R.L. Vasquez-Arnez

Power Transmission Over Long Distances: Economic Comparison Between HVDC and Half-Wavelength Line

In this paper, the economics of some alternative solutions for point-to-point transmission of bulk power over long distances, namely, HVDC and half-wavelength lines (HWLL), are evaluated. Also, the main technical aspects of the half-wave length transmission technology in order to define the line design and its required equipment are discussed. A two-line, 2500 km transmission system (which is half the wavelength of a 60 Hz power frequency) carrying 6000 MW is used as the base case to perform the comparison. Finally, issues related to the sensitivity of such a cost comparison between the HVDC and HWLL alternative is presented.

A methodology for electrical energy forecast and its spatial allocation over developing boroughs

Spatial load forecasting is not an accurate subject, yet it is important for the future safe operation of a distribution system. In this paper, a methodology for spatial load forecasting based on the combination of aerial images with statically procedures applicable to developing boroughs, is presented. The core of the study underlies in the adjustment and construction of the S-curves of both saturated and non-saturated small areas. The proposed methodology is validated through the energy forecast and its spatial allocation over a pilot borough.

Compensation strategy of autotransformers and parallel lines performance, assisted by the UPFC

In this paper, reactive power compensation through the tertiary winding of an autotransformer, is proposed. Such an approach emerges as an alternative to support the significant voltage variation present over two parallel connected autotransformers, in the South Eastern Brazilian system. The above proposal will also help in controlling the line voltage variation due to the UPFC series converter action. A detailed steady-state analysis of the series voltage and the shunt reactive current when supporting line voltage, is realized. Such analysis is based upon the d-q coordinates. The UPFC effect over an uncompensated parallel line, is also studied. The waveform simulations performed to control each transformer terminal voltage, were obtained utilising the ATP/EMTP program. Results concerning the effectiveness of the autotransformer tertiary winding reactive power injection by the UPFC shunt converter, as well as the load flow control over the referred transformers, are also presented.

Steady-state multiline power flow control through the generalized IPFC (interline power flow controller)

The interline power flow controller (IPFC) is one of the newest devices within the FACTS group. By utilizing this device, an enhanced controllability over independent transmission systems or those lines whose sending-end are connected to a common bus can be obtained. As an extended version of the UPFC (unified power flow controller), the IPFC appears as an excellent solution for the control of multiline systems, but it also presents its own complexities whilst operating under certain system conditions. The steady-state response and performance of a generalized IPFC controlling two independent AC systems, is in this paper evaluated. None-the-less, the study can be extended to systems having more than two transmission lines. In order to observe its dynamic behavior and simultaneously validate the previous steady-state analysis, an IPFC model was also built in the ATP program. The results obtained validated the IPFC model built and ratified its capability for controlling the power flow over the compensated transmission lines.

Tap-Off Power From the Overhead Shield Wires of an HV Transmission Line

In recent years, there was an increase of ancillary service loads, such as signaling systems, inspection robots, surveillance cameras, and other monitoring devices distributed along high-voltage transmission lines which require low-power dc voltage supplies. This paper investigates the use of the induced voltage in the shield wires of an overhead 525 kV transmission line as a primary power source. Since phase current variations throughout the day affect the induced voltage in the overhead ground wire, a step-down dc-dc converter is used after rectification of the ac voltage to provide a regulated dc output voltage. The initial encouraging results obtained indicate that this form of power supply can be a feasible and cost-effective alternative for feeding small ancillary service loads. The simulation results are validated by field measurements as well as the installation of a 200 W voltage stabilization system prototype.

Preventive inspection of line insulators through corona emission: A case study

This paper presents the main results regarding the presence of corona on 138 kV lines. Although the study and analysis was mainly focused on the obtention of corona activity through a UV camera, results stemming from an IR camera will also be presented. The substitution of suspected flawed insulators represent to most of the distribution utilities one of the causes of major concern. The results performed in both a HV laboratory and field tests are presented herein. It was not found a similar behaviour and intensity of the corona activity between both cases. However, both type of tests agreed in that the faulty insulator(s) that have its leakage current increased, does not show corona activity.

Tap-off power from a transmission line shield wires to feed small loads

In this article, the feasibility to obtain power from the shield wires of a transmission line, as a result of the electromagnetic induction effect, will be presented. The phase conductors of the considered transmission line are horizontally arranged each having a quadruple bundle configuration. The transmission line used during the study operates at 525 kV. The results obtained showed that this form of power generation can be a feasible and cost-effective alternative for feeding small loads along a transmission line when compared to other forms of electricity supply. In order to obtain the highest induced current some shield conductor configurations were analyzed. The simulation tool used for analyzing the electromagnetic induction was the Alternative Transients Program (ATP).

The Interline Power Flow Controller: Further aspects related to its operation and main limitations

The IPFC (interline power flow controller) is among the FACTS devices aimed at simultaneously controlling the power flow in multiline systems. This paper presents the IPFC main features and limitations whilst controlling the power flow. In order to observe these advantages and disadvantages, a mathematical model based on the d-q orthogonal coordinates was developed. Issues like the relationship between the transmission angle and the IPFC controlled region as well as the converters operative region in steady-state will also be presented.

On the analysis and evaluation of a transmission line upgrading assisted by line arresters

The upgrading of transmission lines has shown to be an attractive alternative regarding the increasing demand of power and the difficulties for constructing new lines. In this paper, the study performed for upgrading an essential transmission line located in an industrial area at the SE region of Brazil will be presented. As the region where the line is located presents a high isokeraunic level, a set of TLAs (Transmission Line Arresters) have been also installed in the referred line. The installation of TLAs has the aim of coping with both lightning and switching surges within the upgraded line. As in a first stage not all the towers will have TLAs, a study for choosing the most appropriate towers will also be presented.

Fault current limitation using thyristor based devices

This paper presents analysis, simulation and experimental results of two short circuit current limiters, the Thyristor Inserted Reactor and the Thyristor Bypassed Capacitor. The purpose of the fault current limiters is to reduce the overstress of circuit breakers provoked by the network expansion and the consequent increase in fault currents. The simulation and experimental prototype results demonstrate the effectiveness of these devices to limit fault currents, deferring significantly the replacement of circuit breakers with surpassed fault current interruption capacity.