POWERLINE BUSHFIRE SAFETY PROGRAM · 2017. 3. 10. · POWERLINE BUSHFIRE SAFETY PROGRAM Ignition...

POWERLINE BUSHFIRE SAFETY PROGRAM Ignition tests – lo-sag conductor

4 December 2015

Report and analysis by Dr Tony Marxsen, Marxsen Consulting Pty Ltd

This report was commissioned and produced with the authorisation of the Powerline Bushfire Safety Program, Department of Economic Development, Jobs, Transport and Resources.

P a g e | 1

© Marxsen Consulting Pty Ltd Friday, 4 December 2015

Centre of Excellence - Electricity Bushfire Safety

The Victorian Government is committed to leading ground-breaking research and accelerating the development of innovative technologies in the field of powerline bushfire safety.

The 10 year, $750 million Powerline Bushfire Safety Program (PBSP) was established in December 2011 for the purpose of implementing the recommendations from the Victorian Bushfires Royal Commission and subsequent Powerline Bushfire Safety Taskforce.

The PBSP’s primary purpose is to reduce the harm to people and property from bushfires started by electricity assets. This includes a five year, $10 million Research and Development Fund that invests in R&D initiatives aimed at reducing the risk of fires starting from powerlines.

The Victorian Government is committed to ensuring that the fight against the threat of bushfires uses the best proven technologies available and draws upon the know-how of those at the forefront of innovation. The critical areas of funding priority include:

bushfire mapping and modelling;

powerline faults and fire ignition; and

improved powerline conductor technology.

Working closely with industry, regulators and the research community the PBSP has undertaken projects which aim to improve the knowledge of bushfire behaviour, bushfire risk and advancing technological solutions that both contribute to enhanced safety on Victoria’s electricity distribution network and leave a legacy that will continue well after the life of the program.

The research in this paper forms part of the 2015 Kilmore Rapid Earth Fault Limiter (REFCL) trial project as set out in the REFCL Technologies test program final report

This report details the arc-ignition testing carried out on a type of covered conductor, lo Sag, for Single Wire Earth Return powerlines.

The Victorian Government is making available the findings from this research in order to foster commercial development of new or enhanced products to further technology that prevents bushfires from powerlines.

P a g e | 2


Disclaimer

This report outlines the results of tests carried out for the Powerline Bushfire Safety Program at a purpose-built facility in Kilmore Victoria in the second half of 2015 in accordance with an Agreement between Marxsen Consulting Pty Ltd and the Victorian Department of Economic Development Jobs Transport and Resources. This report contains test results, observations, analysis, commentary and interpretation.

Subject to the Agreement, no warranty can be offered to third parties for:

The application of anything in this report for any purpose other than those required by the specific objectives stated in the body of the project report.

The direct application of anything contained in this report to any situation other than those that were recorded in the tests.

A complete set of test records is available in the public domain or (in the case of very large video files) upon request from the Powerline Bushfire Safety Program. Readers are advised to rely on their own analysis of these records if they wish to use this report for any purpose other than the specific objectives of the test program stated in the body of the project report.

Readers should in particular note the following qualifications:

The information in this report relates to ‘wire on ground’ powerline earth faults only. Readers who wish to use these results to derive conclusions for other types of network earth fault should rely on their own investigations.

Definitions of worst case fire risk conditions for ignition were derived from limited data and small numbers of tests. No warranty is offered that even worse fire risk condition will not occur in practice.

All reasonable care has been taken to clearly outline the rationale and evidence for findings, but readers should make their own judgements of the merits of such findings before relying on them.

Where a level of statistical uncertainty is stated, this is a statistical measure which cannot be applied to individual cases or small numbers of cases, but can only be validly applied to cohorts of cases large enough to meet the normal criteria set out in statistical theory.

Quantification of statistical certainty has not been possible for some findings due to test-to- test variation of factors that influence ignition outcomes. In such cases, readers should form their own judgement of the level of confidence they can place on the findings concerned.

Many assumptions were used to generate insights, derive findings and interpret results. All reasonable care has been taken to explicitly document these assumptions and explain the rationale in each case, but no warranty can be offered that such documentation is complete or that any implicit or explicit assumptions used are valid.

Where mathematical theory has been used to derive insights from test results, care has been taken to outline the theory and how it was applied. However, no warranty is offered that the theory employed is valid or correctly applied.

P a g e | 3


Contents

1 EXECUTIVE SUMMARY ............................................................................................................................. 5

1.1.1 Uneven ground with non-uniform vegetation cover under the fallen wire ........................................ 5 1.1.2 Fault duration .................................................................................................................................... 5

2 THE PROJECT .................................................................................................................................................. 6

3 IGNITION PROCESSES IN ‘WIRE ON GROUND’ EARTH FAULTS ...................................................................... 6

3.1 IGNITION BY FALLEN STEEL CONDUCTOR.................................................................................................................. 6 3.2 IGNITION BY FALLEN LO-SAG CONDUCTOR ............................................................................................................... 7 3.1 GROWTH OF CURRENT IN ‘WIRE DOWN’ FAULTS ....................................................................................................... 9 3.2 EFFECTS OF DIFFERENT CONDUCTOR MECHANICAL PROPERTIES.................................................................................... 9 3.3 PERFORMANCE OF LO-SAG CONDUCTOR PLASTIC COVERING ..................................................................................... 11

3.3.1 Withstand of voltage stress .................................................................................................................. 11 3.3.2 Withstand of arc and fire exposure ................................................................................................. 12

3.4 OTHER BENEFITS OF COVERED CONDUCTOR ........................................................................................................... 14

4 IGNITION TEST RESULTS ............................................................................................................................... 14

3 TEST PROGRAM DESIGN .............................................................................................................................. 15

3.1 USE OF 2014 REFCL TRIAL DESIGN ..................................................................................................................... 15 3.2 PREPARATION OF CONDUCTOR SAMPLES FOR TESTS ............................................................................................ 16 3.3 TEST PARAMETERS ........................................................................................................................................... 18

4 APPENDIX A: TEST RECORDS........................................................................................................................ 20

4.1.1 Valid ignition tests ........................................................................................................................... 20 4.1.2 Setup and invalid tests .......................................................................................................................... 21

P a g e | 4


List of abbreviations

Acronym Explanation

50Hz 50 cycles per second – the frequency of electricity distributed in Victoria

Amp, A Amperes – the unit used to measure flow of electric current

DEDJTR The Victorian Department of Economic Development Jobs Transport and Resources

FMC Fuel Moisture Content – the proportion of water (by weight) in dry grass fuel

Ohm The unit of measurement of electrical resistance (ratio of voltage to current)

REFCL Rapid Earth Fault Current Limiter – a technology that quickly limits earth fault current

VESI The Victorian Electricity Supply Industry

22kV 22,000 volts – the ‘wire to wire’ voltage on most of Victoria’s electricity networks

ACR Automatic Circuit Recloser – a remote controlled pole-mounted high voltage switch

DBRG The Distribution Business Reference Group – network owner senior executives

ESV Energy Safe Victoria – Victoria’s energy safety regulator

NER Neutral Earthing Resistor – a non-REFCL network earthing approach used in Victoria

PBST, PBSP Powerline Bushfire Safety Taskforce (2011) and Program (current)

TWG The PBSP Technical Working Group

P a g e | 5


1 Executive summary

This report sets out findings from ‘wire down’ ignition tests carried out at Kilmore South in June and September 2015. These tests compared the fire performance of lo-sag conductor and steel conductor in ‘wire on ground’ faults under near-worst-case fire risk conditions. Table 1 summarises the findings derived from the tests results. These findings are just one input into much wider assessment of the overall potential benefits of lo-sag and other covered conductor products.

Table 1: summary of findings – ignition tests on lo-sag conductor

1 In a situation of flat ground with uniform cover by dry grass, i.e. no patches of bare soil larger than about 50mm across, and for fault duration of about 85 milliseconds, tests with lo-sag conductor have a higher probability of producing a sustained fire than tests with steel conductor. Tests give central estimates of the fire probabilities of the two conductor types in this specific circumstance under near-worst-case fire risk conditions of lo-sag 67% and steel 37%.

2 Fallen lo-sag conductor will only generate arcs into soil at the location where the inner Aluminium conductor is exposed. Tests confirmed the outer plastic covering on lo-sag conductor does not burn and remains relatively undamaged by 85 milliseconds exposure to an electric arc followed by 30 seconds exposure to fire. Tests also confirmed the leakage current through the outer plastic covering with the conductor lying on the ground is not sufficient to create thermal runaway so it does not create fire risk.

The comparative fire probability of the two conductor types revealed in tests must be interpreted with care. There are two main factors that must be considered before any conclusions can be reached on the comparative fire risk benefits of either conductor:

1.1.1 Uneven ground with non-uniform vegetation cover under the fallen wire

In a situation of non-uniform ground cover by dry grass under worst-case fire risk conditions, the fire probability of lo-sag conductor will vary depending on where the portion of exposed Aluminium conductor impacts the soil, if it does. If it impacts a patch of dry grass, the fire probability indicated by tests is 67%. If it impacts bare soil, the fire probability is zero. If it lands in bushes or a tree, the chance of the exposed Aluminium conductor contacting vegetation may be small, i.e. no fault current may flow at all. In tests, the lo-sag conductor was much stiffer than the steel conductor and much less able to conform to the contour of the soil bed it was impacting, indicating a fallen lo-sag conductor on uneven ground may not produce an earth fault.

Because steel conductor generates multiple arcs into the soil distributed about every 20-80mm along its length, its fire probability in this circumstance is likely to be not less than the test result of 37% as it will always be likely to have one or more of the arcs touch dry grass. Its fire probability may be more than 37% if multiple arcs are in contact with dry grass.

This factor would tend to favour lo-sag conductor as having lower fire risk.

1.1.2 Fault duration

The fire probability of lo-sag conductor will vary with soil current level and fault duration. The tests reported here were (for both conductors) performed with a fault current of around seven or eight amps and fault duration of around 85 milliseconds. If three metres of conductor were to impact the soil in the fault, lo-sag conductor would still draw seven amps but steel conductor may draw up to 60 amps due to multiple arcs into the soil along its length. This would most likely change the comparative fire probability – a fault involving steel conductor may be detected faster and disconnected faster than one involving lo-sag conductor.

This factor would tend to favour steel conductor as having lower fire risk.

P a g e | 6


2 The project

The tests reported here took place as part of the 2015 REFCL Technologies test program established by the Powerline Bushfire Safety Program (PBSP) as a limited duration research project. Full information on the project is set out in the December 2015 final project report: REFCL Technologies test program final report.

3 Ignition processes in ‘wire on ground’ earth faults

As detailed in the 2014 REFCL Trial report, the process of ignition when a high voltage conductor hits the ground is:

1. The conductor hits the ground at 10-15 metres per second and half-buries itself in the earth 2. The conductor bounces back into the air and as it does, draws one or more electric arcs

between it and the earth 3. The electric arcs heat the dry grass near the point of impact causing generation of

inflammable pyrolysis gases such as methane, hydrogen and carbon monoxide 4. The gases accumulate near the arc to reach the concentration in air at which they will ignite,

typically about 4% 5. The arc ignites the gases and the resultant flame in turn heats more dry grass, generates

more gases, and so creates a sustained fire.

Not all arcs cause ignition and not all ignition leads to a sustained fire:

Sometimes the arc is too far away from the fuel to cause enough pyrolysis gas to be generated.

Sometimes, the pyrolysis gases disperse and never reach the concentration required for ignition.

Sometimes the initial small flame after ignition is not close enough to further fuel to create the additional gas required for a sustained fire and it simply goes out.

Sometimes the initial small flame is blown out by random air currents created by the turbulence resulting from the conductor impact.

Sometimes, the conductor puts out the fire on the second bounce.

The random variability caused by all these factors was addressed by statistical analysis of a large number of identical tests, viz. thirty with each conductor type.

3.1 Ignition by fallen steel conductor

In the tests, the impact of a steel conductor usually resulted in the whole length of the conductor burying itself in the soil so very little arcing was visible before the rebound. As the conductor separated from the soil on the first bounce, multiple (generally not less than four) arcs appeared, spread evenly along the 400mm length of the soil test bed. As it bounced further into the air, these usually converged to a smaller number (usually two or three) of higher intensity arcs before the test current was interrupted.

This process is illustrated by Figure 1 and Figure 2 showing how 11 arcs converged down to just three.


P a g e | 7

Figure 1: KMS Test 611 (steel, 12.2A, 78ms) - multiple arcs created as steel conductor clears soil surface on first bounce

Figure 2: KMS Test 611 - convergence of multiple arcs to three arcs 38ms after steel conductor clears surface

3.2 Ignition by fallen lo-sag conductor

Impact of the much thicker lo-sag conductor usually did not result in the conductor burying itself in the soil. Contact between the 15mm of exposed Aluminium and the soil created a single arc at the mid-point of the sample. As the conductor bounced higher this arc spread ‘roots’ over a larger and larger area of soil surface. However, sustained ignition when it occurred always appeared to start close to the centreline of the soil bed near or in amongst the bases of the tufts of grass rather than in the more widely distributed grass ‘fines’. The single arc between the lo-sag conductor and the soil


P a g e | 8

tended to be of higher intensity than any of the multiple arcs produced by similar impacts of steel conductor. This is illustrated in Figure 3 and Figure 4.

Figure 3: KMS Test 610 (lo-sag, 11.5A, 87ms) – early stage of single arc produced by lo-sag conductor

Figure 4: KMS Test 610 - fully developed single arc from lo-sag conductor (48ms after Figure 3)


P a g e | 9

3.1 Growth of current in ‘wire down’ faults

The two conductor types exhibited different current profiles during the short period of arc current:

Steel: arc current tended to go immediately to its peak value and remain relatively constant until interrupted by the end of the test.

Lo-sag: arc current tended to grow progressively to reach its peak value just prior to current interruption at the end of the test.

These two patterns are illustrated in Figure 7 on the next page. It was considered likely the progressive growth of current in the lo-sag tests corresponded with the progressive spread of arc ‘roots’ across the soil surface. Similar arc-root spread was not as apparent with steel conductor.

3.2 Effects of different conductor mechanical properties

The lo-sag conductor deformed upon impact with the soil bed in a way that lifted the centre section clear of the soil as shown in Figure 5. Sometimes there was no contact between the exposed Aluminium section and the soil until the conductor straightened as it rebounded.

Figure 5: MS Test 586 (invalid) - example of lo-sag conductor deformation upon impact

To achieve consistent fault current duration (considered essential for reliable comparisons between the two conductor types), the two ends of the soil bed were ‘chamfered’ in lo-sag tests so the whole length of the conductor hit the soil on the first bounce. Only tests in which the lo-sag conductor arced to the soil on first contact were marked as valid tests.

This issue illustrated the different propensity of the two conductor types to contact the soil: the stiff lo-sag conductor showed a reduced likelihood of contact compared to the more flexible steel.

Steel conductor also deformed to some extent usually buried itself in the soil before it rebounded, as shown in Figure 6. This sometimes prevented any arcs appearing for up to 30-40 milliseconds.

Figure 6: Test 585 - steel conductor buried in soil upon impact

© Marxsen Consulting Pty Ltd Friday, 4 December 2015 KMS lo-sag conductor tests final report 151204

Figure 7: progressive growth of current during lo-sag tests compared to steel tests

Test RMS current Current waveform

557

Lo-sag 8.0A

594

Steel 7.9A

P a g e | 10

P a g e | 11


3.3 Performance of lo-sag conductor plastic covering

Two aspects of the performance of the lo-sag plastic covering were assessed:

Propensity for insulation breakdown under sustained high voltage stress; and

Resistance to arc and fire damage.

3.3.1 Withstand of voltage stress

Two tests of 60 seconds duration were performed to measure the current through the plastic covering on the lo-sag conductor. They revealed patterns of fast (<2µs)1 current spikes typical of partial discharge as shown in Figure 8 (lying on grass) and Figure 9 (lying on sand).

Figure 8: KMS Test 533 - current through lo-sag conductor plastic covering lying on dry grass on dry sand

Figure 9: KMS Test 534 - current through lo-sag conductor plastic covering on lying dry sand with no grass

1

The data acquisition system sampled at 100MS/s but only every 200th sample was recorded, giving an effective rate of

500kS/s. Each spike showed as a single data point away from the noise band around the zero current axis.


P a g e | 12

3.3.2 Withstand of arc and fire exposure

The standard comparison ignition tests (nominal 7 amps for 85 milliseconds) did not materially damage the lo-sag conductor. The exposed Aluminium section generally showed one or two pinholes and a small area or narrow track of matt surface where the arc contact point had been. The edges of the plastic covering occasionally showed signs of slight alteration by the test. Typical post-test samples are shown in Figure 10.

Figure 10: lo-sag conductor samples after valid ignition tests

Pre-test (KMS Tests 540-620)

Clean metal, sharp edges on plastic

KMS Test 540: new sample

16A arc for 0.8s plus 20s grass fire - NB: this was an

invalid test due to the excessive current duration.

Discolouration, possible slight bulge in metal

surface, signs of plastic softening and shrinkage


11A for 0.1s, no fire (valid test)

Pinholes and matt arc track on metal, no signs of

plastic softening


8A arc for 0.085s plus 30s grass fire (valid test)

Lathe grooves, pinholes, signs of plastic softening

and shrinkage


6.2A arc for 0.08s plus 30s grass fire (valid test)

Lathe grooves, pinholes with matt arc track on

metal, signs of plastic softening and shrinkage


P a g e | 13

Initial proof of concept tests were performed using a single lo-sag conductor sample exposed to longer duration higher current arcs than in the standard comparison tests. None of the conductor constituents caught fire, nor was the structural integrity of the conductor destroyed, though continued severe tests may have eventually eroded the carbon fibre core to the extent this could happen.

Figure 11: effects of proof-of-concept2

ignition tests on single lo-sag sample

Pre-test (KMS Tests 533-538)

Test 536: new sample

2.5 A arc for 8.35s plus 20s fire

Test 537: same sample

18A arc for 0.1s plus 30s fire

Test 538: same sample

>37A arc for 10ms then 20A arc for 70ms plus

25s fire

2

These proof-of-concept tests were unrealistically severe and not at all reflective of the conditions in real ‘wire down’ earth faults. They were also done as a series of repeated tests on a single conductor sample so damage was cumulative.


P a g e | 14

3.4 Other benefits of covered conductor

The case for covered conductor includes fire risk reduction and a range of other benefits related to public safety. The test program reported here was focused solely on fire risk in ‘wire down’ earth faults. The following benefits of covered conductor were recognised but not assessed in the test program:

Fire risk reduction in ‘branch touching wire’ and ‘farm machinery touching wire’ faults.

Potential fire risk reduction and public safety benefits in asset failures or other events (e.g. vehicle impacts) that result in an unbroken length of conductor dropping to the ground.

Reduced supply interruptions from animal and bird faults as well as the above scenarios.

The capability of lo-sag conductor to replace steel conductors in SWER or single phase powerlines without the necessity of installing additional poles was also not assessed.

4 Ignition test results

The large number of random variables involved in the chain of events between the instant of conductor impact and creation of a sustained fire necessitated a statistical approach to the measurement of fire probability.

To provide sufficient results for reasonably reliable statistical analysis, 60 tests were performed: 30 tests with each conductor type.

The conductor type was changed after every test to minimise any risk of systemic bias in the comparison due to variations in factors such as air temperature, soil and grass moisture levels, etc.

The fire probability of each conductor type under the specific conditions of the tests is shown in Figure 12.

Figure 12: comparative fire probability of steel and lo-sag conductor in tests

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

0%

The result shown in Figure 12 must be interpreted with care. The situation in real ‘wire down’ earth faults is more varied and more complex than the standardised conditions of the tests. In particular:

1 Vegetation cover: Because lo-sag conductor produces only a single arc, there is a greater chance that this arc will strike bare ground and no fire will result before the fault is detected and the


P a g e | 15

powerline disconnected. Steel on the other hand will strike multiple arcs along the length of the fallen conductor, i.e. in a diverse range of micro-environments, and will therefore have a higher chance of encountering the conditions that will result in sustained ignition.

2 Fault geometry: Lo-sag conductor is much stiffer than steel and it is quite possible that the exposed section of Aluminium may be suspended clear of the ground by uneven ground or vegetation, in which case no fault current will flow.

Either or both of these factors combined may significantly reduce the ignition probability of lo-sag conductor in real earth faults enough to significantly erode or even reverse the overall comparative result shown in Figure 12 above.

3 Test program design

The 2015 REFCL Technologies test program used a custom-built test facility located at Kilmore South about 50 kilometres north of Melbourne.

3.1 Use of 2014 REFCL Trial design

A detailed description of the experiment design and test site concept is set out in the 2014 REFCL Trial report. The key design elements carried over into the KMS tests included:

1. The underlying principles of realism, direct comparison, and testing in worst case conditions 2. Selection of conductor impact speed and bounce height 3. Selection of soil, fuel and soil-fuel bed geometry 4. Selection of worst case fire weather conditions and fuel moisture content 5. Overall site concept including safety architecture 6. Test procedures and site operating procedures 7. The ‘wire down’ test rig 8. The data acquisition system and transducers

Changes made to the design were primarily matters of detail. They included:

1. Use of insulated shipping containers for the test rig and soil-bed conditioning spaces – this reduced heater load and allowed removal of the air diffuser around the ignition test space.

2. Use of isolated LV supply to the Control Hut instead of a generator 3. Use of normal LV supply to the test rig and HV yard equipment instead of a generator 4. Overhead HV supply to the test rig instead of short lengths of underground cable 5. Omission of the ‘sandpit’ parallel current path in the test rig container 6. Use of a GoPro camera in the test ignition space as the recorder of fire results 7. Use of a wideband 0.200 Ohm shunt to measure soil current.

The test site as built is shown in Figure 13 and Figure 14.

Figure 13: the Kilmore South test facility under construction (180 degree panorama)

The test facility was commissioned on 11th May 2015. Figure 14 shows its condition during test days.


P a g e | 16

Figure 14: the Kilmore South test facility as commissioned

3.2 Preparation of conductor samples for tests

The experiment design was influenced by the only known breakage of lo-sag conductor in the field (during a line stringing operation in South-West Victoria), which produced the break shown in Figure 15.

Figure 15: broken lo-sag conductor (11 Dec 2014)

The lo-sag conductor was prepared for tests by performing the following steps:

Cut conductor samples to 725mm length

Strip the tough plastic covering back at each end to expose 50mm of bare Aluminium

Using a lathe, strip the plastic covering back to expose 15mm of bare Aluminium at the mid- point of the sample

Mount the sample in the test rig arm by fastening one of the bare ends in a collet at the end of the arm and placing the other end in a hollow tube to constrain its movement

Replace the sample with a new one after every test.

A sample is shown in Figure 16 mounted in the test rig arm ready for an ignition test.


P a g e | 17

Figure 16: test rig arm with lo-sag conductor sample ready for test

Steel conductor was not replaced after each test, though it was cleaned with a scour pad to remove soot and burned grass fragments. The outer end of the steel conductor sample was fastened in the same collet used for the lo-sag samples. The inner end was wrapped around a bolt passed through the arm tube. This prevented the steel conductor sample from coming adrift in the test. A sample of steel conductor mounted in the test rig is shown in Figure 17.

Figure 17: steel conductor mounted in test rig arm ready for test


P a g e | 18

3.3 Test parameters

The target parameters for the ‘wire down’ ignition tests were:

1. Arc current of around five to ten amps. Eight amps drawn over a 400mm length of fallen conductor in a test implies a fault current of 60 amps spread over the worst-case minimum length of fallen conductor (three metres) in a network. This is within the range of typical earth fault currents in rural Victorian networks, especially SWER networks. In tests, the soil current depends on the soil moisture content which is not easy to control without compromising fuel moisture content.

2. Arc duration of around 85 milliseconds. Although modern reclosers can achieve fault clearance within 40 milliseconds, there are a variety of legacy devices on Victoria’s rural networks that exhibit a wide range of fault clearance performance. A fault clearance time of 85 milliseconds was seen as within the range of typical performance. In tests, the duration can be set reasonably accurately with the main cause of variation being the time between when the switch opens and the next current zero-crossing, i.e. a range of ten milliseconds plus some allowance for mechanical variations in the conductor-soil impact due to deformation of the conductor sample.

The actual test conditions approached the target parameters on average with some test-to-test variation. Test current duration as shown in Figure 18 was generally within ten milliseconds of the 85 millisecond target with a couple of outlier tests at 69 and 99 milliseconds.

Figure 18: current duration in valid tests

25

20

15

10

5

0

60 65 70 75 80 85 90 95 100 105

Current duration (ms)

Peak current was mostly within the target range as shown in Figure 19.

Figure 19: Peak current in valid tests

16

14

12

10

8

6

4

2

0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Peak current (amps)

Cou

nt

(n =

60)

Co

un

t (n

= 6

0)


P a g e | 19

The peak current tended to be lower for lo-sag tests, as shown in Figure 20, averaging 6.8 amps compared with an average of 8.4 amps for steel.

Figure 20: peak current by conductor type in valid tests

12

10

8

6

4

2

0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Peak current (amps)

Steel Lo-sag

Grass moisture content was not measured in every test. It was higher than defined worst-case (<5%), as shown in Figure 21. This was considered acceptable given the swap of conductor type after every test and the direct comparison objective of the test program.

Figure 21: fuel moisture content in valid tests

10

9

8

7

6

5

4

3

2

1

0

4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5

Fuel Moisture (% wt)

Co

un

t (n

= 3

0 f

or

eac

h c

on

du

cto

r ty

pe

)

Co

un

t (n

= 2

5)


P a g e | 20

4 Appendix A: test records

4.1.1 Valid ignition tests

Sixty valid tests were performed, thirty on each conductor type:

Test No. Date Time Conductor Current (A) Current Duration (ms) Fire

Valid On-site FMC (%)

541 24/09/2015 18:19:13 LoSag 10.8 99 N Y 7.94

552 28/09/2015 12:50:53 312 steel 8.4 87 N Y 6.9

553 28/09/2015 13:36:05 LoSag 9.0 77 Y Y 554 28/09/2015 13:53:39 312 steel 7.68 84 N Y 6.45

555 28/09/2015 14:46:00 LoSag 6.3 84 N Y 4.8

556 28/09/2015 15:09:44 312 steel 9.9 87 Y Y 557 28/09/2015 15:23:29 LoSag 8.0 85 Y Y 558 28/09/2015 15:39:08 312 steel 8.77 86 N Y 4.95

559 28/09/2015 15:57:54 LoSag 8.1 78 N Y 5.73

560 28/09/2015 16:12:14 312 steel 8.73 79 N Y 6.47

561 28/09/2015 16:27:41 LoSag 7.4 78 Y Y 562 28/09/2015 16:48:27 312 steel 10.62 83 N Y 5.74

563 28/09/2015 17:02:30 LoSag 7.2 87 Y Y 564 28/09/2015 17:12:58 312 steel 8.8 86 N Y 7.03

565 28/09/2015 17:23:37 LoSag 7.4 69 N Y 6.85

566 29/09/2015 9:09:00 312 steel 7.93 87 N Y 7.63

567 29/09/2015 9:15:03 LoSag 5.0 85 N Y 568 29/09/2015 9:30:05 312 steel 6.16 88 N Y 8

569 29/09/2015 9:42:18 LoSag 6.5 79 Y Y 570 29/09/2015 9:56:00 312 steel 6.98 87 N Y 7.05

571 29/09/2015 10:14:37 LoSag 4.3 79 N Y 7.54

572 29/09/2015 10:29:29 312 steel 6.01 84 Y Y 573 29/09/2015 10:49:57 LoSag 5.2 79 Y Y 574 29/09/2015 11:04:12 312 steel 9.66 84 N Y 575 29/09/2015 11:28:46 LoSag 5.6 82 Y Y 576 29/09/2015 11:43:00 312 steel 8.08 79 N Y 7.14

577 29/09/2015 11:57:10 LoSag 3.8 78 Y Y 578 29/09/2015 12:12:27 312 steel 6.5 85 N Y 4.82

579 29/09/2015 13:29:54 LoSag 6.6 78 Y Y 580 29/09/2015 13:43:04 312 steel 6.43 86 N Y 7.5

582 29/09/2015 14:14:17 312 steel 6.01 79 N Y 7.57

583 29/09/2015 14:26:51 LoSag 5.3 85 Y Y 584 29/09/2015 14:42:09 LoSag 7.6 84 Y Y 585 29/09/2015 14:56:44 312 steel 9.7 86 Y Y 587 29/09/2015 15:29:04 312 steel 8.39 89 Y Y 588 29/09/2015 15:40:16 LoSag 5.2 84 N Y 7.78

589 29/09/2015 15:53:33 LoSag 5.4 78 N Y 7.56

590 29/09/2015 16:08:58 312 steel 7.87 84 N Y 7.94

591 29/09/2015 16:19:50 LoSag 5.7 79 Y Y 592 29/09/2015 16:31:22 312 steel 8.66 86 Y Y 593 29/09/2015 16:42:31 LoSag 7.3 89 Y Y 594 29/09/2015 16:51:58 312 steel 7.92 88 N Y 595 29/09/2015 17:02:54 LoSag 6.4 85 Y Y 596 29/09/2015 17:12:02 312 steel 8.59 87 Y Y 597 29/09/2015 17:22:20 LoSag 12.0 88 Y Y 598 30/09/2015 9:56:57 312 steel 8.12 88 Y Y 599 30/09/2015 10:05:16 LoSag 6.2 85 Y Y 600 30/09/2015 10:12:52 312 steel 9.27 84 N Y 8.07

601 30/09/2015 10:21:07 LoSag 7.2 85 N Y 8.87

609 30/09/2015 16:59:16 312 steel 17.27 86 Y Y 610 30/09/2015 17:11:23 LoSag 11.5 87 Y Y 611 30/09/2015 17:20:24 312 steel 12.21 78 N Y 7.98

612 30/09/2015 17:31:07 LoSag 6.6 76 Y Y 613 1/10/2015 8:37:21 312 steel 6.01 82 N Y 7.31

615 1/10/2015 9:00:16 312 steel 6.24 88 Y Y 616 1/10/2015 9:10:59 LoSag 5.6 88 Y Y 617 1/10/2015 9:21:07 312 steel 8.91 88 Y Y 618 1/10/2015 9:30:21 LoSag 6.2 79 Y Y 619 1/10/2015 9:41:23 312 steel 7.45 86 Y Y 620 1/10/2015 9:56:01 LoSag 4.6 76 N Y


4.1.2 Setup and invalid tests

The following tests were performed for the purposes of setup or they were ruled invalid for some reason and excluded from the sets of ignition results used in the statistical analyses:

Test No. Date Time Conductor Current (A) Current Duration (ms) Fire Notes

533 25/06/2015 11:52:00 LoSag 0 0 N Current in noise range. Spikes up to 200mA for about 5us. Perception recording triggered manually.

534 25/06/2015 12:00:00 LoSag 0 0 N Conductor resting on bed for 60s. Current levels similar to previous test. Perception recording triggered manually.

535 25/06/2015 12:27:00 LoSag 0 0 N Impact test. Perception recording triggered manually.

536 25/06/2015 12:51:53 LoSag 2.45 8345 Y Conductor cover exposed about 15mm.

537 25/06/2015 13:34:23 LoSag 18.24 113 Y Same conductor as previous test.

538 25/06/2015 13:52:49 LoSag >37 90 Y Fullgurite formed. Current clipped off span.

539 24/09/2015 17:46:00 LoSag - - - No recording on GEN3i because current shunt was disconnected.

540 24/09/2015 18:06:30 LoSag 15.9 809 Y Excessive duration

542 25/09/2015 8:50:00 312 steel >90 106 N Conductor broke away from arm. Not a valid test. Current arced to frame.

543 25/09/2015 10:39:00 312 steel 12.14 99 Y ACR tripped on first attempt, so no GEN3i recording. Test redone with same bed.

544 25/09/2015 11:16:50 LoSag 11.1 107 Y Not valid because current duration >100ms

545 25/09/2015 11:33:00 312 steel 15.91 109 Y Cell supply opened before arm hit the bed. Test redone. Not a valid test because bed was hit twice.

546 25/09/2015 12:24:24 312 steel 15.01 109 Y Cell supply opened before arm hit the bed. Test redone. Not a valid test because bed was hit twice.

547 25/09/2015 12:51:12 LoSag 13.33 95 Y ACR was tripped before the first arm fall. Test redone. Not a valid test because bed was hit twice.

548 25/09/2015 1:08:00 312 steel - - Y Not a valid test because bed was hit twice. No GE3i data from first hit.

549 28/09/2015 12:14:00 312 steel 8.05 264 Y Not a valid test. ACR opened. Current duration was longer than targeted. CDV discharge occurred.

550 28/09/2015 12:29:00 312 steel 8.33 126 N Not valid because current duration >100ms.

551 28/09/2015 12:41:00 312 steel 8.26 102 N Not valid because current duration >100ms.

581 29/09/2015 13:55:35 LoSag 5.48 56 N Current duration too low.

586 29/09/2015 15:15:48 LoSag 7.19 57 Y Current duration too low.

614 1/10/2015 8:48:32 LoSag 2.44 64 N Current duration too low. Very dry bed hence low amps.

Date post:	29-Sep-2020
Category:	Documents
Upload:	others
View:	0 times
Download:	0 times

POWERLINE BUSHFIRE SAFETY PROGRAM · 2017. 3. 10. · POWERLINE BUSHFIRE SAFETY PROGRAM Ignition...

Documents