BS EN 60599:1999:2007 Edition
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Mineral oil-impregnated electrical equipment in service. Guide to the interpretation of dissolved and free gases analysis
| Published By | Publication Date | Number of Pages |
| BSI | 2007 | 30 |
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 1 | BRITISH STANDARD BS EN 60599:1999 IEC 60599: 1999 Mineral oil-impregnated electrical equipment in service – Guide to the interpretation of dissolved and free gases analysis |
| 2 | This British Standard was published under the authority of the Standards Committee and comes into effect on 15 June 1999 National foreword |
| 3 | EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN 60599 +A1 Supersedes HD 397 S1:1979 English version Mineral oil-impregnated electrical equipment in service Guide to the interpretation of dissolved and free gases analysis (IEC 60599:1999) |
| 4 | Foreword Endorsement notice Foreword to amendment A1 Endorsement notice |
| 5 | Contents |
| 6 | Introduction 1 Scope 2 Normative references 3 Definitions and abbreviations 3.1 Definitions 3.1.1 fault NOTE In electrical equipment, a fault may or may not result in damage to the insulation and failure of the equipment. 3.1.2 non-damage fault NOTE Typical examples are self-extinguishing arcs in switching equipment or general overheating without paper carbonization. 3.1.3 damage fault 3.1.4 incident NOTE Typical examples are gas alarms, equipment tripping or equipment leakage. 3.1.5 failure |
| 7 | NOTE In the electrical equipment, failure will result from a damage fault or incident necessitating outage, repair or replacement of the equipment, such as internal breakdown, rupture of tank, fire or explosion. 3.1.6 electrical fault 3.1.7 partial discharge NOTE 1 Corona is a form of partial discharge that occurs in gazeous media around conductors which are remote from solid or liquid insulation. This term is not to be used as a general term for all forms of partial discharges. NOTE 2 X-wax is a solid material which is formed from mineral insulating oil as a result of electrical discharges and which cons… NOTE 3 Sparking of low energy, for example because of metals or floating potentials, is sometimes described as partial discharge but should rather be considered as a discharge of low energy. 3.1.8 discharge (disruptive) NOTE 1 Discharges are often described as arcing, breakdown or short circuits. The more specific following terms are also used: NOTE 2 Depending on the amount of energy contained in the discharge, it will be described as a discharge of low or high energy, based on the extent of damage observed on the equipment (see 5.2). 3.1.9 thermal fault NOTE Typical causes are 3.1.10 typical values of gas concentrations NOTE 1 Typical values will differ in different types of equipment and in different networks, depending on operating practices (load levels, climate, etc.). NOTE 2 Typical values, in many countries and by many users, are quoted as “normal values”, but this term has not been used here to avoid possible misinterpretations. 3.2 Abbreviations 3.2.1 Chemical names and symbols 3.2.2 General abbreviations |
| 8 | 4 Mechanisms of gas formation 4.1 Decomposition of oil 4.2 Decomposition of cellulosic insulation 4.3 Other sources of gas |
| 9 | NOTE The case of gases formed at a previous fault and remnant in the transformer is dealt with in 5.3. 5 Identification of faults 5.1 Dissolved gas compositions 5.2 Types of faults 5.3 Basic gas ratios |
| 10 | NOTE 1 In some countries, the ratio C2H2/C2H6 is used, rather than the ratio CH4/H2. Also in some countries, slightly different ratio limits are used. NOTE 2 The above ratios are significant and should be calculated only if at least one of the gases is at a concentration and a rate of gas increase above typical values (see clause 9). NOTE 3 CH4/H2 < 0,2 for partial discharges in instrument transformers. CH4/H2 < 0,07 for partial discharges in bushings. NOTE 4 Gas decomposition patterns similar to partial discharges have been reported as a result of the decomposition of thin oil film between over-heated core laminates at temperatures of 140 °C and above (see 4.3 and [1] of Annex C). a NS = Non-significant whatever the value. b An increasing value of the amount of C2H2 may indicate that the hot spot temperature is higher than 1 000 °C. NOTE Combinations of gas ratios which fall outside the range limits of Table 2 and do not correspond to a characteristic fault of this table may be considered a mixture of faults, or new faults which combine with a high background gas level (see 6.1). In such a case, Table 2 cannot provide a diagnosis, but the graphical representations given in Annex B may be used to visualize which characteristic fault of Table 2 is closest to the case. The less detailed scheme of Table 3 may also be used in such a case in order to get at least a rough distinction between partial discharges (PD), discharges (D) and thermal fault (T), rather than no diagnosis at all. 5.4 CO2/CO ratio |
| 11 | 5.5 O2/N2 ratio 5.6 C2H2/H2 ratio NOTE If contamination by gases coming from the OLTC is suspected, interpretation of DGA results in the main tank should be done with caution by substracting background contamination from the OLTC, or should be avoided as unreliable. 5.7 C3 hydrocarbons 5.8 Evolution of faults 5.9 Graphical representations 6 Conditions for calculating ratios 6.1 Examination of DGA values a) Values of 0 4l/l on a DGA report or below the analytical detection limits S shall be replaced by “below the S value for this gas” (see IEC 60567 for recommended S values) b) If successive DGA analyses have been performed over a relatively short period of time (days or weeks), inconsistent variations (e.g. brutal decreases of concentrations) may have to be eliminated as an indication of a sampling or analytical problem. |
| 12 | c) Gas ratios are significant and should be calculated only if at least one gas concentration value is above typical value and above typical rate of gas increase (see note 2 of Table 2 and clause 9). d) If gas ratios are different from those for the previous analysis, a new fault may superimpose itself on an old one or normal … NOTE In the case of air-breathing power transformers, losses occur very slowly with time by diffusion through the conservator or… 6.2 Uncertainty on gas ratios 7 Application to free gases in gas relays |
| 13 | NOTE Data given in this table represent mean values obtained on some of the current types of transformer mineral insulating oils… 8 Gas concentration levels in service 8.1 Probability of failure in service 8.1.1 General 8.1.2 Calculation methods |
| 14 | 8.2 Typical concentration values 8.2.1 General 8.2.2 Calculation methods 8.2.3 Choice of normality percentages 8.3 Alarm concentration values 8.4 Rates of gas increase |
| 15 | NOTE In the case of carbon oxides, rates of gas increase are dependent on the oil-to-paper ratio, which may be quite different depending on the equipment considered. 9 Recommended method of DGA interpretation (Figure 1) a) Reject or correct inconsistent DGA values (see 6.1). Calculate the rate of gas increase since the last analysis, taking into account the precision on DGA results. b) Determine if gas concentrations and rates of gas increase are above alarm values. Verify if fault is evolving towards final stage (see 5.8). Determine if paper is involved (see 4.2 and 5.4). c) Take proper action according to best engineering judgment and/or with the help of Figure 1. 1) increase sampling frequency (quarterly, monthly or other) when the gas concentrations and their rates of increase exceed typical values, 2) consider immediate action when gas concentrations and rates of gas increase exceed alarm values. 10 Report of results NOTE The report should be adapted to the specific type of equipment considered. a) DGA analysis report, including S values, method of DGA analysis, and date of analysis. NOTE Values of 04l/l on a DGA report or below the S values are replaced by “below the S value for this gas”. b) specific information on the equipment such as: 1) date of commissioning, voltage, general type (e.g. power or instrument transformer), rated power; 2) special features (e.g. sealed or air-breathing, type of OLTC [see A.1.6)]; 3) oil volume; 4) oil or gas sampling date; 5) oil or gas sampling location; c) special operations or incidents just before and after the oil or gas sampling, such as tripping, gas alarm, degassing, repair, outage; d) previous DGA on the equipment; e) indication of typical values for this specific equipment, if known; f) indication of “Typical DGA/healthy equipment” or “Fault”; g) in case of “Fault”, identification of the fault using Table 2 (see 5.3), with values of the calculated gas ratios indicated; h) indication of paper involvement or not, with value of the CO2/CO ratio; i) recommended actions: 1) new frequency of oil sampling, 2) furanic compound analysis if CO2/CO ratio is lower than 3, 3) other tests. |
| 16 | NOTE For power transformers, see also A.1.5. Figure 1 – Flow chart |
| 18 | NOTE 1 Any gas formation below typical values of gas concentration and rates of gas increase should not be considered as an indication of “fault”, but rather as “normal gas formation”. Ratios are not significant in such a case (see note 2 of Table 2). NOTE 2 In the case of air-breathing power transformers, losses of gas occur very slowly with time by diffusion through the conse… Table A.2 – Ranges of 90 % typical gas concentration values observed in power transformers, in µl/l |
| 19 | Table A.3 – Ranges of 90 % typical rates of gas increase observed in power transformers (all types), in µl/l/year NOTE OLTCs are often composed of a selector switch, located in the oil of the main tank, and of a diverter switch, located in a separate tank but on the same operating axle. |
| 20 | NOTE The values listed in this table were obtained from one particular network. Values on other networks may differ. a The data are influenced by the design and assembly of the on-load tap changer. For this reason, no statistically significant value can be proposed for acetylene. NOTE Definitions of these specific sub-types can be found in [6] of Annex C. |
| 21 | NOTE 1 The values listed in this table were obtained from one particular network. Values on other networks may differ. NOTE 2 The value for H2 in CTs is much lower for rubber sealings (± 20 4l/l) than for metal sealings (± 300 4l/l). |
| 22 | NOTE PD = partial discharges NOTE Some modern bushings contain mixtures of mineral oil and dodecylbenzene (DDB), in proportions not known. Gas compositions evolved from DDB are not the same as from mineral oil, and DDB absorbs more gas than mineral oil. |
| 23 | NOTE These values are examples taken from one particular network. Values on other networks and with different types of cable designs may differ. NOTE 1 In this table are given examples of faults detected by DGA of oil samples taken from the switching compartment. NOTE 2 Switching equipment attached to transformers is complex and of various designs. The detailed description of these systems… |
| 24 | NOTE 1 The arrow indicates increasing temperature. NOTE 2 The axes are limited to values of 10 for clarity of presentation, but actually extend to unlimited values. The coordinates of each zone are the same as in Table 2 and Figure B.2. Figure B.1 – Graphical representation 1 of gas ratios (see [3] of Annex C) |
| 25 | NOTE 1 Each of the cases defined in Table 2 is represented by a volume or “box” on the 3-D graphic. NOTE 2 The coordinates of each box are the same as in Figure B.1 and Table 2. It is more convenient to use this representation with the help of a computer software package. Figure B.2 – Graphical representation 2 of gas ratios (see [4] of Annex C) |
| 26 | Figure B.3 – Graphical representation 3 of gas ratios-Duval’s triangle (see [5] of Annex C) |
| 28 | NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies. |
| 30 | BS EN 60599:1999 IEC 60599: 1999 |
