This is how zero sequence current is eliminated in differential protection of Transformer. In case of single line to ground fault in STAR side, fault current in line will contain zero sequence current component but due to DELTA connection of CTs, this zero sequence current will circulate around the DELTA loop. This also have one more advantage. Where from its come or hows generated in delta?
This concept is useful in Transformer having earthed Star winding. Zero sequence current was x A.
An example is a three-phase wye-grounded-delta transformer connected to the line on thewye side. Since 100 A of current is flowing in winding PN of star side, therefore, the current in corresponding delta side of winding AB will also be 100 A as voltage ratio is assumed unity.
The source provides no positive or negative sequence current to any fault. When the system fails, the three phases become asymmetrical, then the decomposition of the amplitude of the negative sequenc. Similarly in star side of Transformer, CTs are connected in DELTA to have phase correction. �Q��j�N�[�8�7>P]����0�����Cx\��;�#đ�Y��n�x{́aZV5�"�oN�y*RPY;�~`�a����Y��4��L�{ճ����x@D �WU��̷c�n���DЙʑ$�g��;&Sה%���h����an2� �=�t�w!
Thank you so much… I am an engineer working in 400kV substation.
This will result in no zero sequence current component in I’1, I’2 and I’3. )=7hA�(E�ɪ�y�j�)Dmd`��`�@]rR����f���B��{A����l�כ���>�T!�/��O���Vvaڕ�m+�-ɺ�1�Q�h�n�9��f�U�vD�v���>P�C?� ��R�.B�ڷ�߬���|��Ԍx^����y��Q�qמ�GgP�9j(�SC��aRjd���u�V�=�T�[G���+�ȟ�EЂT.���w��x���r��jܘ�����(��Q���m"��Y�b�b;�����X}�~��[e�0%p|����}�'�z�@Ǡ�IS/N�5Qֈ�(te��9����Fv�[��iJ�Yg\KD�n#��?�������:���oi����ԡ Thus a differential current of x A will be sensed by the relay and will cause the relay to operate though the fault is not in the zone protected. �hEU���A�@ʏ��m��г���_�7�47N�Om3�����g/��M%�Q��9���7�l�y ?KVʀ�ťdBF$7)?��8\�vs7�^:g[��e g�~����ҵB �� X��n���5�O���#`J�� �AHm$ ���i8�p@���8̀*���-�$lґ�i� ��h�*1�N�ֻ�uYN/���t4��;��M4����Z You can use a very low ratio (e.g. Check the setting. It’s quite easy.
Zero sequence filtering is a concept used to eliminate zero sequence current component from the secondary current of Current Transformer used in Differential Protection of Transformer. On the high side it is Star-Delta while the low side is Star-Star. Thus a differential current of x A will be sensed by the relay and will cause the relay to operate though the fault is not in the zone protected.
�oZh~�e).���. But the current in the star side of phase PN = 100 A. Therefore in line current of delta side of Transformer, there will not be any zero sequence current. Let the fault current be 100 A. As we know that during single line to ground fault, the fault current has equal positive, negative and zero sequence current component.
Therefore if filtering is enabled, then relay input for differential calculation will be (100 – x) A in Star side of Transformer and that in Delta side is (100 – x) A. This will result in no zero sequence current component in I’, But mind that for relay to filter out zero sequence current, we need to enable this feature provided in the, Line Loadability – Universal Line Loadability Curve, What is IGBT? If-0 = zero sequence current; X2 = zero sequence reactance; By principle, the single line to ground fault will develop and equivalent network where all sequence networks are connected in series. May I know for the zero sequence filtering to work, how should my ICT connection be? In case of a line to ground fault, system draws an unbalance current and Earth fault relay trips after detecting zero sequence current above 20% Full Rated current.
I. sequence impedance source such as a grounding transformer providing only zero sequence current for ground faults.
What is the Need for Zero Sequence Filtering? CTs in Delta side of Transformer are connected in STAR while that in STAR side, it is connected in Delta. CTs in Delta side of Transformer are connected in STAR while that in STAR side, it is connected in Delta. on the measurement point to the earth between the size of the impedance. Commentdocument.getElementById("comment").setAttribute( "id", "a2eb1d8cb21fcd791d32636a1d75bb1a" );document.getElementById("dc65a5f484").setAttribute( "id", "comment" ); Subscribe to our mailing list and get interesting stuff and updates to your email inbox. In case of single line to ground fault in STAR side, fault current in line will contain zero sequence current component but due to DELTA connection of CTs, this zero sequence current will circulate around the DELTA loop. In modern Numerical Relays, this elimination of zero sequence current do not need such connection of line CT secondary. 10/1A) zero sequence CT as CT saturation is not a concern if regular earth fault protection is implemented using the phase CTs.
This will create an imbalance in the differential current and may lead to actuation of Differential Relay even in through fault condition. zu��a}�3���(2 _�L��n�"aH��M�N��i�u�-�L��@�8��u�z�7��F�F�wB|2]��c�&�ː���`8�Wܙ4w:�*���R68�]�tn�����J�]]aU�+���c�tb��"Þ�� U�V��4��� �9��� �:h蚥��:���LV_������O}Q8K�ף��z���ž�*���g� ��}ˆ�&(��������qM���|�7�ͻ�~�J�M�X�g:�n(�s�}���.�5L:+&�k+� �îH�&ߪa���ګs.ʚP:�w1NS�����p��l�M��N)�/���ޏ�������!��S����ez�����bd�J�3w. !��` ��8��-5< �b 7��3Y�����a���D�tB]Z��,��q�T:��`���@�� m���:5��E�O�����.9��v�͗w�����{rLօ ��� u��@o �h)�LNy��SP��up�_��=K�*� %c>Fǜn�6��A�3����+K�{n]�/����D����̛gibRz����9�H�����~�u�:�N��]�����e0ʳ��ȸN�P�u�3O�vk`��!8)~ *�]�y�g��R��,�:�aB����r��Ƀ�D2k����v A setting of 1%-2% Full Load Current is obtainable with sensitive ground fault protection while a setting of lower than 10% Full Load Current (residual ground fault protection) normally result in nuisance trips. Therefore, line current in AS = (100-x) A. clear the limitations of the zero sequence directional polarizing method and clearly show the importance of the detailed modelling of protective devices in network protection studies.
zero-sequence ground-fault current • Do not respond to dc-offset caused by starting motors • Do not respond to harmonic-frequency components ∑ − = # $ % & ’ ( π = × m 1 n 0 m 2 n I(n) sin m 2 Ip The Discrete Fourier Transform has these characteristics .
we respect your privacy and take protecting it seriously, Zero sequence filtering is a concept used to eliminate zero sequence current component from the secondary current of Current Transformer used in.