Understanding power quality issues

Voltage dip

A voltage dip occurs when the supply voltage drops below 90% of the standard voltage. Most voltage dips last for around 0.1 sec.

During a voltage dip, the power supply is not interrupted. 

When there is a voltage dip: 

• Customers' light may dim or flicker;
• Customers' lift may trip; and
• Sensitive equipment may be affected.

Harmonic distortion

Harmonic distortions occur when current waveforms deviate from their fundamental frequency.

Harmonic distortions may result in: 

• Overheating of cables, transformers, and motors;
• Unstable operations of circuit breakers and relays; and
• Extra power consumption.

Intrinsic factors 

(Caused by customer’s system or equipment)

• Switching of large power equipment (e.g. large motors)
• Improper wiring and grounding
• Overloaded circuits or harmonic interference

External factors 

(Not caused by customer’s system or equipment)

• Adverse weather conditions
• Vegetation, animals, etc.
• Equipment failure
• Third party damage