Power Transformers

A transformer is a device that transfers electrical power from one circuit to another by electromagnetic induction. They are most often used at substations where high-voltage transmission lines meet with lower-voltage distribution lines.

Transformers play an important role in the electric grid because they allow for voltage conversion and isolation.

Some other key roles include: providing backup power in case of failure; controlling voltage levels in order to match supply and demand; converting alternating current (AC) into direct current (DC); and improving efficiency through reduced line losses.

How do transformers work?

Transformers work by transferring power through electromagnetic induction. This process occurs when a current flows through the primary coil, which creates a magnetic field. This magnetic field then induces a current in the secondary coil. The strength of the induced current is proportional to the strength of the original current and the number of turns in the secondary coil. This is why transformers are often rated in terms of kVA (kilovolt-amperes), which is a measure of the amount of power they can transfer.

Types of power transformers

There are several different types of power transformers, but the most common are:

  • Distribution transformers: These are used to reduce high-voltage currents to safer levels for use in homes and businesses. They typically have a rating of less than 10 kVA.
  • Power transformers: These are used to increase or decrease the voltage of AC currents. They typically have a rating of more than 10 kVA.
  • Autotransformers: These are used to change the voltage of a single circuit. They do not have a separate primary and secondary coil, but instead share a common coil. This makes them cheaper and smaller than traditional power transformers.
  • Impedance transformers: These are used to match systems with different impedances (number of turns) or to reduce voltage.

Where transformers are located

Transformers are most often used at substations where high-voltage transmission lines meet with lower-voltage distribution lines. Some common locations for transformers include:

  • Substations: This is where high-voltage transmission lines meet with lower-voltage distribution lines.
  • Power plants: This is where AC currents are converted into DC currents.
  • Manufacturing facilities: This is where large amounts of power are needed to run machinery.

  • Power poles: This is where electrical power from the grid enters homes and businesses.

There are thousands of power transformers in the Texas electricity grid. Of these, most are distribution transformers that perform the final voltage step-down before power is sent into homes and businesses. There are also many autotransformers and impedance transformers in the grid.

What Power Transformers look like

Transformers come in all shapes and sizes, but they typically have two or three cylindrical coils of copper wire. The primary coil is the one that is connected to the high-voltage transmission lines, while the secondary coil is connected to the lower-voltage distribution lines.

They can be found in a variety of colors, but most often they are either green or yellow.

Transformer on a Power Pole
Pole-mounted power transformer image credit

Transformer at a Transmission Substation
Transformer at a Transmission Substation image credit

Blown transformers

Blown transformers can be a serious problem for the electric grid. If a transformer fails, it can cause a power outage or damage to equipment.

Transformers are typically very reliable, but they can occasionally fail due to overloads, short circuits, or lightning strikes.

The average power transformer has a service life of approximately 40 to 50 years. However, this number can vary depending on the environment where the transformer is located.

When a transformer fails, it can release a large amount of energy. This can cause a fire or explosion, which can damage property and injure people.

In order to prevent these incidents, it is important to have an emergency plan in place. This plan should include procedures for safely shutting down the power and evacuating people from the area.

Repairing blown power transformers can be difficult and sometimes dangerous.

Not only must crews deal with high-voltage electricity, but some transformers contain PCBs (polychlorinated biphenyls) which are harmful when released into the environment. To avoid this problem, many power companies are moving towards the use of solid-state transformers, which contain no harmful chemicals. Although these can be more expensive than traditional systems, they last much longer and require less maintenance.