Hvilken betydning har resistivitet for prosjektering av jordelektroder?
Tore Solhaug har mange års erfaring og regnes av mange som en guru innen jordplatemåling. Han vil snakke om betydningen av å kjenne til jordens elektriske ledeevne (resistivitet) for å kunne prosjektere jordelektroder. Resistiviteten i bakken er en viktig faktor for å beregne omfang, beste plassering og forventet overgangsmotstand for jordelektroder. Den har også stor betydning for kvaliteten på impulsjording. I tillegg benyttes resistivitetsverdien til å beregne om et høyspenningsanlegg (for eksempel distribusjonsnett) kan betegnes som Omfattende jordingsnettverk (global jord).
Han snakket om spesifikk jordmotstand, hva er viktig med den? Bør det måles resistivitet – eller kan det benyttes tabeller for å prosjektere jordingssystemer. Resistivitet vs Global jord. Målinger kan benyttes til å beregne størrelse / omfang på jordelektrode, finne beste plassering for jordelektrode og beregne om området kan defineres som omfattende jordingsnettverk (global jord).
This is a ppt on World Energy Conservation Day....... It gives us a brief information about energy conservation....... It tells you about the importance of energy conservation...... And how can we save energy in our day-to-day lives.......
Ett projektarbete från Business & Design programmet vid Handelshögskolan & HDK. Det berör ämnet hållbar utveckling och organisationer kan använda sig av ramverket som hållbar utveckling medför. Vi får följa Nikes resa från att vara ett utsatt företag till ett som står främst i ledet i dagens kamp om vår framtid.
Hi , I am Ruby. I would like to share a ppt on ऊर्जा संरक्षण /Energy Conservation. "Let's NURTURE THE NATURE, SO THAT WE CAN HAVE A BETTER FUTURE". Hope these slide will help you to know better about EnergyConservation.
Sandia National Laboratories is developing virtual power plant (VPP) technology to help integrate renewable energy into the electric grid. A VPP aggregates distributed energy resources like solar, storage, and demand response to provide grid services normally provided by traditional power plants. Sandia is researching the optimization, control, and cybersecurity of VPPs. In 2017, they will demonstrate a VPP using real hardware at their Distributed Energy Technologies Laboratory. The goal is to increase renewable energy adoption while improving grid reliability and resilience.
The document discusses energy conservation and climate change. It defines energy conservation as any behavior that results in less energy usage, such as turning off lights. It states that climate change poses a serious threat and that global temperatures are rising at an unprecedented rate due to human activity like carbon dioxide emissions. The document advocates for addressing this issue through improving energy efficiency in technology and changing energy-consuming behaviors to use less energy and reduce waste.
The agricultural sector in the country is distressed, water scarcity being a major reason. The agrarian
distress is also intertwined with the woes in the power distribution sector. Of major importance to
development, solving these deeply connected issues will require a holistic approach. The recently
announced KUSUM scheme by the Ministry of New and Renewable Energy (MNRE) attempts to address
some of these issues.
KUSUM is presented as a scheme that primarily aims at benefiting farmers.
Han snakket om spesifikk jordmotstand, hva er viktig med den? Bør det måles resistivitet – eller kan det benyttes tabeller for å prosjektere jordingssystemer. Resistivitet vs Global jord. Målinger kan benyttes til å beregne størrelse / omfang på jordelektrode, finne beste plassering for jordelektrode og beregne om området kan defineres som omfattende jordingsnettverk (global jord).
This is a ppt on World Energy Conservation Day....... It gives us a brief information about energy conservation....... It tells you about the importance of energy conservation...... And how can we save energy in our day-to-day lives.......
Ett projektarbete från Business & Design programmet vid Handelshögskolan & HDK. Det berör ämnet hållbar utveckling och organisationer kan använda sig av ramverket som hållbar utveckling medför. Vi får följa Nikes resa från att vara ett utsatt företag till ett som står främst i ledet i dagens kamp om vår framtid.
Hi , I am Ruby. I would like to share a ppt on ऊर्जा संरक्षण /Energy Conservation. "Let's NURTURE THE NATURE, SO THAT WE CAN HAVE A BETTER FUTURE". Hope these slide will help you to know better about EnergyConservation.
Sandia National Laboratories is developing virtual power plant (VPP) technology to help integrate renewable energy into the electric grid. A VPP aggregates distributed energy resources like solar, storage, and demand response to provide grid services normally provided by traditional power plants. Sandia is researching the optimization, control, and cybersecurity of VPPs. In 2017, they will demonstrate a VPP using real hardware at their Distributed Energy Technologies Laboratory. The goal is to increase renewable energy adoption while improving grid reliability and resilience.
The document discusses energy conservation and climate change. It defines energy conservation as any behavior that results in less energy usage, such as turning off lights. It states that climate change poses a serious threat and that global temperatures are rising at an unprecedented rate due to human activity like carbon dioxide emissions. The document advocates for addressing this issue through improving energy efficiency in technology and changing energy-consuming behaviors to use less energy and reduce waste.
The agricultural sector in the country is distressed, water scarcity being a major reason. The agrarian
distress is also intertwined with the woes in the power distribution sector. Of major importance to
development, solving these deeply connected issues will require a holistic approach. The recently
announced KUSUM scheme by the Ministry of New and Renewable Energy (MNRE) attempts to address
some of these issues.
KUSUM is presented as a scheme that primarily aims at benefiting farmers.
This document provides an overview of soil and water conservation engineering. It discusses the status of soil conservation in India, including causes and extent of soil degradation. It outlines 10 topics that will be covered, including the universal soil loss equation, erosion control techniques, water harvesting, and wind erosion. The importance of soil conservation to protect productive lands and prevent damage from droughts and floods is emphasized. Key programs implemented in India to address soil erosion and degradation are also summarized.
Bio intensive gardens by Dr.Julian Gonsalves_18June2018Shiela Santos
Bio-intensive gardens provide nutrition, adapt to climate change, and support biodiversity. They involve narrow, raised beds that are dug 12 inches deep, improving soil structure and water retention. Gardens feature diverse, indigenous crops and cover crops that build soil health. Studies found bio-intensive gardens increased soil nutrients like nitrogen and phosphorus while supporting above and below ground biodiversity. Schools saw high vegetable production from their gardens, which provided both nutritional and financial benefits.
This document discusses solar food processing, which uses solar energy for post-harvest food processing to provide quality food at low or no additional fuel costs. It explains that most foods need processing like pasteurization or dehydration before consumption. Dehydration, an important preservation method, is very energy intensive. Solar food processing brings together solar energy generation and food production to address increasing global population and energy demands. Various solar collector designs and dryer types - including open air, direct, indirect, hybrid, and mixed dryers - are described for dehydrating foods using solar heat.
Solar drying is one of the application of solar energy. Drying means moisture removal from the product. Drying is helpful in preserving food product for long time; it prevent product from contamination. Direct solar drying, indirect solar drying, and mixed mode solar drying these are different solar drying methods. Primarily open to the sun or direct sun drying technique is used. However, it has some disadvantages. These disadvantages can be eliminated by indirect type of dryer which is used for drying products as application of solar energy. In this paper, we studied the different technique of drying and various modes of solar drying
Energy conservation is important to reduce costs, promote economic security, and protect the environment for future generations as fossil fuels are non-renewable. While industrialized countries rely heavily on fossil fuels, transitioning to renewable sources like solar, wind, hydroelectric, geothermal, and biomass is key. Individuals can conserve energy through everyday actions like using appliances efficiently, insulating homes, and choosing active transportation when possible. As fossil fuel reserves are depleted, a combined effort of alternative energy development and behavioral changes around energy use is needed.
The document discusses various principles of greenhouse heating, including important heat units like Btu and boiler horsepower. It describes how heat is lost through conduction, infiltration and radiation. Different heating systems are outlined like unit heaters, central heat and radiant heat. Unit heaters are best for smaller greenhouses while central heating is more economical for larger operations. Factors that influence heat loss and common fuels are also summarized.
This document discusses integrated farming systems (IFS), which combine various agricultural enterprises like cropping, animal husbandry, fisheries, and forestry together. IFS aim to maximize production and income while efficiently utilizing resources through recycling waste from one component as inputs for others. Some benefits of IFS include increased profits and sustainability through waste recycling, stable income from multiple enterprises, and better utilization of labor and resources. Common IFS components include crop cultivation combined with livestock, poultry, aquaculture, horticulture, apiculture, or agroforestry systems.
The document analyzes the physical and chemical properties of Silam (Perilla fructescens) seeds and oil found in Nepal. Key findings include:
1. The physical properties of Silam seeds were analyzed, such as 1000 kernel weight (4.13g), angle of repose (52.46°), and bulk density (424.48 g/cm3).
2. Chemical analysis found Silam seed contains 17.3-17.43% protein, 48.19-48.516% fat, and 0.857-0.915% ash.
3. Analysis of Silam oil showed a moisture content between 0.196-0.913%, refractive index of 1
Biomass is an alternative power source that can be generated from organic waste materials like food scraps, garden waste, wood, and manure. The document discusses how biomass power works, providing examples of its use in landfills in Auckland and Wellington, New Zealand to generate electricity. It suggests schools could also use biomass power by collecting organic waste to fuel an on-site biogas plant and burn wood pellets to heat boilers, providing a cheap, sustainable energy option.
This course explains the best solution for direct and immediate reduction of energy consumption. ... It includes planning and operation of energy-related production and consumption units especially in context of agriculture. The course also detailed the main objectives of energy management.
This document discusses energy conservation in India. It notes that energy conservation is important due to scarcity of electricity across the country. It discusses various ways to conserve energy, including improving energy efficiency, reducing transmission and distribution losses, and decreasing commercial losses through measures like preventing power theft. The document provides statistics on India's historical and current energy generation, consumption, losses, and targets for reduction of aggregate technical and commercial losses. Overall it emphasizes the importance of energy conservation for India's future energy security and development.
Non conventional energy resources seminar reportAyush Chandra
this is a seminar report which clearly describes about the latest emerging technologies which can be used to harness non conventional energy and to effectively use them. Also it briefly discusses about the industry and market policy trends which r taking place for non conventional energy resources
The document discusses the RiceCheck system for increasing productivity and efficiency in rice production. It notes that there is still a large yield gap in irrigated rice systems globally. RiceCheck was developed as an integrated crop management approach based on the Australian system. FAO is working with countries to modify and disseminate RiceCheck to help close yield gaps and increase productivity in a sustainable manner. Initial results show it has increased yields by up to 30% in countries like Brazil, Indonesia, and Vietnam.
Solar food drying Presentation for Thai delegationGordon Hirst
Sunlabob is a Laos-based social enterprise that provides renewable energy and clean water solutions. It launched in 2001 as the first commercial renewable energy company in Laos, with a mission to deliver clean energy and water to rural, off-grid communities in a sustainable, socially-minded way. Solar food drying is one solution offered, as it provides clean, hygienic drying using solar thermal or solar air systems while reducing costs, smoke, and greenhouse gas emissions compared to traditional drying methods. The document outlines the principles, design considerations, and examples of solar food drying systems.
An enterprise budget estimates potential revenue, expenses, and profit for a single crop or livestock enterprise. It includes revenue, variable costs, fixed costs, and estimated profit. Variable costs are incurred only if the crop is produced, while fixed costs must be paid regardless. The document provides an example watermelon budget and explains how to construct a crop budget. It also describes how to use enterprise budget data to calculate cost of production and break-even yield and price.
Sustainable agriculture is the practice of farming using principles of ecology ,the study of relationship between organisms and their environment.
this form of agriculture enables us to produce healthful food without compromising future generations ability to do the same.
What is Climate-Smart Agriculture? Background, opportunities and challengesCIFOR-ICRAF
This presentation by Alexandre Meybeck of the FAO was given at a session titled "Using climate-smart technologies to scale up climate-smart agriculture practices" at the Global Landscapes Forum in Lima, Peru, on December 7, 2014.
The panel presentation and discussion focused on how these climate-smart technologies can be scaled-up to benefit smallholder farmers. This was followed by a public debate.
This document provides an overview of soil and water conservation engineering. It discusses the status of soil conservation in India, including causes and extent of soil degradation. It outlines 10 topics that will be covered, including the universal soil loss equation, erosion control techniques, water harvesting, and wind erosion. The importance of soil conservation to protect productive lands and prevent damage from droughts and floods is emphasized. Key programs implemented in India to address soil erosion and degradation are also summarized.
Bio intensive gardens by Dr.Julian Gonsalves_18June2018Shiela Santos
Bio-intensive gardens provide nutrition, adapt to climate change, and support biodiversity. They involve narrow, raised beds that are dug 12 inches deep, improving soil structure and water retention. Gardens feature diverse, indigenous crops and cover crops that build soil health. Studies found bio-intensive gardens increased soil nutrients like nitrogen and phosphorus while supporting above and below ground biodiversity. Schools saw high vegetable production from their gardens, which provided both nutritional and financial benefits.
This document discusses solar food processing, which uses solar energy for post-harvest food processing to provide quality food at low or no additional fuel costs. It explains that most foods need processing like pasteurization or dehydration before consumption. Dehydration, an important preservation method, is very energy intensive. Solar food processing brings together solar energy generation and food production to address increasing global population and energy demands. Various solar collector designs and dryer types - including open air, direct, indirect, hybrid, and mixed dryers - are described for dehydrating foods using solar heat.
Solar drying is one of the application of solar energy. Drying means moisture removal from the product. Drying is helpful in preserving food product for long time; it prevent product from contamination. Direct solar drying, indirect solar drying, and mixed mode solar drying these are different solar drying methods. Primarily open to the sun or direct sun drying technique is used. However, it has some disadvantages. These disadvantages can be eliminated by indirect type of dryer which is used for drying products as application of solar energy. In this paper, we studied the different technique of drying and various modes of solar drying
Energy conservation is important to reduce costs, promote economic security, and protect the environment for future generations as fossil fuels are non-renewable. While industrialized countries rely heavily on fossil fuels, transitioning to renewable sources like solar, wind, hydroelectric, geothermal, and biomass is key. Individuals can conserve energy through everyday actions like using appliances efficiently, insulating homes, and choosing active transportation when possible. As fossil fuel reserves are depleted, a combined effort of alternative energy development and behavioral changes around energy use is needed.
The document discusses various principles of greenhouse heating, including important heat units like Btu and boiler horsepower. It describes how heat is lost through conduction, infiltration and radiation. Different heating systems are outlined like unit heaters, central heat and radiant heat. Unit heaters are best for smaller greenhouses while central heating is more economical for larger operations. Factors that influence heat loss and common fuels are also summarized.
This document discusses integrated farming systems (IFS), which combine various agricultural enterprises like cropping, animal husbandry, fisheries, and forestry together. IFS aim to maximize production and income while efficiently utilizing resources through recycling waste from one component as inputs for others. Some benefits of IFS include increased profits and sustainability through waste recycling, stable income from multiple enterprises, and better utilization of labor and resources. Common IFS components include crop cultivation combined with livestock, poultry, aquaculture, horticulture, apiculture, or agroforestry systems.
The document analyzes the physical and chemical properties of Silam (Perilla fructescens) seeds and oil found in Nepal. Key findings include:
1. The physical properties of Silam seeds were analyzed, such as 1000 kernel weight (4.13g), angle of repose (52.46°), and bulk density (424.48 g/cm3).
2. Chemical analysis found Silam seed contains 17.3-17.43% protein, 48.19-48.516% fat, and 0.857-0.915% ash.
3. Analysis of Silam oil showed a moisture content between 0.196-0.913%, refractive index of 1
Biomass is an alternative power source that can be generated from organic waste materials like food scraps, garden waste, wood, and manure. The document discusses how biomass power works, providing examples of its use in landfills in Auckland and Wellington, New Zealand to generate electricity. It suggests schools could also use biomass power by collecting organic waste to fuel an on-site biogas plant and burn wood pellets to heat boilers, providing a cheap, sustainable energy option.
This course explains the best solution for direct and immediate reduction of energy consumption. ... It includes planning and operation of energy-related production and consumption units especially in context of agriculture. The course also detailed the main objectives of energy management.
This document discusses energy conservation in India. It notes that energy conservation is important due to scarcity of electricity across the country. It discusses various ways to conserve energy, including improving energy efficiency, reducing transmission and distribution losses, and decreasing commercial losses through measures like preventing power theft. The document provides statistics on India's historical and current energy generation, consumption, losses, and targets for reduction of aggregate technical and commercial losses. Overall it emphasizes the importance of energy conservation for India's future energy security and development.
Non conventional energy resources seminar reportAyush Chandra
this is a seminar report which clearly describes about the latest emerging technologies which can be used to harness non conventional energy and to effectively use them. Also it briefly discusses about the industry and market policy trends which r taking place for non conventional energy resources
The document discusses the RiceCheck system for increasing productivity and efficiency in rice production. It notes that there is still a large yield gap in irrigated rice systems globally. RiceCheck was developed as an integrated crop management approach based on the Australian system. FAO is working with countries to modify and disseminate RiceCheck to help close yield gaps and increase productivity in a sustainable manner. Initial results show it has increased yields by up to 30% in countries like Brazil, Indonesia, and Vietnam.
Solar food drying Presentation for Thai delegationGordon Hirst
Sunlabob is a Laos-based social enterprise that provides renewable energy and clean water solutions. It launched in 2001 as the first commercial renewable energy company in Laos, with a mission to deliver clean energy and water to rural, off-grid communities in a sustainable, socially-minded way. Solar food drying is one solution offered, as it provides clean, hygienic drying using solar thermal or solar air systems while reducing costs, smoke, and greenhouse gas emissions compared to traditional drying methods. The document outlines the principles, design considerations, and examples of solar food drying systems.
An enterprise budget estimates potential revenue, expenses, and profit for a single crop or livestock enterprise. It includes revenue, variable costs, fixed costs, and estimated profit. Variable costs are incurred only if the crop is produced, while fixed costs must be paid regardless. The document provides an example watermelon budget and explains how to construct a crop budget. It also describes how to use enterprise budget data to calculate cost of production and break-even yield and price.
Sustainable agriculture is the practice of farming using principles of ecology ,the study of relationship between organisms and their environment.
this form of agriculture enables us to produce healthful food without compromising future generations ability to do the same.
What is Climate-Smart Agriculture? Background, opportunities and challengesCIFOR-ICRAF
This presentation by Alexandre Meybeck of the FAO was given at a session titled "Using climate-smart technologies to scale up climate-smart agriculture practices" at the Global Landscapes Forum in Lima, Peru, on December 7, 2014.
The panel presentation and discussion focused on how these climate-smart technologies can be scaled-up to benefit smallholder farmers. This was followed by a public debate.
Elkomp 2024 - Spenningsprøving og tilstandskontroll av høyspentkabler med VLF...Trainor Elsikkerhet AS
• Spenningsprøving av kabler med VLF
• Relevante standarder for VLF
• Tilstandskontroll med VLF
✦ VLF TD test for TanDelta
✦ VLF PD test for glimming (partial discharge)
• VLF systemer fra B2 ELECTRONIC
- 41 utdannede piloter og 5 under opplæring
- Rundt 1000 flytimer og 5100 flighter siden
våren 2019
- 408 flytimer og 1740 flighter i 2023
- Ingen alvorlige hendelser
- 2 mindre alvorlige hendelser
Elkomp 2024 - Elbillading med energilagring for å balansere strømnettet Nils ...Trainor Elsikkerhet AS
The roadblock to a greener future
Lack of electrical power…
> Where you need it
> When you need it
> The amount you need
…is slowing down the
electrification of transportation
Elkomp 2024 - Luftledninger over 1 kV – NEK 445 Lars Jakob Paulsen, Fagsjef h...Trainor Elsikkerhet AS
• NEK standard
• Hvem er NK 11 og hva jobber de med
• Hva skjer i internasjonal standardisering
• NEK 445 og pågående arbeid med
Nasjonale Normative forhold (NNA)
Elkomp 2024 - Forskrift om elektriskeforsyningsanlegg - Frode Kyllingstad DSBTrainor Elsikkerhet AS
Forskrift om
elektriskeforsyningsanlegg
Elsikkerhetskompetanse
Trainor, Tønsberg
Mars 2023
Frode Kyllingstad 14. mars 2024
Sjefingeniør
Elsikkerhetsseksjonen
Viktige endringer i EN 50110-1: 2023
• Hva medfører dette i praksis for bransjen
• Sammenhengen mellom FSE og EN 50110-1
• Viktige definisjoner
• Arbeidsmetodikk
• 2-polet spenningstesting
• Krav til personell
4. Trainor team kontroll og måling
Utfører måletjenester på jordingssystemer for elkraft og industri
- Overgangsmotstand
- Kontinuitet i jordforbindelser
- Dokumentasjon av berøringsspenninger
- Beregning av omfattende jordingsnettverk (global jord) i distribusjonsnett
Gjennomfører årlige praktisk rettede kurs i måleteknikk på jordelektroder
5. Spesifikk jordmotstand, også kalt
jordresistivitet
• En betegnelse på elektrisk ledeevne i jord
• Benevnelse i Ohm meter eller Ohm cm
6. Jordresistivitet
Hva er viktig med den?
• Jordelektrodens egenskaper påvirkes av grunnforholdene
• Det kan benyttes tabeller for å prosjektere jordingssystemer
– eller –
• Resistivitet kan måles for å oppnå konkrete verdier som
gjenspeiler lokale forhold
• Resistivitet vs Global jord
7. Jordresistivitet
• Hvordan kan vi vite at vi vite at vi velger riktig jordart?
• Tabellverdier er svært omtrentlige
– Resistiviteten varierer med fuktighetsgrad i bakken
Type jordsmonn Resistivitetsverdier
Finkornet sand 150-2000 ohm cm
Jord (matjord, myr, torv) 5-500 ohm cm
Leire 5-200 ohm cm
Kritt (kalkholdig jord) 50-3000 ohm cm
Skifer 200-50000 ohm cm
Granitt >1 000 000 ohm cm
8. Jordresistivitet
Målinger kan benyttes til å
• beregne størrelse/omfang på jordelektrode
• beregne motstandsverdi for elektrode
• finne beste plassering for jordelektrode
• beregne om området kan defineres som omfattende jordingsnettverk
(global jord)
9. Jordresistivitet
Fra FEF:2006, § 4-11 heter det:
• Tillatt berøringsspenning UTP i figur 4-2 ansees være overholdt dersom en av
følgende forutsetninger er oppfylt:
– Jordingsanlegget er en del av et utbredt jordingssystem
– Jordpotensialhevningen UE ved jordfeil skal ikke overstige 2 ganger tillatt
berøringsspenning
– Jordpotensialhevningen UE ved jordfeil skal ikke overstige 4 ganger tillatt
berøringsspenning, samtidig som det er gjennomført tiltak beskrevet under
avsnittet «Tiltak for å redusere berøringsspenning» skal være iverksatt
Dersom disse forutsetningene ikke er oppfylt, skal den reelle
berøringsspenningen beregnes eller måles.
8
16. Jordresistivitet
R = motstand målt i ohm
a = avstanden mellom spydene målt i cm eller meter
ρ = resistiviteten til en dybde lik «a» referert i cm eller meter
𝜌 = 2𝜋𝑎𝑅
a
aaa
a
a
20
C1
P1
P2
C2
17. Etablering av sammensatte elektroder
• Ved flere jordspyd
• 𝑎 = 1,5𝑑
a
d
𝑅 =
𝜌
2 𝑥 𝜋 𝑥 𝐿
x (ln
4 𝑥 𝐿
𝑟
-1) x 1,25 x ant.spyd
19. Jordresistivitet
• Viktig å huske på:
• Dersom elektroden ikke ligger frostfritt vil overgangsmotstand
for den etablerte elektrode variere med årstidene
• Høyest resistivitet og overgangsmotstand i frostmark
21. Jordresistivitet
Hva kan målingene benyttes til ?
Beregning av reell berøringsspenning UT
Fra FEF:2006, § 4-11 heter det:
• Tillatt berøringsspenning UTP i figur 4-2 ansees være overholdt dersom en av følgende
forutsetninger er oppfylt:
– Jordingsanlegget er en del av et utbredt jordingssystem
– Jordpotensialhevningen UE ved jordfeil skal ikke overstige 2 ganger tillatt
berøringsspenning
– Jordpotensialhevningen UE ved jordfeil skal ikke overstige 4 ganger tillatt
berøringsspenning, samtidig som det er gjennomført tiltak beskrevet under avsnittet
«Tiltak for å redusere berøringsspenning» skal være iverksatt
Dersom disse forutsetningene ikke er oppfylt, skal den reelle berøringsspenningen
beregnes eller måles.
23. Beregning av antatt tillatt berøringsspenning
𝑈 𝑇𝑃(𝑡𝑓)=UT (tf)+(RF1+RF2)xIB
RF2 = 1,5m-1 x ρ
24. Oppsummering
• Resistivitetsmålinger er mer presise enn tabeller
• Kan benyttes til viktige beregninger
- i forbindelse med etablering av elektroder
- for å etablere tilleggsjord
- beregne Global jord
- beregne berøringsspenninger
Benevnelsen er Ohm multiplisert med lengde (cm eller meter)
Ved utregning/kalkulasjoner er det viktig å flytte komma korrekt
Det finnes mange tabeller for resistivitet, der de fleste er svært upresise.
Anbefaler å måle for å få eksakt verdi som kan benyttes i beregninger av elektroder.
Pkt 2: I fall bruk av tabeller – hvilken verdi i tabellen skal vi benytte?
Hvis vi bestemmer oss for å måle, kan disse benyttes til…
Benevnelsen er Ohm multiplisert med lengde (cm eller meter)
Ved utregning/kalkulasjoner er det viktig å flytte komma korrekt
- Dersom det kan dokumenteres at jordelektroden er en del av et utbredt jordingssystem, er det ikke krav til å måle overgangsmotstand. For å vurdere om området kan betraktes som «Global jord» trengs det å kjenne til områdets gjennomsnittlige resistivitetsverdi.
Typisk for Global jord kan være en hyttegrend, med omfattende jordingsnettverk
Gjennomsnittlig jordresistivitet betyr at det må foretas representativt antall resistivitetsmålinger for den dybden i bakken som jordledere og elektroder er etablert
Det benyttes en gjennomsnittlig verdi for beregninger.
- Ved å beregne den gjennomsnittlige motstanden for arealet, kan vi finne Jordpotensialhevingen UE, når vi kjenner til 1-polet jordslutningsstrøm
Måling kan gi store gevinster både teknisk og økonomisk.
Undersøkelser i område med etablert elektrode der det er behov for tilleggsjord
Viktige elementer vi må ha klarhet i for å prosjektere elektrodesystemet
Skal tilfredsstille kravene til berøringsspenning
Avstanden «a» er lik dybden ned i bakken som måles.
Dr. F. Wenner publiserte i 1915 metoden i Bulletin of Bureau Standards
Presiserte at dersom forholdet mellom dybden på spydene og avstanden mellom spydene ble endret, måtte også formelen endres
- Andre formler for ringjord, strålejord og kombinerte elektrodeformer (eks. Kråkefot)
- Formel beregner den forventede overgangsmotstand for elektroden når denne er etablert.
Riktig plassering av jordelektrode kan redusere verdien for overgangsmotstand betraktelig
Viktig å huske på at dersom elektroden skal fungere både som berøringsbeskyttelse og impulsjord, må avstanden fra elektroden til det den skal beskytte ikke være for stor (helst rett under).
Når ingen av de 3 første betingelsene er oppfylt, må den reelle berøringsspenningen UT beregnes eller måles
Resistiviteten har innvirkning på tilleggsimpedansen ved beregning av antatt tillatt berøringsspenning
Kan benyttes når det ikke er mulig å måle/beregne berøringsspenninger på annen måte.