Answer / sudhakar g

Beacuse the ct output can use for relays, load managers or
any other devices which can consume low
current.........they also mention the burden and class like
15VA and CL 1.0....

Answer / alan jenkins

Traditionally protection CT's were 5A output and a high vA because they had to drive electro mechanical protection relays which had a high burden, However with modern Digital and Numerical Protection relays the operating burden is very small hence the CT's dont have to be as big as they used to be. Also on modern distribution networks, fault currents can be very high and 5A CT secondary currents were also equally high.
much favoured on new and refurbished equipment is 1A CT's.

Answer / guest

230v

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Dear all, I just want to ask an expert on this forum for some insights. For the magnetic balance test, when applied voltage on a Delta-Star transformer e.g. Dyn11, the following relationships apply for HV side: 1.  H1-H2 = H2-H3 H3-H1 2.  H2-H3 = H3-H1 H1-H2 3.  H3-H1 = H1-H2 H2-H3 For the LV side also: 4.  X1-X0 = X2-X0 X3-X0 5.  X2-X0 = X3-X0 X1-X0 6.  X3-X0 = X1-X0 X2-X0 Is there a similar pattern for Y-d, Y-Y, D-d? And how about Y-z, D-z, Z-y transformers? I've tested a YNzn5 transformer and for LV side I don't see the pattern. In this particular case I got for LV side the following (see values below): H1-H0  H2-H0  H3-H0    X0-X1  X0-X2  X0-X3 128.0  119.9  7.2      29.2   13.3   15.8 70.7   128.4  59.2     23.4   22.0   3.6 7.2    120.1  128.1    13.4   29.3   15.8 What is the relationship here for LV? For row 1 I see the relationship, for row 3 I also see but it's shifted, but for row 2 I don't see such relationship. Any suggestions, answers, someone?

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