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 works as electrical power transformer? Its may your question. It’s true we know electrical power cable works as a capacitor; because the condition to be a capacitor two metallic component need to place in parallel. 

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

Our today’s article is “ELECTRICAL POWER CABLE IS AN ELECTRICAL TRANSFORMER” that may someone not thought before. We are familiar with various transformers that transfer the electrical power from primary side to 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 exist a transformer we need primary winding and secondary winding; no matter way how much turn 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 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 happen if cable shield grounded in single point or multiple points, or even not grounded in any point?

Consider single point shield grounding:

If the shield is only grounded in 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 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.  


Other way we can say the current in the shield increases as the amount of metal in the shield increases. The voltage keeps in zero level.
How Electric Cable works as a Transformer

One of the most important factors for “electrical power cable is an electrical power transformer” if shield is not grounded then always voltage will stays in shield, if voltage increase its may reach dangerous level. 

Typically along the power cable there are many others utility uses metallic elements like gas pipe line, water pipe line, other electric or communication lines etc. 

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

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