Rate of Change (Trend) PPM, PPM/day or PPM/Year What make sense? - PowerPoint PPT Presentation

Rate of Change (Trend) ∆ PPM, PPM/day or PPM/Year What make sense? C. Beauchemin IEEE Transformer Committee TJH2b Analytical Services Inc. Fall 2013 Meeting C57.104 St-Louis, October 20 – 24, 2013

Fall 2012 • Luiz Cheim presentation (On the Web) • Review of work done to date • Review of factors influencing limits • Presentation also covered various aspect of rate computation

Rate of Gas Increase (ppm/year) vs Sampling Interval???

Rate of Gas Increase (ppm/year) vs Sampling Interval???

Rate of Gas Increase (ppm/year) vs Sampling Interval??? Food for Thought…

Further work to clarify this question • Study of a new set of data • Single source (one lab) • North America • Mix of industrial and utilities

Data set • One source • 123 469 DGA • 44 266 Transformers • Delta computed between actual and previous DGA • 78 660 pairs of DGA • All Gas + TDCG

Sampling Interval Time between sampling 0.007 365 Days 0.006 0.005 Density 0.004 186 Days 0.003 26 Days 91 Days 1107 Days 551 Days 735 Days 942 Days 0.002 0.001 0 0 200 400 600 800 1000 1200 1400 Sampling Interval Days

Sampling Interval Time between sampling 0.007 1 Year 0.006 0.005 Density 0.004 3 Months 6 Months 0.003 1 Month 1.5 Years 2.5 Years 3 Years 2 Years 0.002 0.001 0 0 200 400 600 800 1000 1200 1400 Sampling Interval Days

Data set • Table 3 use TDCG rates of 10 - 30 ppm/day • ppm/year or ml/day is also used to evaluate gassing rate • Preliminary study (last meeting) has been done in ppm/year • 1 ppm/day = 365 ppm/year • 10 ppm/day = 3650 ppm/year • 30 ppm/day = 10950 ppm/year

DGA “Noise” • Oil sampling, transport and analysis do introduce DGA variations from one sample to the next • The same difference between two samples could give different ppm/day (or ppm/year) depending of the period between samples • It is of particular importance for on-line data • How that affect interpretation?

An Example: CH4 • The data set was splits in 8 Groups corresponding to 8 different average sampling periods • Week, Month, Quarter, Half-Year, Year, 2 Years, 3 Years and > 4 years • For each DGA, ppm/year was computed • For each groups, a standard statistic study was performed

Sampling Interval Time between sampling 0.007 1 Year 0.006 0.005 Week Density 0.004 Half Year 0.003 Quarter Month 3 Years 2 Years 0.002 Long 0.001 0 0 200 400 600 800 1000 1200 1400 Sampling Interval Days

Data Set Sampling Intervals 4% 2% 5% 4% 7% Week 10% Month 11% Quarter Half Year 1 Year 2 Years 3 Years Long 57%

Some Definitions 95 Percentile: 95% of the samples are below that value Absolute Change (Delta) Delta PPM = PPM now – PPM last sample Normalised Change (Trend) Trend = Delta PPM / (Date now – Date last sample ) in PPM/Day in PPM/Year (PPM/Day * 365) BoxPlot Graph

BoxPlot Graph Outliers Q3 + 1.5 IQR Third Quartile (75%) 50% of Inter Quartile Median Range Population First Quartile (25%) Q1 - 1.5 IQR Outliers

BoxPlot Graph • Usefully to visually evaluate a group of data – Spread of data – Middle Value – Symmetry of distribution – Outliers • Easy to compare several groups of data • So, what do we have with trend data ?

PPM / Year CH 4 Normalised Rate Week Month Quarter Half Year CH 4 Year 2 Years 3 Years Long

PPM / Year CH 4 Normalised Rate Week Month Quarter Half Year CH 4 Year 2 Years 3 Years Long

PPM / Year CH 4 Normalised Rate Week Month Quarter Half Year CH 4 Year 2 Years 3 Years Long

CH 4 Normalised Rate 95 Percentile Rate VS Sampling Interval 3500 95 Percentile Rate (ppm/year) 3000 2500 2000 1500 1000 500 0 Week Month Quarter Half Year 1 Year 2 Years 3 Years Long Sampling Interval

From Last Presentation

CH 4 Normalised Rate 95 Percentile of Rate Sampling Period PPM/Year PPM/Day Week 3115 8.5 Month 1028 2.8 Quarter 235 0.64 Half Year 55 0.15 1 Year 19 0.052 2 Years 12 0.033 3 Years 8.3 0.023 Long 6.7 0.018 A ratio of 463 between “weekly” and “long term” sampling !!

CH 4 Normalised Rate • If we want to use PPM/year (or PPM/Day) we obviously need a method to handle this spread • Should we have a table for each period? • Which periods ? • How many ? • How complex ? • Added to the “other” complexities ?

Normalised Rate and noise • Maybe we are looking at it the wrong way ? • If we have noise in the data, it would probably be the same for short and long period • If we divide a fixed value by an increasing period, we will obtain a log like curve • As an example, let take 25 ppm / 1 day, /7 days, /14 days … to ppm / year….. • Then:

Simulation of a Constant PPM Delta Example of Fixed Delta / Increasing Sampling Period 7000 6000 5000 PPM / Year 4000 3000 2000 1000 0 < 3 3 - 5 5 - 10 10 - 15 - 30 - 60 - 90 - 120 - 180 - 240 - > 365 15 30 60 90 120 180 240 365 Sampling Period Days

Simulation of a Constant PPM Delta Example of Fixed Delta / Increasing Sampling Period 10000 1000 PPM / Year 100 10 1 < 3 3 - 5 5 - 10 10 - 15 - 30 - 60 - 90 - 120 - 180 - 240 - > 365 15 30 60 90 120 180 240 365 Sampling Period Days

From Previous Presentation

Change of Perspective • So, let try to drop the notion of normalised rate (Trend) (PPM/day or PPM/year) • Let look at the ABSOLUTE difference (in PPM) between two samples (Delta) • Let group results by sampling period, as a few slides before • What do we have ?

Delta PPM CH 4 Absolute Change Week Month Quarter Half Year CH 4 Year 2 Years 3 Years Long

CH 4 Absolute Change 95 Percentile Absolute Change VS Sampling Interval 120 100 80 Delta (ppm) 60 40 20 All samples 0 Week Month Quarter Half Year 1 Year 2 Years 3 Years Long Sampling Interval

CH 4 Absolute Change • Ratio has been reduced by a factor of 100 • A lot more manageable !! • The use of absolute variation between consecutive samples, without day or year normalisation, give more uniform results and is simpler to use • What else could we learn from this data set ?

CH 4 Gas Level in PPM 90 Percentile PPM 400 10 9 350 8 % Samples > Condition 4 300 90 Percentile PPM 7 250 6 200 5 4 150 All samples 3 100 2 50 1 0 0 Week Month Quarter Half Year 1 Year 2 Years 3 Years Long Sampling Interval

CH 4 Gas Level in PPM Percentage of Samples above condition 4 120 10 9 100 8 % Samples > Condition 4 7 80 Delta (ppm) 6 60 5 4 40 3 2 20 1 0 0 Week Month Quarter Half Year 1 Year 2 Years 3 Years Long Sampling Interval

CH 4 Absolute Change 95 Percentile Absolute Change and % of Samples above Condition 4 120 10 PPM Change between samples 9 100 % Samples > Condition 4 8 7 Delta (ppm) 80 Percentage of points 6 With CH4 in Condition 4 60 5 4 40 3 2 20 1 0 0 Week Month Quarter Half Year 1 Year 2 Years 3 Years Long Sampling Interval

CH 4 Absolute Change 95 Percentile Absolute Change VS Sampling Interval 120 All Points 100 80 Delta (ppm) Points Condition 4 Removed 60 40 20 0 Week Month Quarter Half Year 1 Year 2 Years 3 Years Long Sampling Interval

CH 4 Absolute Change 95 Percentile Absolute Change VS Sampling Interval 120 All Points 100 80 Delta (ppm) Points Condition 4 Removed 60 Points Condition 3 & 4 Removed 40 20 0 Week Month Quarter Half Year 1 Year 2 Years 3 Years Long Sampling Interval

CH 4 Absolute Change 95 Percentile Absolute Change VS Sampling Interval 120 100 All Points 80 Delta (ppm) Points Condition 4 Removed 60 Points Condition 3 & 4 40 Removed 20 Points Condition 2 & 3 & 4 Removed 0 Week Month Quarter Half Year 1 Year 2 Years 3 Years Long Sampling Interval

Other Gas • H 2 , C 2 H 4 and C 2 H 2 have the same type of distribution • CO and CO 2 form a different group • C 2 H 6 and TDCG are between the two groups

Other Gas • “Type I” • Short Term Rate Higher than long term • Short Term Level Higher than long term – Hydrogen – Methane – Eyhylene – Acethylene

Delta PPM H 2 Absolute Change Week Month Quarter Half Year H 2 Year 2 Years 3 Years Long

H 2 Absolute Change 95 Percentile Absolute Change VS Sampling Interval 450 10 9 400 8 % Samples > Condition 4 350 7 300 Delta (ppm) 6 250 5 200 4 150 3 100 2 50 1 0 0 Week Month Quarter Half Year 1 Year 2 Years 3 Years Long Sampling Interval

Delta PPM C 2 H 4 Absolute Change Week Month Quarter Half Year C 2 H 4 Year 2 Years 3 Years Long

C 2 H 4 Absolute Change 95 Percentile Absolute Change VS Sampling Interval 120 14 100 12 % Samples > Condition 4 80 10 Delta (ppm) 8 60 6 40 4 20 2 0 0 Week Month Quarter Half Year 1 Year 2 Years 3 Years Long Sampling Interval

Delta PPM C 2 H 2 Absolute Change Week Month Quarter Half Year C 2 H 2 Year 2 Years 3 Years Long