Power transformers are undoubtedly the best known in the electrical industry, but there are also others that can be part of an electrical system. Next, we take a look at a so-called potential transformer, which is designed to reduce the voltage of a circuit.
Definition
A potential transformer is defined as an instrument transformer used for transforming voltage, from a higher value to a lower one. It reduces the voltage to a safe limit, which can easily be measured by an ordinary low-voltage device, such as a voltmeter.
This is connected across or parallel to the line, which is measured to record ratio or angle errors.
The transformer is designed to monitor single phase changeover voltages and three phase terminals. It has a main winding, and also a primary and a more secondary high voltage winding.
This special type of transformer allows a meter to take readings of electrical service connections with a higher voltage (potential) rating than the meter is normally capable of when it comes to power factor, and without errors.
Types
Essentially, there are three types according to their function: electromagnetic, capacitor and protection:
Electromagnetic
It is similar to the main transformer, where the primary and secondary windings are wound on a magnetic center. It operates based on a value higher or lower than 130 kV. The primary section is determined based on the phase, while the secondary is grounded. They are used in relays, measurements and high voltage networks.
Capacitor
The series of capacitors are connected to the main or secondary winding. Measures the output voltage coming out of the secondary winding. It is used for communication purposes that carry power line. It is the most expensive.
Protection (voltage transformer)
It can be single-phase or three-phase, and works with the highest precision.
Mistakes
In an optimally operating potential transformer, the primary and secondary voltage are directly proportional to the primary voltage and in phase opposition. But practically this cannot be achieved due to drops in primary and secondary voltage. Thus, the latter are introduced into the system. These are the types of errors:
- Angle: is the error between the voltage of the secondary terminal, which is exactly in phase opposition to the voltage of the primary terminal.
Applications
A potential transformer can be given the following uses:
- In relay and measurement circuits.
- To protect feeders.
- In communication circuits that carry an electric line.
- In electrical protection systems.
- To protect generators from impedance.
- In the synchronization of generators and feeders.
- As protection voltage transformers.
Advantages
- Ammeter and voltmeter can be connected, respectively, to monitor high current and voltage.
- Regardless of voltage or current detection, the low range meter level can be set with its help.
- The operation of these instruments is used to work on many forms of protective devices, such as relays and pilot lights.
- A single potential transformer can be used to control multiple instruments.
- A power transformer is used mainly to protect a system, since the windings of the instrument are not connected directly to the network, in the case of high voltage. For this reason, it is essential to reduce the input voltage, as well as to isolate the protection system from the primary network.
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