Voltage Sag Protection

Transcription

T-68 Protecting Your Equipment through
Power Quality Solutions
Dr. Bill Brumsickle
Vice President, Engineering
Nov. 7-8, 2012
Copyright © 2012 Rockwell Automation, Inc. All rights reserved.
Agenda
What is Power Quality?
Importance of Power Quality to Industrial Users
Power Quality Events & Voltage Sags
2
Power Quality vs. Power Reliability
 Power Reliability: Continuity of electric power delivery measured by the number and
duration of power outages (Zero voltage)
 Outages are tracked by Utilities
 Power Reliability can be as high as 99.999% availability
 Power Quality: Related to fluctuations in electricity, such as momentary interruptions,
voltage sags or swells, flickering lights, transients, harmonic distortion and electrical noise
 Fewer such incidents indicate greater power quality
 Events go mostly untracked by Utilities
 Sag & Momentary events can take out a process as many as 20-30 times per year
The Grid is designed for Reliability, not Quality…
3
Power Quality
 Frequency is regional
 Determined by HV & EHV network generators
 Problems are rare
 Voltage is area-wide
 Determined by MV distribution network
 Problems occur randomly, but with regularity
 Current is local
 Determined by facility loads
 Problem loads can be identified and resolved
Source: DTE Energy website
4
Utility Power – Properties of AC Grid
 Not always ideal sinusoidal voltages!
 Highly interconnected
 Transformer and line impedances between
generators and loads
 Terminal voltage drops with load current
 System faults cause significant voltage sags (dips)
 Most wiring is overhead
 Susceptible to lightning, animals, wind-blown
tree branches, etc.
Source: NPR: Power Hungry: Reinventing The U.S. Electric Grid May 1, 2009
 Insulation fails, equipment fails
5
Power Quality Problems
 All have physical causes
6
Agenda
7
Electrical Equipment Designed Assuming
Power Quality
 Operate with input ac voltage variation of 10%
 Possible new requirements:
Operate through some voltage sags
 SEMI F47
 IEC
 Present a ‘unity’ Power Factor:
 Current phase angle near zero
 Current harmonic distortion low

8
Impact of Power Quality Events
 Possible Agency, Utility, or Facility Requirements


Power Factor correction (current phase angle)
Harmonic current limits
 Load equipment mis-operation




Voltage sags and momentary interruptions
Voltage distortion (harmonics, notching)
Voltage imbalance or single-phasing
High-frequency voltage transients
 Load equipment damage


High-voltage transients
Current inrush following voltage sag
 Facility infrastructure damage



High-voltage transients
Current inrush following voltage sag
Overheating due to current harmonics
9
Consumer is Responsible for Power
Quality
 Utility cannot provide perfect power quality and are not
required to. (e.g., Wisconsin PSC 113.0703)

Customers having equipment or operations that are sensitive to such voltage
fluctuations … may find it necessary to install, at their own expense, power
conditioning equipment or other modifications …
 Job is to “Keep the lights on.”
 Goals






Deliver maximum energy through the existing infrastructure
Maintain +/-10% (on average) voltage at service entrance
Minimize outages longer than 2-5 minutes
60.00 Hz, when averaged over 24 hours
Keep large industrial customers satisfied
Minimize large customers disrupting neighbors’ power quality
The utility is responsible for reliability, not quality of power….the customer is
responsible for protecting their sensitive equipment at their own expense
10
Agenda
11
Power Quality Issues
 Voltage sag (dip) and Momentary interruption
 High voltage transients (spikes)
 Current distortion (harmonics)
 Voltage distortion and voltage flicker caused by distorted
current loads
 Voltage unbalance
EPRI (Electrical Power
Research Institute)
• Monitored 300 sites for 2+
years.
• 92% of all events were voltage
sags under 2 seconds
• 4% of event interruptions from
2 seconds to 10 minutes
 Voltage notching
 Uncommon issues in the U.S. and high-tech. parks:



brownout
voltage swell
frequency variation
 Poor “grounding”
12
Voltage Sag (Dip) Characterization
 Sag - RMS voltage reduction between 1/2 cycle - 60 sec
 Magnitude and Duration
1
Duration: 4 Cycles
0.5
0
0
1
2
3
4
5
6
7
8
-0.5
-1
Magnitude: 60% Remaining
13
Voltage Sag
90%
Magnitude (per unit)
1.0
0.8
0.6
0.4
0.2
0.0
1
10
100
1000
Duration (ms)
14
Why mostly brief sags and interruptions?
12 kV
 Radial Distribution
69 kV
 Reclosing breakers
F1
" C"
20 MVA
F2
 V = Vs – Zline*I
 Fault results in short voltage
sags and interruptions for
most customers, affecting
up to 200 mile radius
" B"
1500kVA
480 VOLTS
THREE PHASE FAULT
" A"
F3
VOLTAGE
1. 0
0. 5
VOLTAGE AT "C"
AND ON F1 & F3
VOLTAGE AT "B"
0. 0
0 BEGIN F2
FAULT OPENS
TIME
V=0.67 p.u.
V=0.40 p.u.
F2
F2
CLOSES OPENS
FAULT
F2
CLEARS CLOSES
15
Why Sag Durations are short
Clearing Time in Cycles
Type of Fault
Typical Minimum
Typical Time Delay
Number of Retries
Clearing Device
Expulsion Fuse
0.5
0.5 to 60
None
Current Limiting Fuse
0.25 or less
0.25 to 6
None
Electronic Recloser
3
1 to 30
0 to 4
Oil Circuit Breaker
5
1 to 60
0 to 4
SF6 or Vacuum Breaker
3–5
1 to 60
0 to 4
Source: IEEE Std 493
16
Sags at High-Tech Mfg. Sites
 Very few outages, still
many sags!
 1000 sag events from
15 Semi plants
 Avg. 5.4 events below
CBEMA per year…with
transmission-level
service!
 SEMI F47
source: International SEMATECH & EPRI, 1999
Impact of Voltage Sags
Sensitivity of various 3-ph. 4kW drives to single-phase sag
(rated speed, torque) [Djokic]
18
Impact of Voltage Sags
% of Nominal Voltage
AC Relay Voltage Sag Tolerance Curves
100
90
80
70
60
50
40
30
20
10
0
0
50
100
150
200
250
300
350
400
450
500
Duration of Sag (milliseconds)
Upper range
Average
Lower Range
Source: IEEE Std 1346-1998
19
Data Corruption
Source: Djokic
IEEE P1668 – a new standard
 Recommended Practice for Voltage Sag and Interruption
Ride-through Testing for End-use Electrical Equipment
Less than 1,000 Volts
 A standard for the response of electrical equipment to voltage sags
 Expected to include:
 Guidance for evaluation of equipment sensitivity to voltage sags and
interruptions
 Minimum performance criteria to specify during the purchasing process
 Levels of performance for acceptance of the product
 Voltage tolerance curves for three-phase equipment: more useful than CBEMA
or ITIC
Effect of Voltage Sags on Equipment
 Most common effect is equipment drops offline
 PLC shutdown
 Open contact or relay (As little as 80% remaining voltage for 1 Cycle)
 A secondary effect is that when voltage returns, high current inrush can occur because the Softcharge circuit is bypassed
 RF Amplifiers, Gradient Amplifiers, and Low Voltage Power Supplies subjected to repeated
hits—Fail.
Typical rectifier circuit diagram:
Voltage SAGS can shut-down and/or damage equipment!
22
Voltage Sags Effect Equipment
Example: Inrush current measured for 1kVA electronic load
Inrush after Sag
Normal Inrush
Volts
Amps
Volts
0
Amps
5
10
• Peak inrush 10A
• Soft-charge
circuit is active
0
20
40
• Peak inrush 50A
• Soft-charge
circuit bypassed
Note the scale change necessary to get the sagged results on the same page!
23
Only some machines shut down. Why?
•
Fabrication or Assembly Line Layout:
480-b
Machine 1
Machine 2
Machine 3
Machine 4
Machine 5
Machine 6
480-a
•
Machine power distribution and power supplies vary:
L1
L2
L3
∆:Y
Tranf.
Controls
Power
L2
Rect.
Controls
Power
L1
Tranf.
Rect.
Tranf.
Controls
Power
Tranf.
Rect.
Controls
Power
L3
L1
Tranf.
Rect.
Rect.
Controls
Power
L3
N
Rect.
Controls
Power
L2
N
Tranf.
L2
L3
N
Controls
Power
L1
Tranf.
Rect.
Detection of Power Quality Events
 Monitoring is Key to Knowing the Local Power
Quality
 I-Sense, I-Grid Voltage Monitoring
 I-Sense voltage monitor device
 I-Grid network of monitors and database
servers
 information and notification service



Email & text message notification in ‘real time’
Web summary, available from anywhere
PDF Reports
I-Grid
Use Web browser to:
•View event details
•Manage accounts and monitors
•Generate reports and export data
I-Sense monitors record & report
PQ event data via the Internet
I-Sense Owners
Internet
I-Grid
Servers
&
Database
Web
Utility Engineer
Facility Engineer
Email
Other users
•Real-time notifications
•Report delivery
Agenda
27
Sag Correction Solutions
DySC Protection
Stand-by UPS
Protection
CVT
Protection
On-Line UPS
Protection
28
28
DySC® and UPS Correction Capability
29
UPS Product Offering
30
DySC® (Dynamic Sag Corrector)
 DySC® (pronounced “Disk”) is an adaptive power supply that optimizes the remaining
power during a sag by using patented inverter technology to compensate for the sag
thereby maintaining an uninterrupted flow of optimal power to the load thus maximizing
uptime, minimizing inventory loss and reducing maintenance costs
 Up to 5 seconds of ride through
 U.S. and International voltages available
 Scalable solution
MiniDySC® (single-phase; 0.25-12 kVA)
ProDySC® (3-phase; 9-167 kVA)
MegaDySC® (3-phase; 263-2000 kVA)
31
DySC® - Normal Operation
DySC®
DSP Controller
Auto
By-Pass
Utility
Load
Static
Switch
CrossCoupling
Transformer
Power Conversion
Rectifier
Inverter
Core
Component
Activity
DSP Controller
Constantly monitors incoming power, system integrity and load
Static Switch (99% efficient)
Closed. Sends power directly to the load
Cross-Coupling Transformer
Idle
Power Conversion Core
Idle
Automatic By-Pass
Idle
Normal Operation - The DySC® monitors power quality continuously,
while the power electronics are in standby 99.99% of the time
32
DySC - Voltage Event
DySC®
DSP Controller
Auto
By-Pass
Utility
Load
Static
Switch
CrossCoupling
Transformer
Component
Power Conversion
Rectifier
Inverter
Core
Activity
DSP Controller
Detects the leading edge of a voltage sag, immediately routing
power thru the C-C Transformer and Power Conversion Core
Static Switch (99% efficient)
Open
Cross-Coupling Transformer
Pulls additional power from the grid
Power Conversion Core
Rectifies and inverts to recreate a true sinusoidal Output
Automatic By-Pass
Idle
DySC® is “On” in under 2 milliseconds and recreates a true sinusoidal output
33
DySC Operation
Normal Operation (Monitoring)
• Static Switch ON, Highly efficient
• Power electronics OFF
• Capacitors charged & ready
• No thermal cycling, long life
• Low maintenance
Voltage Sag Correction
• 1-2 millisec. detection
• Static switch OFF
• Power Electronics ON, to produce
corrected sinusoidal load voltage
• Energy from capacitors needed only
for sags below 50%
Example: voltage sag to 60%, full load
• We keep load voltage at 100%,
so load power remains 100%
• Input Current rises briefly
to (100% / 60%) = 167%
• Load energy comes from ac input,
not from capacitors!
V = 100%
V = 60%
V = 100%
167%
(V = 40%)
100%
LOAD
67%
167%
100%
100%
patented
• Static bypass 99.99% of the time
• Corrects voltage by maintaining power flow (P = V x I)
Most of the time the DySC® is in a monitoring mode
34
DySC Sag Correction
330 kVA MegaDySC responding to 3-phase 50% voltage sag, duration 4.5 seconds
input
waveforms
output
waveforms
35
DySC Interruption Correction
input
rms voltage
330 kVA MegaDySC-ER
3-phase interruption
for 250 ms (15 cycles)
90%
output
rms voltage
36
For More Information or Questions
 Power Quality at Automation Fair 2012

Essential Components (Booth 127): Protection Solutions

Energy Management (Booth 541): Power Quality Monitoring

Backroom Session: Hands-on DySC and I-Sense / I-Grid

More information available at Booths
Thank you for your attention. Questions?
Follow ROKAutomation on Facebook & Twitter.
Connect with us on LinkedIn.
www.rockwellautomation.com

Voltage Sag Protection

Transcription

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