COMPUTER INTEGRATED OVERLOAD RELAY TESTING ANDDATA ...€¦ · Keywords Thermal Overload Relay, Automation testing, NI myDAQ, LabVIEW Cite this Article S. Merlin Gilbert and Raj M.L

http://www.iaeme.com/IJMET/index.asp 952 [email protected]

International Journal of Mechanical Engineering and Technology (IJMET)

Volume 10, Issue 2, February 2019, pp;952-964Article ID: IJMET_10_02_100

Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=2

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

COMPUTER INTEGRATED OVERLOAD RELAY

TESTING ANDDATA MANAGEMENT SYSTEM

USING NI MY-DAQ INSTRUMENT

S. Merlin Gilbert Raj

Dept of ECE, Karunya Institute of Technology & Sciences, Coimbatore

M.L. Merlin Sajini

Dept of EEE, Coimbatore Institute of Technology, Coimbatore

ABSTRACT

Thermal overload relays used for motor protection are most demanded in the

commercial and domestic market. Batch line process is followed for overload relay

assembly and testing. Testing Phase include test for several conditions like trip test, no

trip test, mid trip test for suitable current ratings specified in the datasheet and

continuity test. Existing test system carries out the testing procedure by human

intervention to manually set up the test cases and test reports are generated. It’s

observed, the thermal overload relays passed in the test phase incurs high failure rate

in the market scenario. The problem of thermal overload relay testing is addressed in

this work, considering the combination of modern enabling technologies for data

acquisitions and test measurement meters. An overload voltage protection PCB is

developed to safety measure the data acquisition device. A computer integrated

experimental test set-up is proposed to automate the overload relay testing process

using NI myDAQ LabVIEW instrument. G-programming is used to implement the

overload relay testing algorithm. Graphical user interface build in LabVIEW supports

the testing operator to set the reference current ratings and reference trip time. Test

reports data such as trip/non-trip/mid trip time current curves can be monitored and

stored for various test cases are stored in the database through LabVIEW.

Keywords Thermal Overload Relay, Automation testing, NI myDAQ, LabVIEW

Cite this Article S. Merlin Gilbert and Raj M.L. Merlin Sajini Computer Integrated

Overload Relay Testing Anddata Management System Using Ni My-Daq Instrument

International Journal of Mechanical Engineering and Technology (10)(2), pp;952-964

http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=2

1. INTRODUCTION

Nowadays, the quantity and complexity of electric circuits is constantly increasing, especially

in the automotive industry. The electrical contact has always been an essential part of the

electric circuit. Therefore, ensuring reliable connections is crucial to manage a successful

Computer Integrated Overload Relay Testing Anddata Management System Using Ni My-Daq

Instrument


operation of the system. Most electrical circuits have overload protections that break the power

supply in the event of an electric overload. These protections consist of automatic circuit

breakers, i.e., electrical switches designed to protect a circuit from damage caused by

overcurrent or short circuits. Its basic function is to interrupt current flow if a certain

requirement is not fulfilled and the system is at risk. Another device that enables the interruption

of the current in an electric circuit, in case of overload, is the fuse which operates once and then

must be replaced. However, unlike fuses, overload protection relays can be reset, either

manually or automatically, to restore normal operation.

The purpose of this proposed work is to develop a test method for a thermal overload

protection relay in order to create a general guideline with recommendations on how the

reliability of relays should be verified.

Thermal relays are commonly used as protective elements that automatically break an

electric circuit to prevent overheating. This overheating can be produced in case of overcurrent;

therefore, these mechanisms are often used as overload protection. When the thermal relays are

heated up followed by cooled down, it provides movement for switching. This movement is

due the property of bimetallic strip which, bends to switch ON/OFF circuit.

Jingying Zhao et.al [1] proposed consistency study on over-load relay based on its

functional characteristics, focal failure ways, the reliability assessment method, the sampling

theory and the reliability test theory method. The mentioned methods depend upon the

reliability characteristic value, time dependent test plan, sample based experimental study and

measurement of reliability test practice. In this paper, randomly picked samples from the batch

of arranged products only are tested for its functionality and so the failure rate is high. YanYan

Luo et.al [2] conducted failure analysis for various types of miniature circuit breakers using the

reliability compliance test to enhance the consistency level. N. I. Santoso et.al [3] proposed a

simulator to test the microprocessor controlled protective relays. The simulator in the test zig

generate the relevant voltage and current resolutions/divs to detect the corresponding events

from the system. Kernel based programs in the test monitor the entire process in the test.

Over past years, LabVIEW Workbench was getting familiar to build prototype models using

the G-programming approach in the areas of mechanical, biomedical engineering and electronic

engineering [4]. Jung-Chuan Chou et.al [5] proposed a fault diagnosis approach using

LabVIEW workbench-based test and measurement system for flexible array pH sensors.

Changting Wang et.al builds graphical user interface which could conduct the online

measurement and acquires data to projects in time and frequency domain respectively for

monitoring the combined bearing condition [6]. Amine Yazidi et.al [7] presents a web-based

monitoring and fault detection using integrated LabVIEW workbench for AC Electrical

Machines. On the whole further details on extensiveness of LabVIEW based Workbench for

various applications can be found in [8-12]

In this paper, complete virtual and interactive software was developed for performing

functionality test to achieve reliability and quality of the over-load relay. LabVIEW based

Workbench to conduct functional testing in thermal overload relay is found to be first initiative.

The developed reliability test method for over-load relays includes various test criteria. The test

criteria of over-load relays include three trip points of over-load current, that is, 1.05 times

current, 1.25 times current, 1. 5 times current for the reliability test. The tested BR-Bimetallic

Overload Relay consists of Three-Phase protection with bimetals to detect the over load current

through the heating of the conducting strip. Bimetallic Overload Relay are available in five

frames for motor full load currents from 0.28A – 112 A.

S. Merlin Gilbert and Raj M.L. Merlin Sajini


2 THERMAL OVERLOAD RELAY CHARACTERISTICS

Very often, thermal overload relays are used to protect the motor. Fig 1 shows the three-phase

thermal overload relay and aesthetic appearance. The temperature of the bimetallic strip

increases due to increase in temperature of motor. A strong relationship can be obtained using

the heating curves of motor and thermal overload relay. For a specific dial setting, the overload

relay promises to protect the motor by not tripping the relay unnecessarily. Fig 2. shows the

Wilbur graph sketching the variations of tripping current with respect to tripping time for

specific dial setting currents.

Figure 1 Thermal Overload Relay

Figure 2 Dial Setting Current Vs Time

3 CONVENTIONAL OLR TEST PROCEDURES

The testing of overload relays involves various stages [1].

a. Category tests

b. Production tests

c. Commissioning tests

d. Maintenance tests.

Type Test is conducted based on the written specification and compliance standards. It

ensures the pass or fail of relay mainly under the fault operating conditions. During Production

tests, relays are tested for defects during manufacturing. Various test points are charted to detect


Instrument


the problems earlier and save time. Commissioning Tests are framed to ensure the protection

scheme is appropriately settled during the installation process. Including correctness of the

equipment, wiring check and operation checks are schematically followed during the test

process. Maintenance checks are required to find out the appropriateness of the equipment on

time.

In this work, we focussed on factory production test. Overload relays are ranked based on

the duration of trip time under faulty conditions. The thermal overload relay samples are tested

and validated by manual testing and the trip time, no trip time and mid trip time datas are

recorded manually.

3.1. TESTING OF OLRs FOR TRIP CLASS IN INDUSTRIES

After manufacturing, the overload relays are tested for trip time in order to categorize the OLRs

based on trip time. The testing process involves giving the 230V coil supply to the contactor

and passing certain amount of current through the OLR with contactor either through single

phase or three phase supply. The amount of current to be passed is calculated according to the

dial setting in the OLR, which the dial setting is multiplied by a certain factor to calculate the

current as shown in Fig 3.

Figure 3 Adjustable Current Settings in OLR

3.2. PROBLEM WITH THE EXISTING METHOD

• After the OLR trips while testing, the trip time of the OLR is noted down manually from

the testing panel which has high probability of manual errors.

• The coil supply is also not cut off until the operator disconnects the supply which leads

to wastage of power.

• The trip time noted down are stored into the computer manually which is time

consumption.



Figure 4 Manual Testing of OLR

In order to overcome the drawbacks in the existing manual testing method as shown in Fig

4, we focussed on extending the factory production test using Virtual Instrumentation platform.

To overcome the error and false rate in test cases due to human interventions, here we deployed

NI myDAQ hardware to monitor the flow of current in overload relay under various test cases.

3.3 PROPOSED AUTOMATED OLR TESTING SYSTEM

LabVIEW (Laboratory Virtual Instrument Engineering Workbench) from National Instruments

is used as a platform to automate the OLR testing and report generation process as shown in

Fig 6. Fig 5 shows the automation testing for overload relays.The OLR samples tested and

validated by manual testing method has larger failure rate in the market. Also, the trip time, no

trip time and mid trip time datas are recorded manually. This requires one person has to monitor

and log the datas in the test sheet which consumes time. Hence, there is a need for automated

test process. The error and false rate in test cases due to human interventions can be avoided by

this automated method.

Figure 5 Automated Testing of OLR


Instrument


Figure 6 Block Diagram of Automated Test-Tool

NI myDAQ is a portable data acquisition (DAQ) device that uses NI LabVIEW-based

software instruments to measure and analyze real-world signals as shown in Fig 7. Combined

with NI LabVIEW on the PC, it can analyze, and process acquired signal and control the

automated system depending on programming the input output pins of myDAQ in LabVIEW.

Figure 7 NI myDAQ

The myDAQ is interfaced with the OLR where the high current is passed for testing. Hence

the protection circuit has been used in order to prevent any backflow of high current into

myDAQ pins since the pins are designed for low current applications. Specially designed

protection circuit for myDAQ is shown in Fig 8. Also Fig.9 shows the Protection Circuit Board,

Figure 8 Protection Circuit Layout



Figure 9 Protection Circuit Assemble and Soldered

4.1 OVERLOAD RELAY TESTING PROCEDURE

Step:1 OLR with contactor, Ammeter, Rheostat load are connected in series to 230V supply

through auto transformer.

Step:2 The NC terminals of OLR and the enable pins of the Opto-coupler which controls

coil supply are connected to the programmed pins in DAQ.

Step:3The coil supply to the OLR is controlled by the 5V relay by enabling the optocoupler

pins through programming.

Step: 4 Set the current according to the dial setting in the OLR.

Step: 5 Scan the barcode value of the OLR’s into the LabVIEW using barcode scanner.

Step:6 Switch ON the Boolean switch in the LabVIEW that controls the 230V coil supply

to OLR.

Step:7 Two Boolean indicators are used in LabVIEW to indicate the conduction between

two NC terminals when there is flow of current in the OLR.

Step:8 Run the program and the timer in LabVIEW starts as the coil supply is enabled.

Step:9 After certain time the healthy OLR trips according to the predefined time with

respect to dial setting for current whereas the faulty OLR wil not trip in the predefined t ime.

Step: 10 When the OLR trips the conduction between the NC terminals of OLR breaks

which is detected through DAQ.

Step: 11 After the detection of tripping by DAQ the timer stops automatically, and the coil

supply is disabled automatically.

Step: 12 After tripping the Boolean switches for indicating the coil suppy to OLR and the

conduction between the NC terminals OFF automatically.

Step: 13 In case of multiple OLR testing the coil supply of the tripped OLR alone will be

disabled by programming whereas the coil supply of other OLRs will be enabled till it trips.

Step:14 The OLRs that didn’t trip with respect to the predefined time are indicated as faulty

in LabVIEW.

Step: 15 The barcode value and the trip time (current) is stored together and is loaded into

the MS-Excel which can be used for further reference.

Step: 16 OLRs can also be sorted out automatically in LabVIEW according to the given trip

time.

Step: 17 The trip time of any tested OLR can be checked by simply scanning the barcode

value of the OLR into the LabView.


Instrument


TEST SETUP IN LABVIEW

The front panel control for the OLR testing is designed in such a way to show the barcode, trip

time, current, dial setting and also the status of the OLR while testing. The front panel is made

as user interface where the operator can set the lower and the upper time limit for testing the

OLR for trip time. If the OLR trips below the time limit then the FAULTY indication is ON, if

it trips within the time limit then the HEALTHY indication is ON and if the OLR does not trip

even after the time limit then the FAULTY indication is automatically ON.

Figure.11 Front Panel of the Test setup in LabVIEW



Test Setup

Figure 12 Entire Experimental setup

Figure 13 OLR in test setup

5 RESULTS AND DISCUSSION

The overload relays are tested for No trip test, Mid Trip Test and Trip Test for three trip

points of over-load current, that is, 1.05 times current, 1.25 times current, 1. 5 times of

maximum and minimum values of test current manually and the test reports for the three types

of test is given as follows.

This same method of testing of thermal overload relays are done through the proposed

method and the trip signals for healthy and faulty relays are shown below.

From all the trip signals for maximum and minimum dial setting of current values the faulty

relay trips before the normal trip time of the relay it has to withstand.


Instrument


Figure 14 No Trip Test –Maximum Dial Setting (6.8 A)

Figure 15 No Trip Test –Minimum Dial Setting (4.32 A)

Figure 16 Trip Test – Maximum Dial Setting (7.87 A)



Figure 17 Trip Test- Minimum Dial Setting(5A)

Figure 18 Mid Trip Test (7.72A)

6 CONCLUSION & FUTURE SCOPE

Since Automation in product development is on high demand nowadays, this project meets the

automation requirements of the Relay manufacturing companies. The proposed automated

Relay testing process helps to avoid the tedious manual testing methods and documentation

procedure, thereby reducing the time consumed during the testing process as well as technical

details of the OLR can be obtained easily by just scanning the barcode. The coil supply to the

OLR is automatically cut off after it trips in order to protect it. The trip time of the OLR is also

obtained as soon as the testing process is completed. The Front Panel Control is made as user

interface to set the lower and upper time into the program before running, which can be used to

find the condition of the OLR, i.e., HEALTHY or FAULTY. The customized report of the

technical details of the OLR are automatically stored in an excel file and the data are processed

for further reference. The proposed automated test-tool can also be extended for a large number

of OLR testing

. To make a fully automated testing system where the OLRs are being picked up

automatically from the assembly unit and are placed on the test-tool for the testing process. This

test-tool also has convenience in connecting to all necessary pins of OLRs automatically after

its being placed on the test-tool. Once, the testing process is completed, the healthy and faulty


Instrument


OLRs are separated by the system itself and the whole process report is stored in the company

server.

ACKNOWLEDGEMENTS

The authors wish to thank Karunya Institute of Technology & Sciences for providing the

infrastructure to complete the project successfully.

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COMPUTER INTEGRATED OVERLOAD RELAY TESTING ANDDATA ...€¦ · Keywords Thermal Overload Relay, Automation testing, NI myDAQ, LabVIEW Cite this Article S. Merlin Gilbert and Raj M.L