Reliability Engineering Methods for Distribution Systems - Influence of Differences between Cable Systems and Overhead Lines

One way to increase distribution network reliability is to replace traditional overhead lines with underground cables. To fully utilize these investments, network owners will have to adjust their reliability engineering methods to suit the new cable networks. In this paper different condition assessment methods as well as improved failure statistics for cable systems are considered. The paper is based on information from project reports and scientific papers. In addition a number of Swedish distribution network owners have been asked to share their opinion of reliability engineering work of today and the future. The methods used for distribution system condition assessment change as overhead lines are replaced by underground cable. Visual inspections can no longer be used and diagnostic methods are instead introduced. The diagnostic methods are costly to perform. To become frequently used they must prove to be efficient enough to justify the financial means required. New, improved, diagnostic methods are under development and since most cable failures are related to component properties the use of diagnostic methods is likely to increase. Statistics show that a majority of the cable system failures are ageing failures. The ageing failures do not to any large extent depend on environmental factors but on component properties. This implies that component lifetime standard deviation decreases as component data are related to the statistics, yet failure statistics is at present not related to component data. A majority of the network owners contributing to this paper agree that the nature of cable failures, except excavation failures, makes it interesting and useful to related cable data to failure statistics and to share the statistics with other network owners. Several Swedish distribution network owners are in the process of installing new program for network analysis. One challenge is to decide which component data that shall be related to the failure statistics. Operational age, maintenance history, manufacturer and year of manufacturer are four manageable factors which influence on failure statistics is already established but yet not thoroughly evaluated. In addition the method of cable excavation is suggested as a fifth interesting factor related to cable system reliability

Spirometrian suorittaminen ja tulkinta : uudet suomalaiset ja monikansalliset viitearvot käyttöön - Suomen Kliinisen Fysiologian yhdistyksen ja Suomen Keuhkolääkäriyhdistyksen suositus 2015

•Hil­jattain on jul­kaistu uu­det suoma­laiset ai­kuisten spi­ro­metrian vii­tearvot, joi­den mit­taukset kat­tavat myös vanhus­väestön 84 vuo­den ikään as­ti. •Uu­sien ar­vojen tulkin­nassa otetaan käyt­töön mi­tatun ar­von poik­keaman mää­rä viitear­vo­po­pu­laation ­kes­kiar­vosta z-yksik­köinä (sama kuin SD). Muu­toksen vaikeu­saste ar­vioidaan z-ar­von mu­kaan. •Nor­maalin va­riaation ala­raja on klii­ni­sissä tutki­muk­sissa kai­kille spi­ro­met­ria­muut­tu­jille sa­ma (z-ar­vona –1,65). Ter­veistä 95 % asettuu tä­män ra­jan ylä­puo­lelle. •Syn­ty­pe­rältään ulko­maa­laisten las­ten ja ai­kuisten tutki­muk­sissa suosi­tellaan käytet­tä­väksi uu­sia kansain­vä­lisiä GLI2012-vii­tear­voja. •Suo­ma­laisten las­ten tutki­muk­sissa suosi­tellaan käytet­tä­väksi edelleen van­hoja suoma­laisia viitear­voja, mut­ta nii­den klii­ni­sessä sovel­ta­mi­sessa suosi­tellaan nyt z-ar­vojen käyt­töä. •Ai­kuisten van­hat suoma­laiset vii­tearvot ei­vät ole perus­tuneet todel­lisiin mittaus­tu­loksiin yli 64-vuo­tiailla. Van­hojen ar­vojen käyt­tö on aiheut­tanut toden­nä­köi­sesti hengi­tys­tieobst­ruktion yli­diag­nos­tiikkaa vanhem­missa ikä­ryh­missä.Peer reviewe

Analysis of an induction regulator for power flow control in electric power transmission systems

Controlling the power flow in transmission systems has recently gained increased interest. The difficulties of building new lines and the pressure of having a high utilization of existing assets, makes the flexibility of grid systems increasingly important. This master thesis work investigates induction regulators as control devices for active power flow in a transmission system. A small change in angle of the rotor affects both the amplitude and the phase of the voltage. The magnetic coupling in the induction regulator can be controlled by changing the permeability of a thermo magnetic material such as gadolinium and can hence give a second independent controlling parameter. An analytical model and calculations in the FEM software AceTripleC together with Matlab, is used to simulate the influence of the regulators connected to a simple grid in case1, a 400 kV scenario and case 2, a 45 kV scenario. The analysis was carried out on a small transmission system consisting of two parallel transmission lines connected to source and load. The induction regulators are connected to one of the parallel transmission lines. The regulators modelled in case 1 must be able to control the active power flow in the regulated line to vary between 50 and 150 % of the original power flow through this line. This shall be done over a range of 0 to 800 MW transmitted power. The regulators modelled in case 2 must be able to control the active power flow in the regulated line to vary between 0 and 30 MW, if this does not cause the power flow in the parallel line to exceed 30 MW. This shall be done over a range of 0 to 50 MW transmitted power. The regulators are designed as small and inexpensive as possible while still fulfilling requirements regarding the active power flow controllability in the grid, current density in windings and maximum flux density in core and gap. The results indicate that the size of the 400 kV solution has to be reduced to become competitive whereas for the 45 kV solution the relative difference to existing solution is smaller. Advantages with the proposed design over a phase shifting transformer are mainly a simpler winding scheme and the absence of a tap changer

A comparison of helium dilution and plethysmography in measuring static lung volumes

In order to examine the usefulness of the multi breath helium dilution method (MB) it was compared to the single breath helium dilution method (SB) and body plethysmography (BP). Residual volume (RV), total lung capacity (TLC) and vital capacity (VC) were measured in seventeen subjects with obstructive (11) or restrictive (6) lung disease and four normal subjects. With information from professional literature and current periodicals, advantages and disadvantages with all three methods were compared. ANOVA and Student's t-test were performed on the measurement results. The results of the statistical tests tell us there are differences among the methods in the group of obstructive patients. They also reveal a notable difference between the MB and SB methods when measuring the same parameter. In addition, it was noted that none of the existing sets of prediction equations fulfill the requirements established on high quality lung function testing. Although a thorough evaluation of the reproducibility of the method is still required, it appears to be a viable alternative to body plethysmography. We claim that measuring the above mentioned static lung volumes with only the single breath helium dilution method cannot be considered a satisfactory practice

Influence of distributed compensation on earth fault protection in cable distribution systems

The growing use of underground cables in distribution systems increases the capacitive coupling of the network to earth and as a consequence the capacitive earth fault current. In rural systems consisting of long cable feeders the extensive reactive current transportation gives rise to resistive losses that influence the earth fault protection. Simulations carried out in this work suggest the resistive losses disable sensitive earth fault protection in centrally compensated resonant earthed neutral systems unless unconventional low earth fault protection thresholds are applied. The introduction of distributed compensation will decrease the reactive current transportation and associated resistive losses. Distributed compensation will enable the use of sensitive earth fault protection using conventional protection thresholds

Young women´s experiences of living with breast cancer : - A narrative study

Bakgrund: Antalet kvinnor som diagnostiseras med bröstcancer uppgår till cirka 9000 per år. Av dessa är endast 4 % under 40 år. Flertalet tidigare studier fokuserar på kvinnor äldre än 40 år. Livet förändras på flera plan för kvinnorna i och med en bröstcancerdiagnos. Behovet av stöd upplevs som stort. Syfte: Studiens syfte är att beskriva unga kvinnors upplevelser av att leva med bröstcancer. Metod: Studien har utförts med en kvalitativ ansats med ett patientperspektiv. Analys av narrativer, i form av bloggar, har använts som analysmetod. Data består av sju bloggar publicerade på internet. Resultat: De huvudteman som framkom var; Ett liv i förändring, en kropp i förändring samt möten med sjukvården. Vidare har dessa uppdelats i underteman. Slutsats: Upplevelsen av att leva med bröstcancer är högst individuell. Dock kan vissa huvudområden urskiljas som är gemensamma för kvinnorna. Studien ger en inblick i vad unga kvinnor med bröstcancer upplever i det vardagliga livet. Genom fördjupad förståelse för individens upplevelse kan sjukvården utarbeta strategier för att möta och stödja de individuella behov som patienten ger uttryck för.Background: 9000 women is diagnosed with breast cancer every year. Only 4 % are 40 years and younger. Previous research is focused on women older than 40 years. Lifechanges can be seen in many levels when women is diagnosed with breast cancer. The need for support is experienced as great. Purpose: The aim of this study is to describe young women’s experiences of living with breast cancer. Method: This study has a qualitative approach and a patient’s perspective. Analysis of narratives, in form of blogs, is used as analytic method. Data consists of seven blogs published online. Result: The main themes that emerged was; A life in change, a body in change and meetings with the health care. Further, these were divided into sub-topics. Conclusion: The experience of living with breast cancer is highly individual. However, some main areas can be identified as common to the women. The study provides insight into what young women with breast cancer experience in everyday life. Through in-depht understandning of the individual’s experience, healthcare can develop strategies to meet and support the individual needs expressed by the patient

Central or Local Compensation of Earth-Fault Currents in Non-Effectively Earthed Distribution Systems

Centralized Petersen coil earthing in networks with extensive use of underground cable involves flow of large quantities of reactive earth fault current. In networks with long radial cable feeders this creates problems involving active losses and active and reactive earth fault current. One possible solution to the problem is the use of local compensation. This paper aims at understanding the limitations of traditionally compensated networks and compares these to networks that are locally compensated. This is done through analytical calculations and PSCAD simulations that are combined with results from a project studying cables in Swedish distribution networks. In addition, basic PSCAD simulations are used to clarify how the rating and placing of the distributed compensation units affects active earth fault current and investment cost