Steve Humphries, Technical Commercial Director at NAPIT, reveals the secrets behind bug detection.
An electrical failure is not a natural event, but rather an unplanned event that happens unexpectedly.
When a call comes in to attend a customer’s premises due to an electrical fault, it is often difficult to immediately assess the cause of the problem. Typical discussions usually begin with what was happening at the time of the fault, and once user error has been ruled out, a detailed investigation begins.
After excluding insect or water damage, the majority of electrical faults occur due to the initial installer’s failure to properly select and install electrical fixtures according to current standards and regulations.
Therefore, poor design or installation techniques contribute to errors, and it is very important that the installation design is suitable for its intended purpose.
Failures in our wiring systems do not usually occur along the cable, unless it is improperly installed and subject to damage. However, failures usually occur in equipment and/or accessories within the cable connections, where the installer is involved, as shown in Figure 1.
We all know that BS 7671 tells us that connections must be electrically and mechanically sound, but we also know that faults can happen.
It is important to ensure that the terminals are properly torqued, as over- or under-tightening can result in failure of equipment or accessory connections.
For this reason, it is important to follow Regulation 526.3 which states that every connection must be available for inspection, testing and maintenance.
Designers can mitigate the impact of faults. This can be achieved, as shown in Figure 2, by ensuring that our installations are divided into several circuits in accordance with paragraph (i) of Regulation 314.1, to avoid danger and minimize inconvenience in the event of a fault. However, in reality, the designer cannot “eliminate” the possibility of faults completely.
There are also other factors that may lead to electrical failures in our facilities, such as:
• Misuse
• Neglect
• Overuse
• Abuse
These factors can cause failures in well-designed and installed electrical systems and equipment.
We can reduce the risk of breakdowns by ensuring that electrical installations are well looked after and maintained. This may involve a regular maintenance regime, such as a facilities management program, or by carrying out regular inspections and testing.
The process of troubleshooting can seem daunting, especially for newly qualified or apprentice electricians.
But this does not mean that we need to follow a systematic approach, understand electrical circuits, and be proficient in inspection and testing. At all stages of the fault finding process, we need to work safely, and this includes safe working systems such as safe isolation.
Where do we start?
The bug detection process can be broken down into simple steps using the “Who, Where, When, and Why” methodology.
The steps to successfully find an error can be summarized as follows:
1. Identify the problem/symptoms
First we need to determine what is actually happening. It could be as simple as a security device that keeps failing.
Once we have identified the problem, even at this early stage, we can start to formulate the fault in our minds. It is always a good idea to start with the obvious, as there is no point in rushing and dismantling electrical installations if it is not necessary.
2. Gathering information/evidence
At this stage, we can start gathering information and facts. Having a good knowledge of electrical installations and their associated circuits is essential, and this knowledge can come from a number of sources, such as:
• People (you, the client, the designer)
• Manufacturer’s instructions
• Graphs and pie charts
• Circuit diagrams and timelines
• Previous test results
Figure 3 illustrates these points using the EICR model.
3. Evidence analysis
Once we have collected the evidence, we need to analyze it in conjunction with standard tests and visual inspection.
The cause of the fault may become apparent during visual inspection, for example, water entering a piece of electrical equipment.
A standardized test is useful to support any initial suspicions or to compare with previous test results.
4. Interpretation of information and examination and test results
At this stage, we are fully prepared to diagnose the fault based on all evidence and test results.
With the exception of very obvious problems that can be seen during a visual inspection or very complex faults, most faults generally fall into just a few categories, such as:
• Open circuit
• Electrical short circuit
• Ground fault or leakage
• High resistance
• Cross polarity
It is worth noting that you may encounter more than one fault in a particular electrical installation or circuit. However, it is best to identify and fix one fault at a time. This will ensure that you maintain a systematic approach and do not get confused during the fault finding process.
Table 1 is a simplified guide and can be used as a useful basic tool during the error finding process.
What’s next?
5. Error correction
Once we have identified the fault, we are now ready to fix it. This may involve reconnecting part of the circuit, replacing any faulty electrical equipment, or simply tightening loose connections.
6. Conduct functional tests
We need to make sure the bug is fixed. This requires performing basic functional tests, such as powering the equipment on/off.
It would be appropriate to carry out some standard tests, such as continuity, insulation resistance, earth fault loop impedance and possibly RCD tests and record the results to ensure that the circuit is safe for continued use. At this stage, it is also a good idea to show the customer what you initially found (the fault, for example) and what you did to fix it, including photographic evidence.
conclusion
Troubleshooting is a task that most electricians have to do at one time or another. By taking a systematic approach, the task can be less complicated and frustrating than you might think, and in the end, it can be very rewarding.
Although we ideally do not want to encounter faults in our electrical installations, identifying and correcting them provides us with valuable experience and builds problem-solving and fault-finding skills.
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