1.

Phase angle in a C.T. is defined as ____________(a) \(\frac{180}{π} [\frac{I_m cosδ}{nI_s}]\) degrees(b) \(\frac{180}{π} [\frac{I_c sinδ}{nI_s}]\) degrees(c) \(\frac{180}{π} [\frac{I_m cosδ – I_c sinδ}{nI_s}]\) degrees(d) \(\frac{180}{π} [\frac{I_m sinδ – I_c cosδ}{nI_s}]\) degreesI had been asked this question during an online interview.My doubt is from Errors in Current Transformers in section Extension of Instrument Ranges of Electrical Measurements

Answer»

The correct choice is (c) \(\frac{180}{π} [\frac{I_m cosδ – I_c sinδ}{nI_s}]\) degrees

For explanation I would say: During power MEASUREMENT, there EXISTS phase angle error in a C.T. The phase angle is defined as

Phase angle = \(\frac{180}{π} [\frac{I_m cosδ – I_c sinδ}{nI_s}]\) degrees.

where. Im is the magnetising component of the excitation CURRENT

Ic is the core loss component of the excitation current

Is is the SECONDARY WINDING current.


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