Solenoid type relay it consists of a solenoid and movable iron plunger arranged as shown. Testing directional overcurrent relays from valence. The function will block the phase over current, earth fault, sensitive earth fault and negative sequence over current. Sel351 negative sequence overcurrent testing problems. Rms thermal overload thermal overload protection provides both alarm and trip stages. A technicians approach to cable testing directional. Ird directional overcurrent ground relays these relays are ground directional overcurrent relays which are used for the protection of transmission lines and feeder circuits. Be147n negative sequence voltage relay automation now.
The negative sequence relay has earthing which protects them from phase to earth fault but not from phase to phase fault. Negative sequence overcurrent element application and coordination in distribution protection a. Negative sequence relay is employed for the protection of generators and motors against unbalanced loading that may arise due to phase to phase faults. Advantages negative sequence overcurrent elements provide outstanding resistive from ee 45 at aachen university of applied sciences. Plug setting multiplier and is defined as the ratio of fault current in the relay coil to the pick up value. Inc51a negative phase sequence time overcurrent relay author. The negativesequence current produces a reverse rotating magnetic field in the air gap. Instead of relying on the product of negativesequence voltage and negativesequence current, the sel321 relay uses the ratio of these two quantities. A positive sequence directional relaying algorithm for seriescompensated line. A negative phase sequence or unbalance relay is essentially provided for the protection of generators and mot. The relay is intended for use at locations where the present equipment or system conditions do not permit the use of the conventional types of directional ground relay operating entirely on residual current and voltage. Locate the portion of the system where you want to implement the negative sequence protection. Under normal operating conditions, the current through the relay coil c is such that it holds the plunger by gravity or spring in the position shown. Negativesequence overcurrent considerations for induction.
Troubleshooting and lessons learned using protective relay. The ansiieee number code designation for a directional current sensing protection is 67. B negative sequence overcurrent relay and protection assemblies application negative sequence current relays are primarily applied to protect generators and motors but also sometimes used in transmission systems to detect unbalanced conditions and faults. The electromechanical technology severely limited the sensitivity of these relay. Sel test procedure negativesequence voltpol directional.
The relay functionality allows highly flexible settings for current and time grading making it compatible with all types of overcurrent protection. If we rotate the standard phasor diagram by 90 and add the same labeling used by the relay bulletin drawings, we can see that simply adding voltage will allow us to successfully test every relay of this type. Negative and zero sequence directional overcurrent unit. The negative sequence current and voltage are obtained by means of selfcontained negative sequence current and voltage filters. Current polarization has its own problems, specifically the current in the neutral to ground connections in a wyedeltawye or an autotransformer can exhibit an indeterminate. Identify the device you want to setup the negative sequence elements in. The directional unit operates on negative sequence current and voltage and the overcurrent unit operates on residual or ground current. The software overlays the characteristics of each of the elements in both the it diagram and the directional diagram. V 2 and i 2 are negative sequence voltage and current quantities, respectively, both of which are measured, and z l2 is the modeled negative sequence line impedance, which is known.
Enhance your power system protection with negative. This directional over current relay employs the principle of actuation of the relay, when the fault current flows into the relay in a particular direction. The magnitude of the torque is proportional to the per unit negative sequence current in the stator. The type krq relay is a highspeed directional overcurrent ground relay in which the directional unit operates on negative sequence current and voltage, and the over current unit operates on residual or ground current. The type crq relay is a directional overcurrent ground relay in which the directional unit operates on negative sequence current and voltage, and the over current unit operates on residual or ground current. Digital relay, over current relay, inverse and instantaneous characteristics, slope detection, relay coordination, directional overcurrent relay. This includes all of the elements which respond to the type of fault applied.
Us5349490a negative sequence directional element for a. The relay is also used to detect unbalanced load currents in motors. The prior art relay did not operate correctly and was removed from service during the open pole period. The operate quantity is typically residual ground current 3i0, measured or calculated, or negative sequence current i2. The relay operates for the defined direction when the fault current is in the same direction and exceeds the over current setting value. Directional element design for protecting circuits with.
Considerations in choosing directional polarizing methods for. The classical method for detecting ground faults on a looped system has been to use directional overcurrent relays that measure the zerosequence current 7, 15. Thus a total current of twice the zero sequence current would flow through the relay and would therefore cause its operation. One is a directional element, which determines the direction of current flow with respect to a voltage reference. Directional overcurrent 67 protection electric power. Negative sequence overcurrent relay and protection. Directional overcurret ground relays crq, ird, irp, irq. The type krq relay is a highspeed directional overcurrent ground relay in which the directional unit operates on negative sequence current and voltage, and the overcurrent unit operates on residual or ground current. Troubleshooting and lessons learned using protective relay event analysis ge digital energy multilin. The sel321 relay negative sequence impedance directional element uses the same quantities as we covered in the previous sections but determines direction using a different equation. Directional relay does not measure the power but is. High load flow through a long nontransposed line may produce sufficient negativesequence current to operate sensitively set negative. The negativesequence generated magnetic flux induces highfrequency currents in the rotor.
As a result, they could provide only backup protection for uncleared phasetophase and ground faults. Mar 28, 2017 relay which protects the electrical system from negative sequence component is called a negative sequence relay or unbalance phase relay. Restricted earth fault ref inversetime negative sequence overcurrent 51q. Over this value the directional relay uses standard polarisation the measured voltage, under this. But, if unbalancing occurs, the secondary currents will be different and the resultants current. Negative sequence overcurrent relay and protection assemblies 1mrk 509 045ben revision. The magnitude of negativesequence current produced by the nontransposition depends on line configuration, line length, and magnitude of power flow. Description 33 position switch 34 master sequence device 35 brushoperating or slipring short circuiting device 36 polarity or polarizing voltage device 37 undercurrent or underpower relay 37p underpower. Negativesequence overcurrent considerations for induction motor loads miles dupuis, cleco power llc nick mahoney, aadityaa padmanabhan, and krithika bhuvaneshwaran, schweitzer engineering laboratories, inc. The negative sequence relay has a filter circuit which operates only for the negative sequence components. Study and performance analysis of digital overcurrent relay. As with zero sequence directional elements, the relay calculates torques to determine the direction of the fault.
Pdf a positivesequence directional relaying algorithm for. Under abnormal condition under abnormal conditions voltage in the circuit is too low. The negative sequence current produces a reverse rotating magnetic field in the air gap. Using calculated negativesequence voltage and current applied to the relay, the new directional element calculates the magnitude of negative. Automatic testing of positive negative zero sequence overcurrent characteristics overcurrent is used for automatic testing of directional and non directional overcurrent relays with autoassessment of the trip time characteristic, the directional boundaries of the current stages, and the pickupdropoff ratio. However, during high resistance fault the relaying decision based on negative sequence component is not reliable. A simplified logic diagram of the rxiik 4 relay is shown in figure 2. Pdf a positivesequence directional relaying algorithm. The 2nd harmonic blocking detects high inrush current inflows that occur when transformers or machines are connected. Now our directional overcurrent 67 test plan looks like the following drawing where we start with the raw currents and voltages, calculate the nonfaulted phasetophase voltage, and plot the operating current and polarizing signal, which in this case is vbc.
The negative sequence current and voltage are obtained by means of selfcontained negative. Under normal conditions, as equal current flows in all the three phases, their algebraic sum is zero. Negativesequence directional elements use negativesequence voltage as the polarizing quantity and negativesequence current as the operate quantity. A protective relay for detecting faults within a predetermined protected zone of a three phase alternating current electrical power distribution system, of the type which utilizes at least one restraint signal in conjunction with at least one operate signal to generate a net operate signal, generates an operate quantity which is related to a zero sequence component of current flowing in the. The ansiieee number code designation for a directional currentsensing protection is 67. Considerations in choosing directional polarizing methods for ground overcurrent elements in line protection applications technical report to the line protection subcommittee of the pes, power systems relaying committee completion date. Type krq directional overcurrent negative sequence ground. Presented at the electric council of new england protective relaying committee meeting no. The relay always has a low current setting because the small magnitude overcurrent can cause dangerous situations. Negativesequence overcurrent element application and coordination in distribution protection a. Using calculated negative sequence voltage and current applied to the relay, the new directional element calculates the magnitude of negative. Directional overcurret ground relays crq, ird, irp, irq, irv. The type crq relay is a directional overcurrent ground relay in which the directional unit operates on negative sequence current and voltage, and the overcurrent unit operates on residual or ground current.
Overcurrent automatic testing of positivenegativezero. Negative sequence overcurrent relay and protection assemblies. The negativesequence or zerosequencebased overcurrent function with the choice of either negativesequence or zerosequencebased directional fun ction. Apr 25, 1989 a primary advantage of the negative and zero sequence directional overcurrent unit of this invention is that it can function correctly with one pole open on the transmission line. Where does negative phase sequence relay is employed. The sel321 relay negativesequence impedance directional element uses the same quantities as we covered in the previous sections but determines direction using a different equation. The relay is intended for use at locations where the present equipment or system conditions do not permit the use of the conventional types of directional ground relays operating entirely on residual current and voltage. This p roduces a retarding effect on motion of the rotor in either di rection. Directional relay algorithm based on phasor components either uses voltage or current information as a reference quantity. Directional relay are used when graded time overload protection is applied to ring mains and interconnected networks.
Any relay can be made directional by incorporating directional element in it. For example we can use directional element in overcurrent relay to make it directional overcurrent relay. The negativesequence current generates a magnetic field that crosses the air gap and rotates in the opposite direction with respect to the positivesequence generated magnetic field and the rotor. Negativesequence overcurrent element application and. The mrs1 relay produces a negativesequence system by rotating the current. The positive and negative sequence based directional relaying techniques have. Many microprocessorbased relays now offer negativesequence current elements as a means of detecting ground faults and determining fault direction 4. This relay had a rolled phase, but also a lot of other issues during start up, verify metered values negative sequence voltage and current should be small relative to positive sequence quantities power factor should be as. The current in the negativesequence system is a measure for the magnitude of the unbalancedload. Instead of relying on the product of negative sequence voltage and negative sequence current, the sel321 relay uses the ratio of these two quantities. As with zerosequence directional elements, the relay calculates torques to determine the direction of the fault.
The scalar quantity is then compared against two threshold quantity settings, one to determine a forward fault, the other. Negative sequence overcurrent relays are used to detect unbalanced load on a generator which may cause excessive rotor heating. A positivesequence current based directional relaying approach for ccvt subsidence transient condition monalisa biswal and sandeep biswal abstract in this work, a directional relaying algorithm is proposed for transmission line to prevent relay maloperation during coupling capacitor voltage transformer ccvt subsidence transient. Therefore the driving torque becomes abnormally too small. Thus the relay operates due to flow of current i y through it. The advantage of the negative sequence current over. Advantages negative sequence overcurrent elements provide. Document name prevention of sensitive line protection. However, on the occurrence of a fault, the current through the relay coil becomes more than the pickup value, causing. Sel test procedure negativesequence voltpol directional overcurrent element i am writing to enquire about 67n test procedures, specifically schweitzer relays. Under frequency negative sequence relay my tech info. Directional over current relay from the previous discussion t v i cos. The negative sequence current and voltage are obtained by means of.
The negative sequence current and voltage are obtained by means of selfcontained negative current and voltage filters. Almost all negative sequence voltage polarized relays compare the negative sequence voltage v2 and the negative sequence current i2 to establish direction. I am attempting to test the negative sequence overcurrent on a 351 and 351s with an omicron test set and my test plans just dont seem to be working very well. Negative and zero sequence directional overcurrent unit for.
Normally, the conventional over current relay nondirection will act for fault current in any direction. Negative phase sequence relay and its types electrical. Abstractnegativesequence overcurrent elements can 51q add sensitivity to transformer and feeder protection. Directional overcurrent protection reyrolle 7sr120. The mrs1 relay produces a negativesequence system by rotating the currentvector il2 by 240 and the currentvector il3 by 120. A directional element measures the negative sequence voltage and the negative sequence current and from those quantities produces a scalar quantity related to the negative sequence impedance of a power transmission line relative to the location of the directional element. May 2015 members, working group d3 considerations in choosing directional polarizing methods for ground. Find the phase overcurrent pickup amps of this relay. It is noted that at junction b current i 1 and current i 2 are equal but opposite to each other, so they cancel each other and current i y flows through the relay operating coil. Voltage controlled overcurrent voltage controlled overcurrent provides backup protection for remote phase. Now identify the immediate downstream overcurrent protective relay. For decades, electromechanical negative sequence overcurrent relays have been provided as standard unbalanced current protection for moderate and large generators. Introduction in some medium voltage distribution lines and almost all high voltage transmission lines, a fault can be in two different directions from a relay, and it can be highly desirable for a relay to respond differently.
One such application is generator protection, where an overcurrent relay monitors the amount of current at the point where an electrical power generator connects to a larger network of generators. What is negative sequence current and how does it affect. The relay is connected in parallel across the current transformer secondaries. Further, the zero sequence current due to load current flowing through dissymmetries in the power system, such as untransposed lines, or lines with an open pole, is. The arrangement of negative sequence relay connection is shown in the figure. The relay can also be used in the other applications such as. Inc51a negative phase sequence time overcurrent relay. The time characteristic of the trip circuit of the sgc relay is i 2 2t k, with k being continuously adjustable from 2 to 40 see figure 1, next page.
Negative sequence overcurrent negative sequence overcurrent protection can be set as either nondirectional or directional forwardreverse, and can operate for remote phasephase and phase earth faults even with deltastar transformers present. The negative sequence current and voltage are obtained by means of selfcontained negative sequence filters connected between the directional. To make the relay inoperative under the influence of zero sequence current, the cts are connected in delta, because then no zero sequence current can flow in the network circuit. I type ibc51a relay disassembled front view 0, \,p. The relays are available in single and four pole variants housed in e4 cases with the iec61850 protocol option housed in an e6 case. The magnitude of the torque is proportional to the per unit negativesequence current in the stator. This permits matching the characteristics of the relay with the i 2 2t capability of the machine to be. Directional non directional overcurrent protection. A positivesequence current based directional relaying. Pdf this paper presents the design of a digital directional and non directional over current relay and its performance on matlab. This field produces a shaft torque pulsation at twice line frequency. Negative sequence directional element provides better directional security during spt condition 2932. Directional overcurrent relays 67 respond to excessive current flow in a particular direction in the power system.
In a compensated boosted negative sequence directional element, the boost provided to v 2 for low impedance strong sources is. Negative sequence directional elements use negative sequence voltage as the polarizing quantity and negative sequence current as the operate quantity. The type krq relay is a highspeed directional overcurrent ground relay in which the directional unit operates on negative sequence current and voltage, and the overcurrent unit operates on residual current. Considerations in choosing directional polarizing methods. The negative sequence current and voltage are obtained by means of selfcontained negative sequence filters connected between the directional unit and the current and potential transformers. Given the same system, the negative and zero sequence directional overcurrent trip unit of the present invention will operate for fewer external faults than will prior art units. Rca the characteristic angle is the phase angle by which reference or polarising voltage is adjusted such that the directional relay operates with maximum sensitivity. Introduction in some medium voltage distribution lines and almost all high voltage transmission lines, a fault can be in two different directions from a relay, and it can be highly desirable for a. If the power flow is in the opposite direction, the relay will not operate. Modes of operation the relay makes its directional decision by determining if the angle between the operating current and polarizing voltage has entered the elements operating sector.
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