Arc Fault Detection Devices (AFDDs) Protecting People and Property

Transcription

1 Arc Fault Detection Devices (AFDDs) Protecting People and Property

2 Singapore Standard : CP5 Code of practice for electrical installations - Foreword 2

3 BS 7671 : the 18 th Edition report Short Brief 3

4 BS 7671 : the 18 th Edition report Significant changes Protection against overvoltage 4

5 BS 7671 : the 18 th Edition report Significant changes Protection against overvoltage 5

6 Overview Electrical Switchboard has to be safe and available balanced with the constraints of reliability and maintainability. Safety Reliability Availability Maintenability Switchboard conforming to IEC provides insurance on switchboard realization quality 6

7 Why arc flash protection? 7

8 What is arc flash/blast? 8

9 Statistics related to arc flash incidents US Statistics Arc flash injuries 30,000 Arc Flash Incidents per year 7,000 Burn Injuries per year 2,000 Hospitalisations per year 400 Fatalities per year 80% of Electrical Worker fatalities are due to burns, not shock - Arc flash statistics 2013 by ISHN 9

10 Statistics related to arc flash incidents 10

11 Statistics related to arc flash incidents The fifth victim, in his 40s, suffered some discomfort in his left ear, following the incident. He told Shin Min Daily News at the hospital that when he and a manager were in the room overseeing electrical works, they saw a sudden flash of light before hearing a very loud explosion. 11

12 What happens? Time matters! 0.2 sec Steel fire 0.15 sec Copper fire 0.1 sec Cable fire 12 kv, 40 ka 12

13 Causes of arc accidents The most common reasons for arc flash accidents Human errors Mechanical faults Bad connections Aging/Insulation defect Animals When do arc flash accidents occur? 25 % without operator 10% with operator in front of a closed door 65 % with operator working in the switchgear 13

14 Arc flash standards and regulations World wide standard US IEEE-1584 OHSA NFPA 70E ABS Europe: IEC work-arc box Asia AS/NZS 3000/4836 GB/ Specification for arc flash equipment 14

15 Arc flash standards and regulations World wide standard US IEEE-1584 OHSA NFPA 70E ABS Europe: IEC work-arc box Asia AS/NZS 3000/4836 GB/ Specification for arc flash equipment 15

16 Arc flash study history 25th annual Electrical Engineering Safety Seminar 2015, Australian 16

17 Arc flash study history 25th annual Electrical Engineering Safety Seminar 2015, Australian 17

18 What s future of arc flash study? 25th annual Electrical Engineering Safety Seminar 2015, Australian 18

19 What are the directives in Australia? 25th annual Electrical Engineering Safety Seminar 2015, Australian 19

20 What are the directives in Singapore? 20

21 Incident energy (IE) calculation IEEE 1584 NFPA 70E The end customer doesn t want to do this calculation 21

22 NFPA Hazard Levels Hazard Risk Category Typical Personal Protective Equipment (PPE) Arc Rating (cal/cm 2 ) 0 Non-melting, flammable materials with at least 4.5 oz/yd AR pants and AR shirt, or AR coverall Cotton underwear, plus AR shirt and AR pants Cotton underwear, plus AR shirt and AR pants and AR coverall Cotton underwear, plus AR shirt and AR pants and multilayer flash suit Moonsuit 25-40

23 Typical PPE Suit Requirements <1.2 cal/cm cal/cm cal/cm cal/cm cal/cm 2

24 Mitigation activities?

25 Incident energy (IE) reduction

26 Incident energy (IE) reduction

27 Arc flash detection and outcome minimization : Arc guard system TVOC-2 27

28 Arc guard system TVOC-2 How does it work? Arc initiation Detection Activation Breaker opens 1. Arc is detected by the fiber optic sensor 2. Signal is sent to the TVOC-2 arc monitor 3. TVOC-2 arc monitor sends a trip signal to shunt trip of circuit breaker 4. All this occurs in under 1ms 28

29 Arc guard system TVOC-2 How does it work? 29

30 Arc guard system TVOC-2 Safety Integrity Level - SIL Safety Integrity Level (know as SIL) as per IEC and IEC A measure of safety system performance in terms of Probability of Failure on Demand (PFD), established to define a metric for evaluating a system s (or function s) level of operational reliability with regards to maintaining safety TVOC-2 is certified with a PFD of 3.49 x ( ) per year for a period of 10 years after it is first connected (as long as suggested maintenance is performed annually) 30

31 Arc guard system TVOC-2 Safety Integrity Level To meet SIL-2 safety standards, we need: Redundancy Hardware (IGBT s, relay outputs, IRF,etc) Software (HMI, PC boards, etc) Reliability Self-monitoring of internal faults All light sensors will be manufactured and tested in similar conditions according to EN ISO Reduce the probability of errors caused by external factors Cannot adjust the sensitivity of the sensors Cannot shut down the system for maintenance Cannot change safety configuration parameters via HMI Third-party certification TVOC-2 is certified SIL-2 by TÜV Rheinland 31

32 Arc guard system TVOC-2 Installation Example 32

33 Arc guard system TVOC-2 Where the system is used Chemical Plant Oil Rigs Substation 33

34 Arc guard system TVOC-2 Where the system is used Manufacturing Hospital Transport 34

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36 Arc guard system TVOC-2 Current Sensing Module to prevent Nuisance Tripping Used to monitor current Simply connect CT s with an output of 1, 2 or 5A Can monitor only 1 phase although 3 is suggested Must be adjusted to nominal current level Once current reaches 140% of set level, trip signal is sent 2 types of signals sent from CSU to TVOC-2 1. Light = no fault, proper operation 2. No light = overcurrent signal Total reaction time of TVOC-2 + CSU = 2-3ms when monitoring current on 3 phases 36

37 Arc guard system TVOC-2 How does it work? 60W at 2 cm of distance Arc detected lux (symbol: lx) is the SI derived unit of illuminance and luminous emittance, measuring luminous flux per unit area 37

38 BS 7671 : the 18 th Edition report Full report 38