High Voltage Cable Design

December 22, 2020

2 mins read

Wind Farm Dynamic Cable Ratings

This article explains why dynamic ratings are important when dealing with long AC cables for wind farms. An example calculation of a dynamic rating which uses the measured load profile is given.

High Voltage Cable Design

October 7, 2021

3 mins read

Effects of Controlled Backfills on Cable Current Ratings

The effects on the current rating of cables buried in soils with different thermal resistivities are examined with software using the finite element technique.

Earthing Design

December 13, 2021

3 mins read

Lightning Strikes to Buildings with Earthing Systems

This report shows the effects of a direct lightning strike to an air terminal installed on top of a building which is connected to a buried earthing system.

High Voltage Cable Design

March 2, 2022

3 mins read

Current Rating for Groups of Circuits Installed in Air

The calculation of current ratings for groups of (multiple) cable circuits require the quantification of the mutual heating component between the groups of circuits. This example is for multiple groups of circuits in air on the same cable ladder. This article will discuss the IEC 60287 approach.

Earthing Design

October 7, 2020

3 mins read

Modelling earthing rods surrounded with bentonite

Using bentonite to reduce resistance Sometimes it is not possible to achieve the desired reduction in ground resistance by adding more grid conductors or ground rods. An alternate solution is to effectively increase the diameter of the electrode by modifying the soil surrounding.

Earthing Design

August 22, 2017

4 mins read

Use of Rods to Improve Grid Safety

To show how and when earthing rods can be used to improve the safety of earthing grids by reducing the grid resistance and potential rise (GPR) as well as surface, step and touch potentials.

High Voltage Cable Design

January 9, 2023

4 mins read

Derating of 400 kV Buried Cables from Ventilated Trough

New 13 kV power circuits will be installed in an unfilled trough with ventilated covers. These new circuits will cross with existing buried 400 kV cables at approximately 90 degrees with a continuous current rating requirement of 1136 MVA (1640 A) per phase for all seasons.

Earthing Design

July 7, 2021

3 mins read

Earth Grid Design for Frozen Soils

Soil resistivity is one of the most critical factors affecting earthing and grounding system performance and safety. In cold climates, the top-soil layers may be frozen during the winter or spring seasons, and resistivity may increase to as high as 10,000 Ω.m in the frozen soil layers. This can give rise to significant touch voltage hazards during an earth fault.

Earthing Design

May 30, 2022

3 mins read

Soil Frequency Dependency During Lightning Strikes

The effects of lightning strikes on earthing or protection systems designed to IEC 62305 can be modelled using an equivalent single frequency from 25kHz up to 1MHz which gives similar results to a time-domain approach. This article provides the frequency and current values to be used for modelling lightning.

Power Systems Technical Articles

Choose the article category

Wind Farm Dynamic Cable Ratings

Effects of Controlled Backfills on Cable Current Ratings

Lightning Strikes to Buildings with Earthing Systems

Current Rating for Groups of Circuits Installed in Air

Modelling earthing rods surrounded with bentonite

Use of Rods to Improve Grid Safety

Derating of 400 kV Buried Cables from Ventilated Trough

Earth Grid Design for Frozen Soils

Soil Frequency Dependency During Lightning Strikes

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