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What is the Voltage Monitoring Relay Working Principle?

An example of a voltage monitoring relay (1)
An example of a voltage monitoring relay
Resource: https://www.esmagazine.com

Are you new to voltage monitoring relays? If so, you may be wondering how they work. Here’s a quick overview of the voltage monitoring relay working principle. Among the things you’ll learn are the basics of how voltage monitoring relays protect electrical equipment and the different features they come with. But before delving into the working of these devices, here is a brief look at its basics.

Voltage Monitoring Relay Basics

A voltage monitoring relay is a type of monitoring relay used to detect (and react to) voltage changes in an electrical system, both DC and AC networks. These relays are also available for both single or three phase systems.

When voltages in an electrical system fall outside of the desired or expected range, it can cause major problems. For example, if the voltage gets too low, it can cause equipment such as electrical motors to draw more current and even burn out.

On the other hand, if the voltage gets too high, it can damage equipment or cause fires. That’s where voltage monitor relays come in. These devices are installed in electrical systems to monitor voltages and provide a safe shutdown of equipment in the event of a voltage abnormality.

In other words, voltage monitoring relays help protect against unacceptable voltage changes that could damage equipment or pose a safety hazard. It does so automatically, without requiring human intervention. Read below for more.

Voltage monitoring relay circuit diagram for motor protection
Voltage monitoring relay circuit diagram for motor protection
Resource: https://www.youtube.com/watch?v=7sf7XNiP0B8

Voltage Monitoring Relay Working Principle

Voltage monitoring relays are used to monitor the voltage of an electrical circuit and to trip then the voltage exceeds a preset value. They are typically used in electrical systems where voltage fluctuations are common, such as in industrial facilities or in areas with a high risk of lightning strikes.

The voltage monitoring relay working principle is based on the principle of magnetic induction. When a voltage is applied to a coil of wire, it creates a magnetic field. This magnetic field can be used to trip a switch when the voltage exceeds a preset value.

The voltage monitoring relay typically consists of a coil of wire and a switch. The coil of wire is wrapped around an iron core. When a voltage is applied to the coil, it creates a magnetic field. This magnetic field interacts with the iron core, which causes the switch to trip.

The sequences of events that characterize the voltage monitoring relay working principle are listed below.

  • An overvoltage, undervoltage or other irregularity (in the case of 3 phase relay) occurs in the electrical system.
  • The voltage monitoring relay, which is an overvoltage or undervoltage type (or both), detects the voltage change.
  • The relay trips a switch, which shuts off power to the affected circuit or electrical equipment.
  • After the set time delay, the voltage monitoring relay resets and power is restored to the circuit.

Note that the monitoring relay delay feature nay be set by the manufacturer and therefore, fixed, or it may be user adjustable. Both features suit different applications and needs.

Voltage monitoring relay installed in an electrical system
Voltage monitoring relay installed in an electrical system
Resource: https://youtu.be/FM5ubMp95hs

Voltage Monitoring Relay Features

Voltage monitoring relays are available in a variety of different styles, including panel-mount, DIN-rail mount, and plug-in. They are also available in a variety of different voltage and current ratings. As you can guess, that also means different working methods and user interfaces.

There are a few features that are common among voltage monitoring relays, and which determine their working. These features include:

Adjustable Voltage Setpoints

Most voltage monitoring relays have adjustable voltage setpoints. This means that the voltage at which the relay will trip can be adjusted to meet the needs of the application. The adjustments may be buttons, dials, or resistance screws on the relay itself.

Trip Delay

Many voltage monitoring relays also have a trip delay feature. This means that the relay will not trip immediately when the voltage exceeds the setpoint. Instead, there is a delay of a few seconds to allow for momentary voltage spikes. This feature helps prevent false or nuisance trips.

Trip Indicator

Many voltage monitoring relays also have a voltage or trip indicator, which is a light or other visual indicator that shows when the relay has tripped. This can be useful in troubleshooting electrical problems.

Digital screen

Instead of, or in addition to, a trip indicator, some voltage monitors have a digital screen that displays the current voltage. This type of relay, called the digital voltage monitoring relay, is often used in applications where it is important to monitor the voltage continuously.

Temperature Sensor

Some voltage monitoring relays also have a built-in temperature sensor. This can be used to monitor the temperature of the circuit in which the relay is installed. When present, this feature makes the monitoring relay more useful as a protection device.

Mounting Style

Voltage monitoring relays are available in a variety of different mounting styles, including panel-mount, DIN-rail mount, and plug-in. The type of mounting will be determined by the application. For example, DIN-rail mount relays are often used for circuit protection relays, while plug-in relays are often used for specific loads.

Some voltage monitors also have other features, such as current monitoring, phase loss detection, and ground fault detection. These additional features can be helpful in certain applications. For example, the relays used with 3 phase systems can sense phase faults including phase loss, phase reversal and phase unbalance.

Conclusion

The voltage monitoring relay working principle is generally identical across the different designs of the device: voltage change causes the relay to trip and disconnect electrical equipment. However, a few variations in the operation of the voltage monitoring relay exist, depending on the specific design and features of the device. That said, the vast majority of voltage monitoring relays use the basic principle of magnetic induction to trip a switch when the voltage exceeds a preset value.

William
William

I am William, Electrical Engineering Author. Dedicated to writing technical articles on Timer Relay, Monitoring Relay, Surge Protection Device and other electrical devices. With 7 years of writing experience, I am committed to providing accurate and in-depth expertise to my readers.

1 comment

    Could this be used to start and stop a generator powered battery charger?

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