CHARLES ISIADINSO

SUBSTATION & SUBSTATION

A switchyard is a substation without step-up or step-down transformers. It located just outside the power station and operates only at a single voltage level. Its primary use is to deliver power generated to the grid. The 3-phase electric current leaves the generator via isolated-phase buses, which are connected to a generator busbar (a metal bar used to transfer electricity to the switchyard), each isolated-phase bus is connected to a separate generator busbar as a preventive measure, so if there is a problem in one busbar, the other two phases aren’t affected and the plant can still supply electricity. This is especially useful during maintenance and repairs as one busbar can be taken offline, but the plant can still supply the grid, even if it is two-third power.

Substations, however, use a generator step-up transformer to step-up (or down) the voltage of electricity flowing through transmission lines. Substations exists along the transmission network to step-up (or down) the voltage of electricity to an appropriate level to comply with consumer needs.

The grid works such that electricity leaving the plant is stepped-up for efficient transmission; the voltage is too high to be consumed directly so as the transmission

CHARLES ISIADINSO

network approaches consumers (e.g. homes and businesses), it passes through a substation, which steps the voltage down. Electricity leaving this first substation is usually still at a very high voltage so, further along the line, electricity passes through another substation. The number of substations is determined by the power requirements of the consumers. For example, if there is a large bread factory on the same line, but ahead of, a small town, there will be a substation to step down the voltage to one close to the requirements of the bread factory, but still significantly higher that that of the town first then the electricity will then flow through another substation further closer to the factory, which will step voltage down to meet the factory’s requirements before being supplied to the factory. After the factory, electricity will flow through a further substation and here the voltage will be stepped-down to one suitable for the town. Small step-down transformers will reduce the voltage further before electricity is supplied to homes and shops. Electricity leaving the town passes through a substation to step-up the voltage again so it can be efficiently transmitted to the next set of consumers.

The substation also has provisions for bypass, so if electricity is being transmitted to a set of towns, one small another very large, not all electricity entering the small town substation will be stepped-down, some will bypass the substation and carryon to the large town substation, this is especially the case if the distance between the two towns is large. A typical mid network substation is shown below, with the blue line being the bypass line and the red lines, being the step-up (or down) line(s).

Components of the substation above are:

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1. Primary and secondary power lines (1 and 12 respectively)

2. Ground wire3. Transmission lines4. Transformer (used to measure primary line voltage)5. Disconnect switches6. Circuit breakers7. Current transformer8. Arrester/insulators (protects against lightning)9. Main step-up (or down) transformer10. Control building11. Security fence

REFERENCE:

1. "Transformer." Wikipedia. Wikimedia Foundation, 16 June 2014. Web. [Accessed 16 June 2014].

2. "Electric Power Transmission." Wikipedia. Wikimedia Foundation, 15 June 2014. Web. [Accessed 16 June 2014].

3. "Electrical Substation." Wikipedia. Wikimedia Foundation, 30 June 2014. Web. [Accesses 03 July 2014].

4. "Substations." High Voltage Substations & Substations. Beta Engineering, n.d. Web. [Accessed 03 July 2014].

5. "Busbar." Wikipedia. Wikimedia Foundation, 26 June 2014. Web. {Accessed 03 July 2014}.