valco aluminium ae69700t1

TRANSFORMER CONDITION ASSESSMENT

Project No: File: Valco Aluminium_AE69700T1 of 10

DOBLE ENGINEERING AFRICA

TRANSFORMER DIAGNOSTIC TESTING AT VALCO ALUMINIUM

This report was prepared on the 25th May 2015 by:

Kamendren Govender

Principal Engineer

CLIENT: VALCO ALUMINIUM



REPORT DETAILS

CLIENT Volta Aluminium Company Limited

ADDRESSEE

SITE Line 5

JOB DESCRIPTION Transformer Condition Assessment

REPORT PREPARED BY Kamendren Govender

DATE REPORT COMPLETED 25th May 2015

REPORT AUTHORISED BY Luwendran Moodley

CLIENT ORDER NUMBER

Copyright © 2007 Doble Engineering Africa Limited

All rights reserved. No part of this publication may be produced stored in a retrieval system or transmitted in any form by any means electronic mechanical photocopying recording or otherwise without the prior written permission of Doble.

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.



Table of Contents 1. Executive Summary...............................................................................................4

1.1. Findings ..............................................................................................................4 1.2. Recommendations ..............................................................................................4 2. Analysis and Observations ......................................................................................5

2.1. Transformer Details ..........................................................................................5 2.2. Condition Analysis ...........................................................................................5 2.2.1. Electrical Test Findings ......................................................................................5



1. Executive Summary

1.1. Findings

Doble Engineering Africa was requested by Valco Aluminium 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: AE69700T1 manufactured by Fuji Electric and located at Line 5. The power factor results are high and not within acceptable limits. This is indicative of insulation contamination.

The ratio test revealed no significant concerns with all ratios being within the acceptable limits. The DC winding resistance tests results are within acceptable limits. The Sweep Frequency Response Analysis (SFRA) revealed no winding deformation on the 13.8/16.4 kV windings for all phases. The moisture content is within acceptable values. The DGA signature is indicative of a normal operating transformer.

1.2 Recommendations Given the findings, Doble Engineering Africa recommends the following: Furan measurements to assess the condition of the insulation Annual monitoring of winding power factor results



2. Analysis and Observations

2.1 Transformer Details

The transformers details are given in Table 1.

Table 1: Transformers Details

Substation Line 5

Unit VR5

Serial Number AE69700T1

Manufacturer Fuji Electric

Year of Manufacturer 1968

Voltage 13.8/16.4 kV

VA Rating 93.5 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)

S, L, and SL to ground 8 1.05 38 134.00

The power factor results are high and not within acceptable limits. This is indicative of insulation contamination.



2.2.1.2 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 4.

a) S Winding to L Winding

Table 4: Ratio Test Results

Tap Red Phase Yellow Phase Blue Phase

67 1.001 1.002 1.002

The ratio measurements are within acceptable limits. 2.2.1.3 DC Winding Resistance

Results and Analysis The DC winding resistance tests were performed on all windings and are shown on Tables 5 and 6.

a) S Winding

Table 5: S DC Winding Resistance Test Results


Resistance (m) Resistance (m) Resistance (m)

67 15.01 14.76 14.76

The DC winding resistance is within acceptable limits. b) L Winding

Table 6: L DC Winding Resistance Test Results


Resistance (m) Resistance (m) Resistance (m)

67 18.03 17.91 17.92

The DC winding resistance test results are within acceptable limits.



2.2.1.4 SFRA Test

Results and Analysis The results from the SFRA tests are given in Figures 1 to 3.

a) S Winding Open Circuit

Figure 1: S Winding Open Circuit

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.



b) S Winding Short Circuit

Figure 2: S Winding Short Circuit

The short circuit response revealed no resistance change between the phases. These responses do not indicate winding deformation.



c) L Winding Open Circuit

Figure 3: L Winding Open Circuit

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.



2.2.1.5 Oil Analysis

a) Moisture Content The moisture content (16 ppm) is at acceptable values.

b) DGA

Figure 4 below shows the DGA history of the oil.

Figure 4: DGA Signature

The DGA signature is indicative of a normal operating transformer.

valco aluminium ae69700t1

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