Generally instantaneous attracted armature type relays are used for this purpose because all they have high speed operation and also they are free from being affected by any AC transient of the power circuit. Figure . Limitations of Differential Protection of Generator. %PDF-1.6 % Figure 4 shows the corresponding 87 phase differential operating characteristics for both the main generator (M-3425A) and backup (SEL-700G) protection. This solution acted immediately on the root of the problem and no other measures were necessary. at the generator terminals or on the external connections. Steve is an IEEE Senior Member and a member of the IEEE PSRC, and has presented at numerous conferences. The first event occurred at 19:02:56 and was due to a three-phase bus fault. Now, we take the case of a generator connected to a transmission line. Click to reveal %%EOF An offshore platform started experiencing sporadic generator differential protection trips during the start-up of a newly commissioned, large water-injection pump (WIP) motor rated at 4,100 kW. Turn on the blower power for stationary models. 230 kV bus is always energized. Do not apply a load higher than the generator-rated capacity. Description. in. If you want to try to set up a differential that subtracts one current from another to get to zero, that's not too difficult for two inputs, but gets complicated fast as the number of inputs goes up. In this circuit, the relay uses a voltage divider consisting of two linear resistors and one non-linear resistor. The excitation system of a generator provides the energy for the magnetic field (satisfying magnetizing reactance) that keeps the generator in synchronism with the power system. Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a parts function at the center of their design considerations. David you were after all only replying to my comment /question in a logical manner (and I hope you will continue to do so anytime I say something that sounds like an uncertainty or a question). Hence all protection system not only trip the generator circuit breaker but also trip the "automatic field discharge switch " 16. Figure 2 shows the oscillography captured by a digital fault recorder (DFR) for the event. commissioning generator relays. You can email the site owner to let them know you were blocked. But here is a document that shows concern for generator differential trip upon energization of transformer outside of the zone. Because the transformer being energized is not in the differential zone, there is no difference in what is seen at the terminals from what is seen at the neutral. 961 0 obj <>stream The stator winding faults are very dangerous, and it causes considerable damage to the generator. Then flip the master load switch on. A large steam turbine generator tripped on 87 phase differential protection while attempting to synch the machine to the grid. All the faults occurring outside of the differential protection zones are the through faults. The generator has its own differential protection scheme. Different types of Turbine Protective Devices like turbine over speed trip, low lube oil pressure, axial displacement, turbine temperature and vibration. Kirchhoff says that sum has to be zero and it doesn't matter how many inputs (restraints) you have. 159.223.218.176 It provides a complete protection and synchronization solution for synchronous generators, so you can eliminate the complexity and cost of standalone synchronizer packages. motor, automatic transmission, brakes, differential and front end. 19-300 Vdc, 16, 9, Removable, Generator, 19-300Vdc, 40-250Vac, 50/60 Hz ,Differential Protection Trip Coil Monitor . will not trip for faults near the generator neutral because of the decreased neutral shift during this type of fault. During the test, you can change the draw by switching KW switches on or off. Hang on guys, this was a running generator, no transformer in the zone that tripped. SA-1 Generator Differential Relay - Class 1E 41-348.11C 3 The percentage slope characteristic of the relay lim- its the operating voltage on heavy external faults where the performance of the two sets of current transformers may be quite different. Abstract: Low-impedance generator differential protection is commonly used for detecting stator phase and ground faults in medium-voltage applications. Low-impedance generator differential protection is commonly used for detecting stator phase and ground faults in medium-voltage applications. Review of the SER also reveals that the 87 phase differential protection repeatedly picked up and dropped out over the course of the event. Electric power & transmission & distribution Forum, thread238-125456: Traces of 2MW transformer inrush, http://files.engineering.com/getfile.aspx?folder=42de7951-21a3-4709-8c08-3e, http://files.engineering.com/getfile.aspx?folder=38aaa3f7-c4e0-495d-85d8-4c, http://files.engineering.com/getfile.aspx?folder=f53b4c82-4766-46ed-8785-e7, http://files.engineering.com/getfile.aspx?folder=c495475e-89fb-4e4f-aa70-59, http://files.engineering.com/getfile.aspx?folder=c6bfbd96-d106-4e37-b865-e3, Low-Volume Rapid Injection Molding With 3D Printed Molds, Industry Perspective: Education and Metal 3D Printing. However, only the main generator protection relay operated not the backup protection. To combine fast fault clearance, as well as sensitivity and selectivity, the "Generator differential protection" is normally the best choice for phase-to-phase generator short circuits. Differential Protection87M Motor Differential Protection87L Line Differential Protection: 1.00pm - 2.00pm: . The root cause of the unwanted trip was a bad sync: The electrical angle across the generator breaker was close to 60 degrees at the time of the closing because of improper timing. . 64R= Rotor E/F2nd Stage =50-80 K OHM alarm &5 K OHM Trip 5. It will trip the circuit breaker. Relays, which depend on excess of current for their operation, are less sensitive because they cannot make correct distinction between load conditions and minor fault conditions. 2022 International Electric Testing Association | All Rights Reserved |. Droop mode, the speed is sacrificed with load. The protected area was the generator only, without a generator transformer connected.In this case, the reason seems to be due to the starting, and sporadically, during the stopping of an HV AC motor. 2. A Generator Differential Relay Trip on an Offshore Platform: A Case Study @article{Gupta2020AGD, title={A Generator Differential Relay Trip on an Offshore Platform: A Case Study}, author={Alok Gupta and Dibyendu Bhattacharya}, journal={IEEE Industry Applications Magazine}, year={2020}, volume={26}, pages={14-25} } Have you checked for proper CT polarities ? Use of a differential pressure switch across this high-pressure element is a method of detecting a motoring condition. Many a time, the generator differential protection (87G)will not have 2nd harmonic restraint feature. Easy to use Generator Differential Protection Relay. 0 Therefore, the excess of excitation current has to be immediately lost in order to avoid tripping.Our explanation is that when the circuit breaker opens CT2 immediately stops delivering current but CT1 carries the magnetising current of the 11kV transformer delta winding. The generator is brought online to full speed; ideally, the generator breaker is then closed when the generator is in sync with the grid. Site tests and measurements might be necessary to collect extra data. which do not call for immediate tripping of Generator. The SR489 doesn't have a 2nd harmonic restraint, so their solution was to add a time delay, which I don't like. The reason is still unclear and extra information is required to make a judgement. (At least from what emivana has said to date.) Generators are the most expensive pieces of equipment on power systems. 1) One protecting only generator (this one trips on energization of 100 MVA tranformer); 2) One protecting generator + 80 MVA transformer (this one doesn't trip). Figure 4: 87 Phase Differential Operating Characteristics, Main and Backup. Figure 1 shows the sequence of events captured by the numerical line current differential relays located at the high side of the generator GSU and switchyard breaker. Common Ramp angles are 7, 11, and 14 as examples. . The differential protection function of a generator relay uses the difference between current into and out of the generator in order to detect internal faults in the generator winding. In this case, the differential protection is set up to protect the generator-transformer block and, therefore, it is known as block differential protection.In the figure below, we can see CT inputs and trip outputs for the block differential protection configuration. 0A]uS7D%D^x;y{ A?Cxh elqQA%9k#8e2}1gm8S~n4Y[qOKxkU6E0lz|')6]?`(CafB B*LYP e6 |Yc46xfce+rY-t. More importantly, is this setup new or existing? A large steam turbine generator tripped on 87 phase differential protection while attempting to synch the machine to the grid. Unless the relay does things differently at the two ends, certainly not a good thing to do in a differential, it doesn't matter what the relay does or doesn't do with/about 2nd harmonics. This is 20 times the current at 110% of the nominal voltage, which is already above the knee-point on the curve. Occasionally a ramp may be machined on a collar. This highest availability is a key factor for reliable power generation. Most generators now have the fifteen amp plugs. Performance & security by Cloudflare. Generator Differential Protection (ANSI 87G, 87M) for DIN rail mounting. If the CT's approach saturation during the transient, then small deviations of magnetic and burden parameters can cause bigger differences on CT output. 1. Have all had been extensively serviced and/or repaired, too much too list prior too a trip too this years burning man. The action you just performed triggered the security solution. Looks like an internal fault involving phase B and subsequently, phase C. Not that fastare there waveform captures? The generator differential trip lock-out (86G) is a device that can be tripped by MANY different devices (or just one, if it is a multi-function digital protection "relay"). Close this window and log in. Figure 3 shows the filtered currents flowing through the generator, i.e., the 60-Hz fundamental component for each current waveform. Relay type DGP of GE-Multilin for example. The currents shown (Ia gen, Ib gen and Ic gen) are measured on the neutral side of the generator stator winding, which is the current flowing through the generator. The 440 cu. This relay is not sensitive for single line to earth faults as the earth fault current is limited due to the high neutral earthing resistance. Cloudflare Ray ID: 7669d6fc9ddbb92d After threats of development in the 1960s, Point Reyes National Seashore was created to protect 71,000 acres of the most diverse, scenic ecosystems in the Bay Area. Login. . Table 1 shows the sequence of the event report (SER) captured by the main relay. Add all the currents and get to zero works for any number. So, from the table above, we can determine that the generator transformer LV side is designed to operate near its knee-point on the magnetisation curve. Thank you for helping keep Eng-Tips Forums free from inappropriate posts.The Eng-Tips staff will check this out and take appropriate action. Then, turn on KW load switches until you reach the desired load. An overcurrent relay 51N or a differential relay 87G gives the protection for each generator. Was this a one-time event or something that happens repeatedly? This ramp will usually have a much larger angle with a smaller viewing surface (ie: 45). TCP,FLD= Control Oil Pressure Low =8 Kg/Cm.Square in case of25Kg/Cm square System 6. 2. The following faults are . Note that the trip output contact asserts the first time the protection operated since there is no intentional time delay. If they both break, you either have a poor output in the Generator or an overload. I'm guessing that Phase C tripped and that the relay is set up to inhibit only individual phases when 2nd harmonic exceeds the setting. The protection system that initiates generator false trip-ping is the generator differential protection. 87= Generator Differential Trip =5% of FLC with max200 miliseconds delay or less. "@$. "kH@1H O/@ 1 Core Balance Type ISO mode, using PMS to achieve constant speed operation mode of the generator. 1. OP should provide more info: relay specs, specific element tripping, and probably more. Review of these waveforms reveals that the current magnitude is close to nominal, and the currents are all balanced approximately 120 degrees apart. In this case, the magnetising current had to be above 100A primary per phase to cause the differential protection to operate. The sensitivity usually can be set to between 5-10% of the full load current of the generator, while the operation is instantaneous and trips the excitation, generator CB and also the turbine. The purpose of this is to prevent the generator from being overloaded or being reversed to cause a trip when the load rate of the generator set is suddenly high and low. Normally reverse power setting is kept less than 50% of the motoring power. Generator Protection - Setting Calculations CT's are of C800 Standard quality 87G - Generator Differential 35. . The hydroelectric generating company had two windings on the low-side of each of the step-up transformers at this plant with two generators connected to each low-side winding. Generator Differential Protection (ANSI 87G, 87M) for DIN rail mounting. It shall also be noted that reverse power protection is provided with a time delay of around 5 s to prevent spurious operation due to disturbances or . 947 0 obj <> endobj endstream endobj startxref 3 Main causes of false differential current in transformer Differential power transformer protection scheme Can't get a clear picture with just limited data. The problem occurs when we energize one 100 MVA transformer at no load. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. 8) Reverse Power Trip Reverse power happens when the generator becomes a motor. There are three styles of motor differential protection. Thanks. If your generator trips, or kicks the breaker off, you can test the plugin by using a different plugin. Block Differential protection trip during a load rejection test On this occasion the generator connects to the system via a step-up generator transformer. In the above fault conditions, differential relay should not trip. The turbine speed controller and the AVR can then be adjusted to avoid such trips during load rejection situations.During such an overvoltage situation, we experienced a block differential protection operation. In power engineering, a single-line diagram (SLD), also sometimes called one-line diagram, is a symbolic representation of a three-phase electric power system.The one. The relay is generally connected to trip the main generator breaker(s . I will shut up now since as I said my memory of differentials is faded and David and others can contribute much more. This is responsible for tripping the circuit breaker of the generator. The latter effect causes an increase in the iron loss and a disproportionately great increase in magnetising current (PRAG 87, p.279). Let's back up. By joining you are opting in to receive e-mail. at the generator terminals or on the external connections. Capacitive Currents in Unearthed HV Systems. Information Notice No. Setting Calculations BFI Output Initiate - Output contacts within M-3425A that trip generator breaker. It starts drawing power from the power system of the ship. Copyright 1998-2022 engineering.com, Inc. All rights reserved.Unauthorized reproduction or linking forbidden without expressed written permission. Please let us know here why this post is inappropriate. The characteristic of all cases was that the currents were present only in two out of three phases at any time, varying from one fault to the other. The operation of the differential protection depends on the differential current as well as the relay characteristics and settings. The reported trips were surprising, but the generator relay fault records verified differential currents measured on different occasions. An offshore platform started experiencing sporadic generator differential protection trips during the start-up of a newly commissioned, large water-injection pump (WIP) motor rated at 4,100 kW. A large steam turbine generator tripped on 87 phase differential protection while attempting to synch the machine to the grid. Have all receipts/records about $7-8k worth labor/parts, very reliable and dependable. This gets feeds from other generators protective devices and will trip the breaker in case there is a problem with generator. Differential current Certain phenomena can cause a substantial differential current to flow, when there is no fault, and these differential currents are generally sufficient to cause a percentage differential relay to trip. The voltage overshoot recorded during the load rejection reached a value between 118-120%, which explains this sudden current increase.Solution to the problem was to increase the AVR response in order to prevent the excessive voltage overshoot. Registration on or use of this site constitutes acceptance of our Privacy Policy. Please include what you were doing when this page came up and the Cloudflare Ray ID found at the bottom of this page. Options: Engine: WHEELS: 17 X 7.5 TECH SILVER ALUMINUM (STD) TIRES: 245/75R17 ALL SEASON (STD) CONVENIENCE GROUP -inc: Universal Garage Door Opener MOPAR BLACK TUBULAR SIDE STEPS ENGINE: 3.6L V6 24V VVT ETORQUE UPG I -inc: 600 Amp Maintenance Free Battery 48V Belt Starter Generator GVWR: 5 050 lbs Delete Alternator GVWR: 5 050 LBS MOPAR BLACK FUEL FILLER DOOR HERITAGE TAN/BLACK CLOTH LOW-BACK . The motor is directly connected to the 10kV local busbar, where a generator of smaller size is also connected. But thanks for explaining Kirchoff's law. Easy to use Generator Differential Protection Relay. For a fault outside the protected area, the through fault current can be high, but correct operation of the differential means that it should not operate on such occasions. The reason they cite is related to saturation of the CT's. Already a member? The relay can detect faults between stator windings, stator earth faults, ground faults and faults between phases outside the generator but within the protected zone, e.g. . There is no need to change relay settings, and the trip alerted the utility that there was a problem with the sync. Good analysis, David. Note that these signals are unfiltered and reveal the large DC offset present in these currents. The worst case electrically is 180 degrees, while 90 degrees is the worst case mechanically. Overview. Turn the control power switch on.
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