Power Transformer Components Research Articles

Risk Priority Evaluation for Power Transformer Parts Based on Intuitionistic Fuzzy Preference Selection Index Method

The risk assessment of power transformer equipment can not only improve the safety and management level of transformer operation, but also reduce the operation and maintenance costs of the equipment on the basis of ensuring the overall reliable operation of the power system. As a result, it can enhance the rewards of assets investment. The quantitative analysis of power equipment risk often contains qualitative indicators that are difficult to quantify. These indicators have the characteristics of fuzziness. In order to improve the accuracy and reliability of risk assessment results, this paper proposed a new risk evaluation method based on intuitionistic fuzzy set. Firstly, language variables are transformed into corresponding intuitionistic fuzzy numbers. Secondly, a novel entropy of intuitionistic fuzzy set is established. Thirdly, a weighting method for determining each expert’s importance is proposed based on the new propose entropy. Furthermore, an extended preference selection index is put forward under intuitionistic fuzzy environment. Finally, an example of the risk assessment of power transformer components is discussed to illustrate the effectiveness of the new risk evaluation method.

REDUCTION of STRAY LOSS COMPONENT of POWER TRANSFORMER in ANSYS MAXWELL to OPTIMIZE the LOAD LOSS by USING DIFFERENT MAGNETIC MATERIALS

REDUCTION of STRAY LOSS COMPONENT of POWER TRANSFORMER in ANSYS MAXWELL to OPTIMIZE the LOAD LOSS by USING DIFFERENT MAGNETIC MATERIALS

A New Criterion for Optimal Dielectric Design of High Voltage Bushing Internal Shields in Large Power Transformer

The High Voltage (HV) bushings are the most sensitive components of power transformers, they provide electrical insulation between the HV line and grounded tank, and also provide necessary mechanical support. The majority of transformer breakdowns are attributed to the HV bushings failures which are graded with conductive layers to improve their dielectric strength. The design of bushings is quite challenging with tradeoff between the axial and radial electric stresses. The bushing design is also governed by its mounting angle and transformer tank configuration to meet the internal and external flashover clearances and creepage requirements. At higher voltage levels, the configuration of HV bushing shield and grounded structural components have significant impact on dielectric withstand strength other than the clearances. Hence, it is very important to study the electrode configuration inside transformer tank for a particular bushing mounting arrangement before finalizing the bushing internal shield design. The 3D electrostatic field analysis of high voltage generator transformer was carried out for different bushing shield configurations to evaluate the electric stress distribution and the dielectric breakdown strength of the equipment was verified experimentally. The authors recommend to study the dielectric design of transformer in tandem with transformer configuration and a new evaluation criterion for optimal design of bushing internal shield is proposed.

Failure analysis of power transformer for effective maintenance planning in electric utilities

In this paper, power transformer failures are analyzed and their root causes are systematically investigated in Tamil Nadu Transmission Corporation Limited (TANTRANSCO)/Tamil Nadu Generation and Distribution Corporation Limited (TANGEDCO) electric utilities, based on 196 failure cases from the year 2009–2013. Failure analysis is conducted in two phases. Initially, voltage level, geographical zone and power transformer components based failure analysis are performed through statistical analysis. Secondly, the most significant factors that cause power transformer failures are identified by using root cause analysis (RCA). Finally, current maintenance practice is reviewed and an effective maintenance planning has been proposed for implementation in order to prevent these failures and to maintain the power transformers in good operating condition during their life cycle. This study provides a practical guidance to help maintenance personnel for the best utilization of the power transformer in electric utilities.

Probabilistic model for planning keeping of power transformer spare components with general repair time distribution

The paper suggests a method to optimize the quantity of spare power transformer components. The presented sparing policy is conceived to provide minimum annual cost consisting of expected capital cost for spares, failures renewal and load curtailment costs. The method identifies minor and major failures. Power transformer is a complex system, consisting of six components (functional parts). It is assumed that each component has two independent, competing failure modes: wear-out failure mode, modeled by two-parameter Weibull distribution, and a chance failure mode, characterized by an exponential distribution. Duration of failure renewal is not a deterministic variable. It is assumed that failure state residence time of each power transformer component is Weibull distributed (renewal times of power transformer components may follow any probability distribution, Weibull distribution being only a special case).The application of the method suggested and the benefits it provides are demonstrated for one transformer station (TS) 110/xkV/kV with 2×31.5MVA transformers in case of radial supplying of customers and when outage of one power transformer does not affect customers supplying. In addition, the influence of power transformer refurbishment on expected total cost has also been analyzed.

Determining power transformers' sequence of service in power grids

Utilities need to ensure power grids that are highly reliable and cost-efficient as well. Periodic replacement assures reliability but causes high replacement costs. Thus, it is much better to keep power transformers as long as possible in a functional condition and ensure reliability by adequate service (maintenance and repair). Cost-efficient service requires a sequence of service of power transformers. The sequence can be defined according to some criteria that need to be tracked in course of time. The paper introduces service classes and the risk of an outage as criteria. Service classes and risk are defined according to the condition and function of power transformer's components. The paper focuses on the insulation system, which is one of the most important power transformer components. For the inspection of this component the paper introduces dissolved gas analysis and oil characteristics to find insulation system's defects and aging, respectively. For the interpretation of measurements two new interpretation methods are applied, one for dissolved gas analysis and one for the oil characteristics. They overcome certain limits while they map measurements to different defects and aging conditions. The interpretation methods are presented from a user's point of view. Literature is given for a more in depth presentation of the underlying concepts. The service concept will finally be applied to a group of power transformers that belong to a transmission system operator.

Optimal spares availability strategy for power transformer components

The paper suggests a method to optimize the spare amount of power transformer components. The proposed strategy is conceived to provide minimum annual cost consisting of expected failures renewal cost, capital cost for spares and load curtailment cost. The method identifies minor and major failures. Minor failures are repairable, while major failures can be repairable or unrepairable. Power transformer is a complex system, consisting of six components (functional parts). It is assumed that each component has two independent, competing failure modes: wear-out failure mode, modelled by two-parameter Weibull distribution, and a chance failure mode, characterized by an exponential distribution. The application of the method suggested and the benefits it provides are demonstrated for one transformer station (TS) 110/ x kV/kV with 2 × 31.5 MVA transformers. In addition, the influence of performing power transformer refurbishment on expected total cost has also been analyzed.