19EATON CORPORATION BR003010ENArc faults or arc flashesQuestions about the initial testing of the installationAs an electrically skilled person, how can I ensure the effectiveness of the protective measures, test the AFDD and document the testing?The AFDD+ combines the AFD-unit, RCCB and MCB functionalities. The EATON AFD-unit can be tested with the test button, this triggers a built-in self-test function to check the AFD-unit electronics and finally triggers the RCCB part, too. In addition, the EATON AFD-unit periodically performs a self-test and checks all electronic functions. The MCB and RCCB parts need initial testing. The MCB part has to be chosen accor-ding to the nominal current and the possible short-circuit current of the final circuit. The latter has to be checked with an installation tester. Finally, the RCCB part needs tripping with an installation tester. The verifications of the MCB and RCCB parts have to be documented in a test protocol.What is the difference between an arc flash and an arc fault?In practice, the term „arc flash“ classically refers to an arc that occurs in high- power systems, in areas with a low or even high voltage. The causes are mostly parallel fault currents between multiple phases, phase and neutral (conductor) or phase and earth. However, arc flashes can also occur as breaking sparks on railways, for example.The term arc flash comes about due to the high current (25-150 kA or higher) that leads to an explosive increase in pressure and temperature. So-called arc flash detection devices (e.g. ARCON®) are protection devices that create an intentional mechanical short-circuit within a few milliseconds in order to dissipate the energy from the arc flash as quickly as possible via an induced voltage drop. This short-circuit is created in the physical close proximity of the main switch and is maintained until the main switch is disconnected, so typically a few hundred milliseconds.Arc faults describe arcing currents within the nominal or operating current of a system (mostly less than 125 A). These appear mostly in low-voltage installations and can remain undetected for a long time. They can occur, for instance, due to broken, crushed or damaged cables and wires, as well as loose contact points and insulation faults. Arc faults typically occur as serial arcs along a wire or termination clamp. Under certain circumstances, they also occur as parallel arcs between phase and neutral conductors. Arc faults can only be effectively detected and disconnected by AFDDs. Even arc faults of currents as little as a few amperes can ignite materials surrounding the location of the fault. ?
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