What are voltage and current transformers and what are they used for?

Instrument transformers are very important in power engineering.

They help us perform accurate electrical measurements. We often use them to monitor power quality across the network. One of their functions is to work with protective automation systems to protect electrical equipment from situations such as short circuits and overloads. So what types of instrument transformers are there? How are they used?

There are two types of instrument transformers: current transformers and voltage transformers. In books, they are also called measurement transformers. As the energy sector continues to grow, these devices are becoming increasingly important. They play a role in many measurement and protection systems.

So how do current and voltage transformers work?

Although we often use them together in measurement systems, they are different. They operate differently. This also means that their usage methods are different.

Although we often use them together in measurement systems, they are different. They operate differently. This also means that their usage methods are different.

Current transformers

Current transformers are used to measure current that is dangerous to measure directly in a circuit. They have two parts: a primary winding and a secondary winding. This helps keep the high-voltage circuit and measurement equipment safe. When current passes through the winding, it creates a magnetic field. This field induces a current in the secondary winding proportional to the primary current. Then we can measure the current with a measuring device. The ratio of currents in the two windings is equal to the ratio of the number of turns in the windings. This allows us to measure current accurately. We can calculate the current indirectly.

Voltage transformers

Voltage transformers are used to measure voltage levels in a system. They can be phase or three-phase and have low power and low short-circuit voltage. They convert the primary voltage into a lower secondary voltage that is safe for measurement and protection devices. Voltage transformers have leakage reactance and minimal no-load current. They are used in high and very high voltage networks.

Main difference

The main difference between current and voltage transformers is what they measure and how they operate. Current transformers measure current, while voltage transformers measure voltage. Current transformers are connected in series in the circuit, while voltage transformers are connected in parallel. The secondary winding of a voltage transformer must never be short-circuited, and the secondary winding of a current transformer must never be left open. The grounding terminal of the winding must be securely connected to earth.

Instrument transformers are very important for substations and power lines. They provide information about electrical parameters such as current, voltage, power, and frequency. This information is essential for system control and regulation. Instrument transformers play a role in keeping the network safe and reliable. We use them in substations, switchgear, and distribution stations for tasks such as low-range measurements, remote measurements, and galvanic isolation. Their main purpose is to provide engineers and technicians with real-time information about the operating conditions of the network. This helps manage power quality and detect problems early. It also enables quick response to faults and helps prevent accidents. That is why instrument transformers are very important for the reliable operation of power systems.

Instrument transformers are used:

for measurements with low-range measuring devices

for measurements from equipment located far from the monitored circuit

for galvanic isolation between devices and high-voltage systems

By using instrument transformers, it is possible to keep the network safe and reliable. They ensure the protection of electrical equipment and the proper operation of the network. This is very important for maintaining the reliability and performance of power systems. Instrument transformers help achieve this by providing real-time information about network operating conditions. This information is essential for system control and regulation.