TRANSFORMER CONDITION ASSESSMENT Project No: File: MUMI 1_1083100A0002 Page 1 of 12 DOBLE ENGINEERING AFRICA TRANSFORMER DIAGNOSTIC TESTING AT MUMI 1 SUBSTATION This report was prepared on the10 th June 2014 by: Kamendren Govender Principal Engineer CLIENT: MATREX
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TRANSFORMER CONDITION ASSESSMENT
Project No: File: MUMI 1_1083100A0002 Page 1 of 12
DOBLE ENGINEERING AFRICA
TRANSFORMER DIAGNOSTIC TESTING AT MUMI 1 SUBSTATION
This report was prepared on the10th June 2014 by:
Kamendren Govender
Principal Engineer
CLIENT: MATREX
TRANSFORMER CONDITION ASSESSMENT
Project No: File: MUMI 1_1083100A0002 Page 2 of 12
REPORT DETAILS
CLIENT Matrex ADDRESSEE
SITE MUMI 1 Substation JOB DESCRIPTION Transformer Condition Assessment REPORT PREPARED BY Kamendren Govender DATE REPORT COMPLETED 10th June 2014 REPORT AUTHORISED BY Luwendran Moodley CLIENT ORDER NUMBER QS1405-19
Indemnity This document may not be distributed or used outside the client for whom it is prepared except with written authorization from Doble. Doble disclaims all liability for any loss damage injury or other consequence whatsoever arising from any unauthorized use howsoever caused including any such resulting from error omission or negligence in its application.
TRANSFORMER CONDITION ASSESSMENT
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Table of Contents 1. Executive Summary...............................................................................................4
2.1. Transformer Details ..........................................................................................5 2.2. Condition Analysis ...........................................................................................5 2.2.1. Electrical Test Findings ......................................................................................5 2.2.2 Oil Test Findings .............................................................................................. 12
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1. Executive Summary
1.1. Findings
Doble Engineering Africa was requested by Mutanda Mining Company to perform diagnostic tests and analysis on a transformer based on electrical tests. This report covers the final findings based on our studies of the transformer with serial number: 1083100A0002 manufactured by Hangzhou-Qiantang-River-Electric-Group and located at MUMI 1 Substation. The winding power factor and capacitance results are within acceptable limits.
The bushing power factor and capacitance results are within acceptable limits.
The excitation currents are within acceptable limits.
The ratio test revealed no significant concerns with all ratios being within the acceptable limits. The impedance results are within acceptable limits. The DC winding resistance tests results are within acceptable limits. The insulation resistance test are within acceptable limits. The SFRA indicated no winding deformation on both the HV and LV Winding.
1.2 Recommendations The transformer demonstrates acceptable test results and may be suitable for continued service with routine maintenance and diagnostic testing.
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2. Analysis and Observations
2.1 Transformer Details
The transformers details are given in Table 1.
Table 1: Transformers Details
Substation MUMI 1 Substation Unit T2
Serial Number 1083100A0002 Manufacturer Hangzhou-Qiantang-River-Electric-Group
Year of Manufacturer 2008 Voltage 120/22 kV
VA Rating 24 MVA
2.2 Condition Analysis
2.2.1 Electrical Test Findings
2.2.1.1 Windings Insulation
Results and Analysis The winding power factor values are given in Table 2.
Table 2: Winding Power Factor and Capacitance Test Results
Measured Voltage (kV) Power Factor (%) Capacitance (pF)
HV winding to earth 10 0.22 2 750.48 Between HV and LV winding 10 0.17 3 837.77 LV winding to earth 10 0.16 6 881.44
All winding power factor and capacitance results are within acceptable limits. 2.2.1.2 Bushing Insulation Results and Analysis The bushing power factor and capacitance results are given in Table 3.
Table 3: Bushing Power Factor and Capacitance Test Results
The excitation currents are within acceptable limits.
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2.2.1.4 Ratio Test Results and Analysis
The results of the ratio test for each phase and tap position shall be within ± 0.5 % of the nameplate data. The results from the ratio tests are given in Table 5.
a) HV Winding
Table 5: Ratio Test Results
Tap A Phase B Phase C Phase Min Max
1 3.31 3.31 3.31 3.29 3.32
2 3.27 3.27 3.27 3.25 3.28
3 3.23 3.23 3.23 3.21 3.24
4 3.19 3.19 3.19 3.17 3.20
5 3.15 3.15 3.15 3.13 3.16
6 3.11 3.11 3.11 3.09 3.12
7 3.07 3.07 3.07 3.05 3.08
8 3.03 3.03 3.03 3.01 3.04
9 2.99 2.99 2.99 2.97 3.00
10 2.95 2.95 2.95 2.93 2.96
11 2.91 2.91 2.91 2.89 2.92
12 2.87 2.87 2.87 2.85 2.88
13 2.83 2.83 2.83 2.82 2.84
14 2.79 2.79 2.79 2.78 2.80
15 2.75 2.76 2.75 2.74 2.76
16 2.71 2.72 2.72 2.70 2.73
17 2.67 2.68 2.68 2.66 2.69
The ratio measurements are within acceptable limits. 2.2.1.5 Impedance Test
Results and Analysis The impedance test results are shown in Table 6. HV to LV: Three Phase Equivalent Tests
Table 6: HV to LV: Three Phase Equivalent Test Results
Tap Nameplate Impedance
(%) Measured Impedance
(%) Change in Impedance
(%)
1 10.3 10.37 0.66
5 10 10.08 0.85
17 9.2 9.82 6.69
The impedance results are within acceptable limits.
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2.2.1.6 DC Winding Resistance
Results and Analysis The DC winding resistance tests were performed on all windings and are shown on Tables 7 and 8. a) HV Winding
1 75.82 75.81 75.84 The DC winding resistance test results are within acceptable limits 2.2.1.7 Insulation Resistance Results and Analysis The insulation resistance test results are given in Table 9.
Table 9: Insulation Resistance Test Results
Measure Test Result
Core – Earth 19.6 GΩ The insulation resistance test results are within acceptable limits.
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2.2.1.8 SFRA Test
Results and Analysis The results from the SFRA tests are given in Figures 1 to 3.
a) HV Winding Open Circuit
Figure 1: HV Winding Open Circuit
Note: The deviation of the middle phase (white phase or B phase) in the lower frequencies is normal due to the difference in the reluctance of the core for the middle phase compared to the two outside phases. The comparison between the phases finds that the responses demonstrate a characteristic pattern and has good correspondence across the entire frequency range. These responses do not indicate winding deformation.
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b) LV Winding Open Circuit
Figure 2: LV Winding Open Circuit
Note: The deviation of the middle phase (white phase or B phase) in the lower frequencies is normal due to the difference in the reluctance of the core for the middle phase compared to the two outside phases. The comparison between the phases finds that the responses demonstrate a characteristic pattern and has good correspondence across the entire frequency range. These responses do not indicate winding deformation
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c) HV Winding Short Circuit
Figure 3: HV Winding Short Circuit
The short circuit response revealed no resistance change between the phases. These responses do not indicate winding deformation.
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2.2.2 Oil Assessment a) Oil Quality i) Moisture Content The moisture content (9 ppm) is within acceptable limits. ii) Dielectric Strength The dielectric strength (69 kV) is within acceptable limits. iii) Acidity The acidity (0.01) is within acceptable limits. b) Paper Degradation
The concentration of the paper degradation product of furans measured in oil is 0.06ppm, which relates to a degree of polymerization (DP) of 824 respectively. The furan level suggests the normal paper aging.
c) Dissolved Gas Analysis The only DGA sample is indicative of a normal operating transformer. This is shown in Figure 4.