Electrical safety
Electrical hazards
- Joule heating of human tissue
- Involuntary muscle contractions
- Ventricular Fibrillation
Resistance of Humans
- Ranges from 100\Omega to 1M\Omega
- Equivalent circuits for humans
Heart stoppage
Source: El-Sharkawi, Electric
Energy
Step potentials
- Large currents flowing to ground can create hazardous voltage
differences along the ground
- If the potential difference across a persons stride is high enough,
a shock can occur
Step potentials
Source: El-Sharkawi, Electric
Energy
Step potentials
Source: El-Sharkawi, Electric
Energy
Step potentials
Source: El-Sharkawi, Electric
Energy
Ground Fault Circuit
Interruptor (GFCI)
- A ground fault circuit interruptor monitors the difference in
current between the hot and neutral lines
- If the current is unequal, that means that another conductor is
carrying current to ground, which is a hazardous situation.
- If Kirchoff’s current law is violated, something unsafe might be
happening.
Ground Fault Circuit
Interruptor (GFCI)
![](./figures_static/GFCI_Receptacle.jpg)
Ground Fault Circuit
Interruptor (GFCI)
![](./figures_static/GFCI.jpg)
Fire Risk
- The earth is a ground in our grid, so trees can complete a
circuit
- If a tree completes the circuit, current flows through the tree
- The electrical potential energy is converted to thermal energy
- Thermal energy can lead to temperatures high enough for
ignition
Fire Ignition Diagram
Fire Circuit