Home electrical panel – main breaker, branch circuits and shock protection
Design & TechnologyElectrical Engineering & SafetyAges 17–18
Use it with your class: students open it from a link or a QR code, with no account needed.
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The home's electrical panel has a main circuit breaker, a residual-current circuit breaker (RCCB, 30 mA) and branch breakers feeding lighting, sockets, air conditioning, the water heater and the electric stove. Click a branch to switch it on or off and see the current I = P/(U·cosφ) for that branch and for the whole house; click a fault button to trigger an overload, a short circuit or a leakage current through a person, and see which breaker trips first. Click Reset all to restore power.
Lesson: Structure of the home electrical network and its switching and protection devices: main breaker, branch breakers, residual-current breaker
What it shows
A home electrical panel splits the supply into branch circuits, each protected by its own breaker, downstream of a main breaker and a residual-current circuit breaker (RCCB). Breakers respond to current: a moderate overload trips a branch breaker after a short delay, a short circuit trips it at once, and the main breaker trips only when the total current exceeds its rating. A person touching a live casing draws only tens of milliamps, far too little for any breaker to notice, but the RCCB detects an imbalance of more than 30 mA between the line and neutral currents and disconnects within 0.1 s.
How to use
Click branches in the panel diagram to switch appliances on and watch the total current approach the main breaker's rating. Select one branch, then use Trigger overload and Short-circuit and note which breaker trips and how quickly. Click Touch casing (leakage) with RCCB: yes, then set RCCB: no and repeat. Raise the Load slider to see when the whole house loses power, and click Reset all between trials.
Parameters you can change
- Number of branches in the panel 3–5 branches
- Load level of each branch 40–200 %
- Main breaker rated current 20–63 A
- Simulated fault No fault, Branch overload (plugging in a high-power device), Short circuit (line wire touching the neutral wire), Leakage current through a person touching a device casing
- RCCB (30 mA residual-current breaker) installed
Questions to explore
- Why can a branch breaker not protect a person touching a live casing, while the RCCB can?
- When one branch is short-circuited, which breaker trips first, and why do the other branches keep their power?
- With all five branches on at 100 % load, what main breaker rating is needed to avoid tripping?
