Methanol: A Novel Approach to Power Transformer ... - IEEE Xplore

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IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 27, NO. 2, APRIL 2012

Methanol: A Novel Approach to Power Transformer Asset Management Jocelyn Jalbert, Senior Member, IEEE, Roland Gilbert, Yves Denos, and Pierre Gervais

Abstract—All electrical utilities deal with the task of determining the residual life of their in-service power transformers. Given the difficulties experienced with the use of first and second generations of markers (carbon oxides and 2-furfuraldehyde), several organizations are now considering the use of methanol for this purpose. Hydro-Québec, which discovered this approach, uses this molecule on a regular basis to evaluate the state of the cellulose insulation of in-service power transformers and applies it to Électricité de France’s nuclear power plant transformers. In this paper, some examples of the application of methanol in the field are presented against the information received from the early marker generations. Index Terms—Asset management, carbon oxides, cellulose degradation, insulating paper, methanol, 2-furfuraldehyde, residual life.

I. INTRODUCTION HE END OF THE useful life of an in-service transformer strongly correlates to the degree of its insulation paper degradation. Concerning the diagnosis of transformer internal insulation, the first efforts focused on the use of CO and CO , quantified by dissolved gas analysis (DGA) analysis, for the detection of faults occurring in the paper or oil components. However, the situation is more complex with respect to useful life due to the potentially long aging time an apparatus may experience ( 20 years). For example, in open breathing transformers, the presence of a sufficient amount of oxygen is favorable to the generation of CO/CO from the oil and the paper degradation processes, with the paper moisture being a parameter of prime importance [1]. Moreover, in open-breathing transformers, the carbon oxides can escape from the systems and completely disappear during operations, such as oil degassing or regeneration; the low solubility of CO/CO in the insulation paper compared to the one

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Manuscript received July 07, 2010; revised February 10, 2011, April 13, 2011, May 19, 2011, December 13, 2011; accepted January 22, 2012. Date of publication March 06, 2012; date of current version March 28, 2012. This work was supported in part by Hydro-Québec TransEnergie and in part by Electricité de France. Paper no. TPWRD-00515-2010. J. Jalbert is with the Institut de recherche d’Hydro-Québec (IREQ), Varennes, QC J3X ISI Canada (e-mail: [email protected]). R. Gilbert, retired, was with the Institut de recherche d’Hydro-Québec, Varennes, QC J3X ISI Canada. Y. Denos was with Electricité de France (EDF R&D) Themis Group, Clamart 92141, France. He is now with the ENERBAT Department, Monet sur Loing 77818, France (e-mail: [email protected]). P. Gervais, retired, was with Hydro-Québec TransEnergie, Montreal, QC H5B 1H7 Canada. Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TPWRD.2012.2185957

in the oil [2] prevents marker re-equilibration in the oil, after which its correlation with the insulation paper degradation becomes meaningless. Since a transformer most likely experiences some maintenance work during its useful life and some leaks may be observed in sealed transformers, the use of the CO/CO content to detect or predict the end of useful life becomes highly questionable. An alternative approach consists in considering a family of furan compounds, especially 2-furfuraldehyde (2-FAL), more specifically linked to paper insulation breakdown [3], though many drawbacks have to be taken into account. In particular, the presence of a very small amount of 2-FAL for thermally upgraded insulation paper (TU paper) renders its detection a laborious process [4], [5]; the high production rate from hemicelluloses compared to cellulose [6], the thermal instability of the compound [7], and the effect of moisture on the rate of production [5] are among the concerns utilities are facing. Consequently, the use of 2-FAL as a chemical marker for establishing the remaining life of cellulose insulation is under scrutiny by the scientific community. Recently, the use of methanol (CH OH) has been reported for the first time in the literature by Jalbert et al. [8] for estimating the degree of cellulose insulation degradation. Laboratory tests showed that methanol is mainly produced during the aging of oil-impregnated paper insulation at 60 C–120 C (inhibited naphthenic oil under air), regardless of whether the specimens are thermally upgraded. This work revealed the existence of a direct relationship between CH OH production and the scission of 1,4-ß-glycosidic bonds (bonds that link the cellulose glucose units). Moreover, methanol was detected in the aging tests in the early scissions of the bonds even at temperatures as low as 60 C. More recently, a kinetics study carried out by the same research group on standard-Kraft paper (std) [9] and on TU-Kraft paper [10] showed that depolymerization and methanol production required an activation energy of about 104 kJmol , thus confirming the link between the two processes. Moreover, the production of methanol and broken cellulose chains showed about the same value for the of the Arrhenius expression, which inexponential factors troduces the possibility that the rate of production of CH OH from chopped chains is much higher than the rate of depolymerization, so that the latter becomes the rate determining step of the overall reaction. This means that contrary to the 2-FAL, the methanol is instantaneously produced after the opening of the 1,4-ß-glycosidic bonds and, consequently, detected early in the oil. These authors also demonstrated the role played by oxygen and moisture on the exponential factors as obtained from the application of different degradation models: pseudozero Ekenstam’s rate constants [11], first-order time-dependent decrease

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JALBERT et al.: METHANOL: A NOVEL APPROACH TO POWER TRANSFORMER ASSET MANAGEMENT

of k [12], power law [13], and single first-order evolution equation [14] by comparing paper aging in naphthenic oil under air with paper aging in uninhibited paraffinic oil under nitrogen. Finally, the oil of different pieces of equipment from HydroQuébec’s grid (e.g., transformers, shunt reactors, current transformers) was sampled and assessed for CH OH and 2-FAL. The results showed that methanol is detected in more than 94% of the 900 units studied, compared to 56% for 2-FAL. In this survey, the data showed a marked decrease in 2-FAL concentrations around the 1970s, which corresponded to the introduction of TU-Kraft paper in Hydro-Québec’s equipment [8]. In addition, to demonstrate the advantages of methanol over the earlier generations of markers, another thorough survey was conducted by comparing all of the molecules (methanol, carbon oxides, and 2-FAL) in oil samples collected from about 290 power transformers currently operated by EDF. A comparison of the assessed concentrations was used to establish the limits of each marker. This paper reviews some of the results obtained from these field surveys.

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TABLE I INSTRUMENTAL CONDITIONS FOR THE HSGC/MS ANALYSIS OF METHANOL

II. EXPERIMENTAL Transformer Oil Sampling: The transformer oil samples were collected on load in accordance with the ASTM D 923 test method or IEC 60475 (the oil temperature was noted during the sampling). One aliquot sample was sent to an external laboratory for DGA and moisture analysis while the remaining volume was used at IREQ for the CH OH and 2-FAL measurements. Apparatus and Methods: A G1888 static headspace sampler, coupled with a 6890N gas chromatograph equipped with a 5973N mass selective detector at 70-eV ionization energy in the electron impact mode (all from Agilent Technologies), was used to assess the methanol. The instrument interface was main300 amu, in a tained at 250 C and a mass range 0.21-s cycle, was scanned in total ion count mode (TIC). The separation was performed with a 60-m-long Stabilwax (Restek) polar column, 0.25 mm in diameter and with 0.5- m film thickness; the instrumental conditions are given in Table I. The signal was calibrated by injecting a series of dilutions prepared from a mother solution of methanol in oil at a maximum concentration level of 10 ppm (w/w) (6-point calibration curves). Quantification was carried out in the selected ion monitoring (SIM) mode. 2-FAL was assessed using high-performance liquid chromatography (Agilent Technologies, 1100 Series). The signal was calibrated (6-point calibration curves) by injecting a series of dilutions prepared from a mother solution of 2-furfuraldehyde in oil at a maximum concentration of 2.5 ppm (w/w). The carbon–oxide content was obtained by an external laboratory using a normalized technique, such as ASTM D 3612 Method C or IEC 60233. III. RESULTS AND DISCUSSION A. Survey of Field Transmission Transformers The difficulty associated with transmission transformers arises from the fact that their loads are not constant (i.e., the internal temperature varies) and, in addition, they may have been offload many times while in service. For this reason, the paper insulation aging may be poorly related to service time.

Fig. 1. Insulation transformer life curve using methanol.

Fig. 1 illustrates the signal intensity of the methanol content in oil versus the effective service time of transmission power transformers of known average loading. The -axis corresponds to in years as defined elsewhere [15] the effective service time (1) where Y is the number of years in service and L is the average operating load factor. This relationship enables a comparison on the same basis of equipment operating under different load levels. For example, the of a 10-year-old apparatus operating under 100% of its rated load is 10 years (e.g., applicable to generator transformers) while that of a 10-year-old apparatus at 50% of its rated load is 5 years (e.g., applicable to transmission-line transformers). The use of methanol data in conjunction with DGA diagnosis makes it possible to identify the units affected by an abnormal paper aging rate. Some points illustrated in Fig. 1 correspond to equipment with signs of low energy arcing or hot spots during operation according to DGA measurements, most likely with/without any insulating paper problems. For example, the six data points corresponding to the very large signal intensity values of the methanol content (note the break in the Y axis)

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Fig. 3. Comparison of the three markers on substation transformers. Fig. 2. Diagnosis of paper damage using methanol in the CT.

point to the presence of hot spots at the paper level from DGA measurements. The presence of abnormal cellulose aging was further supported by cooling problems which were manifested during several days for the equipment under consideration. However, the present approach used for the diagnosis of power transformers may not be extrapolated to current transformers (CTs). For the latter, no significant load is generally observed, which means that the correlation with methanol is irrelevant, as illustrated in Fig. 2. signal intensity and As expected, the signal intensity in relative units is very low for CTs compared to those for the power transformers, and no particular trends may be conducted for these systems. The only cases showing a significantly higher content for methanol are those where a corona discharge or a hot spot is present, suggesting that paper damage occurred in these CTs (see Fig. 2). These examples show the applicability of methanol for detecting paper aging in different pieces of equipment. Finally, Fig. 3 presents a comparison of the relative concentrations of the three markers under consideration as obtained from the units of a given substation. (Each unit’s in-service year is given at the top of the respective bar graph.) The concentrations were normalized by adjusting the maximum concentration to 100%. These core-open-breathing transformers were from different manufacturers, with some units equipped with TU-Kraft paper (units #1, 3, and 9). As expected, all of the markers show a quantitative response for the apparatus in operation from 1961 to 1962 (units #2, 5, 7, and 8) equipped with standard-Kraft paper. For unit #2, the carbon oxides are characterized by a high value compared to the levels found for the other markers; this behavior can be explained by the fact that these oxides could also be produced from oil oxidation (acidity of 0.1 mg KOH/g of oil). For the unit in service in 1967 (unit #4), which shows marginal amounts of both CH OH and carbon oxides, the use of TU-paper cannot be confirmed. But the fact that 2-FAL is not detected indicates that this unit probably contains TU-paper. The other apparatus equipped with TU-paper shows

Fig. 4. Whisker plot key parameters.

a certain amount of methanol and carbon oxides with only one in which a very small amount of 2-FAL is quantified. In the latter case, the involvement of board aging has to be considered. B. Survey of Power Plant Transformers Contrary to the previous case, power plant transformers operate at close to 100% of their rated load. This characteristic allows for a direct comparison of the concentration measured in the oil samples of the units. A thorough comparison using the three chemical markers (CO CO , 2-FAL, and CH OH) was established for the 290 transformers currently in operation in EDF’s nuclear power plants. One-hundred sixty-nine step-up transformers operating cover are among these units. under an Each apparatus with a given configuration (shell or core type) is considered to exhibit almost the same characteristics as the others. However, there is a significant difference between the two types of configurations in terms of the amount of insulating materials involved (paper, board, and oil). The main characteristics of the transformers under investigation are given in Table II. The labels correspond to the type of configuration (S for shell and C for core) and the average effective service time . Due to the narrow age distribution of the apparatus, a statistical approach is used to compare the transformers. A Whisker plot graphical representation illustrates the key values of the summary statistics, with these values being defined in Fig. 4 [16]. In


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TABLE II CHARACTERISTICS OF THE TRANSFORMERS INVESTIGATED

this study, the units are consider outliers when they are outside the 5th and 95th percentile. To facilitate the comparison between the two types of transformer configurations, based on the total amount of oil and cellulose (paper board) for each type, the amount of marker measured was then standardized per weight of total cellulose (i.e., milligrams of marker per kilogram of total cellulose). Moreover, in order to take into account the solubility in this paper of each marker at the operating temperature, the data were normalized as follows: In the case of carbon oxides, the normalization was obtained by applying equations taken from [2] for the solubility of the species with the temperature (2) (3) oil temperature in C, ppm of CO where in the sample at 80 C, of CO in the sample at T, ppm of CO in the sample at 80 C and of CO in the sample at T. In the case of 2-FAL, it is stated in the previously cited [2] that there is no significant temperature effect on the solubility between 55 C–100 C and then, the total amount of 2-FAL generated by the cellulose could be estimated as 6.7 times its value measured in the oil. This factor takes into account the partition of 2-FAL between the oil and the paper. Finally, the amount of methanol lost by the paper due to its partition in the oil was evaluated in our laboratory using the following procedure. A total of 81 20-mL ampoules was prepared by inserting a piece of 0.5 g of paper and 8-mL solution of 1 ppm (w/w) of CH OH in oil. These ampoules were sealed under air and distributed in equally in three forced-air ovens operating at 40 C, 60 C, and 80 C. Three ampoules were removed from the ovens after varied lengths of equilibration time and then stabilized for 3 h at 20 C to equilibrate all of the systems at a given temperature. After the seal was broken, an aliquot portion of oil was transferred into a 10-mL headspace vial for the determination of the CH OH. Fig. 5 shows the equilibrium reached for the three temperatures investigated (each data point corresponds to the average of three analyses). Under these experimental conditions, the methanol equilibrates very rapidly (24 h) compared to 2-FAL (30 days) [2]. The amount of methanol at equilibrium is 4.3 times less than what it was initially in the oil (100/23.3%) and, as observed for 2-FAL, is independent of the temperature investigated. This latter value was used to further normalize all of the CH OH data. The Whisker plots of the normalized data obtained for the configurations listed in Table II are reproduced in Fig. 6. First,

Fig. 5. Equilibrium of methanol versus temperature.

in the case of the carbon oxides, no major discrepancy in the data was noted for transformers with an average of 13 7 to 25 3 years. However, the comparison of the distributed data points for each configuration (shell versus core) is very similar: the shell type displays a normal distribution of data compared to the core type, where two groups of data can be noted. Notwithstanding the difference in the operating temperature and , this marker seems to indicate that the paper degradation of these transformers is almost of the same extent regardless of the configuration (shell versus core). Second, compared to the carbon oxides, the 2-FAL data analysis shows a very different trend. As expected, the data obtained for the transformers isolated with 100% TU paper (S13) showed the lowest level of markers, and the data are on a narrow range, which suggests that these transformers did not age significantly. However, a survey conducted on a decommissioned unit of this family showed that contrary to the indication received from the 2-FAL, paper and board have been aged with the degree of polymerization (DP ) values as low as 525 and 875, respectively. On the other hand, based on data collected from our laboratory tests on this type of paper [10], these results suggest that 2-FAL mainly originates from insulation board aging. If we compare the other 2-FAL data distributions for a compa(22 4 versus 25 3 years), the paper insulation of the rable shell-type transformers operating at 360 MVA seems to degrade to a lesser extent than the core type; given that the operating temperature of the shell-type transformers is higher, this result is surprising unless the absorption of the 2-FAL compounds by the boards results in apparent lower concentrations. This is taken into account. Moreover, even if there is a significant difference between core-type transformers operating at 360 and in the versus 16 3 years), the distributions are sim550 MVA ( ilar, except for the outliers. Finally, a comparison of the methanol concentrations with the different transformer configurations showed a mix of what was observed with the carbon oxides and the 2-FAL data analysis. Knowing that TU- and standard-Kraft paper generate methanol, it is not surprising to note a lower average concentration for

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TABLE III OUTLIERS IDENTIFIED WITH A WHISKER COEFFICIENT OF 0.5 ( 90 PERCENTILE)

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On the other hand, lower concentrations were surprisingly noted with methanol for the 360-MVA core-type transformers 24.7 3.2 years) compared to the 550-MVA equivalent ( 16 3 years). This suggests that the materials design ( are more thermally involved in the 550-MVA transformers compared to the 360-MVA units. Note that the same behavior is also observed for the carbon oxides. These results illustrate the need to compare pieces of equipment of the same configuration (i.e., core data should not be compared directly with shell data) as mentioned previously [17]. For a better comparison, it is also important to obtain the amount of materials involved (paper/board/oil) in order to standardize the data. Finally, an empirical model based on the methanol concentrations with average transformer DP could be developed by taking the paper and board DP distributions into account. C. Outlier Comparison

Fig. 6. Comparison of the cellulose marker statistics on EDF’s power plant transformers.

550-570-MVA shell-type transformers ( years) compared to 360-MVA shell-type transformers. However, for ( versus years), the approximately the same average concentration of the shell-type transformer (square dot on the Whisker graph) is higher than what is observed with the core type, probably due to the highest operating temperature attributed to this configuration.

After the characterization of the entire transformer families, it is important to determine the units needing special attention. This could be approached by identifying the units from each family distribution that correspond to the higher concentrations for the three markers studied. Using this approach and a Whisker coefficient of 0.5, it is possible to pinpoint transformers that need particular attention. Table III summarizes the statistics for the transformers studied. Based on this table, methanol exhibits the maximum number of outliers, particularly for the shell type. The units of this configuration are known to be used to a greater extent. It is interesting to note that this trend is confirmed only by methanol, which is most likely due to the high sensitivity of this marker to the cellulose-chain scissions. In particular, if one compares the transformer outliers identified by each marker, only I1TP0 is common for the three different markers in the case of the 550–570-MVA shell-type transformers (100% TU Kraft). For 360-MVA shell-type transformers (100% std Kraft), five transformers are common for three different markers (K1TP4, K2TP8, L2TP0, L2TP4, and L2TP8) from which those from site L are known to be overloaded. For the two core-type transformers (10% TU Kraft: 90% std Kraft), no common outliers are found for the three markers.


TABLE IV RECOVERY OF MARKERS AFTER OIL PROCESSING

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ACKNOWLEDGMENT The authors would like to thank L. Brossard for his revision and helpful contribution in the drafting of this paper as well as P. Tétreault, B. Morin, and S. Duchesne from IREQ for their technical assistance. REFERENCES

IV. OIL REGENERATION One important parameter is the marker’s capability, after oil regeneration, to rapidly re-equilibrate with the oil in order to diagnose the degree of paper insulation degradation. The “memory” of the paper degradation is only possible with 2-FAL and CH OH due to the high concentrations remaining in the paper insulation. This parameter was investigated for methanol and 2-FAL on three core-type transformers where oil regeneration with degassing was applied. The concentrations in the oil of these markers after varied lengths of time following regeneration are summarized in Table IV. This table demonstrates the capability of the regeneration process to remove more than 90% of the 2-FAL and 80% of the CH OH from the oil. After three months of oil processing, 20% and 80% of the initial concentration of 2-FAL and CH OH, respectively, is then restored in the oil phase. Finally, after approximately six months, the 2-FAL has not reached 30% of its initial concentration compared to 90% and more for the CH OH. The values of more than 100% are tentatively attributed to the high aging of the cellulose in these transformers. These findings have some consequences on the ability of electrical utilities to closely monitor their transformers. Based on these data, it is assumed that after processing the oil of a given unit, it will take more than one year to recover close to the initial concentration of 2-FAL in the oil compared to half the time for methanol.

V. CONCLUSION These practical examples from in-service transformers showed the universal application of methanol as a marker for evaluating paper aging. The principle advantage of this molecule over 2-FAL is its ability to be generated in the presence of TU paper regardless of the temperature and the moisture present in the insulation. It could readily be used to sort out the problematic units of a given family and technology. In addition, contrary to carbon oxides, because of its high affinity for the paper, methanol will tend to re-equilibrate in the oil after the latter has been regenerated. This is a major step for electrical utilities seeking, namely, to determine whether a given unit should be refurbished or replaced. This research project allowed Hydro-Québec and Électricité de France to begin using the methanol marker for managing their fleet of transformers.

[1] G. C. Stevens and A. M. Emsley, “Review of indicators of degradation of cellulosic electrical paper insulation in oil-filled transformers,” Proc. Inst. Elect. Eng., Sci. Meas. Technol., vol. 141, no. 5, pp. 324–334, Sep. 1994. [2] K. Hisao, M. Teruo, M. Yoshihiro, N. Sadao, and H. Takashi, “Absorption of CO and CO gases and furfural in insulating oil into paper insulation in oil-immersed transformers,” presented at the IEEE Conf. Rec. Int. Symp. Elect. Insul., Pittsburgh, PA, Jun. 5–8, 1994. [3] P. J. Burton, M. Carballeira, M. Duval, C. W. Fuller, J. Graham, A. De Pablo, J. Samat, and E. Spicar, “Application of liquid chromatography to the analysis of electrical insulating materials,” presented at the CIGRE Conf., Paris, France, 1988, paper 15-08. [4] P. J. Griffin, L. R. Lewand, and B. Pahlavanpour, “Paper degradation by-products generated under incipient-fault conditions,” presented at the Doble Eng. Conf., Boston, MA, 1994, Paper 10-5.1. [5] L. E. Lundgaard, W. Hansen, D. Linhjell, and T. J. Painter, “Aging of oil-impregnated paper in power transformers,” IEEE Trans. Power Del., vol. 19, no. 1, pp. 230–239, Jan. 2004. [6] J. Scheirs, G. Camino, M. Avidano, and W. Tumiatti, “Origins of furanic compounds in thermal degradation of cellullosic inslulation paper,” J. Appl. Polymer Sci., vol. 69, pp. 2541–2547, 1998. [7] D. M. Allan and C. F. Jones, “Thermal-oxidative stability and oil-paper partition coefficients of selected model furan compounds at practical temperatures,” presented at the 9th Int. Sysmp. High Voltage Eng, Graz, Austria, 1995. [8] J. Jalbert, R. Gilbert, P. Tétreault, B. Morin, and D. Lessard-Déziel, “Identification of a chemical indicator of the rupture of 1,4- -glycosidic bonds of cellulose in an oil-impregnated insulating paper system,” Cellulose, vol. 14, pp. 295–309, 2007. [9] R. Gilbert, J. Jalbert, P. Tétreault, B. Morin, and Y. Denos, “Kinetics of 1,4-ß-glycosidic bonds rupture in cellulose and correlation with methanol formation during ageing of paper/oil systems. Part 1: Standard wood kraft insulation,” Cellulose, vol. 16, pp. 327–338, 2009. [10] R. Gilbert, J. Jalbert, P. Tétreault, B. Morin, and Y. Denos, “Kinetics of the production of chain-end groups and methanol from the depolymerization of cellulose during the ageing of paper/oil systems. Part 2: Thermally-upgraded insulating papers,” Cellulose, vol. 17, no. 2, pp. 253–269, 2009. [11] A. Ekenstam, “The behavior of cellulose in mineral acid solution: Kinetic study of the decomposition of cellulose in acid solutions,” Ber Deutschen Chem Geselllschaft, vol. 69, no. 553, 1936. [12] A. M. Emsley, R. J. Heywood, M. Ali, and C. M. Eley, “On the kinetics of degradation of cellulose,” Cellulose, vol. 4, pp. 1–5, 1997. [13] P. Calvini, “The influence of leveling-off degree of polymerization on the kinetics of cellulose degradation,” Cellulose, vol. 12, pp. 445–447, 2005. [14] H. Z. Ding and Z. D. Wang, “On the degradation evolution equations of cellulose,” Cellulose, vol. 15, pp. 205–224, 2008. [15] A. Keiichi, M. Teruhiko, S. Toshiomi, and U. Tokihiro, “Sensing system for degradation diagnosis of oil-filled transformers,” in Proc. IEEE Int. Symp. Elect. Insul. Conf. Rec., Jun. 5–8, 1994, pp. 29–32. [16] OriginLab Corporation. Northampton, MA, Origin Pro. [17] Y. Denos, A. Tanguy, P. Guunic, J. Jalbert, R. Gilbert, and P. Gervais, “Ageing diagnosis by chemical markers: Influence of core-type and shell-type technology,” presented at the CIGRE, Paris, France, Aug. 2010. Jocelyn Jalbert (SM’09) was born in Canada in 1967. He received the B.Sc. degree in chemistry and the M.Sc. degree in analytical chemistry from Université de Montréal, Montréal, QC, Canada, in 1990 and 1992, respectively, and the Ph.D. degree in energy and materials from the Institut National de la Recherche Scientifique—Énergie et Matériaux, Varennes, QC, Canada, in 2009. He joined Hydro-Québec’s Research Institute, Varennes, in 1992, where his main contributions were taking part in the development and normalization of a headspace method for dissolved gas analysis, and the assessment of trace amounts of moisture in transformer oil. More recently, he headed a major project on insulating paper degradation. Dr. Jalber is a member of the ASTM D27 Committee.

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Roland Gilbert was born in Canada in 1946. He received the M.Sc. and Ph.D. degrees in physical chemistry from Université de Montréal, Montréal, QC, Canada, in 1971 and 1974, respectively. He joined Hydro-Québec’s Research Institute (IREQ), Varennes, QC Canada, in 1973 under an industrial postdoctoral scholarship from the Natural Sciences and Engineering Research Council of Canada. In 1977–1978, he was assigned to Chalk River Nuclear Laboratories (CRNL), Chalk River, ON, Canada, where he was involved in nuclear power plant decontamination and steam generator chemical cleaning. During his career at IREQ, he was responsible for the scientific aspects of a wide range of research activities: chemical analysis and physico-chemical phenomena related to nuclear power plant operation, chemical treatment of distribution wood poles, and chemistry of transformer insulating materials. He has authored and co-authored more than 100 papers and patents in these different fields of expertise.

Yves Denos was born in France in 1966. He received the M.Sc. and Ph.D. degrees in energy and materials from the Institut National de la Recherche Sci-


entifique—Énergie et Matériaux, Varennes, QC, Canada, in 1991 and 1994, respectively. He was with Hydro-Québec. Varennes, QC, Canada, from 1990 to 1996, working on fuel-cell material characterization, followed by Gaz de France (1996–2004), France, and Electricité de France, France (since 2004) in the field of power generation and material aging.

Pierre Gervais was born in Canada in 1949. He received the B.Sc. and M.Sc. degrees in physical chemistry from Université de Montréal, Montréal, QC, Canada. He was with Hydro-Québec’s, Varennes, QC Canada, substation maintenance division from 1978 to 1985, then from 1985 to 1992, followed by Hydro-Québec TransÉnergie, Montreal, as a Specialist in the diagnosis of transformer insulation materials.