Selecting protection and monitoring relays
Start with the electrical quantity to be monitored to find the appropriate relay group.
Go to related Bender models ↓First identify the function required
‘Protection relay’ describes a broad product group. Voltage, current, frequency, phase sequence and loop resistance are different monitoring functions. Product selection starts by identifying the quantity to be monitored and how the alarm will be used.
Voltage and frequency monitoring
Bender LINETRAXX® VME and VMD products offer model-dependent under/overvoltage and frequency monitoring. Assess single- or three-phase circuit configuration, nominal voltage and auxiliary supply requirements together. Phase failure, phase sequence and asymmetry capabilities are not identical across all models.
Current monitoring
Current relays such as CME420 are assessed for undercurrent and overcurrent monitoring. Direct or current-transformer measurement, measuring range and transformation ratio form part of product selection. Residual current monitoring is a different measurement requirement and must not be confused with load current measurement.
PE loop and connection monitoring
GM420 is a relay for monitoring loop resistance or the PE conductor connection. This product group performs a different function from general voltage or current monitoring. The measuring circuit and operating conditions must be verified using manufacturer documents.
Does a monitoring relay disconnect the system directly?
A relay's monitoring, alarm and output functions depend on its technical specifications. A relay output alone does not provide every protective function in every application. Its use and the required protection arrangement must be assessed against the system's design requirements.
Information needed for quotations and product selection
Specify the measured quantity, distribution system type, voltage or current range, auxiliary supply and required relay outputs. As Bender's distributor in Türkiye, ADEO Teknik provides access to suitable models' technical information and current documents. Final selection must use the thresholds, delays and operating limits in the manufacturer's datasheet.
Bender relays by monitored quantity
Relay selection begins by identifying the quantity to monitor: voltage and frequency, load current and PE loop monitoring are different product functions.
LINETRAXX® VME420
Monitors undervoltage and overvoltage in AC/DC systems and frequency in AC supplies. Adjustable delays allow brief changes and persistent conditions to be assessed for the application.
Monitored system voltage and the separate auxiliary supply range are different parameters; select the suitable variant accordingly.Explore the model and documents
LINETRAXX® CME420
Used to monitor load current in AC circuits. Within the device's limits, measurement can be direct or via a suitable x/5 A current transformer.
Load current measurement differs from residual current measurement, where all live conductors pass through a shared loop.Explore the model and documents
LINETRAXX® GM420
Monitors the PE conductor loop in AC systems, helping detect interruptions in protective conductor connections. Displays loop resistance and extraneous voltage information.
Do not confuse PE loop monitoring with IMD insulation resistance or RCM residual current measurement; assess the application wiring against product documents.Explore the model and documentsCompare supply, measuring range, delay and contact function for the selected application. Product images belong to Bender.
Bender sources for these models
Technical source: Official Bender product information ↗