What is a bus bar?

bus bar schemes

A bus bar is an essential component of electrical systems. bus bar made from conductive materials like copper, aluminium, or brass.it is designed to carry substantial electric currents across various parts of an electrical assembly, such as a switchboard, distribution board, or substation.

Importance of Bus Bar Scheme

Bus bars are crucial for several reasons. Firstly, they ensure the effective distribution of power, allowing electricity to be supplied from a single source to multiple circuits or endpoints.

This centralized distribution helps maintain a consistent voltage level across all connected components, which is vital for the stable operation of electrical systems.

Secondly, bus bars are designed to dissipate heat efficiently. The heat generated during the transmission of electricity can be detrimental to the system's components, but bus bars help mitigate this by spreading out the heat and reducing the risk of overheating.

Moreover, bus bars contribute to space optimization within electrical panels and cabinets. Their compact and centralized nature allows for a more organized and less cluttered setup, which is particularly beneficial in environments where space is at a premium.

Types of Busbar Connection

Many types of bus bar schemes are used in power substations including

Single Bus Bar Scheme
Single Bus Bar With Sectionalizer Scheme
Double Bus Bar Scheme
Ring Bus Bar Scheme

Single Bus Bar Scheme

A single bus bar is a main conductor or a set of conductors that carries the entire electrical load of the substation.

Components of Single Bus Bar Scheme

Bus Bar
Circuit Breakers
Isolators
Earthing Switch

In normal operation, all incoming and outgoing circuits are connected to the single bus bar, allowing the flow of electrical power through the system. During the maintenance mode of a particular circuit, isolators are used to disconnect the faulty circuit from the bus bar.

The earthing switch is often employed to ground the isolated portion for safety.

single bus bar

Advantages of Single Bus bar

we need a single circuit breaker in the feeder of the single bus bar Scheme
The single bus bar is a low-cost system
The relay system is simple in a single bus bar system.
In a single bus bar system, we do not need transfer break switches to break the connection.
The maintenance cost is low due to the minimum circuit breaker
Single bus bar allows the system that we used bus bar potentials to as relay.
The protective relay system is simple
The operating system is simple and its cost is low
single bus bar scheme is used in 11kv.
this scheme needs minimum space.
fault tracking is easy in a single bus bar system.

Disadvantages of single bus bar

For maintenance work in the single bus bar system, we need the whole system shutdown.
If we need to extend the system we also need to shut down the supply
The overall efficiency of the system is not good in a single bus bar.
The single bus bar scheme is non-reliable.
A single bus bar scheme is not used for more than 33kv.

Single Bus Bar With Sectionalizer Scheme

if we divide the single bus bar system into two parts, this type of arrangement is called a single bus bar with a sectionalized scheme. In this system, we use one brake and two isolators in part. we also divide the single bus bar system into multiple systems. how many divisions of bus bar sections is depends on the importance of substations and switching requirements.

bus bar with sectionalize

we know that, In a single bus bar system for maintenance work, we need to shut down the whole system which results in the consumers being affected in this process. To overcome this problem we divide the single bus system into two or multiple parts as per requirements.

In This scheme when any fault occurs or we need to do maintenance work we just shut down a particular bus bar system. when we need to shut down a particular supply we use the circuit breaker to open the isolators because we always operate isolators with no load.

when we restore the supply we first close the isolators and then 'on' the circuit breaker. In this scheme, we also use current limiting reactors to minimize the fault MVA to reduce the circuit breaker capacity.

Advantages of Sectionlize Single Scheme

A sectionalized single bus bar scheme is a type of power distribution system that provides several advantages over other schemes. Here are some of the advantages of a sectionalized single-bus bar scheme

Improved Reliability
Reduced Maintenance
Flexibility
Cost-effective
Enhanced safety

Improved Reliability

The sectionalized single bus bar scheme increases the reliability of the power distribution system by reducing the impact of faults or failures in a particular section. In the event of a fault or failure, only the affected section needs to be shut down, while the rest of the system continues to operate normally.

Reduced Maintenance

The sectionalized single bus bar scheme reduces maintenance requirements by allowing sections of the system to be taken offline for maintenance without affecting the rest of the system.

Flexibility

The sectionalized single bus bar scheme provides greater flexibility in the operation of the power distribution system. It allows for the addition or removal of sections as needed, without requiring a complete overhaul of the system.

Cost-effective

The sectionalized single bus bar scheme is cost-effective compared to other schemes, as it requires less equipment and maintenance costs.

Enhanced safety

The sectionalized single bus bar scheme improves safety by reducing the likelihood of accidents, such as electrical shocks and short circuits.

Disadvantages of Sectionlize Single Scheme

The initial cost of this Sectionlize bus bar Scheme is high.
Sectionlize bus bar scheme required more maintenance.
The number of breakers and isolators required
Sectionlize busbar system is complex as compared to a single busbar system
if a fault occurs in a particular section we must shut down the particular section for maintenance work.

Double Bus Bar Scheme

Two main conductors or sets of conductors are used each functioning as a main bus bar. The switching arrangement allows the system to be operated with either bus bar active.

During normal operation, one of the bus bars (Bus A or Bus B) carries the entire electrical load. The other bus bar remains idle, providing backup.

Double bus bar scheme

When maintenance or repair is required on one of the bus bars, the load can be transferred to the idle bus bar by using circuit breakers and isolators. This allows maintenance on the active bus bar without interrupting the power supply.

Double bus bar schemes are commonly used in critical power systems where reliability and availability are paramount, such as in substations serving hospitals, data centres, or industrial facilities. The Double Bus Bar Scheme is a reliable and flexible configuration for power substations, used without interrupting the power supply.

The cost of a double bus is high as compared to the single bus bar.

Advantages of Double Bus bar

In this scheme, we shift the complete load on each bus bar.
it has high stability as compared to other systems.
their maintenance is easy.
it is used in extra high voltages.
The double bus bar scheme provides continuity of supply.
it is a protected and stable scheme.
The end consumer is not affected during maintenance.
Their efficiency is high as compared to a single bus bar system.

Disadvantages of Double Bus bar

The initial cost of a double bus bar is high as compared to a single bus bar.
This scheme is complex as compared to the single bus bar scheme
The double bus bar needs more space as compared to the single bus bar.
In Double bus bar chances of a short circuit are available.

Ring Bus Bar Scheme

The ring bus bar scheme, also known as the meshing scheme, represents a specific configuration used in electrical power substations and switchyards. In this arrangement, circuit breakers and bus bars are connected in series, forming a ring-like structure.

This scheme is recognized for its stability. its operation ensures continuous power supply in normal conditions while allowing for fault isolation during abnormal situations.

ring bus scheme

Advantages of Ring Bus Bar Scheme

maintenance and supervision are easy
the operating system is easy
the maintenance cost is minimal.
Ring bus bar scheme is used in most populated areas.
A ring bus bar is a stable and reliable system.

Disadvantages of the Ring Bus Bar Scheme

this scheme is limited to up to 6 circuits
the relay system is complex.

How to calculate the size of the bus bar?

Calculating the size of a bus bar involves several factors, including the material it's made of (usually copper or aluminium), the amount of current it needs to carry, and the permissible temperature rise.

The basic formula for the current carrying capacity (I) of a bus bar is

I = k *A

where 'k' is the current density (A/mm²) for the material, and 'A' is the cross-sectional area of the bus bar (mm²). For copper, a common value for 'k' is 1.2 A/mm², and for aluminium, it's 0.8 A/mm².

The cross-sectional area 'A' is calculated by multiplying the width of the bus bar by its thickness. It's important to consider the safety factor, which accounts for potential future load increases and is typically around 25%.

To ensure accuracy in your calculations, you might also need to consider factors such as the length of the bus bar, the electrical properties of the material, and the environment in which the bus bar will operate, as these can all influence the bus bar's performance and required size.

For example, if you're calculating for a copper bus bar that needs to carry 200 A and you're using a safety factor of 25%, you would calculate the required cross-sectional area as follows

A = I/k =

A = (200 A)/(1.2 A/mm²)

A = 167 mm²

Then, applying the safety factor

A(safe) = 167 (1 + 0.25 )

A(safe) = approx 209 mm²

This means you would need a copper bus bar with a cross-sectional area of at least 209 mm² to safely carry 200 A with a 25% safety factor. You would then choose the width and thickness of the bus bar that gives you at least this cross-sectional area.

Conclusions

In conclusion, bus bars are indispensable in the realm of electrical engineering. Their ability to distribute power effectively, regulate voltage, dissipate heat, optimize space, and enhance safety makes them a cornerstone of modern electrical systems.

Frequently Asked Questions – FAQs

What is a bus bar system?

A bus bar system is a conductive pathway that efficiently distributes electrical power within a switchgear, distribution board, substation, or other electrical apparatus.

Why are different schemes used in bus bar systems?

Different schemes provide varying levels of reliability, flexibility, and protection for the power system.

What are the common types of bus bar schemes?

The most common types include single bus, double bus double breaker, main and transfer bus, and breaker and a half schemes. Each has its own advantages and applications.

How is the bus bar system protected?

Protection schemes involve the use of differential relays, overcurrent protection, and circuit breakers to detect and isolate faults, ensuring system stability and safety.