Power Quality
Basics
Presented by
Scott Peele PE
PQ Basics
O
Terms and Definitions
Z
O
O
O
O
O
Surge, Sag, Swell, Momentary, etc.
Measurements
Causes of Events
Possible Mitigation
PQ Tool
Questions
Power Quality Measurement
O
Duration (Time) Cycles
X (.016
seconds per cycle)
150
100
50
0
Z
Seconds, Minutes, Hours
-50
-100
O
Magnitude (Voltage level)
Z
Z
Z
-150
0
Transient level I.e. = 1000 volts
RMS - Voltage level i.e. = 120 volts
Waveforms
X Distortions
Magnitude and Duration
200
Voltage Level
Magnitude
150
120 Volts RMS
100
169 volts
50
0
-50
One Cycle
.01666 seconds
-100
-150
60 Hertz/second
-200
0
Duration
Time
Terms and Definitions
O
O
O
O
O
O
Transient or Surge
Sag
Swell
Interruption
Outage
Harmonics
O
O
O
O
O
O
Magnitude and Duration
Magnitude and Duration
Magnitude and Duration
Magnitude and Duration
Duration
Steadystate Condition
Duration
O
O
O
O
O
O
O
O
O
Transient or Surge Impulse O
Transient or Surge oscillatoryO
O
Sag
O
Swell
Momentary Interruption O
O
Interruption
O
Outage
O
Harmonics
O
Unbalance
.00000005 -- .002 seconds
.000005 -- .050 seconds
.008 -- 60 seconds
.008 -- 60 seconds
.008 -- 3 seconds
3 seconds to 1 Minute
Greater than 1 Minute
Steadystate Condition
Steadystate Condition
What is Power Quality & Reliability?
200
Short Term Event
300
Long Term Event
400
Transient
Surge
Percent of Nominal Voltage
500
Voltage Tolerance Envelope
Applicable to Single-Phase
120- Volt Equipment
SWELL Region
100
SAG Region
0
0.000001
Outage
0.00001
0.0001
0.001
0.01
0.1
Time in Seconds
1
10
100
Interruptions (<10% of Nominal)
What is a Transient or Surge?
O
A Transient can be classified into two
categories, impulsive and oscillatory
Duration < 50 ns to 50 ms
Z .00000005 seconds to .002 seconds
Z .000005 seconds to .050 seconds
Impulsive
O
This is the category that TVSS (Transient
Voltage Surge Suppressor) SPD
equipment is designed to mitigate.
Sources of Transients
O
Lightning
Z
Z
O
Static
Arc Welding
Switching
Z
Z
Z
contactor
relays
SCR’s
Oscillatory (Low Frequency)
Capacitor Bank Switch
Substation Bank
Line Bank
Voltage Sags
Momentary Interruptions
Breaker Tripped
Outage
Causes of Sag, Interruptions
Outages
Simplified Utility System
Transmission @ 115 kV
Transformer
115 kV Substation
Regulator
Distribution @ 23 kV
Feeder
Breaker
480 V
480 V
Customer
Customer
Fuse
Fuse
Transformer
Transformer
480 V
480 V
Customer
Customer
Fuse
23 kV Feeder
Transformer
Fuse
23 kV Feeder
Transformer
Fuse
23 kV Feeder
Fuse
23 kV Feeder
Fuse
Feeder
Breaker
Fuse
Fuse
Fuse
Transformer
Transformer
480 V
480 V
Customer
Customer
Fuse
Fuse
Transformer
Transformer
480 V
480 V
Customer
Customer
Example
Simplified Utility System
Transmission @ 115 kV
Transformer
115 kV Substation
Regulator
Sag
480 V
Customer
Fuse
Fuse
Transformer
Transformer
480 V
480 V
Customer
Customer
Fuse
Fuse
23 kV Feeder
480 V
Fuse
23 kV Feeder
Transformer
Feeder
Breaker
23 kV Feeder
Fuse
Transformer
Customer
Feeder
Breaker
23 kV Feeder
Fuse
Outage
Distribution @ 23 kV
Fuse
Fuse
Fuse
Transformer
Transformer
480 V
480 V
Customer
Customer
Fuse
Fuse
Transformer
Transformer
480 V
480 V
Customer
Customer
Momentary Interruption
Substation Voltages During a Feeder Fault
Feeder
Breaker
Operation
.3 - 2.0 seconds
Quick Trip
Fault
Current
6-12 cycles
Load Current
lockout
Fault
Initiated
35 seconds
15 seconds
13 cycles
27% Cleared on Second
and Third Relay
68% Cleared on First
Quick trip
5% Goes to Lock Out
.3 - 2.0 seconds
Faulted Feeder
100%
6-12 cycles
Voltage
35 seconds
15 seconds
13 cycles
0%
.3 - 2.0 seconds
100%
Voltage
13 cycles
Adjacent Feeder
15 seconds
6-12 cycles
0%
Time
35 seconds
Steadystate Condition
Waveform Distortion
O
O
O
O
O
Harmonics
Interharmonics
Voltage Balance
Overvoltage
Undervoltage
Wave Distortion
Harmonics
Voltage or Current Unbalance =
Maximum Deviation from Average Voltage
Average voltage
EXAMPLE
Measured
Voltages
X 100 (for Percent)
243 Volts RMS
241 Volts RMS 239 Average Volts
233 Volts RMS
6
X 100 = 2.5% voltage unbalance
239
Customized Solutions
200
Short Term Event
300
TVSS or SPD
Line Reactors
Voltage Tolerance
Envelope
Isolation
Transformers
Applicable to Single-Phase
120- Volt Equipment
SWELL
Region
Power
Conditioner
UPS
or CVT
&
Genset
SAG Region
Interruptions
UPS
Outage
100
0
0.000001
0.00001
0.0001
Long Term Event
400
Transient
Surge
Percent of Nominal Voltage
500
0.001
0.01
0.1
Time in Seconds
1
10
100
IEEE 1159-1995
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
1.1.1 Nanosecond
5 n s rise
< 50 n s
1.1.2 Microsecond
1 u s rise
50 n s - 1 m s
1.1.3 Millisecond
0.1 m s rise
>1 m s
1.2 Oscillatory
1.2.1 Low frequency
< 5 k Hz
0.3 - 50 m s
0 - 4 pu
1.2.2 Medium frequency
5 - 500 k Hz
20 u s
0 - 8 pu
5 us
1.2.3 High frequency
0.5 - 5 M Hz
0 - 4 pu
2.0 Short duration variations
2.1 Instantaneous
2.1.1 Sag
0.5 - 30 cycles
0.1 - 0.9 pu
2.1.2 Swell
0.5 - 30 cycles
1.1 - 1.8 pu
2.2 Momentary
2.2.1 Interruption
0.5 cycles - 3 s
< 0.1 pu
2.2.2 Sag
30 cycles - 3 s
0.1 - 0.9 pu
2.2.2 Swell
30 cycles - 3 s
1.1 - 1.4 pu
2.3 Temporary
2.3.1 Interruption
3 s - 1 min
< 0.1 pu
2.3.2 Sag
3 s - 1 min
0.1 - 0.9 pu
2.3.3 Swell
3 s - 1 min
1.1 - 1.2 pu
3.0 Long duration variation
3.1 Interruption, sustained
> 1 min
0.0 pu
3.2 Undervoltage
> 1 min
0.8 - 0.9 pu
3.3 Overvoltage
> 1 min
1.1 - 1.2 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
Power Quality Tool
http://www.progress-energy.com/
http://www.progress-energy.com/custservice/carcig/resourcectr/pq/pqechome.asp
..\WEB\Tool\index.html
PQ Events
Questions?