Electrical Grid System

(2) National grid : Different regional grids are interconnected together to form a common grid for the nation, it is therefore called as National grid. 

• Each state has a power grid corporation.
• In our country there are total five electricity grids as : (i) Northern (ii) Eastern, (iii) North Eastern, (iv) Southern and (v) Western Grid 
• Several states are connected together by the above grids.
• Power grid corporation of respective states look after the grids.

Causes, Impacts and reasons of Grid system fault :

1. Power suppliers draw excessive power from the grid.
2. Failure of equipment is grid.

• Due to both these reasons, cascading effect is produced. This results in total “Black-out of the grid system

Effects of Excessive Power Drawing :

• This happens due to more demand of that supplier which creates “demand-supply gap”.
• It is over draining of grid system.
• It affects generators in the plant, they run slow causing supply frequency abnormal of the limit 49.5 Hz to 50.2 Hz.
• Effect of this causes tripping of the grid.
• Sudden power loss causes grid-failure or black-out.

Effects of Failure of Equipments :

• This finally produces cascading effect.
• If some elements of equipments fails completely or partly, the load from it gets shifted to the nearby equipment in the system.
• Naturally that element gets overloaded.
• This overloaded element naturally tries to shift this overload on its nearing element and thus shifting of load from one element to the nearby element continues.
• This is cascading effect by which working of the system is affected and thus there is chance of failure of the system.

Impact on Grid failure :

The grid failure affects in many ways like :

• Industries like metallurgical, pharmaceutical, bio-chemical etc. are badly affected due to failure of supply.
• Their production system comes to halt.
• Their process time is critical and Industries suffer from huge losses in raw material as well as unprocessed material.

Impact on Health Care :

• In clinics and hospitals, there are so many medical equipments for treatment and life supporting system. Due to electricity failure for a longer period, problems are created. Many machines need continuous electricity supply. 

Impact on Water Supply Systems :

• Water supply system for drinking water, water supply for irrigation purpose needs electricity for pumping work. These systems are affected by non-supply of electricity for a longer period.

Impact on Elevator System :

• Many malls, multistorey building towers, industry material handing-transportation on upper places need lifts/ elevators.
• These works are affected by non-supply of electric power from the grid.

Impact on Communication Systems :

• The entire network of communication system stops functioning due to electricity failure.
• Electricity is frequently and continuously required for the batteries to get charged which is the main component of communication system.

Impact on Transportation :

• Electric trains, tramways, local trains and the complete traction system needs continuous electricity supply from the grid system. So this working area may come to standstill if supply remains affected by grid failure.

Impact on Power Stations :

• For restoring the “Grid” it may require considerable time as power stations like steam-thermal power stations need some finite time to start and function fully to supply power to the grid network.

• It is the effect of complete interruption of electric power over a large area over an extended period of time. 
• Blackout occurs due to major faults in power system or cascade tripping of the grid system. 
• Blackout occurs so sudden without pre-warning or any pre-indications.

Brownout :

• This term is used for intentional or unintentional drop in the supply voltage.
• Intentional means supply voltage is reduced to prevent the blackout.
• Unintentional means the voltage drop includes voltage sag on line which causes “voltage-dip for a small duration of time.
• Due to this, sensitive devices, equipments, machines are affected due to voltage fluctuations.

Difference between Blackout and Brownout :

Blackout	Brownout
(i) It is the complete interruption of supply.	(i) Supply is at reduced voltage.
(ii) causes-major fault, cascade tripping.	(ii) Cause is increased power demand, so power is supplied at reduced voltage.
(iii) Supply continuity is nil.	(iii) Supply continuity is assured.
(iv) It is not deliberate.	(iv) It can be deliberate.
(v) All devices come to half.	(v) Functioning of digital devices is affected. It may cause malfunction.
(vi) No questions of voltage fluctuations since supply is not present.	(vi) Voltage fluctuations are present.
(vii) Equipments are tripped off from the supply.	(vii) Equipments sensitive to voltage fluctuations are likely to fail.
(viii) The system resumes if the process is tedious and complicated.	(viii) No such issue
(ix) The economic loss on the account of blackout is huge.	(ix) The economic loss is comparatively less.