Supervision of minimum and maximum voltage in the installation
In power systems, both industrial and commercial, voltage stability is a key factor affecting the safety and reliability of equipment operation. Voltage monitoring relays, such as Relpol's RPN-.VM.-A400, RPN-.VM-A230 and RPN-.VC.-A400, enable effective monitoring of power supply voltage in the Umin/Umax range, protecting installations from the effects of voltage exceeding or falling below an acceptable level.
What are voltage monitoring relays within a certain Umin/Umax range?
Voltage monitoring relays, are devices designed for current monitoring of voltage values in a single-phase or three-phase network. Their task is:
- reaction to exceeding the set voltage thresholds (both lower and upper)
- disconnection of the receiver in case of abnormal voltage
- reconnection after stabilization of network parameters
The voltage ranges controlled by these relays are defined as:
- Umin - lower voltage threshold (minimum voltage)
- Umax - upper voltage threshold (maximum voltage)
Relpol relay models for Umin/Umax control:
- RPN-.VM.-A400 – relay for three-phase networks with adjustable switching thresholds
- Designed to monitor phase voltage in three-phase networks without neutral conductor (3˜400 V) or with neutral conductor (3(N)˜400/230 V)
- Ability to set Umin and Umax thresholds over a wide range of voltages
- Detection of missing one or more phases, asymmetry and phase sequence swapping
- Time delay for tripping and return - adjustable
- Version with one or two changeover contacts (depending on configuration)
Application - ideal for industrial switchgear, control cabinets and building automation systems, where full phase voltage monitoring is required in a three-phase network
Three-phase supervisory relay with adjustable switching thresholds
- RPN-.VM-A230 – relay for 230 V AC single-phase networks with adjustable switching thresholds
- Designed for voltage monitoring in single-phase networks
- Measuring range 160...276 V
- Relay has one or two changeover contacts
Application - ideal for residential and commercial applications, such as protecting power supplies, air conditioners, refrigerators or office equipment from harmful voltage fluctuations in the network
Single-phase supervisory relay with adjustable switching thresholds
- RPN-.VC.-A400 – voltage monitoring relay with fixed switching thresholds
- Relay for control of phase-to-phase voltages in three-phase networks (400 V AC)
- Protects the system against phase-to-phase voltage drops below Umin or increases above Umax
- Adjustable tripping delays
- Version with one or two changeover contacts (depending on configuration)
Application - it is used in power supply systems for high-power devices that are particularly sensitive to changes in phase-to-phase voltage - such as three-phase motors, HVAC systems, industrial pumps.
Three-phase supervisory relay with fixed switching thresholds
Why use voltage monitoring relays?
The use of voltage monitoring relays is one of the most effective ways to protect electrical installations and equipment from adverse phenomena occurring in the power supply network. These devices allow continuous voltage monitoring and instant reaction in case of:
- exceeding of the set voltage thresholds (Umin/Umax)
- occurrence of voltage asymmetry between phases
- loss of one or more phases
- incorrect phase sequence (for three-phase applications)
By automatically disconnecting the power supply when deviations from the established parameters are detected, these relays effectively eliminate the risk of damage to consumers, failure of controllers, interference with automation systems and potentially costly production downtime. In addition, their use extends the life of the entire power system, which translates into lower operating costs and greater plant reliability in the long term.
Now you know the types and differences of our minimum and maximum voltage monitoring relays. If you want to use them in your electrical installation, use the offer of our company - Relpol (https://www.relpol.pl/) - feel free to contact us.
