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. 146-480
Mfr. Part No.RM35TF30
R 3,122.70
Each
units
Phase, Voltage 220 → 480 V ac DPDT Overvoltage, Undervoltage 3 194 → 528 V ac - - - Phase Asymmetry, Phase Failure, Phase Sequence 0.1 → 10 s - - -
RS stock no. 146-238
Mfr. Part No.RM17TG20
R 1,365.00
Each
units
Phase 208 440 V ac DPDT - 3 - - - - Phase Asymmetry, Phase Failure, Phase Sequence <100 ms - - -
RS stock no. 884-2473
Mfr. Part No.MAC04D0100
BrandGIC
R 664.71
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. 146-597
Mfr. Part No.RM17TU00
R 1,464.75
Each
units
Phase, Voltage 208 → 480 V ac SPDT Undervoltage 3 183 → 528 V ac - - - Phase Failure, Phase Sequence 0.1 → 10 s - - -
RS stock no. 146-496
Mfr. Part No.RM17TE00
R 2,406.60
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. 857-7662
Mfr. Part No.DPA51CM44
R 3,103.25
Each
units
Phase 208 → 480 V ac SPDT - 3 177 → 550 V ac - - - Phase Loss, Phase Sequence - - - -
RS stock no. 518-7297
Mfr. Part No.3UG4513-1BR20
BrandSiemens
R 1,570.00
Each
units
Phase, Voltage 160 → 690 V ac DPDT Undervoltage 3 160 → 690 V ac - - - Phase Failure, Phase Imbalance, Phase Sequence 0.1 → 20 s - - -
RS stock no. 397-9189
Mfr. Part No.70PCVR-4W 400VAC
R 2,203.95
Each
units
Phase, Voltage 400 V ac 4NO/4NC Overvoltage, Undervoltage 3 Maximum of 400 V ac - - - Neutral Loss, Phase Loss 200 ms - - -
RS stock no. 146-608
Mfr. Part No.RM17TT00
R 1,528.80
Each
units
Phase 208 → 480 V ac SPDT - 3 - - - - Phase Asymmetry, Phase Failure, Phase Sequence 0.1 → 10 s - - -
RS stock no. 145-976
Mfr. Part No.RM35JA32MW
R 3,015.60
Each
units
Current 24 → 240 V ac/dc DPDT - - - Overcurrent, Undercurrent 0.15A 15A - 0.3 → 30 s - - -
RS stock no. 857-7075
Mfr. Part No.DIA53S72420A
R 801.36
Each
units
Current - SPST - 1 - Overcurrent - - - <300 ms - - -
RS stock no. 299-1914
Mfr. Part No.45150 230VAC
R 1,527.86
Each
units
Current 230 V ac SPDT - 1 - Overcurrent 5mA 1A - 0.1 → 3 s - - -
RS stock no. 857-7179
Mfr. Part No.DUB01CB23500V
R 3,408.54
Each
units
Voltage 115/230 V ac SPDT Overvoltage, Undervoltage 1 2 → 500 V ac/dc - - - - 1 s, 6 s - - -
RS stock no. 146-591
Mfr. Part No.RM17TA00
R 2,010.75
Each
units
Phase 208 → 480 V ac SPDT - 3 - - - - Phase Asymmetry, Phase Failure, Phase Sequence 0.1 → 10 s - - -
RS stock no. 916-0198
Mfr. Part No.PMA50A415
BrandLovato
R 2,795.55
Each
units
Current 380 → 415 V ac SPDT - 1, 3 - Overcurrent, Undercurrent 0.1A 16A - 0.1 → 10 s - - -
RS stock no. 916-0132
Mfr. Part No.PMV55A240
BrandLovato
R 2,213.84
Each
units
Voltage 208 → 240 V ac SPDT Self Powered 1 Maximum of 400 V ac - - - - 0.1 → 20 s - - -
RS stock no. 347-696
Mfr. Part No.FSRST30SLP-110/230VAC
BrandTempatron
R 1,646.44
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. 614-9432
Mfr. Part No.84872141
BrandCrouzet
R 1,800.82
Each
units
Voltage 24 → 48 V ac/dc SPDT Overvoltage, Undervoltage 1 20 → 80 V ac/dc - - - - 0.1 → 10 s - - -
RS stock no. 916-0182
Mfr. Part No.PMA30240
BrandLovato
R 2,462.19
Each
units
Current 24 → 240 V ac/dc SPDT - 1 - Overcurrent 0.25A 16A - 0.1 → 30 s - - -
RS stock no. 914-3945
Mfr. Part No.ECPF03
BrandRelpol
R 337.59
Each
units
Phase, Voltage 220 → 460 V SPDT Overvoltage, Undervoltage 3 45 → 65 Hz, 176 → 552 V - - - Phase Failure, Phase Sequence - - - -