Protector Trip Relays

Crompton Instruments manufactured extensive range of Protector Trip Relays (electronic control products)providing continuous monitoring and protection of any electrical parameter, including 400 Hz for the aviation industry. When the monitored parameter deviates from the desired set point limit, the relay will operate to prevent damage to the power asset. Designed to suit a wide variety of applications the range offers both traditional and technologically advanced products, from single parameter units through to multifunctional microprocessor based protection relays.

For the specific protection of generator sets, the range offers unbalanced current, reverse power flow, reverse VAr, synchro-check and under/over-speed trip relay functions. Various dc models provide protection of battery and UPS systems and a range of temperature protection products is ideal to prevent the damaging effects of overheating.

This versatile range features a host of DIN-rail protectors offering numerous trip functions for single and three-phase power systems, including (see pics below): Ac Current, Ac Voltage, Dc Millivolts, Earth Leakage, Frequency, Ground Fault, Hot Spot 3 Temperature, Hot Spot 6 Temperature, Phase Balance, Phase Sequence and Failure, Reverse Power, Speed Sensing, Synchro-Check(Paralleling), Thermistor Trip, Voltage & Frequency Combined Under/Over


  • Continuous monitoring of any electrical parameter
  • Monitoring for under and over current conditions
  • Ensures load current is within generator capacity
  • DIN-rail or wall mounted
  • Range of outputs and configurations
  • Adjustable trip points, time delay and differentials
  • LED trip indication
  • Designed to avoid nuisance tripping


  • Protection of power assets
  • Detection and isolation of faults
  • Maintains supply continuity of healthy circuits
  • High speed tripping to avoid damage


  • Switchgear
  • Aviation Industry (400 Hz Protectors)
  • Distribution systems
  • Generator sets
  • Control panels
  • Energy management
  • Building management
  • Utility power monitoring
  • Process control
  • Motor protection
  • Equipment and network protection


  • CSA File Number 052592 for following units
  • Ac Voltage, Types: 252-PV,253-PV, monitoring voltage, 300v max single phase and three phase
  • AC Current, Types: 252-PA, 253-PA, monitoring current, 5A max from CT secondary, 10 A max direct. Aux. voltage supply – 300V ac max, 24 V DC max, 4VA
  • Frequency, Types: 252-PH, 253-PH, monitoring frequency,400 Hz max, 300 v max
  • Reverse power, Type: 256-PA, monitoring voltage, 300 V ac max, monitoring current 10 A max
  • Phase Sequence-loss, Type: 252-PVR, monitoring voltage, 300 V max
  • Phase Balance, Type: 252-PS, monitoring voltage, 600 v ac max
  • Transducer Trip, Types: 252-PB, 253-PB, monitoring voltage 50 v DC, monitoring current 20 mA DC, Aux Voltage supply 240 v ac max, 3 VA
  • Temperature Trip, Types: 252-PBS, 253-PBT, monitoring voltage, 150 mv max. Aux voltage 240 v ac max, 3VA.
  • Synchro-Check, Type: 256-PLL, 256-PLD; monitoring voltage, phase displacement, and frequency of two supplies, operating voltage range 57.7-300v ac max, 45-65 Hz, 6VA with two output relay contacts rated 240 v ac, 5A (non-inductive) and 24 V DC/5A (resistive)