Guide for High Voltage Direct Current Overhead Transmission ...

Guide for High Voltage Direct Current Overhead Transmission ...

Progress in CIGRE Working Groups on Lightning and Grounding (and IEEE Task Force on HVDC Line Design) Member Report: William A. Chisholm [email protected] 19 July 2016 Meetings Attended Montreal, May 2016 B2.56, Ground Potential Rise at Overhead AC Transmission Line Structures during Power

Frequency Faults B2.AG06.TF007, Dont Put your Arresters near our Dampers Petrache paper on CEATI studies (CDEGS HiFreq vs NEC-4) Lots of interest in German Hybrid AC/DC with positive pole exposed to lightning Meetings Attended GROUND 2016, Brazil June 2016 C4.23, Guide to Procedures for Estimating the Lightning

Performance of Transmission Lines C4.33, Impact of Soil-Parameter Frequency Dependence on the Response of Grounding Electrodes and on the Lightning Performance of Electrical Systems XIII SIPDA, Brazil, September, 2015 C4.36, Winter Lightning: Parameters and Engineering Consequences for Wind Turbines C4.410 TB 633, Lightning Striking Characteristics to Very High Structures Published October 2015

Meetings Attended PES Annual Meeting, July 2016 HVDC Line Design Guide Task Force (July 18) HVDC Line Design Subcommittee (July 20, 8 AM) Meetings Attended Montreal, May 2016 B2.56, Ground Potential Rise at Overhead AC Transmission Line Structures during Power Frequency Faults B2.AG06.TF007, Dont Put your Arresters near our

Dampers Petrache paper on CEATI studies (CDEGS HiFreq vs NEC-4) Lots of interest in German Hybrid AC/DC with positive pole exposed to lightning B2.56 Appendix 2: Step Potential Verification Method Demonstration of the use of two different methods (modeling, testing) to cross-check.

7m V78 B2.56 Appendix 2: Step Potential Verification Method Tower base current injected with electric fence pulse generator. 14 SP_EDC15MZ_6789_1415

7m Tower Base Current (A) 12 10 8 6 Pretrigger Standard Deviation -7 s to -1 s

4 2 Unfiltered 0.047 Average (11) 0.015

Median (20) 0.014 0 Zareba EDC15M-Z Pulse Generator, 180 m CRL with ground rod -2 -1.0E-05 0.0E+00

1.0E-05 Time (s) 2.0E-05 3.0E-05 V78 B2.56 Appendix 2: Step Potential Verification

Method Voltage between two probes measured with oscilloscope. Shown: V6-7 6m V67 B2.56 Appendix 2: Step Potential Verification Method Demonstration of the use of two different

methods (modeling, testing) to cross-check. Measured and modeled: Peak from 7 to 8 m B2.56 Appendix 2: Step Potential Verification Method Conclusions: Cross check of field test to calculation is mandatory. Uniform soil assumption worked here in spite of complex infrastructure (sewer, pipelines) nearby.

Recommendations: Coordinate with C4.33 to confirm the validity of the impulse test method, considering frequency dependence of the soil. Evaluate range of two-layer soil contrast (reflection coefficient) for which inverse distance / quasi-uniform soil model is valid. B2.56 Appendix 2: Step Potential Verification Method Inverse Distance Good

Poor Poor Meetings Attended Montreal, May 2016 B2.56, Ground Potential Rise at Overhead AC Transmission Line Structures during Power Frequency Faults B2.AG06.TF007, Dont Put your Arresters near our Dampers

Petrache paper on CEATI studies (CDEGS HiFreq vs NEC-4) Lots of interest in German Hybrid AC/DC with positive pole exposed to lightning B2-AG06-TF007 INTERACTION OF VIBRATION DAMPERS WITH SURGE ARRESTERS SUMMARY OF MEETING IN MONTREAL May 12, 2016

by David Havard SCOPE OF TF007: Most transmission line surge arrester (TLSA) installations are fitted after construction to improve lightning performance. Surge arresters are large, heavy and often placed on conductors outside vibration damper locations. The objective is to produce a paper for CIGRE Journal of Science and Engineering guideline.

Havard, B2 AG 06 TF.007 14 SCOPE OF TF007 (CONTD): Scheduled completion 2016. Originally on application of dampers to retain aeolian vibration control for surge arresters applications. Based on inputs from WG members, now includes other vibration modes and other forms of failure.

Havard, B2 AG 06 TF.007 15 Meeting of May 12 2016 23 Members and guests in attendance: Agenda included: Outlining points added to the paper since the last meeting Review of new material contributed by email

in the last week Furtado re failure of support for TLSA Vingradov re explosive failure of TLSA and need for Standard Havard, B2 AG 06 TF.00v 16 A review of the 6th draft of the paper Highlighting key points in the paper new experiences offered by members present

Van Dyke re use of AGS clamp support Halsan re loosened corona ring on TLSA Chisholm re damage to supporting chain Havard, B2 AG 06 TF.007 17 Future activities: Update paper with recently acquired and other new material

Target date within one month Next (final?) meeting in Paris (Boulogne) in August 2016 Havard, B2 AG 06 TF.007 18 AUTHOR: DR. DAVID G. HAVARD CONVENOR CIGRE B2-AG06 TF007 PRESIDENT, HAVARD ENGINEERING INC.

TEL: 1-905-273-3076, E-MAIL: [email protected] WEB PAGE: www.havardengineering.com ADDRESS: 3142 LINDENLEA DRIVE, MISSISSAUGA, ONTARIO, CANADA, L5C 2C2 Havard, B2 AG 06 TF.007 19

Meetings Attended GROUND 2016, near Recife, Brazil June 2016 Meetings Attended GROUND 2016, Brazil June 2016 C4.23, Guide to Procedures for Estimating the Lightning Performance of Transmission Lines C4.33, Impact of Soil-Parameter Frequency Dependence on the Response of Grounding Electrodes and on the Lightning Performance of Electrical Systems

XIII SIPDA, Brazil, September, 2015 C4.36, Winter Lightning: Parameters and Engineering Consequences for Wind Turbines C4.410 TB 633, Lightning Striking Characteristics to Very High Structures Published October 2015 C4.23 Meeting, Brazil, June 2016 Responsible: Chris Engelbrecht (convenor) Imre Tannemaat

(secretary) Present draft: 99 pages C4.23 Meeting, Brazil, June 2016 Overview of methodology Meetings Attended GROUND 2016, Brazil June 2016

C4.23, Guide to Procedures for Estimating the Lightning Performance of Transmission Lines C4.33, Impact of Soil-Parameter Frequency Dependence on the Response of Grounding Electrodes and on the Lightning Performance of Electrical Systems XIII SIPDA, Brazil, September, 2015 C4.36, Winter Lightning: Parameters and Engineering Consequences for Wind Turbines C4.410 TB 633, Lightning Striking Characteristics to Very High Structures Published October 2015

Frequency-Dependent Resistivity Resistivity at 100 kHz or 1 MHz is significantly lower than resistivity measured at 100 Hz Effect is strongest for high soil resistivity Effect is well supported by test data Liaison Report: C4.33 Introduction Basic Physical Aspects

Cites the Cole-Cole approach: The permittivity of a material can be described [51] as a complex number given by: The real part of permittivity () The imaginary part () Such losses represent the fraction of energy Frequency-Dependent Resistivity Draft is 74 pages. Contributions in chronological order.

Frequency-Dependent Resistivity Frequency-Dependent Resistivity Typical models, 1000 m soil Organization of Technical Brochure Contributions on the frequency dependence of soil parameters in a chronological order: Smith-Rose (1930s) Scott et al. (1964-1966) Eberle et al. (1969-1983)

Longmire and Smith (1975) Messier (1980-1985) Visacro and Portella (1987) Portella (1997-2000) CIGRE WG C4.2.02 (1995-2005) Chisholm et al. (2003-2016) He et al. ( ..) Visacro and Alipio (2011-2016) Montaa et al. (2012)

CIGRE TB 275 Inclusion CIGRE WG C4.2.02 (1995-2005) In 1995, CIGRE Working Group 02 of Study Committee 36 noted that seven countries (France, Germany, Belgium, Spain, Great Britain, Italy and South Africa) were making use of an ABB HW2A instrument to test the earthing resistance of individual pylons. Fixed frequency of 26 kHz. Electrically isolates the tower under test from neighbours, using the high inductive reactance of any overhead groundwire connections.

Analysis in TB 275 suggested that 150 kHz would be more appropriate for this purpose. CIGRE TB 275 Inclusion REN (Portugal) compared ABB HW2A instrument with measurements of soil resistivity at 4 m depth. Weak power-law relation, with structure impedance at 26 kHz varying roughly to the 1/3 power of low frequency resistivity. CIGRE TB 275 Inclusion Anticipated relation between Z26 kHz and o

from substitution of f = 26 kHz into a Alipio/Visacro model for (f), and normalization to an effective tower perimeter of 30 m (giving 10 at 0 = 300 m). Additional influence of r (f) (21) at 26 kHz is modest, even at 0 = 3000 m. Time-Dependent Effects Resistivity vs time, 500 to 1000 ns

(f) Versus Ionization Effect on peak tower base voltage (f) effect is strong initially, weaker by about 2 s Ionization models introduce onset time constants on the order of 2 s Effect on large-dimension footings (f) effect is the same, large or small dimension Ionization is not so important for footings of transmission lines, compared to single rods

Testability in full scale (f) effect is easy to verify with 1-10 A test current Ionization calls for impulse currents of 30 to 200 kA Meetings Attended PES Annual Meeting, July 2016 HVDC Line Design Guide Task Force (July 18) HVDC Line Design Subcommittee (July 20, 8 AM) Administrative Influence Encouraged HVDC

group to prepare a PES Technical Report rather than a Standard or Guide Faster More tolerant of a range of opinions and options Easier to modify and add new experiences

Technical Influence Chapter 3.4 Grounding considered as return electrode HVDC should always be designed with Overhead Groundwires (OHGW), never unshielded. Role of end-to-end optical fiber cable. Expected dc resistance of OHGW as line return electrode 0.25 for length > 60 km with 9/16 aluminum clad steel 0.03 for length > 300 km with 336 kcmil Linnet ACSR Introduces Insulated Earth Return Wire (below phases) Foundation grounding issues expected relation to soil

resistivity; corrosion aspects; two-layer soil case. Worst case: Separate return electrode (Appendix C) in domain of Substation Committee (Guide 80, Guide 81). Technical Influence Chapter 3.5 Lightning role of dc voltage bias Positive pole adds to stress from negative lightning to tower, so it has lower critical current and thus higher backflashover rate. Use critical current of negative-pole backflashover to estimate the two-pole to

ground fault rate. Technical Influence Chapter 3.5 Lightning role of insulated earth return in improved lightning performance Covered in IEEE Standard 1243/1997 Figure 9, without the supporting matrix math. Technical Report includes 3x3 and 4x4 matrices for surge

impedance coupling coefficients without corona. Technical Influence Chapter 3.5 Lightning role of guy wires on HVDC towers Steel monopole: 250 to 300 Typical lattice tower: 160 to 200 Slender lattice tower with 4 guy wires: < 100 Technical Influence Chapter 3.5 Lightning role of guy wires on HVDC towers

Steel monopole: 250 to 300 Typical lattice tower: 160 to 200 Slender lattice tower with 4 guy wires: < 100 Desirable Lightning Protection Aspects: Two OHGW, widely separated Relatively large-diameter tower body Four guy wires attached to tower with individual soil anchors Technical Influence Chapter 3.5 Lightning role of guy wires on HVDC towers

Typical lattice tower: 160 to 200 Slender lattice tower with 4 guy wires: < 100 Steel monopole: 250 to 300 Desirable: Twin Earth Return Undesirable Lightning Protection Aspects: All groundwires above phases Earth wires too high, too close Thin tower body and arms Single pier foundation rather than 4, 5 or 8 paths to ground

TR Conclusion / Recommendations Technical Report gives an overview of the specific issues related to HVDC overhead line design and some perspective on the production variations in existing HVDC line designs. Some weakness and internal consistency can be improved, but it is ready for next-level approval and publication. Try to avoid the long delay in TR-17 on aeolian vibration, in getting from 99 to 99.9%.

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