Simulath · Worksheet 5/5

Fault-finding step by step

Level 2 · Installation · Inspection and testing
Goal: Apply an orderly, safe method to locate faults.

Scan: weekly challenge

Name:Group:Date:

1 Observe · 2 Hypotheses from the diagram · 3 Measure safely from the supply to the load · 4 Isolate, verify and confirm · 5 Repair, test and record

Exercises

Which device operates in each case? a) short circuit; b) overload; c) earth leakage.
With the switch closed: 230 V between its input and neutral; 0 V between its output and neutral. Where is the fault?
An incandescent lamp is off with S1 closed: both terminals read 230 V to earth and 0 V between them. What is wrong?
With the switch closed you read 230 V across the lamp terminals and it does not light. Cause?
An insulation test on a domestic circuit (500 V DC) gives 0.2 MΩ. Is it acceptable?
Fault challenge: scan the QR code, solve this week's challenge and explain in your own words why you rule out the other options.

Simulath · Worksheet 5/5 · Answer key (for the teacher)

Scan: weekly challenge

Which device operates in each case? a) short circuit; b) overload; c) earth leakage.
a) MCB, magnetic part (instant). b) MCB, thermal part (delayed). c) RCD.
With the switch closed: 230 V between its input and neutral; 0 V between its output and neutral. Where is the fault?
In the switch: it does not make contact (open circuit between its input and output).
An incandescent lamp is off with S1 closed: both terminals read 230 V to earth and 0 V between them. What is wrong?
The neutral is broken between the lamp and the box: the line passes through the lamp and there is no return path.
With the switch closed you read 230 V across the lamp terminals and it does not light. Cause?
The lamp is blown or badly seated in the lampholder (the open point is in the lamp itself).
An insulation test on a domestic circuit (500 V DC) gives 0.2 MΩ. Is it acceptable?
No. Spain's ITC-BT-19 requires at least 0.5 MΩ for installations up to 500 V (check your local code). Find the fault.
Fault challenge: scan the QR code, solve this week's challenge and explain in your own words why you rule out the other options.
Open answer. Reward learners who use the measurements to rule out hypotheses rather than guessing.

Solve this week's fault challenge: simulath.com/en/challenge/

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