UNDERSTANDING SERIES CAPACITORS

Series Capacitors are generally applied to compensate the excessive inductance of long transmission lines, in order to reduce the line voltage drop, improve its voltage regulation, minimize losses by optimizing load distribution between parallel transmission lines, and to increase the power transfer capability. Similarly, series capacitors are also installed in electrical power systems to improve its voltage stability.

SHUNT CAPACITORS AND THEIR APPLICATIONS

Shunt Capacitors have several uses in the electric power systems. They are utilized as sources of reactive power by connecting them in line-to-neutral. Electric utilities have also connected capacitors in series with long lines in order to reduce its impedance. This is particularly common in the transmission level, where the lines have length in several hundreds of kilometers. However, this post will generally discuss shunt capacitors.

POWER QUALITY BASICS: VOLTAGE UNBALANCE

Voltage Unbalance (or Imbalance) is defined by IEEE as the ratio of the negative or zero sequence component to the positive sequence component. In simple terms, it is a voltage variation in a power system in which the voltage magnitudes or the phase angle differences between them are not equal. It follows that this power quality problem affects only polyphase systems (e.g. three-phase).

DYNAMIC VOLTAGE RESTORER (DVR)

DVR (Dynamic Voltage Restorer) is a static var device that has seen applications in a variety of transmission and distribution systems. It is a series compensation device, which protects sensitive electric load from power quality problems such as voltage sags, swells, unbalance and distortion through power electronic controllers that use voltage source converters (VSC). 

PSCAD – THE ELECTROMAGNETIC TRANSIENTS SOFTWARE

PSCAD (Power Systems Computer Aided Design) is a time domain simulation software for analyzing transients in electrical networks. It is a collection of programs, providing a graphical Unix-based user interface to electromagnetic transients program (EMTP). It is also known as PSCAD/EMTDC. EMTDC (Electromagnetic Transients with DC Analysis) was first developed in 1976 and has been constantly evolving in its scope and capabilities. It is an integral part of PSCAD as it is the library of power system component models and procedures, which establish the simulation software provided with PSCAD. Together they provide a fast, flexible and accurate solution for the efficient  time-domain program for simulating a variety of electrical power system transients and control networks.