Zero Phase Sequence Impedance :-
Zero-sequence current and voltage values are important quantities to provide proper relay protection of power lines and substation equipment. Zero-sequence quantities having any real significance generally occur only when a power system becomes unbalanced due to non symmetrical power loading or because of a fault.
For a three-phase power system, zero-sequence current flows when one or two phases are faulted to ground. The correct operation of ground relays requires proper zero-sequence relay current and (for directional relays) polarizing quantities during the fault.
Delta-wye transformers with grounded wye neutrals are the major sources of zero sequence-current flow within a power system. Depending on a transformer’s configuration, zero-sequence currents can flow through the transformer, from the transformer, or both.
To describe zero-sequence impedance testing on a transformer, a grounded wye (sometimes called a star configuration) connection is used. Zigzag transformers are tested for zero-sequence impedance by the same test connections.
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Our lab is well equipped, meeting National/ International Standards and accredited by NABL (National Accreditation Board for Testing & Calibration Laboratories) under Dept. of Science & Technology (DST), Govt. of India, New Delhi.
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