1. Overview of Indian Power Sector 6-9 2. Power System Operation Corporation Limited 10-12 3 Eastern Regional Load dispatch Centre 13-15 4. Frequency Management 16-20 5. Voltage Management 21-23 6. Outage Planning 24-25 7. Switching Coordination 26 8. Periodic Report and Event Information 27 9. Network Security and Congestion Management 28-29 10. Scheduling and Load Dispatch 30-33 11. SCADA/EMS System Operation 34-38 12. Synchrophasor Initiative 39-43 13. Metering and Settlement System 44-47 14. Conclusion 48 15. Bibliography 49

1. 1
A
SUMMER INTERNSHIP AND PROJECT REPORT
ON
POWER SYSTEM OPERATION CORPORATION
LIMITED (POSOCO), ERLDC, KOLKATA
By
PRATAP BHUNIA
In partial fulfilment of Summer Internship for the award of the degree
Of
BACHELOR OF TECHNOLOGY
In
Electrical Engineering
Techno India, Salt Lake
EM 4/1, Salt Lake, Kolkata 700091
JULY, 2015

2. 2
SUMMER INTERNSHIP SCHEDULE
(15th
June, 2015 – 14th
July, 2015)
DATE NAME OF DEPARTMENT MENTOR SIGNATURE
15.06.2015
to
17.06.2015
Orientation, Overview, Grid
Management
Sh. P. P.
Bandyopadhyay
Dy. Gen. Manager
18.06.2015
to
24.06.2015
System Studies, Management
Information Systems (MIS)
Sh. S. Banerjee
Asstt. GM
25.06.2015
to
30.06.2015
SCADA and IT Sh. S. P. Barnwal,
CM
01.07.2015
to
09.07.2015
Metering and Settlement,
Ancillary Service, Short Term
Open Access (STOA)
Sh. G. Chakraborty
Dy. Gen. Manager
10.07.2015
to
14.07.2015
System Operation Sh. P. S. Das
GM

3. 3
ACKNOWLEDGEMENT
Any accomplishment requires effort of many people and this work is not different. This
satisfaction drives for accomplishment would be with acknowledging the effort of persons behind
it.
I express my gratitude to Mr G. K. Kundu, Manager (HR), ERLDC Kolkata, for allowing me to
carry the Summer Internship in Eastern Region Load Dispatch Centre (ERLDC) under Power
System Operation Corporation Limited (POSOCO).
I am grateful to Mr S. Banerjee, Asstt. GM, Mr P. P. Bandyopadhyay, Dy. Gen. Manager, Mr
S. P. Barnwal, CM, Mr G. C. Chakraborty, Dy. Gen. Manager, Mr P. S. Das, Asstt. GM, Mr
Shailendra Chouhan, Dy. Manager (Operation), Mr Manoj Kumar Thakur, Dy. Manager, Mr
Sanjay Kumar Sahu, Manager and Mr Biswajit Mondal for providing me motivation and
guidance during the entire training. Their valuable suggestions and comments have made it
possible for me to complete this training report.
I am also thankful to Mr S. Paul, HOD, Electrical Engineering department in our college for
giving me an opportunity for the Summer Internship on ERLDC, Kolkata under POSOCO.
Thanks are also due to all the engineers of the ERLDC, Kolkata for helping me in providing
enough information on Indian Power System and its operation & protection related information.
Lastly I would like to thank my friends along with whom I completed my training and without
whose help this project would remain incomplete.
--------------------------------------
(PRATAP BHUNIA)
ROLL No. - 13001612118

4. 4
PREFACE
A student gets theoretical knowledge from classroom and gets practical knowledge from industrial
training or internship. When these two aspects of theoretical knowledge and practical experience
together then a student is fully equipped to secure his best.
In conducting the internship in an organisation, students get exposed and have knowledge of real
situation in the work field and gains experience from them. The object of the internship is to
provide an opportunity to experience the practical aspect of technology in any organization. It
provides a chance to get the feel of the organization and its function.
Electrical energy is very important. Both the historical and the present-day civilization of mankind
are closely interwoven with energy, and there is no reason to doubt but that in the future our
existence will be more are more dependent upon the energy. Electricity energy occupies the top
position in the energy hierarchy. It finds innumerable uses in home, industry, agriculture and even
in transport. Besides its use for domestic, commercial and industrial purposes it is required for
increasing defence and agricultural production.
The process of modernisation, increase in productivity in industry and agriculture and
improvement in the quality of the people depend so much upon the supply of electrical energy that
the annual per capita consumption of electrical energy has emerged those days as an accepted
yardstick to measure the prosperity of a nation. India had a per capita consumption of electrical
energy of 631 kWh in 2006-2007 and 916.18 kWh in 2012-2013.

5. 5
CONTENTS
Sl. No. Title Page Number
1. Introduction of Indian Power Sector 6-9
2. Power System Operation Corporation Limited 10-12
3 Eastern Regional Load dispatch Centre 13-15
4. Frequency Management 16-20
5. Voltage Management 21-23
6. Outage Planning 24-25
7. Switching Coordination 26
8. Periodic Report and Event Information 27
9. Network Security and Congestion Management 28-29
10. Scheduling and Load Dispatch 30-33
11. SCADA/EMS System Operation 34-38
12. Synchrophasor Initiative 39-43
13. Metering and Settlement System 44-47
14. Conclusion 48
15. Bibliography 49

6. 6
INTRODUCTION OF INDIAN POWER SECTOR
The power sector in India has undergone significant progress after Independence. When
India became independent in 1947, the country had a power generating capacity of 1,362 MW.
Hydro power and coal based thermal power have been the main sources of generating electricity.
Generation and distribution of electrical power was carried out primarily by private utility
companies. Notable amongst them and still in existence is Calcutta Electric. Power was available
only in a few urban centres; rural areas and villages did not have electricity. After 1947, all new
power generation, transmission and distribution in the rural sector and the urban centres (which
was not served by private utilities) came under the purview of State and Central government
agencies. State Electricity Boards (SEBs) were formed in all the states. Nuclear power
development is at slower pace, which was introduced, in late sixties. The concept of operating
power systems on a regional basis crossing the political boundaries of states was introduced in
the early sixties. In spite of the overall development that has taken place, the power supply
industry has been under constant pressure to bridge the gap between supply and demand.
From, the Fifth Plan onwards i.e. 1974-79, the Government of India got itself involved in a
big way in the generation and bulk transmission of power to supplement the efforts at the State
level and took upon itself the responsibility of setting up large power projects to develop the coal
and hydroelectric resources in the country as a supplementary effort in meeting the country’s
power requirements. The National thermal Power Corporation (NTPC) and National Hydro-
electric Power Corporation (NHPC) were set up for these purposes in 1975. North-Eastern
Electric Power Corporation (NEEPCO) was set up in 1976 to implement the regional power
projects in the North-East. Subsequently two more power generation corporations were set up in
1988 viz. Tehri Hydro Development Corporation (THDC) and Nathpa Jhakri Power Corporation
(NJPC). To construct, operate and maintain the inter-State and interregional transmission
systems the National Power Transmission Corporation (NPTC) was set up in 1989. The
corporation was renamed as POWER GRID in 1992.
GOI has promulgated Electricity Regulatory Commission Act, 1998 for setting up of
Independent Regulatory bodies both at the Central level and at the State level viz. The Central
Electricity Regulatory Commission (CERC) and the State Electricity Regulatory Commission
(SERCs) at the Central and the State levels respectively. The main function of the CERC are to
regulate the tariff of generating companies owned or controlled by the Central Government, to
regulate the tariff of generating companies, other than those owned or controlled by the Central
Government, if such generating companies enter into or otherwise have a composite scheme for

7. 7
generation and sale of electricity in more than one State to regulate the inter-state transmission of
energy including tariff of the transmission utilities, to regulate inter-state bulk sale of power and
to aid & advise the Central Government in formulation of tariff policy. The CERC has been
constituted on 24.7.1998.
The Electricity Laws (Amendment) Act, 1998 provides for creation of Central and State
Transmission utilities. The function of the Central Transmission Utility shall be to undertake
transmission of energy through inter-state transmission system and discharge all functions of
planning and coordination relating to inter-state transmission system with State Transmission
Utilities, Central Government, State Governments, generating companies etc. Power Grid
Corporation of India Limited will be Central Transmission Utility.
 Total Installed Capacity ( As on 30.04.2015):
Sector Mega Watt (MW) %age
State Sector 95,079 34.9
Central Sector 72,721 26.7
Private sector 1,04,887 38.5
Total 2,72,687
Fuel Mega Watt (MW) %age
Total Thermal 189,498 69.5
Coal 165,236 60.6
Gas 23,062 8.5
Oil 1,200 .4
Hydro (Renewable) 41,632 15.3
Nuclear 5,780 2.1
Renewable Energy 35,777 13.1
Total 2,72,687

8. 8
 Plant Load Factor (PLF):
Year
Target Actual Sector Wise Actual
%age %age Central State Private
2011-12 68.7 73.3 82.1 68.0 69.5
2012-13 70.0 69.9 79.2 65.6 64.1
2013-14 69.6 65.6 76.1 59.1 62.1
2014-15 65.52 64.46 73.96 59.83 60.58
2015-2016 69.70 61.89 72.48 55.45 59.20
 Indian Power Grid divided into five main regions:
1. Eastern Region
2. Western Region
3. Northern Region
4. North Eastern Region
5. Southern Region
Fig: 1
SOUTHERN
REGION
WESTERN
REGION
EASTERN
REGION
NORTHERN
REGION NORTH-
EASTERN
REGION
REGIONAL
GRIDS

9. 9
 Evolution of National Grid:
 Grid management on regional basis started in sixties.
 Initially, State grids were inter-connected to form regional grid and India was
demarcated into 5 regions namely Northern, Eastern, Western, North Eastern and
Southern region.
 In October 1991 North Eastern and Eastern grids were connected.
 In March 2003 WR and ER-NER were interconnected .
 August 2006 North and East grids were interconnected thereby 4 regional grids
Northern, Eastern, Western and North Eastern grids are synchronously connected
forming central grid operating at one frequency.
 On 31st December 2013, Southern Region was connected to Central Grid in
Synchronous mode with the commissioning of 765kV Raichur-Solapur
Transmission line thereby achieving 'ONE NATION'-'ONE GRID'-'ONE
FREQUENCY'.
Fig: 2

10. 10
POWER SYSTEM OPERATION CORPORATION LIMITED
 Formation of POSOCO:
Central Government through Ministry of Power in exercise of the power conferred by
sub-section (3) of Sect 26 and sub-section (2) of Section 27 of the Electricity Act, 2003, by
notification date September 27, 2010 in the Gazette of India notified that the Power System
Operation Corporation Ltd (POSOCO), a wholly owned subsidiary of the Power Grid
Corporation of India Limited (a Government Company) shall operate National Load Despatch
Centre and the five Regional Load Despatch Centres, with effect from October 1, 2010.
To make load despatch centres financially self-reliant and autonomous, the Pradhan
committee recommended independent and sustainable revenue streams. The move to separate the
two functions is in keeping with the provisions of the Electricity Act, 2003, which seeks to
separate commercial interests from load management functions. The Pradhan committee had
recommended setting up a separate representative board structure overseeing the functions of the
five regional load despatch centres (RLDCs) run by PGCIL—the northern, eastern, north-
eastern, western and southern regions at that time.
POSOCO is a wholly owned subsidiary of Power Grid Corporation of India Limited. It was
formed in March 2010 to handle the power management functions of PGCIL. It is responsible to
ensure the integrated operation of the Grid in a reliable, efficient and secure manner. It consists
of 5 Regional Load Despatch Centres and a National Load Despatch Centre. The subsidiary may
eventually be made a separate company, leaving the parent firm with only the task of setting up
transmission links. The load despatch functions, earlier handled by PGCIL, will now come up to
POSOCO.
 Mission of POSOCO:
Ensure Integrated Operation of Regional and National Power Systems to facilitate transfer of
electric power within and across the regions and trans-national exchange of power with
Reliability, Security and Economy.
 Departments of POSOCO:
POSOCO have many departments, those are:
1. Regulatory Affairs:
 IEGC
 Electricity Act 2003

11. 11
 Transmission Notification
 Grid Standards
 Metering Standards
 ABT order
 Open Access Regulations
 UI Regulations etc.
2. Market Operations:
 Scheduling Procedures for
o Bilateral STOA
o Collective STOA
 Functions & Activities of Power Exchange
 Daily Collective Transactions Procedure
3. Real-Time Grid operations:
 Overview of National Grid
 Various Grid Profile
 Grid Operation & Management
 Preparation of Daily Reports
4. Power System Studies:
 Base Case formation
o Updation of BaseCase
o Power System Case Studies in
 Steady State
 Transient State
 Dynamic State
5. Settlement System & UI Pool Accounts:
 Concepts of
o UI Pool Accounts
o Settlement System
 Weekly Settlement of UI Accounts

12. 12
6. SCADA/IT & Establishment:
 Basic SCADA/EMS setup
 EMS applications
o Display Updation
o Modelling of New Sub-stations, SLDs & Transmission Lines
o Handling Problems regarding Link Outages
 Hierarchical Structure of POSOCO:
POSOCO have One National Load Dispatch Centre (NLDC) and five Regional Load Dispatch
Centre (RLDC), those are
1. Eastern Regional Load Dispatch Centre (ERLDC)
2. Western Regional Load Dispatch Centre (WRLDC)
3. Northern Regional Load Dispatch Centre (NRLDC)
4. North Eastern regional Load Dispatch Centre (NERLDC)
5. Southern Regional Load Dispatch Centre (SRLDC)
Fig: 3

13. 13
EASTERN REGIONAL LOAD DISPATCH CENTRE
 Introduction:
In compliance to the IEGC (Indian Electricity Grid Code) this internal Operating Procedure for
Eastern Region is developed in consultation with the regional constituents of Eastern Region.
Eastern Region Grid system comprises of the states of Bihar, Jharkhand, Orissa, West Bengal
and Sikkim and has an operating area of 4,25,423 sq km, which is about 13% of the total area of
the country. Damodar Valley Corporation (DVC) established under sub-section (1) of Section 3
of the Damodar Valley Corporation Act, 1948 in eastern region is an integrated utility similar to
STU/SEB encompassing part of the states of West Bengal and Jharkhand and has its own
generation, transmission and distribution facilities in its identified command area. Eastern
Region is strategically located and has interconnections with all the other regions as well as with
neighbouring countries like Bangladesh, Bhutan and Nepal.
The internal operating procedure as prepared by ERLDC is to clearly specify the roles of each
player in the grid i.e., Central Sector Generating and Transmission Utilities, State Utilities,
Independent Power Producers, Traders, System Operators and other agencies operating in the
power market to facilitate grid operation in efficient, secure, reliable and economic manner.
 Functions of ERLDC:
 Facilitates:
Integrated operation for improved quality, Security and Reliability of Power Supply on
Regional Basis
 Provides:
Avenues for Intra-Regional and Inter Regional Exchanges
 Telemeters:
Live Data from Major Generating Plants and Sub-stations
 Co-ordinates:
Drawal Schedule from for all ISGS constituents
 Persuades:
Constituents to Match Drawal Schedule

14. 14
 Issues:
Clearance for outage of Elements for Maintenance Work
 Supplies:
Management Information about Performance of Grid Operation
 Supports:
Constituents in Power System Studies
 Monitors:
Generation of C.S. Power Stations and Power Flow in Major Lines and Tie Lines
 Endeavours:
To Maintain Network Security
 Processes:
Special Energy Meter Readings for Bulk Power Energy Settlement
 Implements:
IEGC and Regulatory Directives
 Overview of Eastern Region:
 Eastern regional grid is an electrical system comprising of 4,25,000 Sq. KM . It
comprises six constituents namely:
1. BSEB (Bihar State Electricity Board)
2. SEB (Jharkhand State Electricity Board)
3. GRIDCO (Grid Corporation of Orissa)
4. DVC (Damodar Valley Corporation)
5. WBSEB (West Bengal State Electricity Board)
6. SIKKIM
 Effective Generating Capacity of utilities as on 31.01.15 is 32,734 MW.
 Daily average (Apr-14 to Jan-15) Energy Consumption: approximately 330 MU.
 Average (Apr-14 to Jan-15) inter-regional export from ER: 57 MU per day.
 Maximum regional demand met was 17649 MW on 22/10/14.

15. 15
 Power Map of Eastern Region:
Fig: 4

16. 16
THE OPERATING PROCEDURE OF ERLDC
The Operating procedure of the Eastern Region system contains the following
 Frequency Management
 Voltage Management
 Outage Planning
 Switching Coordination
 Periodic Reporting and Event Information
 Network Security and Congestion Management
 Scheduling and Despatch
 SCADA/EMS System Operation
 Synchrophasor Initiative
 Metering & Settlement System
FREQUENCY MANAGEMENT
 Frequency Standard:
IEGC has mandated that all Regional entities shall make all possible efforts to ensure
that the grid frequency always remains within the 49.9-50.05 Hz band, Frequency is the most
important indicator of the quality of supply and is the global parameter in the grid i.e. it is same
throughout an inter -connected power system. Since frequency is a function of the load-
generation balance, it is subject to variation on a continuous basis as either of the two viz.
generation or load may vary from time to time. Whenever, the frequency approaches upper/lower
limits of the above range, advance action needs to be initiated in order to arrest further rise/fall in
frequency; as it takes some time for remedial measures to give desired result.
 High Frequency Conditions:
In case the frequency is high (above 50.05Hz) and is in increasing trend then the
following actions may be initiated:
1. ERLDC shall check whether the high frequency condition is due to the heavy under-drawal
by any entity within the region or by neighbouring regions. In the latter case, the matter
has to be brought to the notice of the concerned region as well as NLDC for necessary

17. 17
remedial action
2. ERLDC shall advise the regional entities within ER to lift load shedding if any.
3. However, before taking up with other regions / NLDC, ERLDC would check the
possibility of any backing down of the reservoir based hydro stations within state system.
4. ERLDC before advising any generation reduction at the hydro stations, in consultation
with concerned SLDC, would check back whether such reduction would cause any
adverse change in voltage levels or network loading in the ISTS. Similarly, the concerned
SLDC would also assess the impact on its intra-state network. In case any problem is
envisaged due to such generation reduction, the same shall be avoided.
5. Explore the possibility of running of Purulia Pump storage hydro units in pump mode, in
consultation with SLDC, West Bengal.
6. Advise/remind the states to back down costly generation as per merit order by taking
adequate support from SCADA.
7. If any ISGS (other than must run) is generating more than their schedule, advise the ISGS
to reduce the over injection.
8. The Hydro stations of Bhutan power system exporting power to India are not covered
commercially under ABT mechanism. Backing down advice on account of high
frequency conditions may be issued to stations at Tala, Chukha and Kiruchu of Bhutan
system only after all possible remedial measures are exhausted. However, in case the
stations are noticed generating extra with respect to schedule issued , ERLDC shall
attempt revising the generation schedule with due revision of constituents drawal
schedule.
9. In case any regional entity is underdrawing/overinjecting, ERLDC may advice to
maintain net exchange as per schedule.
10. In case any regional entity is under-drawing, ERLDC may advice concerned SLDC for
considering surrendering of its share from ISGS, based on merit order.
11. If the frequency is still high, and action from underdrawing beneficiaries is not
forthcoming, ERLDC shall suo-motto reduce the generation schedule of ISGS with
corresponding downward revision of schedule of the concerned beneficiary
12. Backing down of the spilling hydro units or the run-off-the-river units for short duration
may also be considered if all other options are exhausted.
 Low Frequency Conditions:
If the frequency is less than 49.9 Hz. and has a decreasing trend, the following
actions may be taken:

18. 18
1. ERLDC shall check whether the low frequency condition is due to the heavy over-drawal
by regional entities or by the neighbouring regions. In the event of overdrawal by
neighbouring regions, matter may be brought to the notice of NLDC through written
messages with a copy/ies to the RLDC of the over drawing region(s).
2. If any unit of Purulia Pump storage is operating in pump mode and if the concerned
beneficiary is over drawing, ERLDC shall advise the concerned SLDC for discontinuing
the pump operation.
3. ERLDC may advise all regional entities / control areas, through their respective SLDCs
to maximize their internal generation viz. hydro, thermal, IPP etc. in case margins are
available.
4. Deviation Settlement Mechanism and related matters Regulations, 2014. already lays
down appropriate financial and legal penalties for under-generation / over-drawal at low
frequency. Nevertheless, if any ISGS is under-generating, it may be reminded to generate
as per schedule. If such generation increase is not possible due to any technical
constraints, the concerned ISGS may be advised to reduce its Declared Capability.
ERLDC would then correspondingly reduce the drawal schedules of all concerned
beneficiaries (including outside regions) and advise them to maintain their net exchanges
as per their respective revised schedules.
5. The Actual receipt from the Hydro stations from Bhutan may be closely monitored under
low frequency conditions. In case such receipt is less than the schedule, because of some
technical reasons like low inflow etc., ERLDC may suo motto revise the generation
schedule downwards with corresponding downward revision of drawal schedules of the
respective constituents who have share on such stations. Such downward revision shall be
duly informed to the concerned beneficiaries with an advise to curtail their drawal from
the grid.
6. If the frequency is less than 49.9Hz. and has a falling trend, remind the SLDC(s) of
overdrawing regional entity /entities telephonically to maintain frequency by picking up
internal generation/ curtailing overdrawal. The estimation of over-drawal has to be done
corresponding to nominal frequency (50.0 Hz) after applying requisite frequency bias
correction on the exchange at the prevailing off-nominal frequency.

19. 19
7. If the frequency is less than 49.9 Hz and it may appear that practically no control area is
as such overdrawing, a general message may be issued to all regional entities requesting
to estimate their respective actual net exchanges at 50.0 Hz (after applying necessary
frequency correction factor on the existing interchange) and improve internal generation/
shed loads wherever the estimated actual drawal corresponding to 50.0 Hz exceeds the
net scheduled drawal.
8. ERLDC may further examine the latest status of thermal units under outage (forced) and
find out when the units are expected to be on bar and take up for expediting the same.
9. As a long term measure, It may be examined that whether a planned maintenance of any
unit can be postponed without much affecting the AMP of other units.
10. Notwithstanding the above as per clauses 6.4.12 of IEGC, ERLDC may direct the
SLDCs/ISGS/ other regional entities to increase/decrease their drawal/generation in case
of contingencies e.g. overloading of lines/transformers, abnormal voltages, threat to
system security. Such directions shall immediately be acted upon. In case the situation
does not call for very urgent action, and ERLDC has some time for analysis, it will be
checked whether the situation has arisen due to deviations from schedules. These shall be
got terminated first, through appropriate measure like opening of feeders , if considered
necessary by SLDC/ERLDC, before an action, which would affect the scheduled supplies
to the long term, medium term customers or short term customers is initiated in
accordance with Central Electricity Regulatory Commission (Grant of Connectivity,
Long-term Access and Medium-term Open Access in Inter-State Transmission and
Related matters) Regulations, 2009 and Central Electricity Regulatory Commission
(Open Access in Inter-State Transmission) Regulations, 2008.
Violation Type and Category
Duration for issuance of
Message
Frequency
Violation >50.1 Hz or <49.7 Hz Emergency
Message will be issued if
violation
continues for at least 5 minutes
50.05-50.1 Hz or 49.9
Hz Alert
Message will be issued if
violation
-49.7 Hz continues for at least 15 minutes
49.9 Hz -50.05 Hz Normal
Voltage Violation > 425 kV or <380 kV Emergency Message will be issued if

20. 20
violation
continues for at least 15 minutes
415 kV - 425 kV or
390 Alert
Message will be issued if
violation
kV - 380 kV continues for at least 15 minutes
>390 kV to <415 kV Normal
Loading Violation
> Thermal Loading
under Emergency
Message will be issued if
violation
n-1 contingency continues for at least 5 minutes
= Thermal Loading
under Alert
Message will be issued if
violation
n-1 contingency continues for at least 15 minutes
< Thermal Limit under
n-1 Normal
contingency
Zero Crossing
1 Failure (issued 14th
time Emergency
Violation Block)
Issued in 11th time
block if Alert
the direction not
changed
for 10 time blocks
Zero Crossing done
within Normal
10 time Blocks
Deviation
Violation > 20% or 250 MW Emergency
Message will be issued if
violation
(whichever lower) continues for at least 5 minutes
12%-20% or 150 MW
to Alert
Message will be issued if
violation
250 MW (whichever continues for at least 15 minutes
lower)
<12% or 150 MW Normal
(whichever lower)
Note:
1. General Approach is to issue Alert Message before reaching Critical level
2. Generally every Alert is considered for maximum of 15
Minutes
3. Generally any Emergency considered for maximum of 5
minutes

21. 21
VOLTAGE MANAGEMENT
 Introduction:
In compliance to the IEGC (Indian Electricity Grid Code) all regional constituents
shall make all possible efforts to ensure that the grid voltage always remains within the following
operating range
Nominal Maximum Minimum
(KV –Rms) (KV –Rms) (KV –Rms)
765 800 728
400 420 380
220 245 198
132 145 122
Eastern Region Grid has a very good spatial distribution of generation rendering a better voltage
profile across 400 kV and 220kV network. However, in some pockets of system where radial loads
are fed, occasional low voltage is experienced. Posts commissioning of Tala Transmission system
exhaustive 400kV networks have been laid. This part of the network is essentially used to evacuate
the hydro power from Bhutan system, generation of Teesta-V HPS and surplus hydro power of
North Eastern Grid during monsoon. Normally the 400kV system usually operates within the
prescribed voltage limit as specified in the IEGC. 400kV stations at Jeypore occasionally
experience low or high voltages due to the low fault MVA of these stations. As the HVDC station
Gajuwaka is also connected to Jeypore having low fault MVA, any power flow change associated
with switching of filter banks operation render at times wide fluctuations in voltage at 400kV level.
 AVRs of Generators:
As per the IEGC, all generating units shall keep their Automatic Voltage Regulators
(AVRs) in operation and power system stabilizers (PSS) in AVRs be appropriately tuned.
 VAR Generation / Absorption by Generating Units:
In order to improve the overall voltage profile, the generators shall run in a manner so
as to have counter balancing action corresponding to low/high backbone grid voltage and to bring
it towards the nominal value. In order to achieve the same, all generators shall generate reactive
power during low voltage conditions and absorb reactive power during high voltage conditions as
per the capability limit of the respecting generating units. The online tap changers (OLTC) on the
generator transformer wherever possible should also be used to achieve this. Off load tap changes
should be used to take care of the seasonal variations in the voltage profile.
 Control of Voltage at Grid Substations/Generating Stations:
Following corrective measures in order of priority shall be taken by ERLDC for ISTS

22. 22
system and regional entities and by SLDC for state entities in the event of voltage going beyond
the operating limits as stipulated in IEGC.
 High Voltage:
In the event of high voltage (e.g. 400 kV voltage going beyond 415 kV and having a rising
trend) following specific steps would be taken by the respective grid substation/generating station
at their own, with intimation to ERLDC, unless specifically mentioned by ERLDC/SLDCs. Before
taking any voltage control action the reason for high voltage as observed /reported be carefully
studied The network adjoining to the substation/s experiencing high voltage be also carefully
studied and areas/substations /generating stations be identified where voltage control measures
need to be taken in the following order of priority
1. The bus reactor be switched on.
2. The switchable line/tertiary reactor are taken in.
3. Optimization of the filter banks at HVDC terminal (provided high voltage is being
experienced in the vicinity of the terminal).
4. The Generating units on bar at the stations in proximity to high voltage areas, absorb
reactive power within the limits of their capability curves.
5. Check the possibility of changing the transformer Tap if one side of ICT is witnessing High
voltage while other side is having low voltage.
6. Checking possibility of rerouting /change of power flow on HVDC terminals so that
loading on parallel EHV network can be altered that may result in reduction in voltage.
7. ERLDC/SLDCs shall consider opening one circuit of lightly loaded multi circuit lines
around the area /substation where high voltage is reported, ensuring security of the balance
network. In case it becomes essential to switch out one of the circuits of inter-regional lines
to mitigate high voltage at one or more inter-regional sub-stations, due consent would be
obtained from the concerned neighbouring RLDC (s) and NLDC.
 Low Voltage Condition:
In the event of low voltage(e.g. 400 kV voltage going below 390 kV and have a declining
trend), following specific steps would be taken by the respective grid substation/generating station
at their own, with intimation to ERLDC, unless specifically mentioned otherwise by
ERLDC/SLDCs. However, before taking any voltage control action, the reason for low voltage as
observed /reported be carefully studied. The network adjoining the substation/s experiencing low
voltage be also carefully studied and areas/substations /generating stations be identified where
voltage control measures need to be taken in the following order of priority
1. Close the lines which were opened to control high voltage after obtaining due
permission from ERLDC/SLDCs.
2. The bus reactor be switched out
3. The switchable line/tertiary reactor be taken out

23. 23
4. Optimization of the filter banks at HVDC terminal
5. Check the possibility of changing the transformer Tap if one side of ICT is
witnessing Low voltage while other side is having High voltage
6. All generating units on bar shall generate reactive power up to the limits of their
respective capability curves.
7. Operate hydro generator for VAR generation i.e. at lagging p.f.
8. Check possibility of altering HVDC power flow settings on HVDC terminals so that
loading on parallel EHV network goes down resulting in rise in voltage.
 Switching off the Line Reactors in Case of Low Voltage:
In the event of persistent low voltage conditions, some of the line reactors are to
be selected on the basis of line length, grid conditions, network topology etc., which can be
switched off in order to improve the system voltage profile.
 Voltage Profile of Eastern Regional Grid:
Fig: 5
350
370
390
410
430
450
KV
CENTRAL
MAX
MIN
340
360
380
400
420
440
460
KV
NORTHERN
MAX
MIN
350
370
390
410
430
450
KV
SOUTHERN
MAX
MIN

24. 24
OUTAGE PLANNING
 Introduction:
In reference to the IEGC, this section sets out the procedure for preparation of outage
schedule for generating units and transmission elements of the region in a coordinated and
optimal manner keeping in view the regional system operating conditions and maintaining load
generation balance in the system. Adequate security margins shall be ensured while preparation
of the generation and transmission outage programme. ERPC secretariat shall be responsible for
preparation of the annual outage plan in advance for the financial year and be reviewed on
monthly basis.
 Objective:
 To formulate a coordinated outage programme of transmission lines and generating units
for the regional grid considering all the available regional resources and taking into account
transmission constraints as well as other requirements.
 To minimise surplus or deficit, if any, in the requirement of power and energy and help to
operate system within the grid standards.
 To optimise the transmission outages of the elements of the Eastern Regional grid that
should not affect adversely the regional grid operation but take into account the generation
outage schedules, outage of SEB/STU systems thereby maintaining security standards.
 Outage Planning Procedure:
1. For the purpose of Load Generation Balance (LGB)/ Outage planning process, OCC
(Operation Coordination Sub Committee) of ERPC shall, in general, be the forum for
reviewing and deciding the outage planning.
2. It shall be the responsibility of the ERPC secretariat to analyse the outage programmes
proposed by various agencies and, prepare a draft annual outage schedule for finalization
of the annual outage plan for the following financial year by 30th
November of each year.
3. All SLDCs/STUs, CTU, ISGS, IPPs, shall provide RPC Secretariat their proposed outage
programmes in writing for the next financial year by 31st
October of each year. These shall
contain identification of each generating unit/ transmission line/ICT, the preferred date for
each outage and its duration and where there is flexibility, the earliest start date and latest
finishing date.

25. 25
4. Each load serving control area shall be responsible to match its demand with the
anticipated availability from its own plant(s) and availability from ISGS / other purchase
/ sale contracts. The SLDC/STUs along with the proposed outage programme, therefore,
shall also furnish details of the anticipated load generation balance report (LGBR) to
ERPC secretariat in order to facilitate preparation of the annual outage plan.
5. ERPC Secretariat after receiving the outage programme will study the following :-
a. Total power and energy availability (for peak and off-peak condition).
b. Month wise availability and requirement.
c. In case of both surplus and deficit, proper staggering of generation outage to
reduce/ eliminate the deficit.
d. In case of only deficit efforts to be taken to even out high and low deficit by
staggering of generation outage.
e. The anticipated programme for bilateral transaction under STOA or otherwise by
state beneficiaries.
6. ERPC Secretariat shall then come out with a draft load generation balance report (LGBR)
and draft outage programme for the next financial year by 31st
December of each year for
the Regional grid taking into account the available resources in an optimal manner and to
maintain security standards. This will be done after carrying out necessary system studies
and, if necessary, the outage programmes shall be rescheduled. Adequate balance between
generation and load requirement shall be ensured while finalising outage programmes.
7. The final outage plan along with the Load Generation Balance report(LGBR) shall be
prepared in consultation with NLDC and RLDC and intimated to NLDC, Users, STUs,
CTU, other generating stations connected to ISTS and the RLDC for implementation latest
by 31st
January of each year as mutually decided in ERPC forum.
8. Shutdown planning of any element affecting the power transfer to Bangladesh will be done
in coordination with NLDC.
9. The above annual outage plan shall be reviewed by ERPC Secretariat on quarterly and
monthly basis in coordination with all parties concerned, and adjustments made wherever
found to be necessary.
Fig: 6

26. 26
SWITCHING COORDINATION
 Introduction:
Coordination of switching operations in the grid is important for ensuring safety of
personnel and equipment as well as for ensuring adequacy and security of the grid. Before any
operation of important elements of the Eastern Regional Grid is carried out on a User/STU system,
the Users, SLDC, STU, CTU, licensee shall inform ERLDC, in case the Eastern Regional grid
may, or will experience an operational effect.
 Switching of System Elements for First Time:
In line with Regulation of the Central Electricity Authority (Grid Standards) regulations 2010, no
entity shall introduce an element in the ISTS of Eastern Grid without the concurrence of ERLDC
in the form of an operation code. In case a new power system element in Eastern Regional grid is
likely to be connected with the Inter-State Transmission System or is to be energized for the first
time, from the ISTS, the applicant User/STU/CTU/licensee shall send a separate request in
advance along (at least one week) with the confirmation of the following:
• Acceptance of ERLDC with regards to registration as regional entity
• Signed Connection Agreement if applicable
• Availability of telemetry of station/Element at the ERLDC/SLDC
• Availability of voice communication with the station at ERLDC/SLDC
• Interface meter installed and tested by downloading data and forwarding it to ERLDC
• Single Line Diagram
• Healthiness of Protection System/Protection Setting
• Statutory clearance has already been obtained
 Switching of Important Elements:
In line with regulation of the IEGC no part of the Eastern Regional grid shall be deliberately
isolated from the rest of the National/Regional grid except under an emergency conditions in which
such isolation would prevent a total grid collapse and would enable early restoration of power
supply or safety of human life; when serious damage to a costly equipment is imminent and such
isolation would prevent it; when such isolation is specifically instructed by ERLDC.
Important elements of the regional grid, which have a bearing on the network security, is
compiled and issued by ERLDC as a separate document. The regional entities, users, STU, CTU,
licensee shall obtain ‘operation code’ from ERLDC before carrying out any switching operation
on any of the important elements of the Northern Regional grid. Shut down of any 400 kV bus at
substation needs approval of ERLDC.

27. 27
PERIODIC REPORT AND EVENT INFORMATION
 Introduction:
Timely and accurate reporting and exchange of information plays an important role in
grid operation. This assumes more importance during an occurrence/ a disturbance or in crisis.
Timely and accurate information flow under such conditions would help operators in making an
informed decision and reduces uncertainty. Here we describes the event information and
reporting procedure in writing to all Regional entities, ERPC Secretariat/ERLDC/SLDC in
accordance with the clause of IEGC. This section we describes the different periodic reports to
be prepared by RLDC to be sent to all entities of the region and ERPC Secretariat.
 Event Information:
1. All the following events require reporting by ERLDC/ Regional entity
i) Violation of security standards
ii) Grid Indiscipline / Grid Disturbance
iii) Non-Compliance of RLDC’s instructions
iv) System islanding / system split
v) Regional blackout / partial system blackout
vi) Protection failure on any element of ISTS and or any item on the agreed list of
the intra-state systems
vii) Power system instability
viii) Tripping of any element of the regional grid
ix) Sudden load rejection in regional entity’s control area
2. Any tripping of an element under the list of important elements of regional grid, whether
manual or automatic, shall be intimated by the control centre of the regional entity to
ERLDC in a reasonable time say within 10 minutes of the incident. Along with the tripping
intimation, the reasons for tripping (to the extent known) and the likely time of restoration
shall also be intimated. Such information can be on telephone, fax or e-mail.
3. Any operation planned to be carried by a regional entity which may have an impact on the
regional grid or on any of the important element, shall be reported by the concerned SLDC
to ERLDC in advance.
4. Any operation planned to be carried out on the instructions of ERLDC which may have an
impact on the system of a regional entity shall be reported by ERLDC to the concerned
SLDC in advance.
5. The intimation and the exact time of revival of any element under the category of important
events will be furnished to ERLDC as early as possible.

28. 28
NETWORK SECURITY AND CONGESTION MANAGEMENT
 Introduction:
The Indian power grid is one synchronous grid viz “NEWS” Grid comprising of
Northern, Eastern, North Eastern, Western region and Southern Region grid. With formation of
the NEWS Grid, there has been sea change in the operational philosophy in system operation
that has already yielded various benefits like peak/off peak demand management through
diversity of time, surplus/deficit management due to seasonal resource variations, demand
forecast errors, weather variations besides increased economic transactions, improvement in
overall system security due to increased stability margin and a higher stiffness to the tune of
4500-5000 MW/Hz. Eastern Region is strategically located with synchronised interconnections
with all the other regions of the NEW Grid besides having synchronous integrated operation with
Bhutan Power system. Eastern Grid is also connected to Southern Region through two no HVDC
interconnections having a total capacity of 3500MW capacity. The large number of synchronous
interconnections of Eastern Region with other regions/neighbouring country like Bhutan and
Nepal in radial mode however has also resulted in evolution of contingencies of critical nature
under different despatch/demand scenarios.
 Transfer Capability:
While a Transmission system is built, inherent design margins are kept in order to
take care of reliability and security issues, future generation growth, ROW issues, cost
optimisation etc. The interregional interconnections as have been planned and over the years had
also taken care of such margins. However, since power flow takes place as per the laws of
physics and with more and more AC interconnections between Areas/Regions the transfer
between two or more regions gets restricted because of factors like generation despatch
conditions, loop flows between regions, upstream or down stream network limitations, voltage
and angular differences between critical buses etc. Thus the Total transfer capability between
areas is equal to or less than the aggregated design capacity of interconnection/s and therefore
need to be assessed through power system studies well in advance considering the load /
generation balance forecast to a fair degree of accuracy.
“Total Transfer Capability (TTC)” means the amount of electric power that can
be transferred reliably over the inter-control area transmission system under a given set of
operating conditions considering the effect of occurrence of the worst credible contingency.

29. 29
“Transmission Reliability Margin (TRM)” means the amount of margin kept in
the total transfer capability necessary to ensure that the interconnected transmission network is
secure under a reasonable range of uncertainties in.
“Available Transfer Capability (ATC)” means the transfer capability of the inter-
control area transmission system available for scheduling commercial transactions (through long
term access, medium term open access and short term open access) in a specific direction, taking
into account the network security. Mathematically ATC is the Total Transfer Capability less
Transmission Reliability Margin.
Fig: 7
It is therefore imperative that the exchanges between regions are contained to a level of
ATC and in no case exceed the TTC between the regions. All the regional entities of Eastern
Region and / or neighbouring region(s) will adhere to their levels of net interchanges as advised
by ERLDC whenever such breach in TTC level among the regions takes place to ensure the grid
security irrespective of frequency and schedule.
Assessment of Total Transfer Capability (TTC), Transmission Reliability Margin (TRM)
and Available Transfer Capability (ATC) for import and export of power in Eastern Region as
required for reliable system operation and for facilitating non-discriminatory open access in
transmission shall be carried out by ERLDC in coordination with National Load Despatch Centre
and other RLDCs. The ‘Detailed Procedure for Relieving Congestion in Real Time Operation’ as
approved by the CERC vide order dated 22.04.2013 may be referred for further details. The
assessed TTC, TRM and ATC shall be posted on ERLDC/NLDC website.
The detailed procedure for assessment of TTC, monitoring and invoking congestion
conditions in real-time, application of Congestion Charge and Congestion Charge accounting and
settlement shall be as per the regulation / procedure issued / approved by CERC
 Defence Mechanism:
Despite utmost caution exercised during operational planning and implementing all the
above steps to improve the network security and reliability, the possibility of a contingent
situation cannot be totally ruled out. It calls for suitable defence mechanism to be available in the
system to take care of such contingencies. Following are the minimum schemes which should be
operational in Eastern Region to ensure safe and secure grid operation.

30. 30
SCHEDULING AND LOAD DISPATCH
 Introduction:
This procedure is applicable to ERLDC and other RLDCs, all the thermal and hydro inter-
State generating stations (ISGSs) on which beneficiary constituents have shares, the beneficiary
constituents of Eastern Region and any regional entity. For the purpose of implementation of the
schedules for import of power from Hydro stations in Bhutan, this procedure shall also be
applicable to the hydro stations of Bhutan.
 Description of the Procedure:
The Regional grids shall be operated as power pools (with decentralized scheduling and
dispatch), in which the States shall have operational autonomy, and SLDCs shall have the total
responsibility for
(i) Scheduling /dispatching their own generation (including generation of their embedded
licensees),
(ii) Regulating the demand of their customers,
(iii) Scheduling their drawal from the ISGS (within their share in the respective plant’s expected
capability),
(iv)Arranging any bilateral interchanges,
(v) Regulating their net drawal from the regional grid.
The system of each State shall be treated and operated as a notional control area. The
algebraic summation of scheduled drawal from ISGS , long-term access , medium term and short-
term open access arrangements shall provide the drawal schedule of each State, and this shall be
determined in advance on daily basis. The regional entities shall regulate their generation and / or
consumers’ loads so as to maintain their actual drawal from the regional grid close to the above
schedule. The regional entities, through their SLDCs shall always endeavour to restrict their net
drawal from the grid within their respective schedules, whenever the system frequency is below
49.8 Hz or the loading of any important transmission element is beyond the acceptable limit. Below
49.7 Hz, regional entities shall carry out requisite load shedding to ensure that there is no
overdrawal.
The introduction of the scheduling and despatch mechanism as mandated in IEGC, has
further evolved the framework for developing other power markets such as Short term open access
transactions and collective transactions that can fit in with the scheduling and despatch procedures
as mandated in IEGC. Further CERC has also issued regulation on Short Term and and Collective
transactions and procedure for short term and collective transactions have been duly issued by
CTU and approved by CERC. Therefore procedure as issued by CTU on Short term and Collective
may be referred separately as a part of this procedure. In order to understand the procedure and
bring in more clarity the scheduling and despatch procedure has been prepared in the form of flow
chart as described below:
The entire activities are broadly divided into three parts namely
(i) Day ahead scheduling
(ii) Revision of schedules

31. 31
(iii)Implementation of Final schedules
The broad guidelines to be followed for scheduling ISGSs under such conditions are as follows:
Fuel shortage would be declared by the generating stations on a day ahead basis
only and status cannot be changed during the day of operation even if fuel supply
status changes, except in case of unit tripping.
The concerned plant shall declare its energy capability (MWh), maximum ex-bus
generation (MW) and minimum possible ex-bus generation (MW) that can be
maintained.
Utilities may requisition based on their requirements either as average MW in all time blocks or
different MW in different time blocks up to the entitled maximum MW remaining within the
total energy entitlement for the day. The default would be average MW during all blocks for
those beneficiaries whose time-block wise requisition is not received by RLDC.
 Revision of Schedule for Upward Revision of Entitlement:
As per present practice agreed by all constituents, in case of upward revision of
entitlement, full entitlement will be scheduled to those constituents who have already requisitioned
full entitlement previously.

In case there is already less requisition by any constituent from ISGS/s for some block, no
revision of schedule will be carried out for upward revision of entitlement for those blocks for
that constituent provided minimum level of generation technically achievable by the station
criteria is satisfied. If minimum level of generation technically achievable by the station criteria
is/are not satisfied, then ERLDC shall increase requisition of that constituent to the extent to give
minimum level of generation technically achievable by the station schedule of that ISGS.
However, for those blocks where full entitlement is requisitioned the same constituents, ERLDC
will schedule full entitlement for that constituent.
 Revision of Schedule for Downward Revision of Entitlement:
In case downward revision of entitlement, revision of schedule will be carried out
subject to restricted entitlement. No revision will be carried out for that constituent, whose
requisition is already below entitlement previously minimum level of generation technically
achievable by the station criteria is/are satisfied and requisition is less than revised entitlement. If
minimum level of generation technically achievable by the station criteria is/are not satisfied, then
ERLDC shall increase requisition of that constituent to the extent to give minimum level of
generation schedule technically achievable by the that ISGS.

32. 32
In case of subsequent upward revision of entitlement, same methodology as followed in
case of upward revision of entitlement will be followed.
For those constituents, who have given less requisition from any ISGS earlier and due to
subsequent downward revision of entitlement from same ISGS which is less than the requisition
(specially when unit trips), schedule from that ISGS will be restricted to entitlement for that
constituent and validity of earlier requisition of that constituent will expire. In case of subsequent
upward revision of entitlement from same ISGS (specially when unit returns), ERLDC will
schedule full entitlement from that ISGS to the same constituent.
 Different Type of Access:
In the power system operation there are two different type of operation or transaction between
the power buyer and power seller. Those are
1. Bilateral Transaction:
 Long Term Access (LTA) for up to 25 years power purchase agreement.
 Medium Term Open Access (MTOA) for 3 months to 3 years agreement.
 Short Term Open Access (STOA) for Intraday to 3 months power purchase
agreement.
2. Collective Transaction: This is done through Power Exchange (PX) of the Day Ahead
Basis.
 Scheduling of LTA and MTOA:
1. Constituent/Generator would only furnish to ERLDC the mutually agreed schedules by 17:00
Hrs for the next day. Endorsement of the concerned SLDC/RLDC (when one of party is from
outside region) will be required.
2. ERLDC would incorporate the schedules and release the schedule for next day by 18:00 hrs.
3. SLDCs/Generators can inform of any mutually agreed changes duly endorsed by concerned
SLDC/RLDC (when one of party is from outside region) by 22:00 hrs. of previous day to
ERLDC.
4. Schedules for next day to be frozen by 23:00 hrs.
5. Revision of the schedule during course of the day would be permitted, depending upon
intimation of the revised mutually agreed schedules duly endorsed by concerned SLDC/RLDC
(when one of party is from outside region) to ERLDC. The concerned SLDCs/RLDCs (when
one of party is from outside region) may also give standing instructions to ERLDC in advance
to accommodate all day ahead requisition/revision on the day of operation, on behalf of
constituents under their jurisdiction so that schedule furnished by other
constituent/s/generator/s will be construed as mutually agreed schedule and will be revised

33. 33
accordingly.
6. In case of tripping of unit of Generating station/s having LTA, schedule will be revised with
intimation to concerned SLDCs/RLDCs. The revised schedules shall become effective from
the 4th time block, counting the time block in which the forced outage is declared and revision
sought in MW quantum from the generator to be the first one.
7. Revised schedules for other revision shall become effective from the 4th
time block, counting
the time block in which revised mutually agreed schedule duly endorsed by concerned
SLDC/RLDC(when one of party is from outside region)has been received by ERLDC to be
the first one.
 Scheduling Procedure:
Fig: 8

34. 34
SCADA /EMS SYSTEM OPERATION
 Introduction:
The coal based thermal capacity is concentrated in eastern part while hydro capacity
is concentrated in south and extreme northern part of India. The electricity is transported from
these concentrations to loads via transmission systems comprising of 765 KV, 400 KV, 220 KV,
132 KV AC network and HVDC system 500KV. Operation of such complicated and vast system
requires a central coordination and information system. For this a Supervisory Control and Data
Acquisition (SCADA) System have been installed jointly by Power Grid, a Central Transmission
Utility (CTU) and state electricity board, the agencies responsible for electricity management in
states.
SCADA system can be illustrated by the analogy of Security cameras installed in a
building for monitoring the entire building from a centralized location. SCADA works in similar
way, each Remote Terminal Unis (RTU) acts like a camera, records the interested measurements
from the power system, sends it to centralized location (Control-centre computer) via
communication media like fibre optic, micro wave, PLCC.
 Hierarchical Structure:
 Hierarchy at National Level:
SCADA system is hierarchical in nature having two distinct hierarchies - one at national level
other at regional level. At national level, SCADA/EMS system of all five RLDCs report to
NLDC. Data from each RLDC is transmitted to NLDC in real time on dedicated communication
lines. The national level hierarchical arrangement is shown in figure.
Fig: 9

35. 35
 Hierarchy at Regional Level:
At regional level RLDC acts as apex body and coordinates the all inter-state activities of
SCADA/EMS systems of SLDCs of a region. SCADA systems of all Sub-LDCs of a state
reports to the SLDC of that state. The hierarchy at regional level is shown in figure.
Fig: 10
 SCADA Main Components:
 RTU (Remote Terminal Unit) located at substations
 Wideband Communication consists of Fibber Optic/Microwave
 Control centre (Load dispatch centre) equipment/software
 Auxiliary system consists of UPS, 48volt DCPS,DG set etc.
The salient features of SCADA System are:-
 Operating system is POSIX compliant.
 LAN and WAN uses OSI compliant protocol.
 Graphical User Interface is Motif.
 ICCP (TASE 2) has been used for inter site exchanges.
 WAN communication is on X.25 with Multilink Bundled PPP
 RTU communication is on IEC 65870.5 – 101 protocols.
 RDBMS is used for historical data archiving.

36. 36
 Function of SCADA:
The list of major functions of the SCADA system are summarized below:-
 Data acquisition from RTUs and storage of data in online database.
 Processing of data for converting the raw values to engineering values, checking
quality, assigning quality flag and checking limit.
 Supervisory control of power system element (not being used at present).
 Historical data storage and retrieval.
 Reconstruction and replay of events.
 Protective and informative tagging of power system device.
 Load Management.
 Sequence of events recording.
 Generalized calculation – for adding and removing operator’s defined
calculations.
 Providing user interface to operators.
 Inter control centre communication.
 Real time and historical trends.
 State Estimation.
 Data Requirements from Substation through SCADA:
Following data are generally acquired from the substation:
1. Analog:-
 Active Power (MW)
 Reactive Power (MVAR)
 Voltage (KV)
 Frequency (HZ)
 OLTC
2. Digital :-
 Circuit breaker status
 Isolator status
 Protection contracts.

37. 37
 Remote Terminal Units:
 Location of RTUs:
All 400KV Sub-Station.
All 220Kv Sub-Station.
All 132Kv Inter-tie Sub-Stations.
All Sub-Stations necessary for Network Analysis.
 Type of RTUs:
1. Critical RTU: All the RTUs which are located at following stations
 All 400KV Sub-Stations.
 All 220KV Sub-Station.
 Power plants with gross output more than 50MW.
 Critical RTUs shall be supported by two communication channel.
2. Non-Critical RTUs: All the other RTUs are non-critical.
 Typical SCADA System:
Fig: 11

38. 38
Fig: 12
Sample of SCADA Data
Fig: 13

39. 39
SYNCHROPHASOR INITIATIVE
 Introduction:
Recent advances in measurement, communications and analytic technologies have
produced a range of new options. In particular, wide area measurement systems (WAMS) have
come to the fore as a means to address not just immediate reliability concerns but also operations
issues like enhancing transfer capability in real time, advanced automatic corrective actions like
adaptive islanding, blocking/de-blocking of distance relay zones under power swings, better
visualization through state measurements, decision support tools etc.
The existing SCADA/EMS provides only the steady state view of the power system. These
systems take a minute to deliver a snap shot of a system whose characteristic are changing very
fast. In contrast to the conventional SCADA system where RTUs are used to acquire voltage,
current and frequency, Wide Area Monitoring system acquire current, voltage (both magnitude
and phase angle) and frequency measurement by phasor measurement and are also time
synchronised via Global Positioning System (GPS) receiver to a time resolution of 1 micro sec.
so that Real Time Dynamic State Measurements/Monitoring of System across the widely spread
grid is possible. The wide area measurement facilitates better, faster analyses of grid conditions,
which in turn provide operators with more time and more options to preserve system stability. It
also represents a quantum leap in the quality of data on which everyday operational decisions are
based. This will help in maintaining grid safety and security and will be a step towards intelligent
and self-healing grid. Deployment of this technology in Indian Power System has been
envisaged in the Report of Working Group on Power for 11th Plan, Government of India as well
as in National Electricity Policy.
The Synchrophasor initiatives in India started with the implementation of a very simple
project consisting of 4 PMUs and 1 PDC along with data historian and operator console in May
2010 in Northern Region. Subsequently, other pilot projects were taken up in different regions.
Later on these all projects were integrated at National level by providing a PDC at National level
in National Load Despatch Center located at Delhi.

40. 40
 Phasor and Synchrophasor Technology:
A phasor is a complex number that represents both the magnitude and phase angle of
the sine waves found in AC system as shown in figure.
Fig: 14 (Phasor representing magnitude & phase angle of sine wave of voltage or current)
Phasor measurements that occur at the same time are called "Synchrophasor" and can be
measured precisely by the Phasor measurement units (PMUs). PMU measurements are taken at
high speed typically 25 or 50 samples per second – compared to one every 4 to 10 seconds using
conventional technology. Each measurement is time-stamped according to a common time
reference. Time stamping allows phasors at different locations to be time-aligned (or
synchronized) thus providing a comprehensive view of the entire grid at central location.
A typical PMU installation as a part of wide area monitoring system (WAMS) network
consists of phasor measurement units (PMUs) dispersly placed throughout the electricity grid at
strategic locations in order to cover the diverse footprint of the grid. A Phasor Data Concentrator
(PDC) at central location collects the information from PMUs and provides alert and alarm for
emergency situations as well as facilitates development of different types of analytics for smooth
operation of grid on real time basis. The PMU data is also transmit to Supervisory Control and
Data Acquisition (SCADA) system after time aligning the same. The WAMS technology
requires high bandwidth communication network for rapid data transfer matching the frequency
of sampling of the PMU data.

41. 41
 Challenges:
Synchrophasor technology has many advantages, however implementing it on a large
scale also poses many challenges. In India, the project was first started on a pilot basis to obtain
initial experience of the technology and now it is being scaled up in the upcoming scheme
known as Unified Real Time Dynamic State Measurement Scheme (URTDSM Scheme). During
the execution of pilot projects many challenges were faced, which include:
 Selecting locations for PMU placements
 Type of architecture required
 Setting up of standards and compliances
 Ensuring interoperability of PMUs
 Availability and setting up of communication infrastructure
 Developing tools for in-depth post facto analysis
 Event Detection
 Developing lucid visualizations for system operators
 Integration of Synchrophasor technology with SCADA
 Cyber Security Management & Compliance
 Phasor Measurement Units (PMU):
PMUs installed for provide time stamped synchronized measurements to Phasor Data
Concentrators (PDCs) installed at Control Center at a reporting rate of 10, 25 and 50
frames/second. Most of the PMUs installed at EHV substations are reporting in IEEE C37.118-
2005 protocol combination of either One/Two sets of Voltage or one/two sets of Current signals.
Fig: 15 (PMU and GPS at Substation)

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 Phasor Data Concentrators (PDC):
The Phasor Data Concentrators receives data from various PMUs, aligns the received
data and forwards the aggregated data to real time applications.
Fig: 16 (PDC and Other Equipment at RLDC)
 PMU Data Visualisation:
Visualization is used for showing data to the control room operators in a
comprehensible way and has been extended to Control Rooms of the respective control centre.
This is used for real time monitoring through Synchrophasor data.
Fig: 17 (Data Visualisation in Control Room)

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 Location of PMUs in Eastern Region:
Fig: 18 (Location of PMUs in Eastern Region)

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METERING AND SETTLEMENT SYSTEM
 Introduction:
The settlement system is an important part in implementation of Availability Based
Tariff (ABT). The system involves metering, data collection and processing, energy accounting
and raising of bills of the constituents. This chapter indicates the roles and responsibilities of the
different regional entities in making the settlement system operative in most efficient manner.
 Special Energy Meter (SEM):
Regional Load Despatch Centres are responsible for scheduling and measuring power
within and across the regions. Measurement of electric energy is being carried out by interface
meters called Special Energy Meters (SEMs) installed at the peripheries of states and regions
according to Metering regulation notified by CEA. POWERGRID being Central Transmission
Utility (CTU) is responsible for installation of SEMs throughout the region and Eastern Regional
Load Despatch Centre is responsible for collection and processing the metered data.
Fig: 14

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 Metering and Data Collection:
o As per IEGC, the CTU shall install Special Energy Meters on all inter connections
between the regional entities and other identified points for recording of actual net
MWh inter-changes, average frequency on 15-minute time block and MVARh
drawls under low/high voltage conditions.
o The type of meters to be installed, metering scheme, metering capability, testing
and calibration requirements and scheme for collection and dissemination of meter
data shall be as per IEGC guideline.
o All concerned entities having SEMs installed in their premises shall fully cooperate
and extend necessary assistance by taking weekly meter reading and transmitting
them to ERLDC in time.
o All concerned entities having SEMs shall also carry out necessary time
adjustments in the meter as per the procedure already in vogue/advice of.
o In the event of any reported problem of SEMs as by ERLDC during processing in
the matter shall be reported to concerned / to the owner of the meter for necessary
replacement /repair.
 Data Processing:
o As mentioned in IEGC guideline all the energy meter data would reach ERLDC
by every Tuesday afternoon via email. The CTU/STU, ISGSs and regional entities
shall be responsible for sending of data of sending of data to ERLDC. ERLDC
would carry out data validation and in case of any problem, request any entity to
send the data again. Each entity would therefore have necessary backup of data at
their local PC level.
o The computation of the net injection of each ISGS and actual net drawl of each
beneficiary shall be carried out in line with IEGC based on the above meter readings
received at ERLDC. The preparation and issue of REA to the constituents shall be
done by ERPC Secretariat on the basis of meter data and implemented schedule
forwarded by ERLDC.
o Data related to the reactive energy exchange between two STU systems and
between STU and ISTS points would also be forwarded by ERLDC for preparation
of reactive energy accounts and communication to all constituent and ERLDC by
ERPC Secretariat.
o The final schedule implemented by ERLDC shall be open to all regional entities
for checking / verification for a period of five days and mistakes/omissions if any
would be rectified.

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 Energy Accounting:
ERPC Secretariat would process the information provided by ERLDC and other
utilities to determine the following energy accounts:
1. Monthly Regional Energy Account for the purpose of billing:
o Capacity charges payable by each beneficiary to each ISGS.
o Energy charges payable by each beneficiary to each ISGS
o ISGS energy scheduled for each regional beneficiaries.
In case of utilities outside Eastern regions are having shares on ISGSs, ERLDC shall be
furnishing consolidated schedule drawal at the concerned regional boundary/ies only.
2. Weekly Deviation Account:
Weekly Deviation charges shall be settled as per deviation calculation for each 15
minute block. The deviation charges payable/receivable shall be calculated with respect to
deviation Pool. The Pool Account shall be maintained by ERLDC. The deviation account as
prepared by ERPC Secretariat shall have the following components
o Deviation charges payable by beneficiaries/ISGSs/IPPs to Pool
o Deviation charges receivable by the beneficiaries/ISGSs/IPPs from the pool
o Additional Deviation charges payable by beneficiaries/ISGSs/IPPs to Pool
o Pool balance amount due to capping of deviation rate for Thermal ISGSs.
Since the hydro stations within Bhutan System is not covered under deviation
settlement mechanism, the accounting for drawal from these stations shall be as per the Monthly
energy account as per the agreed principles. However, deviations of injections from these
stations shall be accounted for and duly apportioning the deviations amongst its beneficiaries.
3. Weekly VARh Account:
The VARh account as prepared by ERPC Secretariat shall have two distinct
components.
o VARh charges payable/receivable for VARh exchange between STU systems
o VARh charges payable by Beneficiaries for low VARh drawal or High VARh injection
between STU and ISTS points.

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The VARh account for low VARh drawal and High VARh injection between STU and
ISTSs shall be maintained by ERLDC. Any payment to be made from VARh account shall be
discussed beforehand in ERPC forum.
4. Congestion Charge Account:
The Congestion Charge account is prepared by ERPC secretariat. There is a
congestion imposed on real time Grid Operation, Congestion Charge shall be applicable to
Regional entities as per the CERC (Measures to relieve congestion in real time operation)
Regulations and orders on rate of congestion charge as applicable from time to time. Congestion
charge would be levied for over drawal or under- injection in the importing control area and,
Congestion charge would also be levied for under drawal or over-injection in the exporting
control area.
5. Pool Account Operation:
In line with IEGC guideline, from the date of issue of weekly deviation account and
Reactive Energy Charge Account by ERPC Secretariat, within 10-days, the concerned regional
entity shall pay on priority the indicated amount into regional deviation, Reactive Energy and
Congestion charges accounts operated by ERLDC. The agencies that have to receive the money
from pool accounts would then be paid within 2 working days. These pool accounts are to be
reconciled once in periodic intervals (i.e. quarterly).

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CONCLUSION
An Industrial training has allowed the student to get an exposure for the practical implementation
to theoretical fundamentals, which would be of great use in coming future. It gives large
spectrum to utilize the theoretical knowledge and to put it into practice.
From this Internship we get a very good experiment about Power System Operation Corporation
Limited’s (POSOCO) operation as well as over view of Indian Power System. We will like to
conclude that POSOCO as well as Eastern Regional Load Dispatch Centre (ERLDC) has
provided us with the following opportunity:
 A comprehensive practical experience where learning is the primary objective of the
experience.
 A congenial and supervised field environment.
 An opportunity for us to gain better understanding about Power as a sector in general and
Power System in particular.
 To help us evaluate and determine future career opportunities.
 To develop skills and make connections, gain insights in to Corporate Sector.

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BIBLIOGRAPHY
 www.erldc.org
 www.posoco.in
 www.erpc.gov.in
 www.cea.nic.in
 www.powermin.nic.in
 www.cpri.in
 www.npti.in
 www.nldc.in
 www.wikipedia.org
 www.dvc.gov.in
 www.wbsldc.in