Power Quality Basics. Presented by. Scott Peele PE

Transcription

1 Power Quality Basics Presented by Scott Peele PE

2 PQ Basics Terms and Definitions Surge, Sag, Swell, Momentary, etc. Measurements Causes of Events Possible Mitigation PQ Tool Questions

3 Power Quality Measurement Duration (Time) Cycles (.016 seconds per cycle) 50 Seconds, Minutes, Hours Magnitude (Voltage level) Transient level I.e. = 1000 volts RMS - Voltage level i.e. = 120 volts Waveforms Distortions

4 Magnitude and Duration 200 Magnitude Voltage Level volts 60 Hertz/second 120 Volts RMS One Cycle seconds Duration Time

5 Terms and Definitions Transient or Surge Sag Swell Interruption Outage Harmonics Magnitude and Duration Magnitude and Duration Magnitude and Duration Magnitude and Duration Duration Steadystate Condition

6 Duration Transient or Surge Impulse Transient or Surge oscillatory seconds seconds Sag seconds Swell seconds Momentary Interruption seconds Interruption 3 seconds to 1 Minute Outage Greater than 1 Minute Harmonics Steadystate Condition Unbalance Steadystate Condition

7 What is Power Quality & Reliability? 500 Percent of Nominal Voltage Voltage Tolerance Envelope Applicable to Single-Phase 120- Volt Equipment Transient Surge Short Term Event SWELL Region Long Term Event SAG Region 0 Outage Time in Seconds Interruptions (<10% of Nominal)

8 What is a Transient or Surge? A Transient can be classified into two categories, impulsive and oscillatory Duration < 50 ns to 50 ms seconds to.002 seconds seconds to.050 seconds

9 Impulsive This is the category that TVSS (Transient Voltage Surge Suppressor) SPD equipment is designed to mitigate.

10 Sources of Transients Lightning Static Arc Welding Switching contactor relays SCR s

11 Oscillatory (Low Frequency)

12 Capacitor Bank Switch Substation Bank Line Bank

13 Voltage Sags

14 Momentary Interruptions Breaker Tripped

15 Outage

16 Causes of Sag, Interruptions Outages

17 Simplified Utility System 115 kv Regulator 23 kv 115 kv Substation Feeder Breaker Feeder Breaker 23 kv Feeder 23 kv Feeder 23 kv Feeder 23 kv Feeder

18 Example

19 Simplified Utility System 115 kv Sag Regulator Feeder Breaker 23 kv 115 kv Substation Feeder Breaker Outage 23 kv Feeder 23 kv Feeder 23 kv Feeder 23 kv Feeder Momentary Interruption

20 Substation Voltages During a Feeder Fault Feeder Breaker Operation Fault Current Quick Trip 6-12 cycles seconds Load Current lockout 13 cycles 15 seconds 35 seconds Fault Initiated 68% Cleared on First Quick trip 27% Cleared on Second and Third Relay 5% Goes to Lock Out Faulted Feeder seconds 100% Voltage 6-12 cycles 0% 13 cycles 15 seconds 35 seconds seconds 100% Adjacent Feeder 13 cycles 15 seconds 35 seconds Voltage 6-12 cycles 0% Time

21 Steadystate Condition Waveform Distortion Harmonics Interharmonics Voltage Balance Overvoltage Undervoltage

22 Wave Distortion

23 Harmonics

24 Voltage or Current Unbalance = Maximum Deviation from Average Voltage Average voltage X 100 (for Percent) EXAMPLE Measured Voltages 243 Volts RMS 241 Volts RMS 233 Volts RMS 239 Average Volts X 100 = 2.5% voltage unbalance

25 Customized Solutions 500 Percent of Nominal Voltage Voltage Tolerance Envelope Applicable to Single-Phase 120- Volt Equipment Transient Surge TVSS or SPD Line Reactors Isolation s Power SWELL Conditioner Region 0 Interruptions Outage Short Term Event or CVT SAG Region UPS Long Term Event UPS & Genset Time in Seconds

26 IEEE Recommended Practice For Monitoring Electric Power Quality Table 2 Categories and typical characteristics of power system electromagnetic phenomena Categories Typical Spectral Typical Duration Typical Voltage Content Magnitude 1.0 Transient 1.1 Impulsive Nanosecond 5 n s rise < 50 ns Microsecond 1 u s rise 50 n s - 1 m s Millisecond 0.1 m s rise >1 m s 1.2 Oscillatory Low frequency < 5 k Hz m s 0-4 pu Medium frequency k Hz 20 u s 0-8 pu High frequency M Hz 5 u s 0-4 pu 2.0 Short duration variations 2.1 Instantaneous Sag cycles pu Swell cycles pu 2.2 Momentary Interruption 0.5 cycles - 3 s < 0.1 pu Sag 30 cycles - 3 s pu Swell 30 cycles - 3 s pu 2.3 Temporary Interruption 3 s - 1 min < 0.1 pu Sag 3 s - 1 min pu Swell 3 s - 1 min pu 3.0 Long duration variation 3.1 Interruption, sustained > 1 min 0.0 pu 3.2 Undervoltage > 1 min pu 3.3 Overvoltage > 1 min pu 4.0 Voltage imbalance steady state 0.5-2% 5.0 Waveform distortion 5.1 DC offset steady state 0-0.1% 5.2 Harmonics 0-100th H steady state 0-20% 5.3 Interharmonics 0-6 k Hz steady state 0-2% 5.4 Notching steady state 5.5 Noise broad-band steady state 0-1% 6.0 Voltage fluctuations < 25 Hz intermittent 0.1-7% 7.0 Power frequency variations < 10 s

27 Power Quality Tool

28 PQ Events Questions?