Development of a Digital Motor Universal Management Relay
Contents
1. me intervals o the disturbance The proposed environment simulates a microprocessor based relay designed for the protection and management of medium and large sized motors Overvoliage and undervoltage protection thermal overload fault diagnosties ae provided It provides phase neutral ground and negative sequence instantaneous and time overcurrent protection The me overeuent fonction provides multiple curve shapes or optimum co ordination The relay also features an enhanced Thermal Model with custom curves current unbalance biasing and running and Stopped exponential cooling curves An optional RTD module allows for the Thermal Model RTD Bias function Motor start and supervision functions include Starts Per Hour Time Between Starts Restart Time Acceleration Time Emergency Resan and San Inhibit Sensitive Directional Power Mechanical Jam and Current Unbalane elements are also Included ss standard funetions Voltage curent and power metering is considered Current parameters are available as oul waveform RMS magnitude or as fundamental frequency only RMS magnitude and angle phasor is worth saying that the main objective in the design of this work is the simulation of an actual relay for design and implementation purposes Teaching the fundamentals of protective relaying was not the major goal This issue has been done in other papers 10 The paper is organized as follows Seton I gives a short d2. Development of a Digital Motor Universal Management Relay Simulator Mojtaba Khederzadeh and Hossein Ansar Sharezai protective relay desi protective devices a wel at contral monitoring communication be dened and evaluated n ih mt omer Spee Blot repo by Environment MATLAB iPower tn 1 mondeo ROTECTIVE relay design and implementation is a Sophisticated task chat requires both hardware and software considerations The algorithms should be developed based on the hardware capabilities IF the computation requirements are not fulfilled by the selected processors the hardware design needs to be reevaluated The common practic is the design and implementation ofa prototype based on mhe preliminary evaluation of the computational requirements of the protection contol monitoring scllography and communication tasks Hence there is a nezd for a simulation tool which could simulate the relay both fom hardware and software point of view RAN Ghom NADERE ta vS eam Modes Different approaches to modeling protective relays and elated power system events have been discussed in 1 Well Known Software packages can be used to simulate power system faults in both the time domain electromagnetic transients 2 3 4 and phasor unbalanced steady state 6 TI modes Some of the packages have the provision for incorporating protective relay models developed by the user 12 3 while the others have the gener
3. ad withthe motor initially at 0846 per unit of thermal capacity The cyelie current in Figure 11 alternates between 1 4 and 0 4 per unit current every 10 minutes Note that the verge of the euents squared and the rms curen is 1103 pu The cyclic curent is not an overload that raises the temperature to the tip Value Figure 9 shows the cycle temperature response of the themal model reaches a 1 06 average or 30 percent of the wip value The overcurrent relay model does not measure temperature and nips becuse it cannot account for thermal history B Diferential Relay Operation Fig 10 shows the simulation of differential relay operation The power system consists of a phase source cable manent wansformers breakers and related measuring 1 ee B V Caxetusion Im his paper a novel modeling and simulation environment s developed that could serve as an aid 1o relay designers and manufacturers to evaluate their protective algorithns and hardware structures Diferent motor protective devices can be emabieidisabled by the user AN the protective devices are collected and optimized in one unique station that emulates he actual relay The relay operates in a dynamic manner and its satus is visible on the sereen Advanced protective algorithms Tike thermal overload could be best tested and debugged by the developed environment It allows evaluation fof both individual relays as well as the interactions among cl
4. ation In order to closely emulate the actual rely a user friendly model with different capabilities has been designed Fig 3 shows the relay in the Simulink modeling page The status indicates normal operation or wipped condition Trip type indicates the prorecive device function and number for example Excessive starting time locked rotor 48 SILR Trip date and time is for data logging and indicates the date and time of the event The last line is for the simulation time staring fom the beginning up to the relay trip Since the user determines the instant of fault this vala shows the relay tip Time tam the inocption of fault 10 the issue of the wip command The basie blocks protective devies have bes developed as masked subsystems with fictions performing he requicod operations The icon of the management relay has been used in a dynamic way H reflects he changes during the execution of the program not as emey to the program For example when the undervoltage device 27 operates the relay icon shows the wip type dynamically It uses the GUI programming for data input and output The data entry mechanism ofthe mask has been extensively used to input the block parameters the locked Consequently ary contains both the blocks structures and pre defined default data The help lak of the mask has been used to provide one help n the form of mettet documents ha or vich text format Some blacks file converters for exampl
5. ays incorporated ino a protective relaying system under a Variety of power system operating conditions The sampling interval is adaptively adjusted bythe system frequency The enhanced envitanment allows for the evaluation of the burden of the processing resources In this regard fired interval processing loops can be designed and evaluated The processing of the sample data into operating quantities may not be done every time a new sample data is acquired i could be selected by the user This high processor burden task Would only be done as often as the highest priority tasks are called Rerenesces N PG Maren Menil V Shee A igi AL Sachdev G 1 CAA Ue Gan Aerate Ten Progam ATP le a Pen 19 I NTP Retence Mal BEA Angus 1946 OE User anatase VDE Roce C186 PES LESSE Sannan Klaar Nac ve 43 I ASPEN Uns Mua ASPEN 1098 a Reker ang EA Dl Tee hy Savers rn 20 Us Ga M Kenmovic S Vasilie Advanced Sofware Environment for Evaluating the Protection Performance Using Modeling and Simulation CIGRE SC 34 Colloquium Sibiu Romania September 2001 13 GE Univeral Mae Magnet Relay Ue Manusi 4 al BEE Sunde 3190 Canon Fo ro Dita m 08 Sey EZ Ama Gin Thema Mode in Poner Ed EER ES Er en Fa War ene o Tenn Teln ieee sc
6. e have been developed as MATLAB programs ar Ties The inputs to thi slay are 3 phase currents fram the motor terminals 3 phase voltages 1 input from Core Balance CT Gif availible and 3 phase currents of the neural side of the motor Windings for differential protection By clicking on the relay he senting menu appears Fig 4 This figure shows different protective device functions fr motar The user can enable or disable any device and perform the settings by clicking on the desired icon Since the other power system equipments such as generator transmission line and transformer have common protective devices this software environment could be Extended to cover these equipments Fig 4 also shows the sening menu for thermal overload as an example The wer observes this menu by clicking on the associated icon The relay also delivers the captured data and evens in IEEE Contrade format 13 Pip toting em den rene eve AL Hardware Modeling Fig 5 shows the masked subsystem of the relay This block shows analog multiplexer anti aliasing fiter AD convertor DC offset removing block and processor eh FT Although the general blocks like analog Cler and A D can be built by different methods but the important point is the sampling rate In this regard fired interval processing laps un be designed and evaluated For example the algorithms may be structured such that there is t
7. ermal model used in motor start up Fig 7 indicates the thermal model in running siate 14 The digital equivalent of these models are solved in the software environment based on the motor nominal data As can be seen Hom Figure 4 the sening menu for thermal overload reseives the Service Factor SF Locked Rotor Curent IL Locked Rotor Time From Operating Temperature To Locked Rotor Time From Ambient Temperature Ta and initial condition temperature rise as input data D Brera Stating Time Lacked Rotor Fig 8 shows the block diagram of the device function 4W SILR This mean is ree plase It comprises three pans Excessive starting time during starting the protection picks up when ons af the 3 phase currens is greater than the sel point Is for a longer period of time than the ST time delay normal starting time 4 Locked rotor at the normal operating rate afer staring he protection picks up when one of the 3 phase currents 5 greater than the set poin I Tor a longer period of time than the LT time delay af the definite time ype m pa u ae Suning is detected when the eurent consumed is 10 rete than the hase current or 123 input is activated by a contact fom motor shaft rotation detector The ST time delay Which corresponds to the normal staring time may be Teinslzed by a logic data input for particular uses put na Locked rator at staring stage large motors may have ve
8. escription of a motor management relay with its new features owed to mhe digital technology like thermal overload protection An overview of motor fault evens and normal operating states as well as the selected model of an actual power network are given in section IE Section IV provides insight into the motor management relay modeling and simulation tools Section V defies the new simulation environment for a motor universal management relay design and evaluation The conclusions are given at the end IL Motos MANAGEMENT RELAY SPECICATION Protection monitoring and metering shall be supplied in one integrate digital relay package for application to medium and large horsepower motors suitable for incorporation imo an integrated station contol system A Protection Funetions D Thermal Overload Protection The Thermal Overload element must provide dynamic rotor protection both during acceleration and stall conditions The gorithm shall include these key elements Overload protection using Standard programmable overload curves a Negative sequence current biasing using the negative to positive sequence ratio scaling to include system unbalance bewing effects Sar RTD biasing hoveold compensation with type selection Independent motor cooling tine constants for both running and stopped conditions Restart inhibition to prevent thermal damage during successive starting Inhibit override to allow an Emerge
9. hanced environment for the evaluation of the burden of the processing resources and the efficiency of the protective devices algorithms In the proposed software envionment the relay designer has the feedom to select more processors or optimize the code based on the resl needs of updating the operating quantities The efficiency of the algorithms could be judged easily by simulating the conditions for the operation or the desired protective device This important feature is based on the capability of modeling of the power network and protective relays and their interactive simulation for a variety Of the events in power system These events encompass many scenarios including various fats and normal operating states and correspond to specifie time scales In this paper MATLAB Version 6 5 RI with the enhanced Simulik SimPowerSystems Version 23 9 is Selected as the main engineering tool Tor performing modeling nd simulation of power systems and relays as well as for interfacing the user and simulation programs Asa part of the Physical Modeling family of pres SimPowersystems work together with Simulink to model aste mechanical and contol systems Through one interface the operator is able to select and set models of the appropriate power systems nd relays to interface the relay models to the models of the power system to define power system disturbance scenarios and to initiate various simulations coresponding to specifie
10. he A D interrupt running atthe A D sample rate The processing of the sample data into operaning quantities phasor estimation for example may not be done every time new sample data is acquired This high processor bunden task would only be done as a en as the highest priority tusks ae called The high priority instantaneous np functions and output loge funetions muy be in LK or eyele loop Another grouping of lower priority functions may be processed only every cycle or every other eyele n this simulation the following approaches have been used The sampling rate depends on the system frequency whic changes with time In this simulation the system frequency is measured per rival of one or multiple of new samples Based on the measured frequency the Sampling interval is determined The simulation Benefis Tom the sliding window approach for updating the phasor measurements The user can select the updating period by clicking on the SAMPLING icon in setting menu Fig 4 For 16 samples per eyele the user can select O means updating very eyes to IS means updating every sample B Protective Device Algorithms These algorithms are developed for optimized operation of the relay One of the important ones is thermal modeling This protective device is developed and progressed by the aid the digita technology enables og ty solve differential equations in eskime D Thermal Overload Fig 6 shows the th
11. ic relays models already included 4 8 6 7 In all the mentioned eases itis dificult 10 add mhe modeling and simulation features 10 specifie protective relaying concepts that go beyond the level of derail originally provided by the software Additions of new relay models and implementations of specifie Bul scenarios as well asthe flexibility of changing the way the models of relays and power system interact is constrained by the Spesie user and programming interface rules embedded in the existing Software The relays can be more accurately and more emsiendy modeled by using either C language or a commercial software package with pre defined libraries such ss MATLAB SIMULINK S An embedded system in a digital relay usually consists of one host processor and one or multiple DSPS Ia general there is a finite amount of processing resource available in any given microprocessor design This is a function of the speed and architecture of the processor or processors and the speed oF peripheral items such as memory data bus ete For a given hardware platform the relay designer must decide on the best compromise in allocating this finite processing resource 10 crente a multifunction relay Several of the most important Factors that the relay designer balances in the design of a relay are number of functions needed how often each function is processed and efficiency of the code The salient feature of the proposed software is an en
12. m other elements contact inputs ete The relay shall allow for peer to peer communications direct Tiber or G703 oe RSA22 interfaces Swinchable Sening Groups The melay shall have switchable sening groups for manie reconfiguration of the protection elements due 10 changed conditions such as system configuration changes or seasonal requisements Metering Futons Voliage Currant Power Energy Voltage phasors mue RMS values symmetries components current phasors symmetrical components wie RMS Values real reactive and apparent power power factor energy and frequeney er programmable osellographs Tip dealt monitoring relay includes the The device numbers and functions are according to Table L This is a typical motor universal management relay that can be found commercially 12 Usually he time overeen devices have IEEE Moderately Very Extremely Inverse curves IEC and BS ABC and Short Inverse curves definite time curves and a few user programmable ones O e z Prose Saame Va D Hardware The structure of a mieroprocessor based relay is shown in Fig 2 The parameters of euch module should be carefully selected in order to have an optimized design The important peins in this part are transducers voltage and current wansformers isolation wansformers anti aliasing Bles AD convenors digital inputs a
13. ncy restart D Restrained Stator Differential element The diferential clement shall have a dual slope characteristic A directional check and saturation detection algorithm Stall be included for enhanced performance during CT 3 Current Unbatance protection This element shall use the negative to positive curent component ratio method The element shall adapt to overload conditions The element shall detect singl phasing and wer n o D El 2 El Nomally a allowing protection devices 1 Overcurrent Protection Phase Neutral and Ground Instantaneous Overcument AOC protection shall be provided with a setae time delay Ground Time Overcurrent TOC protection wit IEEE IEC TAC I definite time curves Volage Protection Phase Neus Ausliry and Negative overige protection Phase and Auxiliary undervoltage protection both with definite and inverse time characteristics The volage element operating times shall be wer adjustable Sensitive Directional Power element Two clement shall be included each consisting of two stags The element characteristic angle shall be adjustable ATD monitoring Sequence Control Function Programmable logie including non volarite latches Steen curves for wserdefnable protection functions Flexible conto of all input and output contacts shall be provided Al elements shall have a blocking input that allows Supervision of the element fo
14. nd outputs The sampling rate is a key factor Usually it is between 16 10 64 samples per cycle Sometimes a block is necessary to change the gain of the input signals in different sats These parameters that explicitly relates to hardware can greatly fet he software like the required degrez of digital filtering IIL RELAY SuMLLATION SoPIWARESHRUCTURE In Wis work MATLAB Version 65 R13 with the enhanced Simulink SimPowerSystens Version 23 9 is Selected for simulation ofthe power system and the universal motor management relay MATLAB is seleted far is popularity in the university environment and increasing recognition in power engineering indastiy its exible sofware structure comprising braies models and programs in onder 1o integrate different model components in one package conveniently is time domain solver SIMULINK 10 reste a fienly and open system to add new models and basis is quick and efficient expansion due to the powerful csleulation and visualization means without the necessity 10 develop any extra programming tools is ich and powerful TOOLBOXes and is newly developed SimPowerSssoms previously called Power System Blockset 11 enabling modeling the basic components of power systems while drumusically reducing the computation time It provides computations similar to EMTPIATE permiting modeling of Boh the power system and is coatols in the same environment and thus facilitating closed loop simul
15. ry long starting time due to their inertia or the reduce Voltage supply This starting time is longer dan the permissive mtor blocking time To protect such a motor LTS timer initiate a wip ia start has been detected Is er if tbe mator speed s zero For a normal Mar the input 123 sto sgeed sui disables this protection When the motor re accelerates i consumes a cument in the vicinity of the starting current Cls without the current first passing through a value less than 10 of Ibase This information may be used te Reinitialize the excessive starting time protection Setthe locked rotor protection LT delay to a Jow Value D Phase Overcurrent Phase overcurrent protection is deep It picks up when one nwo ar thre of the phase currents reaches the operation set poin It is time delayed The time delay may be definite DT or IDMT standard inverse SIT very inverse VIT or LTL extremely inverse EIT ulna inverse UIT RI The funtion includes an adjustable reset ime TY DT characteristics timer hold Sie IN INTERACTIVE POWER SYSTEM AND RELAY SIMULATION in te simulation environment different faults can be simulated and the behavior of the relay sould be checked Here only ty cases are invoduced A Thermal Overload Silat In Fig 9 conventional overload overcurrent relay used for overload and thermal overload models we subjected 10 a cyclic overlo
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