Siemens Reyrolle 7SR57 Motor Protection Relay

Siemens Reyrolle 7SR57 Motor Protection Relay Suppliers,Exporters in India

ARP IMPEX supplies and exports Siemens Reyrolle 7SR57 Motor Protection Relays for medium- and large-motor protection panels, industrial substations, motor control centres and plant electrical systems. Buyers can send the complete Siemens article number, protection specification and destination country for price and availability.

The Siemens Reyrolle 7SR57 is a numerical protection relay designed to protect motors during starting, normal running, overload and abnormal operating conditions. It monitors motor current, starting time, thermal condition, phase balance and other electrical values that can indicate a developing fault.

The relay covers protection against locked rotor, prolonged starting, thermal overload, phase imbalance, phase reversal, undercurrent, short circuit and earth fault. Selected versions also provide voltage, power, frequency and directional protection. The advanced 7SR5721 models include motor differential protection for large and critical motors.

Its thermal model follows the heating and cooling behaviour of the motor more closely than a basic overload element. Temperature sensor inputs are available on selected configurations for direct monitoring of motor windings, bearings or other plant locations. Depending on the model, the relay can accept up to 16 temperature sensor inputs.

IEC 61850 Ethernet communication comes as standard across the 7SR57 platform. The range also supports other commonly used industrial and substation communication protocols, allowing the relay to connect with SCADA, distributed control and substation automation systems.

ARP IMPEX can quote the Siemens Reyrolle 7SR57 motor protection relay price against the exact current inputs, voltage inputs, binary I/O, communication ports and protection functions required by the project.

Technical Specifications

• Brand: Siemens
• Product family: Reyrolle 5
• Series: 7SR57
• Product type: Numerical motor protection relay
• Main application: Protection, control and monitoring of industrial motors
• Available device types: 7SR5710, 7SR5711 and 7SR5721
• Current inputs: Four or eight, depending on the model
• CT secondary rating: Combined 1 A and 5 A current inputs
• Voltage inputs: Without voltage inputs or with four voltage inputs
• Binary inputs: Up to 29, depending on the configuration
• Binary outputs: Up to 16, including the device-health contact, depending on the ordering version
• Temperature sensor inputs: Zero, eight or sixteen
• Arc-flash detector inputs: Zero or three
• High-speed binary outputs: Up to three
• Heavy-duty binary outputs: Up to four
• Motor differential protection: Available on 7SR5721 models
• Housing sizes: Size 6, Size 8 or Size 12
• Construction: Withdrawable relay element
• Display: Backlit 128 × 128 graphical LCD
• Indication: Up to 28 programmable tri-colour LEDs
• Front communication: USB port
• Rear communication: RS485 and dual Ethernet ports
• Ethernet options: Electrical RJ45 or optional optical connections
• Communication protocols: IEC 61850, IEC 60870-5-103, Modbus RTU, Modbus TCP, DNP3 and DNP3 TCP
• Network redundancy: HSR, PRP and RSTP
• Rated auxiliary supply: 24–250 V DC or 100–230 V AC
• Configuration software: Siemens Reydisp Manager 2
• Security: Password control, signed firmware, security logging and role-based access control
• Optional construction: Conformal coating available against selected ordering codes

The hardware arrangement differs across the 7SR57 family. The full Siemens MLFB or article number must be checked before confirming the number of current inputs, voltage inputs, binary contacts or communication interfaces.

Main Motor Protection Functions

Thermal Overload Protection

The 7SR57 continuously calculates the motor’s thermal condition during starting, running and cooling. It can trip the motor before the calculated temperature reaches a damaging level.

This is important for motors that operate with frequent starts, changing loads or long acceleration times. The thermal model provides a better picture of motor heating than a simple current threshold alone.

Locked-Rotor and Starting-Time Protection

A motor that fails to accelerate can draw high current for longer than the winding and rotor can safely withstand. The relay monitors the starting sequence and can trip if the motor remains locked or takes too long to reach running condition.

The relay also records motor-start information, which can help maintenance engineers identify increasing starting time, excessive starting current or changes in the driven load.

Phase-Imbalance and Phase-Reversal Protection

Uneven phase current can cause additional heating in a motor even when the current in one or more phases appears normal. The 7SR57 monitors phase imbalance and can disconnect the motor before the condition causes winding damage.

Phase-rotation reversal protection can identify an incorrect phase sequence that may cause a pump, fan, conveyor or other machine to rotate in the wrong direction.

Undercurrent and Loss-of-Load Protection

A drop in motor current can indicate loss of mechanical load, pump dry running, broken belts, damaged couplings or process interruption.

Undercurrent protection allows the 7SR57 to detect these conditions without requiring a separate mechanical load sensor in suitable applications.

Overcurrent and Earth-Fault Protection

The relay provides instantaneous and time-delayed phase overcurrent protection for short-circuit and high-current fault conditions.

Measured and calculated earth-fault protection elements are available for detecting insulation failures and faults between the motor circuit and earth. High-impedance restricted earth-fault protection is also available for applicable schemes.

Temperature Sensor Monitoring

Selected 7SR57 configurations can monitor temperatures directly through plant temperature sensors. Depending on the selected model, the relay can accept eight or sixteen sensor inputs.

These inputs may be used for:

• Motor winding temperature
• Drive-end bearing temperature
• Non-drive-end bearing temperature
• Cooling-air temperature
• Motor enclosure temperature
• Other project-specific plant measurements

An external temperature interface can also be used where the required sensor inputs are not built into the relay.

Motor Differential Protection

The Siemens Reyrolle 7SR5721 provides motor differential protection for large and critical motors. It compares the current entering and leaving the protected motor zone and can trip quickly when it detects an internal phase or earth fault.

Motor differential protection is commonly considered for high-value motors where faster and more selective internal fault detection is required. The 7SR5721 uses eight current inputs and four voltage inputs in the standard motor differential arrangement.

Additional Functions with Voltage Inputs

The Siemens 7SR5711 and 7SR5721 models include voltage inputs and can provide additional protection and monitoring duties, such as:

• Undervoltage protection
• Overvoltage protection
• Sequence overvoltage protection
• Neutral-voltage displacement
• Power protection
• Power-factor monitoring
• Frequency protection
• Directional overcurrent protection
• Directional earth-fault protection
• VT supervision
• Voltage-referenced backspin monitoring

These versions are suitable where the relay must check the motor supply voltage as well as the motor current and thermal condition.

Backspin Monitoring

Some pumps, compressors and rotating machines can continue moving or rotate backwards after shutdown. Restarting the motor before the shaft has stopped can cause excessive mechanical and electrical stress.

The 7SR57 provides backspin monitoring to block a restart until the motor has reached a safe condition. Current-referenced and voltage-referenced arrangements are available depending on the selected device type.

Features

• Protects motors throughout starting, running and cooling periods
• The thermal model follows the motor heating and cooling characteristics
• Locked-rotor protection detects a motor that fails to accelerate
• Starting-time supervision identifies prolonged motor starts
• Phase-imbalance monitoring helps prevent uneven winding heating
• Phase-reversal protection identifies an incorrect supply sequence
• Undercurrent protection can detect dry running or loss of mechanical load
• Instantaneous and delayed overcurrent protection covers high-current faults
• Earth-fault protection helps detect insulation breakdown
• Temperature sensor inputs are available for winding and bearing monitoring
• Motor differential protection is available for large motors
• Backspin monitoring helps prevent unsafe motor restarting
• Number-of-starts supervision controls frequent start attempts
• Circuit-breaker failure protection is included
• Trip-circuit and closing-circuit supervision are available
• Arc-flash detector inputs are available on selected models
• IEC 61850 communication supports digital substation integration
• HSR, PRP and RSTP options support redundant Ethernet networks
• Motor-start, fault, event and waveform records assist fault analysis
• A large graphical display shows measurements, alarms and motor status
• Programmable LEDs provide clear local trip and warning indication
• Withdrawable construction makes testing and replacement easier
• Combined 1 A and 5 A CT inputs reduce hardware variations
• Conformal-coated versions are available for specified environments
• Role-based access and security logging help control changes to relay settings

The exact functions available depend on whether the selected device is a 7SR5710, 7SR5711 or 7SR5721.

Applications

Siemens Reyrolle 7SR57 Motor Protection Relays are commonly used for:

• Medium-voltage induction motors
• Large and critical industrial motors
• High-voltage motor protection panels
• Pump motors and pumping stations
• Compressor motors
• Industrial fans and blowers
• Crusher and mill motors
• Conveyor and material-handling motors
• Boiler feed pumps
• Cooling-water pumps
• Process pumps
• Refinery and petrochemical motors
• Oil and gas processing equipment
• Steel and rolling mill motors
• Cement plant machinery
• Mining and mineral-processing equipment
• Water and wastewater treatment plants
• Power-generation auxiliary motors
• Marine and port equipment
• Large HVAC and refrigeration compressors
• Motor control centre upgrades
• Protection-panel replacement projects
• Motors requiring differential protection
• Motors with winding and bearing temperature monitoring

The relay is particularly suitable where a project requires a numerical motor protection relay with IEC 61850, a large-motor differential protection relay, or an integrated motor protection device with thermal, electrical and temperature monitoring.

Available Siemens Reyrolle 7SR57 Models

Siemens Reyrolle 7SR5710 Motor Protection Relay

The 7SR5710 uses four current inputs and does not include voltage inputs. It covers the main current-based motor protection duties, including thermal overload, locked rotor, starting-time supervision, phase imbalance, overcurrent, earth fault and backspin monitoring.

It suits applications where voltage, power and directional elements are not required.

Siemens Reyrolle 7SR5711 Motor Protection Relay

The 7SR5711 uses four current inputs and four voltage inputs. It adds voltage, frequency, power, power-factor and directional protection functions to the standard motor protection package.
Selected configurations can also include arc-flash detector inputs, temperature sensor inputs, high-speed outputs or heavy-duty outputs.

Siemens Reyrolle 7SR5721 Motor Differential Protection Relay

The 7SR5721 uses eight current inputs and four voltage inputs. It provides motor differential protection in addition to the standard thermal, starting, overcurrent, earth-fault, voltage and monitoring functions.

This model is generally considered for large or high-value motors where internal winding faults must be cleared quickly and selectively.

Selecting the Correct Siemens 7SR57 Relay

The Reyrolle 7SR57 should not be selected only by the series name or motor kilowatt rating. The relay hardware and protection package must match the motor, starter, CT arrangement and plant communication system.

For correct selection, provide:

• Complete Siemens MLFB or article number
• Motor power rating
• Rated motor voltage
• Full-load current
• Starting current and starting time
• Motor thermal withstand information
• Direct-on-line, reactor, autotransformer or other starting method
• Number and ratios of protection CTs
• CT secondary rating
• VT ratio and voltage-input requirement
• Motor differential protection requirement
• Winding and bearing temperature sensor requirement
• Number of binary inputs and outputs
• Circuit-breaker or contactor control arrangement
• Backspin monitoring requirement
• Arc-flash detector requirement
• Auxiliary supply voltage
• IEC 61850 or other communication protocol
• Electrical or optical Ethernet requirement
• Housing size and panel cut-out
• Conformal coating requirement
• Quantity and destination country
• For replacement enquiries, share a clear photograph of the relay nameplate, the full article number, the existing wiring diagram and setting file where available.

Siemens Reyrolle 7SR57 Supplier and Exporter in India

ARP IMPEX is an independent supplier and exporter of Siemens Reyrolle protection relays in India. We supply 7SR57 Motor Protection Relays for industrial plants, EPC contractors, switchgear manufacturers, motor protection panel builders and maintenance companies.

Buyers searching for a Siemens Reyrolle 7SR57 motor protection relay supplier in India, an industrial motor protection relay exporter, or a motor differential protection relay with IEC 61850 communication can send the exact article number and project specification for review.

The 7SR57 range has several hardware and I/O combinations. A quotation should therefore be based on the complete ordering code rather than only the description “Siemens 7SR57 relay.