Voltage Direct Current Transmission Lines Research Articles

Development of a Wireless Sensor Network for Distributed Measurement of Total Electric Field under HVDC Transmission Lines

A wireless sensor network-based distributed measurement system is designed for collecting and monitoring the electric field under the high voltage direct current (HVDC) transmission lines. The proposed system architecture is composed of a group of wireless nodes connected with electric field sensors and a base station. The electric field sensor based on Gauss's law is elaborated and developed. For the design of wireless node, the ARM microprocessor and Zigbee radio frequency module are employed. The proposed system has been used in China's state grid HVDC test base and the in situ power transmission projects. Based on the experimental results, the proposed measurement system demonstrates that it can adapt to the complex electromagnetic environment under the transmission lines and can accomplish the accurate, flexible, and stable demands of the electric field measurement.

A sensitive and high-speed traveling wave protection scheme for HVDC transmission line

Summary This paper presents a novel traveling wave protection scheme to satisfy the sensitive and high-speed performances of protective relaying for line commutated converter high voltage direct current (HVDC) transmission lines. The scheme performs by using a startup and two auxiliary criteria with a small sampling interval to ensure the sensitivity of fault detection: the startup criterion adopts the concept of voltage derivative to distinguish between internal and external faults; the two novel auxiliary criteria adopt concepts of voltage difference and voltage ratio to deal with noise interference, which is brought to the fore by using small sampling interval. Besides high sensitivity, the scheme is able to achieve an excellent high-speed performance because it acts only on the basis of the first waveform following a fault. Simulation studies have been conducted in power systems computer aided design/electromagnetic transients including direct current (PSCAD/EMTDC) to evaluate the scheme, which shows that the scheme permits both high speed and high sensitivity for direct current line fault detection at a satisfactory level. Copyright © 2013 John Wiley & Sons, Ltd.

A Novel Pilot Protection for HVDC Transmission Lines Based on Model Error Function

In order to solve the problems in existing protection for high voltage direct current (HVDC) transmission lines, such as insufficient sensitivity for main protection and slow operation for backup protection, a novel pilot protection for HVDC transmission lines based on model error function is proposed in this paper. In the principle, through analyzing the fault component networks, external fault is equivalent to a capacitance model, while the internal fault is equivalent to a inductance model. Taking capacitance model as a benchmark, the model error function was defined to describe the degree of consistency between actual fault data and the benchmark. When an external fault occurs, fault data agree with the capacitance model and model error equals zero. When an internal fault occurs, fault data do not agree with the capacitance model and model error does not equal zero. According to this, a protection criterion is constructed. Theoretical analysis and simulation show that the new principle, not affected by transition resistance and line distributed capacitance current, can identify internal faults and external faults reliably and rapidly.

The potential of wind energy to largely displace existing Canadian fossil fuel and nuclear electricity generation

The potential of wind-generated electricity to displace existing fossil fuel and nuclear generation in Canada is assessed by combining wind turbine power curves with data from the Canadian Wind Energy Atlas. There are many widely-scattered regions with capacity factors (average power output as a fraction of the rated output) greater than 0.4, and some greater than 0.5, that could supply many times the current electricity production from fossil fuel and nuclear powerplants in Canada. By linking multiple high-wind regions to the major demand centres with high voltage direct current transmission lines, the variation in the aggregate electricity output at time scales of one week or less would be greatly reduced, while variations at longer time scales can be largely offset through anti-phase operation of hydro-electric reservoirs. Assuming onshore and offshore wind farm capital costs of about $2000/kW and $3000/kW, respectively, onshore and offshore transmission line costs of $0.5/kW/km and $0.75/kW/km, respectively, and terminal costs of $250/kW, the cost of electricity (financed at a real interest rate of 3%/yr) is 5–7 cents/kWh, which is less than the likely cost of electricity from new coal powerplants equipped to capture CO2 (at least 9 cents/kWh) or from new nuclear powerplants (10–23 cents/kWh).

CALCULATION OF POWER LINE FIELDS BETWEEN CIRCULAR CONDUCTORS

It is important to calculate the electric field at the surface of high voltage direct current power transmission lines, since it is this field which governs the onset of corona discharge and the power loss arising therefrom. A method is presented here to calculate the electric field based on an implementation of the boundary element method for conductors of strictly circular cross section. Given the circular geometry it is possible to resolve all integrals involved analytically. A Galerkin approach is adopted, giving the solution in the spatial frequency domain. That allows a controlled truncation of the system matrix by choice of which frequency components to keep. It transpires that the low frequency components are the most important ones. Two test cases are used to quantify the accuracy of the solution with respect to truncation and distance from the surface. It is found that the accuracy increases with distance from the surface, but for all distances can be controlled by choosing an appropriate level of truncation.

Realizing truly sustainable development: A proposal to expand Aboriginal ‘price adders’ beyond Ontario electricity generation projects

Recognizing the sustainable development potential of incentivizing domestic renewable energy generation, the Province of Ontario (Canada) presciently implemented the Green Energy Act in 2009. The feed-in tariff provisions of this Act provided guaranteed, premium price contracts for new renewable energy generators utilizing a variety of different technologies. Of particular relevance to this article, the Act also included a $0.015 per kW h price adder for those projects that included Aboriginal economic participation. As a result, this policy framework permitted the inclusion of Canada's historically marginalized indigenous peoples in decentralized, small-scale power generation. Although some Aboriginal groups have been able to take advantage of this novel energy supply policy framework, others have been hamstrung by looming caps on new supply procurement and, especially, a lack of transmission capacity. This article picks up on this latter point, contending that the Province should expand the applicability of their policy innovation and consider the adoption of a comparable ‘price adder’ for new transmission projects, given that an estimated $20 billion in new high voltage direct current transmission lines will need to be built over the next 20 years in Ontario. Much, if not all, of this transmission capacity will need to be built on the traditional territories of Aboriginal groups – many of which have unsettled land claims with the Canadian government – and it is crucial that this minority group is included in future energy-related development initiatives. The article concludes by offering suggestions for Aboriginal adders in other energy developments across Canada (and potentially in other international contexts that involve indigenous peoples), including planned transmission projects across the country, ongoing shale gas developments in British Columbia, and controversial oil sands extraction in northern Alberta. Further research into optimal methods for facilitating indigenous participation in energy developments is urged.

Analysis of shielding failure parameters of high voltage direct current transmission lines

This paper studies the influence of different parameters on the shielding failure of high voltage direct current (HVDC) transmission lines. A numerical analysis model considering the developing process of the downward lightning leader based on electromagnetic field theory is used to estimate the lateral striking distance to the transmission line. The influences of different factors (different parameters of the downward lightning leader, HVDC transmission line, and weather conditions) on the shielding failure of the HVDC transmission line (TL) have been considered in this analysis. The results show that the dimensions of the transmission line strongly affect the analysed results of the HVDC–TL shielding failure. ► We study the influence of different parameters on the shielding failure of HVDC–TL. ► We model the downward lightning leader to estimate the lateral striking distance to the TL. ► The TL dimensions effect seriously on the HVDC–TL shielding failure. ► Weather conditions have effect on the HVDC–TL shielding failure.

Fast Decoupled Power Flow for Power System with High Voltage Direct Current Transmission Line System

Problem statement: High voltage direct current transmission line system has been widely applied for control power flow in power system. The power flow analysis was the one of powerful tools by which the power system equipped was analyzed both for planning and operation strategies. Approach: This study presented the method to analyze power flow of power system consisted of HVDC system. HVDC was modeled as the complex power injections. The presented complex power injected was incorporated into the existing power flow program based on fast decoupled method. The presented method was tested on the multimachine power system. Results: The transmission line loss of the system with and without HVDC was compared. Conclusion: From the simulation results, the HVDC can reduce transmission line loss of power system.

Analysis of the Ionized Field Under HVDC Transmission Lines in the Presence of Wind Based on Upstream Finite Element Method

Corona phenomenon generated from high voltage direct current (HVDC) transmission lines can affect the environment nearby. Based on the upstream finite element method, an iterative algorithm is used to analyze the ionized electric field and the ion current density at the ground level with the wind velocity taken into consideration. The algorithm is efficiently convergent. The proposed method is testified by measurement results of a unipolar line in the presence of wind and a bipolar test line. Finally some examples are analyzed to predict the effect of the wind and to determine the transmission corridor of ±800 kV HVDC transmission line.

Latitudinal gradients in vegetation along a disturbed transmission line right-of-way in Manitoba

A floristic survey was conducted along the high voltage direct current transmission line right-of-way in Manitoba. The right-of-way extends over 895 km, from 50 to 56° N latitude, intersecting six of the natural vegetation zones. The disturbed right-of-way communities differ from the adjacent undisturbed communities in both species composition and physiognomy. The majority of disturbed communities are characterized by high graminoid richness and cover, principally as a result of such secondary disturbances as grazing, mowing, herbicide treatment, and fire. In contrast, the majority of undisturbed communities are woodland or forested areas consisting of species from a variety of growth forms. Species richness in most plant growth forms (graminoid, forb, and tall shrub) decreases significantly with an increase in latitude in both the undisturbed and disturbed communities; the only exception being the low shrub group, which occurs predominantly in the northern latitudes. The composition of the undisturbed communities is highly influenced by changes in latitude and three major vegetation zones are recognizable. This strong latitudinal gradient is absent from the disturbed communities where the majority of species are ubiquitous.

DC power interruption technology.

This report describes the newest technology for large DC pow er interruption of high voltage direct current (HVDC) transmission lines and thermonuclear fusion equipment power supply system. The main switching elements of DC interrupters are constructed by the most judicious use of VCB, ABB, or thyristor switch based on the individual devices. In particular, utilization of semiconductor switches is becoming more common in fusion equipment power supply system. The circuit interrupters based on this DC power interruption technology should be useful in future thermonuclear fusion equipment.

Field Determinations of HVDC Ozone Production Rates

The environment near a high voltage direct current (HVdc) transmission line experiences corona effects, including the production of oxidants. Field determination of ozone production rates were made at the Bonneville Power Administration (BPA) HVdc Test Facility, The Dalles, Oregon, in fall and winter 1977. A novel micrometeorological profiling technique was used to identify sources of ozone plumes. The results indicate that even during precipitation the atmospheric ozone concentrations from HVdc lines at voltages up to ±550 kV are relatively small. Measured atmospheric ozone concentration plumes are consistent with laboratory data predictions of ozone concentrations based on corona, line parameters, and ambient dispersion. This confirmation under worst-case field conditions demonstrates the validity of previous estimates of a very low magnitude of the potential ozone effects.

In-Situ Monitoring of Leakage Current on Composite and Glass Insulators of the Cahora Bassa HVDC Transmission Line

High voltage transmission line design requires careful insulator selection to ensure good operational performance. This paper reports on the in-situ measurements of leakage current (LC) on composite and glass insulators of the Cahora Bassa high voltage direct current (HVDC) transmission line in South Africa over a 6 - month period. The influence of temperature, humidity, dew, rain and the HVDC line's voltage and current on LC are investigated. The results show that the composite and glass insulator LC behaviour is similar, except in cases of high humidity or rain. At the commencement of rainfall and humidity (>90%), elevated LC levels are observed on glass insulators, while composite insulators demonstrate lower LC levels under these conditions. Under nominal weather conditions of no rain and low humidity, the LC measurements exhibit an almost square-wave behaviour with LC switching between lower (≈20 μA) and higher values (≈60 μA) with relatively short transitions on a daily basis. This phenomenon can be ascribed to condensation on the insulators, which is a primary determinant of the LC levels on contaminated insulators. The line current and voltage fluctuations do not influence the LC level.