Electric power industry consulting
There is one important concept in the calculations of power transmission lines – this is the equivalent depth of current in the ground (Dg). In symmetrical operating modes (normal mode and three-phase short circuit), there is no electric current in the ground, and this depth is not interesting to us. However, in any unbalanced modes
One of the weak points of cable lines is cable joints and terminations. Despite all the efforts of specialists who develop and install the joints/terminations, there are still many damages. The consequences of damage will vary depending on the location features. There are at least the following typical locations:1️⃣ Joints in the ground.2️⃣ Joints in
The materials of the outer sheath of cables usually differ depending on whether the cable is laid in the ground or above the ground (in places where oxygen is available). To avoid cable fires (for example, due to a short circuit), cables for open laying are provided with a non-flammable outer sheath. However, when laying
To design the cable line, we need to pass the following stages:✅ Evaluate the electrical strength of the cable outer sheath (jacket) and agree on what is the permissible voltage on the screen.✅ Select the grounding/bonding scheme of the screens (number of sections, cycles, etc.)✅ Perform the thermal calculation of the cable line and select
The reliability of cable lines depends on a number of factors:1️⃣ Design (including calculations);2️⃣ Production and delivery;3️⃣ Cable laying and termination/joint installation;4️⃣ Cable operation (testing, monitoring, diagnostic etc);5️⃣ Unpredictable actions of third parties. Mistakes at any of these stages can lead to serious financial losses: damage to the cable, the need to repair the damaged
In 110-500 kV networks with a grounded neutral, cable line lengths from 0.6 to 1.2 km are considered as “bad”. The reasons are simple – for lines more than 0.3-0.6 km, single-end screen grounding can no longer be used (due to the dangerous voltage Us induced on the screens during a single-phase short circuit external
We have to design the cable length that the customer wants. However, let’s discuss which line length would be particularly inconvenient for us and why. The answer to this question depends on the voltage class and the method of neutral grounding. Today, let’s only discuss 110-500 kV networks with a grounded neutral. For such networks,
All the experience allows the author to state that the global metal-oxide surge arrester (MOA) industry is in dire need of simple MOA application methods, but, instead it, is developing endless editions of IEC 60099, adding details to an already complex document that contains dozens of MOA characteristics. At the same time, IEC 60099 does not divide
There are projects where reserve cables or reserve pipes/ducts are provided (empty or with a cable in them). Of course, this complicates the project and makes it more expensive, but maybe it’s worth it? It looks like we are talking about “insuring” a cable line in case of trouble, but the problem is that even
Our industry has excellent international standards (IEC) and excellent software. Both provide us with high accuracy calculations. However, despite the precise methods, can we be sure of the results of the calculations? Of course not! At least because we don’t always understand which source data to use in calculations. If we do not have accurate