TOPIC 1 - FAULT FINDING

1. UEENEEG108 TROUBLE-SHOOT AND REPAIR FAULTS IN LOW VOLTAGE ELECTRICAL APPARATUS AND CIRCUITS TOPIC 1 - FAULT FINDING

2. UEENEEG108 TROUBLE-SHOOT AND REPAIR FAULTS IN LOW VOLTAGE ELECTRICAL APPARATUS AND CIRCUITS TOPIC 1 FAULT FINDING

3. TOPIC 1 - FAULT FINDING What is Fault Finding Common Causes and Symptoms of Faults Fault Finding Procedures

4. What is troubleshooting? • It is the process of analysing the behaviour or operation of a faulty circuit to determine what is wrong with the circuit. • It then involves identifying the defective component(s) and repairing the circuit. • Depending on the type of equipment, troubleshooting can be a very challenging task.

5. When Equipment Fails • Urgency to get it fixed • Downtime costs money • Loss of productivity • Costs involved with fixing equipment • Customers often watch you • Puts pressure on you to solve problem faster

6. List 5 steps you should undertake before you start work on a breakdown?

7. 1 Risk assessment • Isolation, working safely at heights, confined spaces, explosive gasses, poisonous gasses.. • There are lots of potential hazards

8. 2 Ask • Find out exactly what the fault is and what were the circumstances that led to it. • Make your own assessment , don’t presume what you have been told is the whole truth, the operator may have made a mistake !

9. 3 Visual Inspection • Check for jammed or seized machinery, • Look for cable damage. • Check fuses or circuit breakers • Check for tripped overloads or cut outs

10. 4 Use your senses • Have a look - some faults can be found simply by taking a look. • Listen - motors will hum if the start capacitor is faulty. • Smell - burnt cables or overloads will smell if heat damage has occurred. • Touch - feel the cables, are they hot?

11. 5 Test • Useyour test instruments to find the fault • Continuity of cables. • Insulation Resistance of cables. • Clamp meters, how much current is being drawn? https://www.google.com.au/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwiGguzPgLzKAhVCo5QKHfjtAD4Q jRwIBw&url=http%3A%2F%2Fwww.lcr-meter.net%2Fmultimeters%2Fhow-to-use-a-multimeter.html&psig=AFQjCNHgqB2N3B0evcPel96iKbF QwyT8Og&ust=1453503472727323

12. NO LIVE WORK!! Testing is considered to be “Electrical Work”

14. Etc………..

15. Can you work on a switchboard (alone) if the main switch is turned off? Main switch turned off

16. COMMON CAUSES OF FAULTS Operator Faults Defective wiring practices Short Circuits Open Circuits Overloaded Circuits Mechanical Faults Supply Faults

17. 1. Operator Faults • One of the most common faults. • Most of the time, the operator has failed to follow a procedure properly or something unexpected has happened. • Eg. Power is turned off

18. 2. Defective Wiring Practices • Loose connections. • Some insulation piercing connectors when applied incorrectly can make poor connections due to insufficient contact area or pressure.

19. 2. Defective Wiring Practices • Aluminum and copper conductors spliced together with an incorrect connector. Aluminum oxide causes overheating. • AS3000:2007 Clause 3.3.2.5 • “Disimilar metals liable to initiate galvanic action shall not be placed in contact with each other” • “Materials liable to cause mutual or individual deterioration, or hazardous degredation, shall not be placed in contact with each other” • Eg. Cabling through polystyrene in portable buildings

20. 2. Defective Wiring Practices

21. 2. Defective Wiring Practices Will only corrode if an “Electrolyte” is present.(Ie. Water). Like a battery…. Water

22. 2. Defective Wiring Practices • Cabling against sharp edges, causing cuts to insulation (particularly in ceilings – ie. Government Home Insulation Program) • Low-voltage applications (such as high-current landscape lighting) with field connections that are exposed to combustibles, such as woodchips, can be dangerous. Even though it’s low Voltage, high currents are involved. Poor connections can lead to fires.

23. 2. Defective Wiring Practices • Polarity • Incorrect polarity (ie. Crossed wires) will make the earthing system live. • Voltage test at the GPO will not show a fault Voltage Test Active to Earth = 230V Active to Neutral = 230V Neutral to Earth = 0V

24. 3. Short Circuits • A short circuit in an electrical circuit is one that allows a current to travel along a path where essentially no (or a very low) electrical impedance is encountered. • Can be between: • Active and Earth • Active and Neutral • Neutral and Earth

25. 3. Short Circuits • This results in an excessive electric current (overcurrent) limited only by the Impedance of the rest of the network and potentially causes circuit damage, overheating, fire or explosion.

26. 3. Short Circuits • Typical Symptom: • Operation of Protective Device

27. 4. Open Circuits • The electrical opposite of a short circuit is an "open circuit", which is an infinite resistance between two nodes. • Can be caused by: • Broken cables • Mechanical Damage • Vibration • High resistance joints • Carbonised contacts • Galvanic action

28. 4. Open Circuits • Typical Symptom: • Appliance/Device does not operate

29. 5. Overloaded Circuits • Overloaded circuits are when too much current flows through the circuit. • Can be caused by: • Too much load on motors • Too many appliances on a circuit • Undersized cables • Undersized electrical equipment (eg. Switches) • Oversized circuit breakers

30. 5. Overloaded Circuits • The outcome of an overloaded device or circuit is • This can lead to: • Breakdown of insulation • Damage to electrical devices • Short circuits • Fires HEAT

31. 5. Overloaded Circuits • Typical Symptom: • Operation of Protective Device • (same as Short Circuit)

32. 6. Mechanical Faults • Non-Electrical (mechanical) faults can often lead to electrical faults • Overloaded motors • Broken parts • External damage

33. 7. Supply Faults • Blackouts • Loss of Supply • Brownouts • Reduction in Supply Voltage • Causes lights to dim • Can cause damage to circuits • V=IR • Decrease in Voltage causes Increase in Current • Loss of Phase • 3 phase systems • Can cause motor damage (overload) • Under Voltage • Over Voltage

34. Wet Arc Tracking • Initially caused by moisture/ conductive material build-up between terminals or plug pins • Forms a path/bridge for current to flow (not enough to trip circuit) • Starts out as a very high resistance path, but over time, carbon build up forms a “track” for current to flow • Current flow causes heat, which can eventually cause fires • Eg. Salt water on aquarium electrical devices or the rinse aid in a dishwasher leaking onto internal wiring.

35. Dry Arc Tracking • Usually caused by overloading and poor connections • Insulation overheats and plastic degrades • Turns plastic from hydrocarbon into elemental carbon (which is a semi-conductor)

36. Insulation Breakdown • Can be caused by: • Overloading • Mechanical damage (immediate or over time) • Insulation can become brittle if cable is overloaded for long periods • Also, some cables are not UV stabilised. • Insulation can breakdown and cause short circuits

37. How do we improve Electrical Safety? • Install RCD’s on all circuits • Install electrical equipment that is suitable for the environment it is in. (eg IP ratings) • Mechanical protection (cables and electrical equipment) • Avoid poor wiring practices • Cable sizing • Connections • Protection • Equipment ratings

38. Circuit Protection • Circuit breakers protect against • Over-current • Short Circuits • If they are sized correctly Over-current Trip Curve B-Curve – 4 times C-Curve – 7.5 times D-Curve – 12 times http://electrical-engineering-portal.com/mcb-miniature-circuit-breaker-construction

39. Circuit Protection • Residual Current Devices (RCD) protect against • Earth Faults RCD only Combined RCD + MCB (RCBO) http://electrical-engineering-portal.com/mcb-miniature-circuit-breaker-construction

40. FAULT FINDING PROCEDURES • Talk to Client/Operator • Observe • Define Problem Area • Identify Possible Causes • Determine Most Probable Cause • Test and Repair • Follow Up

41. Fault Finding Procedure • 1. Talk to Client/Operator • The first report of a fault is going to come from a customer/operator. • It is most important at this stage to get as much information on the fault as possible. • What you are told at this stage may indicate what the fault is and what tools, equipment and spare parts you might require

42. Fault Finding Procedure • 2. Observe • Most faults provide clues as to their cause. There could be visual clues such as signs of damage or improper operation. • Don’t forget to use your other senses; sounds and smells can also provide valuable clues. • Through careful observation and a some reasoning, most faults can be identified to the actual component with very little testing

43. Fault Finding Procedure • 2. Observe (cont’) • Be sure you understand how the equipment is designed to operate. It makes it much easier to analyze faulty operation when you know how it should operate; • Note the condition of the equipment as found. • You should look at the state of the relays (energized or not), • Which lamps are lit, • Which auxiliary equipment is energized or running etc.

44. Fault Finding Procedure • 3. Define Problem Area • At this stage you apply logic and reasoning to your observations to determine the problem area of the malfunctioning equipment. • Understand the circuit and how it operates • Use Circuit Diagrams, Plans or Operation Manuals to help determine: • How the equipment or circuits should operate • What kind of features the circuit has • What voltages you should expect at various points on the circuit • Where components are physically located • How the components are actually wired together • Draw a circuit diagram if one isn’t available

45. Fault Finding Procedure • 4. Identify Possible Causes • Once you have the problem area(s) defined it is necessary to identify all the possible causes of the malfunction. • Sometimes it is possible that there are 2 or more faults in a circuit. One fault may lead to another fault developing

46. Fault Finding Procedure • 4. Identify Possible Causes (cont’) • Make a list of all possible causes in order of likelihood • First look for components which burn out or have a tendency to wear out, i.e. mechanical switches, fuses , relay contacts, or light bulbs. (Remember, that in the case of fuses, they burn out for a reason. You should find out why before replacing them.) • The next most likely cause of failure are coils, motors, transformers and other devices with windings. These usually generate heat and, with time, can malfunction.

47. Fault Finding Procedure • 4. Identify Possible Causes (cont’) • Connections should be your next choice, especially screw type or bolted type. Over time these can loosen and cause a high resistance. In some cases this resistance will cause overheating and eventually will burn open. Connections on equipment that is subject to vibration are especially prone to coming loose. • Finally, you should look for is defective wiring. Pay particular attention to areas where the wire insulation could be damaged causing short circuits. Don't rule out incorrect wiring, especially on a new piece of equipment.

48. Fault Finding Procedure • 5. Determine Most Probable Cause • Once the list of possible causes has been made it is necessary to prioritize the items as to the possibility of them being the actual cause of the malfunction. • 6. Test and Repair • Once you have determined the most probable cause, you must test it to prove it to be the problem or not. • Always try to predict what your measurement should be before you test

49. Fault Finding Procedure • 6. Test and Repair (cont’) • After replacing the component, you must test operate all features of the circuit to be sure you have replaced the proper component and that there are no other faults in the circuit. • It can be very embarrassing to tell the customer that you have repaired the problem only to have him find another problem with the equipment just after you leave. • Document any changes that have been made

50. Methods for Testing Assumptions • Visual Inspection • Component Isolation • Eg. If an RCD is tripping, First unplug all appliances and then plug back in one at a time. • Test Equipment • Use multimeter or other instruments to test if equipment is faulty • Sectional Testing • Test one section at a time • Split-Half Tests • Split the circuit up and test each half to isolate the problem • Repeat as required until fault is found