Table of Contents
What is a Voltage Protection Relay?
A Voltage Protection Relay is a microprocessor based device that activates by creating a magnetic field as long as there is current passing through. It transmits the current, while protecting motors and circuits against over/undervoltage, phase failures/absences and phase sequence faults.
Thanks to voltage protection relays, any low or high current going to devices are prevented. Only the necessary amount of current is passed to the device.
Also known as Voltage Control Relay, Voltage Protection Relays continuously follow the voltage passing through the device, and activates when set boundaries are surpassed. Because of this, only the set voltage passes through the device and any damage that could be caused by voltage fluctuations is prevented.
Voltage Protection Relay Connection Diagram
Applications of Voltage Protection Relays
Voltage Protection Relays are used in many areas, such as:
- Power Factor Correction panels,
- Control systems that could be damaged from low or high voltage in single phase and three phase systems,
- Electronic Control Circuits or Capacitor Groups,
- Protection of Motors, Air Conditioners and Compressors.
Voltage Protection Relays are named after different purposes and their usage on various circuits. They are categorized into different types based on their voltage adjustment range, phase sequence control, and selectable pull-in or trip delay settings. Some of the functions include:
- Overvoltage and Undervoltage Protection
- Adjustable Voltage Protection
- Phase Failure/Absence Protection
- Phase Sequence Protection
Overvoltage and Undervoltage Protection
The voltage protection relay activates when there is a nominal overvoltage or undervoltage value of 40% in any of the phases.
Adjustable Voltage Protection
The output relay activates when the voltage surpasses the set boundaries longer than the set delay time. If the voltage returns back inside the set boundaries during the set delay time, the relay holds its state. There is a hysteresis curve in a certain value to protect the system from small voltage changes.
Phase Failure/Absence Protection
The system overheats when there is a phase failure or absence. The output relay drops out to prevent the system from overheating. It continues to pull in when the phases become normal again.
Phase Sequence Protection
The relay activates when the order of L1, L2 and L3 phases are wrong, protecting the system.