The Microshield O/C relay is an advanced microprocessor based unit that was designed to provide high value three phase and ground overcurrent protection and optional circuit breaker auto-reclosing. Applications include distribution feeders, transformers, line protection back-up, motor protection, and others. The Microshield O/C provides monitoring, metering, and fault recording as well as protection.

The Microshield O/C can be applied with voltage transformers (VTs) connected for operation at 69 or 120 volts AC phase-to-ground (Wye), 120 volts or 208 volts AC phase-tophase (Open-Delta). (Other voltages such as 110v or 100v nominal are also suitable and easily accomodated.)

The unit is packaged in a steel case suitable for conventional flush mounting on panel. It can also be semi-flush mounted by the use of available case spacers when unit depth is a concern. Available bezels make retrofit of older electromechanical and solid state relays possible. The full draw-out design allows for quick removal without the need for removal of hardware. The microprocessor based logic along with the power supply, VT’s and CT’s can be totally withdrawn from the case and interchanged with other cases without the need for re-calibration. CT shorting bars are an integral part of the unit case. All connections to the Microshield O/C are made at terminals on the rear of the unit.

Protective Functions
The Microshield O/C contains the protective elements necessary for medium voltage circuit overcurrent protection. Its applications include distribution feeder protection, line backup protection, motor overcurrent protection, and transformer overcurrent protection. The dual phase-timeovercurrent
elements allow the user to design a composite curve; for example for motor protection applications to provide locked-rotor and overload protection. A summary of the elements follows.

The combined overcurrent and earth-fault relay SPAJ 140 C is intended to be used for the selective short-circuit and earth-fault protection of radial feeders in solidly earthed, resistance earthed or impedance earthed power systems. The integrated protection relay includes an overcurrent unit and an earth-fault unit with flexible tripping and signalling facilities. The overcurrent and earth-fault relays can also be used for other applications requiring single-, two-, or three-phase overcurrent protection. The combined overcurrent and earth-fault relay includes a circuit-breaker failure protection unit.

The combined overcurrent and earth-fault relay SPAJ 140 C is part of ABB’s Distribution Automation concept, the complete ABB solution for control and management of electric power systems.

The combined overcurrent and earth-fault relay SPAJ 141 C is intended to be used for the selective short-circuit and earth-fault protection of radial feeders in solidly earthed, resistance earthed or impedance earthed power systems. The integrated protection relay includes an overcurrent unit and an earth-fault unit with flexible tripping and signalling facilities. The overcurrent and earth-fault relays can also be used for other applications requiring single-, two-, or three-phase overcurrent protection and earth-fault protection. The combined overcurrent and earth-fault relay includes a circuit-breaker failure protection unit.

The combined overcurrent and earth-fault relay SPAJ 141 C is part of ABB’s Distribution Automation concept extending ABB’s solution for the control and management of electric power systems.

The combined overcurrent and earth-fault relay SPAJ 142 C is intended to be used for the selective short-circuit and earth-fault protection of radial feeders in solidly earthed, resistance earthed or impedance earthed power systems. The integrated protection relay includes an overcurrent unit and an earth-fault unit with flexible tripping and signalling facilities. The overcurrent and earth-fault relays can also be used for other applications requiring single-, two-, or three-phase overcurrent protection and sensitive earth-fault protection. The combined overcurrent and earth-fault relay includes a circuit-breaker failure protection unit.

The combined overcurrent and earth-fault relay SPAJ 142 C is part of ABB’s Substation Automation concept extending ABB’s solution for the control and management of electric power systems.

The combined phase and neutral overcurrent relay SPAJ 144 C is used for the selective short-circuit and time overcurrent protection of radial feeders in distribution networks. The relay is also used for feeder earth-fault protection in isolated neutral networks and networks with resistively earthed neutral. The overcurrent unit includes three protection stages and the earth-fault unit two. Further, the relay includes a phase discontinuity protection unit and an integrated circuit-breaker failure protection unit.

The phase and neutral overcurrent relay is provided with serial communication capabilities. Vital relay information is immediately available to the relay operator, locally or remotely. Therefore, the phase and neutral overcurrent relays can be used for any application, ranging from stand-alone relay applications to advanced applications comprising fully remote-controlled substations.

The earth-fault relay REJ 511 is a secondary relay which is connected to the current transformers of the object to be protected. The earth-fault unit continuously measures the neutral current of the object. On detection of a fault, the relay will start, trip the circuit breaker, provide alarms, record fault data, etc., in accordance with the application and the configured relay functions.

The earth-fault unit includes low-set stage I₀ > and high-set stage I₀ >>. If the high-set stage is given a setting value within the lower part of the setting range, the relay module will have two nearly identical stages. In this case, the relay can be used in two-stage load shedding applications.

The protection functions are independent of each other and have their own setting groups and data recordings. The earth-fault protection function uses conventional current transformer measurement.

An output contact matrix allows start or trip signals from the protection stages to be routed to the desired output contact.

The overcurrent relay REJ 513 is a secondary relay which is connected to the current transformers of the object to be protected. The overcurrent unit continuously measures the phase currents of the object. On detection of a fault, the relay will start, trip the circuit breaker, provide alarms, record fault data, etc., in accordance with the application and the configured relay functions.

The overcurrent unit includes low-set stage I> and high-set stage I>>. If the high-set stage is given a setting within the lower part of the setting range, the relay module will have two nearly identical stages. In this case, the relay can be used in two-stage load shedding applications.

The protection functions are independent of each other and have their own setting groups and data recordings. The overcurrent protection function uses conventional current transformer measurement.

An output contact matrix allows start or trip signals from the protection stages to be routed to the desired output contact.

The combined overcurrent and earth-fault relay REJ 515 is a secondary relay which is connected to the current transformers of the object to be protected. The overcurrent unit and the earth-fault unit continuously measure the phase currents and the neutral current of the object. On detection of a fault, the relay will start, trip the circuit breaker, provide alarms, record fault data, etc., in accordance with the application and the configured relay functions.

The overcurrent unit includes low-set stage I> and high-set stage I>> and the earth-fault unit low-set stage I₀ > and high-set stage I₀ >>. If the high-set stage is given a setting value within the lower part of the setting range, the relay module will have two nearly identical stages. In this case, the relay can be used in two-stage load shedding applications.

The protection functions are independent of each other and have their own setting groups and data recordings. The overcurrent protection function uses conventional current transformer measurement.

An output contact matrix allows start or trip signals from the protection stages to be routed to the desired output contact.

The directional or non-directional earth-fault relay REJ 517 is a secondary relay which is connected to the voltage and current transformers of the object to be protected. The earth-fault current and the zero-sequence voltage unit continuously measure the zero-sequence voltage, earth-fault current and phase angle of the object. On detection of a fault, the relay will start, trip the circuit breaker, provide alarms, record fault data, etc., in accordance with the application and the configured relay functions.

The voltage unit includes low-set stage U_0b> and the earth-fault current unit low-set stage I₀ > and high-set stage I₀ >>. The earth-fault stages can be replaced by two additional voltage stages, low-set stage U₀ > and high-set stage U₀ >>.

The protection functions are independent of each other and have their own setting groups and data recordings. The voltage and current functions use conventional transformer measurement.

An output contact matrix allows start or trip signals from the protection stages to be routed to the desired output contact.

The overcurrent relay SPAJ 131 C is designed to be used for two-stage phase overcurrent protection of distribution feeders, large low-voltage motors, high-voltage motors, medium-sized and large generators and power transformers. The relay can be used both as main protection relay and back-up protection relay.

The relay has two protection stages: a low-set overcurrent stage I> and a high-set overcur-rent stage I>>. The low-set stage has a definite time or an inverse-time operation characteristic, while the high-set stage has a definite time characteristic only.

The overcurrent relay is provided with five output relays, four of which are freely configurable for the desired function. Two of the output relays have heavy-duty contacts capable of directly operating a circuit breaker.

The combined overcurrent and earth-fault relay SPAJ 320 C is used for short-circuit protection, time overcurrent protection and residual earth-fault protection for radial overhead and cable feeders in solidly earthed or low-resistance earthed networks. The relay may also be used in a variety of other applications requiring phase overcurrent protection and/or residual earth-fault protection.

Three-phase low-set overcurrent protection with inverse time or definite time characteristic
Three-phase, high-set, instantaneous or definite time overcurrent protection
Non-directional, sensitive, definite time, residual current earth-fault protection
Non-directional, high-set, instantaneous or definite time, residual current earth-fault protection
Harmonics measuring module for blocking the earth-fault protection module
Control input for an incoming external blocking signal
Local man-machine communication via push-buttons and digital displays on the front panels of the relay modules
Serial interface for connecting the relay to higher-level data acquisition systems, local or remote control systems or other host systems via optical fibers
Local operation indication via LED indicators with memory function and via the digital display
Compact and robust mechanical design in an aluminium case to IP 54
Continuous self-supervision and auto-diagnostic fault indication to facilitate fault location and repair after detection of an internal relay fault
Powerful software support for parameterisation of the relay, for reading measured and recorded values, events, etc., and for storing readings
Member of the SPACOM product family and ABB’s Substation Automation system

The combined overcurrent and earth-fault relay SPAJ 321 C is used for short-circuit protection, time overcurrent protection and residual earth-fault protection for radial overhead and cable feeders in solidly earthed or low-resistance earthed networks. The relay may also be used in a variety of other applications requiring phase overcurrent protection and/or residual earth-fault protection. The relay is especially used in applications based on the use of inverse time relays both for the overcurrent protection and the earth-fault protection.

The combined phase overcurrent and earth-fault relay SPAJ 135 C is intended to be used for time and current graded overcurrent and earth-fault protection in distribution networks. The relay is especially suited for use in solidly earthed and low-resistance earthed networks.

The relay provides a two-phase non-directional overcurrent protection and non-directional earth-fault protection. The two-stage overcurrent unit includes a low-set stage I> and a high-set stage I>>. The low-set stage I> features field-selectable definite time characteristic or inverse definite minimum time (IDMT) characteristic as per IEC 255. The high-set stage I>> operates either instantaneously or has a definite time characteristic. The earth-fault unit I 0 > also features field-selectable definite time characteristic or inverse definite minimum time (IDMT) characteristic as per IEC 255.

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