Types of Hydro Turbines

Impulse Turbine (Pelton wheel) for high heads.
Reaction Turbine (Francis) is used for medium heads.
Propeller Turbine (Kaplan) is used for low head.

In impulse turbine high velocity water from nozzles creates impulse on the buckets of pelton wheel.
In reaction turbine (Francis) the water pushes the turbine-blades by reaction.
In propeller turbine (Kaplan) the blades are pushed by propelling action of the water.

Earthing Switch

Earthing switch connect the live parts/ line conductors and earth. This switch is normally open.

Earthing switch is used to earth the live parts during maintenance and during testing. During maintenance although circuit is open still there are some voltages on line , due to which capacitance between line and earth is charged. Before proceeding to maintenance work the voltage s discharged to earth, by closing the earth switch.

1. Maintenance Earthing Switch: These are two or three pole units with a manual operating mechanism.

2. High Speed Earthing Switch: These are operated by spring energy. Spring is charged by motor-mechanism.

Circuit Breaker

Circuit Breaker: It is a device which is capable of making and braking a electric circuit under normal and abnormal condition such as short circuit. Circuit Breaker can be manually or remotely operated.Circuit Breaker are of  following types.:

1. Minimum Oil
2. Air blast
3. Air break
4. Vacuum
5. SF6 (Sulphur Hexaflouride)

Energy Efficiency of Electrical Machines.

In the generation of electrical power; electrical machinery, converting mechanical energy into electrical energy is found to be quite efficient. Therefore, for overall improved efficiency of the energy system, electrical energy conversion to other useful forms(mechanical, thermal etc) must be carried out as efficiently as possible. Since major portion of the generated power is consumed in electrical drives, emphasis must be laid on efficient use of these drives. High efficiency of electrical drives can be achieved by

(a) Judicious design of electrical machinery.

(b) Proper matching of motor-load combination.

1. Judicious Design:- 

For electrical drive,

                             Power Efficiency =  Power                                                                                                                                                                                                              (Power output + losses)

Energy Efficiency = Power Output * H(number of hours or days in service)

                       

Isolators

They are the disconnecting switches, which are used to disconnect the circuits under no load conditions. Isolators are very important for maintenance purpose because it provides safety as no live part is connected to the part of circuit under maintenance.

Megawatt ( Electrical Power Plant)

Power plants whether thermal or hydro are rated in Megawatt or Kilowatt. 

This rating denotes their power or in lay man language it tells the strength of power plant. More the strength more is the electricity generated by the plant.

Electrical Energy generated by a 100 MW Power plant:

We know we consume electrical energy in terms of Electrical Unit. 1 Electrical unit = 1 KWH= 1 KW * 1 H where KW=kilowatt and H=Hour Therefore a plant of 1 KW rating/capacity will produce one unit of electrical energy in one hour.

For Plant of 100 MW the electrical energy generated is as follows

Electrical Energy in one hour = 100 MW * 1 H = 100000 KW * 1 H = 100,000 KWH = 100,000 Units

Electrical Energy in one day = 100,000 Units * 24 = 2400,000 Units

Electrical Energy in one year = 2400,000 Units* 365 = 87,60,00,000 Units

Suppose rate of selling one unit = Rs 3

Annual Income of 100 MW power plant = Rs 3 * 876000000 = Rs.262,80,00,000

= Rs 263 crore

Instrument Transformer

Current Transformer: Current transformers are used for measuring,control and protection purpose. There current ratio of these transformer is high (e.g. 500A/5A) and voltage . Their location is decided by protective zone measurement requirement.

Voltage Transformer: Basically are of two types

     1. Electromagnetic Voltage Transformer.

     2. Capacitive Voltage Transformer.

The voltage ratio of these transformer is high. Used for measuring, control and protection purpose The secondary sides of these transformer are connected to protective relays