Graffeo - CT question

[applepieordie]

Hi, this is a figure in the 2016 printing of the Graffeo book, page 148.

Is there a typo in describing the direction of current above the CT on I2 side? The description is the same before and after the fault...why? 

I tried checking the errata on Graffeo's website but this page is not mentioned.

Thanks in advance!

View attachment 9728

 

[rg1]

Hi, this is a figure in the 2016 printing of the Graffeo book, page 148.

Is there a typo in describing the direction of current above the CT on I2 side? The description is the same before and after the fault...why? 

I tried checking the errata on Graffeo's website but this page is not mentioned.

Thanks in advance!

View attachment 9728

There does not seem to be anything wrong. He is assuming the that the transformer is a part of large network and if a fault occurs in the Transformer it will be fed by both primary and secondary  sides. So I2 on primary side (of CT) is coming into Transformer on internal fault condition which is opposite in direction to the case when Transformer was healthy (Top fig). This will also make CT secondary to change its direction and hence operating coil(middle one) will have the current I1+I2. If it does not make sense, I will put a figure tomorrow. The figure could have been more explanatory than the existing one.

 

[BigWheel]

Hi, this is a figure in the 2016 printing of the Graffeo book, page 148.

Is there a typo in describing the direction of current above the CT on I2 side? The description is the same before and after the fault...why? 

I tried checking the errata on Graffeo's website but this page is not mentioned.

Thanks in advance!

View attachment 9728

The figure itself is correct, but you are also correct in pointing out the erroneous description.

The text box above "I2 Pri CT" is wrong. The box should read, "Ip into polarity side" and "Is out of polarity side" (i.e., the description above "I2 Pri CT" should match the description above "I1 Pri CT," as the current directions match under fault conditions).

 

[applepieordie]

thanks for the replies gentlemen