Marian Ciontu

Congestion management using dispatch or phase shifting transformers

This paper deals with two categories of congestion management methods. The dispatch method is analyzed in two versions: static and differential, each one applied to outputs or to loads. The static method used the contributions to congesting flows, whereas the differential counts for the impact on flows before and after congestion management. The results for static and differential cost allocation are compared with the postal stamp. The development of FACTS devices and control techniques has provided efficient tools for dealing with congestion management. Phase shifting transformers are employed as a substitute method for dispatch. Two alternate locations are exemplified for managing congestion under a particular operation regime.

Preventive maintenance optimization for power transformers in use

The paper proposes a method for determining the optimal preventive maintenance intervals. It is highlighted the existence of a range for preventive maintenance actions which leads to minimizing the total cost of maintenance. For this purpose it is proposed to define a pre-defect state which allows the accumulation of the effects due to degradation of the transformer. At this state the transformer is still able to fulfill its functions but it should be mentioned that its parameters are worsening being close to the limits permitted by normative. The paper presents the main objective functions that can be used to optimize maintenance activity. In this article it is presented a study case which aims to optimize the preventive maintenance activities taking in consideration an extension of the transformers lifespan from 25 years to 40 years. Depending on the considered objective function the optimal maintenance interval may have different values. For the example presented in this paper, to obtain the minimum value for the failure rate and minimum value of the unavailability time it is recommended to perform maintenance every 6 months. In order to decrease the maintenance cost, the maintenance time interval should be equal with 13 months. The purpose of the preventive maintenance is to maintain the rate of failure at a low value, which characterizes the normal operation of the equipment. Therefore when a pre-defect state occurs the equipment is removed from service before the appearance of any serious damage.

Powering knowledge transfer at INCESA - BRIDGE projects

The movement of know-how or technical knowledge from one organization to another known as knowledge transfer in literature is considered to be one of the most important components of the strategic plan of a research institute. Despite the fact that INCESA (Research Hub of Applied Sciences, University of Craiova) is a young organization, it already counts an important number of collaborations with the local and regional business environment. Consequently, it is developing a management strategy that approaches the knowledge transfer (KT) to the industry as a recurrent event. The paper presents an overview of the KT to the industry as secured by INCESA. Two of the INCESAs KT-type projects financed by national grants and based on a partnership with the power distribution industry are the object of our analysis. The findings are used to refine the taxonomy of the KT channels in relation to INCESAs projects, and to feature a successful framework of the knowledge management at the micro level of the project, as well as at the meso-institutional level.

Symmetrical components based software for three-phase load flow analysis

This paper presents the principle of a load flow algorithm adjusted to asymmetrical operation of the three-phase distribution networks. The algorithm is based on an iterative procedure, which is independently applied on three equivalent sequence networks and uses a phase-to-phase equivalent model for unbalanced loads connected to the analyzed network.

Application Development to Convert Heterogeneous Information into PQDIF (Power Quality Data Interchange Format)

In this paper is presented a web-based application development, used to convert heterogeneous information provided by MEG40 (power acquisition equipment) into standard formats as PQDIF (Power Quality Data Interchange Format IEEE® Std 1159.3-2003 standard). The web-based solution proposed is able to convert huge volume of heterogeneous information into standard formats in order to be easily processed.

Simple control strategies of the active filters within a unified power quality conditioner (UPQC)

Unified power quality conditioner (UPQC) consists of combined shunt and series active power filters for improving both the power quality on the source side and on the load side. The paper presents a simple method for controlling the series filter under unbalanced and distorted load conditions by using a three phase locked loop (PLL). Two methods for controlling the shunt filter are analyzed. The model of the entire system is presented and considerations on the starting procedure are highlighted. The simulation is performed by using the Matlab-Simulink environment. The improvements of the power quality are analyzed by comparing the THD on the source side before and after use of the UPQC.

Simple control strategy of the series filter within a unified power quality conditioner

Unified power quality conditioner (UPQC) consists of combined shunt and series active power filters which acts both on the source side and on the load side for improving the power quality. The paper presents a simple method for controlling the series filter under unbalanced and distorted load conditions. The proposed control method is based on a three phase locked loop (PLL). For giving a complete approach of the UPQC, the control of the shunt filter is also presented. The whole system is then simulated. The results emphases on one hand a specific starting procedure and on the other hand the corrections of the power quality on the source side, by comparing the power factor and current THD before and after use of the UPQC. The simulation was performed by using the Matlab-Simulink environment.

Three-phase load flow analysis of the unbalanced distribution networks

This paper summarizes the results of a three-phase load flow analysis case study. This work was part of an overall energy systems modeling and analysis effort designed to develop a validated power flow study that facilitates understanding of power flow concepts for the present distribution networks operating in asymmetry conditions. To simplify data collection requirements and illustrate key concepts, a representative HV power distribution network with unbalanced loads was chosen for the study. The analysis methodology used in this illustrative case study and the lessons learned from the study could assist the grid operator in conducting power flow studies of operational areas of interest.

Assessment of reactive power related to users of transmission network

This paper deals with the assessment of reactive powers related to network users for payment and compensation purposes. The drawbacks are evaluated and compared with the benefits for voltage regulation, according to Romanian regulations. Theoretical skills are combined into one organic methodology, and an in-house software package for reactive power assessment is built. This is based on sensitivities of voltage, loss and transmission capacity to reactive injections into nodes. A case study consisting of a real 110kV network of about 2000 nodes was adopted. The results were used to evaluate the opportunities to compensate and/or to discharge payments the MVARs with positive contribution to voltage regulation.

Program for efficiency analaizing for variable speed drive of pumps

The present paper describe an original program elaborate by authors in order to analize the economic and energetic efficiency of using variable speed driven for turbo-pumps. The input dates of the program are represented by the parameters circuit hydraulic pump, the pump characteristics, motor drive, static frequency converter circuit and power supply. The program realise a comparative analysis of electricity consumption for flow through valve adjustment and changing speed for a curve given technical task. Starting from energy savings and the equipment cost it can be determined the payback of the investment. The paper presents a case study.