Check our new membership plans and prices! We usually depict the electrical distribution system by a graphic representation called a single line diagram SLD.
A single line can show all or part of a system. It is very versatile and comprehensive because it can depict very simple DC circuits , or a very complicated three-phase system. We use universally accepted electrical symbols to represent the different electrical components and their relationship within a circuit or system.
This chart shows the most frequently used symbols. Below is a simple electrical circuit.
You can tell by the symbols that this single line diagram has three resistors and a battery. The electricity flows from the negative side of the battery through the resistors to the positive side of the battery. This helps to keep the voltages and their paths straight. Starting at the top, you will notice that a transformer is feeding power to the whole system.
The transformer steps the voltage down from 35kV to 15kV, as indicated by the numbers next to the transformer symbol. You can assume this circuit breaker can handle 15kV , since it is attached to the 15kV side of the transformer, and nothing different is indicated on the single line diagram. Following the drawout circuit breaker a1 from the transformer, it is attached to a heavier, horizontal line.
This horizontal line represents an electrical bus , which is a means used to get electricity to other areas or circuits. You will notice that two more drawout circuit breakers b1 and b2 are attached to the bus and feed other circuits, which are at 15kV, since there has been no indication of voltage change in the system. Attached to the drawout circuit breaker b1 , a step-down transformer is used to take the voltage in that area of the system from 15kV down to 5kV.
On the 5kV side of this transformer, a disconnect switch is shown. The disconnect is used to connect or isolate the equipment below it from the transformer. The equipment below the disconnect is at 5kV , since nothing indicates the contrary.
Do you recognize the equipment attached to the lower side of the disconnect switch as being two medium-voltage motor starters? A number of starters could be connected depending upon the particular system requirements. Now locate the second drawout circuit breaker b2. This circuit breaker is attached to a fused disconnect switch and it is connected to a step-down transformer.
Notice that all the equipment below the transformer is now considered low voltage equipment, because the voltage has been stepped down to a level of volts or lower. Moving to the bottom area of the single line diagram, notice that the circuit breaker b3 in the middle is connected to the bus in the bottom portion. To the bottom left and connected to the bus is another fixed circuit breaker. Look carefully at the next grouping of symbols.
Do you recognize the automatic transfer switch symbol? Also, notice that a circle symbol which represents an emergency generator is attached to the automatic transfer switch. A low-voltage motor control circuit is attached to the automatic transfer switch through a low-voltage bus. Make sure you recognize these symbols.
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Although we do not know the exact function of the low voltage motor control in this circuit, it is obvious that it is important to keep the equipment up and running. A written specification would normally provide the details of the application. Below the meter center is a load center or panelboard that is feeding a number of smaller circuits.
This could represent a load center in a building that feeds power to the lights, air conditioning, heat and any other electrical equipment connected to the building.
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Please can you send me the pdf copy to my email corustartechnology gmail. Recently the EU drawings are not with number Nice Explanation. Ed can you give your email since I had few clarifications to be made, may be you might have published in your earlier versions.
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Harga ATK (Alat Tulis Kantor)
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Please send me this Valuable information on my email Address. Kindly send me the pdf through my email aikinsmyglory gmail. Possible send me PDF … rahismohammed87 mail. It is obviously not the CB number as they are all the same! Please send me a PDF file form as this article is very useful as reference.
Very useful information can you send me pdf on my Gmail. Can you please send me PDF soft copy danishkhan85 gmail. Very useful information. Credits to EEP and the author i really appreciate. Excellent info. For a customized excel template that performs fault calculations, please feel free to email me at cnnb17 yahoo. Thanks clarity..
I love the way you simply the single line diagram.. Pls send me file on Siemens substation and transmissions line protection. Very good. Thank you Edvard Csyani sir for your valuable lessons. EEP has been very helpful,especially for freshers like me who lacks practical experience. I look forward to more important articles. I was looking for that stuff, Well explained. This engineering portal is very helpful for beginner like me.
Do you have anything that can help out to understand them? A comparison table would be great. Thanks very much for those information, its very helpful and informative. However, could you be able to send me a simple systematic drawing from point of generation to transmission and distribution please.
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Sir, there is this component in a SLD i m given to read which contains a circle with MF written in it, what would that be? Please send me this file if possible. Kindly send me this complete article.
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More Information. Single line diagram SLD We usually depict the electrical distribution system by a graphic representation called a single line diagram SLD. The last piece of electrical equipment in the middle portion of the diagram is another circuit breaker b3. This time, however, the circuit breaker is a fixed low voltage circuit breaker , as indicated by the symbol. On the right side of the third area there is another fixed circuit breaker connected to the bus.
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It is attached to a meter center , as indicated by the symbol formed by three circles. This indicates that the electric company is using these meters to keep track of power consumed by the equipment below the meter center.
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