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

  • 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. 819-3248
Mfr. Part No.K8AK-LS1 24VAC/DC
BrandOmron
£50.95
Each
Units
Level Control 24 V ac/dc SPDT - - - - - - - - - - -
RS Stock No. 146-070
Mfr. Part No.RM35S0MW
£143.00
Each
Units
Speed 24 → 240 V ac/dc SPDT - - - - - - - 0.6 → 60 s - - -
RS Stock No. 715-7986
Mfr. Part No.2900177
£171.93
Each
Units
Current, Temperature, Voltage 110 → 500 V ac DPDT Overvoltage, Undervoltage 1, 3 0 → 480 V ac Overcurrent, Undercurrent 0.15A 12A - 0.1 → 50 s Overtemperature, Undertemperature - -
RS Stock No. 240-8967
Mfr. Part No.BD9080.12 3AC400V UH=AC230V
BrandDold
£243.38
Each
Units
Phase, Voltage 400 V ac DPDT Overvoltage, Undervoltage 3 - - - - Phase Asymmetry, Phase Failure, Phase Sequence 0.1 → 5 s - - -
RS Stock No. 500-3515
Mfr. Part No.MK9163N.12/110 ATEX AC/DC24V
BrandDold
£63.37
Each
Units
Temperature 24 V ac/dc DPDT - - - - - - - - Overtemperature - -
RS Stock No. 794-3963
Mfr. Part No.MLD4BS
BrandGIC
£44.57
Each
Units
Thermistor 400 V ac SPDT - 3 - - - 5A - 2 ms, 100 ms, 360 → 550 ms - - -
RS Stock No. 463-3654
Mfr. Part No.84871034
BrandCrouzet
£117.30
Each
Units
Current 230 V ac SPDT - 1 - Overcurrent, Undercurrent 0.1mA 10A - 0.1 → 3 s - - -
RS Stock No. 442-9411
Mfr. Part No.1SVR550824R9100
BrandABB
£66.11
Each
Units
Phase 208 → 440 V ac SPDT - 3 - - - - Phase Failure, Phase Sequence 500 ms - - -
RS Stock No. 298-9400
Mfr. Part No.45050 230VAC
£71.53
Each
Units
Voltage 230 V ac SPDT Overvoltage 1 0.5 → 10 V ac/dc, 3 → 60 V ac/dc, 30 → 600 V ac/dc - - - - 0.1 → 3 s - - -
RS Stock No. 819-3208
Mfr. Part No.K8AK-AS2 100-240VAC
BrandOmron
£82.15
Each
Units
Current 100 → 240 V ac SPDT - 1 - Overcurrent, Undercurrent 0.1 8A - - - - -
RS Stock No. 397-9195
Mfr. Part No.45PUVR 400VAC
£69.22
Each
Units
Phase, Voltage 400 V ac DPDT Undervoltage 3 Maximum of 400 V ac - - - Phase Loss 200 ms - - -
RS Stock No. 876-2551
Mfr. Part No.1SVR560730R3402
BrandABB
£605.60
Each
Units
Frequency, Voltage 24 → 240 V ac/dc SPDT Overvoltage, Undervoltage 1, 3 0 → 317 (2 Wire) V ac, 0 → 317 (4 Wire) V ac, 0 → 550 (3 Wire) V ac - - - - ±20 ms - - 40 → 70 Hz
RS Stock No. 758-6946
Mfr. Part No.3UG4633-1AL30
BrandSiemens
£105.39
Each
Units
Voltage 17 → 275 V ac/dc SPDT Overvoltage, Undervoltage - 17 → 275 V ac/dc - - - - 0.1 → 20 s - - -
RS Stock No. 442-9449
Mfr. Part No.1SVR550871R9500
BrandABB
£61.69
Each
Units
Phase, Voltage 320 → 460 V ac SPST Overvoltage, Undervoltage 1, 3 320 → 460 V ac - - - Phase Failure 500 ms - - -
RS Stock No. 758-6942
Mfr. Part No.3UG4632-1AW30
BrandSiemens
£110.02
Each
Units
Voltage 24 → 240 V ac/dc SPDT Overvoltage, Undervoltage - 10 → 600 V ac/dc - - - - 0.1 → 20 s - - -
RS Stock No. 321-6848
Mfr. Part No.45175 110VAC
£63.46
Each
Units
Speed 110 V ac SPDT - - - - - - - 0.5 → 30 min, 0.5 → 30 s - - -
RS Stock No. 775-7955
Mfr. Part No.1SVR730830R0400
BrandABB
£165.54
Each
Units
Voltage 24 → 240 V ac/dc DPDT Overvoltage, Undervoltage 1 3 → 30 V, 30 → 300 V, 6 → 60 V, 60 → 600 V - - - - 0 s, 0.1 → 30 s - - -
RS Stock No. 463-3402
Mfr. Part No.84871030
BrandCrouzet
£117.79
Each
Units
Current 24 V dc SPDT - 1 - Overcurrent, Undercurrent 0.1A 10A - 0.1 → 3 s - - -
RS Stock No. 776-1581
Mfr. Part No.72.01.8.240.0000
BrandFinder
£63.64
Each
Units
Level 230 → 240 V ac SPDT - 1 - - - - - 0.5 → 7 s - - -
RS Stock No. 850-5395
Mfr. Part No.LXCVR 230V
£47.04
Each
Units
Phase, Voltage 230 V ac SPDT Overvoltage, Undervoltage - 173 → 218 (Under) V, 242 → 288 (Over) V - - - Single Phase 0.2 → 10 s - - -
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