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... resulting from a turn -to- turn fault have low magnitudes and are hard to detect Typically, the fault will have to evolve and affect a good portion of the winding or arc over to other parts of the ... relays provide good protection for turn -to- turn faults 1.4.3 Phase Angle Regulators and Voltage Regulators Protection of phase angle and voltage regulators varies with the construction of the ... connected in wye and solidly grounded Generally there is no breaker installed between the generator and transformer It is common practice to protect the transformer and generator with an overall...

Ngày tải lên: 21/03/2014, 12:08

... anti-motoring protection is more of a prime-mover protection than a generator protection The most obvious means of detecting motoring is to monitor the flow of real power into the generator If ... resistor connected across the secondary winding will limit the current level of a phase -to- ground fault to a few primary amperes The most common and minimum protection against a stator -to- ground ... partially or totally covering the generator zone will also provide backup protection for the stator differential 2.3 Protection Against Stator Winding Ground Fault Protection against stator -to- ground...

Ngày tải lên: 21/03/2014, 12:08

... Voltages Transmission lines will be those lines operating at 138 kV and above, subtransmission lines are 34.5 kV to 138 kV, and distribution lines are below 34.5 kV These are not rigid definitions and ... minimum melt and total clearing curves Minimum melt is the time between initiation of a current large enough to cause the current responsive element to melt and the instant when arcing occurs Total ... systems become more complex and the fault current varies with changes in generation and system configuration, directional overcurrent relays become difficult to apply and to set for all contingencies,...

Ngày tải lên: 21/03/2014, 12:08

... coverage and low bandwidth It is best suited to station -to- station protection and communications to small stations that are hard to access otherwise Company owned microwave is cost effective and reliable ... these objectives are type and topology of the communications network, communications protocols, and media used These factors will in turn effect communication system bandwidth, usually expressed ... to calculate the system condition and derive the parameters in real time Rapid derivation and analysis of these parameters are important to initiate automatic corrective actions fast enough to...

Ngày tải lên: 21/03/2014, 12:08

... ANSI=IEEE Standard C37.90, provides the standard for the Surge Withstand Capability (SWC) to be built into protective relay equipment The standard consists of both an oscillatory and transient ... values occur in both numerator and denominator of Eqs (5.35) and (5.36) The denominator is not constant but varies in time with local minima at points where both the current and the derivative of ... respectively Typically wk and vk are assumed to be independent of each other and uncorrelated from sample to sample If wk and vk have zero means, then it is common to assume that n o E wk wT...

Ngày tải lên: 21/03/2014, 12:08

... ‘‘A’’ and ‘‘B’’ open and the line is deenergized, the bus potential restores to its full value thereby applying full restraint to all impedance relays connected to the bus The line voltage goes to ... oscillations can last up to 400 cycles or more This abnormal voltage is applied to the relays at the instant of reclosure and has been known to cause a breaker (for example, ‘‘A’’) to trip because of ... depicts the performance of good breaker operations (top waveform) Here, both breakers trip in cycles and reclose successfully in 13 cycles The top waveform depicts a slow breaker ‘‘A’’ tripping...

Ngày tải lên: 21/03/2014, 12:08

... voltages, and machine rotor speeds; the voltage variations will actuate both generator and transmission network voltage regulators; the generator speed variations will actuate prime mover governors; and ... in rotor angle through a non-oscillatory or aperiodic mode due to lack of synchronizing torque, or (ii) rotor oscillations of increasing amplitude due to lack of sufficient damping torque In today’s ... continually, and the system adjusts to the changing conditions The system must be able to operate satisfactorily under these conditions and successfully meet the load demand It must also be able to survive...

Ngày tải lên: 21/03/2014, 12:08

... power to the generator Pm1, the electrical output power is Pe (equal to Pm) and the corresponding rotor angle is da As the mechanical power is increased to Pm2, the rotor angle advances to db ... Powerflow: Defines system topology and initial operating state Dynamic data: Includes model types and associated parameters for generators, motors, protections, and other dynamic devices and their controls ... sequence powerflow model, which defines the transmission topology, line reactances, connected loads and generation, and predisturbance voltage profile Generators can be represented with various levels...

Ngày tải lên: 21/03/2014, 12:08

... as steady-state conditions and contributed to a worldwide rush to apply power system stabilizers (PSS) to all generator-voltage regulators as a panacea for all oscillatory ills ß 2006 by Taylor ... Voltage regulators, either continuous or discrete, are commonplace on generator excitation systems, capacitor and reactor banks, tapchanging transformers, and SVCs Modulation controls to enhance ... continually changing load and generation to result in unsatisfactory tie-line power oscillations A small oscillation in each generator that may be insignificant may add up to a tie-line oscillation...

Ngày tải lên: 21/03/2014, 12:08

... disturbance when LTCs restore customer load and further increase reactive demand on generators The period beyond 10 when AGC, phase angle regulators, operators, etc come into play The sequential ... power supplied by generators, synchronous condensers, and static-var compensators and its sensitivity to variations in load bus active and= or reactive power These indices and sensitivities, as ... Jacobians, and their sensitivities with respect to various system parameters Bus voltage profiles and their sensitivity to variations in active and reactive power of the load and generators, or...

Ngày tải lên: 21/03/2014, 12:08

... studies and is limited to the analysis of first swing transients For more details regarding the model, the reader is referred to Anderson and Fouad (1994), Fouad and Vittal (1992), Kundur (1994), and ... approaches related to direct stability methods: Pai (1981), Pai (1989), Fouad and Vittal (1992), Ribbens-Pavella (1971), and Pavella and Murthy (1994) These references provide a thorough and detailed ... reference frame and also in the internode coordinates which is similar to the formulation used by Aylett (1958) Tavora and Smith obtained expressions for the total kinetic energy of the system and the...

Ngày tải lên: 21/03/2014, 12:08

... prime mover torque, and Te is electrical torque related to generator electric power output The generator speed determines the generator rotor angle changes relative to other generators Figure ... the generator This causes electric power and torque to be zero, with accelerating torque equal to Tm (Although generator current is very high for the short circuit, the power factor, and active ... loads and the generator (or wo ∫ • dt ∫ dt − 2H group of generators) will accelerate, with Pe − increase in generator speed and angle If D the acceleration relative to other generators is too great,...

Ngày tải lên: 21/03/2014, 12:08

... circuit, and Ll represent the resistance and leakage inductance of the generator stator, Lad and Laq represent the mutual inductance between stator and rotor, and the remaining elements represent rotor ... the stored energy in the rotor in MW-seconds, normalized to the MVA rating of the generator Typical values are in the range of to 15, depending on the type and size of the turbine generator If ... referred to Kundur (1994) and the other references cited below 13.2 Generator Modeling The model of a generator consists of two parts: the acceleration equations of the turbine-generator rotor and...

Ngày tải lên: 21/03/2014, 12:08

... time- and frequency-domain tools to highlight critical aspects of system behavior Automatic detection of unusual conditions or activity, producing operator alerts and cross-trigger commands to secondary ... monitor that automatically erases the oldest file and stores the newest file will meet this criterion if the buffer area is 10 days or more If the monitor requires an operator to remove old data to ... monitor stores continuous data, it does not have to store events The monitor demonstrates synchronization to universal time coordinated (UTC) to a 100 ms level or better Synchronization to GPS-based...

Ngày tải lên: 21/03/2014, 12:08

... type of control must be fast and guided by predefined automatic remedial schemes Restorative control is the action taken to return the system from the restorative state to the normal state This type ... Microseconds to milliseconds Microseconds to tenths of seconds Milliseconds to seconds Hundredths of seconds to tens of seconds Tenths of seconds to hundreds of seconds Seconds to thousands of seconds ... generators have experienced multiple swings Deciding when to stop a simulation and declare the result either stable or unstable remains a challenge in DSA analysis 15.7 Modeling In order to perform...

Ngày tải lên: 21/03/2014, 12:08

... armature is phased to produce a rotor torque that reinforces the initial rotor torque at frequency fn If the resultant torque exceeds the inherent damping torque of the turbine-generator for mode n, ... (TCSC) is a capacitor in series with the transmission line, with a thyristor pair and small reactor in parallel with the capacitor It can function as a series capacitor if the thyristors are blocked, ... generator excitation system, power system configuration, and other factors The minimum and simplest tests are those used to identify the natural torsional frequencies of a turbine-generator Tests to...

Ngày tải lên: 21/03/2014, 12:08

... before operators can respond The goal is to maximize safety, minimize damage, and continue to supply load with the least inconvenience to customers Data acquisition provides operators and computer ... rates and it may be necessary to move the faster generators more to obtain an acceptable response The UCEs are then sent to the various units under control and the generating units monitored to ... penalty factors The penalty factor for each generator is a reflection of the sensitivity of that generator to system losses, and these sensitivities can be obtained from the transmission loss factors...

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... through the forces of supply and demand Economic theory and common sense tell us that if the total supply is high and the demand is low, the price is likely to be low, and vice versa If the price ... LLC 18.1.3 EDC and System Limitations A complex network of transmission and distribution lines and equipment are required to move the electric energy from the generating units to the consumer ... provide power system operators an estimated amount of power demanded The UC objective is to minimize the total operational costs subject to meeting all of this demand (and other constraints they...

Ngày tải lên: 21/03/2014, 12:08

... i and bus j, gij and bij are the conductance and susceptance of line i-j, respectively, and gish and bish are the shunt conductance and susceptance at bus i, respectively Using Eqs (19.4) and ... estimator 19.2.1 Network Topology Assessment Before the state estimator is executed in realtime, the topology of the network is determined This is accomplished by a system or network configurator ... system and the network topology assessment applications and stores the state of the system in a central location (i.e., database) Power system applications, such as contingency analysis and optimal...

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... shunt capacitors and reactors are switched on or off to correct voltage profiles and to reduce active power transmission losses, and phase shifters are used to regulate the MW flows of transmission ... specified power demand occurs), the practically observed version of the standard OPF solution will have a higher total power demand, and hence a higher fuel cost, and total revenue, and net revenue ... leading to multiple OPF solutions) due to two considerations The first is due to use of discontinuous techniques to model specific operating practices and preferences, and the second is due to modeling...

Ngày tải lên: 21/03/2014, 12:08