Circuit Restoration/Reclosing Philosophies and Power · PDF file ·...
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1 Circuit Restoration/Reclosing Philosophies and Power Quality VELCO Operating Committee January 17, 2013
Transcript of Circuit Restoration/Reclosing Philosophies and Power · PDF file ·...
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Circuit Restoration/Reclosing Philosophies and Power Quality
VELCO Operating Committee January 17, 2013
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Goal
• To have a heightened awareness of how our circuit restoration operating practices and decisions impact each other’s interconnected system, and how they can both enhance and potentially degrade customer service and system reliability.
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Objectives
• Convey the Increasing Importance of Power Quality
• Define the Relationship Between Reclosing and Power Quality
• Explain the Concepts for Effective Automatic Reclosing
• Review Remote Control Reclosing Practices for Different Voltage Classes
• Discuss the Consequences Associated with Reclosing
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Power Quality • It’s No Longer Just Keeping the Lights On
– Microprocessor-Based Equipment More Susceptible – Variable Speed Drives and Other Industry Electronics – Moore’s Law – Integrated Circuit Capacity Doubles Every 18-24
Months • Gordon Moore, April 13, 2005 - noted that transistors would
eventually reach the limits of miniaturization at atomic levels, and we have another 10 to 20 years before we reach a fundamental limit.
• Utility Customers Need To Be More Competitive • Interruptions of Less Than 1/10 second Can Be Costly • A Significant Amount of the Subtransmission System in
VT can Cause Power Quality Issues for Sensitive Commercial Customers
•
Presenter
Presentation Notes
Since the invention of the integrated circuit in 1958, the number of transistors that can be placed inexpensively on an integrated circuit has increased exponentially, doubling approximately every two years. The trend was first observed by Intel co-founder Gordon E. Moore in a 1965 paper. On 13 April 2005, Gordon Moore stated in an interview that the law cannot be sustained indefinitely: "It can't continue forever. The nature of exponentials is that you push them out and eventually disaster happens" and noted that transistors would eventually reach the limits of miniaturization at atomic levels: In terms of size [of transistor] you can see that we're approaching the size of atoms which is a fundamental barrier, but it'll be two or three generations before we get that far—but that's as far out as we've ever been able to see. We have another 10 to 20 years before we reach a fundamental limit. By then they'll be able to make bigger chips and have transistor budgets in the billions
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Power Quality is Impacted By
• Harmonic Distortions (Dirty Power) – Non-Linear Loads Such As Variable Speed Drives and Switching
Power Supplies • Interruptions
– Both Planned and Unplanned • Transient Disturbances
– Lightning and Switching of Lines, Caps, and Cables • Swells and Sags/Dips
– Load or Source Loss, and Fault Clearing • Voltage Fluctuations, Flicker Voltage
– Motor Starting, Arc Furnaces
Presenter
Presentation Notes
Variable Speed Drives and Switching Power Supplies are dependent on either zero crossing or on the peak for proper control
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Power Quality is Measured
• PQ Measurement in “Total Harmonic Distortion” (THD) – Used to define the effect of harmonics on the power system
voltage, expressed as percentage of the fundamental – THD = sqrt (sums of all squares of amplitude of all harmonic
voltages ÷ square of the amplitude of the fundamental frequency) – Voltage Distortion Limits, per ANSI/IEEE Standard 519
• ≤69kV, THD = 5.0% • 69 to 161kV, THD = 2.5% • ≥161kV, THD = 1.5% *Measured at the Point of Common Coupling
• PQ is also Measured by “Total Demand Distortion” and “Telephone Influence Factor” (TIF), per Standard 519
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Power Quality
• Harmonic Distortion
Time (One Cycle)
Current
100%
100%
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Power Quality
• Transient Disturbance (Cap Bank Closing)
Time (One Cycle)
Voltage
100%
100%
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Power Quality
• Voltage Sag (Line Clearing for a Fault)
Time
Voltage
100% 95%
t = 0 t + 6cycles t + 36cycles
Pre-Fault Post-Fault
Remote End Clear
Local End Clear
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Power Quality
• The CBEMA (Computer Business Equipment Manufacturers Association) Curve – Guideline for the Industry Members in Specifying and Designing
Production Equipment, e.g. Power Supplies
Presenter
Presentation Notes
The CBEMA curve was derived by the Computer Business Equipment Manufacturers Association — the acronym used in the name of the curve as a guideline for the organization's members in designing their power supplies. The association designed the curve to point out ways in which system reliability could be provided for electronic equipment. Computers, programmable logic controllers (PLCs), instrumentation, telecom, and other solid-state systems need to be designed to this standard.
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CBEMA Curve
0.0001 0.001 0.01 0.1 1 10 100 1000-100
-50
0
50
100
150
200
250
TIME IN SECONDS
PE
RC
EN
T C
HA
NG
E IN
BU
S V
OLT
AG
E
8.33
ms
OVERVOLTAGE CONDITIONS
UNDERVOLTAGE CONDITIONS
0.5
CY
CLE
RATEDVOLTAGE
ACCEPTABLEPOWER
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ITIC (Information Technology Industry Council) Curve
0.0001 0.001 0.01 0.1 1 10 100 1000-100
-50
0
50
100
150
200
250
TIME IN SECONDS
PE
RC
EN
T C
HA
NG
E IN
BU
S V
OLT
AG
E
8.33
ms
OVERVOLTAGE CONDITIONS
UNDERVOLTAGE CONDITIONS
0.5
CY
CLE
RATEDVOLTAGE
ACCEPTABLEPOWER
10%+--
Presenter
Presentation Notes
The ITIC curve was derived by a working group of CBEMA, which changed its name to the Information Technology Industry Council. This derivation was developed in collaboration with EPRI's Power Electronics Application Center (PEAC). The intent was to develop a curve that more accurately reflects the performance of typical single-phase, 60-Hz computers and their peripherals, and other information technology items like copiers, fax machines, and point-of-sales terminals. While specifically applicable to computer-type equipment (as with the CBEMA curve), the ITIC curve is generally applicable to other equipment containing solid-state devices.
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Example CBEMA Plot
Jan 25Feb 17
Mar 8
Mar 8
Mar 11Apr 15
Apr 23Apr 25
May 21May 31 Jun 1
Jun 10
Jun 17
Jun 22
Jul 18Jul 31Sep 9
Sep 18
Nov 12
0.1 1 10 100 1000
DURATION IN CYCLES
0%
25%
50%
75%
100%
125%
VO
LT
AG
E
2008 ELECTRICAL UTILITY POWER DISTURBANCES --- MAIN SITE
Lack of Stored Energy in Some Equip
June 10, 20% VD for 26 cycles
March 8, 20% VD for 11 cycles 10% VD for 54 cycles
June 22, 23% VD for 9 cycles
Impact
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Power Monitor Recording
Phase A-B Voltage64 Points / Cycle
Volta
ge
Milliseconds
-20000-15000-10000
-50000
5000100001500020000
0 100 200 300 400 500 600 700 800 900 1000
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Power Monitor Recording
Phase A-B VoltageRMS Analysis
RMS
Milliseconds
110001150012000125001300013500
0 100 200 300 400 500 600 700 800 900 1000
Voltage Drop = (13600 – 10987 / 13600) x 100% = 19.2%
Time = 358msec – 27msec = 331msec (19.86 cycles)
Minimum Voltage = 10,987 Volts
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Power System Reclosing • Circuit Restoration is
One of the Most Important Functions of an Operator, with Concern for: – Safety
Public Utility Workers
– Customer Service (e.g. SAIDI)
– Transmission Reliability
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Power System Reclosing • Jackson, TN. The driver was attempting to throw a logging cable over the
logs to secure them and hooked the electric line instead. The Logger said that the tires began to burn within seconds.
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Reclosing Options
• Local Manual Control (Different Control Schemes) – Switchman in Control, Responsible for Checking Conditions – Permissive Control, Indication Relays Supervise Conditions – Safety Precautions, Ground Potential Rise
• Remote SCADA Control
– Permissive Control, Indication Relays Supervise Conditions – Situational Awareness, Decisions Made with Information at Hand
• Automatic
– Permissive Control, Indication Relays Supervise Conditions
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Reclosing Conditions
• Conditions – Bus/Source Alive – Line Alive (Synch-Check)
• phase angle must be within a specified limit and for a specified time – Bus/Source Alive – Line Dead – Bus/Source Dead – Line Alive – Bus/Source Dead – Line Dead
• Indication/Supervising Relays – Reclosing Relay (Device 79) – Synch-Check Relay (Device 25) – Bus/Source Voltage Relay (Device 27B/S) – Line Voltage Relay (Device 27L) – Multifunction Relay (Several Variations)
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Typical Breaker Close Circuit
Local/Remote (Local)
Control Sw (Close)
79 (Close)
+ DC
- DC
Close Bus
Breaker Auxiliary Contact
Close Coil
27B Dead
87 Relay Lockout
27L Live
27B Live
43 Auto
SCADA (Close)
27L Dead
25 Sync
27B Dead
27L Live
Local/Remote (Remote)
27B Live
27L Dead
25 Sync
Breaker Trip Free Design
Breaker Circuitry
Internal Circuitry
N.O.
SCADA B/A
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Automatic Reclosing • Automatic Reclosing Increases Continuity of Service • Overhead Lines
– Distribution - 50 to 80% of Faults are Temporary – Transmission - ≥90% of Faults are Temporary
Varies considerably with differences in climate, lightning intensity, ground conditions, voltage level, line design and etc
• Underground Lines – Virtually all Faults are Permanent • Voltage Class Determines the Reclosing Attempts
– Distribution – Typically 2 to 4 shots and coordinated with downstream devices
– Subtransmission – Varies widely, typically from 1 to 3 shots – Transmission – Typically 1 to 2 shots
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Automatic Reclosing • Success Rates for Reclosing
– Small Additional Percentage of Success After First Attempt – Number of Successful Reclosures, for a Typical “Distribution”
Utility, ref ABB Applied Protection Relaying One automatic reclose attempt – 83.25% Second automatic reclose attempt - 10.05% Third automatic reclose attempt – 1.42%
– Reclose Success Rate for Successive Multiple Reclosures, ref IEEE std. C37.104-2002, IEEE Guide for Automatic Reclosing of Line Circuit Breaker for AC Distribution and Transmission Lines One automatic reclose attempt – 90% Second automatic reclose attempt - 4% Third automatic reclose attempt – 1%
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Automatic Reclosing • Considerations in Applying a Reclosing Scheme
– Circuit Configuration, Looped or Radial – Downstream Devices, e.g. Tapped Loads and Motor Loads – Critical Customer Load being Served, Proximity and PQ Impact – Grounded or Ungrounded System Being Served – Short Circuit Strength, Stronger Source – Upstream Relay Coordination, Ratcheting Effect – Transformer Through Current, e.g. forces on windings – Proximity to Generation, e.g. transient forces on machines – Voltage Across a Breaker, System Angle and Shock to System – Breaker or Recloser Capabilities
• Multiple Interrupting Capability and De-Rating • Stored Energy and Recharge
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Automatic Reclosing • Considerations for Blocking Automatic Reclosing
– Manual Trip – Local Breaker Failure Operation – Receipt of Transfer Trip for Breaker Failure or Protection Scheme – Hot-Line Maintenance, to Include Parallel and Adjacent Lines – Three Phase Faults, EHV – Delayed Remote Backup Clearing – Differential Relay Operations; Busses, Transformers, and Other – Faults on Underground or Submarine Cables – Out-of-Step or Swing Conditions – Under-frequency and Under-voltage Load Shedding Operations – Switch-Onto-Fault Operations – High Impedance Fault Detection
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Automatic Reclosing • VELCO Standard Transmission System Reclosing
– One Automatic Reclose Attempt on a “Dead Line” Condition from One End of Line
– Synch-Check Reclosing from the Opposite “Remote” End • VELCO Automatic Sectionalizing Schemes on Multi-
Terminal Lines – Restore Transmission Continuity with Consideration for:
• Sensitive Areas with Concern for Voltage Performance • Reliability Concern with Severe Weather Events Taking Out
Multiple Lines, e.g. Stowe K24 Tap Line • Special Applications, e.g. Highgate Converter output
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Automatic Reclose Cycle
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Manual and SCADA Reclosing • VELCO Reclosing Philosophy for Permanent Faults
– Two-Terminal Transmission Lines – due to the low probability for successfully reclosing after one automatic attempt along with the concern for both public safety and further equipment damage, VELCO will not make an attempt to reclose via SCADA or manual control. For permanent faults VELCO Engineering will be immediately contacted for analyzing the fault and determining a location. At the same time, VELCO field personnel will be dispatched to inspect the line. VELCO will not reclose the line until the fault has been found and cleared, except with the noted exception below.
– During weather conditions, such as intense lightning storms or ice unloading of conductors, it is possible that the same circuit was tripped within up to 60 seconds following a successful reclose. At the discretion of the VELCO System Operator, s/he can perform either a manual or SCADA reclose without the benefit of engineering analysis or field inspections.
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Manual and SCADA Reclosing • VELCO Reclosing Philosophy for Permanent Faults
- Multi-terminal Transmission Lines with Sectionalizing Capability – faults will be isolated by only closing in on each section of line with downstream switches open. The closest switch shall normally be opened first during the sectionalizing process to reduce the number of system faults.
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Manual and SCADA Reclosing • VELCO Subtransmission System Reclosing Following
Unsuccessful Automatic Attempt(s) – Looped circuit and without tapped loads
• Normally, no reclose attempts made from VELCO end with concern for transformer through-faults and PQ impacts
• VELCO Engineering will be immediately contacted for analyzing the fault and determining a location
• During weather conditions, such as intense lightning storms or ice unloading of conductors, it is possible that the same circuit was tripped within up to approx 60 seconds following a successful reclose. At the discretion of the VELCO and VDU System Operators, perform either a manual or SCADA reclose without the benefit of engineering analysis or field inspections.
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Manual and SCADA Reclosing • VELCO Subtransmission System Reclosing Following
Unsuccessful Automatic Attempt(s) – Looped Circuit with Tapped Loads and Sectionalizing Switches
• In coordination with VDU Operator, perform sectionalizing and use source with consideration for safety and equipment
• VELCO Engineering will be immediately contacted for analyzing the fault and determining a location
• VELCO Evaluating Best Approach for Providing Real-
time Protective Relay Information to the System Operators, e.g. fault location and targets
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Manual and SCADA Reclosing • VELCO Subtransmission System Reclosing Following
Unsuccessful Automatic Attempt(s) – Radial circuit without sectionalizing switches
• Normally, no reclose attempts made from VELCO end with concern for transformer through-faults and PQ impacts
• VELCO Engineering will be immediately contacted for analyzing the fault and determining a location
• During weather conditions, such as intense lightning storms or ice unloading of conductors, it is possible that the same circuit was tripped within up to approx 60 seconds following a successful reclose. Also, during severe weather conditions, such as with high or low ambient temperatures and concern for public safety, at the discretion of the VELCO and VDU System Operators, perform either a manual or SCADA reclose without the benefit of engineering analysis or field inspections.
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Manual and SCADA Reclosing • VELCO Subtransmission System Reclosing Following
Unsuccessful Automatic Attempt(s) – Radial circuit with sectionalizing switches
• In coordination with VDU Operator, perform sectionalizing and use source with consideration for safety and equipment
• VELCO Engineering will be immediately contacted for analyzing the fault and determining a location
– During weather conditions, such as intense lightning storms or ice unloading of conductors, it is possible that the same circuit was tripped within up to approx 60 seconds following a successful reclose. Also, during severe weather conditions, such as with high or low ambient temperatures and concern for public safety, at the discretion of the VELCO and VDU System Operators, perform either a manual or SCADA reclose without the benefit of engineering analysis or field inspections.
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Power Quality and Reclosing
• Questions?
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References
• ANSI/IEEE Standard C37.90 “Relays and Relay Systems Associated with Electric Power Apparatus”
• ANSI/IEEE Standard C37.104 “Guide for Automatic Reclosing of Line Circuit Breakers for AC Distribution and Transmission Lines”
• ANSI/IEEE Standard 519-1992 “Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems”
• Kennedy, Barry W.; Power Quality Primer, McGraw-Hill, 2000 • Elmore, Walter A., et al; Protective Relaying Theory and
Applications, Marcel Dekker, Inc., 1994 • Blackburn, J. L.; Protective Relaying Principles and Applications -
Second Edition; Marcel Dekker, Inc., New York, 1998
