an introduction to facts

An Introduction to FACTS

Presented by

T.S.L.V.AyyaraoAssistant Pofessor

GMRIT

Why do we need Transmission Interconnections?

Delivery of Electrical Power To minimize the total power generation capacity

and Fuel cost. To supply electricity to the loads at minimum cost

with a required reliability. Transmission is an alternative to a new generation

resource. Economic energy or reserve sharing is constrained

by transmission capacity


Can we use the full potential of Transmission interconnections?

As power transfers grow, the system becomes more complex to operate.

The power systems of today are mechanically controlled

If so what? Switching devices are mechanical and there is

little high speed Mechanical devices cannot be initiated frequently.


Mechanical devices wear out quickly. In view point of both dynamic and steady state

operation, the system is really uncontrolled. In recent years, power demand increases day by

day. Increased demand and absence of long term

planning leads to less security and reduced quality of supply.

Opportunities for FACTS

FACTS technology opens up opportunities to control power and enhance the usage capability of line

FACTS controller uses Control the current through the line at reasonable

cost. Enables the power to flow under normal and

contingency conditions To control the interrelated parameters (series

impedance, shunt impedance, current, voltage, phase angle)

Opportunities for FACTS

To damp oscillations at various frequencies below rated frequency.

Enable a line to carry power closer to its thermal rating.

Mechanical switching replaced with power electronics

Power Flow in an AC System

In ac system, the electrical generation and load must balance at all times.

The electrical system is self-regulating. If generation is less than load, voltage and

frequency drop. Active power flows from surplus generation areas

to deficit areas.

Power Flow in Parallel Paths

Power Flow in a Meshed System


A adjustable series capacitor controls the power flow

Mechanically switched series capacitor is limited by wear and tear.

A series capacitor in a line may lead to subsynchronous resonance.

This occurs when mechanical resonance frequencies of the shaft of a multiple turbine generator unit coincides with 50hz minus the electrical frequency of the line.


If series capacitor is thyristor controlled It can be varied as often as required Rapidly damp any sub-synchronous resonance

conditions Damp low frequency oscillations in the power

flow Avoid risk of damage to generator shaft and

system collapse Greatly enhance stability of the network.

Limitations of loading capability

For best use of transmission asset and to maximize the loading capability, what are the limitations?

There are three kinds of limitations Thermal Dielectric Stability


ThermalFor overhead line, thermal capability is a function of ambient

temperature, wind conditions, conditions of conductor, and ground clearance. The FACTS technology can help in making an effective used of newfound line capability.

DielectricBeing designed very conservatively, most lines can increase

operation voltage by 10% or even higher. FACTS technology could be used to ensure acceptable over-voltage and power flow conditions.


StabilityThe stability issues that limit the transmission capability

include: 1. Transient stability, dynamic stability, steady-state

stability, frequency collapse. Voltage collapse, and sub-synchronous resonance.

2. The FACTS technology can certainly be used to overcome any of the stability limits.

an introduction to facts

Engineering