Types of interconnection power system and advantage and disadvantage

Here present the knowledge about the types of interconnection power system and advantage and disadvantage

There are mainly three types of interconnection.

AC interconnection
DC interconnection
Hybrid AC/DC interconnection

(1) AC interconnection

This figure show the AC interconnection scheme, two systems are directly connected to each other with converting station.

(2) DC interconnection

This figure shows the DC interconnection system. Both the system A and B having no converting station to change the voltage level and control the voltage. Transmission of large power blocks over long distances is however utilize by HVDC at the same time can strengthen the interconnection to avoid dynamic problem.

(3)Hybrid AC/DC interconnection

The hybrid interconnection system. Both AC and DC power is transmitted over long distance. The hybrid interconnection could therefore offer the best possibility for system interconnections in the case of continental networks, consisting of a number of small system.

➡Advantages of interconnected power system:-

(1) exchange of peak loads:

An important advantage of interconnected power system is that the peak load of the power station can be exchanged.
If the load curve of a power station shows a peak demand that is greater than the rated capacity of the plant,then the excess load can be shared by other stations interconnected with it.

(2) Use of Older Plants:

The interconnected system makes it possible to use the older and less efficient plants to carry peak loads of short durations.
Although such plants may be inadequate when used alone,yet they have sufficient capacity to carry short peaks of loads when interconnected with other modern plants.
Therefore,interconnected system gives a direct key to the use of obsolete plants.

(3)Ensures Economical Operation:

The interconnected system makes the operation of concerned power stations quite economical.
It is because sharing of load among the stations is arranged in such a way that more efficient stations work continuously throughout the year at a high load factor and the less efficient plants work for peak load hours only.

(4)Increases Diversity Factor:

The load curves of different interconnected stations are generally different.
The result is that the maximum demand on the system is much reduced as compared to the sum of individual maximum demands on different stations.
In other words,the diversity factor of the system is improved,thereby increasing the effective capacity of the system.

(5)Reduces Plant Reserve Capacity:

Every power station is required to have a standby unit for emergencies.
However,when several power stations are connected in parallel,the reserve capacity of the system is much reduced.
This increases the efficiency of the system.

(6)Increases Reliability of Supply:

The interconnected system increases the reliability of supply.
If a major breakdown occurs in one station,continuity of supply can be maintained by other healthy stations.

➡Disadvantage of interconnected power system

(1)Synchronizing Problem:

The generators of all the interconnected generating stations must operate the same at frequency and in a synchronized manner.
During the heavy load condition some generators go out of step due to this synchronization breakup.
And finally complete system goes out of step is also called black out condition.

(2)Expensive Tie Lines:

In the interconnected power system to control the system reactive power,tie lines are used.
Expense of tie lines for construction of interconnecting transmission line between generating stations.

(3)Expensive Circuit Breaker:

An interconnected system use circuit breaker to isolate the faulty part from the healthy part during the fault condition.
For high voltage power system,higher rating circuit breaker is used.
During the large flow of current on transmission line under faulty condition with a consequent increase in capacity of circuit breakers therefore expensive circuit breaker are required with interconnected power system.
Hence cost of circuit breakers increase.

4.Metering and Instrumentation:

Adequate metering and instrumentation is needed at different levels.
It is necessary to install sequential recorders,disturbance recorder,time of day meters etc.