For example, when used for motor protection, the relay can recognize a single phase condi tion even though the motor may be supplying considerable back emf after having one phase. So far, it has functioned much better with the negative sequence than. Abstract this paper describes the development of a new static negative sequence relay for generator protection. The basic theory of symmetrical components is that phase currents and voltages in a three phase power system can be represented by three single phase components. Type coq negative sequence generator relay 5060 hertz. Pdf modeling and simulation of digital negative sequence. As with zero sequence directional elements, the relay calculates torques to determine the direction of the fault. There are three voltages or emfs in the three phase system with the same magnitude, but the frequency is displaced by an angle of 120 deg electrically. The earth relay provides protection for phase to earth fault but not for phase to phase fault.
The relay derives the nps voltage from the three input voltages vl1, vl2 and vl3. The algorithm has been formulated to be suitable for use in a numeric relay to determine either the absolute value of the negative phase. A relay which protects the electrical system from negative sequence component is called a negative sequence relay or unbalance phase relay. Distinguishes between correct phases, phase sequence, and phase loss when power is turned on. 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. The micom p343 is suitable for protection of larger or more important generators, providing generator. Pdf extracting negative phase sequence components from the threephase. Rebirth of negativesequence quantities in protective. What is negative sequence current and how does it affect. Reverse phase or phase balance current relay operates when the polyphase currents are of reverse phase sequence or when the currents are unbalanced or contain negative phase sequence components greater than a set value.
Relay which functions in conformance with the positive phase sequence component of the current, voltage, or power of the circuit explanation of positive phase sequence relay. View and download basler be147n instruction manual online. Where does negative phase sequence relay is employed. Mar 28, 2017 relay which protects the electrical system from negative sequence component is called a negative sequence relay or unbalance phase relay. The integral autorecloser with check synchronising can be confi gured to grade with downstream reclosers. 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. Supports phase loss detection when the motor is operating. Phasesequence phaseloss relay k8akph threephase phasesequence phaseloss relay using voltage detection method greater resistance to inverter noise. For phase to phase faults an earth relay cannot provide necessary protection and hence negative phase sequence relay is required. Symmetrical components made easy part 1 manta test. Inc51a negative phase sequence time overcurrent relay. A ground fault in the generator zone produces primarily zero sequence voltage.
This will be affected to a lesser extent than the measurement of negative sequence current alone, since the ratio is approximately constant with variations in load current. Negativesequence overcurrent considerations for induction. A negative phase sequence or unbalance relay is essentially provided for the protection of generators and mot. Negative sequence relay is employed for the protection of generators and motors against unbalanced loading that may arise due to phase to phase faults. We theorized that with negative sequence protection, it might provide more sensitive detection, wo nuisance tripping. Abb library is a web tool for searching for documents related to abb products and services. In this paper the authors have developed a protection scheme using logic based detection of negative sequence currents and for six phase transmission system of allegheny power systemaps, usa. Negative sequence overcurrent relay and protection.
The emphasis is on numerical relays since they have facilitated the calculation of symmetrical components. Find out information about positive phase sequence relay. Integrated logic is provided to allow the optimal configuration of relay functionality with the relays analogue inputs and binary inputoutput circuits. Shortcircuit studies or manual calculation will yield the. Figure 2 negativesequence filter in an electromechanical relay. Sep 20, 2016 the broken conductor protection relay incorporates an element which measures the ratio of negative to positive phase sequence current i 2 i 1. Generator protection with a new static negativesequence relay. The negative relays are also called phase unbalance. The feeder is a long line, and the phase overcurrent relays would not pickup any faults, even when the lines were broken and on the ground still energized. The relay functionality also allows its application in autotransformer and reactor protection schemes. Stator winding diagram illustrating pitch in winding construction.
Negative sequence quantities the voltage and current denoted by v2 and i2 are very useful quantities in protective relaying. Instead of relying on the product of negative sequence voltage and negative sequence current, the sel321 relay uses the ratio of these two quantities. Modeling and simulation of digital negative sequence relay for. Phase sequence relays application the type 47 provides undervoltage and reverse phase detection. Apr 08, 2014 symmetrical components made easy part 1 before computer software applications, the task of calculating fault currents for a threephase electrical system was a challenging task. Inc51a negative phase sequence time overcurrent relay author. Back to the basics event analysis using symmetrical components. The mrs1 relay is a negative sequence protection relay with universal application. The advantage faster and more sensitively than phase overcurrent relay of the negative sequence current nsc components over zero ocr for phase to. Block diagram for implementation of digital negative sequence relay ansi 46 logic diagram for. Negative sequence overcurrent relay and protection assemblies 1mrk 509 045ben revision. The concept of negative sequence current is rooted in symmetrical component methodology. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solidstate relays. As shown by the curves of figure 5, the rel ay s char.
For example, with a time dial setting of 4 the relay will close its contacts in 30 seconds with the above tap currents applied to the relay. A negative sequence relay has a filter circuit which is operative only for negative sequence components. The negative sequence relay protects the generator and motor from the unbalanced load which mainly occurs because of the phase to phase faults. Negative phase sequence relay k6nqovg572lw idocpub. Pdf novel microprocessor based negative phase sequence. Negative phase sequence relay and its types electrical.
The negative phase sequence current present in the circuit will be of same frequency but the phase sequence will be negative to the system sequence. Phase sequence component an overview sciencedirect topics. Sel351 negative sequence overcurrent testing problems. Negative phasesequence overcurrent protection nsptoc main settings. A sensitive negative phase sequence alarm with continuous remote indication is also provided to warn the operator of increase in nps level in the generators.
No doubt, an earth relay can also provide the desired protection but only in case when there is a fault between any phase and earth. These are positive, negative and zero sequence components. I am attempting to test the negative sequence overcurrent on a 351 and 351s with an omicron test set and. With a large number of different tripping characteristics and adjustment possibilities, the tripping characteristic can be made suitable for al. Pdf a novel numeric relay algorithm for extracting negative phase. Modeling and simulation of digital negative sequence relay for unbalanced protection of generator. This paper describes an event in which a 51q element operated for a fault on. Be147n negative sequence voltage relay automation now. Positivephasesequence relay article about positivephase. Phase sequence voltage relay operates upon a predetermined value of polyphase voltage in the desired sequence. Phase and zero sequence phasors for a single phase toground fault negative sequence directional elements use negative sequence voltage as the polarizing quantity and negative sequence current as the operate quantity. It is more sensitive to unbalanced line voltage than competitive types.
Negative sequence overcurrent relays are used to detect. Negative sequence relays electrical impedance relay. A simplified logic diagram of the rxiik 4 relay is shown in. Negativesequence components are used to detect phaseto. It serves for negative sequence protection of three phase generators. This relay has a broader range of settings and greater sensitivity to provide protection for modern large generators. Novel microprocessor based negative phase sequence relay and meter.
This paper focuses on the uses of negative sequence quantities in protective relaying. Type coq negative sequence generator relay 41161j 3 time as determined by the time dial setting and is as shown by figure 7. For this reason, the negative phase sequence protection must trip the unit directly category a. Negative phase sequence overvoltage 47 7sr12 negative phase sequence nps voltage v2 is a measure of the quantity of unbalanced voltage in the system. Low order of over current also can cause dangerous situations hence a negative sequence relay has low current settings.
A mathematical theorem using symmetrical components and sequence networks was the most practical method to conduct fault studies. Pdf logic based detection of negative sequence currents. Negative sequence overcurrent relay and protection assemblies. Rebirth of negativesequence quantities in protective relaying. However, certain loads may cause higher than expected negativent to sequence curre flow because their negative sequence impedance is quite low when compared to their positive sequence impedance. This protection is duplicated, one relay connected into each tripping system. Negative sequence current will cause excessive heating of generator rotor as the rotor will experience double the system frequency so far the negative sequence current is concerned.