High Voltage Cable Design

December 6, 2022

10 mins read

Estimating Cable Life Expectancy

Most power cables have a design life of between 20 to 30 years. If the cables are not fully loaded, they are expected to last beyond their design life. The insulation is the weakest part of a cable. Montsinger's Rule states: Insulation life is halved by a temperature increase of 8 to 10 ˚C. An example calculation using the Arrhenius equation is provided.

Low Voltage Design

November 21, 2022

3 mins read

Touch Voltage Calculations for LV Electrical Systems

The definition of “touch voltage” is the voltage between accessible exposed and extraneous conductive parts that may lead to the risk of electric shock in the event of an electrical fault. This article covers AS/NZS 3000, BS 7671, and NFPA 70E rules concerning touch voltages and provides the equations for calculations.

High Voltage Cable Design

November 16, 2022

7 mins read

Cable Current Rating in J-Tubes for Offshore Windfarms

This article explains how to calculate the current rating of cables in J-tubes. Typically J-tubes are the thermal bottleneck of submarine power cable routes.

High Voltage Cable Design

July 6, 2022

8 mins read

Current Rating of Cables in Multiple Backfills Using the Finite Element Method

A new calculation method based on FEM and IEC 60287 for current rating of HV cables in soils with multiple different thermal resistivities is explained with an example calculation. Modelling the different soil thermal resistivity zones (multiple backfills) is important for obtaining accurate cable current ratings.

Low Voltage Design

June 6, 2022

12 mins read

Solar PV systems – DC cable sizing with examples

DC cable sizing has significant implications on a PV system's performance, total cost, and safety. Example calculations of Current Rating and Voltage Rise have been provided.

Arc Flash

May 30, 2022

2 mins read

Typical Working Distances for Arc Flash Calculations

One of the main factors determining the severity of an arc flash injury is the proximity of the worker to the arc flash, also known as the working distance. Working distances from AS (ENA), IEEE, NFPA and DGUV Standards and Guides have been provided.

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.

High Voltage Cable Design

May 23, 2022

5 mins read

Current Rating of Cables in Ventilated Tunnels

The methods for calculating the current rating of multiple cables installed in ventilated tunnels are explained with example calculations. Overall tunnel length and air velocity inside the tunnel have a significant impact on cable current ratings.

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.

Power Systems Technical Articles

Choose the article category

Estimating Cable Life Expectancy

Touch Voltage Calculations for LV Electrical Systems

Cable Current Rating in J-Tubes for Offshore Windfarms

Current Rating of Cables in Multiple Backfills Using the Finite Element Method

Solar PV systems – DC cable sizing with examples

Typical Working Distances for Arc Flash Calculations

Soil Frequency Dependency During Lightning Strikes

Current Rating of Cables in Ventilated Tunnels

Current Rating for Groups of Circuits Installed in Air

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