What is a Bus Bar : Types & Their Working

During the distribution of electrical power to various output circuits, two or more wires are connected to a single wire. The improper electrical connection gets opened and the insulation of the wire may get damaged due to heat generation in the wires. This condition may lead to an open circuit, which is too dangerous for the distribution of power. In such cases, to avoid open-circuit conditions, the multiple wires are connected properly using an electric bus system. The bus bar is an electrical component used in electrical distribution systems to collect current from the input terminals of an electrical system and distributes it to various output circuits. It is used as a junction between the input power and output power. It distributes the power to various output circuits with more flexibility. This article is an overview of the bus bar and its types.

What is the Bus Bar?

The conducting material or a conductor used to collect power from the input terminals of an electrical system and distribute it to various output circuits is known as an electrical bus bar or bus system. It acts as a junction, where the incoming power and outgoing power meets. It is used to collect all the electrical power in one place. It is available in the form of rectangular strips, round tubes, round bars, and square bars made up of aluminum, copper, and brass.


The use of an electrical type will reduce the cost of labor, maintenance cost, and installation costs. These are connected very easily and quickly. These are used in various applications like hospitals, industries, data centers, railways, metros, institutions, computer technology, and many more.

It contains an isolator and the circuit breaker. If any fault occurs, the circuit breaker gets tripped off and the part of the bus bar, which is faulty can easily be disconnected. Mostly rectangular type is used in electrical power distribution systems.

Types of Bus Bar

The bus bars are available in the sizes of 40x4mm, 40x5mm, 60x8mm, 50x6mm, 80x8mm, and 100x10mm. These are used in the distribution of power depend on factors like cost, flexibility, reliability, etc. While selecting its arrangement, consider that the arrangement should be easy and simple, cheap and the maintenance should not affect the process of distribution of power.

The single type is used in small substations where the process of the continuous power supply is not required. An additional type is used in large substations to avoid interruption in the power distribution. The different types are explained below.

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Single Bus-Bar Arrangement

The single bus bar arrangement is very simple and easy. This type of arrangement consists of a single bus with a switchboard. The transformers, feeders, and generators are connected to the bus bar as shown in the figure below.

Single Bus Bar
Single Bus Bar

The circuit breakers control the transformers, generators, and feeders. During the maintenance, the isolators are used to isolate the transformers, generators, and feeders from the bus bar.

The advantages of the single bus bar arrangement are

  • Low cost
  • Less maintenance
  • Operation is simple and easy.

The disadvantages of a single bus bar arrangement are

  • If any fault occurs in this, the whole distribution of power is interrupted and the feeders will be disconnected.
  • It is less flexible and used in only small substations, switchboards, and small power stations where the continuous distribution of power is not needed.

Single Bus-Bar Arrangement with Bus Sectionalized

This type of arrangement is used in large stations where several units are installed using a bus sectionalized. In this type, the circuit breakers and isolators are used as shown in the figure below.

Single Bus Bar with Bus Sectionalized
Single Bus Bar with Bus Sectionalized

The isolator in the arrangement used to separate the faulty section to protect the system from the shutdown. There is no increase in cost even though an additional circuit breaker is used.

Advantages

  • Easy to remove the fault section, without any loss in the supply continuity
  • Individual sections on the bus can be repaired without disturbing the overall section on the bus bar.
  • The current limiting reactor helps to reduce the faults in the sections of the bus.

Disadvantages

Usage of additional isolators and circuit breakers in the system increases the cost.

Main and Transfer Bus Arrangement

This type of bus bar is designed by combining the auxiliary type and the main bus bar by using a bus coupler to connect the circuit breaker and isolated switches. In case of overloading, the load is transferred from one to another bus bar by using a bus coupler. In this case, the potentials of the two bus bars should be the same to transfer the load and the main bar should be opened and should be kept closer to transfer the load.

Main and Transfer Type
Main and Transfer Type

Advantages

  • The main advantage is shifting the load from one type to another type if any fault occurs loss of continuity.
  • The cost of repair and maintenance is less
  • Relays can be operated by using the bus potential.
  • It is very easy to shift the load on any other buses.

Disadvantages

  • As the whole systems use two bus bars, the cost would increase
  • The whole system may breakdown if any fault occurs in any of the sections on the bus.

Double Bus Double Breaker Arrangement

In this type, two bus bars with two circuit breakers are used. So, that it doesn’t require any special types of equipment like a switch and bus coupler.

Double Bus Bar Double Breaker
Double Bus Bar Double Breaker

Advantages

It gives the highest flexibility and reliability because there no loss of continuity due to the faults
Even though the load is transferred from one bus to another, there would be no change in the supply continuity of the system.

Disadvantages

The cost of the system and maintenance is more due to the additional circuit breakers and two buses. So, these types of bus bar systems are used in substations

Sectionalized Double Bus Bar Arrangement

In this type, an auxiliary type is also used along with the sectionalized main bus bar system. Any of the sections in the main type can be removed for repair and maintenance and can be connected to any of the auxiliary bus bars in the system. There is no need to sectionalize the auxiliary type because of its highest cost.

Sectionalized Type Arrangement
Sectionalized Type Arrangement

One and a Half Breaker Arrangement

This type of system uses 3 circuit breakers for 2 circuits. That means each circuit in this will use ½ circuit breaker. This type of arrangement is mainly employed in large stations like power handling circuits.

One and Half Breaker
One and Half Breaker

Advantages

  • Protects the system against loss of power supply
  • Can be used to operate relays
  • Easy to add additional circuits to the system

Disadvantages

  • Compex circuit due to the relay system
  • High maintenance cost

Ring Main Arrangement

This type of system is arranged in ring form by connecting the endpoint of the main bus bar in the system back to the starting point.

Ring Arrangement
Ring Arrangement

Advantages

  • Due to the ring arrangement, two paths are available for the supply. So, the working of the system will not be affected due to the faults.
  • Faults of a particular section in the whole system can be repaired without affecting the entire working of the systems.
  • Easy to maintain the circuit breaker without any interruption in the supply.

Disadvantages

  • The system would be overloaded if any of the circuit breakers are opened.
  • Adding the new circuit may create some complications.

Mesh Arrangement

This type of bus bar is controlled by 4 circuit breakers, which are installed in the mesh. From the node point, the circuit is tapped. The mesh formed by the buses gets opened due to the occurrence of faults in any of the sections. It is mainly used in the substations where it requires a large no. of circuits. It also provides security against faults. There is a lack of facility in switching.

Mesh Arrangement
Mesh Arrangement

Thus, this is all about the electrical bus bar and its types. Here is a question for you, “What is the purpose of an electrical bus bar in power distribution systems.

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