General It is important to note that DISCRIMINATION is ensuring that the correct device operates when a fault or overload occurs – not, as many mistakenly take it, the nearest or smallest device. But with a bit of logical detective work, you should be able to find the cause of the problem - and, in many cases, correct the fault yourself. This will require more power when a restriction is in place & thus create an overload situation. We were called in when others failed in getting a machine running. From the above, if a reading of 0.00Ω was seen, then the two cables being tested are in contact with each other at some point in that circuit. This condition is verified (or tested for) by utilising the R1 + R2 test method of linking the Phase to Earth at the DB and testing at the point where a reading would be expected between PH-E. The healthy side can now be disregarded and the half-test carried out again on the damaged side of the circuit. For shielded cable, insulation is used to limit current leakage between the phase conductor and … Observe the system running, if you consider it safe to do so. The test involves wiggling the wiring to see if a fault occurs. This may be a simple task, as in the case referred to above, or it may be a much bigger one. The Polarity referred to throughout this section is not the type of Polarity referred to in electronics, where if the positive and the negative points of a circuit are reversed damage could be caused to a component or a circuit board. Why?...the IR test will tell you what you want to know..a low current continuity test will show open circuit with a resistance of 10,000 ohms,where a 500v IR testwill give a low reading of 0.1 Mohm...a fault 6th Insulation resistance test between conductors (IR tester).readings should be higer than 1 M ohms. For example, if a door bell does not ring when it should, it is only by means of a systematic approach that one determines that the bell itself is faulty. To locate the point the circuit must next be disconnected as near to its mid-point as possible. Before attempting any electrical test, for your safety, you should be sure you feel confident to do so if you have any doubt hire a professional to carry out these tests !!! If one is in doubt as to whether anything is relevant, then include it. Finally, look closely at Figure 3. One end of the faulted cable is connected through a pair of resistors to the voltage source. A.Level 2 Certificate in Engineering IVQ – Electrical and Electronics Technology (2850-84), learners must achieve 35 credits: • 21 credits from the three mandatory units plus, • a minimum of 14 credits from the two optional units..OR . It is always worth remembering that Motor & Control Circuits often contain Internal Fuses –  & what may seem like a loss of supply could be an internal fuse having blown. One of the most important factors in doing this, is the approach used. Remember ! How to identify electrical faults. Answer ALL questions. It is important to ensure that the machine, equipment or system is functioning normally after the cause of the fault and the fault itself has been dealt with. Candidates on the electronic fault finding training course use a range of circuit boards to explore the function of the various electronic components. In the case of the puncture, it is easy to confirm that the cause of the fault – and the fault itself – has indeed been dealt with satisfactorily, assuming that the tyre remains inflated. An earth fault on one phase of a 3 phase supply will disconnect. proves that insluation is not damaged and no loose connections. CORRECT or INCORRECT answers are indicated at the TOP of the page. All the evidence collected must be relevant to the problem in hand. Fault finding means the testing of the operation of electrical equipment to determine if that electrical equipment is safe and working correctly as defined in the Victorian Electricity Safety (Registration and Licensing) Regulations 2010.. A fault-finding test, such as the fault-finding Accenture exam or the SHL aptitude assessment, is an online test used to evaluate interested applicants. Murray loop bridge. If none is seen (ie: open circuit, > 200Ω), then the test would be moved to the N – E of the same termination point. What are the six key steps to approach electrical fault finding? Collect the Evidence. Looking at Figure 1 (other side of this sheet), the lighting circuit is seen to be ‘switched off’ and therefore it should be seen as safe to work within any of the modular fittings repairing or replacing parts – but on closer inspection it can be seen that the NEUTRAL is passing across the switch, not the phase, and therefore the phase section of the terminal block (and any part thereafter) remains live even with the switch in the open* position. All Rights Reserved. When electrical energy is generated in the generations’ stations, it is distributed to the different loads, i.e. By Warren Rhude, president of Simutech Multimedia Inc. To expertly troubleshoot electrical equipment, problems must be solved by replacing only defective equipment or components in the least amount of time. If there is a problem in electric circuit then possible causes may be; 1. For further resources, why not check out our video support library and our electrical testing & electrical safety blog. Control Circuits often contain Internal Fuses – what may seem like a loss of supply could be an internal fuse having blown. Single & 3PH motors will react to a restriction in movement by struggling to reach their optimum speed. Single & 3PH motors will react to a restriction in movement by struggling to reach their optimum speed.  Take measurements around the circuit, but mentally predict what they should be. Consider all the evidence collected and, if possible, reject any which after further careful consideration is not relevant. The testing equipment used to detect faults in the operation of electronic devices by creating stimulus signals and capture responses from electronic devices under test is known as electronic test equipment. While these are effectively carrying out the same job, the fuse is part of an isolation device, which is in place for a different purpose to the Circuit breaker at the DB. cities, towns and villages for consumption then. Introduction. Newly Installed work – CB’s tripping once power is energised. This definition supplements the requirements already mandated by Sections 43 and 44 of the Electricity Safety Act 1998. This is a skilled analysis using a dedicated meter which incorporates a number of variable resistors and an ammeter.  inductors can store energy in a magnetic field and give electric shocks. Hopefully the installer will have some indication of the most likely ‘trouble spot’ area within the installation that any fault (earth of short circuit) may have occurred once the Main DB is commissioned and the circuits are switched on – eg: a spur off a ring that was difficult to terminate at the 2nd Fix stage, or a multi-gang switch that had a number of 2 and 3 core cables in the same enclosure, and seemed constricted when the face plate was screwed on. Once you learn the symptoms of each it should become straightforward to resolve the issues you will encounter... Why (Loose Connection – Tripped CB – Blown Fuse – Internal Fuse), Tripping Circuit Breaker/RCD – device will not re-engage (or will for a short while - then possibly a switched circuit contains the fault), Type B – Type C – Type D Circuit Breakers / S’Type RCD’s, Switches – Relays –Contactors, etc, not functioning correctly (brings about the decision as to replace or repair), Internal Wiring/PCB’s & Electronics (How far to go for an ‘electircian'). Fault finding and rectification - advanced, test instrument settings, readings, test procedures, typical faults, supply faults, fault-finding procedures - 8 questions from a bank of questions . The cause of the puncture may be a nail which has penetrated the outer cover. The process involves stepping up the voltage to minimize the loss of energy in the form of heat. One side would read >999MΩ, and the other would continue to read 0.00Ω. At supply Origin – at a single outlet (Phase Neutral reversed or neutral earth reversed) or at a single fitting (Phase – Neutral) – Live Test Vs Dead Test. There are only a certain number of reasons why a circuit will have ceased to operate as it should. Further reading: Become an Electrician To locate the point the circuit must next be disconnected as near to its mid-point as possible. Intriguingly in this case the use of a 100mA RCD as a main switch could well give rise to nuisance tripping throughout the life-span of the installation, because the discriminatio0n of the device would be seen to be incorrect. Control Circuits (Internal Fuses) – Contactors (Breakdown of Parts)  – 3PH motors (Loss of  Phases &/Or burnt out coils) – Single Phase Motors – (Carbon Brushes), Reversed Polarity – Discrimination – loose connections – Protective Devices –Faulty Portable equipment – (NB: Cannot be ‘ware and tear’). Whatever is the case, it is a specific task based on earlier findings. Look for any feedback given if you get an answer incorrect. If the cause of a fault is not removed, the fault will recur even though the fault has been rectified. Devices shipped with integral Ground Fault Interrupting cords (such as blow dryers, etc.) T. Tt12zza. The terminals in the under-section of a kWh meter are normally as follows: (from left to right). Some of these boards have switched faults on them so that the candidates start to gain some fault finding experience. If the reading were less than the maximum for the instrument being used (ie a meter that would normally read >999MΩ was indicating 329MΩ) – and was dropping as the test were being carried out, part of the circuit would be seen as erroneous, and must be further investigated. Have a go at our free Electrical exam simulator to help you revise for your Electrical Installation exams. In this case the entire neutral bar would be permanently live, and the CB’s would be making and breaking the Neutral – once again giving risk of electric shock under numerous circumstances. In figure 2 (other side of this sheet), the problem with, Potential cause:               1.Overload (time to trip or blow will determine the likelihood), 3.Faulty device (is it operating functionally – opens and closes), 4.Dead Short – in real terms this could trip a circuit breaker for, Type C/Type 3        Motor Circuits – Inductive Loads. Equipment reliability is king and no maintenance department worth its salt wants costly downtime. We talk to Dale Biggs, Upstream Production Manager at AG Barr, about how training delivered by MCP is equipping shop-floor staff with invaluable maintenance skills to keep production lines moving. If you are convinced that the Earth is touching the phase (or vice-versa), or the PH is touching the N prior to the load, then you would carry out an IR test at 500 Volts DC between the Ph & E or Ph & N. If a reading of 0.00Ω was seen, then the two cables being tested are in contact with each other. If the puncture is repaired (i.e. This situation is verified by using a set of Approved GS38 Test Lamps and testing from: PH – N             (230V expected)      PH – E            (230V expected) N – E               (0V expected). Fault finding and rectification, test instrument settings, readings, test procedures, typical faults - 8 questions from a bank of questions. You will have to state the methods required for repairing the faults. Whether they’re working on tanks in the armed forces or repairing a city bridge, technicians, civil engineers, and security personnel need to know how to spot and quickly fix equipment. From the above, if a reading of 0.00Ω was seen, then the two cables being tested are in contact with each other at some point in that circuit. To perform this test, it is necessary to have a sound cable running alongside the faulty cable. In this case if the wiring were terminated across a one way switch, it would not in fact turn the lamp on and off – the lamp would be perpetually receiving a phase and a neutral, & therefore stay ‘on’. To help technicians get to the cause of a fault faster, MCP has developed a course focusing on a logical approach to fault finding. Answer ALL questions. If the initial reading were less than the maximum for the instrument being used and continued dropping as the test were being carried out, part of the circuit would be seen as erroneous, and must be further investigated using the half test method. As modern equipment of all types becomes more dependent on electronic control systems (and arguably more complex) the ability to approach problems logically in order to find the cause of the fault is … Study the hard core of relevant evidence and – through the process of careful, logical thinking –diagnose the likely fault or at least the area or region of the fault. the fault is removed) this will not be of much use if the cause of the puncture in the first place is not determined and appropriate action taken. However, if the phase in one of the fittings were to touch the earth, in this case the RCD would operate. How to identify electrical faults. Some of these also have switched faults. Our courses have been delivered across the UK and around the world. Copyright © 2020 DJT Electrical Training. All a bit of a disaster wiring wise– but the correct term to describe the switching remains incorrect polarity – as the switch is not in the phase conductor only. 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If a Low Ω reading were obtained at that point this would indicate reversed polarity, and must be investigated further. Electrician Training - A Systematic Approach to Trouble shooting and Electrical Fault Finding. For intermittent faults, perform the wiggling test on wiring. Megger – Fault Finding Solutions For the purposes of this document on cable fault locating, only leakage current through the insulation will be considered. Here, John Saysell, Head of Business Development and Technical Training at MCP Consulting Group, explains his Six-Step Approach to Fault Finding…. State and record how the identified faults can be rectified. Discrimination: Conventional Paradigms A device trips; causing complete or partial loss of Power, where this could have been avoided & only have separated part of the supply from one protected point of the circuit if correct discrimination were in place. Short Circuit - A connection that may be closed is called short circuited. Here we outline two alternative approaches to achieving competence. Cable Fault Finding Solutions. Type D                   Large Inductive Loads – Large Motors, X-Rays. During the course of assessing more than 1,000 candidates over a 15 year period, MCP has found fault finding to be the second biggest weakness in maintenance trade tests. The quantity of information collected is unimportant, what matters is that all information collected is relevant. Troubleshooting is the process of tracing and rectifying faults in electric/electronics circuit. Gather Information – Ask people when & how the fault occurred Analyse Information – decide the probable cause Investigate – find the fault Rectify – safely repair the fault Test – test before re-energising. It is more important than ever that industrial employers understand their legal responsibility to make sure their technicians are competent to carry out their tasks. 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