Electric.ie Issue 39 May-June

42 ELECTRIC.IE • The Magazine & Website for the Irish Electrical Industry • Eaton Eaton introduces the AFDD+ - The next step in the evolution of protection ‹† ›‘— ‘™ –Šƒ– ƒ’’”‘šǤ ͞͡τ‘ˆ ƒŽŽ ”‡•‹†‡–‹ƒŽ Ƥ”‡• ƒ”‡ ‡Ž‡…–”‹…ƒŽŽ› ‹‰‹–‡†ǫ ƒ–‘ǯ• ‹‘˜ƒ–‹˜‡ ͳ‹ͱ φǡ ƒ”…ˆƒ—Ž– †‡–‡…–‹‘ †‡˜‹…‡™‹–Š ‹–‡‰”ƒ–‡† Ȁ ǡ ’”‘–‡…–• ’‡‘’Ž‡ǡ ’”‘’‡”–› ƒ† ƒ••‡–• ƒ‰ƒ‹•– Ƥ”‡ Šƒœƒ”†…ƒ—•‡† „› ƒ”…•Ǥ Š‹• ‡™ ƒ–‘…‘’‘‡– †‡–‡…–• Š‹‰Š ˆ”‡“—‡…› ’ƒ––‡”• ‹ ‡†…‹”…—‹–• –Šƒ– ‹†‹…ƒ–‡ –Š‡ ‡š‹•–‡…‡ ‘ˆ ƒ ƒ”…ƒ† ™‹ŽŽ ƒ—–‘ƒ–‹…ƒŽŽ› •™‹–…Š ‘ơ –Š‡ ‡†…‹”…—‹– –‘‹‹‹œ‡ –Š‡ ”‹• ‘ˆ Ƥ”‡•Ǥ An arc fault, which could be described as a ‘micro-lightning’, is a high power discharge of electricity between two or more conductors, generating a build-up of heat that can damage the ‹•—Žƒ–‹‘ ‘ˆ ƒ ™‹”‡ ƒ† –”‹‰‰‡” ƒ Ƥ”‡Ǥ Arc faults occur frequently arising from vulnerable points in an electrical installation, due to factors including damaged wiring, which can be caused by rodents, overexposure to sunlight or misguided drilling. Other causes of arc faults include overheated or stressed electrical cables, worn- out electrical insulation, loose connections or contacts and defective electrical appliances. Arcs can occur suddenly or develop over many years, creating a hidden danger for people. A fast detection of an arc is therefore crucially important. Long-established protection devices such as RCDs and MCBs most often are not able to detect arcs. Serial and parallel arc ˆƒ—Ž–• ‹ ƤƒŽ…‹”…—‹–• ƒ”‡ •‘‡–‹‡• also referred to as low-current arc faults which were undetectable until the invention of the Arc Fault Detection Devices. ‡”‹ƒŽ ƒ”…ˆƒ—Ž–• Serial arc faults are low-current arc faults in a conductor (phase or neutral) which current most often will stay below the tripping threshold of the circuit breaker and will therefore not (always) trip of current signals, to provide sensitive detection of fault currents, combined with avoidance of nuisance tripping. The EATON AFDD+ has been developed to ensure that other high frequent signals on the grid do not interfere with its detection capability. The installation of arc fault detection devices (AFDDs) is recommended under the international standard IEC 60364 (Part 4-42). Some countries, such as Germany, have implemented national codes that require –Š‡‹” —•‡ ‹…‡”–ƒ‹ •’‡…‹Ƥ‡† circumstances, making them partly mandatory. In the US, where AFDDs are known as arc fault circuit interrupters (AFCIs), the use of arc fault detection is required by the National Electric Code. This protection device is particularly suitable and recommended for buildings where people reside temporarily or permanently, buildings with irreplaceable goods (e.g. museums) or goods of a high value, as well as central infrastructure (transshipment points of goods) which includes, amongst others, train stations, airports. ƒ”ƒŽŽ‡Ž ƒ”…ˆƒ—Ž–• ƒ”ƒŽŽ‡Ž ƒ”…ˆƒ—Ž–• Ȃ ‘™Ǧ…—””‡– ƒ”… faults between phase and neutral most often stay below the tripping threshold of MCB’s which will therefore not (always) trip. Low- current arc faults between phase and earth with a leakage current most often are higher than 30mA. In which case the Residual Current Circuit Breaker will trip. A breakdown of the fault current, close to the zero- crossing of the driving voltage is a typical indication of the presence of an Arc fault. ƒ•– ƒ† •‡•‹–‹˜‡ †‡–‡…–‹‘ ‘ˆ ƒ”…ˆƒ—Ž–• An AFDD+ uses embedded processing and smart evaluation