Cable Parameters: Insulation Resistance,Charging Current, Dielectric Losses

Cable Parameters: Insulation Resistance, Charging Current, Dielectric Losses

Before we formulated cable basic parameters resistance, inductance, and capacitance, now we will try to 3 more parameters like Insulation Resistance, Charging Current and Dielectric Losses.

Cable Insulation Resistance:

Using the following formula you can calculate insulation resistance in mega-ohm per kilometer of cable, to do this you consider the insulation material, diameter of cable including a semiconductor layer, and the diameter of the insulated core.

R =K In (D/d )  MΩ/km

Where

R = Insulation resistance in MΩ/km;

K = Constant depends on the insulation material;

d = Diameter of the conductor in mm including the semiconducting layer;

D = Diameter in mm of the insulated core;

MΩ- mega ohm, km- kilo meter, mm- mili meter.

Cable Charging Current:

The charging current is the capacitive current that flows when AC voltage is applied to the cables as a result of the capacitance between the conductor and earth, and for a multi-core cable in which cores are not screened, between conductors. The value can be calculated from the following equation.

IC = Uo ωC 10^-6   A/km

Where

IC = Charging current in Ampear/km;

Uo =Voltage in volt between phase and earth;

ω= 2 π f (π=22/7, f= frequency in hertz) Hz;

C= Capacitance in micro-farad per kilo-meter to neutral;

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Cable Dielectric Losses:

To calculate the dielectric losses of an AC cable are proportional to the Capacitance, the frequency, the phase voltage and the power factor. The value in watt per kilo-meter per phase can be calculated from the following equation.

WD = 2 π f C Uo² tanδ 10^-6   watt/km/phase

Where 

WD = Dielectric losses in watt/km/phase;

f = Frequency in hertz;

C = Capacitance in micro-farad per kilo-meter to neutral;

Uo = Voltage in volt between phase and earth;

tanδ=Dielectric power factor.

Switching and Earthing Operating Procedure

Switching and Earthing Operative Procedure in Electrical Energy Network

 

The keywords of this article are Switching & Earthing; we are not going to learn technical details about switching and earthing procedures in this piece, but we would like to keep in limit our focus on the key points to the safe operation of switching & earthing system.

The Switching

How keep your switching system safe and healthy in the electrical energy transmission and distribution network? Let’s review some important points that will keep you a smarter switching operator.

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Circuit Breakers and Isolator Operation

1.     Don’t allow switching or any operation in a system without clear permission of the controlling authority except in an emergency case for personnel or property;

2.     System control authority should directly communicate with an authorized person who will operate the switching;

3.     If direct contact is not possible for controlling authorities, the message may be relayed by a third party with written down without any alteration or abbreviation;

4.     If a switching or operating message send by any wireless devices then the receiver will write the message and readout to the sender to ensure that it has been received accurately;

5.     The circuit Breakers or Isolators operator should carry on the message from control authorities without delay  regarding switching or operation;

6.     If emergency switching is required to save the life or property, the report must be relayed to control authority as soon as possible;

7.     If any fault is visible to any equipment, operator must  inform to controlling authority immediately before operation or switching;

8.     Very details switching and operation record must maintain in a station Log.

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The Earthing

The earthing switch is very much related to switching or operating the circuit breakers and isolators. To ensure life and property isolator and earthing switch must be operated safely.

Circuit Main Earth or CME Operation

The Circuit Main Earth or CME must be operated under the supervision of authorized seniors and after clear instruction from the controlling authorities. The position of the earthing and location of each connection must be recorded in the station Log.

If you have many more ideas about switching and earthing operations, you can share them in the comments space. If you think others should know this for safe work, please don’t forget to hit the like or share button below.

Voltage Drop Calculation for Electrical Power Cable

What is Voltage Drop for Cable?

When current flows in a cable conductor a voltage drop is developed in between the ends of the conductor which is the product of flowing current and the impedance of the cable.

Why Calculation Voltage Drop?

It is a common obligation for the designer to calculate the voltage drop as requirements are the main factor in determining the minimum conductor sizes (cross-sectional area) that can be used for a particular electrical circuit.

How to Calculate Voltage Drop?

Calculating the voltage drop of a circuit the designer has two options to choose of them depending on the project requirements. These pretty two options are as below:

Simple Design Approach

Accurate Design Approach

The simple design approach is a rough estimated one which sometimes leads to the use of larger conductor cross-sectional areas than are necessary for the project. If you consider a simple approach, then basically the following information is needed:

·        

•     Type of cable;
•     Conductor cross-sectional area;
•     Method of installation (for AC circuits only);
•     Circuit route length;
•    Type of circuit (DC, single-phase AC or three-phase  AC);
•     Load on the circuit.

Information is not needed for a simple approach:

•   Type and nominal current rating of the associated overcurrent device;
•   Ambient temperature;
•   Whether the circuit is run singly or grouped with other  circuits;
•    The power factor of the load.

On the other hand, an accurate design approach takes more into consideration conductor operating temperature. Above mentioned four “not needed information” for a simple approach should consider for a more accurate approach, especially two factors namely:

•    The ambient temperature
•    Whether the circuit is to be run singly or grouped with other circuits.

Calculate Voltage Drop Smartly:

We who work with cable system sometimes have to calculate voltage drop in short and very smartly. Considering this point of view following two formulas may be helpful for voltage drop calculation smartly.

Voltage Drop Calculation Formula for Single Phase Circuit:

V_d=2Il (R cos ø + X sin ø)  V

Voltage Drop Calculation Formula for Three Phase Circuit:

V_d=√ 3 I l (R cos ø + X sin ø)  V

Where

V_d = Voltage drop in Volt;

I = Load current in Amper;

R =A C Resistance in Ω/km;

X =Reactance in Ω/km;

cos ø = Power factor;

l  = Length in km;

X = ^ωL10-3

 ^ω=2 π f

L = from table mh/km

The limit of voltage drop depends on national code and standards which vary from country to country, and hope we got some basic idea on Voltage Drop for Electrical Power Cable.

Electricity Myth and Fact in Our Socity

Electricity Myths Can be a Killer

There are lots of juicy myths on various subjects like earthquake, eclipse, etc. in almost every nation; but the fact is that electricity myths are not jukes or fun, just a little mistake can cause of severe electrical shock, burn or even death!!

If you don’t sure or without advice from electrician, do not believe any myth on electricity. To know the fact contact your nearest electricity utility company or any electrical professional or electrician.

Our post on electricity myth and fact may not be juicy or folky but will give you some important information that will help to use safe electricity as well as save your electricity.

Myths and Facts on Electrical Safety

Myth: Power lines are insulated, no chance to shock.                               

Fact: Most of the powerlines are not insulated and insulated powerlines also can be lost their insulation any time very easily.

Myth: This line is safe because it is not a high voltage line.

Fact: Actually high voltage is not required to kill anyone, ampere flowing through the body is enough to kill. Our house using about 100 ampere where the 1-ampere shock is enough to fatal heart irregularities.

Myth: Birds landing on electric wires, so wires are safe to touch.

Fact: No, Birds touching an only live wire and not touching any ground path to complete the circuit, that’s why birds are not electrifying.

Myth: The fallen conductor is shut off, no electricity presence.

Fact: Not true always, if it is fallen on poor conductive materials like dry earth or grasses, bitumen etc.

Myth: Live conductor make sparks; so no spark fallen wire is safe.

Fact: Actually sparks happen where there is loos contact, with firm contact sparks not happen.

Myth: As the ladder is not metallic, so it can rest on live electric line.

Fact: No, If you don’t know the material property and hazard risk level, don’t use ladder rest on powerline.

Myth: Bamboo and wood are not conductors.

Fact: Actually dry bamboo and wood are poor conductors, but witty or green bamboo and wood are conductive that may cause severe shock.

Myth: Rubber is an insulator, so rubber gloves and shoes are safe to touch electricity.

Fact: Only 100% pure rubber or especially electrical insulation type rubber is a good insulator, otherwise typically mixed materials used rubber gloves or shoes are not a good insulator.

Myth: Trimming the tree and touching on electric line for a short moment of time is not dangerous.

Fact: No, never do this. Call the nearest power utility department.

Myth: Digging a sallow/ few deep in the ground, no chance to reach an underground cable.

Fact: Underground cable may be in an upper layer than you are thinking, take advice from professional.

Myth: Electric shock become only for touching the live wire, close to it is no danger.

Fact: Closed to high voltage live line is as a danger as touching. Current can jump or arc. Keep a safe distance from the electric line always, at least 3 meters. 

This is not a myth

Myths and Facts on Electric Bill

Myth: It takes more energy to turn on the switch for the light bulb or fan, so better to keep it on to save the electricity bill.

Fact: No! there is no extra electricity used to switch ON/OFF. Turning the light/fan off saves the electricity consumes. Appliances consume a small amount of energy while on standby mode, better to unplug/switch off.

Myth: Keeping the AC running the whole day in the high setting is better than running at end of the day while the room is heated, this way saves energy.

Fact: Not a wise decision, cooling the hot room down takes less energy than running the AC the whole day in any setting.

Myth: The same device takes more energy in the 240V system than the 110V system.

Fact: No, the energy measured by a unit in watts comes from the multiplication of voltage and current. In an electrical system power/watt is always the same, if the voltage increases the current decreases proportionally and vice-versa. So, wattages remain the same and so does the cost.

Myth: Faulty wiring is the cause of paying more electric bills than that used.

Fact: Yes, if the wiring system with small leakage that will not lead your line to shut off, but some leakage current always passes out from the circuit even all the switches, that you have not used but counted on the energy meter for billing at end of the month.

Myth: Mis-wiring or using undersized wire causes more electric bills.

Fact: Yes, using undersized cable in house wiring is cause to pay more electric bill than that used. If the cable/wire size is not enough to carry the current safely, the wire becomes heated, and extra electrical energy uses as dissipated heat energy is the cause of the extra electric bill. 

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What is Electricity Kite?

Franklin wrote an article for the Pennsylvania Gazette in 1752, an article that tried to prove theoretically the existence of electricity. Franklin chooses a cloudy and stormy day to do his experiment, flying a kite to reach near lightning. Franklin's kite was silken, complete with the lightning road, a key sagging on the end of the string. When lighting struck the Franklin kite volt traveled through the string and charged the metal key. Franklin touching the key got shocked and proved the existence of electricity.

Last Line: Enjoy the myths but remember the fact before coming near to electricity.

Why The Sun Become Reddish During Sunset?

Sunset at sea-shore, you will find the sun as like a reddish dining plate, the moment is very lovely, we must like it. During this time the sun looks very red, but the sun color is never red.

During the day time you cannot find the sun in this color, only a particular moment of the day you will find it like this reddish color. 

The fact is that when you find the sun is red during sunset, at the same time others people from thousand kilo meters away from you cannot see it red. So, the sun never be red.

The sun become reddish during sunset because the distance from us that the sunlight passes through the space. You can remember that the sunlight actually contains all the colors. Our eyes detect the sunlight as white that actually a mixture of all colors.

But in the space around us where presence the air, dust, humidity or water particles, and many more micro particles that light refraction property is different.

During sunset at the horizon, due to the light refraction property in different particles, we see the red and yellow color more than the others color that makes the sun reddish to us.

For the same reason, we see the sky blue during the clear weather. 

Why Does The Sun Give Us Light?

 It is difficult to believe that what we see at night in the sky and the bright sun at day time is the same things. It is true that the sun is also a star that is the closet star of the earth. 

What we mean by life that totally depends on the sun. If the light and heat do not come to the earth from the sun, it was impossible to create and exist life on the earth. Without sunlight the green trees and human cannot exist. 

The sun is 93,000,000 miles away from the earth and 1,300,000 times bigger than the earth.

It is very interesting that the sun not solid as like as the earth. The temperature of the sun surface is 6,000^oC. This super high temperature is enough to be any material into gas. So, no doubt the sun is in gaseous state. 

Earlier, the scientists were believe that the sun is burning continuously to generate the light and heat. Recently the scientists are changed their mind and believe that the sun generate light and heat as like the atomic bomb working principle. 

Actually the light and the heat generate on the sun converting the particle of matter into energy that is completely different from burning.

In burning procedure matter changes the state from one form to other, but in converting particle to energy its required very small amount of matter to produce huge amount of energy.

Example:

Only 28g particle can produce such amount of energy that can melt more than 1,000,000 tons stone.

So, if the science is true, the sun is converting materials in energy continuously to produce light and heat.

When the sun will become useless or become zero mass? The sun can generate heat and light energy for 150 thousand million (150,000,000,000) years just using 1% of its mass.