CHARLES ISIADINSO

GENERATOR STEP-UP

TRANSFORMER (GSU)

The generator is connected to the GSU via a generator circuit

breaker, so the next stage in the electricity generation and

transmission process is the GSU.

After power has been generated, it needs to be transmitted from

the plant to consumers. There are two steps from the plant to the

consumers:

1. Power plant to electrical substation (power transmission)

2. High-voltage substations to consumers (power distribution)

The role of a transformer is to modify the voltage of current

coming into it, either by increasing it (stepping-up) or decreasing it

(stepping-down), this is done using the law of electromagnetic

induction. Voltage is usually stepped up from the power plant

output voltage to the transmission line transmission voltage. And

is stepped back down from the transmission voltage to a lower

more manageable voltage at electrical substations and stepped

down further before reaching the consumer.

Power plant output has to be transmitted to the consumers, and

one plant can be responsible for supplying hundreds of homes and

businesses, hundreds of miles away, with electricity. This translates

to a grid systems comprising of miles of cables connecting the

plant to its consumers. Energy is lost when transmitting electricity

over long distances; however, at higher voltages (greater than 120

kV) less energy is lost than at lower voltages, for this reason, the

plant output voltage is stepped up before being transmitted.

A transformer unit consists of:

1. Two sets of bushings, one insulate the conductors when they

enter the generator the other set insulate when the

conductors leave the generator

CHARLES ISIADINSO

2. Radiator fins/fans, which is responsible for cooling oil in the

transformer

3. Conservator tank, which provides and environment for oil to

expand on heating and contract on cooling, reducing waste

4. Three voltage transformers, which carry out the voltage step-

up or down

5. Tap changer, which controls the amount of voltage change

by reducing the number of effective loops in a layer of

windings, and

6. Explosion vent, which protects the unit in the event of a

major fault

The voltage transformer is made up of a laminate steel core

surrounded by two layers of conductor windings (usually copper

wire), each with a different number of loops. The more loops in a

winding, the higher the voltage of the current flowing through the

winding. The voltage transformer is assembled with the core in the

center, the winding layer with fewer loops (low voltage windings)

at the end and then layer with more loops (high voltage windings),

between the core and the low voltage windings. In a generator step-

up transformer, current enters the generator through a conductor

connected to the low voltage windings, induces a magnetic flux in

the iron core, and this flux induces a current in the high voltage

windings, which is connected to a conductor that connects to the

transmission lines. The reverse is the case for a step-down

transformer.

CHARLES ISIADINSO

REFERENCE:

1. "Generator Step-up Transformers (GSU)." - Power

Transformers. N.p., n.d. Web. [Accessed 16 June 2014].

2. "Transformer." Wikipedia. Wikimedia Foundation, 16 June

2014. Web. [Accessed 16 June 2014].

3. "Electromagnetic Induction." Wikipedia. Wikimedia

Foundation, 06 Oct. 2014. Web. [Accessed 16 June 2014].

4. "Electric Power Transmission." Wikipedia. Wikimedia

Foundation, 15 June 2014. Web. [Accessed 16 June 2014].