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

Practical System

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.

Power 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

4.28 15.25 0.16 4.12 22.87 67.71 5.14 63.50 100.00 32.51 27.09 72.84 52.23 32.22 0.00 10.69 57.08 6.41

50.023 0.0375 0.0569 46.8 FDI: 36.5

Max 50.196 0:03:50 Max 50.132 0:15:00 198 0:02:47

Min 49.789 18:51:50 Min 49.854 19:00:00 79 0:03:48

135

133

Source : AGRA 10 Sec. (8640 samples)

<49.7

0.00

8:45:40

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 19-Jul-2021 (Monday)

0 10 20 30 40 50 60 70 80 90 100

49.75

49.80

49.85

49.90

49.95

50.00

50.05

50.10

50.15

50.20

50.25

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

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 the world.

I T& D losses are 21 %.

I However , the per capita energy consumption is 1,208 kWh perperson per year.

I It is low compared to many countries. For example, US : 12,154& China : 4,617

I It is even lower than the world average (3,081 kWh).

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

Installed Capacity

The installed capacity as on 31-05-2021 is approximately 383 GW.

Type Capacity (MW) % of TotalThermal 2(Coal, Oil & Gas) 234,728 61 %

Hydro 46,209 12 %

Nuclear 6,780 2 %

RES 95,656 25 %

Total 383,374

I The peak demand in May, 2021 was 184.503 GW.

I There was a deficit of 0.2 % .

Source : Central Electricity Authority, Ministry of Power, GoI

2Coal based power plants account for 90 %

Installed Capacity - Sector Wise

Private

48%

State

27%

Central

25%

Electricity Generation in May 2021

Total electricity generation in May 2021 was 118.09 BU.

Thermal

74%

Nuclear

3%

Hydro

11%

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

Course Mechanics

Since the semester is online, 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.