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Electricity and Power Protection

Electricity and Power Protection. 1. The nature of electricity 2. Calculating an electrical load 3. Power problems explained 4. Power protection solutions 5. Sizing an uninterruptible power supply. The nature of electrical power. Fundamentals of Electricity. What is Voltage?.

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Electricity and Power Protection

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  1. Electricity and Power Protection 1. The nature of electricity 2. Calculating an electrical load 3. Power problems explained 4. Power protection solutions 5. Sizing an uninterruptible power supply

  2. The nature of electrical power

  3. Fundamentals of Electricity

  4. What is Voltage?

  5. Course_id?_lesson1_page1 Page Name: Atoms 3 Slide Type 7: Flash Animation What is Voltage?

  6. Voltage can only exist between 2 points Since voltage is the difference in electric potential energy between two points, it can never be referred to on a single point. This is why a bird can land on high voltage wires and feel no voltage. However, if the bird touches two high voltage wires at the same time, voltage will exist between the two points.

  7. What is Current?

  8. Current must have a path to flow through Almost anything can be a path. If voltage is high enough, electrons will flow. A perfect example of this is air. Under low voltage conditions, air will not allow electrons to move. Under very high voltage conditions, electrons will flow. Lightning is a great example of this.

  9. What is resistance?

  10. Resistance: Conductors v Insulators

  11. Ohm’s Law

  12. Applying Ohms Law

  13. Applying Ohms Law Example 1

  14. Applying Ohm’s Law Answer 1

  15. Applying Ohm’s Law Example 2

  16. Applying Ohm’s Law Answer 2

  17. Applying Ohm’s Law with resistance held constant

  18. Direct Current (DC) Sources

  19. Alternating Current (AC) Sources

  20. Cycle, frequency and period

  21. Peak voltage and root mean square

  22. Course_id?_lesson1_page1 Page Name: Why generate AC power? Slide Type 7: Flash Animation Why generate AC power?

  23. Signal diagram for linear loads Blue = voltage Red = Current Time in seconds In phase AC Power

  24. Calculating an electrical load

  25. AC power calculations for linear loads RMS Voltage RMS Current Time is seconds P = Vrms x Irms Power (watts) = RMS voltage times RMS Current

  26. AC Power Calculations for non linear loads Voltage Current time Phase angle Out of Phase Phase Shift = sideways movement of the current wave due to change in resistance Displacement Factor = Cosine of the phase angle

  27. AC power calculations for non-linear loads Current Distortion of a Non-linear Load Switch Mode Power Supply Voltage time Current Total Harmonic Distortion (THD): Measure of the severity of current distortion caused by Diodes and Transistors Distortion Factor = Fundamental Current total RMS Current

  28. Power factor calculations • Power Factor = Displacement Factor x Distortion Factor • Non-linear loads can cause the current to shift or distort • The shifting or distorting of the current directly effects the power consumed • -The power factor includes all the displacement and distortion the load creates • - Power Factor is used to calculate the power used by the load.

  29. Volt Amps (VA) v. Watts Watts: the amount of power being used for linear loads only Volt-Amps (VA): is the apparent power used by a non-linear load VA = Watts x (1 / Power Factor)

  30. Power factor calculations example 1 VA = Watts x (1 / Power Factor) Example 1: A 9v battery is powering a light bulb. The current measured in the circuit is 2 Amps. How much power does the light bulb use? Note: Watts = V x I (Amps)

  31. Power factor calculations answer 1 VA = Watts x (1 / Power Factor) Example 1: A 9v battery is powering a light bulb. The current measured in the circuit is 2 Amps. How much power does the light bulb use? Answer: A Battery is DC, so the power factor is 1. Note: Watts = V x I (Amps) VA = Watts x (1 / Power Factor) VA = (9 x 2) x (1/1) = 18 VA

  32. Power factor calculations example 2 VA = Watts x (1 / Power Factor) Example 2: A computer system has a 200 Watt power supply. It requires a 120 V RMS supply voltage. The power factor for the system was measured at .7 What is the power consumed by the load?

  33. Power factor calculations answer 2 VA = Watts x (1 / Power Factor) Example 2: A computer system has a 200 Watt power supply. It requires a 120 V RMS supply voltage. The power factor for the system was measured at .7 What is the power consumed by the load? Answer: VA = Watts x (1 / Power Factor) VA = 200 W x (1 / .7) VA = 200 W x (approx. 1.4) = 280 VA

  34. Power Problems

  35. Why is power a concern? • Power problems 15x more prevalent than a viruses • Power problems largest single cause of downtime and data loss • 42% of companies estimate downtime cost > $1000 or more per hour (Yankee Group) • Power quality may continue to decline because of utility deregulation

  36. Spike Surge • 132 VAC Safe • 115 VAC Operating Range • 103 VAC Brownout Blackout Types of Power Problems

  37. AC power problems • RMS Voltage rises (over 132V RMS) • Sags: RMS Voltage drops (under 92V RMS) • Spikes: Peak voltage is too high (over 200 V) • Blackouts: No Voltage is present • Frequency Drift: Cycles per second drifts away from 60Hz •  Harmonic Distortion: Created by loads which draw power inconsistently

  38. Power Problems • Surges • Definition:Short term increases in voltage, usually lasting at least 1/120 of a second • Cause:High powered electrical motors are switched off and extra voltage is dissipated • Effects:Stresses delicate components, premature failure of power supplies, and catastrophic damage

  39. Power Problems • Spikes (Impulses) • Definition:Instantaneous, dramatic increases or decreases in voltages • Cause:Nearby lightning strike • Effect:Catastrophic damage to computer hardware which will include loss of data

  40. Power Problems • Brownouts (Sags) • Definition:Decreases in voltage levels • Causes:Supply vs. demand of electricity in area • Effects:Frozen keyboards, unexpected system crashes, loss of efficiency and reduced life span of electrical equipment

  41. Power Problems • Blackouts • Definition:Total loss of utility power • Causes:Excess demand on power grid, lightning storms, ice storms, construction • Effects:Loss of current work in RAM or cache; Possible loss of hard drive FAT, resulting in loss of data stored on the hard drive

  42. Power Problems Frequency Source: Bell Labs All surge protectors only protect against 8% of power problems

  43. Frequency Drift 1/60 second (period) Frequency drift: Cycle per second drifts away from 60 HZ

  44. Harmonic Distortion Voltage time Current Total Harmonic Distortion (THD): Measure of the severity of current distortion caused by Diodes and Transistors Distortion Factor: Fundamental Current total RMS Current

  45. Power Protection Solutions

  46. Surge protector • Only protects against surges and spikes • Does not protect against sags, brownouts and blackouts • Used to protect power and/or data lines

  47. Stand-by UPS • Extremely high power efficiency, Typically above 97%. • Little heat is generated and battery lifetime is approximately twice that of the on-line UPS • Very quiet operation and the highest MTBF (mean-time-between failure) due to the lowest voltage, current and temperature of its internal parts. • Simple design and low number of components results in a low purchase price and low maintenance costs. • The switchover time of a high-quality standby UPSs is less than 1mS, quick enough to guarantee glitch-free transfers.

  48. Line Interactive UPS • A Stand-by UPS with additional line conditioning • Utility power is fed directly to the critical load through an inductor or transformer • Copes with a wider range of voltage input without switching to battery • Prolongs the life of the battery. • Offers the same high efficiency and low cost as the basic Stand-by UPS

  49. On-Line UPS • Utility power is converted to DC by a rectifier/charger and converted back to clean AC by the inverter. • During power failure the inverter draws DC power from the battery. No form of detection or switching is required. • On-line UPS provides a superior voltage regulation and line conditioning • Cost is approx 3 times a Stand by UPS. For most point of use applications Stand by is recognized as a more than adequate solution • On-line is more common when used in conjunction with a diesel generator or for extremely mission critical applications.

  50. Power Array A Power Array is an N+1 redundant UPS configuration. Power modules can be added for redundancy and to scale the UPS.

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