in
increase of lagging MVAR
•Load angle decreases with the increase
of voltage & frequency resulting in
increase of leading MVAR

38. Monitoring Load Angle
Loadangle and Voltage (Receiving end) relation for different line lengths
3
5
7
9
11
13
15
17
19
21
400 390 380 370 360 350 340 330 320 310 300
VOLTAGE AT RECEIVING END
LoadAngleindegrees
350KM line
200KM line
100KM line

40. Indian Grid – Institutions
Central
Government
State
Government
Private sector –
(Indian and
International)
Ministerial Institutions
Ministry of Power,
 Ministry of New & Renewable
Energy
 Planning Commission,
 Central Electricity Authority,
 Bureau of Energy Efficiency
 Central Electricity Regulatory
Commission
Appellate Tribunal for Electricity
Corporations
 Generation,
Transmission,
 Trading, Financing,
 Manufacturing
 National and Regional Load
Dispatch
Ministerial Institutions
 Ministry of Energy,
 State Renewable Energy
Agency
 State Regulatory
Commission
Corporations
 Generation,
 Transmission,
 Distribution
 State Load Dispatch Centre
 Generation,
 Transmission,
 Distribution,
 Trading, Financing
 Manufacturing,
 Services

41. Indian Grid – Functions of the Institutions
Ministry Of Power
(MoP)
 Legal provisions (EC Act 2003),
 Policy directions
 Guidelines for competitive bidding, etc
Central Electricity Authority
(CEA)
 National Electricity plan,
 Monitoring of projects,
 Maintaining data and statistics,
 Demand forecast,
 Feasibility analysis of Hydro projects
Regulatory Commission
(CERC,SERCs)
 Regulates all players in the sector,
 Decides tariff,
 Approves capital expenditure,
 Monitors supply and service quality
 Ensure implementation of various
provisions of EC Act 2003
Load Despatch Centre
(PGCIL )
 Scheduling and accounting of power at state level.
 Responsible for maintaining grid stability and
discipline
Generation Company
(NTPC,NLC,DVC, NHPC, SEBs ,Privates)
 Subject to provisions of act, can generate power
based on contracts or independently.
 Needs to abide by Load Dispatch directions for
scheduling its generation
Transmission Company
(PGCIL,SEBs)
 Builds and operates the transmission network and
infrastructure
Distribution Company
(SEBs , Private)
 Maintaining and building distribution network
 Metering & billing
 Collection from consumers

42. Indian Grid – Legal Structure
Public / Citizen of India
Legislature
MoP
EC ACT 2003
Policy
CERCSERCs
Regulation &
Orders
Executives
• Tariff
• Capacity Addition
• Customer service