Power quality disturbances

Seminar topic on Power quality disturbances .
It gives a fundamental idea of this topic.

1. SEMINAR ON POWER QUALITY DISTURBANCES ELECTRICAL ENGINEERING Guided By :- Dr. Bhagabat Panda Presented By :- Manas Kumar Patro Regd No. – 1501109287 Mahesh Panigrahi Regd No. - 1501109286

2. CONTENTS :- Introduction to Power Quality Power Quality Definition Causes Of Power Quality Problems Power Quality Disturbances Solutions For Power Quality Problems Conclusion References

3. INTRODUCTION :- The aim of power system is to supply electrical energy or power to customers. Non linear loads, utility switching and fault clearing produce disturbances that affect the quality of this delivered power. Power quality means the quality of the normal voltage supplied to our homes, factories, etc. It is based on the extent of variation of the voltage and current waveforms from the ideal pure sinusoidal waveforms of fundamental frequency.

4. POWER QUALITY DEFINITION Power Quality is the set of parameters defining the properties of the power supply as delivered to the user in normal operating conditions , in terms of the continuity of voltage and voltage characteristics. As per IEEE 100 Authoritative Dictionary of IEEE Standard Terms, Power Quality is defined as `The concept of powering and grounding electronic equipment in a manner that is suitable to the operation of that equipment and compatible with the premise wiring system and other connected equipments’.

5. CAUSES OF POWER QUALITY PROBLEMS Difficult to point an exact cause for a specific problem. Power quality problems are broadly classified as two categories : 1.Internal Causes 2.External Causes

6. 1.Internal causes i )About 80% of Power Quality problems originate within a business facility. ii)Due to large equipments start or shut down, improper wiring and grounding, overloaded circuits or harmonics. 2.External causes i )About 20% of Power Quality problems originate within the utility transmission and distribution system. ii)Due to lightning strikes, equipments failure , weather conditions etc.

7. POWER QUALITY DISTURBANCES:- Power Quality disturbances can be divided into 2 basic categories: 1.Steady-state variations 2.Events 1.Steady-state variations:-Small deviations from the desired voltage or current values. i )voltage fluctuations ii)voltage unbalance iii)harmonic distortion iv)high frequency voltage noise

8. 2.Events:-Significant sudden deviations of voltage or current from the nominal or ideal wave shape. i )interruptions ii)voltage sag iii)voltage swell iv)transients

9. 1.i) VOLTAGE FLUCTUATION Due to variations of total load of a distribution system, action of transformer tap changers, switching of capacitor banks, etc. If the variations are large enough or in a certain critical frequency range, it can affect the performance of the equipment. Fig.:-Voltage Fluctuation

10. 1. ) VOLTAGE UNBALANCE A voltage variation in a three-phase system in which the three voltage magnitudes or the phase angle differences between them are not equal. Causes: Large single-phase loads, incorrect distribution of all single-phase loads by the three phases of the system. Consequences: The most affected loads are three-phase induction machines. 1.iii) HARMONIC DISTORTION Non-fundamental frequency components are called harmonics. Deviation of voltage and current waveforms from the ideal pure sinusoidal waveforms of fundamental frequency. Causes: Classic sources Modern Sources

11. 1.iv) HIGH FREQUENCY VOLTAGE NOISE Non periodic high frequency components in supply voltage. Caused mainly due to arc welding or operation of electrical motor. Analysis needed only if it leads to some problem with power system or end user equipments. .

12. 2.i) INTERRUPTIONS Supply interruption occurs when voltage at supply terminals is close to zero. Normally initiated by faults which subsequently trigger protection measures. Based on the duration, interruptions are subdivided into: 1. Sustained interruptions 2. Temporary interruptions 3. Momentary interruptions 2.ii) VOLTAGE SAG Decrease in the RMS value of the voltage, ranging from a half cycle to few seconds(less than 1 minute).

13. Cont.…. Referred to as ‘under voltage’, if continues for longer duration. Causes: 1)Faults on the transmission or distribution networks. 2)Connection of heavy loads. Consequences: 1)Malfunction of microprocessor base control systems. 2)Loss of efficiency in electrical rotating machines. 2.iii) VOLTAGE SWELL Momentary increase of the voltage, at the power frequency, outside the normal tolerances with duration of more than 1 cycle, and typically less than 1 minute.

14. VOLTAGE SWELL(cont.): Referred to as ‘over voltage', if continues for longer duration. Causes: 1)Start and stop of heavy loads. 2)poorly regulated transformers Consequences: 1)Flickering of lighting and screens. 2)Damage of sensitive equipments .

15. 2.iv)TRANSIENTS Sub cycle disturbances of very short duration that vary greatly in magnitude. Mainly subdivided into: 1)Impulsive transient, where there is a large deviation of the waveform for a very short duration in one direction, followed possibly by a couple of smaller transients in both directions. 2)Oscillatory transient, where there is a ringing signal or oscillation following the initial transient.

16. Solutions For Power Quality Problems

17. Grid Adequacy Distributed Resources – Energy Storage Systems Distributed Resources – Distributed Generation Enhanced Interface Devices Develop Codes and Standards

18. 1.Distributed Generation The most common solution is the combination of electrochemical batteries UPS and a diesel genset. At present, the integration of a flywheel and a diesel genset in a single unit is also becoming a popular solution, offered by many manufacturers.

19. 2.Distributed Resources – Energy Storage Systems Restoring technologies Energy storage systems, also known as restoring technologies, are used to provide the electric loads with ride-through capability in poor PQ environment Flywheels Electromechanical device that couples a rotating electric machine(motor/generator) with a rotating mass to store energy for short durations.

20. Super capacitors New technology applied to capacitors • High power density • Long life and non-toxic Superconducting Magnetic Energy Storage (SMES) Energy is stored in the magnetic field of a coil made of superconductor material. • High power density • Very fast response • Very expensive (on development)

21. 3.Codes and Standards Need to regulate: • the minimum PQ level that utilities have to provide to consumers, and • the immunity level that equipment should have. 4.Enhanced Interface Devices Dynamic Voltage Restorer Transient Voltage Surge suppressors (TVSS) Noise Filters Static VAR Compensators Harmonic Filters 5.Make End-use Devices Less Sensitive Some measures to increase equipment immunity: -Add a capacitor with larger capacity to power supplies – Use cables with larger neutral conductors

22. Conclusion The availability of electric power with high quality is crucial for the running of the modern society. If some sectors are satisfied with the quality of the power provided by utilities, some others are more demanding . To avoid the huge losses related to PQ problems, the most demanding consumers must take action to prevent the problems. Among the various measures, selection of less sensitive equipment can play an important role. When even the most robust equipment is affected, then other measures must be taken, such as installation of restoring technologies, distributed generation or an interface device to avoid PQ problems.

23. References Roger C. Dugan , Surya Santoso , H. Wayne Beaty and MARK F. McGRANGHAN.(2013).Electrical Power Systems Quality.3 rd edition McGraw-Hill Education. ALEXANDER KUSKO and MARC.C.THOMPSON.(2007).Power Quality in Electrical Systems .New York : Mc Graw-Hill. D.SAXENA,K.S.VERMA and S.N.SINGH.(2010).Power Quality Even Classification : an Overview and Key Issues . International Journal of Engineering , Science and Technology.2(3),pp.186-199. ALEXANDER KUSKO and MARC.C.THOMPSON.(2007).Power Quality in Electrical Systems . New York : Mc Graw-Hill. M. Bollen , “Understanding Power Quality Problems – Voltage Sags and Interruptions”, IEEE Press Series on Power Engineering – John Wiley and Sons, Piscataway, USA (2000).

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