Porcelain insulators (bell type) were first created in 1849 by Werner von Seimens. Porcelain Insulators was originally used for insulation of telephone lines. Since then, porcelain insulators have evolved and has found vast usage especially in the transmission lines system acting as insulators.

Porcelain Insulators have two basic purposes on transmission lines:
1.To support conductors and attache them to structures
2.To electrically isolate conductors from other components on a transmission line
The second purpose is very important to operation since without some form of insulating material, electrical circuit cannot operate.

To be able to isolate conductors, insulators must be made of materials that offer a great deal of resistance to the flow of electricity. Porcelain is one of the most highly used insulator type along with glass and other synthetic materials.

Porcelain is a multiphase ceramic material that is obtained by heating aluminum silicates until a mullite phase is formed. Mullite us porous, its surface must be glazed with a high melting point glass to render its smooth and impervious for use in overhead line insulators.

Porcelain insulators, like any insulators come in a variety of different shapes and sizes, to accommodate the insulator rating as well as its usage.
Insulators are rated in terms of its electrical and mechanical handling capabilities.

Voltage Level
Low Frequency Dry and Wet Flashover
Positive and Negative Impulse Flashover

Cantilever Strength
Tensile Strength
Combined M&E Strength
Maximum Working Load

As for its usage, there are three types of insulators typically found on transmission lines. They are pin insulators, post insulators, and disc insulators.

Pin Insulators

Are generally designed for use on lower range of transmission voltages. Pin insulators are mounted on poles or cross arms using an insulator pin, made up of metal or wood. Pin insulators are always designed to support a conductor upright or vertical on top.

Post Insulators

Post insulators can be mounted vertically on the tops of poles or cross arms or horizontally on the side of the pole.

Disc Insulators

Disc insulators can be connected together in strings to accommodate the requirements of any transmission voltage. They are usually bell shaped, and have mechanisms on the top and bottom for connecting.


The Right of Way
Before we are going to discuss the classification of power lines, it is good to be acquainted with the concept of the Right-of-Way. Transmission lines are normally constructed on a tract of land known as right-of-way. In most cases, only one type of structure is used on a right-of-way. But there are also instances wherein different types of structures and different types of lines are being put.

A right-of-way may follow a straight path, or may change direction in order to avoid obstacles, which happen in many cases. This change in direction causes strain on structures, and the need to compensate from these strains causes the emergence of much type of Transmission Line Structures.

The general types of structures used on transmission lines are wooden poles, concrete poles, metal or steel poles, and lattice towers. These structures can be classified as tangent, angled, or dead-end structure, depending on how it is used in a line.

Dead-End Structures
Dead-end structures, or strain-termination structures, are used wherever a transmission line ends. It is specifically designed to withstand relative greater deal of stress and strain. Dead-end structures at the end of a transmission line are generally identified by insulator strings in the strain insulators.
Dead-end construction may also be found within transmission lines at any point where excess strain is placed on the structures or its components. Example of these is double dead-end, wherein it supports strain of each phase of a line in two directions.

Angle Structures
This structure type is used at points where a transmission line undergoes a significant change in direction. Angle structures are specially reinforced to withstand the strain placed on them by changes in direction.

Tangent Structures
This type is the most commonly used structure type on a transmission line. It is also called as straight-through/ along the line construction. It is generally located on relatively straight portions of a right-of-way.
Tangent structures must be capable of supporting each phase of a transmission line as it passes from one structure to the next. In most cases, the insulator strings on the tangent structures are mounted in the suspension position.

Factors Affecting Transmission Line Design
All of those transmission line structure types can be found on virtually any transmission line. Where and how particular structures are used depends on many factors. Some the more important factors are the following:

1. Ground Clearance
2. Load Requirements
3. Type of Terrain
4. Span Length Conductors
5. Weather Conditions


Power Cable Capacitance (C) Formula
Single Conductor Shielded Cable
        C = 0.024113 x e/ [log (d2/d1)]   microfarad/ kilometer
e = dielectric constant for XLPE = 2.3, PVC = 5.0-7.0
d2 = diameter under insulation
d1 = diameter over the insulation

Power Cable Insulation Resistance (IR) Formula
According to ICEA Specification
IR @ 15.6 degrees C = K log (d2/d1)    Megaohm - 1000ft

According to JIS Specification
IR @ 20.0 degrees C = 3.665 x 10^-12 x p x log (d2/d1)    Megaohm - km

d2 = diameter under insulation
d1 = diameter over the insulation
K = constant (XLPE = 20,000; PVC = 500)
p = volume density (ohm-cm) ; XLPE = 2.5 x 10^15, PVC = 1 x 10^13

Power Cable Inductance (L) Formula
Multiple conductor cable or single conductor cable arranged in parallel and three single conductor arranged in triangular
          L = 0.46 log (S/d) + 0.19    mH/km
d = diameter of conductor
S = distance between conductor

Power Cable Charging Current (Ic) Formula
          Ic = 2 x pi x fC x v/ 1.73    Amp/km
C = capacitance (F/km)
V = rated line to line voltage (Volt)
f = frequency (Hz)

Power Cable Potential Gradient Formula
         E = (v/1.73)/ X ln (d2/d1)    kV/mm
X = distance from center of the conductor (mm)
V = rated line to line voltage
d2 = diameter under insulation
d1 = diameter over the insulation


Toroid Transformers and Its Concept

Toroid transformers, also called as Toroidal Transformer or Toroidal power supply are transformers having the shape of its core different than the conventional ones. Toroid transformer's core, as the name implies are toroids or called as Toroid Cores.
Toroids are ring-shaped surface generated by rotating a circle around an axis that does not intersect the circle. It is a doughnut-shaped object enclosed by a torus.


Learn the hows and whys behind basic electricity, electronics, and communications without formal training
The best combination self-teaching guide, home reference, and classroom text on electricity and electronics has been updated to deliver the latest advances. Great for preparing for amateur and commercial licensing exams, this guide has been prized by thousands of students and professionals for its uniquely thorough coverage ranging from DC and AC concepts to semiconductors and integrated circuits.


Transmission Lines Voltage Evolution and Selection
Electricity has been used as a major energy source since the late 19th century. The first three phase alternating current transmission started in 1891, a 175 km long line supplying electricity to an electrical engineering exhibition in Frankfurt and Main Germany. A power of about 200 kW was transmitted by this line operating at 40 Hz.

Since then, the selection of transmission voltage have evolved to facilitate the needs and requirements of the user. The evolution of voltage levels and other milestones can be seen below:


OPGW or known as Optical Ground Wire is a type of cable or wire that is used in transmission lines construction. It is also known as optical fiber composite overhead ground wire. It can serve as a grounding wire, shielding wire, and at the same time a cable used for communication purposes. 

OPGW contains a tubular structure with one or more optical fibers in it. It is then surrounded by layers of steel and aluminum wire. It can be compared like an ASCR, except that steel is the one covering the tube with fiber optics inside.


Transmission and Distribution Electrical Engineering is the engineer’s handbook to real-world power engineering practice – a unique working reference for the engineer, technician, systems planner and manager

Most books on transmission and distribution electrical engineering are student texts that focus on theory, brief overviews, or specialised monographs. Colin Bayliss and Brian Hardy have produced a unique and comprehensive handbook aimed squarely at practising engineers and planners involved in all aspects of getting electricity from the power plant to the user via the power grid.


The Electrical Engineer's Handbook is an invaluable reference source for all practicing electrical engineers and students. Encompassing 79 chapters, this book is intended to enlighten and refresh knowledge of the practicing engineer or to help educate engineering students. 



The longest single span in a transmission line in the world is found in Greeanland. We've already talked about the longest transmission line in terms of circuit kilometers on this blog entry. This is for the distinction in a single span.


Transmission Planning is purposed to define a transmission system or its expansions as to comply with the electric energy demand at specified quality and reliability criteria at a minimum cost. Planning process should be continuous, should have an interactive structure as to make an optimized future evolution use.

The planning studies take a leading role in the definition of an electric system or its expansion. The planning activities have to start several years before the installation of new or expansion of existing transmission lines is to be implemented.

Planning Stages of Transmission Lines

1. Long Term Planning - It defines the basic future structure of an electric system. It comprises a long term horizon for the system planning usually in the range of 15-30 years.

2. Medium Term Planning - Its target horizon is in the range of 10-15 years. It usually defines the basic characteristic of the system such as voltage, main transmission lines  and substations.

3. Operation or Short Term Planning - The horizon to be analyzed is usually below three years and urgent requirements of the system. These includes but not limited to the anticipation of operation dates of new facilities, needs to uprate or upgrade existing lines, or load transfers in scheduled interruptions.

Note: Planning should be continuously revised depending on the variation that can occur in the economic environment, the energy market, energy industry, or in the generation program.

Planning Aspects Regarding Transmission Lines

Planning Studies should answer the following questions:
When will a new transmission line, or uprating, or upgrading of existing lines will be required?
Where is it required and what quality of supply or reliability is required?
What normal and emergency ratings are required?
What type of transmission should be used? (Overhead, underground, AC or DC?)
What voltage and how many circuits will be needed?

Transmission Lines Planning Criteria

The basic criteria that should be established in a system planning is that no load can be lost under occurrence of a simple contingency in the system being studied or in another neighboring interconnected system.

Steady State Condition Criteria
The system must be tested for heavy load and light load conditions. It should support the outage of any of its components, also known as n-1 criterion.

Load flow studies parameters are as follow:
Voltage range should be between 0.95 and 1.05 p.u.
Transformer loads: Normal conditions: no overload
                             Loss of a transmission line or generator: 20% overload
                             Loss of a transformer: 40% overload

Temporary and Transient Condition Criteria
System stability is required under any load condition in case of phase to ground short circuit without reclosing, considering the loss of one of the system components.

Temporary over voltages should not cause damage to any system equipment. The maximum allowable temporary over voltages are in the range of 140% in points with saturable equipment and 150% in other points.

Short Circuit powers and currents have to be assessed as accurately as possible in order to prevent exceeding the equipment capacity of the system and installations.


How to Conserve Energy and Save Money in the Process?

Energy Conservation is a paramount duty of everyone. We know how much estimated electrical energy is consumed by the world from my previous entry. It also directly related to how much resources utilized and how much waste is emitted to the environment. In short, everyone must act and think of energy conservation.

Whenever you save energy, you not only save money, you also reduce the demand for such fossil fuels as coal, oil, and natural gas. Less burning of fossil fuels also means lower emissions of carbon dioxide (CO2), the primary contributor to global warming, and other pollutants.


Yup, you read it right. This is about the World's Longest Overhead Transmission Line as of today. It is around 1700 km in length, transmitting power of 560 MW. Interestingly enough it its transmission voltage is 500 kV dc, mainly due its relatively long distance.


Aluminum Conductor Steel Reinforced (or ACSR) cable is easily the most used type of cable in overhead power lines in the last century. It is a specific type of high-capacity, high-strength stranded cable used in overhead power lines where the outer strands are aluminum, chosen for its excellent conductivity, low weight, and low cost. Its center strand is of steel for the strength required to support the weight without stretching the aluminum due to its ductility. Thus the name steel reinforced. 


Conductor, classified further as wires or cables is one of the major components of your transmission lines system. A conductor is a material that facilitates the flow of electricity (or electric current) in our transmission line.

Different types of conductors are used in transmission lines. They vary in number and size, depending on the type of circuit and the transmission voltage. Steel, aluminum and copper are the most common conducting materials used in transmission lines.


PLS CADD ( Power Lines System – Computer Aided Design and Drafting) is a computer software that enables you to design, simulate, and analyze the behavior of a transmission and distribution system. It is owned and developed by Power Lines System, from which the name was derived. It is the most popular tool in transmission lines design, and fast becoming (if not yet) an industry standard.


Ohms Law is the basic of anything that has something to do with electrical engineering and electricity. It is a mathematical expression of the relationship between, the current, voltage, and resistance. Every equation and law in electrical engineering would be explained at the simplest sense, and would all boil down to Ohm's Law.

Ohms Law states that the current is directly proportional to the impressed emf applied to the circuit, and is inversely proportional to the resistance of the said circuit. This mathematical equation is conveniently represented by only three letters:

I = E/R
Where; I - current
E - voltage
R - resistance

Ohms Law was named after one of our Electrical Engineering Heroes, Georg Simon Ohm.

Enter two known values and press Solve to calculate unknowns.




Ohm's Law Components

Current or electric current is the motion of the electrical charges brought upon by a potential difference. It's unit is in ampere, named after Andre M. Ampere. One (1) ampere unit is equivalent to one coulomb of charge, passing a point in one second.

Impressed Electromotive Force (EMF), also called as Potential Difference, or simply voltage, is the capability of doing work, expressed in Volts. It is named after Alessandro C. Volta. One (1) unit of volt is equal to one Joule of work done per coulomb of charge.

Resistance is the inherent opposition of the conductor where the work  (one joule per coulomb) has to be done. Factors that determines the resistance aside may be its resistivity, area, length, and temperature.

Ohm's Law Sample Calculation and Practical Usage

a. A load of 10 ohms is connected to a source with 120 volts. What is the current drawn?
From ohm's law, I = E/R
    I = 120/10 = 12 amps

There you go. We hope that we gave you even just a little idea about Ohm's Law.
You may also visit recommended websites if you want to know more about one of the most important law in electricity, Ohm's Law.

Ohm's Law Calculator = http://www.the12volt.com/ohm/page2.asp http://www.allaboutcircuits.com/vol_1/chpt_2/1.html http://www.electronics-tutorials.ws/dccircuits/dcp_2.html


Daily electrical energy consumption of the world is quite an intriguing idea. But how exactly would you dtermine the daily electrical consumption of the world. On this feature, we try to estimate, and put into context the daily energy consumption of the world.


On this post, i will share to you a sample of a .bak file. Vertical dead end construction using strain insulators.

Download link is ==>HERE


Voltage Surge is an abnormal conditions on the Electrical Power System, characterized by voltage spikes. These usually refers to acute to extreme high voltages that is experienced by the power equipment.

Voltage surges could be transients or sustained. Whichever is the case, this could do harm to the electrical equipment or even your household appliances. Frequent transient surges and sustained over voltages is typically not good and should be kept minimal if not totally prevented. This will damage the insulation of such, and could result in electric flashover, which could not only do harm on the equipment but to lives as well.

Voltage Surges Causes

Common causes of voltage surges are; lightning and switching. Switching surges can be produced by the repeated igniting and extinguishing of electric arcs. Such voltage surges are obtained, for example, in disconnecting unloaded lines or by the grounding through an arc of one of the phases of a three-phase system with an insulated neutral conductor.

Lightning surges are voltage surges that are associated with lightning discharges either directly into the current-carrying parts of electric equipment (direct-strike surges) or into the ground adjacent to the equipment (induced surges). In a direct strike all of the lightning current passes into the ground through the struck object.

Voltage surge protection and suppression is one of the main engineering field of specialty in Electrical Engineering. One of the most important aspect in fact is called, insulation coordination.

For more on voltage surges and how to protect your equipment from it, you may refer to these articles:

Voltage Surge Effect on Motors
Damage from Voltage Surge 
Specifications of Voltage Surge Supressor
Transient Surge Protection for Low Voltage


On this second part, I recommend you to read this wonderfully written article about substation grounding by ECM. This article would answer some of the most common questions related to grounding like step and touch potentials, and the difference between mechanical boding and exothermic welding.

Full article may be found ==> HERE

For other free ebooks, pdf, tutorials, and links about substation grounding, click on the links below:





One of the must haves in relations to substation grounding for ANSI standards followers:
Guide for Safety in Ac Substation Grounding-Standard 80-1986


Grounding is one of the most important yet most misunderstood part of power engineering. In essence, grounding is important since it is involved in the protection of both lives and equipment during abnormal condition.

If your grounding system is properly designed and installed, then most likely it will have a reliable performance. Fast clearing of faults, made possible by good grounding, improves the overall safety and reliability of an electrical system. Therefore, substation reliability must be as "built-in" as possible because of the high available fault current levels present and unlikely occurrence of follow-up grounding inspections.

With these things in mind, I am going to share to you, some of important free e-books, tutorials, links and pdf related to substation grounding. Click on the links below:

Better Grounding Techniques

Fence Grounding Reference

Ground Fault Testing

Grounding Book

Other equally interesting and important grounding references:

Guide to substation grounding and bonding for mine power systems

Guide for Safety in Ac Substation Grounding-Standard 80-1986

Connectors for Electrical Construction and Maintenance: Distribution, Substation, Grounding - Aluminum and Copper Miniature Catalog

Analysis Techniques for Power Substations Grounding Systems (Design Methodology and Tests, Volume 1)


Hello there. On this blog, i will try to compress and collect any available engineering jobs out there with emphasis on the entry level.







note: I am in no way related to these job hiring poster.



For purpose of practice, I am giving a sample .bak file of the structure with 2-part insulators. Please do note that you may only use it as a guide in making models as some of its values were used only for illustrative purposes. You are encouraged to improved on it and do anything on it.

I do appreciate feedbacks and comments though, as well as suggestions to improve upon.

The Download link ==>> HERE



On this tutorial, we are to model a structure that is consisting of a steel pole, with construction made up of 2-parts insulators.
To model a steel pole, you may refer to this tutorial.  ==>> HERE
To model a two part insulator, you may refer to this tutorial. ==>>HERE

We will model the structure from a drawing to a .pol PLS-POLE file that we can use for analysis and use in PLS-CADD software as well.

Tutorial is found ==>> HERE



On this tutorial, we are going to create or model a braced post insulator using PLS-POLE. It is a 2-part insulator consisting of a post insulator supported by suspension insulators.

Some of the characteristics of a braced line post are:

  • It uses a traditional fixed base line post.
  • The longitudinal strength is limited to the RCL rating of the line post component.
  • It generates high tower torque (Z-direction) under longitudinal loading.
Tutorial can be downloaded ==>> HERE


Submarine cable and the world's longest submarine cables were already discussed beforehand. One might wonder, what is the longest communication submarine cable in the world?

The distinction goes to, FLAG (Fiberoptic Link Around the Globe), the system is organized, designed and priced to compete in the rapidly growing wholesale market for international telecommunications traffic. It is the longest man-made structure ever built, stretching 28,000 kilometers (17,000 miles) from the United Kingdom to Japan and linking Europe and Asia by way of the Middle East.

FLAG can transmit more than 10 gigabits of digital information per second -- the equivalent of 600,000 simultaneous conversations -- over two fiber pairs. Further technical advances, including Wavelength Division Multiplexing, give FLAG the potential to double the capacity of most segments.

 FLAG construction was built on time (in 27 months) and within budget, at a capitalized cost of approximately $1.5 billion. And, unlike traditional cable systems, the entire FLAG system is monitored continuously from a single network operations center, which is located in the United Arab Emirates.

Complete Info May be found HERE


What is the World's Longest Submarine Power Cable

Submarine cable system is one of the most common engineering solutions when distributing power or information in areas that are bounded by bodies of water, wherein overhead system is no longer practical. (More info in here). But have you ever wonder what is the longest submarine power cable that is operating today?


One of the most challenging tasks in the effort to distribute power, is to transmit when the area is bounded by bodies of water. Examples of this are island states or countries, and their connection to the power grid, as to support their island mode generating capacities.

Under normal circumstances, long distances and the presence of water beneath limits the practicality of putting overhead lines for the purpose. Thus, most of the time, engineers and builders turn to submarine cables.

Submarine cables are cables that are laid beneath the sea, or any bodies of water to carry or transmit energy, data or both. It can be classified into Submarine Communication Cables or Submarine Power Cables.

Typical cross section of a submarine cable is wonderfully illustrated by this picture courtesy of http://www.mutual-energy.com/The_Moyle_Interconnector/History_and_Development_of_the_Interconnector.php
For more on submarine cables, check and click on these highly recommended free tutorials, free links, and submarine cables pdf:

You may also check this equally interesting links:



George Simon Ohm, the man behind the ohm's law is today's EE hero. The unit of resistance (electrical) is named after this man.

Georg Simon Ohm was born in Erlangen, Bavaria, on March 16, 1787. He first published the theory behind ohm's law in the book, Die galvanische Kette Mathematisch Bearbeitet. He may have died in 1954, but his works, and the ohm's law itself is mentioned and is being applied everyday.

Everyone who is into Electricity and Electrical Engineering knows how important Ohm's law is. It is the single mathematical equation that describes the basic relationship of electricity and its elements. At its purest form, it is composed of only three figures; V=IR. It means that, the current flowing in the medium is directly proportional to the voltage and is inversely proportional to the resistance. Ohm's Law (V=IR) is as basic to the study of electronics, as Newton's Law (F=mA) is to classical physics. For that, we need to thank Geroge Simon Ohm.

Yet, its beginning is somehow far from easy. In fact, early scientists, his colleagues apparently dismissed his work, causing him both poverty and humiliation. During his time, the approach to physics are less mathematical, and George Simon Ohm is one of those who used mathematics. For this, he was an outcast, and died a poor man.

But today, George Simon Ohm could proudly say that he was, and is right all along.

For more about our Engineering Hero, please refer to these free sites:



Other Interesting Links
Ohm's Law, Electrical Math and Voltage Drop Calculations
Ohm's Law Experiment Kit
T-Shirt - Ohm's Law


Protective relaying is one of the most important and highly technical fields in electrical engineering. It is so critical, since it involves the protection of our power system to abnormal conditions that might be subjected to our power equipments and apparatus. It is practically, system protection.

Our power system, composed of our power equipment, transformers, generators, and transmission lines cost a fortune to construct and maintain. It is not rare to see generating plants, and power substations to cost in millions of dollars. Through an intricate manner, a device is used to act as an eye and brain in the protection system. They are called protective relays.

In basic power system set up, power apparatus, like the generators and power transformers may be subject to abnormal conditions like fault. They might experience over current and over voltages. They are usually accompanied with protective equipment like power circuit breakers. But these breakers merely react to what information they are fed with.

Protective relays acts as the “eye” and brain to the muscle of the circuit breakers. These relays therefore must be set and coordinated with, to ensure smooth, reliable, and correct power system protection.

Below are three of the more popular references in basic protective relaying. This is very useful for upstart relay engineers and students as well who are interested in protective relaying. As a career, relay engineer is a good one, as it is one of the highly technical ones.

other references that may interest you:

Just always remember, Protective Relaying is one of the major keys in  System Protection.

Sebastian Ziani de Ferranti - ELECTRICAL ENGINEERING HERO

Earlier on, we discussed a phenomenon called the Ferranti Effect. This is a rise in voltage occurring at the receiving end of a long transmission line, relative to the voltage at the sending end. This honor belongs to a British electrical engineer who promoted the installation of large electrical generating stations and alternating-current distribution networks in England.
This electrical effect was named after Sabastian Ziani de Ferranti (1864-1930), who in 1887 became the chief engineer for London Electric Supply Corporation (LESCo), responsible for the design of their power station at Deptford, England.

What led to this discovery was during the early days of Ferranti’s work at the Deptford Power Station, an anomaly was experienced when transmission line voltages remote from the generator rose to levels that damaged equipment. Intuition led engineers and operators of the time to think that voltage would decay over long distances, but this turned out to be true only when the line is loaded.

For more about our Electrical Engineering Hero, below are references:


Ferranti Effect is an electrical engineering phenomenon, wherein there is a rise in voltage occurring at the end of a long transmission line when its load is disconnected. We usually observed that the sending voltage is greater than the receiving end voltage. From the equation:
Vs = Vr + (current x impedance), the receiving voltage is lower since it is the difference of the Voltage Sending and the voltage drop.

The operative words here are, long transmission lines and disconnected load. Under no load conditions, theoretically, Vs=Vr.  Furthermore, one classification of transmission lines is according to its length or circuit km. In long transmission lines, you are going to take into consideration the effect of capacitance and the charging current of the lines.

Due to the voltage drop across the line inductance (due to charging current) being in phase with the sending end voltages, capacitance and inductance is responsible to produce this phenomenon.

For more about the Ferranti Effect, you may click on these free links/pdf
Radiation effects on power transistors (Ferranti semiconductors ; 1)


Hello. In this blog, we will try to create a steel pole model, using the PLS Pole software of Power Lines System. This created pole will practically be part of your data bank that can be later used to create structures. These structures on the other hand can be used in PLS CADD for analysis. In itself, the PLS pole could analyze the integrity and strength of both the structures and the pole. 

First things first is to build up your data base of components. For starters, I hope this helps. 

Click on the links for the .doc files.



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folk, please bear on the admin on the delay of the turorials.
soon the tutorials will start so visit the site from time to time.
in the mean time, please leave a comment on what you want to know regarding pls software so that it will be featured on this site


Starting today, October 2, 2010, changes will be made on this blog site. Aside from Transmission and distribution lines topics, the following topics will also be found:

Substation Design
General Engineering
All Electrical Engineering and Electronics topics.
Questions are also encouraged
you may email your queries here:


I would like to share this interesting video. It is about a proposed project linking the renewable energy sources plants in Canada up to New York through underwater cables. It pretty much discusses the overhead transmission lines and the opposition on it and how builders find ways to deliver power despite and due to the many problems encountered in building overhead transmission lines.

New Underwater Transmission Lines Proposed

original URL: http://www.dailymotion.com/video/xdl8s3_new-underwater-transmission-lines-p_news


The Ruling Span is defined as the assumed uniform span that most likely represents actual spans that are in any particular section of the line. In the absence of finite element analysis tools or software (ex. PLS CADD), the ruling span is used to calculate sag and clearances on the plan profile drawing, and it is necessary in structure spotting.

Ruling Span Tip: When stringing the line, the general rule is that the spans in the line should not be more than twice the ruling span, or less than half of the ruling span.

Ruling Span is one of the most used yet misunderstood and misused terms in the design, staking, and construction of overhead lines. “Ruling span” is loosely used with several different meanings.

Theoretical Ruling Span: It is the equation derived from the conductor length equation and by making certain assumptions, approximations, and formula substitutions. This formula must be used if the actual spans are already known.
The theoretical ruling span equation is not exact because of the assumptions made. Since
its accuracy is sufficient for most line designs, it is the equation used most often to calculate the ruling span for new overhead distribution lines.

Estimated Ruling Span: If the actual spans are not yet determined but knowledge gained from a reconnaissance and previous surveys of the proposed line are known, it is possible to estimate a ruling span. A traditional “rule of thumb” equation that may be helpful in the estimation of a ruling span is:
Se = Average Span + 2/3 (Maximum Span – Average Span)

Use this rule for estimating the ruling span with caution.  Use only this formula if the actual spans are not yet known.

What would happen if my ruling span is different from the actual design?

If the design sag is greater than the theoretical sag, then the actual sag of the installed conductors will be less than the predicted sag. This condition will lead to increased conductor tensions, which may exceed the permitted loads of support structures and guying assemblies.
If the design sag is less than the theoretical sag, then the actual sag of the installed conductors will be greater than the predicted sag. This condition may result in inadequate ground clearances.

I hope this helps.

additional reading and resources:



During the current wars (AC vs. DC) days, it was the economics of transmitting power in high voltage and low through power transformers sealed the fate in favor of AC power transmission. But nowadays, Direct Current is fighting back. Or that least, it is covering what AC power transmission cannot.

Most if not all of the bulk transmission of powers are in AC. That was up until 1954, the firstHVDC (10MW) transmission system was commissioned in Gotland. It is of important to note that as early as 1941; a proposed 60 MW HVDC link in Germany did not fully materialize due to war.

HVDC is favorable to AC transmission on the following reasons:

. No technical limit to the length of a submarine cable connection.
. No requirement that the linked systems run in synchronism.
. No increase to the short circuit capacity imposed on AC switchgear.
. Immunity from impedance, phase angle, frequency or voltage fluctuations.
. Preserves independent management of frequency and generator control.
. Improves both the AC system’s stability and, therefore, improves the internal power carrying capacity, by modulation of power in response to frequency, power swing or line

The advantages of using HVDC Transmission:

1.The cost of d.c. transmission line is less than 3 - phase a.c. line because only two
conductors are necessary for D.C. line.
2.Tower designs are simple.
3.The dielectric strength of cable is high .
4.The dielectric loss is low.
5.For D.C. overhead transmission lines length is unlimited.
6.Power transmission capacity is higher than a.c.
7.Corona & radio frequency interference losses are less.
8.HVDC link has accurate & quick control of power in the required direction

The Limitations of HVDC Transmission:

1. Transformer for step up – step down voltages are not available in case of HVDC.
2. The terminal equipment is costly.
3. Reliable d.c. ckt. Breakers for higher ratings are not available. (yet)
4. Earth current may cause some side effects.
5. Reactive MVA cannot be transferred over a HVDC link.
6. Although inverters are used, the wave farm of output a.c. is not exactly sinusoidal and
it contains harmonic distortion

One of the most important considerations in any project is the cost. The best of to explain the relationship or comparison between AC and HVDC is this;

HVDC has high const in the construction of its terminal points compared to ac. But as the transmission lines approaches infinite length, which hypothetically means the longer the transmission lines are, its cost would become lesser compared to ac.

Considerable amount or research and development are still being done to improve transmission of bulk power in dc as of the moment. Me for one hopes to be involved in an HVDC project someday.

For details on the topic HVDC Transmission of power, LINKS and RESOURCES of the topic can be seen below.


Transmission Line Restoration From July 17 Wind Storm Completed 
Sep 9, 2010 10:40 PM

Restoration of Nebraska Public Power District's 230-kV transmission line, severely damaged in a July 17 wind storm, was completed when the line was re-energized Monday, Aug. 30.

Crews completed restoration work on a section of the line between the District's Riverdale substation, located north of Kearney, to a substation east near Grand Island Monday afternoon. A total of 129 structures were damaged on the line, with approximately 18 mi of power lines coming to the ground.

Earlier, another section of line, running west from the Riverdale substation to Crooked Creek substation, north of Lexington, was restored August 22. That section of line saw 87 structures damaged with 14 mi of line down over two separate sections. A third transmission line, running from Riverdale to the Tower substation in Kearney, had an additional eight structures damaged with about one mile of line being downed. That work was completed several days after the storm.

NPPD's Transmission and Distribution Manager Tom Kent said that completing the work and restoring the system back to full operation took a combination of team work from District employees, contractors, and suppliers to return the line to service.

"We met our goal of having the line safely returned to service by the end of the month," Kent explained, "we used our best available resources, including stringing of line using a helicopter, to bring the line back into service. While meeting that goal we also had a safe restoration effort by employees and contractors.

"NPPD thanks the many property owners for their cooperation as their property was impacted by the power lines that were downed and throughout the restoration process." NPPD will continue to work with those property owners to restore property and repair damages caused by the downed lines or reconstruction work.

The July 17 storm pushed through the area bringing winds that measured between 70 and 100 miles per hour. While those high voltage lines were lost that night, NPPD's control center was able to redirect power so that no customers were without service.

NPPD estimated the cost of reconstructing the two lines at approximately $12 million, with a portion of the cost to be reimbursed by the Federal Emergency Management Agency. Final right-of-way clean up and demobilization for both lines will continue for about two more weeks.

news source: http://tdworld.com/projects_in_progress/announcements/nppd-wind-storm-restoration-0910/




in any consolitation.

Basic Components of Overhead Power Lines

The most common way method of transmitting power is through overhead power lines. It is relatively less costly, visible detection of faults, repair and maintenance is easier compared to underground system.

The following are the basic components of an overhead power line (click on links to see pic):

Supporting structures


Electricity as most of us know, are conveniently utilized as we plug our appliances and machines to our power sockets. However, the origin of that very electricity though may actually be as far as hundred and even thousand of kilometers away. These are from power plants and other power generating stations.

A generating plant will be useless unless its generated energy (power) in millions and even thousands of billions of watts will be delivered to its consumers, to us. These electrons traveled in speed approaching that of light, through a medium called transmission and distribution lines.
Electricity might be transmitted and distributed in either on the following ways(click on link for pics):

The choice and selection of methods of construction would usually vary on the philosophy of the personalities and circumstances involved. These would refer to the owner of the lines, the engineering team and the culture, practice and applicability wherein the transmission lines are located.

The most common type of transmission and distribution lines there is, are the overhead types. These are conductors, bare and insulated those are attached to supporting structures, usually poles and towers. It could be attributed to the fact that it would be cheaper in first cost, maintenance and repair as compared to that of underground.

The main selling point of an underground system is in its aesthetics. Certain customers or situation would require a use of underground cables in distributing power. Common cases would be the impracticality of putting overhead lines due to existing aerial obstruction. Submarine cables are common in inter-island grid interconnection.


Greetings everyone.

One of the most useful forms of energy ever utilized is in the form of electricity. It is a primary if not the sole contributor in the advent on human history and civilization. It is almost impossible to imagine living today without electric power. Without it, you won't be reading this blog, since nothing will power your computer.

One of the most visible and profound units of the electrical power system are its transmission and distribution lines. Lines, wires, cables, it is almost everywhere and yet it is as if it is nothing to most of us.

But the creation, design and construction of these lines, the engineering behind in itself is a wonder to behold. The evolution, from the site and draft process to the use of sophisticated software like PLS-CADD makes the study of craft even more exciting.

This blog aims to give everyone an overview, a brief understanding and resources in understanding and appreciation of the art and science of transmission and distribution lines design.

Everyone is encouraged to browse, ask and interact with us. Much effort will be done to make entries as convenient and as accommodating to all. Students could use some of the materials for their research. The curious may find some of it handy and useful. This blogs might also serve as an avenue in interaction of Engineers who are involved in this field.

Succeeding entries will give information and definition on some of transmission lines nuisance, tips on transmission lines design, ask an expert and PLS-CADD tutorials.

I hope you'll like this site and would find as much information as you could.