The study of 220kV power substation (equipment details)

220kV substation equipment

The present-day electrical power system is A.C. i.e. electric power is generated, transmitted and distributed in the form of alternating current. The electric power is produced at the power stations which are located at favourable places, generally quite away from the consumers. It is delivered to the consumers through a large network of transmission and distribution.

At many places in the line of the power system, it may be desirable and necessary to change some characteristic (e.g. voltage, A.C. to D.C., frequency, Power factor etc.) of electric supply.

This is accomplished by suitable apparatus called Substation. For example, generation voltage (11KV or 6.6KV) at the power station is stepped up to high voltage (say 220KV or 132KV) for transmission of electric power. The assembly of apparatus (e.g. transformer etc.) used for this purpose is the substation.

Similarly, near the consumer‟ s localities, the voltage may have to be stepped down to utilization level. This job is again accomplished by a suitable apparatus called „Substation’.

About 220 kV substation ‘Passiana’

220 KV Passiana substations is one of the important substations of Punjab State Transmission Corporation Limited (PSTCL). It is the main source of power supply in the district of Patiala. The grid 220 KV substation, Passiana is situated 7-8 km from bus stand of Patiala to Samana Road.

Until 2007 it was transmitting 66KV energy and on 29 July 2008 it was up graded to 220KV substation.

Specification of used transformer

At Passiana substation transformers manufactured by B.H.E.L, A.B.B, T.A and E.C.E are installed with their power ratings ranging from 20 MVA for 66/11KV to 100MVA for 220/66KV step down voltages.

The main purpose of these transformers is to step down the voltages from 220 KV voltage to 11KV voltages by the use of four different transformers installed in the substation.

These transformers are generally insulated upon lengths of rails fixed on concrete slabs having foundation 1 to 1 and 1/2 meter deep. These transformers are provided with the tap changers with the main aim of regulation of the voltage.

Busbars

If the busbars are of rigid type (Aluminum types) the structure heights are low and minimum clearance is required. While in case of strain type of busbars suitable ACSR conductors are strung/tensioned strain by tension insulator discs according to system voltages.

In the widely used strain type busbars stringing tension is about 500-900 kg depending upon the size of conductor used and tensioning is manual by means of rope pulleys or by pull lifts. It may also with the help of tractors.

Here proper clearance would be achieved only if require tension is achieved. Loose busbars would affect the clearances when it swings while over tensioning may damage insulators. Clamps or even affect the supporting structures in low temperature conditions.

The clamping should be proper, as loose clamp would spark under in full load condition damaging the busbars itself.

The busbar is provided with lightning protection to safeguard the equipment against direct stroke by providing aerial earth wire giving a protection at 30 degree i.e. height and earth wire such that all the equipment and bus bar should be covered with in this 30 degree.