This principle of protection is capable of detecting very smallmagnitudes of the differential currents. [Reference-2]. To compensate for these influences, the differential relay is stabilized, that is, the relay is given a characteristic basically similar to that in Figure 12.13. Generator full load current in secondary = 5533/8000 = 0.692. Differential protection is a very reliable method of protecting generators, transformers, buses, and transmission lines from the effects of internal faults. There are three basic insulator materials available. Poor adjustment of rated CT data to rated generator data by these factors a fault current is caused which mainly depends on the biasing current. The differential relay minimum pickup setting need to be adjusted to detect faults on as much of the Reverse Power (32) Generator Protection Setting Calculations Generator and transformer test sheet data, and system information: X d =24.5% X T = 10% on generator base X SYS = 6.25% on generator base Use graphical method to determine settings. 185.142.154.245 Pick-up = 0.3 A (480 A primary sensitivity) Slope = 10%. them differential relay is very commonly used relay for protecting transformers and generators from localised faults differential relays are very sensitive to the . Generator Protection - Setting Calculations Overfluxing Capability, Diagram 24 - Volts/Hertz (Overfluxing) 0 200 400 600 800 1000 1200 1400 1600 1800 2000 1.40 p.u. They are used for differential protection (87M) of a 2250KW, 0.8 PF, 4.16KV, standby diesel generator. has a slope 1 setting of 30% and a minimum differential operating current setting, IDIFFmin= 20% (or 200mA 97d5U`J|NNO=cG Also known as unbiased differential protection only one actuating relay quantity (current) required for . 772 0 obj <>/Filter/FlateDecode/ID[]/Index[763 18]/Info 762 0 R/Length 64/Prev 631612/Root 764 0 R/Size 781/Type/XRef/W[1 2 1]>>stream Generators are very sensitive equipment, we should protect the generatorin this we have given around 86 number of relays and its detained explanation.. . The percentage differential principle originally developed for transformer and generator protection was extended for use on short transmission lines already in the 1930s, and is still widely in use. Differential Protection - Courseware :: Centurion University The proposed adaptive setting of the generator-transformer unit overall differential protection (87O) can be with either the P-Q or R-X plot. A impact on setting generator protection. Hence transformers near the generating source have a longer inrush phenomenon, while at substations remote from the generating sources, the inrush is not as severe as the increased inductance and resistance of the line reduce the peak magnitude and damp the current. Transformer protection relay calcul. Reduced battery load with low burden power supply. Differential protection compares two (or more) currents to locate a fault; which actually makes current protection. All other settings for the operating characteristic can be left to the default values. The following pickup characteristic (exact characteristic) gives a detailed study of the individual fault factors and the resulting fault current. The differential scheme studied here is called a circulating-current circuit due to the fact that the current continuously circulates in the interconnecting leads of this circuit. No current flows in the relay and the voltage that appears across the paralleling points is zero. Generators, unlike some other power system components, need to be protected not only from short circuits, but also from abnormal operating conditions. In a differential protection scheme in the above figure, currents on both sides of the equipment are compared. HV6+p$SK )-SmV$$j7g !QxfzzfirL6e4Y=_w7U9iH%o4s2mey|H*>uZ&;|6/N2&Hct?Ac 87G Generator Differential. The two or more actuating quantities should be similar. Under this condition the saturated transformer secondary winding presents an impedance which is practically equal to its DC resistance, since the leakage reactance of the full s-hiding of the toroidally wound CT can be neglected and a secondary current will be forced through the saturated CT equal to the sum of the secondary currents in the remaining paralleled as, less the current through the high-impedance relay which is negligible. Differential protection schemes are mainly used for protection against phase-to-phase fault and phase to earth faults.The differential protection used for power transformers is based on Merz-Prize circulating current . 0 Figure : Typical bias characteristics of percentage differential relay. Functions which can be programmed by the user. Differential relays, in particular the digital ones are used to detect stator faults of generators. X1kUU f``pL p%1JDh%{*m+rl\e ;A(^U:]q3noF( 3o~*@F|fME"FuAQI>`}- The total tripping time of the Relay is below 35 ms. [Reference-3]. Generators do experience short circuits and abnormal electrical conditions. As already mentioned above, the differential protection is applied not only (or protection of segments of lines, but also for protection of such important system components as transformers, reactors, generators. The differential relays detects a current difference of I1-I2 = Id and trips when Id has exceeded the set threshold. Electric power utilities and industrial plants tradionally use electromechanical and solid-state relays for protecting synchronous generators [3]. Generator Load Responsive Protection Functions (Ref. Unequal DC component in the short circuit current. 4, October 1992. The relay may lose its stability through faults. This certainly causes operation of differential relay though there is no fault in the transformer. To distinguish between faults occurring within (internally) or outside (externally) of the protection zone is the main purpose of the differential protection because at internal faults the differential protection relay must trip, but not so at external faults. . Generator protection is different and complex as compared to other equipment and machines due to the reason that it is connected with 3 other systems simultaneously, a DC exciter circuitry for providing DC to field winding, a prime mover for rotating rotor and is synchronized with the grid. The presentation explains about the simple differential protection, biased differential protection and also the advanced numerical relay working in generator. Generator protection relay setting calculations (.pdf) Generator protection (.pdf) Protection of Synchronous Generators (.pdf) endstream endobj 768 0 obj <>stream Due to such high selectivity of protection, there is no need to activate a delay for the relay pick-up, which is why all differential relays are high speed. Short-circuit protection (overcurrent protection, impedance protection, differential protection) Stator ground-fault protection (90% non-directional or directional, 100% with 3rd harmonic, real 100% . Differently, the increase of circulating current results in a desensitization of the relay to a differential current. Possible sources of measuring errors are systematic and can be duly taken into account. "A differential relay is defined as the relay that operates when the phasor difference of two or more similar electrical quantities exceeds a predetermined value.". The difference between incoming and outgoing currents of all generator terminals is small (in ideal cases = zero) I1-I2 = 0. 2. Dependent on the earthing method used, the neutral can also be included in measuring and balance. Figure : Connection diagram for high-impedance differential relay type. It is because the high earthing resistance will limit the earth-fault currents to a low value, necessitating relays . In order to overcome this difficulty differential relays are used. In many cases, equipment damage due to these events can be reduced or prevented by proper generator protection. For protecting two parallel high-voltage lines of wide applications, transverse differential current protection is implemented, based on a comparison of the magnitude and phase of the currents in the parallel lines (Figure 2). They are Porcelain/Ceramic insulator Glass insulator Polymeric Composite insulator, Difficulties Associated With Differential Protection. Figure : Normal Differential Protection and percentage Differential relay. Earth fault. The ratio error of CTson either side differ during these condition due to. The following limitations on CTs are required for applying these relays: All C.Ts in the differential circuit must have the same ratio. They generally increase as the load on the transformer increases. Two significant disturbances are the 1996 western area disturbances and 2003 east coast blackout. 87 Phase Differential 87G Generator Ground Differential 87T Transformer Differential 87O Overall Differential 18 . It is essentially a circulating current differential relay which employs additional restraining coils. Whatever secondary voltage is generated by the core flux of the saturated CT will also reduce the voltage across the paralleling points. The worst condition of unbalanced secondary currents is realized when the CT in the faulted circuit is completely saturated and none of the other CTs suffer a reduction in ratio. The features which govern the operating characteristics are (a) current setting; and (b) operating time. If a fault develops inside of the protected zone, currents I1 and I2 are no longer equal, therefore i1 and i2 are not equal and there is a current flowing through the current relay. Abstract. If CTs of identical ratios are used on neutral and line side of generator, an operating current setting of 20% it can be adopted. 3. SPAD of ABB) is done with illustrative figures. The BE1-11 g has many features to address issues with reliability . At low values of the circulating current the curve does not rise more steeply than is necessary with a view to the spill currents, and changes its slope only when the circulating currents are such that the as are approaching saturation. Cloudflare Ray ID: 766944c19c70bb25 Generator Protection -Setting Calculations 24 -Volts/Hertz (Overfluxing) 0 200 400 600 800 1000 1200 time Overfluxing Capability, Diagram 1400 1600 1800 2000 1.40 p.u. From my point of view, you need increase setting of protection. Examples of such abnormal conditions are over-load, over-excitation, over-voltage, and loss of field, unbalanced currents, reverse power, and abnormal frequency. Current/ Current. Generator Relay Schweitzer Engineering Laboratories applications for complete generator or unit protection. In case of power transformers, the percentage basic setting is of the order of 20 % and percentage pick up value is of the order of 25%. This course presents a comprehensive and systematic description of the concepts and principles of operation and application of protection schemes for power generators. Under normal conditions, or for a fault outside of the protected zone, current I1 is equal to current I2. The practical way of calculating differential protection settings for a Relay (e.g. If two identical power lines are run in parallel from one substation to another and are connected, to the buses by a common circuit breaker, a common protection is installed for both lines and will trip out the circuit breaker when a short circuit occurs on any one of the lines. The results are applicable to other internal unsymmetrical faults also. On one hand, these resistances effectively limit voltage in secondary circuits of the CT when a high-impedance differential relay (Figure 4) is used, and on the other hand they provide pick-up of the relay shunted by this resistance at a certain voltage level. %PDF-1.6 % 8. The relay in this case operates to transmit impulses to trip the circuit breakers at both ends of the faulted line. The differential protection is called unit protection because it is confined to protection of a particular unit (equipment) of a power plant or substation. As a result, differential protection is the most important concept in protection. The following restraining characteristics are usedone, two or all three of them, depending on requirements given below: A differential relay may mal-operate on external faults due to C.T. endstream endobj 767 0 obj <>stream Stabilizing the relay means always an action to make the relay more insensitive. In this paper, we examine the degree of protection afforded by the various types of differential elements (phase, negative, and zero sequence) for stator winding faults. Sometimes an additional restraint is provided by some manufacturers and this will be described later. You can email the site owner to let them know you were blocked. The following are the available information: (1) There are 3 ABB 419M relays (Model 419M, IB 7.6.1.7-1). A digital differential technique for detecting generator stator winding internal faults has been presented in this paper. This depends on the type of relay and the magnitude of the differential current, Expressed as a multiple of this current setting. An available advanced synchronizer (25A) includes selectable phase-lock-loop and anticipatory modes. This aspect is taken care of by a biased differential, Protection of generator, protection of generator transformer unit, Protection of feeder (transmission line) by pilot wire differential protection, Protection of transmission line by phase comparison carrier current protection. 5533. A differential relay is defined as the relay that operates when the phasor difference of two or moresimilar electrical quantities exceeds a predetermined value., The current transformer and machine to be protected are located atdifferent sites and normally it is not possible to connect the relay coil to the equipotential points. The action you just performed triggered the security solution. During a short circuit occurring at the grid, the short circuit current flows through the generator. Current setting: This setting determines its sensitivity on internal faults. 780 0 obj <>stream Therefore, Id/Ib> 0.0x. This may also result in unwanted operation on external faults. These currents are general being different in magnitude. Figure1 Typical Application. Irrespective which one of the two possible solutions is used differential protection characteristic settings can be set in the same way. The heart of this form of protection is the differential relay in which the current on the primary and secondary sides to the transformer to be protected are compared with respect to magnitude and phase relationship. Because, with the rise in current, the restraining torque increases and I1-I2 arising out of difference in CT ratio is not enough to cause the relay operation. The basics of a differential application include: Synchronous generator is the most important element of power system. i1 = i2 and no current flows through the current relay. N|G1TS:W7E&/K=|7-Dg{tVia?I 7cZHxUqiM!e[maVO*;EUh?[sJ0oc{O^.yH?[|x^dp8aq4VD0;e9"pYsa\9"#{ the fault is within the generator's differential zone of protection anyway, so an 87G trip is expected . Fundamental analysis Distortion factors for differential current measuring are: In fig. M. S. Sachdev and D. W. Wind, Generator differential protection using a hybrid computer, IEEE Trans. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data. The working element of such a high-impedance differential relay is a voltage relay. setting the generator protective relay functions eep, rem 610 motor protection relay library e abb com, generator This selection is recommended for the example generator. If the secondary currents of CTs CT1 and CT2 are denoted, respectively, by I1 and I2, and the positive, direction of the current in the relay is taken to be that of current I1, during normal operating conditions on line AB (here and hereinafter vector values): This relation is valid by virtue of the fact that the impedance of the winding of relay (usually a current relay) is considerably less than that of the current transformer secondary windings and it can hence be considered that the secondary currents flow through interconnection leads and complete their circuit through the relay winding. Generator Protection Setting Calculations. However, because of different voltage levels, fault levels, ratios and makes, C.Ts on one side may saturate and cause spill current to flow through the operating relay resulting in unwanted operation. In such a case, there is no option but to delay the protection operation. In this situation a solid generator-terminal fault creates roughly 100% of rated current. 95 TP102, 1995. . So therefore the current balance shows a difference. 7, no. Case study results shows that the technique used correctly discriminates between internal and external faults on the stator winding. It is obvious that under external fault conditions, no higher voltage than this can exist, since either a reduction in ratio of any of the other CTs or a diversion of current through the relay will reduce the current through the saturated transformer secondary. Because the These are the main factors which make protection necessary for the generator or alternator.Even when properly used, a machine in its perfect running condition does not only maintain its specified rated performance for many . Thus a current differential relay is one that compares the current entering a section of the system with current leaving the section. THE ABOVE TIME SETTING SHALL BE CO-ORDINATED WITH LINE PROTECTION. Performance & security by Cloudflare. 1.35 1.30 1.25 1.20 1.15 1.10 1.05 1.00 [1] In this configuration, an op amp produces an output potential (relative to circuit ground) that is typically 100,000 times larger than the potential difference between its . Accurate, repeatable, and reliable operation. This appears as an internal fault to the differential relay. If a real fault occurs, the measured differential current exceeds the biasing current caused by operational conditions. Please include what you were doing when this page came up and the Cloudflare Ray ID found at the bottom of this page. 763 0 obj <> endobj 3. 500 ms at two times the current setting depending tin the type of relay. AbstractDifferential protection is often touted as being The protection for generator stator windings. Working Principle, Circuit Breaker: Operation and Arc Phenomenon, Location of Cable Faults: Types and Methods. Generator The generator protection is installed at the generator side of the PCC and protects the DG from internal faults and abnormal operating conditions.
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