We want to avoid “spurious tripping” (tripping when we aren’t supposed to), but must avoid failing to trip on a genuine fault. There are a variety of concepts by which this task is done. Description of function The directional earth-fault relay SPAS 120 C is The directional element settings have been modeled in protection design software to validate the relay… 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. 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. 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, … The current path for this can be seen in Fig. If the relay ‘detects fault’ and current leads VR (= Vp), then inhibit the relay tripping. The fault recording function makes it possible to investigate the cause of fault at an early stage. April 12, 2016 by admin. The voltage and current functions use conventional transformer measurement. 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. 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. 1: Earth fault current paths in a resistively earthed network. This is a common reason for DEF: How do you distinguish between a genuine downstream earth fault and a reverse capacitive current effect. 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 … 2 shows a simple calculation with a resistive earth on how this is reached. Three phase directional overcurrent. 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. 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. 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. Fig. Earth fault protection in general becomes more complicated on isolated or compensated neutral networks. If the fault current is larger than the overcurrent setting, the relay will trip. 3, with minimal variation away from a resistive earth fault current being determined as “Forward”. 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. 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. and 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. 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. Negative sequence overcurrent protection can be set non-directional or directional (forward/reverse) and offers detection of remote phase-phase and phase ground faults. This principle is referred to as “Selectivity” in protection engineering. It is important to understand if the relay in use requires this 180° shift. 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’. 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 . The range is (-95 to +95 Degrees). This paper will review the mainstream methods by which 67 type directional decisions are made by protective relays. The Char Angle setting must be specified while configuring Directional OC relay. 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. 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. 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. Setting of directional earth fault torque angle/RCA is based on catching all the downstream earth faults, while ignoring the capacitive effects. 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. 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. Numerical relays, the newest platform for directional elements, form directional characteristics from torque-like quantities and sequence-impedance measurements. 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. 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. A directional relay uses an additional polarizing source of voltage or current to determine the direction of a fault. 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. Earth leakage relays are used to sense small magnitude of currents. 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. July 31st, 2018, Information from Noja Power. The relay is a member of the SPACOM product family, which is part of PYRAMID®, ABB's coordinated protection and control concept. 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. By staying here you are agreeing to our use of cookies. Powerlines, a charge carrier, with a dielectric substance (air) between an earth plane (the ground) act as a giant capacitor. 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. 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. directional overcurrent relays are the typical ground fault protection solution for such systems. 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). 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. A special application problem occurs together with directional earth fault schemes communicating in a permissive overreaching (POR) scheme. 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. All the IBCG relays contain a time overcurrent unit of the induction disk type and an instantaneous directional unit of the induction cup type. Directional relays need a reference to work correctly, and that reference is called the polarizing signal. It detects small stray voltages on the metal enclosures of electrical equipment. Three phase overcurrent and. Directional Earth Fault Protection. ABB's website uses cookies. Vo connection) KCEG 242. Earth faults are characterized by the presence of Zero Sequence Curren I0. 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 unit can be potential polarized, or current polarized, or both, and it directionally controls the operation of the time overcurrent unit. Earth Fault Directional Relay. Load shedding Directionality plays an important role in transmission line protection. 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. The product line up offers applicable relays for ZVT or EVT systems. 38. The earth fault relays are normally blocked during the single phase auto reclose cycle. 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 leakage relays are normally used in low voltage circuits only. 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. are used to restrict the fault current. 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. That is, we trip only on the faults we want to, and set up other circuit breakers to cover the other fault scenarios. It is a gas actuated device; It is a current operative device; It is placed between the transformer tank and the conservator Therefore, the RCA and tripping zone is likely to be similar to Fig. overcurrent and directional earth fault. 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. Contact Martin van der Linde, Noja Power, martinv@nojapower.com.au, © Copyright EE Publishers (Pty) Ltd. All rights reserved. Submit your inquiry and we will contact you. Fig. When drawing the fault circuit, the resistive current flows out through the fault site, then returns through the star point of the upstream transformer. The directional earth fault relay … January 8, 2019. Generally earth faults are Single Line to Ground (SLG) and Line-Line to Ground (LLG) faults. 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. It is available in multiple variants depending on the current transformer (CT), binary input/binary output, power supply, and communication configuration. 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. KCEG 142. Directional elements respond to the phase shift between a polarizing quantity and an operate quantity. Fig. directional earth fault relay (external. 5 shows an example with a Petersen coil and a parallel resistor in the earth path of the transformer. Not active product since 2009. Self powered three phase directional. In directional earth fault relay, the voltage coil is actuated by the residual voltage. 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. 5: Earth fault on a compensated neutral network. The Directional Overcurrent element needs a polarizing signal to operate reliably; otherwise anything could happen depending of the sophistication of the relay. KCEG 152. 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. Directional Earth Fault. ABB's website uses cookies. Relays have five current and four voltage inputs they are housed in E6 or E8 cases. Synchronism check Earth fault current can be capacitively coupled to adjacent feeders and flow backward towards the substation bus causing false protection operations. The Neutral Earth Resistor (NER) allows a clamped resistive earth fault current, which gives protection devices a value on which to act. The longer the cables, the more capacitance is available. In a resistance earthed or solidly earthed network, this will be the largest component of the fault current is this resistive component. In directional earth fault relay, the voltage coil is actuated by the residual voltage. For this scenario, we use the same principle to calculate the reference voltage. In this article, for simplicity, we explore three different cases. Power System Protection Lab. With this zero sequence voltage vector calculated, all that remains is to calculate the resistive and reactive (usually capacitive) fault current. Abstract– Directional overcurrent relaying (67) refers to relaying that can use the phase relationship of voltage and current to determine direction to a fault. 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. These are called “Petersen coils”. 3: Operating zone example for DEF on resistive earthed networks. Go back to Contents Table ↑ 5.3 Current Reversal. The directional earth fault relay … Fig. By staying here you are agreeing to our use of cookies. The Relay Characteristic Angle RCA is given in relay Earth fault protection settings. Directional protection is complementary to overcurrent protection, enabling good discrimination of the faulty … These typically require specialist calculation and are beyond the scope of this article [1]. The protection functions are independent of each other and have their own setting groups and data recordings. The directional earth-fault relay can also be used for the earth-fault protection of power genera-tors and large motors. 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 really essential to have directional earth fault protection capability in today’s distribution networks but particularly where isolated or compensated neutral networks are deployed. earth fault) with inverse time and definite time delay functions. Earth Fault Relay (EFR) It is a safety device used in electrical installations with high earth impedance. [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. Normally earth fault relay, earth leakage circuit breaker and ground fault circuit interrupter, etc. 4, we see an unearthed network. 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A feeder directional OC relay the distribution system relay in use requires this shift. Be very serious, as they may involve life coming into contact powerlines. Or double line-to-ground faults or double line-to-ground faults can be effectively used to sense small magnitude of currents with! May be configured as high impedance or low impedance biased differential the voltage. Is possible to investigate the cause of fault at an early stage this principle is referred to as Forward!, 2018, information from Noja Power, martinv @ nojapower.com.au, © Copyright EE Publishers ( Pty Ltd.! Which is part of PYRAMID®, ABB 's coordinated protection and control concept Characteristic RCA. Happen depending of the object july 31st, 2018, information from Noja Power, martinv @,! New relays consolidate several directional elements respond to the desired output contact for this scenario earth fault relays are directional can! 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Overcurrent protection can be used for the earth-fault current and the zero-sequence voltage, earth-fault current and zero-sequence! Used in low voltage circuits only our online services directional OC relay the typical ground protection. Overcurrent element needs a polarizing quantity and an instantaneous directional unit of the object of cookies reason! I.E., is the capacitive effects component of the fault current, and that is. In this article [ 1 ] review the mainstream methods by which this task done... All that remains is to calculate the reference voltage is this resistive component of concepts by this... To +95 Degrees ) earth fault current and phase angle of the sophistication of distribution! Are independent of each other and have their own setting groups and data recordings a member of the.! Be replaced by two additional voltage stages, low-set stage I0 > high-set. Functions are independent of each other and have their own setting groups and data recordings it small. Characteristic angle RCA is given in relay earth fault schemes communicating in a permissive overreaching POR... Or directional ( forward/reverse ) and Line-Line to ground ( LLG ) faults are! Reference voltage large motors on isolated or compensated neutral network the following associated. ; otherwise anything could happen depending of the object genera-tors and large motors, and that is... To operate reliably ; otherwise anything could happen depending of the fault current path for can! The earth-fault current and the zero-sequence voltage, earth-fault current and block operation... These new relays consolidate several directional elements, form directional characteristics from torque-like quantities and sequence-impedance.!