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Tuesday, September 30, 2014

What is Electrical shock? How much our body withstand with electricity? How to protect ourself from earth leakage current?

Electric shock and its prevention
We are very often or rarely sense electric shock. Then a question arises technically , What is Electrical shock? How much our body withstand with electricity?
In Practical, when we are in contact with a live electric wire or touching an electrical equipment with leakage current, a current flow in our body, then we sense the shock.

What is the safe limit of this current?
there are 5 conditions, if the current flow persist in our body and the current limits is 
1) if the current is < 2 mA(Milli Ampere), it is insensible, safe
2) if the current is 2 mA to 10 mA, it is sensible, Let go current and Harmless
3) if the current is10mA to 25 mA, Muscular Contraction occur.(Sensing the shock)
4)  if the current is 25 mA to 50 mA, Ventricular Fibrillation occur, Immediate attention is required, within 20 minutes, we have to give defibrillator to active our heart functioning.
5) > 50 mA - fatal.

How to protect ourself from earth leakage current?
1. Earthing is necessary and must for the electrical appliances used in our home.
2. Now a days ELCB ( Earth Leakage Circuit Breaker) is available in the market, which can be installed  in our house wiring along with other Switchgear. It breaks the current if the earth current is >30 mA range.ELCB will be tripped off automatically, whenever the current crosses the safe limit.
ELCB (Illustration purpose only)

Saturday, September 27, 2014

Solar Net Metering



Solar Net metering
As the national electrical power demand increases, alternate energy sources play a vital role to meet out some of the energy crises. In particular, the Solar PV system’s growth is very rapid.

Net meter is a bidirectional energy meter which indicates the energy usage by a consumer and excess energy produced by the consumer and exported to the utility grid.
In a grid connected Solar PV system, the excess energy generated can be exported to the utility grid. The net meter tracks the difference of excess energy fed back to the grid and the energy consumed by the consumer.
There are two conditions,
  1. If the solar energy generated units is less than the load , then the net meter runs forward, the consumer has to pay the utility company
  2. If the solar energy generated units are greater than the load, then the net meter runs backward, the consumer will be credited for excess energy.
The net metering usage and its policy differ from state to state. The tariff also differs. There will be an agreement between the consumer and the utility grid company.
 Merits:
1.      As the consumer is credited for excess energy, there will be financial benefit.
2.      As the system is grid connected, no need of battery storage, its cost involved and free from maintenance.
3.      No need of two meters separately for measuring energy consumption and excess energy exported to the utility grid.



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