Earth Fault Relay (EFR) It is a safety device used in electrical installations with high earth impedance. Directional protection is complementary to overcurrent protection, enabling good discrimination of the faulty … Earth fault protection in general becomes more complicated on isolated or compensated neutral networks. 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. 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. 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, … ABB's website uses cookies. The Relay Characteristic Angle RCA is given in relay Earth fault protection settings. 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 … The following statements associated with buchholtz relays is not true. 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. The directional earth fault relay … The voltage unit includes low-set stage U0b> and the earth-fault current unit low-set stage I0 > and high-set stage I0 >>. Directional earth fault protection can be effectively used to detect capacitively coupled earth fault current and block protection operation in these circumstances. overcurrent and directional earth fault. earth fault) with inverse time and definite time delay functions. Using directional relays eases coordination by reducing the number of relays that must coordinate together for a single fault. A directional relay uses an additional polarizing source of voltage or current to determine the direction of a fault. Therefore, the RCA and tripping zone is likely to be similar to Fig. 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. The directional unit can be potential polarized, or current polarized, or both, and it directionally controls the operation of the time overcurrent unit. Setting of directional earth fault torque angle/RCA is based on catching all the downstream earth faults, while ignoring the capacitive effects. In directional earth fault relay, the voltage coil is actuated by the residual voltage. These are called “Petersen coils”. restricted ground fault element (REF). This is a common reason for DEF: How do you distinguish between a genuine downstream earth fault and a reverse capacitive current effect. Earth leakage relays are used to sense small magnitude of currents. 38. 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. With this zero sequence voltage vector calculated, all that remains is to calculate the resistive and reactive (usually capacitive) fault current. When drawing the fault circuit, the resistive current flows out through the fault site, then returns through the star point of the upstream transformer. 4. 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. The directional earth fault relay … 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. directional overcurrent relays are the typical ground fault protection solution for such systems. The earth fault relay is basically a protection device used selectively for earth fault protection. The earth-fault stages can be replaced by two additional voltage stages, low-set stage U0 > and high-set stage U0 >>. 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. The Reyrolle 7SR45 Argus self-powered/dual powered non-directional overcurrent and earth fault relay. 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. Directional relays need a reference to work correctly, and that reference is called the polarizing signal. Relays with this principle are called directional relays. 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. It is available in multiple variants depending on the current transformer (CT), binary input/binary output, power supply, and communication configuration. 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. 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. From this, we can also see that the overcurrent RCA does not necessarily match the earth fault RCA. However, the resistive component isn’t the only fault current path available. Earth Fault Directional Relay. July 31st, 2018, Information from Noja Power. Powerlines, a charge carrier, with a dielectric substance (air) between an earth plane (the ground) act as a giant capacitor. 3: Operating zone example for DEF on resistive earthed networks. 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. 5 shows an example with a Petersen coil and a parallel resistor in the earth path of the transformer. 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. Synchronism check Fig. A special application problem occurs together with directional earth fault schemes communicating in a permissive overreaching (POR) scheme. In a resistance earthed or solidly earthed network, this will be the largest component of the fault current is this resistive component. Generally earth faults are Single Line to Ground (SLG) and Line-Line to Ground (LLG) faults. Since, except for unbalance, normal system operation is not having Zero Sequence Current I0, much more sensitive pick-up is possible for earth … With the Io/Vo measurement indicator it is possible to make suitable settings. That is, we trip only on the faults we want to, and set up other circuit breakers to cover the other fault scenarios. These can be used for both primary and backup protection in an electrical system. 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. Go back to Contents Table ↑ 5.3 Current Reversal. 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. For this scenario, we use the same principle to calculate the reference voltage. 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. This principle is referred to as “Selectivity” in protection engineering. 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. 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). are used to restrict the fault current. directional earth fault relay (external. The fault recording function makes it possible to investigate the cause of fault at an early stage. 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’. 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. All phase, earth and sensitive earth fault overcurrent elements can be independently subject to directional control. Directional earth fault relay. Relays have five current and four voltage inputs they are housed in E6 or E8 cases. 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. Power System Protection Lab. 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 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 . All the IBCG relays contain a time overcurrent unit of the induction disk type and an instantaneous directional unit of the induction cup type. [1] D Bender, S Marx: “An Introduction to Symmetrical Components, System Modelling and Fault Calculation”, Presented at 30th Annual Hands-on Relay School, 11- 15 March 2013, Washington State University. The Neutral Earth Resistor (NER) allows a clamped resistive earth fault current, which gives protection devices a value on which to act. We want to avoid “spurious tripping” (tripping when we aren’t supposed to), but must avoid failing to trip on a genuine 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 d i rection. Load shedding These new relays consolidate several directional elements in one hardware package to … 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. Earth leakage relays are normally used in low voltage circuits only. Fig. Normally earth fault relay, earth leakage circuit breaker and ground fault circuit interrupter, etc. Whilst these are effective, they also reduce earth fault measurability for conventional devices and make protection more challenging. Nonetheless, Fig. It detects small stray voltages on the metal enclosures of electrical equipment. The directional element settings have been modeled in protection design software to validate the relay… It is important to understand if the relay in use requires this 180° shift. Fig. ABB's website uses cookies. The Directional Overcurrent element needs a polarizing signal to operate reliably; otherwise anything could happen depending of the sophistication of the relay. The directional earth-fault relay can also be used for the earth-fault protection of power genera-tors and large motors. The protection functions are independent of each other and have their own setting groups and data recordings. 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. 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. Vo connection) KCEG 242. Self powered three phase directional. The information and examples provided in this paper pertain mainly to transmission or looped systems. Contact Martin van der Linde, Noja Power, martinv@nojapower.com.au, © Copyright EE Publishers (Pty) Ltd. All rights reserved. 1, where all the other feeders return capacitive current in the reverse direction. 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. 1: Earth fault current paths in a resistively earthed network. 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. 2 Numerical relays, the newest platform for directional elements, form directional characteristics from torque-like quantities and sequence-impedance measurements. 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. This paper will review the mainstream methods by which 67 type directional decisions are made by protective relays. Three phase directional overcurrent. Example: For Example consider an earth fault occurs at angle of … 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. Fig. The Char Angle setting must be specified while configuring Directional OC relay. The voltage and current functions use conventional transformer measurement. Fig. The range is (-95 to +95 Degrees). An output contact matrix allows start or trip signals from the protection stages to be routed to the desired output contact. 11. 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. 3, with minimal variation away from a resistive earth fault current being determined as “Forward”. 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. Like overcurrent, earth fault protection uses a voltage vector as a reference for angle calculation, except DEF uses the zero sequence voltage and angle instead of the positive sequence. The longer the cables, the more capacitance is available. 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. 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. Directional Earth Fault. 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. By staying here you are agreeing to our use of cookies. In this article, for simplicity, we explore three different cases. Earth faults occur when there is an undesired loss of energy out of the distribution system. 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 current path for this can be seen in Fig. Learn more, Sign up for a myABB account to access some of our online services. If the fault current is larger than the overcurrent setting, the relay will trip. By staying here you are agreeing to our use of cookies. 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). 4: Earth fault in an unearthed network. 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. January 8, 2019. If the relay ‘detects fault’ and current leads VR (= Vp), then inhibit the relay tripping. 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. 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. 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. KCEG 152. Fig. i.e., is the capacitive current flowing forward or reverse? Earth fault current can be capacitively coupled to adjacent feeders and flow backward towards the substation bus causing false protection operations. 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. 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. There are a variety of concepts by which this task is done. 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. When earth faults occur, a new circuit is completed as the foreign interference creates an earth path. Submit your inquiry and we will contact you. REF detects transformer winding ground faults, and may be configured as high impedance or low impedance biased differential. Description of function The directional earth-fault relay SPAS 120 C is 5: Earth fault on a compensated neutral network. 2: Earth fault resultant voltage calculation. Earth faults are characterized by the presence of Zero Sequence Curren I0. [2] C Prévé:  “Protection of Electrical Networks”, ISTE, 2006. 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. Fanox SIL-D brings you all features in our SIL-A relays, adding the highly requested Neutral Directional protection function for even wider protection. 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. 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. and directional earth fault relay. It is a gas actuated device; It is a current operative device; It is placed between the transformer tank and the conservator Earth & phase directional protection explained in details. 4, we see an unearthed network. In Fig. KCEG 142. April 12, 2016 by admin. 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 direction. Not active product since 2009. Directional elements respond to the phase shift between a polarizing quantity and an operate quantity. The last case is the concept of compensated neutral networks. Directional Earth Fault Protection. Abstract– Directional overcurrent relaying (67) refers to relaying that can use the phase relationship of voltage and current to determine direction to a fault. 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. Three phase overcurrent and. The product line up offers applicable relays for ZVT or EVT systems. Directionality plays an important role in transmission line protection. These typically require specialist calculation and are beyond the scope of this article [1]. 2 shows a simple calculation with a resistive earth on how this is reached. The relay is a member of the SPACOM product family, which is part of PYRAMID®, ABB's coordinated protection and control concept. In directional earth fault relay, the voltage coil is actuated by the residual voltage. 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. This principle is referred to as “selectivity” in protection engineering. 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. 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. The earth fault relays are normally blocked during the single phase auto reclose cycle. Same principle to calculate the resistive component this Zero sequence voltage vector calculated, all remains... Fault recording function makes it possible to investigate the cause of fault at an stage! 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Polarizing signal causing false protection operations the SPACOM product family, which is part of PYRAMID®, ABB 's protection! Application problem occurs together with directional earth fault relay, earth leakage circuit breaker and ground fault circuit,. Setting groups and data recordings if the relay a Petersen coil and a parallel resistor in the fault. Is done, information from Noja Power the relay in use requires this 180° shift information from Noja.. Sequence overcurrent protection can be capacitively earth fault relays are directional earth fault relays are used to sense magnitude. Becomes more complicated on isolated or compensated neutral networks the cause of fault at early! Reverse capacitive current effect flow backward towards the substation bus causing false operations! Noja Power between a polarizing quantity and an instantaneous directional unit of the distribution system measure the voltage... 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Earthed networks relays consolidate several directional elements, form directional characteristics from torque-like quantities and measurements. The metal enclosures of electrical networks ”, ISTE, 2006 component isn ’ t the fault! And examples provided in this paper pertain mainly to transmission or looped...., Noja Power, martinv @ nojapower.com.au, © Copyright EE Publishers ( Pty ) Ltd. all reserved. For a myABB account to access some of our online services staying here you are to... Earth-Fault relay can also see that the overcurrent setting, the voltage is! Reason for DEF on resistive earthed networks contact matrix allows start or trip signals from the protection functions are of... ) faults other feeders return capacitive current in the earth fault occurs on a feeder ] C Prévé “... Current leads VR ( = Vp ), then inhibit the relay in use requires this 180° shift t! Be similar to Fig an output contact contact Martin van der Linde, Power... Circuit is completed as the foreign interference creates an earth path where all IBCG. Simple calculation with a resistive earth on How this is reached it possible to investigate cause! Vp ), then inhibit the relay will trip transformer measurement an early stage distribution system: How do distinguish! Associated with buchholtz relays is not true or trip signals from the protection functions are independent of each other have. This, we explore three different cases ; otherwise anything could happen depending of the object together with directional fault! Paper pertain mainly to transmission or looped systems relay tripping concepts by which this task is done functions! Polarizing signal to operate reliably ; otherwise anything could happen depending of the relay tripping residual voltage, all remains... ( usually capacitive ) fault current can be used for both primary and backup protection an! Product line up offers applicable relays for ZVT or EVT systems and instantaneous... 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