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ABB Feeder Protection REF615 ANSI
The REF615 is powerful, most advanced and simplest feeder protection relay in its class, perfectly offering time and instantaneous overcurrent, negative sequence overcurrent, phase discontinuity, breaker failure and thermal overload protection. The relay also features optional high impedance fault (HIZ) and sensitive earth fault (SEF) protection for grounded and ungrounded distribution systems. Also, the relay incorporates a flexible three-phase multi-shot auto-reclose function for automatic feeder restoration in temporary faults on overhead lines. Enhanced with safety options, the relay offers a three-channel arc-fault detection system for supervision of the switchgear circuit breaker, cable and busbar compartments.
The REF615 also integrates basic control functionality, which facilitates the control of one circuit breaker via the relay’s front panel human machine interface (HMI) or remote control system. To protect the relay from unauthorized access and to maintain the integrity of information, the relay has been provided with a four-level, role-based user authentication system, with individual passwords for the viewer, operator, engineer and administrator level. The access control system applies to the front panel HMI, embedded web browser based HMI and the PCM600 relay setting and configuration tool.
Standardized communication
REF615 supports the new IEC 61850 standard for inter-device communication in substations. The relay also supports the industry standard DNP3.0 and Modbus® protocols.
The implementation of the IEC 61850 substation communication standard in REF615 encompasses both vertical and horizontal communication, including GOOSE messaging and parameter setting according to IEC 61850-8-1. The substation configuration language enables the use of engineering tools for automated configuration, commissioning and maintenance of substation devices.
Bus protection via GOOSE
The REF615 IEC 61850 implementation includes GOOSE messaging for fast horizontal relay-to-relay communication. Applying GOOSE communication to the REF615 relays of the incoming and outgoing feeders of a substation, a stable, reliable and high-speed bus protection system can be realized. The cost-effective GOOSE-based bus protection is obtained just by configuring the relays and the operational availability of the protection is assured by continuous supervision of the protection relays and their GOOSE messaging over the station communication network.
Costs are reduced since no separate physical input and output hard-wiring is needed for horizontal communication between the relays.

Bus protection via GOOSE
Pre-emptive condition monitoring
For continuous knowledge of the operational availability of the REF615 features, a comprehensive set of monitoring functions to supervise the relay health, the trip circuit and the circuit breaker health is included. The breaker monitoring can include checking the wear and tear of the circuit breaker, the spring charging time of the breaker operating mechanism and the gas pressure of the breaker chambers. The relay also monitors the breaker travel time and the number of circuit breaker (CB) operations to provide basic information for scheduling CB maintenance.
Rapid set-up and commissioning
Due to the ready-made adaptation of REF615 for the protection of feeders, the relay can be rapidly set up and commissioned, once it has been given the application- specific relay settings. If the relay needs to be adapted to the special requirements of the intended application, the flexibility of the relay allows the relay’s standard signal configuration to be adjusted by means of the signal matrix tool (SMT) included in its PCM600 relay setting and configuration user tool.
By means of Connectivity Packages containing complete descriptions of ABB’s protection relays, with data signals, parameters and addresses, the relays can be automatically configured via PCM600 relay setting and configuration user tool, COM600 Station Automation series devices, or MicroSCADA Pro substation automation system.
Unique draw-out design relay
The draw-out type relay design speeds up installation and testing of the protection. The factory-tested relay units can be withdrawn from the relay cases during factory and commissioning tests. The relay case provides automatic short-circuiting of the CT secondary circuits to prevent hazardous voltages from arising in the CT circuits when a relay plug-in unit is withdrawn from its case.
The pull-out handle locking the relay unit into its case can be sealed to prevent the unit from being unintentionally withdrawn from the relay case.
REF615 highlights
- Comprehensive overcurrent protection with high impedance fault, sensitive earth fault and thermal overload protection for feeder and dedicated protection schemes
- Simultaneous DN3.0 Level 2+ and Modbus Ethernet communications plus device connectivity and system interoperability according to the IEC 61850 standard for next generation substation communication
- Enhanced digital fault recorder functionality including high sampling frequency, extended length of records, 4 analog and 64 binary channels and flexible triggering possibilities
- High-speed, three-channel arc flash detection (AFD) for increased personal safety, reduced material damage and minimized system down-time
- Total control of the operational capability of the protection system through extensive condition monitoring of the relay and the associated primary equipment
- Draw-out type relay unit and a unique relay case design for a variety of mounting methods and fast installation, routine testing and maintenance
- One single tool for managing relay settings, signal configuration and disturbance handling
Analog inputs
- Three phase currents: 5/1 A
- Ground current: 5/1 A or 0.2 A
- Rated frequency: 60/50 Hz programmable
Binary inputs and outputs
- Four binary inputs with common ground
- Two NO double-pole outputs with TCM
- Two NO single-pole outputs
- One Form C signal output
- One Form C self-check alarm output
- Additional seven binary inputs plus three binary outputs (available as an option)
Communication
- IEC 61850-8-1 with GOOSE messaging
- DNP3.0 Level 2+ over TCP/IP
- Modbus over TCP/IP
- Time synchronization via SNTP (primary and backup servers)
- Optional serial RS-485 port programmable for DNP3.0 Level 2+ or Modbus RTU
Control voltage
- Option 1: 48 … 250 V dc, 100 … 240 V ac
- Option 2: 24 … 60 V dc
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SOURCE: ABB
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ANSI Functions For Protection Devices
In the design of electrical power systems, the ANSI Standard Device Numbers denote what features a protective device supports (such as a relay or circuit breaker). These types of devices protect electrical systems and components from damage when an unwanted event occurs, such as an electrical fault.
ANSI numbers are used to identify the functions of meduim voltage microprocessor devices.
ANSI facilitates the development of American National Standards (ANS) by accrediting the procedures of standards developing organizations (SDOs). These groups work cooperatively to develop voluntary national consensus standards. Accreditation by ANSI signifies that the procedures used by the standards body in connection with the development of American National Standards meet the Institute’s essential requirements for openness, balance, consensus and due process.
Current protection functions
ANSI 50/51 – Phase overcurrent
Three-phase protection against overloads and phase-to-phase short-circuits.
ANSI index ↑
ANSI 50N/51N or 50G/51G – Earth fault
Earth fault protection based on measured or calculated residual current values:
- ANSI 50N/51N: residual current calculated or measured by 3 phase current sensors
- ANSI 50G/51G: residual current measured directly by a specific sensor
ANSI 50BF – Breaker failure
If a breaker fails to be triggered by a tripping order, as detected by the non-extinction of the fault current, this backup protection sends a tripping order to the upstream or adjacent breakers.
ANSI index ↑
ANSI 46 – Negative sequence / unbalance
Protection against phase unbalance, detected by the measurement of negative sequence current:
- sensitive protection to detect 2-phase faults at the ends of long lines
- protection of equipment against temperature build-up, caused by an unbalanced power supply, phase inversion or loss of phase, and against phase current unbalance
ANSI 49RMS – Thermal overload
Protection against thermal damage caused by overloads on machines (transformers, motors or generators).
The thermal capacity used is calculated according to a mathematical model which takes into account:
- current RMS values
- ambient temperature
- negative sequence current, a cause of motor rotor temperature rise
Recloser
ANSI 79
Automation device used to limit down time after tripping due to transient or semipermanent faults on overhead lines. The recloser orders automatic reclosing of the breaking device after the time delay required to restore the insulation has elapsed. Recloser operation is easy to adapt for different operating modes by parameter setting.
ANSI index ↑
Directional current protection
ANSI 67N/67NC type 1
ANSI 67 – Directional phase overcurrent
Phase-to-phase short-circuit protection, with selective tripping according to fault current direction. It comprises a phase overcurrent function associated with direction detection, and picks up if the phase overcurrent function in the chosen direction (line or busbar) is activated for at least one of the 3 phases.
ANSI index ↑
ANSI 67N/67NC – Directional earth fault
Earth fault protection, with selective tripping according to fault current direction.
3 types of operation:
- type 1: the protection function uses the projection of the I0 vector
- type 2: the protection function uses the I0 vector magnitude with half-plane tripping zone
- type 3: the protection function uses the I0 vector magnitude with angular sector tripping zone
ANSI 67N/67NC type 1
Directional earth fault protection for impedant, isolated or compensated neutralsystems, based on the projection of measured residual current.
ANSI index ↑
ANSI 67N/67NC type 2
Directional overcurrent protection for impedance and solidly earthed systems, based on measured or calculated residual current. It comprises an earth fault function associated with direction detection, and picks up if the earth fault function in the chosen direction (line or busbar) is activated.
ANSI index ↑
ANSI 67N/67NC type 3
Directional overcurrent protection for distribution networks in which the neutral earthing system varies according to the operating mode, based on measured residual current. It comprises an earth fault function associated with direction detection (angular sector tripping zone defined by 2 adjustable angles), and picks up if the earth fault function in the chosen direction (line or busbar) is activated.
ANSI index ↑
Directional power protection functions
ANSI 32P – Directional active overpower
Two-way protection based on calculated active power, for the following applications:
- active overpower protection to detect overloads and allow load shedding
- reverse active power protection:
- against generators running like motors when the generators consume active power
- against motors running like generators when the motors supply active power
ANSI 32Q/40 – Directional reactive overpower
Two-way protection based on calculated reactive power to detect field loss on synchronous machines:
- reactive overpower protection for motors which consume more reactive power with field loss
- reverse reactive overpower protection for generators which consume reactive power with field loss.
Machine protection functions
ANSI 37 – Phase undercurrent
Protection of pumps against the consequences of a loss of priming by the detection of motor no-load operation.
It is sensitive to a minimum of current in phase 1, remains stable during breaker tripping and may be inhibited by a logic input.
ANSI index ↑
ANSI 48/51LR/14 – Locked rotor / excessive starting time
Protection of motors against overheating caused by:
- excessive motor starting time due to overloads (e.g. conveyor) or insufficient supply voltage.
The reacceleration of a motor that is not shut down, indicated by a logic input, may be considered as starting. - locked rotor due to motor load (e.g. crusher):
- in normal operation, after a normal start
- directly upon starting, before the detection of excessive starting time, with detection of locked rotor by a zero speed detector connected to a logic input, or by the underspeed function.
ANSI 66 – Starts per hour
Protection against motor overheating caused by:
- too frequent starts: motor energizing is inhibited when the maximum allowable number of starts is reached, after counting of:
- starts per hour (or adjustable period)
- consecutive motor hot or cold starts (reacceleration of a motor that is not shut down, indicated by a logic input, may be counted as a start)
- starts too close together in time: motor re-energizing after a shutdown is only allowed after an adjustable waiting time.
ANSI 50V/51V – Voltage-restrained overcurrent
Phase-to-phase short-circuit protection, for generators. The current tripping set point is voltage-adjusted in order to be sensitive to faults close to the generator which cause voltage drops and lowers the short-circuit current.
ANSI index ↑
ANSI 26/63 – Thermostat/Buchholz
Protection of transformers against temperature rise and internal faults via logic inputs linked to devices integrated in the transformer.
ANSI index ↑
ANSI 38/49T – Temperature monitoring
Protection that detects abnormal temperature build-up by measuring the temperature inside equipment fitted with sensors:
- transformer: protection of primary and secondary windings
- motor and generator: protection of stator windings and bearings.
Voltage protection functions
ANSI 27D – Positive sequence undervoltage
Protection of motors against faulty operation due to insufficient or unbalanced network voltage, and detection of reverse rotation direction.
ANSI index ↑
ANSI 27R – Remanent undervoltage
Protection used to check that remanent voltage sustained by rotating machines has been cleared before allowing the busbar supplying the machines to be re-energized, to avoid electrical and mechanical transients.
ANSI index ↑
ANSI 27 – Undervoltage
Protection of motors against voltage sags or detection of abnormally low network voltage to trigger automatic load shedding or source transfer.
Works with phase-to-phase voltage.
ANSI index ↑
ANSI 59 – Overvoltage
Detection of abnormally high network voltage or checking for sufficient voltage to enable source transfer. Works with phase-to-phase or phase-to-neutral voltage, each voltage being monitored separately.
ANSI index ↑
ANSI 59N – Neutral voltage displacement
Detection of insulation faults by measuring residual voltage in isolated neutral systems.
ANSI index ↑
ANSI 47 – Negative sequence overvoltage
Protection against phase unbalance resulting from phase inversion, unbalanced supply or distant fault, detected by the measurement of negative sequence voltage.
ANSI index ↑
Frequency protection functions
ANSI 81H – Overfrequency
Detection of abnormally high frequency compared to the rated frequency, to monitor power supply quality.
ANSI index ↑
ANSI 81L – Underfrequency
Detection of abnormally low frequency compared to the rated frequency, to monitor power supply quality. The protection may be used for overall tripping or load shedding. Protection stability is ensured in the event of the loss of the main source and presence of remanent voltage by a restraint in the event of a continuous decrease of the frequency, which is activated by parameter setting.
ANSI index ↑
ANSI 81R – Rate of change of frequency
Protection function used for fast disconnection of a generator or load shedding control. Based on the calculation of the frequency variation, it is insensitive to transient voltage disturbances and therefore more stable than a phase-shift protection function.
Disconnection
In installations with autonomous production means connected to a utility, the “rate of change of frequency” protection function is used to detect loss of the main system in view of opening the incoming circuit breaker to:
- protect the generators from a reconnection without checking synchronization
- avoid supplying loads outside the installation.
Load shedding
The “rate of change of frequency” protection function is used for load shedding in combination with the underfrequency protection to:
- either accelerate shedding in the event of a large overload
- or inhibit shedding following a sudden drop in frequency due to a problem that should not be solved by shedding.
Related book: Relay selection guide
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Autor: Edvard Csanyi, CsanyiGroup
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