POWER SYSTEM OPERATION AND CONTROL

S.H.ABIDI

STRUCTURE

Despite having installed power generation capacity of 225 GW and power demand of 135 GW (as of May 2013).

India faced a peak power deficit of 9% (12 GW) Power shortages have adversely affected the

country's economy. In 2012-13, power shortages in India accounted for a 6 GDP loss of USD 68 billion (0.4% of GDP) .

Impacting multiple industries like agriculture, manufacturing, services etc. Improvement of this

sector is essential for the economic well-being of the country and enhancement of the quality of life

of citizens.

Current Scenario

In the last 5 years, power generation capacity has grown by ~50%, whereas transmission capacity has increased by ~30% .

As per the 12th Five Year Plan(2012-2017), the future expansion in power generation capacity in India is planned around 88GW

Future Plans

In order to meet this capacity, investment in the transmission sector needs to be increased. Overall, an addition of 90,000 km of 765-220 kV lines.

154,000 MVA of substation capacity and 27,350 MW of national grid capacity is required in order to meet the 12th Five Year Plan .

For this purpose, an investment of USD 35billion is planned in the power transmission sector. Of this, about USD 19 billion is planned to come from Power Grid Corporation of India Limited .The remaining USD 16 billion,~46% of the total investments, needs to be secured from private players.

• Grid management on regional bases was started in mid 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 .

Power Grid

•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

National Grid

NEW Grid

SouthGrid

South

West

North

East

Northeast

Five Regional GridsFive Frequencies

October 1991East and Northeast

synchronized

March 2003West synchronized

With East & Northeast

August 2006North synchronized

With Central Grid

Central Grid

Five Regional GridsTwo Frequencies

3.2 Million Sq. Km Area

Installed Capacity 211 GW

The current frequency band is between 49.7 Hz and 50.2 Hz.

The country’s apex power sector regulator has suggested a grid frequency band of 49.5Hz and 50.05Hz

Peculiarities of Regional Grids in India

SOUTHERN REGION

WESTERNREGIO

N

EASTERN REGION

NORTHERN REGION NORTH-

EASTERN REGION

REGIONAL GRIDS Deficit Region

Snow fed – run-of –the –river hydro

Highly weather sensitive load

Adverse weather conditions: Fog & Dust Storm

Very low load

High hydro potential

Evacuation problems

High Industrial load and agricultural load

Low load

High coal reserves

Pit head base load plants

High (40% agricultural load)

Monsoon dependent hydro

CHICKEN-NECK

10

X

SinEEP

212

21

1

X

SinEEP

Reliability

Economy

Instability

Advantages And Disadvantages of Interconnected System

The System must be able to meet the continually changing load demand for active and reactive power.

The system should supply energy at minimum cost and with minimum ecological impacts.

The “quality “of power should meet certain minimum standards .

Operational objectives

Definition of States and control actions

System operation in steady state is governed by equations which express:

1. Real and Reactive power balance at each node(Equality Constraints)

2. Limitation of physical equipment, such as current and voltages must not exceed minimum limits(Inequality constraints)

A normal(secure)state is the ideal operating condition, wherein all the equipments are operating within their design limits and the demanded load is being met.

Power system can withstand a contingency without violation of any of the constraint.

Power system is secure.

States of Power System

The System enters the alert state if the security levels falls below a certain limit of adequacy or if the possibility of a disturbance increases because of adverse weather conditions such as the approach of severe storms.

•If the disturbance is very severe ,the extremis state may result.

•The system enters the emergency state if a sufficiently severe disturbance occurs .

•The restorative state represent a condition in which control action is being taken to connect all facilities and to restore system

Power system Operating states

AlertRestorative

In extremis

Normal

Emergency

Transition from Alert to Emergency state

Hierarchy of control

•Energy Control Centre

•Generating Unit control

•Transmission control

•The Scheduling of references of many controllers are set by Energy Control Centers.

•The scheduling of references may have economic and technical consequences.

•The ownership of generation, transmission and distribution may be with different entities.

•There may be more than one energy centre but a certain hierarchy is strictly defined.

Thank You