ABB REA101-AAA ARC PROTECTION

Description

The REA system is a fast and flexible arc fault protection system for air-insulated low voltage and medium voltage switchgears. A fast and selective arc fault protection system is a natural constituent of a modern switchgear panel and a safety and security investment for older switchgears to protect human lives and prevent or reduce asset damage.

The REA arc fault protection system uses two types of sensors for detecting light: a non-shielded, bare-fiber sensor that detects light along its entire length and light collecting lens-type sensors with typically one sensor installed per switchgear compartment.

The function of the REA arc fault protection system is based on detecting the intense light of an electric arc alone or on a detection of light and simultaneous phase or neutral overcurrent. On detection of an arc fault, the REA arc fault protection system delivers trip commands in less than 2.5 ms to all circuit breakers that feed the fault zone. Furthermore, the operation indicators of the REA arc fault protection system help localizing faults by selectively guiding the maintenance staff to the fault zone, that was identified by the arc fault protection system.

The actual REA arc fault protection system consists of one or more arc fault protection main modules type REA 101 and a necessary number of extension modules type REA 103, REA 105 and REA 107. The main module REA 101 can operate as a stand-alone device or cooperate with other REA 101 modules, and with the REA 103, REA 105 or REA 107 extension modules. The extension modules REA 103 and REA 107 allow the number of sensor fibers and/or lens-type sensors to be increased to extend the area of protection. The use of the extension module REA 105 including fast trip outputs will allow protection schemes with increased selectivity to be created.

The arc flash phenomenon

The consequences of an arcing short-circuit or earth-fault inside a low voltage or medium voltage switchgear panel can be very disastrous. The extremely hot electric arc can destroy valuable equipment causing prolonged and costly distribution downtimes. Moreover, an arc fault poses a serious threat to the switchgear operating and maintenance staff.

An arc fault can arise from, for example, insulation faults and weaknesses, maloperation of a switchgear device, improper (loose) busbar or cable joints, overvoltage, corrosion, pollution, moisture, ferro-resonance (instrument transformers) and even ageing under electrical stress. Most of these fault reasons can be prevented by appropriate maintenance. Despite of all precautions, arc faults may be caused by human error, or by animals entering the switchgear panel.

Time is a critical parameter for the detection and minimization of the effects of arc faults as the arc incident energy rapidly increases by time. An arc fault lasting 500 ms may cause severe damage to the installation. If the arc lasts for less than 100 ms the damage is often restricted, but if the arc is extinguished in less than, for example, 4 ms the damage is insignificant.

Arc fault protection system

For all modules of the REA arc fault protection system the user can select either an automatic or manual compensation system for the ambient light. The compensation system enables adjustment of the sensitivity of the light detection in relation to the reference level based on the intensity of the ambient light measured by the sensors or on the value selected with a setting device on the front panel of the modules. The sensitivity adjustment eliminates the possibility of unwanted operation of the REA arc fault protection system, for example, when an air magnetic circuit breaker or a pole-switch disconnector is breaking current.

Arc fault protection module REA 101

The arc fault protection module REA 101 is the main module of the REA arc fault protection system. The REA 101 module can operate as a stand-alone device or in combination with other REA 101 modules and with the extension modules REA 103, REA 105 or REA 107. The REA 101 module is provided with two extension ports. A maximum of five extension modules can be daisy-chained to each port. Several REA 101 modules can be interconnected via a fiber-optic link communication or the intermediate REA 105 extension module can be used. The REA 101 module can utilize one loop or radial type fiber sensor, or a lens-type sensor for light detection

High speed trip outputs

1.The REA 101 module features two high-speed, galvanically isolated, insulated gate bipolar transistor (IGBT) outputs (HSO1 and HSO2) for CB tripping purposes. In addition, REA 101 offers one heavy-duty relay output (TRIP3) to be used, for example, as a circuit-breaker failure protection (CBFP) output for an up-stream circuit breaker, or as an alarm output. ABB Overcurrent condition The REA 101 module features an adjustable three-phase overcurrent or two-phase and neutral overcurrent condition monitoring function, which enhances the reliability of the arc fault detection by eliminating unwanted CB tripping caused by light not related to any arc fault, like a flash light used in photography.