CLASSIFICATION OF TRANSMISSION LINE

Classification of Transmission Line
There are three major approaches in analyzing transmission
lines in a power system, the Short, Medium and
Long transmission line analysis.

These three classifications affects the analysis since certain electrical parameters are considered which differ from one to the other. According to the book of William Stevenson Jr. entitled "Elements of Power System Analysis", in an open wire 60hz line, it is said that;

Short Lines is less than about 80 kilometers (50miles).
Medium Lines are between 80 kilometers (50 miles) and 240 kilometers(150 miles)
Long Lines are longer than 240 kilometers(150 miles).

In an overhead lines that is classified as short, the major line parameters that are considered is the series resistance and the series inductance of the line. The power dissipated in this two parameters practically also represents the line loss of the conductor. Shunt capacitance is not considered in the analysis of short lines since the absence of it creates a little loss of accuracy.

SHORT LINE ANALYSIS

Medium line on the other hand considers the shunt capacitance in the analysis. Two types of analysis are usually done with medium length transmission lines. The pi network and the T network. In a pi network, the line impedance R & L are lumped in the middle of the line which represents that it is uniformly distributed along the line. With it the shunt capacitance are divided in to two, the first half is found in the sending end while the other is at the receiving end. While in the T network, the opposite is usually done. In a T network, the shunt capacitance are lumped in the middle of the line and the total line impedance is equally divided into two along the each side of the network.

PI NETWORK FOR MEDIUM LINE ANALYSIS

T NETWORK FOR MEDIUM LINE ANALYSIS

Lastly, when the transmission line is over 240 kilometers and that the analysis now requires a high degree of accuracy, long line analysis is practically used. However, we shall not dwell so much with these analysis and the primary objective of this discussion is to refresh your ideas about transmission lines.

Comments

PARTS OF A POWER TRANSFORMER

What are the name of the basic parts of a Power Transformer? We can not deny the fact that only a handful of electrical engineering students are presently familiar with power transformers especially on what it looks like. Unlike a transformer we found in our homes, a power transformer’s appearance and construction is somewhat more complicated. It is not just a simple winding with a primary and secondary terminal although basically any transformer has one. The function that a power transformer plays in an electrical system is very important that an electric utility can not afford to loss it during its operation. Our discussion here will focus more on the basic parts and functions of a power transformer that are usually tangible whenever you go to a substation . Although not all power transformers are identical, nonetheless they all have the following listed parts in which the way of construction may differ.

click here to continue

ELECTRIC MOTOR FRAME SIZE STANDARD SPECIFICATIONS

ELECTRIC MOTOR FRAME SIZE STANDARD SPECIFICATIONS How is electric motor frame size being specified? Motor frame dimensions have been standardized with a uniform frame size numbering system. This system was developed by NEMA and specific frame sizes have been assigned to standard motor ratings based on enclosure, horsepower and speed. The current standardized frames for integral horsepower induction motors ranges from 143T to 445T. These standards cover most motors in the range of one through two hundred horsepower. Typical example of where you can locate the frame is shown in Fig 1.2.D – Frame No. The numbers used to designate frame sizes have specific meanings based on the physical size of the motor. Some digits are related to the motor shaft height and the remaining digit or digits relate to the length of the motor. The rerate, or frame size reduction programs were brought about by advancements in motor technology relating mainly to higher temperature ratings of insulating mate...

click here to continue

ELECTRIC MOTOR NAMEPLATE SPECIFICATIONS

How do we interpret an electric motor nameplate? Motor standards are established on a country by country basis.Fortunately though, the standards can be grouped into two major categories: NEMA and IEC (and its derivatives). In North America, the National Electric Manufacturers Association (NEMA) sets motor standards, including what should go on the nameplate (NEMA Standard MG 1-10.40 "Nameplate Marking for Medium Single-Phase and Polyphase Induction Motors").

click here to continue

power systems loss

Search This Blog