How is electricity transmitted?
Electricity is generated by electromagnetic induction. Commercial electricity is a silent and seemingly inexhaustible source of energy provided in the form of alternating current (AC), generated by power plants, stepped up by transformers, and transmitted hundreds of kilometers to electrical equipment. Understanding the role of electricity in a short period of time helps us understand how important simple and stable alternating current is for the stable operation of the precision systems we rely on. Through an oscilloscope, we can see the waveform of electrical energy. In an ideal environment, commercial AC power is displayed as a smooth and symmetrical sine wave (the sine waveform represents the voltage change from positive to negative), which varies by 50 or 60 cycles per second (i.e. 50 or 60 Hz) depending on your location. The APC UPS output is a stable 60Hz sine wave.
When the size, shape, symmetry, frequency of this flowing waveform changes or there are gaps, pulses, oscillations, or drops to zero (but temporarily), these are power disturbances. We will expand on the seven types of power quality disturbances discussed in this article through simple graphical variations of the ideal sine wave mentioned above.
As mentioned, the use of power disturbance terminology is ambiguous throughout the entire power industry and business community. For example, according to a study, “surge” means an instantaneous increase in voltage, usually caused by heavy load disconnection. On the other hand, ‘surge’ refers to a transient voltage with extremely high peak values ranging from microseconds to milliseconds in duration. The latter is usually associated with lightning strikes and momentary discharges or arc discharges generated by contact switches. We often use the following vague terms to express power issues: dimming/brightening/power surges/surges/interruptions/flicker/grid pollution/frequency offset/interference/spikes/instantaneous flicker.
For example, if one can effectively understand electricity, such as the difference between interruptions and transient oscillations, then the decision to purchase power correction equipment may be completely different. If improper power calibration equipment is purchased, this error may lead to serious consequences, including downtime, financial losses, and even equipment damage. The listed power quality disturbances are usually classified into categories based on waveform:
1. Transient phenomena (① transient pulses; ② transient oscillations)
2. Waveform distortion (① noise; ② harmonics; ③ interharmonic waves; ④ DC bias; glitches;)
3. Voltage fluctuations
4. Frequency jitter
5. Voltage sag/undervoltage
6. Voltage transient rise/overvoltage
7. Interruption