#Example of single line diagram series#

This time, however, the circuit breaker is a fixed low voltage circuit breaker, as indicated by the symbol. The last piece of electrical equipment in the middle portion of the diagram is another circuit breaker (b3). 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 600 volts or lower. This circuit breaker is attached to a fused disconnect switch and it is connected to a step-down transformer. Now locate the second removable circuit breaker (b2). 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. The equipment below the disconnect is at 5kV, since nothing indicates the contrary. The disconnect is used to connect or isolate the equipment below it from the transformer. On the 5kV side of this transformer, a disconnect switch is shown. Attached to the removable circuit breaker (b1), a step-down transformer is used to take the voltage in that area of the system from 15kV down to 5kV. You will notice that two more removable 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. This horizontal line represents an electrical bus, which is a means used to get electricity to other areas or circuits. Do you recognize the removable circuit breaker 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 one-line.įollowing the drawout circuit breaker (a1) from the transformer, it is attached to a heavier, horizontal line. Once the voltage has been stepped down, a removable circuit breaker (a1) is encountered. The transformer steps the voltage down from 35kV to 15kV, as indicated by the numbers next to the transformer symbol. Starting at the top, you will notice that a transformer is feeding power to the whole system. To explain this easier, we have divided the single line into three sections. This helps to keep the voltages and their paths straight. When interpreting a single line diagram, you should always start at the top where the highest voltage is and work your way down to the lowest voltage. Lets go through a industrial single line diagram. Non-circuit breaker type transfer switch.One circuit breaker representing a main device and other circuit breakers representing feeder circuits usually in a common enclosure.

#Example of single line diagram series#

The symbol is a combination of a normally open contact (switch), overload relay, motor and disconnect device.Ī series of circle symbols representing meters usually mounted in a common enclosure. The symbol is a combination of a fuse and disconnect switch with the switch in the open position. The symbol is frequently shown in conjuction with a transfer switch. Protects a motor should an overload condition develop. Additional motor information is commonly printed next to symbol, such as horsepower, RPMand voltage.Ĭan represent a single contact or single pole switch in the open position for motor controlĬan represent a single contact or single pole switch in the closedposition for motor control Represents a motor and is also shown with an “M” inside the circle. Represents a battery in an equipment package Represents potential transformers usuallymounted in assembled equipment. Represents current transformers mounted in assembled equipment. Represents a switch in low or medium/high voltage applications (open position shown) Represents a fixed mounted low voltage circuit breaker. Additional information is normally printed next to symbol indicating winding connections, primary /secondary voltages and KVA or MVA ratings. Represents a variety of transformers from liquid filled to dry types. This chart shows the most frequently used symbols. To interpret one-lines you first need to be familiar with the electrical symbols. We use universally accepted electrical symbols to represent the different electrical components and their relationship within a circuit or system. It is very versatile and comprehensive because it can depict a very complicated three-phase system. A single line can show all or part of a system. We usually depict the electrical distribution system by a graphic representation called a single line diagram (SLD).