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. 102-6137
BrandRS PRO
MYR425.60
Each
units
Phase, Voltage 400 V ac SPDT Overvoltage, Undervoltage 3 300 → 380 (Undervoltage) V, 420 → 500 (Overvoltage) V - - - Phase Failure, Phase Sequence 0.2 → 10 s - - 48 → 63 Hz
RS Stock No. 102-6131
BrandRS PRO
MYR294.82
Each
units
Voltage 230 V ac SPDT Overvoltage, Undervoltage 1 173 → 218 (Undervoltage) V, 242 → 288 (Overvoltage) V - - - - 0.2 → 10 s - - 48 → 63 Hz
RS Stock No. 102-6136
BrandRS PRO
MYR286.23
Each
units
Phase, Voltage 280 → 520 V ac SPDT Undervoltage 3 300 → 500 (Undervoltage) V - - - Phase Failure, Phase Sequence 0.2 → 10 s - - 48 → 63 Hz
RS Stock No. 102-6134
BrandRS PRO
MYR446.92
Each
units
Current 24 → 230 V ac/dc SPDT - 1 - Overcurrent, Undercurrent 1A 10A - 0.1 → 30 s - - 48 → 63 Hz
RS Stock No. 102-6130
BrandRS PRO
MYR210.33
Each
units
Voltage 12 → 24 V dc SPDT Undervoltage 1 12 → 24 V dc - - - - 0 → 30 s - - -
RS Stock No. 102-6133
BrandRS PRO
MYR502.10
Each
units
Voltage 24 → 230 V ac/dc SPDT Overvoltage, Undervoltage 1 50 → 500 V - - - - 0.1 → 30 s - - 48 → 63 Hz
RS Stock No. 102-6135
BrandRS PRO
MYR280.39
Each
units
Phase, Voltage 280 → 520 V ac SPDT Undervoltage 3 Maximum of 280 V - - - Phase Failure, Phase Sequence 100 ms - - 48 → 63 Hz
RS Stock No. 772-1215
Mfr. Part No.5SV8000-6KK
BrandSiemens
MYR1,432.52
Each
units
Current 230 V ac - - - - Residual 30mA 5A - 0.02 → 5 s - - -
RS Stock No. 240-8939
Mfr. Part No.BA9043 3AC50-400Hz 230/400V
BrandDold
MYR980.08
Each
units
Voltage 230/400 V ac DPDT Undervoltage - - - - - - - - - -
RS Stock No. 727-1256
Mfr. Part No.PUA01CB23500V
MYR373.48
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. 261-993
Mfr. Part No.84874320
BrandCrouzet
MYR923.36
Each
units
Speed 24 → 240 V ac/dc SP-NO/NC - - - - - - - 15 ms - - -
RS Stock No. 857-7416
Mfr. Part No.PPA01CM44
MYR656.94
Each
units
Phase, Voltage 208 → 480 V ac SPDT - 3 177 → 475 V ac - - - Phase Loss, Phase Sequence - - - -
RS Stock No. 857-7662
Mfr. Part No.DPA51CM44
MYR949.62
Each
units
Phase 208 → 480 V ac SPDT - 3 177 → 550 V ac - - - Phase Loss, Phase Sequence - - - -
RS Stock No. 124-0184
Mfr. Part No.RM22TR33
MYR563.88
Each
units
Phase, Voltage 304 → 576 V ac DPDT Overvoltage, Undervoltage 3 380 → 480 V ac - - - Phase Failure, Phase Sequence 0.1 → 30 s - - -
RS Stock No. 614-9397
Mfr. Part No.84871130
BrandCrouzet
MYR649.38
Each
units
Current 24 → 240 V ac/dc DPDT - 3 - Overcurrent, Undercurrent 0.1A 10A - 0.1 → 3 s - - -
RS Stock No. 775-7936
Mfr. Part No.1SVR730824R9300
BrandABB
MYR479.69
Each
units
Phase 200 → 500 V ac DPDT - 3 - - - - Phase Failure, Phase Sequence 500 ms - - 45 → 65 Hz
RS Stock No. 884-2473
Mfr. Part No.MAC04D0100
BrandGIC
MYR207.57
Each
units
Phase, Voltage 415 V ac DPDT Overvoltage Protection, Undervoltage Protection 3 - - - - Neutral Loss, Phase Failure, Phase Reversal, Phase Sequence, Phase Symmetry 5 (Over Voltage) s, 5 (Phase Failure) s, 5 (Phase Imbalance) s, 5 (Under Voltage) s, 500 ms → 1 s (Neutral Loss) - - 47 → 53 Hz
RS Stock No. 614-9347
Mfr. Part No.84870700
BrandCrouzet
MYR513.28
Each
units
Level Control 24 → 240 V ac/dc DPDT - - 24 → 240 V ac - 10mA 5A - 0.1 → 5 s - - 50 → 60 Hz
RS Stock No. 347-696
Mfr. Part No.FSRST30SLP-110/230VAC
BrandTempatron
MYR455.15
Each
units
Shaft Rotation Sensor 110 V ac, 230 V ac SPDT - - Maximum of 30 V dc - - - - 1 → 30 s - - 50 → 60 Hz
RS Stock No. 392-7267
Mfr. Part No.3RN1010-1CB00
BrandSiemens
MYR378.60
Each
units
Thermistor motor protection relay 24 V ac/dc SPDT - - - - - - - - Overtemperature, Undertemperature +60 → +180°C -
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