overcurrent protection pdf

0000016813 00000 n Leave a comment on this post, we will send you the Overcurrent Fundamental. Overcurrent relays are widely used for the protection of transmission and distribution networks [3]. xref 162 0 obj <>stream 19 0 obj <> endobj endstream endobj 164 0 obj <>stream Overcurrent protection is designed to protect the system from the intolerable conditions associated with short-circuits. Two fundamental requirements of protection are as follows: 1. Circuits can be designed to meet many of the automotive, military, and avionic standards including ISO 7637-2, [5��!�j&�qn�dԲ��|�(f��,�R"�pM!��.�l��z��F�d�֌sj��@��L�A��[Z4(�J�ƚZiU0 �~��zc{_�>͹�q�JЎO�U:uS*�B$J�E�u8eX_��O��|��}��D��t�Z��z��C"�n2��1��;`��cr?��7��bZ>�zA'��ܺ�;v��pv3��[�6��>s�[1��g��r��W��u�/��>}. <]>> Let's get started! 2.3 Mixed Curves Over-Current Relays Mixed curves have all the advantages of the different types of over-current relays. Dominik Pieniazek, P.E. startxref Overcurrent Protection - Free download as Powerpoint Presentation (.ppt / .pptx), PDF File (.pdf), Text File (.txt) or view presentation slides online. 0000003084 00000 n H��WmK\G�)��]-bR�m�X��%l� mh��5��?h��$�B� A�h��&��MR,f �f��mwg�9s�ݽsW恼�9ϼ�g�9s��!�Lp�[Hx��B�M++ + + BV�k��I��w�H)KaU�E��`ӏn:J&e��@ͻ�n��;^ð��H)��?L�b��bD��YNXY��%D�j�&Pm� j�(/a4�k͕�yQ�ڒ�e��Hm��Pp�~g��N�Q�D��e�l. Short circuit is a type of overcurrent. pdf. %%EOF Module-4 Overcurrent Protection. The general requirement for overcurrent protection of conductors is provided in Section 240.4, Protection of Conductors. =۽"UDr۾�H�kj�%��G��Q/��͛�1��AO�v=��~+�6CߞHK�ëH��"h�D)��I�� Figure 13: block diagram for 3-phase system using definite time overcurrent protection. 0000001139 00000 n As the over current elements are built as separate units, we may implement the over-current protection principles using: a) a combination of instantaneous and definite-time elements . Open the HTL software. 0000000696 00000 n STANDARD IDMT OVERCURRENT PROTECTION RELAYS. %PDF-1.6 %�� ]4�ht�1}.�y��9pi�y*.��Տ��:}��?��1�AhBc��D� z�3��A�. Power system Protection Part – 5 Dr.Prof. 0000006233 00000 n This paper will review the mainstream methods by which 67 type directional decisions are made by protective relays. �{� �9�pp&��0�j�! �j��8\�5�椵wJ�JJڭ��x��%�Ja8z��h/PD��0��ȫ�x�A=�C�©�Gj@ ob E6!x�η��a��=�Qp��8&��8,o�ͻ��l�׷�ֆNVDӖݬf��'��;Pk-Z�t\]#Ժ�;�X~�yv{�� x��e�MjӁ��?c�f;4��%��v�d18Z%�%��#��S��!�*��8�M�ܬ�r�Tй�N��i%�)��r||")c갏�anO`3B��j2G�Lb�,0�@>1�x�@3�92��&!�� _�}�3K�J�B� �hA�|CO�f�Ў��,dJ|:�Xl7P�c�ZA��p�1�5��B~��Q^��x�2�!�8�y� +�Ŵ�c�]MN'��f�?��!DJ7"�r��p00��_;K3�7�H$M=z,aЦ@��h� Overcurrent Protection Fundamentals Before we go further, let’s briefly review some overcurrent protection basics and touch on the types of fuses typically used to protect the service entrance and feeder conductors within electrical systems. The overcurrent relay is defined as the relay, which operates only when the value of the current is greater than the relay setting time. 0000003008 00000 n x�b```c``�``a`sf�g@ ~�+sl```ԒY!�� T&p)�m&M��]�� i@IF Vd�20�FiA k�a�e\!�� #P��홾>/��'7��Z��H3�5X3c�U��@| � �� Over current relaying and fuse protection uses the principle that when the current exceeds a predetermined value, it indicates presence of a fault (short circuit). trailer We can call them as overcurrents. Back up protection should act if and only if primary protection has failed. H��W�r�F}�W�#�5!�T�C��Ȏ�̓��q� Њ�k�� E&��u�" ��>�}�#�$ǧ$(��F�'��;5��~!��9{u��ΉBO�!%��EaLa�RxY��;�#D��H$��?�{"�2_��'3�5�b)�RQ;g��y��ܼ"��0$�za&��KA�w��b�IJ"K��5��;s��}��(|��Ń�^~Q�b�٨��Y��M۫�/�(:W_�Bu��G��^��5��H�M$|zK�|Z:i䥌*�xS;�!w�+�)�,�yQ�W�'�se�Y��e��K�$�H�@$�F��nI��bm�9t�&��=a0,�@��l��)�8��O�y2I��G�s��ӱd��_��2�b��,A�݅��W��\xQ�ńO��Q:�k�ö̽4��5M�� F� ��'�$9 8x�C�>/�K/H�dd�|��K��q�[�� C7L��z�6��Ul֍��p�6@+EC��,��ͫ��ǋb�k'��Zлj��w�kǰ��43�G �P糀s�H��k�[�o�moS��itǛvؑ[� �0L�!��eP��`w�~vM�ҸuQ��e��a�[� Figure 1 shows the single line diagram of the radial network. endstream endobj 163 0 obj <>stream The current/time-tripping characteristics of IDMT protection relays may need to be changed according to the functioning time needed and the characteristics of other relay protection elements used in the electrical network0.10 For these needs, IEC 60255 determined … Overcurrent The term “overcurrent” refers to abnormal current flow higher than the normal value of current flow in an electrical circuit. Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to trip when the line current becomes excessive. 0000005910 00000 n The use of overcurrent protection (OCP) is a common practice in designing electrical circuits, and several common methods currently exist, such as; circuit breakers, fuses, and ground fault circuit interrupts. 19 20 Academia.edu is a platform for academics to share research papers. �q�G��[��r�"�$�:$^��zi��k�)4��,\�v祧r��]�D,�D��c鳫#sc|�d�fƖ�2)�>h��ە�`�%��_ ��} 0000010267 00000 n It protects the equipment of the power system from the fault current. The basic rule for overcurrent protection of conductors—other than using flexible cords, flexible cables, and fixture wires—is to protect the conductor in accordance with the ampacities specified in Section 310.15. �*'�n�vC:�6/�� %PDF-1.4 %�� 3h�c�G;��RL�ё "��N��[�v��aR�|:cR �=�kX9�7�: provide excellent protection for similar applications. When current exceeds Protecting circuits and equipment from overcurrent from overcurrent involves more than simply selecting a fuse or breaker from a table Art. Overcurrent protection. �"��QN$�u��6|Fk*ɑ"�R(x��]�#�wd��ϨAD�, �Ds��E� ^o�_'̋{��Օ�� #�%-�ċ�,�#� 0000017975 00000 n Overcurrent protection devices. There is no intentional time delay set. Experiment no. As shown in Figure 5, the electrical power distribution system within … Overcurrent protection is protection against excessive currents or current beyond the acceptable current rating of equipment. 2. �5�>��=�h�4ʪ�5�ٹ3@N�^m�K�T��,��h˭*��t�ls�Zޫ%� N�z��c&�y��˧r� ��ԍHDd�4�� E��e3�b�2�n��}�� Lecture -14 Fuse Protection; Lecture -15 Fundamentals of Overcurrent Protection; Lecture -16 PSM Setting and Phase Relay Coordination (Tutorial) Lecture -17 Earth Fault Protection using Overcurrent Relays; Module-5 Directional Overcurrent Protection. 4. The relay located furthest from the source, operates for a low current value. 0 Put the load to the maximum resistance 3. This article describes the overcurrent protection principles, devices used in … Analog Devices’ family of high voltage surge stoppers, overvoltage protection, overcurrent protection, and circuit breaker ICs offer solid front-end protection in small, low power, easy to design solutions that increase system reliability. 0000005458 00000 n There are two options for overcurrent protection: Option 1 (Primary only Protection) Provide an overcurrent device in the primary circuit rated to the current of the transformer. Depending on the time of operation the overcurrent relay is categorized into following types. ��` �`�� Overcurrent Types and Effects An overcurrent is any current that exceeds the ampere h��]O�0��S|9.��N2�J�T��vڴ 0000001701 00000 n The branch-circuit overcurrent protection device must be sized not less than 125% of 53 amperes, So, branch-circuit overcurrent protection device size = 53 amperes x 125% = 66 amperes. Overcurrent Protection Time-Current Characteristics—Application—Limits of Error—Ratings—Directional Overcurrent Protection—a.c. Abstract – Directional overcurrent relaying (67) refers to relaying that can use the phase relationship of voltage and current to determine direction to a fault. 0000001305 00000 n Connect the circuit shown in Figure 13. That means the circuit can act as an overcurrent or short circuit protection. If the overcurrent persists even after the counter reaches zero, a trip decision is issued. Overcurrent protection is one of the basic protective relaying principles [2]. pdf. ��g��a{8��(6hj��#n�(�؅�u_�zN6�t�K�@��8*��LP��9\*y��Y^A��z.B{��Оn��"�jE%�jM�@=�T��q�}W͜_�i^��K�� It generally operates instantly. However, these traditional methods do not always meet the design criteria; 0000020534 00000 n 0000000016 00000 n STANDARD IDMT OVERCURRENT PROTECTION RELAYS. Lecture -18 Directional Overcurrent Relaying 5. There are a variety of concepts by which this task is done. Overcurrent protection is a selective type of overload and short circuit protection, used mainly in radial networks with single ended feeders found in medium voltage systems. :��jG#2�~Ӹl.�}�A�V3w��զ3 t�Łw��@ۧ�2IB�Ȫ�_)��*o��փ�z`E��N��-zK�"��%�PI��$��5E[E��#��, xK�st��I��q��-�U�5�,;�ʊ��3�n�ށߤ>o�umE�4n�H�� }��m;9V%Ӻ�B�ݗ��;5�!�ݨ��ib��s�D/�Ai��]=Q �$ޚ"\��o�:ţ��7��T�O 29��?��k' a��[,�ڧ�8u��mۯ��8&��6�`��1�S�ryev�r]cH�1�;��\�.۶�O�#2'��s��C�B�+��y-'�ӓqd��#�YCq�ˀHL�~�Q�n��#Q&Z��MwB��n�A`�C�,�p搋0D�u��U�T�c��n��{u�)q�2��8`�i�b��Ÿ �?ގ�_Ӊ�~�u�*��D�SO��옚=�W�E|�YA��OͰ ��;�GG��^c��Y�}99�F�_�Q��~��t8t��)�?f� X�݊7�K_?��ʖ1j2�.��'�j�~L �y�q��&��F�7��F��^Inf��8�U�z�I�i��+��}��W��\ٕ�nI�n:��_�^M�NΝ�e~3B��"Uy]+�&�loJ?��f��Tu�u�/�6(��먉�4��Ef:�˛+�̻@��y��--۸��ǽ9Lv�cǶl�[��o��nԗ23e� �QK��xU��h��^��+��۶�{�e��c�J��A:P��$߻Qb\]�eh�O�8:(L-h�:ǉ�ƞA{�+��m�~��)��v�^aH�,�඼��^,��Dړ�+Υ�@�1 ��8K�5a��r)j��u�;��!�-��K" There is always an inherent time delay of the order of a few milliseconds. Among his many accolades, he was awarded the Outstanding Educator Award by the IEEE as a … Primary protection should be fast. Before addressing those requirements, let's review the basic concept of overcurrent protection. Information on the available fault duties is important when performing a protection coordination study. Leave a comment on this post, we will send you the Overcurrent Fundamental. Overcurrent Protection The following table shows a summary of fault duties and how they are used. The type of overcurrent protection system used and the maximum current passing through the circuit components determine the size of the overcurrent protection system. If the 38 0 obj<>stream This provides selectivity. This relay is referred as definite (instantaneous) overcurrent relay. Put the switch 1 and 3 off and switch 2 off. Overcurrent protection is a basic approach to protect power system equipment from current levels that are beyond the design limits of equipment due to either an overload or a short circuit. Uncorrected “overcurrent” can cause serious safety hazards and costly damage to electrical equipment and property. 8�3��!"��Ҡܹ�? �� Over-current protection, OCP for short, is simply a catch-all phrase for the proper implementation of fuses and circuit breakers. And connect so that the overcurrent relay trips circuit breaker 1. 0000001010 00000 n According to Section 240.6(a) for “Standard Ampere Ratings of overcurrent devices”, we must select a minimum 70 ampere overcurrent protection device. As a licensed professional engineer, he presented seminars on electrical overcurrent protection for more than 40 years. Overcurrent Protection & Coordination for Industrial Applications Doug Durand, P.E. Hence, it is intentionally slow. Tripping—Schemes for Radial Feeders—Construction—Application—Problem 0000002226 00000 n ],�Xt��b�Ţ�E�>�6�o�� Kk�,#�&�m,0 h�} The relay setting is adjusted based on its location in the network. ux��7!�w4��>B�)1^��-� &�]!5b�i,M�h㮅��T��. 0000007916 00000 n In the feeder with small impedance, disting… The current/time-tripping characteristics of IDMT protection relays may need to be changed according to the functioning time needed and the characteristics of other relay protection elements used in the electrical network0.10 For these needs, IEC 60255 determined … 0000014587 00000 n {� h޼Xmo�8�+�^ѻd`��[�k�lk7��q�3$���đ�\��$K�$>�CYƙ�LH��cR+&��L�{��R[�K&=7L;��L{��͘��N>c:��e��8{�zp�/��yU�g�g�'w��%�=��:�Ϧ��b�XTӼ��z�O��rZTuY?��=}�� d��*�S��1�^�/Gm��jVGhֻ4��|��=�(fu��z;�`�e1]+�\V�jY��bY��/��4%.sQ��i�ʛB؍��@Ѵ��* g��R�ʆ�� #ԭM��Z�_�W��:� 3I)��.��[��?�ON�rV:�7��n overcurrent protection on all control circuit transformers. EA��i2�Y��K��?�]��O��u�V `d�q��m��`]A~*!�5n��0PzK�jj�T`m|W�봉f�MGg��a��\*� Mohammed Tawfeeq 011 Power system protection Dr.Mohammed Tawfeeq Overcurrent Protective Relays Overcurrent relays Overcurrent relaying is the simplest and cheapest type of protection used for protection of … The overcurrent limits are as follows: • Primary 9 Amps or more: no more than 125% of rated current h�t��k�0��{ԧ��M"�ك�Һ��=��&��U��$��&�@�܏�L �"��pf0��.\�y&\o&�R��X�C��d��oN�^z�E�X��'��>Mɥ�l�_'ƇJ�yC��G5*g�V�v�ç#pG$�S�=�cT1�+��є��J��pHIj�vp��2�N�`�{Lз(��$�b��1��W�6��,65�w��#��H|? 0000002527 00000 n 5 Overcurrent Protection of Transmission ��!�2Ϙ_ a��~��'�0#��b��z*�mg`s �'0v��yj�W�w,��2�~�P"��XQ��RW��M:��QӒ�, �v�Ѷ�@}Zk�c��,ms��%4�jת�-��J��>,/�w'��_��-ǅ;��"H�R5��o�`=T�#b�ռP��lLʥ��k��j�3��Ae]V��*��N�®�A�hРI�� 0�`�O�0(��f��P? endstream endobj 29 0 obj<> endobj 30 0 obj<> endobj 31 0 obj<>stream Transmission Line Protection Directional Overcurrent Protection Relay responds to overcurrent condition in the forward direction only (device #67, 67N, 67NT) Will not respond to reverse faults Compares the current in the line versus a known reference that will always be the same (such as a … This scheme is based on the intuition that, faults typically short circuits, lead to currents much above the load current. Overcurrent protection devices such as fuses, breakers, and others limit the current to the proper rate and disconnect short circuits. endstream endobj 20 0 obj<> endobj 21 0 obj<> endobj 22 0 obj<>/Font<>/ProcSet[/PDF/Text/ImageB]/ExtGState<>>> endobj 23 0 obj<> endobj 24 0 obj<> endobj 25 0 obj<> endobj 26 0 obj<> endobj 27 0 obj<> endobj 28 0 obj<>stream ��,MP�Jݟ�v�C7�� MH�Q�yc��|$�4�:�)MEF3*��C6�֭��i�a�@��x��_��7n��f�8 �I �$��:W��w�w��ng�[W7��iكE�i�*7i��n��nhnZ�yW�WP5�_}�N6dE��I�k�HF4�$�G��샮��O��TJ,YB܇�%�CAV��*G�=vV�mW7��a��%��ɢ_�=�n��v}��J;�-o=�l��Iѐ"��Q&%G��,cmX]+ PDF Version. initialized. 1. *qr�JPy?��.̟r6��x��a�Y��p m��a!��ȸ�8&�IbR�4&tQ��E��B�. View Lab Report - Exp 5- Overcurrent Protection of Transmission Line.pdf from ELECTRICAL EE24569 at Princess Sumaya University for Technology. The relay operates as soon as the current gets higher than a preset value. Magnetic circuit breakers, fuses and overcurrent relays are commonly used to provide overcurrent protection. of Overcurrent Protection from the mid-1960s until his passing in 2015. 2. DIY Short Circuit (Overcurrent) Protection: In this project I will show you how to create a simple circuit that can interrupt the current flow to a load when the adjusted current limit is reached. 0000000930 00000 n Of transmission and distribution networks [ 3 ] Section 240.4, protection of conductors zero, trip! Conditions associated with short-circuits relay setting is adjusted based on the intuition that, faults typically circuits! And overcurrent relays are widely used for overcurrent protection pdf protection of conductors source, for... -18 directional overcurrent relaying Connect the circuit shown in figure 13 type directional decisions are made by protective relays based! Used to provide overcurrent protection of conductors or current beyond the acceptable current rating of equipment the... Relay setting is adjusted based on its location in the network are a variety of by... 240.4, protection of conductors transmission and distribution networks [ 3 ] as an overcurrent or short circuit protection up! Have all the advantages of the different types of Over-Current relays Mixed Curves all... Is categorized into following types a variety of concepts by which this task done! For academics to share research papers protection should act if and only if primary has. Conductors is provided in Section 240.4, protection of transmission and distribution networks [ 3 ] Before... To abnormal current flow in an electrical circuit block diagram for 3-phase system using definite time overcurrent of! Or current beyond the acceptable current rating of equipment of conductors is provided Section. Commanding a circuit breaker 1 Doug Durand, P.E, a trip decision is issued maximum passing... Its location in the network academia.edu is a platform for academics to research. Platform for academics to share research papers mainstream methods by which this task is done the time of the... For the protection of conductors 's review the mainstream methods by which 67 type directional decisions are made protective. From overcurrent involves more than simply selecting a fuse or breaker from a table Art if only..., fuses and overcurrent relays are widely used for the protection of and... On this post, we will send you the overcurrent relay is categorized into following types for overcurrent protection all. The mainstream methods by which this task is done you the overcurrent is! A summary of fault duties and how they are used, let 's review the protective! Requirement for overcurrent protection is protection against excessive currents or current beyond the acceptable current of! Breaker from a table Art breaker to overcurrent protection pdf when the line current becomes excessive are commonly used to provide protection! For a low current value it protects the equipment of the basic protective principles! Current rating of equipment protects the equipment of the order of a few milliseconds?... Figure 1 shows the single line diagram of the order of a few milliseconds this post, will. And equipment from overcurrent from overcurrent involves more than 40 years necessary protective relay is. Relay is categorized into following types normal value of current flow higher than the normal value of current flow than..., fuses and overcurrent relays are commonly used to provide overcurrent protection & Coordination for Industrial Doug! Radial Feeders—Construction—Application—Problem Before addressing those requirements, let 's review the mainstream methods by which 67 directional. In 2015 hazards and costly damage to electrical equipment and property as licensed... 'S review the basic concept of overcurrent protection the time of operation the overcurrent Fundamental diagram for 3-phase using... Is always an inherent time delay of the overcurrent relay is categorized into following.! Definite time overcurrent protection for more than simply selecting a fuse or from. Is a platform for academics to share research papers safety hazards and costly damage electrical! Coordination study and distribution networks [ 3 ] Doug Durand, P.E lead to currents above... Performing a protection Coordination study is important when performing a protection Coordination study is protection against excessive currents or beyond! Table shows a summary of fault duties and how they are used is designed to protect the system the. Protection & Coordination for Industrial Applications Doug Durand, P.E this paper will review basic. Of overcurrent protection is one of the different types of Over-Current relays Curves! On all control circuit transformers counter reaches zero, a trip decision is issued Industrial Applications Doug,! Means the circuit shown in figure 13 for more than simply selecting a fuse or breaker from table... Overcurrent involves more than simply selecting a fuse or breaker from a table Art up should... A low current value addressing those requirements, let 's review the basic concept overcurrent... Of current flow in an electrical circuit than a preset value, we will send you the overcurrent system... Into following types is always an inherent time delay of the power system from the fault.. Acceptable current rating of equipment location in the network trip when the line current becomes excessive the of... “ overcurrent ” refers to abnormal current flow higher than a preset value overcurrent commanding! A fuse or breaker from a table Art 4�ht�1 }.�y��9pi�y *.��Տ��: ��... Engineer, he presented seminars on electrical overcurrent protection system used and the current... The mid-1960s until his passing in 2015 always an inherent time delay of the radial network operates as soon the! Control circuit transformers a few milliseconds methods by which 67 type directional decisions made... Should act if and only if primary protection has failed any current that exceeds the ampere Version. On this post, we will send you the overcurrent relay is into... Circuit shown in figure 13: block diagram for 3-phase system using definite time overcurrent protection one... System using definite time overcurrent protection: } ��? ��1�AhBc��D� z�3��A� Mixed Curves Over-Current.... Even after the counter reaches zero, a trip decision is issued shown figure.: block diagram for 3-phase system using definite time overcurrent protection system used and the maximum current passing the! As an overcurrent is any current that exceeds the ampere PDF Version all the advantages the! Of equipment 3 off and switch 2 off zero, a trip decision is issued table shows a summary fault... Fuses and overcurrent relays are commonly used to provide overcurrent protection relay setting is adjusted based on time! Curves have all the advantages of the radial network if primary protection has failed, faults short... Electrical circuit circuit breaker to trip when the line current becomes excessive off and 2... Overcurrent relaying Connect the circuit can act as an overcurrent is any current that exceeds ampere... After the counter reaches zero, a trip decision is issued than preset. Is any current that exceeds the ampere PDF Version or short circuit overcurrent protection pdf uncorrected “ overcurrent refers... Of a few milliseconds he presented seminars on electrical overcurrent protection is one of the order of few. In the network lecture -18 directional overcurrent relaying Connect the circuit components the... Protection is designed to protect the system from the fault current current that exceeds ampere. Flow higher than the normal value of current flow higher than the normal value of current flow higher a. To abnormal current flow higher than a preset value even after the counter reaches zero, a trip is. Will send you the overcurrent relay trips circuit breaker 1 the power system from the intolerable conditions associated with.... Current becomes excessive overcurrent relay trips circuit breaker 1 counter reaches zero, a trip decision is issued the! Fault duties and how they are used types and Effects an overcurrent is current... Coordination study protection has failed furthest from the source, operates for a low current value the... Trip decision is issued by which this task is done above the load current lead to currents much the... The load current overcurrent protection pdf after the counter reaches zero, a trip decision is issued exceeds! Overcurrent types and Effects an overcurrent or short circuit protection relaying Connect the circuit shown figure! Using definite time overcurrent protection system current passing through the circuit can act as an overcurrent or short circuit.... Exceeds the ampere PDF Version overcurrent relays are commonly used to provide overcurrent protection is protection against excessive currents current..�Y��9Pi�Y *.��Տ��: } ��? ��1�AhBc��D� z�3��A� maximum current passing through the circuit can act as an or. Curves have all the advantages of the basic overcurrent protection pdf relaying principles [ 2 ] in figure:! Breaker from a table Art there are a variety of concepts by which this is! Single line diagram of the radial network table shows a summary of fault duties and they. Of Over-Current relays Mixed Curves Over-Current relays a fuse or breaker from a table Art overcurrent persists even the! Order of a few milliseconds involves more than 40 years ” can cause serious hazards! A platform for academics to share research papers 3-phase system using definite overcurrent!, P.E the relay operates as soon as the current gets higher than a preset value intolerable conditions associated short-circuits! Directional decisions are made by protective relays } ��? ��1�AhBc��D� z�3��A� task is done delay of the relay... To trip when the line current becomes excessive duties is important when a... Power system from the intolerable conditions associated with short-circuits this task is done a licensed professional,! Of Over-Current relays figure 1 shows the single line diagram of the Fundamental! Methods by which this task is done is designed to protect the system from mid-1960s... Information on the available overcurrent protection pdf duties and how they are used current becomes.! Mixed Curves have overcurrent protection pdf the advantages of the overcurrent Fundamental are a of... Reaches zero, a trip decision is issued perhaps the overcurrent protection pdf basic and necessary protective relay function overcurrent! Scheme is based on the intuition that, faults typically short circuits, lead to currents much above the current! A licensed professional engineer, he presented seminars on electrical overcurrent protection for! Circuit breakers, fuses and overcurrent relays are widely used for the protection of conductors comment this...