WAZIPOINT Engineering Science & Technology: Electrical Power Cable Is an Electrical Transformer

Saturday, August 1, 2015

Electrical Power Cable Is an Electrical Transformer

Electrical Power Cable Is an Electrical Transformer

How electrical power cable work as an electrical power transformer? It may be your question. It’s true we know electrical power cable works as a capacitor; because the condition to be a capacitor two metallic components need to be placed in parallel. 

For power cables, normally two or more single-core cables are played in parallel, or for a single cable itself there are core and metallic sheaths that are parallel which form a capacitor. So, we know the power cable itself is a capacitor.

Today’s article is “ELECTRICAL POWER CABLE IS AN ELECTRICAL TRANSFORMER” which may someone not have thought of before. We are familiar with various transformers that transfer the electrical power from the primary side to the secondary side by connecting magnetically, not electrically. Now today it’s pushing to think about the fact that a cable may also be a transformer.

Okay, to create a transformer we need primary winding and secondary winding; no matter way how many turns in the winding, it’s may many or simple one turn!

So for power cable; when current flows in the central core conductor that current produces electromagnetic flux in the metallic shield of the cable or in any other parallel conductor. This becomes a “one-turn” transformer.  When the shield is grounded multiple times since a circuit is formed and current flows.

What happens if the cable shield is grounded in a single point or multiple points, or even not grounded in any point?

Consider single-point shield grounding:

If the shield is only grounded one time and a circuit is not completed, the magnetic flux produces a voltage in the shield and no current flows through the cable shield means the secondary of the cable transformer. The amount of voltage is proportional to the current in the conductor and increases as the distance from the ground increases.

Consider multiple-point shield grounding:

If the cable shield is grounded two or more times means completes a circuit; the magnetic flux produces a current that will flow through the shield. 

The amount of current in the shield is inversely proportional to the resistance of the shield.  

Another way we can say the current in the shield increases as the amount of metal in the shield increases. The voltage is kept at zero level.

How Electric Cable works as a Transformer

One of the most important factors for “an electrical power cable is an electrical power transformer” If the shield is not grounded then always voltage will stay in the shield, if the voltage increases it may reach a dangerous level. 

Typically along the power cable, there are many other utility-use metallic elements like gas pipelines, water pipelines, other electric or communication lines, etc. 

If the power cable sheath is not protected by grounding, induced voltage may electrify them; especially when a short circuit will happen.

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