IEEE C57.140 pdf free download

IEEE C57.140 pdf free download. Evaluation and Reconditioning of Liquid Immersed Power Transformers.
4. Risk assessment
For the purpose of this guide, the term /ailur’ is defined as any unscheduled event of the transfbrmer and integrated (non-ancillary) accessories that requires the transformer to be removed from service for corrective action. A failure of an ancillary component or accessory might cause a relay to trip the transformer for reasons not relating to the transformer itself, and such a trip does not constitute a transformer failure according to the intentions of this guide. Because the decision to remove a transformer from service will vary with different users, users should create their own specific models based on the general models in this clause.
The term fimli as used in this clause is not restricted to the traditional electric utility usage, i.e., an unintentional phase-to-ground or phase-to-phase dielectric failure. Instead, in this clause, the term là,,!! may refer to a broader definition, such as a malfunction, defect, or indication of deteriorat ion of a component or accessory.
Evaluating and reconditioning of a liquid-filled transformer is not a trivial exercise. Dual objectives of meeting the growing demand of the electric power grid and maintaining system reliability may require significant changes in the way an owner operates and cares for its transformers. An emerging industry strategy is a life-cycle management program that sets loading priorities and provides owners with strategic direction for transformer assets. For the owner that has many transformers, it is usually not economically feasible to subject every aging transformer to a rigorous inspection and extensive testing. Thus, this asset management approach is typically a three-step process:
a) Priority screening of transformer fleet
b) Diagnostic testing
c) Condition assessment of individual transformers
Identifying and prioritizing an aging transformer population requires a screening process. The screening could be as simple as ranking the transformers by age. However, a more comprehensive screening can be accomplished with a risk assessment method. There are many different risk assessment methods and strategies available to the utility industry for a large family of power transformers. The method discussed here is a simple procedure called /àuIi tree analysis, which can help identify the transformers that need additional condition assessment, additional testing, and/or other actions for the purpose of bringing the entire population up to an acceptable risk level. Each transformer in a group can have a risk index to rank and compare other transformers on the company’s balance sheet.
The risk-based screening process uses statistical methods to identify and prioritize the transformers that represent the highest risk for the owner; however, this step does not identify the actual condition or the vulnerability of the individual transformers. Once the screening process has established a priority list, the next two steps in the process, diagnostic testing (see Clause 5), and condition assessment and reconditioning (see Clause 6), can help the owner establish a detailed asset management strategy. However, the list of variables and the individual utility circumstances that govern the technical and financial decision-making are such that it is impossible to establish an industry-wide set of rules or standards for managing the life cycle of aging transformers.
Transformers can be evaluated through the use of online monitoring and each system can be monitored to determine if it is functioning properly. IEEE Std C57. 143 is written to aid the engineer in detennining the proper tools to use to monitor the transformer. This guide should also be referred to when considering instrumentation to a reconditioned liquid immersed power transformer.IEEE C57.140 pdf download.