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

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