Electrical Grid Components and Voltage Transformations

Electrical Grid Components and Voltage Transformations

The Electrical Grid, consists of:

• Power Plants: Where electricity is generated.

Substation Power Transformers: Where voltage is stepped up for transmission.

• Distribution Transformers: Where voltage is stepped down for distribution.

The purpose of increasing voltage is to reduce transmission losses. Today, we'll discuss electrical losses within the grid.

As shown in the attached image, a power plant generates at 11 kV with 54.5 Amperes. This voltage isn't suitable for long-distance transmission, hence it's increased using a Step-Up Transformer.

The voltage is raised to 66 kV, 132 kV, 220 kV, 400 kV, or 500 kV. Higher voltage means less current for the same power, reducing the conductor cross-sectional area needed, which in turn lowers the cost of building transmission lines, whether they are overhead (OHTL) or underground (UGC).

Also, less energy is lost in this process:

Power Losses = I² x R

In the image, the voltage is raised to 500 kV with a current of 1 Ampere.

Electricity Transmission:

Electricity is transmitted from power plants through overhead (OHTL) or underground cables (UGC) to transformer stations. Here, voltage is reduced with Step-Down Transformers:

• From 500 kV to 220 kV with 2.27 Amperes.

• Then from 220 kV to 66 kV with 7.58 Amperes.

• Further reduced to 22 kV (medium voltage) with 22.7 Amperes.

• Then to 11 kV with 45.4 Amperes.

Finally, Distribution Transformers reduce it to 415 V for industrial and small workshops, and 230 V for residential (Phase to Earth).

This explanation is simplified for the electrical grid in Austria, but the concept is universal.

The colors used in the explanation:

• Red: Power generation.

• Blue: Transformer stations.

• Green: Distribution transformers.

• Black: Consumers (residences, commercial centers, hospitals, etc.).

It's crucial to understand that ideally, input power (Pin) should equal output power (Pout). However, in reality, there are losses in the grid. No power grid in the world operates without losses, which can range from 2% to 6% in a well-maintained grid.

These losses are:

- Technical losses: Due to aging equipment, lack of maintenance, not using capacitors or reactive power compensators, and not employing modern measuring devices to identify grid faults.

- Commercial losses: Occur from illegal connections bypassing meters, theft in informal markets, etc.

This provides a basic overview of how electrical grids operate and manage power losses.