What Should Be the CT Turns Ratio for a 30MVA Transformer in a Railway Network?

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In summary, the ideal turns ratio for the differential protection of a 132kV to 50kV single phase 30MVA transformer is 2.64:1, based on the 30MVA rating and using 1A CT inputs.
  • #1
Fisher92
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Hi,
A 132kV to 50kV single phase 30MVA transformer supplies an electric railway network. It is to be protected with differential protection using an electronic protection relay that accepts 1A CT inputs. If the CTs are to be continuously rated for a 40MVA load what would be the ideal turns ratios?

I do not know weather the ratio is based off of the 30MVA or the 40MVA?? From there its easy.

I think since its still a 30MVA a tx i should use that - but since its differential it really makes no difference?

Its for a quiz.

Thanks
 
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  • #2
!Yes, the turns ratio should be based on the 30MVA rating. Differential protection does not depend on the current rating of the transformer. The ideal turns ratio would be 132kV/50kV = 2.64:1
 

Related to What Should Be the CT Turns Ratio for a 30MVA Transformer in a Railway Network?

1. What are CT ratios and how are they used?

CT ratios, also known as current transformer ratios, are a measure of the ratio of primary current to secondary current in a current transformer. They are used to step down high currents to a lower magnitude that can be safely measured or controlled.

2. How do I calculate the CT ratio for a given transformer?

The CT ratio can be calculated by dividing the primary current rating by the secondary current rating. For example, if a transformer has a primary current rating of 100 amps and a secondary current rating of 5 amps, the CT ratio would be 100/5 = 20.

3. What factors should be considered when selecting a CT ratio?

The primary factors to consider when selecting a CT ratio include the maximum primary current, the desired secondary current, and the accuracy and burden requirements of the application. It is also important to consider the physical size and cost of the transformer.

4. How can I ensure the accuracy of CT ratios in my measurements?

To ensure the accuracy of CT ratios, it is important to calibrate the transformer regularly and make sure it is not overloaded. The burden, or load, connected to the secondary circuit should also be within the specified range for accurate measurements.

5. What are the common applications for CT ratios?

CT ratios are commonly used in power systems for measuring and monitoring currents, as well as in protection systems for detecting faults and overloads. They are also used in industrial and commercial settings for energy management and process control.

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