Electrical Power Generation & Generating Sub-Station of 11KV/400KV

There are many method in the world to generate electrical power but the most important method at commercial scale is to keep the conductor stationery and rotate the magnetic field or keeping the magnetic field stationery and rotating the conductor. The first method is used widespread in the world. Apart from this, electrical generator is also of mainly three types 

1. Inductor Generator 

2. DC Generator 

3. Synchronous Generator 

 But at commercial scale, synchronous generator is used & most commonly it is also known as Alternator. The alternator is used because it provides the 3-phase power which can be supplied to the long distance by the use of 3-phase power transformer which is very costly & lossey operation in case of DC power transmission. The power from alternator is supplied at fixed frequency which is not load depended whether alternator is loaded or not loaded. This freqency depends on the speed of the alternator. 

On the basis of speed of alternator, there are two types of alternator

1. 2 pole alternator which has 3000 RPM rotating speed at 50 Hz frequency, its maximum capacity is 1200MW

2. 4 pole alternator which has 1500 RPM rotating speed at 50 Hz frequency, its maximum capacity is 1550MW

These alternator requires the mechanical power to rotate which is obtained from steam turbine whose shaft mechanically coupled with the rotor of the alternator. This steam turbine achieved the steam pressure whether from coal based power plant or nuclear power plant. For generation of the same power level, the alternator which run on steam turbine has more length of rotor with less diameter while the alternator which runs on water turbine has less length of rotor and more diameter because water turbines runs on less speed. 

The transformer commercially available for transmission has not the capacity more than 1100 MVA in the world. So we can transmit the power not more than 1100MVA in a single line, even if there's availiablity of 1500MVA. Therefore for utilizing the generator capacity, 3 different single phase transformer are used in each phase to get availablity of the capacity of the generator & most of the time delta connection are used in transformer at generator side while load side has star connection at transformer. But it is not necessary in usual practice, directly 3 phase transformer taken for transforming the energy from the generator to grid as shown in figure - 1

Figure-1

The conductor from transformer passes through the Surge arrester or lightening arrester(LA) and Current transformer (CT) to measure the current of the line and then conductor tightened to gantery where Potential Transformer (PT) is used to measure the voltage of the generating station. Then this conductor taken to another conductor through insulator disc which support the weight of the conductor at gantery and provides the insulation between gantery and main conductor. Another gantery provides support structure for power transmitting bays to the main bus which is also known as generating bus as shown in figure - 2 below

Figure - 2

The conductor from gantery goes down to the isolator as highlighted at Figure - 2 and then again surge arrestor, SF6 circuit breaker (CB), lightening arrestor and then connected to the generating bus. There are two generating bus, both the generating bus connected to a single transformer, so there are two bays from the gantery which connected to the both generating bus. Similarly from second transformer shown in figure-1 also connected in same manner to the generating bus. This generating bus extended for transmission of power, therefore another 4 bays erected as shown in figure - 3 & these 2 bays from one generating bus for each transformer power ended to another gantery from where two circuits supported on the gantery are send to the power transmitting tower. as shown in figure - 3 below 

Figure - 3