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Advancements in Dissolved Gas Analysis: CO/CO2 Ratio

For DGA interpretation, faults identified using hydrocarbon gases are considered more serious if they appear to affect paper insulation. That is made explicit in CIGRE technical brochure 771[1]. Production of hydrocarbon gases from the oil by electrical or thermal stress does not significantly...

Advancements in Dissolved Gas Analysis: NEI & Gassing Events

One of the most important steps when looking at DGA data is to decide whether the data support the existence of a fault that is actively breaking down the insulation before you try to use a triangle, pentagon, or gas ratio method to identify a fault type. Otherwise, you are diagnosing random...

Utility Transformers

transformer repair

Radiator Fin(s) Leak Repair

Radiator fins are notorious for leaking at various locations. One of which is where the fins are attached (welded) to the horizontal bottom-run header. Measurements are taken so a weir box can be installed to cover the fin(s) that are leaking. It is preferred the weir box will cover above the leaking area about 6".
This 6” cover will allow for urethane (poured into weir box) to adhere to the drier part of the fin(s) to assist with the sealing process. After pour, the technician will mark the outside of the weir box at the location(s) where the original leak was. This incase further work may be required for a better seal. After the urethane is poured and let to cure (usually overnight) the job is inspected to determined seal effectiveness. In the event we still have some leakage; whether the following day or later, an additional procedure may be performed. If leaking, the weir box is fabricated out of 11ga galvanized sheet metal which is thick enough for completing a 1/16" NPT. The technician will decide where (usually where it's been marked) and how many 1/16" D&T’s (drill & taps) are required. Once additional d&t's are completed, injection valves installed, then a special 2-part sealant (must be approved from a dielectric and DGA standpoint) will be injected. The thought is: now that there is cured urethane above the original leak(s) and we have marked the weir box for injecting close to that spot, we have created a bridging barrier for our sealant to back up against (so as not to extrude out the top of the weir box).

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Advancements in Dissolved Gas Analysis: NEI & Gassing Events

One of the most important steps when looking at DGA data is to decide whether the data support the existence of a fault that is actively breaking down the insulation before you try to use a triangle, pentagon, or gas ratio method to identify a fault type. Otherwise, you are diagnosing random...

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Case Study: Rapid Changes in Bushing Health

IntroductionContinuous online monitoring of bushings provides real-time information which can result in the early detection of a possible failure. Challenge: A Major AlarmA prominent U.S. utility was looking for a way to improve system reliability for their 138kV assets. They researched and...

Protection of Electrical Power Transformers

INTRODUCTIONIn most large electrical systems, generators and power transformers are the two most expensive pieces of equipment. In addition to the capital cost of purchase, these two key devices are also the most critical to continuous and reliable operation of the system.Consider, for example, the...


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