Electrical noise is unwanted high-frequency oscillations generated in the electrical system. The electrical noise distorts the fundamental voltage and current waveforms, resulting in power quality issues. The poor power quality causes:

  • Permanent damage to the sensitive electronics loads 
  • Malfunction and erratic behavior of computerized loads
  • Increased maintenance and energy usage of the loads
Damage from noise
Noise causing damage to the load

Internally generated noises is about 70-85%, while the externally generated noises is about 15-30%

The electrical noise is classified into two categories based on its origin of generation 1) external and 2) internal.

Internally generated noises constitute about 70-85% of the total transients in a facility. The sources of the internally generated transients are: 

  1. Load switching 
  2. Nonlinear load behavior such and VFDs and PLC 
  3. AC-DC power conversion 
  4. Starting and stopping loads 
  5. Arcing faults (ground) 
  6. Discharge of inductive loads such as transformers, motors 
  7. Contactors, relays, and circuit breaker operation
Loads adding internally generated noise to the system
Lightning is an example of externally generated noise

Externally generated noises remain at 15-30% of the transients. The sources of externally generated surges are: 

  1. Lightning – both direct and indirect hits 
  2. Utility initiated grid and capacitor switching 

Again, the internally generated noise is 85%, while the externally generated noise is 15%. Learn more about the switching noise from the nonlinear loads here.