2 INTRODUCTION
2.1 Features
The P253 is a dedicated motor protection relay designed to protect motors in industrial networks and
power plants. It offers essential protection functions for motors deployed in installations from LV to MV
voltage levels. The P253 relay performs an important role in many industrial processes with its
diagnostic features improving asset health monitoring.
The principal protection functions in the relay include thermal overload, negative sequence
overcurrent, loss of load, prolonged start, locked rotor (starting/normal running), restricted earth fault,
excessive no. of starts and speed switch input for stall rotor detection. Additional versatility is provided
thanks to the inclusion of backup overcurrent and earth fault protection, with up to 3 independent
stages (IEC and IEEE curve types are provided for IDMT function), breaker fail and trip circuit
supervision functions. Multiple setting groups are included. The hardware capability is broadened by a
sensitive earth fault CT option, and a universal auxiliary power supply range to permit standardisation
in procurement and inventories.
The user can assign any of the logical/physical statuses to binary inputs, binary outputs and
programmable LEDs. This provides flexibility to program the relay as per the application requirements.
All the output contacts are changeover type for ease of implementing the desired wiring schematic.
The P253 offers supervision functions including measurement, monitoring and recording. The P253
records the starting current which is very helpful in monitoring motor performance during the critical
starting period. Industry and utility protocols such as MODBUS, IEC 60870-5-103 and DNP3.0 are
available for transmitting relay data to a supervisory control system via communication networks. The
intuitive operator interface facilitates easy reading of measured values and simple configuration of the
relay.
2.1.1 Protection & Control
• Thermal overload
• Speed switch input (for stall rotor detection)
• Prolonged start (excessive long start)
• Locked rotor (during starting)
• Locked rotor (during normal running)
• Excessive number of starts
• Loss of load detection
• Negative sequence overcurrent
• Emergency restart
• Timed and instantaneous phase and earth fault protection (3 independent stages)
• Wide range of IEC/IEEE curves
• Inrush blocking
• Circuit breaker Fail
• Restricted earth Fault
• Trip circuit supervision
• 6 Digital inputs
• 6 Digital output (c/o)
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