— MV Drives – Main Protection and Personnel Safety 2021/03 – 3BHS883924 Arc Resistant Design — Introduction Electrical failures and arc faults Bolted Short Circuits Arc Faults – Bolted short circuits are caused by a breakdown of a component that ends in a solid conductive electrical connection – Arc Faults are caused by a breakdown of the insulation – Due to low resistance of the fault, only a low energy is absorbed into the fault Thermal stress is limited (short term) – The low impedance short circuit causes potentially high short circuit currents – Short circuit currents flow through ionized air, called an arc As a primary effect, high energy is released, causing a pressure, sound and heat wave Harmful gases and particles represent a secondary danger High mechanical stress on the components in the short circuit path (magnetic field) There is no immediate safety risk – Probability of occurrence is related to the reliability of the electrical components. – Typical MTBF of the power circuit is in the range 15 – 30 years October 4, 2021 Slide 2 There is an immediate safety risk Probability of occurrence is very low Choosing clearance and creepage distances in accordance to relevant standards reduces risks of occurrence — ABB MV Drives Main protection and safety barrier Main circuit breaker (MCB/ICB) – Major protection device of the frequency converter – See important safety note 3BHS230517 – Maximum opening time is critical Short circuit occurs Open and / or trip command is set at the frequency converter control output No further damage of frequency converter No hazard to personnel Max. protection trip time Max. safety trip time October 4, 2021 Slide 3 Max. protection trip time: Max. safety trip time: Maximum opening time that ensures minimum HW damage inside the drive in case of bolted short circuit Maximum opening time that ensures* no personnel safety risks due to arcing in the converter section Minimize HW damage Minimize safety risk * “ensure” means: converter meets relevant standards for drives or product is classified as arc fault resistant — Arc Fault Safety ABB’s approach - the 4 safety classes • • CLASS I CLASS II CLASS III CLASS IV protection based on arc prevention protection based on arc resistant cabinet structure protection based on external arc fault limitation and elimination fast arc elimination Design of insulation systems in accordance with relevant IEC and NEMA standards to prevent arcs and provide personnel safety Class I is not a certified arc resistant design, it is mainly focusing on arc fault prevention • • • The cabinet is designed to withstand the pressure of an arc flash Arc fault is contained in the cabinet or guided through pressure relief vents The drive will face severe damage after an event • • HV Fuses are applied externally to the drive in order to limit the arc fault current to less than half cycle of the fundamental AC frequency (< 10ms in case of 50Hz supply) This method is only used to reach arc resistant designs for MV drives connected without external drive transformer to the mains (integrated transformer solutions and DTL solutions) • • • This is an ABB patented method, ABB MV drives “protection firing” system. The arc fault is detected and converted into a non severe bolted short circuit For an even faster detection and elimination an optical ABB arc fault detection system is available Provides highest level of personal safety and the equipment remains undamaged and can be immediately restarted after inspection and elimination of the arc ignition cause Arc resistant design IAC Certified according IEC62271-200 / IEC 62477-2 October 4, 2021 Slide 4 — Safety Requirements Standards with arc resistant design requirements Standards without arc resistant design requirements Relevant standards for MV drives Switchgear IEC NEMA UL IEC 62271-200 High-voltage switchgear and controlgear IEC 62477-2 Safety requirements for power electronic converter systems and equipment IEEE C37.20.7 none IEEE Guide to test metal-enclosed switchgear UL347 Medium-Voltage AC Contactors, Controllers, and Control Centers - Presently there is no relevant standard released for arc resistant design of MV drives - ABB and other companies have applied switch gear standards. - IEC and IEEE are very similar October 4, 2021 Power Electronic Converters Slide 5 UL347 (a) Medium Voltage Power Conversion Controllers - A new IEC standard relevant for MV drives has been released - This standard will be relevant in IEC and (likely) also in NEMA world - The standard allows to reuse the certifications according switchgear standards Drives IEC IEC 61800-5-1 Safety requirements, Electrical, thermal and energy IEC 61800-5-1 Safety requirements, Electrical, thermal and energy none - This are most relevant standards for MV (and LV) drives safety requirements - Future revision will reference to IEC 62477 (-1 for LV) and (-2 for MV) for arc resistant design — Migrating from IEC 62271-200 to IEC 62477-2 Definition • • IEC 62477-2 Safety requirements for power electronic converter systems and equipment – Part 2 defines an internal arc classification (IAC) system for MV Drives Future revision of MV (and LV) safety requirement standard will reference IEC 62477-2 for MV Drives arc resistant design, classification and test • IEC 62477-2 describes 6 internal arc fault safety concepts • Test results based on IEC 62271-200 performed prior to release date of IEC 62477-2 can be transferred • Rated arc fault current and arc fault duration are listed on the IAC rating plate along with the accessibility types for each classified side of the equipment. October 4, 2021 Slide 6 * PPE – Personal protective equipment Concept/Measure Product property Test Required Specific prevention: 1. Arc-prohibiting design 2. Active protection 3. Passive protection 1) no arc possible, arc would not start on its own 2) arc is not bridging different power Sources Avoid damage: Stop the arc evolving Withstand damage: Yes Yes Withstand the full arc (pressure wave, heat, gas) Yes 4. Distance Limit the area of damage Yes 5. Housing - No 6. Wear PPE - No — Migrating from IEC 62271-200 to IEC 62477-2 Comparison ABB’s approach - the 4 safety classes CERTIFIED SAFE FOR PERSONNEL ACC. TO IEC 62271-200:IAC AFLR CLASS III and II CLASS I 2 Active protection 3 Passive protection 4 Distance 5 Housing 6 Wear PPE N/A ARC PREVENTION + FAST ELIMINATION ARC PREVENTION + PROTECTION OR ELIMINATION ARC PREVENTION ARC PREVENTION USAGE OF PROPER PPE MANDATORY NO ARC POSSIBLE, ARC NOT START ON ITS OWN BASED ON PROTECTION FIRING AND/OR FAST DETECTION BASED ON ARC RESISTANT ENCLOSURE OR BASED ON HVFUSES BASED ON RESISTANT ENCLOSURE BASED ON DESIGN ACC. TO IEC 60146-1-1 IEC 61800-4 N/A NONE NEGLIGIBLE MODERATE SEVERE SEVERE SEVERE 1 Arc-prohibiting design CONCEPT/MEASURE PERSONNEL SAFETY BASED ON EQUIPMENT DAMAGE IN CASE OF ARC October 4, 2021 CLASS IV Slide 7 * PPE – Personal protective equipment — Arc Fault Safety Arc resistant design Equipment is called “arc resistant” in case it has passed certification tests in accordance with IEC 62477-2 or IEC 62271200 / IEEE C37.20.7 if test performed prior to IEC 62477-2 release date Test – Test equipment is surrounded with highly flammable cotton – Ignition of an arc inside the cabinet (place with highest probability) – Maximum arc rating current is feed into the arc for a defined time Test criteria – Multiple criteria per standard – During the test duration: no damages or any burning signs are allowed to be recorded in the cotton October 4, 2021 Slide 8 IEC standard defines IAC (Internal Arc Classification) for equipment passing the tests Examples: FLRTB, means the equipment is safe from front (F), left side (L), right side (R), top side (T), bottom side (B), Black cretonne 150 g/m2 cotton indicator (AA.5.2.2) at d m distance (2b), associated protection is required (APR), special condition (SC) — Arc Fault Safety Different parts of the drive system sees different max currents Main power line Input section Input transformer Rectifier DC-link Inverter Output filter Motor 50 M Network short circuit Converter internal short circuit is limited by transformer & filter Barrier transformer impedance limits short circuit current/power October 4, 2021 Slide 9 * Only relevant for sync bypass Motor / Network* short circuit Barrier filter impedance limits short circuit current/power — Arc Fault Safety Basis for arc current ratings and times Main power line Input section Input transformer Rectifier DC-link Inverter Output filter Motor Main power line 50 Input section Input transformer Rectifier DC-link Inverter Output filter 50 M M Maximum currents Maximum currents – Worst case arc fault reached when all transformer secondary systems are feeding into an arc in parallel – Integrated transformer and DTL versions are directly connected to the mains. – Maximum arc fault current is mainly defined by main transformer impedance, secondary voltage and number of secondary systems Time – The arc resistance time has to be sufficient to guarantee safe interruption of fault current. – The products have been rated for times in a range of 250ms – 500ms, which is sufficient for: • The protection relay of the main circuit breaker can detect the fault current and open the breaker • In case the breaker doesn’t open, the breaker on the next upper level can still be opened – Those products are therefore exposed to full short circuit current rating of the supply at the primary side of the transformer or decoupling inductor Time – Since the short circuit rating of the supply can be extremely high, ABB offers arc resistant design for this products only in combination with an external current limiting fuse located in the feeder line – The current limiting fuse will limit the short circuit current to half cycle of the fundamental frequency, at 50Hz < 10ms. Tests are done with minimum 10ms The external current limiting fuse only protects in case of arc faults at the primary side of the transformer. The secondary side arc faults are handled the same way as for external transformer solutions. Therefore, a second IAC rating is provided for those products. October 4, 2021 Motor Slide 10 — ABB MV Drives Arc resistant design offering Product ABB class Concept / Measure** IAC Rating Third body certificate Availability in DriveSmart ACS1000a and w I 4. none - default ACS1000a II 3. 5kA / 0.5s 12123Ra option ACS1000w II 3. 6kA / 0.5s 15kA / 0.5s 11075Ra 11077Ra option C+ (Reinforce Cabinet) ACS2000 DFE IEC I 4. None II 3. 15kA / 0.45s 15114Ra option IV 2. 18kA / 0.5s 15114Ra option I 4. none - default II 3. 3.5kA / 0.5s 12035Ra option I 4. none - default ACS5000w FS1, 2 & 3 IV 2. 19kA / 0.5s 12116Ra/11176Ra default ACS5000w FS4 IV 2. 28kA / 0.5s 11176Ra default ACS6000 / ACS6080 II 3. 20kA/ 0.5s 09067Ra option IV 2. 20kA / 0.5s 1202 Bm-1 default (protection firing only) IV 2. 50kA / 0.5s 1202 Bm-2 option I 4. none - default II 3. 23kA / 0.5s 11011Ra/2196-19 option (*) ACS2000 AFE IEC ACS5000a MEGADRIVE-LCI October 4, 2021 Slide 11 default Products with integrated transformer: Product ABB class Concept / Measure** IAC AFLR Rating Third body certificate Availab ility in DriveS mart ACS580MV I 4. none - default ACS1000i I II III 4. 3. 3. 13021Ra/13023Ra 13017Ra default option option I 4. None - Default III + II 3. 15kA/50kA for 0.45s/0.02s 15114Ra/15115Ra option III + IV 3. + 2. 18kA/50kA for 0.5s/0.02s 15114Ra/15115Ra Option ACS2000 DTL I 4. none - default ACS5000i I 4. none - default ACS2000 DFE IEC . . none . 6kA/20kA for 0.5s/0.1s 6kA/20kA/50kA for 0.5s/0.1s/0.01s – Integrated transformer solutions from ABB are available up to 7MVA. For this power range it is common approach to use «fused contactors» as MCBs Therefore in many cases the external current limiting fuse is already available. – Attention: fuses within the drive as part of the optional integrated “fused line-side contactor” do not replace external fuses. The fuse has to be external FS: Frame Size (*) Power cable entry from top is not compatible with the “arc resistant” design. Reason is that the space on top is limited (cable entry, pressure relieve flaps & fans). In case this combination is required a Cplus needs to be issued. Depending on the type of LCI it might be required to increase the size of the terminal unit. Minimum ceiling height: 3.5m! ** Definition according to IEC 62477-2
