Thomas M Sebastians "THOUGHTS"

How blackout works

Blackouts are terms associated with the Electrical grid.You must have heard about the blackout in Mumbai,NewYork etc.On those days you were able to see how the whole city came to halt. The transport system wasaffected, the telecommunication, the daily life,buisness everything came to a standstill. This was due tothe failure in recognising where the problem was and to recover it as soon as possible. Since the grid isa large structure it is very difficult to trace out where the problem really occured , unless there isconstant communication between the consumers, key nodes etc. The error occured ion NewYork took days torecover. While the Mumbai recovered it in one day.

Let us first understand what an electrical grid is. It can be simply told as theinterconnection of electrical lines operating in the same frequency. There will be sources and the usersaltogether present in the grid.The sources may thermal power stations, Hydropower stations, Nuclear power,wind power etc. But the end product is same , Electricity. The main usage of grid is to make an electricalsystem stable. If you consider a system without grid there will be always power failures,load cuttingetc.In almost every grid there will be additional power than the total power in demand. These will be a 5 percentage of total demand.This is to avoid the possible breakdown , due to the failure of a major generating station.

Lets start with a simple example.Consider the scenario where there are 3 generating stations of 5 Mw each. And they are connected to the grid or they are interconnected. They are connected to the load of 12Mw . They will give the load maximum efficiency when they are all running in rated rpm and at rated frequency. when 0ne of the machines fail the generated Mw will be 10Mw. Still the load can survive but the voltage and all will be low. And load can't effectively run on such voltage. This will affect life of the load. Now consider the one of the two running generators also goes down. This will seriously affect the generator. There is only generator with 5Mw with is feeding the load of 12Mw. This will result in a condition so that the generator should run in a greater speed and which will be greater than the rated rpm. Thus the generator will eventually stop generation. These is an example.

In the real grid there will be a surplus of 5% of total demand. if this mw cannot be supported by the machines then eventually the load is passed from one genrator to other. The end result will be gradual failure of all the generators. There is an additional power of 800Mw in our Southern grid in India which covers 4 states and 2 UTs. The real problem occurs when the heavy generators will go into a standstill. These will really affect the system.

Now we will have a look on why restoring the system is difficult.The main problem remains on identifying the problem, where the problem occured, who is responsible for the problem, is the problem going to occur after restoration also. After realising the problem and the ways to succumb it, Generators are put into service one by one. Thus if there are any problem, the machines will go as soon as they are put into service. So if the problem is not recognised correctly this will happpen again. Thus resulting in much more delay. And when the generators are put into service, the total load won't be applied to the generators. Since they cant meet the demand all of a sudden. Its like applying the full power to a standstill car.This will effect the generators life. So load will be applied to the machines step by step. Thus the system is restored .

The Grid is very complex one to understand . It is Huge due to its size. It is complex due to the load sharing method, due to the various types of generators used, loads and the complex calculation.