Removal of corrosive sulfur from by-products of sulfur combustion (C3) Uruguay 2010

seamarconi — Fri, 31 May 2013 14:51:16 +0000

Scenario

Uruguayan utility

October 2012: Failure 2 weeks after a reclaim treatment with fuller earth (performed by a local operator).

Nameplate data of the transformer:

Transformer: grid transformer with OLTC
Namufact.: xxx
Year: 1977
Power [MVA]: 425
Voltage [KV]: 500
Oil mass [Kg]: 58.000
Oil type: YPF65 paraffinic oil not inhibited

Evidence of electrical arc on the contacts of the selector

Analysis and diagnosis (by the holder)

The diagnosis of the holder, as a result of the field tests, presumed an high energy discharge in the main tank. Subsequently, after laboratory tests, was discovered a failure in the OLTC that produced a discharge in the transformer main tank.

The reclaim treatment with fuller earth made the oil aggressive towards the silver surfaces of the contacts.

Corrosion of the silver surface of the contacts

Analysis, diagnosis and expertise by Sea Marconi

Columns with reactivated earth (not used by Sea Marconi)

«At relatively high temperature, sulphur-containing oil molecules may decompose and react with metal surface to form metal sulphides» (IEC 60422 Ed. 4 – 2013 art. 5.17)

Sea Marconi calls this case as SCBP (Sulfur Combustion ByProducts) & Corrosive Sulfur.

“The oil regeneration process plant involves the high temperature reactivation of sorbent and fuller earth column by uncontrolled combustion. The Sulfur Compounds naturally present (DiBenzoThioPhene – DBTP, etc.) in the Oil and additives (DBDS, etc.) are decomposed in Sulfur Combustion ByProducts (such as corrosive H2S, Mercaptans, etc.) forming Sulphides CuS, Cu2S, Ag2S, etc.”. Ref. other case histories such as National Grid, ABB, etc.

	Analytical results
CCD	Corrosive
TCS DBDS Eq. [mg/Kg]	131
ASTM 1275 B	4C
DBTP [mg/Kg]	24
TAN [mg KOH/g]	0,01
DF	0,018
IFT [mN/m]	0,018

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Insulating oil treatments: “Sea Marconi Solution” vs “Fuller Earth treatments”

seamarconi — Tue, 16 Apr 2013 08:23:17 +0000

Benchmarking between the different techniques of oil treatment during the life cycle of oils and transformers

Download the flier PDF: Sea Marconi Treatments Vs Fuller Earth treatments ENG (377.5 KiB)

Key Factors	DMU & Integrated Treatments* Sea Marconi Patented	Treatment with typical Fuller Earth	Treatment with typical Fuller Earth and regeneration > 600-700 °C
Recovery: Physical Properties KV, DGA, H₂O	Yes	Yes	Yes
Recovery: Chemical Properties TAN, DF, IFT	Yes	Yes	Yes
Removal: DBDS & Corrosive Sulfur	Yes	No	No
Decontamination: Dissolved Metals	Yes	No	No
Dehalogenation: PCBs/POPs in Oils	Yes	No	No
Classification: BAT/BEP – Best Available Techniques/Best Environmental Practices (PCBs/POPs)	Yes	No	No
Self-cleaning unit from: DBDS, PCBs/POPs	Yes	No	No
Cross contamination by DBDS, PCBs/POPs	Safety	Danger	Danger
Corrosion by Sulfur Degradation byProducts (SDBP) as H₂S, Mercaptans, etc. due to high temperature (> 370 °C – typical 600-700 °C)	Safety	Safety	Danger
Dioxins Emissions (PCDDs, PCDFs) due to high temperature degradation byproducts from PCBs/POPs and halogenated contaminants in Oils	Safety	Safety	Danger

*CDP Process^® for PCBs/POPs chemical dehalogenation; CHEDCOS for DBDS & Corrosive Sulfur Selective Depolarization

Example of Case history: «C3 – SDBP & Corrosive Sulfur»

URUGUAY 2010

signs of electric arcs on tap selector contacts

Post Failure diagnosis on a Grid Transformer showed signs of electric arcs on tap selector contacts. The failure has been caused by the formation of Corrosive Sulphides as CuS, Cu2S, Ag2S, etc. Indeed «At relatively high temperature, sulphur-containing oil molecules may decompose and react with metal surface to form metal sulphides» (IEC 60422 Ed. 4 – 2013 art. 5.17). This mechanism started together with the oil regeneration process with reactivation of sorbent and fuller earth column by uncontrolled combustion (> 370 °C). The Sulfur Compounds naturally present (DiBenzoThioPhene – DBTP, etc.) in the Oil and additives (DBDS, etc.) are decomposed in Sulfur Degradation ByProducts. Other Ref. National Grid (UK), ABB (Sweden), 2010 Doble Conference (USA)

Sustainable Solutions by Sea Marconi – Added Value for Customers, Holders & Partners:

45 years of Innovation for Life Cycle Management of Oils & Transformers;
Solutions based on Global and Integrated Approach, Case histories, State of the Art, IEC Standards, CIGRE Guidelines, Stockholm Convention on POPs (Persistent Organic Pollutants);
Opportunity for prevention and/or mitigation of losses and risks for the asset, workers, public health and environment;
Focus on hot topics and priorities for strategic electrical equipment filled with insulating fluids;
Diagnosis (> 150,000 cases) and Integrated Treatments (> 700 Power Transfos – 2012) with DMU (25 Decontamination Mobile Units), guarantee independent expertise, reliability, quality control (ISO 9001-2008, ACCREDIA ISO 17025), traceability, economic benefits, environmental protection, social, stakeholders and insurance relationship.

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