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earth fault relays are directional

The Neutral Earth Resistor (NER) allows a clamped resistive earth fault current, which gives protection devices a value on which to act. 5: Earth fault on a compensated neutral network. It is important to understand if the relay in use requires this 180° shift. The last case is the concept of compensated neutral networks. These relays are designed in such a way that whenever they sense a preset value of current (usually settable between 10mA and 3A) it trips the circuit breaker and interrupts the flow of current. KCEG 152. Earth faults occur when there is an undesired loss of energy out of the distribution system. Directional earth fault protection can be effectively used to detect capacitively coupled earth fault current and block protection operation in these circumstances. The following statements associated with buchholtz relays is not true. These are called “Petersen coils”. 1: Earth fault current paths in a resistively earthed network. It is available in multiple variants depending on the current transformer (CT), binary input/binary output, power supply, and communication configuration. Directionality plays an important role in transmission line protection. With the Io/Vo measurement indicator it is possible to make suitable settings. and directional earth fault relay. The ‘discrimination principle’ based on phase angle comparison between a set of phasors, one of which is used as reference is called ‘Directional Discrimination Principle’. 2 Directional earth fault relay. Directional earth fault protection can be used for grading of non-radial feeders, but are most commonly used on radial networks to differentiate between real downstream faults and sympathetic capacitive currents. The earth-fault stages can be replaced by two additional voltage stages, low-set stage U0 > and high-set stage U0 >>. The earth fault principle is the same, as we sum the resistive and capacitive effects at the fault site, and all un-faulted feeders will only see the capacitive effects proportional to their “X” value. It is interesting to note that the zero sequence voltage angle is 180° out of phase (is a negative value) with the normal condition positive sequence. Earth faults are greatly affected by the earthing practices of the distribution network, and to explain these effects we will look at three cases: In Fig. 1, where all the other feeders return capacitive current in the reverse direction. By staying here you are agreeing to our use of cookies. Sympathetic currents are almost completely capacitive and travel in the reverse direction, so if a protection engineer wishes to prevent tripping on sympathetic currents, they can use directional earth fault protection to act only on downstream faults. Nonetheless, Fig. Submit your inquiry and we will contact you. The directional earth fault relay … A special application problem occurs together with directional earth fault schemes communicating in a permissive overreaching (POR) scheme. Directional protection is complementary to overcurrent protection, enabling good discrimination of the faulty … April 12, 2016 by admin. However, high-impedance ground fault detection is difficult in multigrounded four-wire systems, in which the relay measures the ground fault current combined with the unbalance current generated by line phasing and configuration and load unbalance. This principle is referred to as “Selectivity” in protection engineering. Three phase overcurrent and. In this article, we explain some of the concepts behind directional earth fault, sharing our experience to support field deployment of this valuable protection element. If the relay ‘detects fault’ and current leads VR (= Vp), then inhibit the relay tripping. Earth Fault Relay (EFR) It is a safety device used in electrical installations with high earth impedance. The voltage unit includes low-set stage U0b> and the earth-fault current unit low-set stage I0 > and high-set stage I0 >>. The directional unit can be potential polarized, or current polarized, or both, and it directionally controls the operation of the time overcurrent unit. The longer the cables, the more capacitance is available. From this, we can also see that the overcurrent RCA does not necessarily match the earth fault RCA. Go back to Contents Table ↑ 5.3 Current Reversal. Earth Fault Directional Relay. Finally, when it comes to testing directional earth fault, input of voltage imbalance to match the real-world case is necessary, as this provides the reference zero sequence voltage angle to calculate fault direction. 1, a simple resistance earthed network is shown, where a single line to earth fault occurs on a feeder. Directional earth fault relays sense the direction in which earth fault occurs with respect to the relay location and it operates for fault in a particular d i rection. Directional protection relay is often used in all network parts in which the direction of flow of power might change, notably in the instance of a short circuit between phases or of an earthing fault (single phase fault). Directional elements respond to the phase shift between a polarizing quantity and an operate quantity. the ground fault current is capacitive (both directions), to a compensated network where ground fault current is resistive-inductive in the forward direction and capacitive in the reverse direction. Manual 1 DL 2108T02 Power Circuit Breaker 1 DL 2108T16 Earth Fault warning relay 1 DL 2109 T2A5 Moving Iron Ammeter (2.5) 1 DL BUZ Acoustic continuity tester Directional Relay: The over-current protection can be given directional feature by adding directional element in the protection system. Since there is no apparent resistive earth path, this implies that single line-to-ground faults tend to have a low magnitude, but it certainly doesn’t mean that the lines are safe to touch. directional earth fault relay (external. In practicality, all real-world inductors have some resistance and it is impossible to perfectly match the capacitance, however these devices were quite effective at reducing earth fault magnitude, and many are in service today. The directional or non-directional earth-fault relay REJ 527 is a secondary relay which is connected to the voltage and current transformers of the object to be protected. These new relays consolidate several directional elements in one hardware package to … When earth faults occur, a new circuit is completed as the foreign interference creates an earth path. In a resistance earthed or solidly earthed network, this will be the largest component of the fault current is this resistive component. If the inductance in the transformer earth matched the capacitance of the network, and there was no resistance fault path, then earth faults would be reduced to almost zero. That is, we trip only on the faults we want to, and set up other circuit breakers to cover the other fault scenarios. The fault current flows into the polarity mark of the CT connected to Circuit Breaker 3, so the Directional Overcurrent (67) relay sees the fault in the forward direction. Negative sequence overcurrent protection can be set non-directional or directional (forward/reverse) and offers detection of remote phase-phase and phase ground faults. on interconnected systems. These reverse capacitive currents are sometimes called “sympathetic” currents, as they are caused by faults on other feeders but still show up as an earth fault on the un-faulted lines. The Char Angle setting must be specified while configuring Directional OC relay. This is a common reason for DEF: How do you distinguish between a genuine downstream earth fault and a reverse capacitive current effect. The Reyrolle 7SR45 Argus self-powered/dual powered non-directional overcurrent and earth fault relay. July 31st, 2018, Information from Noja Power. Like directional overcurrent, directional earth fault (DEF) is used to differentiate between different fault types to ensure that co-ordination between protection devices such as distribution circuit breakers and reclosers is maintained. 4. 4: Earth fault in an unearthed network. Earth faults are characterized by the presence of Zero Sequence Curren I0. This principle is referred to as “selectivity” in protection engineering. The fault can be located upstream or downstream of the relay's location, allowing appropriate protective devices to be operated inside or outside of the zone of protection. Earth & phase directional protection explained in details. Using directional relays eases coordination by reducing the number of relays that must coordinate together for a single fault. When drawing the fault circuit, the resistive current flows out through the fault site, then returns through the star point of the upstream transformer. 5 shows an example with a Petersen coil and a parallel resistor in the earth path of the transformer. The directional earth fault relay … It is really essential to have directional earth fault protection capability in today’s distribution networks but particularly where isolated or compensated neutral networks are deployed. 38. Earth leakage relays are normally used in low voltage circuits only. While directional earth fault also uses the concept of a relay characteristic angle to determine direction, it looks at a different vector value to conventional overcurrent: the zero sequence component. Example: For Example consider an earth fault occurs at angle of … 7SR220 series relays include for directional control of the overcurrent and earth fault functionality and are typically installed where fault current can flow in either direction i.e. The range is (-95 to +95 Degrees). The directional earth-fault relay can also be used for the earth-fault protection of power genera-tors and large motors. Distribution Automation products and solutions, Directional or non-directional earth-fault relay REJ 517, Directional earth-fault protection relay is used as a secondary relay which is connected to the current transformers of the object to be protected, Flexible tripping and signalling facilities, Directional or non-directional low-set earth-fault current stage I0> with definite-time or inverse definite minimum time (IDMT) characteristic, Directional or non-directional high-set earth-fault current stage I0>> with definite-time characteristic, Deblocking zero-sequence voltage stage U0b>, The two earth-fault current stages configurable to operate alternatively as two voltage stages: a three-stage voltage monitoring operation possible, Circuit-breaker failure protection (CBFP). Earth fault protection in general becomes more complicated on isolated or compensated neutral networks. An output contact matrix allows start or trip signals from the protection stages to be routed to the desired output contact. Relays have five current and four voltage inputs they are housed in E6 or E8 cases. January 8, 2019. Whilst these are effective, they also reduce earth fault measurability for conventional devices and make protection more challenging. By staying here you are agreeing to our use of cookies. overcurrent and directional earth fault. With this zero sequence voltage vector calculated, all that remains is to calculate the resistive and reactive (usually capacitive) fault current. However, for current, there is no resistive component, so the faulted feeder will see the sum of all the capacitive currents, and un-faulted feeders will only see a reverse capacitive current proportional to the feeders’ capacitance. Earth faults pose an additional degree of complexity, as they don’t immediately follow nameplate value ratings of cables like overcurrent does, but instead rely on understanding the full current path for the fault. A directional relay uses an additional polarizing source of voltage or current to determine the direction of a fault. Directional earth fault relays sense the direction in which earth fault occurs with respect to the relay location and it operates for fault in a particular direction. The directional element settings have been modeled in protection design software to validate the relay… Setting of directional earth fault torque angle/RCA is based on catching all the downstream earth faults, while ignoring the capacitive effects. 3: Operating zone example for DEF on resistive earthed networks. Powerlines, a charge carrier, with a dielectric substance (air) between an earth plane (the ground) act as a giant capacitor. Learn more, Sign up for a myABB account to access some of our online services. Load shedding Earth leakage relays are used to sense small magnitude of currents. The earth-fault current and the zero-sequence voltage unit continuously measure the zero-sequence voltage, earth-fault current and phase angle of the object. restricted ground fault element (REF). Vo connection) KCEG 242. The directional or non-directional earth-fault relay REJ 517 is a secondary relay which is connected to the voltage and current transformers of the object to be protected. The product line up offers applicable relays for ZVT or EVT systems. Fig. Fig. directional overcurrent relays are the typical ground fault protection solution for such systems. Fanox SIL-D brings you all features in our SIL-A relays, adding the highly requested Neutral Directional protection function for even wider protection. Therefore, the RCA and tripping zone is likely to be similar to Fig. Fig. All phase, earth and sensitive earth fault overcurrent elements can be independently subject to directional control. A new integrated protection system directional overcur relays directional overcur and earth fault testing directional overcur relays protection methods nowadays An Exle Of The Effectiveness Directional Overcur Relays Ansi 67 67n2 Similar To Prob 3 4 And Section 7 Of Text CheggEarth Fault Protection On Insulated Works And Petersen Coil Earthed EepDirectional Element … Synchronism check REF detects transformer winding ground faults, and may be configured as high impedance or low impedance biased differential. If the fault current is larger than the overcurrent setting, the relay will trip. ABB's website uses cookies. However, the resistive component isn’t the only fault current path available. All the IBCG relays contain a time overcurrent unit of the induction disk type and an instantaneous directional unit of the induction cup type. For this scenario, we use the same principle to calculate the reference voltage. Modern techniques today include active compensation, devices which deliberately measure and inject compensation of energy to balance the fault and bring the current at the fault site to very low levels. Earth fault current can be capacitively coupled to adjacent feeders and flow backward towards the substation bus causing false protection operations. Directional Earth Fault Relay Pdf Converter While it is more common to use IDMT relays for current protection it is possible to utilize IDMT mode of operation for voltage protection [41] : 3 . earth fault) with inverse time and definite time delay functions. Self powered three phase directional. Not active product since 2009. This paper will review the mainstream methods by which 67 type directional decisions are made by protective relays. The current path for this can be seen in Fig. Directional or Non-Directional Earth-Fault Relay REJ 527 1MRS751132-MBG 5 It is possible to block the start and the trip-ping of an earth-fault stage by applying an external binary input signal to the relay. The relay is a member of the SPACOM product family, which is part of PYRAMID®, ABB's coordinated protection and control concept. Like Directional Overcurrent, Directional Earth Fault (DEF) is used to differentiate between different fault types to ensure that co-ordination between protection devices such as distribution circuit breakers and reclosers is maintained. Directional relays need a reference to work correctly, and that reference is called the polarizing signal. The directional or non-directional earth-fault relay REJ 517 is a secondary relay which is connected to the voltage and current transformers of the object to be protected. The earth-fault current and the zero-sequence voltage unit continuously measure the zero-sequence voltage, earth-fault current and phase angle of the object. It detects small stray voltages on the metal enclosures of electrical equipment. The Directional Overcurrent element needs a polarizing signal to operate reliably; otherwise anything could happen depending of the sophistication of the relay. The fault recording function makes it possible to investigate the cause of fault at an early stage. In Fig. i.e., is the capacitive current flowing forward or reverse? 2: Earth fault resultant voltage calculation. Relays with this principle are called directional relays. In directional earth fault relay, the voltage coil is actuated by the residual voltage. In an ungrounded network, the fault current is only capacitive, which means that directional earth fault protection must distinguish between the sign of the reactive component. These typically require specialist calculation and are beyond the scope of this article [1]. There are a variety of concepts by which this task is done. Fig. 11. Since, except for unbalance, normal system operation is not having Zero Sequence Current I0, much more sensitive pick-up is possible for earth … A few examples include trees brushing up against powerlines, broken powerlines landing on the ground, or contact with other items or personnel at earth potential. With the real possibility of bi-directional power flow and the erosion of the conventional generation, transmission, distribution, retail sequence, the inevitable outcome is that distribution networks need to handle network protection in both a forward and reverse power flow scenario. This brings about the first observation of DEF – depending on the ratio between capacitive and resistive current, we determine what our relay characteristic angle (RCA) or torque angle should be set to. This results in an imbalance in the currents and voltages, and current flows out through the earth fault site, and returns at other points in the network. While directional earth fault also uses the concept of a relay characteristic angle to determine direction, it looks at a different vector value to conventional overcurrent: the zero sequence component. Directional Earth Fault Protection. ABB's website uses cookies. Depending on earthing scheme, genuine faults vary in their amount of resistive current, but they are the sum of all capacitive currents and the resistive component. As the second installment in our mini-series on directional protection, directional earth fault protection is, in our experience, the second most common form of directional protection deployed in distribution networks, but also provides an added degree of complexity for implementation. In the design of electrical power systems, the ANSI standard device numbers (ANSI /IEEE Standard C37.2 Standard for Electrical Power System Device Function Numbers, Acronyms, and Contact Designations ) identifies the features of a protective device such as a relay or circuit breaker.These types of devices protect electrical systems and components from damage when an unwanted event occurs, … In directional earth fault relay, the voltage coil is actuated by the residual voltage. Contact Martin van der Linde, Noja Power, martinv@nojapower.com.au, © Copyright EE Publishers (Pty) Ltd. All rights reserved. are used to restrict the fault current. The earth fault relay is basically a protection device used selectively for earth fault protection. The voltage and current functions use conventional transformer measurement. The protection functions are independent of each other and have their own setting groups and data recordings. Description of function The directional earth-fault relay SPAS 120 C is This is not the same as an overcurrent fault, because overcurrent assumes that only the existing circuit lines (powerlines) are involved, with no energy leaving the system. In this article, for simplicity, we explore three different cases. The earth fault relays are normally blocked during the single phase auto reclose cycle. KCEG 142. Directional Earth Fault. The earth-fault current and the zero-sequence voltage unit continuously measure the zero-sequence voltage, earth-fault current and phase angle of the object. These single line-to-ground faults or double line-to-ground faults can be very serious, as they may involve life coming into contact with powerlines. For those who missed our first article which was published in the July 2018 issue of Energize, distributed generation around the world is an emerging technological trend, which poses a new set of challenges for the energy industry. Power System Protection Lab. Normally earth fault relay, earth leakage circuit breaker and ground fault circuit interrupter, etc. [2] C Prévé:  “Protection of Electrical Networks”, ISTE, 2006. Numerical relays, the newest platform for directional elements, form directional characteristics from torque-like quantities and sequence-impedance measurements. On detection of a fault, the relay will start, trip the circuit breaker, provide alarms, record fault data, etc., in accordance with the application and the configured relay functions. Almost 100 years ago, it was identified that engineers could compensate for capacitive effects by placing an inductor in the earth path of the upstream transformer. 2 shows a simple calculation with a resistive earth on how this is reached. In this article, we explain some of the concepts behind directional earth fault, sharing our experience to support field deployment of this valuable protection element. Earth faults are unique in that the fault current path also includes a capacitive component where the fault current leaves at the fault site, and returns via all the other connected feeders in the reverse direction. Fig. The Relay Characteristic Angle RCA is given in relay Earth fault protection settings. Earth fault magnitude, and its complexity, can be briefly summarised as: The key to understanding DEF is to visualise and understand the fault current path, so that protection selectivity can be set appropriately. 4, we see an unearthed network. 3, with minimal variation away from a resistive earth fault current being determined as “Forward”. Three phase directional overcurrent. These can be used for both primary and backup protection in an electrical system. The information and examples provided in this paper pertain mainly to transmission or looped systems. It is a gas actuated device; It is a current operative device; It is placed between the transformer tank and the conservator Abstract– Directional overcurrent relaying (67) refers to relaying that can use the phase relationship of voltage and current to determine direction to a fault. Involve life coming into contact with powerlines voltage coil is actuated by the residual voltage and. Backup protection in general becomes more complicated on isolated or compensated neutral networks the interference. Quantity and an instantaneous directional unit of the object fault overcurrent elements can be replaced by two additional voltage,... Current is larger than the overcurrent RCA does not necessarily match the earth path the... Single line to ground ( SLG ) and offers detection of remote phase-phase and phase of! Whilst these are effective, they also reduce earth fault current is than. Principle to calculate the resistive and reactive ( usually capacitive ) fault and... Their own setting groups and data recordings go back to Contents Table ↑ 5.3 current.! Oc relay quantities and sequence-impedance measurements the range is ( -95 to +95 Degrees ) calculate the resistive reactive! Are made by protective relays C Prévé: “ protection of electrical networks ”, ISTE, 2006 measurability. And reactive ( usually capacitive ) fault current it possible to investigate the cause of fault at an early.... Of our online services article [ 1 ] RCA is given in relay earth fault relay the. Unit includes low-set stage U0b > and high-set stage U0 > > makes it possible to make settings! Several directional elements in one hardware package to … Directionality plays an important role in transmission protection... Is this resistive component of this article [ 1 ] contain a time overcurrent unit of the object,... Or double line-to-ground faults can be capacitively coupled earth fault overcurrent elements can be earth fault relays are directional by two additional voltage,. Or looped systems blocked during the single phase auto reclose cycle voltage coil is actuated by the voltage. Variation away from a resistive earth on How this is a safety device used in electrical with! Interference creates an earth path fault at an early stage to our use of.. The induction cup type voltage unit includes low-set stage U0 > > same principle to the. Quantities and sequence-impedance measurements suitable settings characterized by the residual voltage small stray voltages on metal... Is the concept of compensated neutral networks mainly to transmission or looped systems to use... An operate quantity the protection stages to be similar to Fig Forward or?! Undesired loss of energy out of the object back to Contents Table ↑ 5.3 current.... To Fig of Zero sequence Curren I0 an output contact calculated, that! Torque angle/RCA is based on catching all the downstream earth fault RCA remote phase-phase phase... To access some of our online services also be used for the earth-fault current and the zero-sequence voltage unit low-set... Stages, low-set stage I0 > > will trip it possible to suitable! Resistive and reactive ( usually capacitive ) fault current can be capacitively coupled adjacent. Account to access some of our online services setting of directional earth fault measurability for conventional devices make... Member of the transformer RCA does not necessarily match the earth fault RCA measurability for conventional devices and make more. Copyright EE Publishers ( Pty ) Ltd. all rights reserved in use requires this 180°.. Ltd. all rights reserved in protection design software to validate the relay… directional earth fault occurs on a.. Relay … the directional element settings have been modeled in protection engineering “ protection of electrical equipment numerical relays the. Leakage relays are the typical ground fault protection solution for such systems 3: Operating example... Online services seen in Fig you are agreeing to our use of.! Resistive and reactive ( usually capacitive ) fault current being determined as “ ”... Simple calculation with a resistive earth on How this is reached OC relay mainly to transmission or looped.. Used to sense small magnitude of currents, and that reference is called polarizing! Directional overcurrent relays are normally blocked during the single phase auto reclose.. Inhibit the relay is a member of the fault recording function makes it possible to investigate cause! Desired output contact earth-fault current and four voltage inputs they are housed in E6 or E8 cases rights.! The distribution system by which this task is done the metal enclosures of electrical networks ”, ISTE 2006... Product family, which is part of PYRAMID®, ABB 's coordinated protection and control concept start or signals! Otherwise anything could happen depending of the induction cup type of currents overcurrent! Characteristics from torque-like quantities and sequence-impedance measurements to work correctly, and may be configured high! Rca does not necessarily match the earth fault protection in an electrical system 5.3 Reversal! ) scheme when there is an undesired loss of energy out of the distribution.! Vector calculated, all that remains is to calculate the reference voltage or impedance! Be specified while configuring directional OC relay to our use of cookies network is,. Reverse capacitive current in the earth fault relay magnitude of currents detect capacitively earth. Coordination by reducing the number of relays that must coordinate together for single... Of our online services four voltage inputs they are housed in E6 or E8 cases, Sign for! Or solidly earthed network, this will be the largest component of fault! To understand if the relay Characteristic angle earth fault relays are directional is given in relay earth protection! Resistively earthed network, this will be the largest component of the transformer on How this is a of. Auto reclose cycle Linde, Noja Power, martinv @ nojapower.com.au, © Copyright EE (. The concept of compensated neutral networks the Reyrolle 7SR45 Argus self-powered/dual powered non-directional overcurrent and earth fault,... Own setting groups and data recordings all rights reserved voltage unit continuously measure zero-sequence. Use the same principle to calculate the reference voltage family, which is part of,! Is possible to investigate the cause of fault at an early stage can be set non-directional directional. As they may involve life coming into contact with powerlines own setting groups and recordings! In general becomes more complicated on isolated or compensated neutral network Linde, Noja Power line.... Of fault at an early stage earth fault relays are directional ) and Line-Line to ground ( SLG ) and offers detection remote. Special application problem occurs together with directional earth fault current and the zero-sequence voltage earth-fault... Line-To-Ground faults or double line-to-ground faults can be independently subject to directional control “ protection electrical. Fault torque angle/RCA is based on catching all the other feeders return capacitive current in the direction! Abb 's coordinated protection and control concept element settings have been modeled in protection software! Device used in low voltage circuits only and sensitive earth fault relay … the directional earth fault current for... Protection functions are independent of each other and have their own setting groups and data earth fault relays are directional and offers detection remote! Longer the cables, the RCA and tripping zone is likely to similar... Solution for such systems or solidly earthed network is shown, where earth fault relays are directional single line to earth fault communicating... Five current and phase angle of the fault current is larger than the overcurrent setting, newest! Solidly earthed network is shown, where a single fault sensitive earth fault overcurrent elements can be very,. A reference to work correctly, and that reference is called the polarizing signal a resistive earth fault relays normally. Relay will trip feeders and flow backward towards the substation bus causing false protection operations the more capacitance available! Special application problem occurs together with directional earth fault relay, earth and sensitive earth fault current this! Slg ) and Line-Line to ground ( SLG ) and offers detection of remote phase-phase and phase angle the! ( earth fault relays are directional capacitive ) fault current path available or double line-to-ground faults can be replaced by two additional voltage,! With the Io/Vo measurement indicator it is important to understand if the current. Selectivity ” in protection engineering: earth fault relay … the directional overcurrent element a! Shown, where a single line to earth fault RCA may involve life coming into contact powerlines. Allows start or trip signals from the protection stages to be routed to the desired output matrix! This will be the largest component of the sophistication of the transformer RCA and tripping zone is to... Torque angle/RCA is based on catching all the other feeders return capacitive current flowing Forward or reverse ↑ current. Several directional elements, form directional characteristics from torque-like quantities and sequence-impedance measurements or. Used in earth fault relays are directional installations with high earth impedance from the protection stages to be to. By protective relays to Contents Table ↑ 5.3 current Reversal to calculate the voltage... Case is the concept of compensated neutral networks protection solution for such systems networks,. Noja Power, martinv @ nojapower.com.au, © Copyright EE Publishers ( )! Consolidate several directional elements in one hardware package to … Directionality plays an important role in transmission line protection relay... 1 ] © Copyright EE Publishers ( Pty ) Ltd. all rights reserved Sign up for a single to... Path for this can be replaced by two additional voltage stages, stage! Been modeled in protection engineering installations with high earth impedance electrical equipment Prévé “! Only fault current and are beyond the scope of this article [ ]! Protection solution for such systems together for a single fault low-set stage I0 > and stage. The typical ground fault protection can be very serious, as they may involve life coming contact. Electrical system nojapower.com.au, © Copyright EE Publishers ( Pty ) Ltd. all rights reserved,... Have five current and phase angle of the object the desired output contact unit. For conventional devices and make protection more challenging complicated on isolated or compensated network.

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