GRADUATE PROJECT

Presented to

LOS ANDES UNIVERSITYSCHOOL OF ENGINEERING

DEPARTMENT OF ELECTRICAL AND ELECTRONICENGINEERING

Project submitted for the degree of

ELECTRIC ENGINEER

by

Carlos Alberto Nino Ramırez

Development of Methodology for Programming and Testing ProtectionDevices Using Computer Models and the Relay Eaton EMR-3000

Thesis submitted on December 6, 2019, to:

- Advisor: Gustavo Ramos Lopez PhD, Assistent Professor, Los Andes University

- Juror: David Celeita

To all of you...

AcknowledgmentsSpecial acknowledgments to my assessor Gustavo Ramos, for his patience and faith in this project,who help me get to the next step whenever i was stuck. Also to Juan Pablo Holguin and Juan RamonCamarillo for their excitement with the project, and for helping me and teaching me how to use thelab equipment. Finally I would like to express my gratitude to my family and close friends for theirunconditional support in this journey.

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Contents

1 Introduction 11.1 Scope And Final Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2.1 General Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.2 Specific Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 Teorical Framework 22.1 Induction Motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.2 Short Circuit equivalent and Fault Currents . . . . . . . . . . . . . . . . . . . . . . . . . 22.3 Over Current Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3 Methodology 53.1 General methodology and procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53.2 Computer Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53.3 Etap and ATPDraw Model Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.3.1 System Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.4 Relay programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.5 Validation Procedure: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.6 Standards And Normatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4 Simulation and testing results 104.1 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104.2 Programming and Validation results: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5 Conclusions and further work 16

Bibliography 16

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List of Figures

2.1 Circuit Model for Induction Motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.2 Ansi Extremely Inverse Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3.1 Methodology Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53.2 ATP Model Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63.3 TCC Curve use to setup protection functions . . . . . . . . . . . . . . . . . . . . . . . . 83.4 Wiring diagram of the montage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.1 One phase fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104.2 Two phase fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114.3 Three Phase Fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.4 Locked Rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.5 Cold Start Recorded by Relay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.6 51P[1] Pickup for 3Phase Fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.7 Asymmetrical Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

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List of Tables

3.1 Etap 19 Motor Model Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.2 Load Flow and Short Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.3 Relay System Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.1 Protection Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114.2 Protection Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

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1. IntroductionIndustrial power systems are a very important of the grid because of the portion of the total demandthey represent. similarly, in terms of the electric industry, industrial power systems are one of the mostrepresentative clients of electric machines, conductors and protective systems. This presence in all ofthis areas of the industry, makes the industrial consumer one the employers with higher demand forelectric engineers. For this reason, all reputable electric engineering schools have a strong research inindustrial power systems. This tendency, highlights the importance of investigating in this field, butnot only in order to get new knowledge, but also to improve the teaching of engineering on this areas.

With this in mind, this project presents the development of a methodology for programming and testingprotective relays in a lab environment, using simulations as a main tool to emulate real scenarios in alab. additionally this project has the objective of facilitating the comprehension of protective systemsfor industrial applications. Attempting to bring new tools for the teaching of protection devices andalso providing a small contribution to the overall protection systems research in the university.

1.1 Scope And Final Products

As final products, this project aims to deliver a methodology to simulate different operative conditionsthat are consistent with the protection capabilities of a relay, configuring such relay using the infor-mation obtained from simulation and the theory behind it, and at last a validation strategy where thedifferent functions that were programmed before can be tested in order to understand the behavior ofthe device and the considerations one must have in order to use program it effectively. All of this willbe done using the Eaton EMR-300 as a testing platform for the methodology and also as an exampleof it.

1.2 Objectives

1.2.1 General Objective

Develop a methodology to program and test relays in a lab environment, using simulation as a referenceto program and test, and the Eaton EMR-3000 as a testing platform.

1.2.2 Specific Objectives

• Design a power system montage in ATPDraw that allow us to simulate different operative con-ditions and obtain COMTRADE files from them.

• Program the protection functions on the Eaton EMR-3000 using the information from the sim-ulation done before.

• Test the parameters using injections test where the correct operation of the functions is evaluated.

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2.Teorical Framework

2.1 Induction Motor

The induction motor is an electric machine that uses the electromagnetic principles to transform electricenergy into mechanical one, or more specifically, it transforms electrical power into mechanical torque.To achieve this the motor consist of two main parts, the stator and the rotor, the stator refers to theelectric side that is attach to chassis of the machine an the rotor is the electric side that is attach tothe shaft. The principle of operation is that the electromagnetic field generated in by a current in thestator induces a current in the rotor which flows in the opposite direction, this new current generatesother electromagnetic field. Due to the directions of both fields an electromotive force is generated, asthe shaft is the only mobile part it rotates generating a mechanic torque. As the rotor and the statorare not connected electrically the model circuit model for the induction motor is similar to the modelof a transformer, with a leak impedance to estimate the air losses and other impedance to estimatethe losses of the copper. The model can be seen in the figure 2.1As can be seen, the impedance of the load is estimated using a variable resistance which value dependson the slip of the motor. The slip is defined as:

ηSlip = ηSync − ηm (2.1)

s =ηSlipηSync

(2.2)

In relation between the electromagnetic field and the rotor. This means that the rotor speed is neverthe same as the electromagnetic field’s. This is why they are called asynchronous machines, and isa characteristic of these kind of motors that establishes a relation between the load and the circuitmodel, because if one knows the relation between the load and the mechanical speed, the magnitudeof the load impedance can be calculated to perform electric calculations using the circuit model.

As can be noted, most of the load is generated by inductances, so a transient response must be ex-pected, in this case there is a peak in the current where the magnitude is very significant due to theX/R ratio of the motor. Usually in a motor the peak transient current is between five and seven timesthe steady state current. For that reason, the motor start is one of the most important operationstates of the system because and should be considered in the protection scheme[3].

i(t) =V max

Z[Sin(ωt+ α− θ)e

−RtL ] (2.3)

2.2 Short Circuit equivalent and Fault Currents

During a fault scenario, the current is given by the generators or the short circuit capacity of thesystem, since usually the generators separated from the demand, its very common to modelate a short

Figure 2.1: Circuit Model for Induction Motor

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CHAPTER 2. TEORICAL FRAMEWORK 3

circuit equivalent with a determined short circuit capacity, which is the power the system can provideduring a short circuit scenario. A circuit equivalent of this element is given by a Voltage source and aseries RL impedance, these impedance can be calculated using the following expressions[2]:

X1 =2VLL

MVA3φ(2.4)

X0 =3KV 2

LL

MVA1φ− 2KVLLMVA3φ

(2.5)

This calculation is valid for the steady state current, but in the transient of the fault, there will be anasymmetrical current with an AC and a DC component, the instantaneus value of this current can becalculated using the expression 4.7. As can be seen this component depends on the part of the cycleon which the fault hits and the X/R ratio of the system, in this case, the short circuit equivalent.

2.3 Over Current Protection

Over Current protection consist on a series of comparators, that take the current phasor and compareits magnitud to a reference that can be a unique value or a nonlinear expression. The most relevantfunctions in the ANSI devices numbers are the 50 and the 51, where the 50 is instantaneous, so itoperates by comparing the current magnitude with a constant current threshold. The 51 comparesthe measurement with a time inverse curve, there are multiple curves within the ANSI standard, theexpression or the extremely inverse curve is the next one[6]:

top = (t−mul)28.2

(If

Ipickup)2 − 1

+ 0.1217 (2.6)

As can be seen, the shape of the curve can be modified by changing the value of the t-multiplier orthe pick up current, the t-multipler changes the slope of the curve and with this, the time delay ofthe function, while the pickup current determines the threshold from where the function will begin toactuate. A graph of the function curve can be seen in the figure 2.2[4] The expression show in equation2.6 is valid for pickup values greater than 1, whereas for pickup values smaller than 1 the curve behavioris different, and its known as the reset state, which emulates the behavior of a mechanical relay. Inthis case the reset times of the functions will be set to zero, so the behavior described for Pickup ¡ 1will not be seen.

CHAPTER 2. TEORICAL FRAMEWORK 4

Figure 2.2: Ansi Extremely Inverse Curve

3.Methodology

3.1 General methodology and procedure

As mentioned earlier, the main goal of this work is to develop a methodology that allows us to determinethe settings for the protective relay, and validate those in a lab environment. In order to achieve thisgoal we defined three main stages: First, is the development of a computer model that allows usto simulate and obtain accurate waveforms for different operative and fault scenarios to get a set ofparameters and restrictions that the protective relay must fulfill.In second place, is the recognition of the features and protective capabilities of the relay that we aregoing to be using. This stage has the objective of defining the conditions where the relay is design totrip or not. Once the capabilities and scenarios are defined, the next step is the programming of thesettings in the relay, and the coordination of the protection functions. Once these is done, the correctoperation of the relay must be validated.The last stage consists in the validation of the programming of the relay using the simulation dataobtained in the first stage. The main objective of these part is to establish a procedure of signalgeneration and amplification so they can be process by the relay as if they were from the secondaryside of a current transformer.These stages aren’t sequential, this is due to the dependency between multiple aspects of them. Oneexample clear example are the first and second stages, where the electrical parameters of the simulationare highly dependent on the relay intended application and capabilities. A diagram of the methodologyis shown in the ??

3.2 Computer Model

As the purpose of this stage is to find a model that allows us to generate waveforms, is necessary todefine the restrictions to be fulfilled in order to get a useful model for the purpose mentioned before,the main aspects to consider for this are the relay main application and functions, and the equipmentavailable to validate the configuration. Since the relay to be use is an overcurrent relay, most of thescenarios to be simulated are fault and overload conditions, and since the signal processing platformthat will be used uses the comtrade protocol, the simulation data should be capable of generatingcompatible files. With this in mind, the requirements of the model are the next ones:

• Generate waveforms in comtrade format.

• Simulate 1, 2 and 3 phase faults.

• Simulate locked rotor and overload conditions.

Figure 3.1: Methodology Diagram

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CHAPTER 3. METHODOLOGY 6

Figure 3.2: ATP Model Diagram

• Simulate different start scenarios.

• Being versatile enough to allow testing different motors.

The software chosen to achieve this was ATPDraw, because of its time domain simulation capabilities,the compatibility with the Comtrade protocol and the included induction motor models that allowmanufacturer’s data input, this was important because it allows the testing of realistic scenarios withease.Once the software was chosen, the topology of the system was the next step, a basic configuration wasadopted, with a short circuit equivalent, a connection cable, a current transformer, a fault setup andthe induction machine.The short circuit equivalent was design for a low voltage network with a 3 phase short circuit capacityof 10MVA and 8MVA for the mono phase case, the impedances were calculated using the expressions2.4 and 2.5.The electric parameters for the induction machine were taken from an catalog for induction motorsfrom the company TECO[7], the parameters are shown in the tableOnce the model complete, we proceeded to simulate 6 different scenarios, start, locked rotor, overloadand mono, bi and three phase faults. The results were validated with the theoretical values calculatedfor steady state magnitude and asymmetrical current in transient state, using the expressions showbeneath. The simulated waveforms are shown in the figures4.1, 4.2,4.3 and 4.4

CHAPTER 3. METHODOLOGY 7

Table 3.1: Etap 19 Motor Model ParametersParameter ValueVoltage 480VPower 382WPF 0.87Efficiency Sec 0.95Slip 0.025LRC 7PU

Table 3.2: Load Flow and Short CircuitParameter ValueVoltage 480VFLA 301Aone-Phase Short circuit 9.27KATwo Phase Short Circuit 10.14KAThree-Phase Short Circit 12.46KAAsymetrical RMS current 17KA

3.3 Etap and ATPDraw Model Comparison

The Etap 19 model was made using the same topology of the one in ATPDraw, a 480V short circuitequivalent, a 30 meter cable, and a 382HP induction machine, with the difference that on this model,an Overcurrent relay model was used, with the objective of using the protection coordination toolsincluded on the Etap 19 software. Since the software has a built-in model for the Eaton EMR-3000 thatincludes all of the protection functions and configurations. In order to validate the use of this softwareto determine the settings of the relay, three elements were compared, the motor electric characteristics,the load flow and the short circuit analysis.

3.3.1 System Parameters

The electric parameters of the motor were obtained based on a motor catalog [7] and the librariesincluded in the software. This parameters can be seen in the table 3.1Now, the short circuit and FLA currents were obtain by performing load flow and circuit analisys,using the ANSI standard for the short circuit and computing the asymmetrical currents. Which givesthe results presented in the table 3.2

3.4 Relay programming

As the main goal of this section was to program the settings of the relay and its protection functions,the procedure on this stage consisted in the definition of the current transformer(CT) ratio, the desiredCT input (5 or 1A), the Full Load Amperage (FLA) of the motor and the wire configuration of theCT connection(with or without ground CT). One important consideration on this section, is that theCT ratio was configured considering the IEEE 242 recommendation of setting the ration between 100and 125% of the FLA. The system parameters are shown in the 3.3The protection parameters were adjusted for the overcurrent functions 50 and 51, in its Phase, residual,Jam-Stall versions. As the relay incorporates 3 different 50P and 51P one was used to protect theoverload condition. The justment of the settings was done using the software ETAP with an equivalentsystem and motor from the ETAP 19.0 libraries, TCC curves were used to select the settings in order

CHAPTER 3. METHODOLOGY 8

Table 3.3: Relay System ParametersParameter ValuePhaseSec ABCFrecuency 60CT Primary 400CT Sec 1FLA 390CT Config 3-Wire

Figure 3.3: TCC Curve use to setup protection functions

to protect the device in fault condition and avoid false pickup of the functions in start condition; oneexample of these curves is shown in the Figure 3.3The criteria used in the overcurrent protection is to program the instantaneous functions (50) tooperate on the worst case scenario, which is the highest asymmetrical current caused by the faulthitting on the peak of the cycle. And the inverse time curves (51) to operate on the steady statecurrent under the curve of thermal damage of the motor. This way we ensure that the protection istriggered before the fault current can generate any significant damage to the motor.As for the overload and Jam protection, the criteria used was based on the manufacturers data, whichfor this case recognized and overload situation when the load torque its at 1.6PU for a period longerthan 15 seconds, and when the locked rotor current was maintained for more than 8 seconds. Basedon this data, one 51 moderately inverse protection curves was program to trip under this overloadconditions.

3.5 Validation Procedure:

The validation process was divided in two stages, injection and parameter validation. The injectionstage consists in processing the digital signal generated by the simulation software to generate a low

CHAPTER 3. METHODOLOGY 9

power signal, and then amplifying this signal in order to emulate the secondary of a current transformerconnected to the relay. The validation process consist on recording the pickup and tripping of thefunctions and comparing the tripping times to the expected on the protection curves. Additionally,the idea was verify that the relay is coordinated so the function that trips corresponds to the simulationthat its being injected.In order to achieve this, two systems were used, the NI-cRio 9082 for the signal processing and genera-tion, and the Omicron CMS-356 as the signal amplifier. The NI-cRio uses the LabView VI designed inthe Power and Energy lab at Universidad de los Andes, which processes the signal in comtrade format,converts it to a voltage signal and scales it depending on the peak of the signal and an scaling factorin order to match the output range of the system. The other system used was the Omicron CMS-356which is a voltage and current amplifier that acts as power stage for the NI-cRio, by delivering a threephase current of up to 64A on each phase. The general connection of this setup can be seen on thediagram of the figure.

Figure 3.4: Wiring diagram of the montage

As for the validation process, the main tools used were the relay software, Eaton Power Port-E andits complement Quality manager. This tools were used configure the relay waveform recorder to storerecordings of function trips and motor starts, and to visualize the measurement of fault currents andtripping times of the functions. The measured times were compared with the theoretical curves usingETAP 19. Other aspect to validate was the coordination of the functions within the relay, in orderto achieve this, COMTRADE from different scenarios were injected an the function that tripped wasidentified and compared with the programming. For example, in a locked rotor scenario was expectedto see the tripping of the 51P[2] function, and not the 51R[1] or the 51P[1], since these two wereintended to operate in a single or two phase fault scenarios.

3.6 Standards And Normatives

As mentioned earlier, there were used some IEEE standards to design the simulation system and definesome protection parameters. These standards are the IEEE 242[6] which gives some general consid-erations and recommended practices to perform Overcurrent protection in industrial power systems,which is the case given the Relay used and the type of system. Additionally, there was used the IEEEPC37.96[1] which gives some protection recommended practices for motor protection, it was speciallyuseful to understand the general protection strategy for electric motors.

4.Simulation and testing results

4.1 Simulation Results

As mentioned earlier the main objective of the ATPDraw model, was to generate simulation filesof operative scenarios that were useful for programming and testing the relay, the start, fault, andoverload simulation graphs are shown in the figures 4.2, 4.1, 4.3 and 4.4

(a) Phase A (b) Phase B

(c) Phase C

Figure 4.1: One phase fault

This waveforms were obtained from the secondary of the Current Transformer simulated configured at1A. As can be seen the, there is a noticeable asymmetrical current, which is caused by the X/R ratioof the short circuit equivalent, this was used to test the instantaneous overcurrent functions (50[P])and the coordination with the other overcurrent curves (51), additionally all of the scenarios weresimulated using a cold start for motor, which isn’t very accurate in a real life application, but helps usto validate that none on the protection functions is tripping incorrectly.

4.2 Programming and Validation results:

The parameters of the protection functions were defined considering the coordination and trippingcriteria mentioned before, all the protection parameters programmed on the relay can be seen on table

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CHAPTER 4. SIMULATION AND TESTING RESULTS 11

(a) Phases BC (b) Phases AB

(c) Phases AC

Figure 4.2: Two phase fault

4.1.The 51P[1] and 51R[1] are ANSI Extremely Inverse Curves while the 51[2] is the ANSI Moderatelyinverse curve used to protect in case of an overload or a locked rotor event. Other consideration tohave is the additional functions that the relay may have. For example, the relay we are using has amaximum amount of cold starts allowed before tripping and also a minimum time between cold starts,in this case those functions were disable, other functionalities to have into account are the CircuitBreaker failure monitor and the CT failure monitor.

Regarding the differences in measured values and simulated ones, in table4.2 can be seen the percentageof error between those values for peak currents referred to the primary of the CT, in case of the faults,the values correspond to steady state current. As can be seen the maximum error is around 5% anddecreases non linearly as the current grows. This error can be attributed to multiple elements in the

Table 4.1: Protection ParametersFunction PickUp t-multiplier/Delay50P[1] 23.81 0.0150R[1] 20 0.0151P[1] 1.48 3.6651P[2] 1.4 2.750J[1] 1.6 7

CHAPTER 4. SIMULATION AND TESTING RESULTS 12

Figure 4.3: Three Phase Fault

Table 4.2: Protection ParametersScenario Measured(KA rms) Simulated(KA rms) Difference(%)FLA 0.42 0.4 4.7Start 2.68 2.8 4.2One Phase Fault 9.36 9.27 0.97Two Phase Fault 10.03 10.14 1.08Three Phase Fault 12.29 12.26 0.24

chain of measurement, but is most likely associated to the scaling of the COMTRADE file into ananalog signal, because this is the stage where the signal data is modified directly.Once the simulations were injected in the relay the tripping times were extracted from the device usingthe Eaton software, the correct functioning of the functions was validated. Some of the recordings canbe seen in the Figures 4.5 and 4.6

As an be seen in figure 4.5, a cold start recorded by the relay in RMS, there is not pickup from anyprotection function, this is because the speed was zero, so the start detection function assumes is astart scenario, and since both the current and the time are below the established threshold, it blocksthe overload functions.

As for the case of a three phase fault with an impedance of 25 Ω 4.6. The 51[1] function picks up,since the magnitude of the fault significantly smaller than a solid fault, this scenario was simulatedto see the behavior of the protection scheme under a higher impedance fault. As can be seen, thefunction trips at around 0.014 seconds (almost a full cycle) after the fault hits, which is consistentwith the curve, since the RMS current is approximately 3.16KA which is very only 35 percent of theshort circuit capacity.

As for the asymmetrical faults4.7, can be appreciated that the instantaneous function trips on highlyasymmetrical faults where the short circuit current is greater than 16 KA RMS, only after 1/4 of acycle, presumably because of the specifications of the PMU of the relay.

CHAPTER 4. SIMULATION AND TESTING RESULTS 13

Figure 4.4: Locked Rotor

Figure 4.5: Cold Start Recorded by Relay

CHAPTER 4. SIMULATION AND TESTING RESULTS 14

Figure 4.6: 51P[1] Pickup for 3Phase Fault

CHAPTER 4. SIMULATION AND TESTING RESULTS 15

](a)51[P

](b)50[P

](c)51[R

Figure 4.7: Asymmetrical Faults

5.Conclusions and further workIn conclusion it was developed a methodology to program and test relays using computer models andtime domain simulations, and injection equipment in a lab environment. The general result of thisproject is the organized procedure of that methodology that can be summarized in three stages: Es-tablishing what is he desired protection device or system that will be configure and tested, Identifyingthe available equipment to perform this task, defining which features of the system will be configuredand tested, design a computer model consistent with the application of the protection device and theavailable testing resources, configuring all the necessary settings of the devices involve, and at lasttesting the configuration with a theoretical reference(Expected performance, times, coordination, etc).

This methodology can be really useful if one wants to develop protection systems tests, or it can be usedas a learning tool for engineering students interested in protection analysis, because of the practicalpart of the procedure, that would allow students to test their ideas about protection parametrizationand coordination, in a safe environment.

As for future works, one very interesting approach would be the connection to other relays, in orderto test selectivity and protection coordination in situations there the protection logic might not be sosimple, such us systems with distributed generation. Additionally this methodology could be usefulin the Power and Energy lab at Universidad de Los Andes, if put together with the Gidteractionssimulated network developed there.

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Bibliography[1] IEEE Draft Guide for AC Motor Protection, 2012.

[2] P. M. Anderson. Analysis of Faulted Power Systems. 2010.

[3] S. J. Chapman. Electric Machinery Fundamentals. 2010.

[4] I. Manual. EMR-3000 EATON MOTOR RELAY.

[5] Omicron. Cms 356. pages 4–5, 2016.

[6] P. Systems. I e e e book TM 242 TM. 2001.

[7] TECO. Standard Motor Catalogue. pages 1–28, 2014.

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