1

Saving Asset Life - DGA on LTC

2

DISSOLVED GAS ANALYSIS

■ Oil is the Life Blood of a Transformer

■ Like a blood sample, oil samples attempt to determine condition

3

DISSOLVED GAS ANALYSIS

■ Industry practice to use DGA for Transformer condition assessment

■ First IEEE Standard Formed in 1978 as C57.104

4

DISSOLVED GAS ANALYSIS

CAN THIS ASSESSMENT TOOL BE APPLIED FOR LOAD TAP

CHANGERS?

5

DGA on LTC

■ First introduction into Epcor in 2009 for trending

■ Discussion in the industry on adopting this as

standard for testing

■ IEEE standard was

created in 2010 –

C57.139

6

Garneau Substation Incident

■ Garneau Substation - 72kV 6

breaker ring bus with 3

transformers serving the

University Area

■ Garneau TX1 Details

■ 30/40 MVA Ferranti Packard

Transformer built in 1981

■ Load Tap Changer Type 25RT32

7

Garneau Incident and Investigation

DGA Test Results Received in August 2009

Gas PPM

H2 13,386

CH4 132,436

C2H6 70,740

C2H4 441,806

C2H2 19,570

TDCG 678,289

■ Using Themography LTC was confirmed warmer than main tank

■ Next Scheduled Maintenance due in 2010

8

Garneau TX1

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Garneau TX1

10

Garneau TX1

11

Garneau TX1

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Garneau TX1

13

Garneau TX1

14

Garneau Incident and Investigation

DGA Test Results Received 6 months Later

Gas PPM

H2 453

CH4 147

C2H6 156

C2H4 1273

C2H2 1092

TDCG 3161

■ Discussing with Siemens – service announcement April 2003 offering

reversing switch upgrade kit

■ Made repairs to TX1, TX2, TX3

15

Garneau Conclusions and Recap

■ Opening compartment confirmed indications of problems in tap

changer

■ Discussion with Vendor from incident led to installing Reversing

Switch upgrade kit

■ DGA results in 2010 and after confirmed successful repair

■ Originally scheduled for maintenance 2010 – unsure if tap changer

would have failed.

16

Thank you for your time

Any Questions?