Answer / pillay

it should be preventive maintenance,
what transformer.
any way like usual electrical installation.
1)check all termination for good fitting and sign of any damage
2) Check all insulation.
3) check all other associated equipments like cooling fans
thermometer. protection relays .
4)check for physical condition of the transformer for rust
or leaking oils
5) check for condition of the insulating transformer oil,
bushes and connecting cables and switchgear.

Sir We have a REF relay connected to 10MVA(Y-Y) Transformer.on External earth fault REF relay trips along with earth fault relay.The REF relay has no complant as we tested relay.Why is it happening?

3 Answers   KSEB,

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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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what is the roll of power factor in induction motor.

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