EE381 - Power Systems

S. Sivasubramani

Associate ProfessorElectrical Engineering Department

Indian Institute of Technology Patnawww.iitp.ac.in/~siva

Overview

Power Systems

Indian Power Sector - An Overview

Syllabus

Books

Course Mechanics

Power Systems

Power systems have the following three components.

1. Generation - Source of Energy

2. Transmission - Transmission of Energy over long distance(close to the speed of light)

3. Distribution - Consumption of Energy

I Electric Energy is seldom used in its form.

I It is easy to convert from other forms and transmit fromsources to loads.

I Power system is the most complex system on earth.

I In interconnected systems, the frequency has to be the same.In India, it is 50 Hz. In some countries, it is 60 Hz.

Generation

Electric energy is generated at generating stations by convertingother forms of energy.

1. ConventionalI ThermalI Hydro (Renewable)I Nuclear

2. Non Conventional (Renewable)I SolarI WindI BiomassI TidalI Geo-ThermalI Small HydroI Waste

Renewable Energy Sources (RES)

RES have unlimited resources. But they are intermittent.

Structure of a Power System

T1

Transmission LineG

T2 T3

DomesticCustomers

CommercialCustomers

Sub Transmission LineIndustrial Customers

Interconnected Systems

Reasons for interconnections

1. To improve reliability

2. To improve economy

I Several power systems are interconnected to form a grid.

I Several regional grids are interconnected to form a nationalgrid.

I Interconnections are done at Transmission networks.

I In interconnected systems, the frequency of generation mustbe the same.

Practical System

Source : NPTEL

Grid Frequency

<49.90 <49.97 49.7-49.8 49.8-49.9 49.9-50.0 50.0-50.1 50.1-50.2 49.90-50.05 49.7-50.2 49.97-50.03 50.05-50.1 >50 >50.03 >50.05 >50.2 <49.95 49.95-50.05 49.90-49.95

4.38 31.17 0.12 4.26 47.87 47.34 0.42 86.03 100.00 45.25 9.26 47.72 23.58 9.59 0.00 19.81 70.59 15.44

49.991 0.0259 0.0501 46.3 FDI: 14.0

Max 50.128 14:02:20 Max 50.078 14:15:00 176 0:03:29

Min 49.779 18:25:30 Min 49.887 18:30:00 129 0:01:56

177

176

Source : NTPC-VINDHYACHAL:Frequency 10 Sec. (8640 samples)

<49.7

0.00

3:21:10

Instantaneous Frequency 15 minute Average Frequency No. of excursions Average time freq per excursion remains

above 50.03 Hz below 49.97

below 49.97 Hz above 50.03

above 50.00 Hz

below 50.00 Hz No. of hours freq outside

49.9-50.05 Hz

Average Frequency : Frequency Variation Index : Standard Deviation : Mileage:

POWER SYSTEM OPERATION CORPORATION LIMITED

NATIONAL LOAD DESPATCH CENTRE, NEW DELHI

Frequency profile for 16-Aug-2020 (Sunday)

0 10 20 30 40 50 60 70 80 90 100

49.70

49.75

49.80

49.85

49.90

49.95

50.00

50.05

50.10

50.15

50.20

50.25

50.30

00:0

0

01:0

0

02:0

0

03:0

0

04:0

0

05:0

0

06:0

0

07:0

0

08:0

0

09:0

0

10:0

0

11:0

0

12:0

0

13:0

0

14:0

0

15:0

0

16:0

0

17:0

0

18:0

0

19:0

0

20:0

0

21:0

0

22:0

0

23:0

0

Duration (Percentage of time)

Freq

uen

cy (

Hz)

Source : POSOCO

Indian Power Sector - An Overview

I India is the third largest producer of electricity (more than 1TU1 a year) in the world.

I India is also the third largest consumer of electricity in theworld.

I However , the per capita energy consumption is 1,181 kWhper person per year.

I It is low compared to many countries. For example, US :12,071 & China : 4,475

I It is even lower than the world average (2,674 kWh).

11 TU = 1,000,000,000,000 kWh

Installed Capacity

The installed capacity as on 30-06-2020 is 371.054 GW.

Type Capacity (MW) % of TotalThermal 2(Coal, Oil & Gas) 230,906 62.3 %

Hydro 45,699 12.3 %

Nuclear 6,780 1.8 %

RES 87,669 23.6 %

Total 371,054

I The peak demand was 165.434 GW in June 2020.

I The peak demand met was 164.946 GW in June 2020.

I There was a deficit of 0.3 % .

Source : Central Electricity Authority, Ministry of Power, GoI

2Coal based power plants account for 90 %

Thermal

62.3%

Hydro

12.3%

Nuclear

1.8%RES

23.6%

Installed Capacity - Sector Wise

Private

47%

State

28%

Central

25%

Total Generation in June 2020

Total electricity generation in June 2020 was 112.90 BU.

Thermal

69%

Nuclear

3%

Hydro

16%

Renewable

12%

Most of the energy is still from Thermal.

Thermal Power Plant

What We will study in EE381..

We will analyze power systems under

I steady state conditions

I abnormal conditions

In order to analyze, every component of power systems has to bemodeled.

I Generator

I Transformer

I Transmission line

I Load

Since the steady state model of synchronous machines andtransformers have already been studied in EE280, we will onlymodel the following in this course.

I Transmission line

Loads are usually considered as

1. Constant power

2. Constant impedance

3. Constant current

We usually simplify any analysis at the cost of accuracy....

Syllabus

I Basic Concepts

I Line Parameter Calculation

I Performance of Transmission lines

I Per unit calculation

I Network Matrices

I Load Flow

I Economic Dispatch

I Fault Analysis

I Power System Stability

Books

Text Books:

1. W. D. Stevenson, Jr., “Elements of Power System Analysis”,Tata McGraw-Hill, 4e, 2008.

Reference Books:

1. J. J. Grainger and W. D. Stevenson, Jr., “Power SystemAnalysis”, Tata McGraw-Hill, 2008.

2. D. P. Kothari and I. J. Nagrath, “Modern Power SystemAnalysis”, Tata McGraw-Hill, 3e, 2010.

Course Mechanics

Due to Covid-19, the following pattern may be adopted.

I Five Quizzes - 40 %

I Mid Sem (Assignment)- 25 %

I End Sem (Mostly Assignment) - 25 %

I Attendance and Sincerity - 10 %

Course Page

Refer to my web page.