In Power Quality troubleshooting, voltage disturbances are critical factors.

The ability to identify the characteristics and analyze the disturbance is key to the appropriate power quality solution to be deployed. Most often referred as surge (transient overvoltage), while they are not.

Today, we shall explain, basically what surges (transient overvoltages) are and what they are not.

Surges (transient overvoltages)

Surges (transient overvoltages) are short duration increase in voltage measured between two or more conductors.

This increase to voltages vary from a few to thousands of volts and its duration from microseconds (millionths of a second) to a few milliseconds (thousandths of a second). Spikes, glitches and transients are also referred to as surges.

These voltages occur between two or more conductors.

For a mains power supply, these conductors would be the live/phase, neutral and earth wires.

What surges (transient overvoltages) are not?

Surges (transient overvoltages) are by definition a very specific form of disturbance. We therefore outline other forms of voltage disturbances in order to understand what surges are not.

Most of these disturbances can be represented as an aberration to the normal mains power supply as shown below

‘Outage’, ‘power cut’ and ‘blackout’ are all terms applied to total break in the supply lasting from several milliseconds to many hours. Very short breaks, which cause lights to flicker, may be sufficient to crash computers and other sensitive electronic equipment.

‘Undervoltages’ or ‘brownouts’ are sustained reductions in the supply voltage, lasting anything from a few seconds.

‘Overvoltages’ are sustained increases in the supply voltage, lasting anything over a few seconds.

‘Sags’ or ‘dips’ are decreases in the supply voltage, lasting anything over a few seconds.

‘Swells’ (also called ‘surges’) are increases in the supply voltage, lasting no more than a few seconds.

Electrical noise or radio frequency interference (RFI), is a continuous high frequency (5kHz or more) distortion of the normal sine wave.

Harmonics are a continuous distortion of the normal sine wave, at frequencies of up to 3kHz.

Nuclear Electromagnetic Pulse (NEMP), or Electromagnetic Pulses (EMP), are pulses of energy caused by nuclear explosions and intense solar activity. NEMP or EMP transients are much quicker (a faster rise time) than commonly occurring transients.

Electrostatic discharge (ESD) is something of a different phenomenon. Unlike the above it does not tend to be transmitted on power or data lines. An electrostatic charge is generated by two insulating objects being rubbed together. A charged object will discharge when it comes into contact with a conducting object. A common example of the charging mechanism could be someone walking over a synthetic carpet. The discharge would occur when the electrically charged person touches a door handle or computer keyboard.

Electromagnetic Interference (EMI) is a very board term referring to system interference.

Electromagnetic compatibility (EMC) is a philosophy referring to attempts to prevent EMI. EMC practice dictates that potential sources of interference are designed so as not to affect equipment, and that potential victim equipment is designed to be immune from potential source of interference. Lightning cannot be prevented at source, and cannot be fully protected against with simple EMC counter measures.







Enquiries

Victor Oyedu, FNSE, FNIEEE, CPQ.
Power Quality and Energy Management Specialist.
Publisher at Afrienergyonline.com &
CEO, FullSpectrum Energy Solutions Limited, Nigeria.