Power Quality mitigation techniques2.pptx

Mitigation Techniques

1. Power Quality Definitions IEEE Categories Std 1159-1995 Short Duration Variations Typical Duration Instantaneous Sag 0.5 – 30 cycles Momentary Sag 30 cycles – 3 sec Temporary Sag 3 sec – 1 min

2. PQ Definitions IEEE Categories Std 1159-1995 Short Duration Variations Typical Duration Instantaneous Sag 0.5 – 30 cycles Momentary Sag 30 cycles – 3 sec. Temporary Sag 3 sec – 1 min. Instantaneous Swell 0.5 – 30 cycles Momentary Swell 30 cycles – 3 sec. Temporary Swell 3 sec – 1 min.

3. PQ Definitions IEEE Categories Std 1159-1995 Short Duration Variations Typical Duration Instantaneous Sag 0.5 – 30 cycles Momentary Sag 30 cycles – 3 sec. Temporary Sag 3 sec – 1 min. Instantaneous Swell 0.5 – 30 cycles Momentary Swell 30 cycles – 3 sec. Temporary Swell 3 sec – 1 min. Momentary Interruptions 0.5 – 30 cycles Temporary Interruptions 30 cycles – 3 sec.

4. PQ Definitions IEEE Categories Std 1159-1995 Long Duration Variations Typical Duration Sustained interruptions > 1 min Under voltages > 1 min Over voltages > 1 min

5. PQ Definitions IEEE Categories Std 1159-1995 Long Duration Variations Typical Duration Sustained interruptions > 1 min Under voltages > 1 min Over voltages > 1 min Voltage imbalance Steady state Waveform Distortion

6. PQ Definitions IEEE Categories Std 1159-1995 Long Duration Variations Typical Duration Sustained interruptions > 1 min Under voltages > 1 min Over voltages > 1 min Voltage imbalance Steady state Waveform Distortion DC offset Steady state Harmonics Steady state Inter harmonics Steady state For Electric Utilities, Control of Voltage and Prevention of Outages is Power Quality

7. Sources of PQ Problems Utility/Sources Lightning PF Correction Equipment Faults Switching Internal Sources Individual Loads –Lighting, Elevators, Coolers, HVAC Uninterruptible Power Supplies Variable Frequency Drives Battery Chargers Large Motors During Startup Electronic Dimming Systems Lighting Ballasts (esp. Electronic) Arc Welders, and Other Arc Devices Medical Equipment, e.g. MRIs and X-Ray Machines Office Equipment and Computers Wiring

8. PQ Problems and Possible Causes Typical problems Disturbance Type Possible Causes Overheated neutral Intermittent lock-ups Frequency deviations Steady-state Shared neutrals Improper or inadequate wiring High source impedance SCR/Rectifiers and notching Harmonics

9. PQ Problems and Possible Causes Typical problems Disturbance Type Possible Causes Overheated neutral Intermittent lock-ups Frequency deviations Steady-state Shared neutrals Improper or inadequate wiring High source impedance SCR/Rectifiers and notching Harmonics Interruption Garbled data Random increase in harmonics levels Utility faults Inrush currents Inadequate wiring

10. PQ Problems and Possible Causes Typical problems Disturbance Type Possible Causes Overheated neutral Intermittent lock-ups Frequency deviations Steady-state Shared neutrals Improper or inadequate wiring High source impedance SCR/Rectifiers and notching Harmonics Interruption Garbled data Random increase in harmonics levels Utility faults Inrush currents Inadequate wiring Intermittent lock-ups Lights flicker Garbled data Sags/Swell Source voltage variations Inrush/surge currents Inadequate wiring

11. PQ Problems and Possible Causes Typical problems Disturbance Type Possible Causes Overheated neutral Intermittent lock-ups Frequency deviations Steady-state Shared neutrals Improper or inadequate wiring High source impedance SCR/Rectifiers and notching Harmonics Interruption Garbled data Random increase in harmonics levels Utility faults Inrush currents Inadequate wiring Intermittent lock-ups Lights flicker Garbled data Sags/Swell Source voltage variations Inrush/surge currents Inadequate wiring Component failure Dielectric breakdown Garbled data Wavy CRTs Impulses EMI/ RFI Lightning Load switching Capacitor switching Static discharge Hand-held radios Loose wiring/arcing

12. PQ Problems and Possible Causes Typical problems Disturbance Type Possible Causes Overheated neutral Intermittent lock-ups Frequency deviations Steady-state Shared neutrals Improper or inadequate wiring High source impedance SCR/Rectifiers and notching Harmonics Interruption Garbled data Random increase in harmonics levels Utility faults Inrush currents Inadequate wiring Intermittent lock-ups Lights flicker Garbled data Sags/Swell Source voltage variations Inrush/surge currents Inadequate wiring Component failure Dielectric breakdown Lock-ups Garbled data Wavy CRTs Impulses EMI/RFI Lightning Load switching Capacitor switching Static discharge Hand-held radios Loose wiring/arcing Overheated transformers and motors Voltage and current distortions Garbled data Harmonics Electronic loads SCR/rectifier

13. Major PQ Problems Source: EPRI, 1994 Spikes, 7% Sags, 56% Outages, 6% Swells, 31% Sags (Dips) Associated with system faults Switching of heavy loads Starting of large motors Swells System fault conditions Switching on a large capacitor bank Switching off a large load

14. Power Quality Mitigation techniques

15. POWER QUALITY SOLUTIONS Transient Voltage Surge Suppressors (TVSS) By employing TVSS a level of safe value of voltage is reached to electronic load. Filters Noise Filters It can be accomplished by using a combination of capacitors and inductances that creates a low impedance path to the fundamental frequency and high impedance to higher frequencies. Harmonic Filters An LC circuit, tuned to each harmonic order to be filtered, is installed in parallel with the non-linear load This bypass circuit absorbs the harmonics, thus avoiding their flow in the distribution network.

16. Isolation Transformers The main purpose of the isolation transformer is safety and protection of electronic components and the person against electrical shock. STATCOM STATCOM or Static Synchronous Compensator is a power electronic converter using devices like IGBT, GTO etc. to control the reactive power flow through a power network and thereby increasing the stability of power network. STATCOM mean that it can either absorb or generate reactive power in synchronization with the demand to stabilize the voltage of the power network.

17. Dynamic Voltage Restorer DVR is method of injecting voltage in power distribution. DVRs are connected in series with the transmission line. Thyristor -Based Static Switch The static switch is a versatile device for switching a new element into the circuit when voltage support is needed. To correct quickly for voltage spikes, sags, or interruptions, the static switch can be used to switch in one of the following: i ) Capacitor, ii) Filter, iii) Alternate power line, iv) Energy storage system . Static switch can be used in the alternate power line application.

18. Uninterruptible Power Supply (UPS ) UPS systems provide protection in the case of a complete power interruption (blackout). A UPS provides a finite source of electrical power to support selected critical loads during a loss of normal power. This backup time ranges from seconds to hours.

19. Voltage Regulators Voltage regulators maintain output voltage at nominal voltage under all but the most severe input voltage variations. Three basic types of Voltage regulators : Tap Changers: Designed to adjust for varying input voltages by automatically transferring taps on a power transformer. Buck Boost: Utilize similar technology to the tap changers except the transformer is not isolated. Constant Voltage Transformer (CVT): CVT is also known as ferro -resonant transformers. The CVT is a completely static regulator that maintains a nearly constant output voltage during large variations in input voltage .

20. Unified Power Quality Conditioner (UPQC)   The unified power quality conditioner (UPQC) is a custom power device, which mitigates voltage and current-related PQ issues in the power distribution systems. The UPQC employs two voltage source inverters (VSIs) that is connected to a DC energy storage capacitor. A UPQC, combines the operations of a Distribution Static Compensator (DSTATCOM) and Dynamic Voltage Regulator (DVR) together. This combination allows a simultaneous compensation of the load currents and the supply voltages, so that compensated current drawn from the network and the compensated supply voltage delivered to the load are sinusoidal and balanced .

21. Benefits of Continuous PQ Monitoring Continuous PQ Monitoring Detects, Records, and Leads to the Prevention of Power Quality Problems Power Quality monitoring provides a continuous “Health Check” of a facility’s power system … for example: Harmonic interaction between loads and power conditioning equipment spotted High Inrush currents from equipment startup detected Transients from load switching are seen It provides data to see, diagnose and avert looming problems Trends can be detected equipment maintenance programs can be established It acts like a “Black Box” on an airplane to tell you what, when, and where a Power Quality event occurred … to prevent it from reoccurring

22. What is needed for PQ Monitoring? PQ Monitors must detect and record the 7 types of PQ problems Transients Interruptions Sag/Under Voltage Swell/Over Voltage Waveform Distortion Voltage Fluctuations Frequency Variations These include Flicker and Compliance to ITI(CBEMA), IEEE and ISO Standards Plus they must … Be easy to use Be Suitable for continuously monitoring indoors and outdoors Interface with standard PQ analysis Software Be fast enough to capture high speed events that produce equipment problems Have enough storage to save the waveforms you need Have PQ analysis tools that produce usable, actionable recommendations ITI : Information Technology Industry Council (Computer & Business Equipment Manufacturer’s Association)

23. Instantaneous Sag Event

24. Instantaneous Swell Event

25. Harmonic & Interharmonic Spectrum

26. PQ - Evaluation GE Multilin provides the necessary tools for a successful PQ disturbance analysis and allows users to take remedial actions Accurate Measurement to determine actual state Examinations Remedial actions Remedy Feels the pulse of the power system network Symptoms High resolution recordings for longer durations GE Communicator software Diagnosis

27. Real Time Field Recorded Events Source: AGA Brazil Meter: EPM9650 Period: Jan 2005 – Dec 2005 Continuous Monitoring of the Station for PQ Problems