Potential Transformer

Voltage transformers (also called potential transformers, abbreviated PT) and transformers are similar and are used to change the voltage of the instrument. Voltage transformers are used to transform voltage, mainly for power supply to measuring instruments and relay protection devices, to measure the line voltage, power, and electrical energy, or to protect valuable equipment, motors, and transformers in the line in the event of a line fault, voltage transformers in the power system play a key role in helping to ensure that the stability of the power system, the quality of the power system and security, but also to support the energy management and monitoring. monitoring. They are an important tool for power system monitoring and management.

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How Does a Voltage Transformer Work?

The potential transformer is a power measurement device used to measure the voltage in a high-voltage power system and reduce it to a safe level that can be measured or monitored. Its principle of operation is based on the transformer method and is divided into two windings: The main winding and the secondary winding. The main winding is usually located in a high-voltage power system and introduces the high voltage of the system. This winding is usually wrapped in an insulating material for safety. The secondary winding is the part that connects to the measuring device or meter and has a relatively low number of winding turns and therefore a lower voltage. The secondary winding is wrapped around the main winding and is usually isolated using an insulating material to prevent current flow.

The principle of voltage transformer is to use a magnetic core through which a high voltage alternating current field (the primary winding) is passed and wound into several turns to form a magnetic field, while another low voltage alternating current field (the secondary winding) is wound around the core, thus generating a current under the action of the magnetic field. When a high voltage flows through the main winding, a lower voltage than that of the main winding will be induced in the secondary winding according to the transformer principle.

This voltage reduction ratio is determined by the winding turns ratio. The output voltage of the secondary winding is proportional to the input voltage of the main winding in a known buck ratio. A change in the AC electric field is therefore able to change the strength of the current in the secondary winding and thus transform the voltage. This output voltage can be connected to a measuring device such as a voltmeter, a digital acquisition system, or a protection device for voltage measurement and monitoring.

The Main Types of Voltage Transformers

The installation location can be divided into indoor type and outdoor type. 35kV potential transformer and the following are made into indoor type. 35kV above is made into outdoor type.

Single Phase Potential Transformer

According to the number of phases can be divided into single-phase potential transformer and three-phase potential transformer type (35kV and above can not be made into three-phase type). Single-phase voltage transformers work according to the principle of electromagnetic induction. They contain windings around an iron core, through which the incoming high-voltage signal can be stepped down to a measurable low-voltage signal. This conversion process allows the voltage signal to be efficiently transmitted to other equipment for processing and analysis.

Three Phase Potential Transformer

Three-phase voltage transformer is a device used to measure and monitor voltage in a three-phase power system. They typically contain three separate but identical transformers, each used to measure the voltage of one phase. Three-phase VT are used to accurately measure the voltage value of each phase to monitor the voltage level of the power system. They can be used to monitor voltage waveforms in real-time to ensure that power quality standards are met. Three-phase voltage transformers are used in conjunction with protective devices to detect voltage abnormalities, such as overvoltage or Undervoltage, to trigger protective devices to protect power equipment and systems. In the industrial and commercial sectors, they help monitor power consumption and support energy management and energy conservation measures.

The number of windings can be divided into double-winding and three-winding voltage transformers, and three-winding voltage transformers in addition to the primary side and the basic secondary side, there is a set of auxiliary secondary sides, for grounding protection.

Oil-immersed Potential Transformer

The insulation can be divided into dry, cast, oil-immersed, and gas-filled. Dry-type voltage transformer structure is simple, with no fire and explosion hazards, but the insulation strength is low, only for 6kV below the indoor device. The cast voltage transformer structure is compact, easy to maintain, and suitable for 3kV~35kV indoor power distribution equipment. Oil-immersed potential transformer insulation performance is better and can be used for more than 10kV outdoor power distribution equipment. Inflatable voltage transformers are used in SF6 fully enclosed appliances.

 According to the Principle of Operation

• Electromagnetic Voltage Transformer: Electromagnetic induction is the use of the principle of proportional conversion voltage or current equipment.
• Capacitive Voltage Transformer: Capacitive voltage transformer (CVT) is a series capacitor voltage divider, and then by electromagnetic transformer voltage reduction and isolation, as a meter, relay protection, etc., a potential transformer, capacitive voltage transformer can also be the carrier frequency coupled to the transmission line for long-distance communication, remote measurement, selective line high-frequency protection, remote control, teletype, and so on.
• Electronic Voltage Transformer: A device consisting of one or more voltage or current sensors connected to the transmission system and the secondary converter, used to transmit a quantity proportional to the measured quantity, supplied to measuring instruments, meters, and relay protection or control devices.
  
  

Application of Voltage Transformer

Voltage transformers can be used to convert high voltages into standard secondary voltages of 100V or lower voltage in a proportional relationship to supply protection, metering, and instrumentation devices. At the same time, the use of voltage transformers can isolate high voltages from electrical workers. Although the voltage transformer is also by the principle of electromagnetic induction equipment, its electromagnetic structure relationship with the current transformer is compared to the opposite.

Voltage transformers are used in power systems to monitor voltage levels and ensure stable operation of the grid. They help power companies manage the distribution of power to meet the demand for electricity at different times and locations. VT are used in electric vehicle charging stations to ensure that voltage is controlled and monitored when charging batteries to prevent overcharging or over-discharging. Voltage transformers are built into many household appliances such as TVs, washing machines, and refrigerators to ensure they operate at the correct voltage while protecting the user from voltage fluctuations.

Many electronic devices, such as computers, servers, and networking equipment, use poential transformers to protect them from electrical problems such as overvoltage, voltage fluctuations, and flicker. In solar and wind energy systems, voltage transformers are used to monitor and control power output to ensure the efficiency and reliability of renewable energy systems. In smart homes, voltage transformers are used to monitor power consumption and grid connection status to support energy management and automation control. Voltage transformers are used in the field of power quality analysis to monitor voltage waveforms to identify problems in the power system, such as harmonics and transients.

How to Install a Voltage Transformer?

• Selecting the Installation Location: First, determine where the voltage transformers will be installed. Typically, they are installed on the main cables or wires of the power system. Make sure that the location chosen has the proper voltage level and access conditions.
• Disconnect the Power: Always disconnect the power system before performing any installation work to ensure safety. Follow all safety protocols and procedures.
• Connecting Wires: Connect the voltage transformer wires to the electrical system. Ensure that they are properly connected and that proper insulation is used to protect the connection points.
• Calibration and Testing: After installation, the voltage transformer must be calibrated and tested to ensure accuracy and reliability. This usually requires specialized instruments and qualified technicians.
• Fixing and Encapsulation: Install the voltage transformer in its location and secure it there using suitable fixings. Ensure that the transformer is well-protected physically.
• Earthing: Ensure that the voltage transformer is connected to a suitable earth connection, according to safety regulations, to protect the equipment and personnel from the hazards of earth currents.
• Monitoring System: After the installation is complete, make sure that the monitoring system can read and record the data provided by the voltage transformer. Perform some tests to verify that everything is working properly.
• Restoring Power: After the installation is completed and tested, the power system can be restored to operation.
• Documentation: Record all installation and testing procedures for future maintenance and troubleshooting.
• Please note that voltage transformer installations usually need to be performed by trained professionals to ensure safety and performance. All applicable safety codes and standards must be observed.