Monitoring Relays

Monitoring relays are a type of relay that trips a circuit breaker when a fault is detected. A relay is an electrically controlled switch that is used to turn the power on or off in a circuit.


Monitoring relays are more sophisticated than regular relays, as they have adjustable operating conditions, whereas normal relays switch according to a fixed threshold. They measure a given parameter, such as voltage or temperature, and will trip a circuit breaker when the parameter gets too high or low.


What are monitoring relays used for?


Monitoring relays have a wide range of uses, depending largely on the factor being monitored. For example, they can protect against overcurrent if measuring current, or they can detect an abnormally low frequency if frequency is being measured.


Types of monitoring relay


The main way in which monitoring relays differ is the function that they measure. This can be a number of things, including: voltage, current, temperature and frequency.


The factor that you need to measure will decide which monitoring relay you choose.


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Description Price Monitoring Application Supply Voltage Contact Configuration Voltage Sensitivity Electrical Phase Voltage Sensing Range Current Sensitivity Minimum Current Sensed Maximum Current Sensed Phase Sensitivity Time Delay Temperature Sensitivity Temperature Sensing Range Frequency Sensing Range
RS Stock No. 850-5411
Mfr. Part No.LBVR/A 12-24VDC
£49.06
Each
Units
Voltage 8 → 30 V dc SPDT Undervoltage - 12 → 24 V dc - - - - 0 → 30 s - - -
RS Stock No. 727-1256
Mfr. Part No.PUA01CB23500V
£70.25
Each
Units
Current, Voltage 115/230 V ac SPDT Overvoltage - 0.4 → 500 V ac, 2 → 500 V dc Overcurrent - - - <300 ms - - -
RS Stock No. 629-386
Mfr. Part No.M3PPI 300-500vAC
£39.21
Each
Units
Phase 300 → 500 V ac - - 3 - - - - Phase Loss, Phase Sequence - - - -
RS Stock No. 518-6086
Mfr. Part No.817-E2
£138.00
Each
Units
Temperature 24 → 240 V ac/dc DPST - - - - - - - - Overtemperature - -
RS Stock No. 794-3939
Mfr. Part No.MG53BH
BrandGIC
£41.36
Each
Units
Voltage 415 V ac DPDT Overvoltage, Undervoltage 3 - - - 5A - 5 s, 0 → 15 s - - -
RS Stock No. 850-5364
Mfr. Part No.LXPRC/S-4W 230V (400V)
£72.04
Each
Units
Phase, Voltage 230 V ac SPDT Overvoltage, Undervoltage - 173 → 218 (Under) V, 242 → 288 (Over) V - - - Phase Failure, Phase Sequence 0.2 → 10 s - - -
RS Stock No. 392-7289
Mfr. Part No.3RN1010-1CM00
BrandSiemens
£63.63
Each
Units
Thermistor motor protection relay 230 V ac SPDT - - - - - - - - Overtemperature, Undertemperature +60 → +180°C -
RS Stock No. 794-3948
Mfr. Part No.MG73BH
BrandGIC
£37.42
Each
Units
Voltage 240 V ac DPDT Overvoltage, Undervoltage 1, 3 - - - 5A - 5 s, 0 → 15 s - - -
RS Stock No. 261-959
Mfr. Part No.84871122
BrandCrouzet
£87.19
Each
Units
Current 24 → 240 V ac/dc SP-NO/NC - - - Overcurrent, Undercurrent 2A 20A - 500 ms - - -
RS Stock No. 146-200
Mfr. Part No.RM35JA31MW
£100.70
Each
Units
Current 24 → 240 V ac/dc DPDT - - - Overcurrent, Undercurrent 2mA 500mA - 0.3 → 30 s - - -
RS Stock No. 146-496
Mfr. Part No.RM17TE00
£145.35
Each
Units
Phase, Voltage 208 → 480 V ac SPDT Overvoltage, Undervoltage 3 183 → 528 V ac - - - Phase Asymmetry, Phase Failure, Phase Sequence 0.1 → 10 s - - -
RS Stock No. 146-250
Mfr. Part No.RM17TG00
£73.00
Each
Units
Phase 208 → 480 V ac SPDT - 3 - - - - Phase Asymmetry, Phase Failure, Phase Sequence <100 ms - - -
RS Stock No. 806-5910
Mfr. Part No.1SVR730660R0100
BrandABB
£242.69
Each
Units
Insulation 24 → 240 V ac/dc SPDT - - 0 → 250 V ac, 0 → 300 V dc - - - - - - - -
RS Stock No. 397-9218
Mfr. Part No.45PSR 400VAC
£79.43
Each
Units
Phase 400 V ac SPDT - 3 - - - - Phase Loss, Phase Sequence 200 ms - - -
RS Stock No. 124-0184
Mfr. Part No.RM22TR33
£103.55
Each
Units
Phase, Voltage 304 → 576 V ac DPDT Overvoltage, Undervoltage 3 380 → 480 V ac - - - Phase Failure, Phase Sequence 0.1 → 30 s - - 50 → 60 Hz
RS Stock No. 758-6924
Mfr. Part No.3UG4512-1AR20
BrandSiemens
£72.91
Each
Units
Phase 160 → 690 V ac SPDT - - 160 → 690 V ac - - - Phase Failure, Phase Sequence - - - -
RS Stock No. 518-7174
Mfr. Part No.3UG4615-1CR20
BrandSiemens
£140.51
Each
Units
Phase, Voltage 160 → 690 V ac DPDT Overvoltage, Undervoltage 3 160 → 690 V ac - - - Phase Failure, Phase Sequence 0.1 → 20 s - - -
RS Stock No. 857-7662
Mfr. Part No.DPA51CM44
£159.60
Each
Units
Phase 208 → 480 V ac SPDT - 3 177 → 550 V ac - - - Phase Loss, Phase Sequence - - - -
RS Stock No. 392-7267
Mfr. Part No.3RN1010-1CB00
BrandSiemens
£63.63
Each
Units
Thermistor motor protection relay 24 V ac/dc SPDT - - - - - - - - Overtemperature, Undertemperature +60 → +180°C -
RS Stock No. 614-9347
Mfr. Part No.84870700
BrandCrouzet
£66.93
Each
Units
Level Control 24 → 240 V ac/dc DPDT - - 24 → 240 V ac - 10mA 5A - 0.1 → 5 s - - 50 → 60 Hz
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