Unit 01 – Introduction to Power Quality
Syllabus: Terms and definition of transients.
Long duration voltage variations: Under voltage, Under voltage and sustained interruptions.
Short duration voltage variations: sag, swell.
Voltage Imbalance,
Waveform distortion: dc offset, Harmonics, Inter-harmonics, Notching, Noise.
Voltage fluctuation, Power frequency variation.
What is Power..
The ability of doing work is called as Power.
Or
The ability to do something in a particular way is called Power.
According to Mathematical Expression, it is defined as Rate of doing Work or the Work done with respect to time.
What is Quality..
- Quality defines features and characteristics of any quantity and defines its ability that whether it will satisfy the requirement or not.
- For Example, Quality of Voltage or Current defines whether the it will make the equipment work efficiently or will damage the equipment.
Power Quality..
- It is an abnormal behavior on a power system, arises in the form of voltage and current, which affects the normal operation of electrical and electronic equipment.
- Any power problem manifested in voltage, current or frequency deviation that results in failure or miss-operation of customer equipment.
- It also refers to the ability of electrical equipment to consume the energy being supplied to it.
Good Power Quality:
- A good Power Quality have voltage and current in constant sine wave shape with constant fundamental frequency and constant RMS values.
- It should form a symmetrical power system and should not get affected by the load changes.
Reason of Power Quality Issues:
- Connection and Disconnection of Large Load, specially inductive load, affects the supplied power as the Inductive load consumes active and reactive power which decreases or affects the supplied voltage.
- Atmospheric Phenomena like Lightning strikes on power devices, transmission or distribution system, creates a huge amount of current to flow which can damage the home appliances and other equipment.
- Interruption of power supply for few minutes, caused by generation or transmission plant failure, transmission or distribution line fault or load shedding (disconnection of load) during system overloading creates power quality issue.
- Decrease in Voltage by failure of tap changing or short time voltage disturbance due to starting and shutting down of large motor creates power quality issue.
Example of Power Quality Issues:
- AC power system design to operate at a sinusoidal voltage of a given frequency and magnitude. Any significant deviation in the waveform, magnitude, frequency, purity in a potential create power quality problem.
- Ex: The current resulting from a short circuit causes the voltage to sag or disappear completely, as the case may be the current from lightning stocks passing through the power system cause high impulse voltage that frequently flashover insulation and leads to other phenomena such as short circuit.
- Distorted current from harmonics producing loss, also demolish the actual voltage as they pass through the system impedance. Thus, a distorted voltage will be presented or passed to other end users.
- Poor Power Quality increases the Power consumption by equipment which is not good as it leads the consumer to pay more money for the electricity.
- It can reduce the productivity in business and can damage sensitive equipment and can effect the efficiency.
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