Читать книгу Alternative Liquid Dielectrics for High Voltage Transformer Insulation Systems - Группа авторов - Страница 62
2.6.1.2 Doernenburg Ratio Method
ОглавлениеThis technique uses the four ratios R1, R2, R3, and R4 for diagnostics of faults in the transformer. In this method, it is primarily determined whether a fault exists in the transformer by examining the quantity of each gas associated to a minimum concentration limit L1 as given in Table 2.7. There is a fault in the transformer if any of the gases from H2, CH4, C2H2, and C2H4 exceeds double the recommended limit L1 and the quantity (ppm) of any one of the other two gases (C2H6 and CO) exceeds this limit L1. This procedure is reliable only if the quantity of at least one of the gases in each ratio exceeds the limit value, otherwise oil samples may be again collected for repeated analysis. If the ratio analysis is valid, then each successive ratio is compared in the order of R1, R2, R3, R4 and the fault type is ascertained as given in Table 2.8.
Table 2.5 IEC gas ratios.
| Gas ratio | Value | Code |
|---|---|---|
| R2 = C2H2/C2H4 | R2 < 0.1 | 0 |
| 0.1≤ R2 ≤ 3 | 1 | |
| R2 > 3 | 2 | |
| R1 = CH4/H2 | R1 < 0.1 | 1 |
| 0.1≤ R1 ≤ 1 | 0 | |
| R1 > 1 | 2 | |
| R5 = C2H4/C2H6 | R5 < 1 | 0 |
| 1≤ R5 ≤ 3 | 1 | |
| R5 > 3 | 2 |
Table 2.6 Types of faults.
| No. | Type of fault | Code | ||
|---|---|---|---|---|
| R2 | R1 | R5 | ||
| 1 | No fault | 0 | 0 | 0 |
| 2 | Partial Discharge with low energy density | 0 | 1 | 0 |
| 3 | Partial Discharge with high energy density | 1 | 1 | 0 |
| 4 | Discharge (arc) with low energy | 1→2 | 0 | 1→2 |
| 5 | Discharge (arc) with high energy | 1 | 0 | 2 |
| 6 | Thermal faults of temperatures < 150 °C | 0 | 0 | 1 |
| 7 | Thermal faults of temperatures between 150 and 300 °C | 0 | 2 | 0 |
| 8 | Thermal faults of temperatures between 300 and 700 °C | 0 | 2 | 1 |
| 9 | Thermal faults of temperatures >700 °C | 0 | 2 | 2 |
Table 2.7 Doernenburg gas ratio method.
| Key gases | Minimum concentration L1 (ppm) |
|---|---|
| Hydrogen (H2) | 100 |
| Methane (CH4) | 120 |
| Carbon monoxide (CO) | 350 |
| Acetylene (C2H2) | 1 |
| Ethylene (C2H4) | 50 |
| Ethane (C2H6) | 65 |
Table 2.8 Types of faults by Doernenburg ratio method.
| No. | Type of fault | R1 | R2 | R3 | R4 |
|---|---|---|---|---|---|
| 1 | No fault | Conc. (H2 or CH4 or C2H2 or C2H4)>2L1 and Conc. (C2H6 and CO) <L1] or [Conc. (H2 or CH4 or C2H2 or C2H4)< 2L1] | |||
| 2 | Thermal decomposition | R1 > 1 | R2 < 0.75 | R3 < 0.3 | R4 > 0.4 |
| 3 | Low‐intensity partial discharge | R1 < 0.1 | R2 = ND | R3 < 0.3 | R4 > 0.4 |
| 4 | High‐intensity arcing | 0.1 < R1 < 1 | R2 > 0.75 | R3 > 0.3 | R4 < 0.4 |
