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Substation 1

Power transformers are the most important equipment in an electrical substation and are used to change voltage levels, regulate voltage, and control reactive power flow. They operate at voltages from 138kV to 765kV and capacities from 1,000MVA to 50MVA. Circuit breakers are mechanical devices that can make, carry, and break currents under normal and abnormal conditions like short circuits.

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Bhaskar Das
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15 views2 pages

Substation 1

Power transformers are the most important equipment in an electrical substation and are used to change voltage levels, regulate voltage, and control reactive power flow. They operate at voltages from 138kV to 765kV and capacities from 1,000MVA to 50MVA. Circuit breakers are mechanical devices that can make, carry, and break currents under normal and abnormal conditions like short circuits.

Uploaded by

Bhaskar Das
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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3.3.

1 Power Transformer

Power transformers are the most important equipment in an electrical substation. They are different from
distribution transformers. They perform different functions. They are used:

• To Change the voltage from one level to another,


• To regulate the voltage level,
• To control the flow of reactive kilovolt-amperes in the power system.

Power transformers installed in transmission substations will normally be constructed for and operate at
voltages in the range of 138,000 volts to 765,000 volts or higher.

Figure 9: Power Transformer

Most substations will have three-phase transformers. Some substations will have three single-phase
transformers in parallel installed in a bank. Often, a fourth single-phase transformer will be located at
the substation to serve as a spare. If one of the transformers connected in the bank fails, the spare is
energized to expedite the restoration of electric service. The capacity of the transmission substation
transformers will normally be in the range of 1,000 MVA to 50 MVA.

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Figure 10: Three single phase transformers in bank

Power transformers installed in distribution substations will normally be constructed for and operate at
the lower voltages and smaller capacities. The voltages will generally be in the range of 161,000 volts
to 4,160 volts and the capacities in the range of 50 MVA to 5 MVA.

3.3.2 Circuit Breaker

A circuit breaker is a mechanical switching device, capable of making, carrying and breaking currents
under normal circuit conditions and making, carrying for a specified time and breaking currents under
specified abnormal circuit conditions such as those of short circuit. The contacts of the circuit breakers
are opened and closed by mechanical linkages manufactured from insulating materials and utilizing
energy from compressed air, electric magnets, or charged springs.

Some of the high-voltage circuit breakers utilize compressed air to operate the contacts and interrupt the
current flow when the contacts are open. Operation of the circuit breakers is initiated, utilizing dc cir-
cuits, by manually operating a switch, by remote operation of supervisory control equipment, or by
relays that automatically recognize predetermined abnormal conditions or electrical failures in the sys-
tem. Various types of circuit breakers used in high voltage substations are.

• SF6 Circuit Breaker


• Oil Circuit Breaker
• Air Blast Circuit Breaker
• Vacuum Circuit Breaker

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