2013 11 potm circuit breaker testing en

7/23/2019 2013 11 PotM Circuit Breaker Testing En

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Circuit Breaker Testing Complexities Removed

Joint Authors: Aditya Taneja,Ulrich Klapper (OMICRON Electronics)

Introduction A circuit breaker is an electrical switch designed toprotect an electrical circuit from damage caused byoverload or short circuit. It is also used to isolatepart of a healthy circuit for regular maintenance. Itsoperation can therefore be both automatic andmanual. Its basic function is to immediatelydiscontinue electrical flow. The circuit breakerplays a significant role within the power systemwhere it;

> Minimizes losses in closed position> Opens and closes on command

> Opens or closes a circuit to connect the powerto/from the transmission line(O - break, C - make)

> Opens a circuit for planned maintenance (O -break)

> Opens a circuit at system fault to protect thesystem behind the circuit breaker (O break, O-C reclose, O-CO, auto-reclose)

> Isolates between poles (TRV), open contactsand earth

To ensure appropriate operation of the circuitbreaker it is important to test the performance ofkey components including;

> kinematic chain

> timing of main and auxiliary contacts

> contact travel (motion) of main contacts

> control circuits

> coil current analysis> minimum pick-up test

> charging motor > motor current analysis

> main contacts' wear and tear > contact resistance of main contacts (staticand dynamic)

Conventional testing of circuit breakers doesgenerally mean the disconnection of the circuitbreaker from the system. This involves aninevitable outage and brings about muchpaperwork and cost in order that safetyrequirements are met, often involving a number ofstaff to complete the work. It is imperative,therefore, that testing of circuit breakers is done inthe shortest possible time, utilising equipmentwhich provides accurate results.

The conventional set-up for circuit breaker testing(Figures 1 and 2) involves rewiring between micro-ohm measurement and timing tests. This involves

many cables, is time-consuming and error-prone.

Figure 1: Conventional wiring set-up for micro-ohmmeasurement

Figure 2: Conventional wiring set-up for timing tests

The wiring for the micro ohm certainly is not doneall in parallel in the conventional set-up, howeverall the wires shown in the picture are needed.

Classic Circuit Breaker Testing

Traditionally, reference to "circuit breaker testing"excluded the static resistance measurement,despite the fact that this is an absolutely necessary

test.OMICRON defines "circuit breaker testing" as:

the distribution of open and close commands ofthe circuit breaker with nominal and undervoltage

analysis of coil currents

the measurement on the main and auxiliarycontacts

static contact resistance testand if necessary,

a dynamic resistance measurement of the maincontacts

motion analysis or time travel diagram



Testing System Plan

OMICRON's new CIBANO 500 test systemcombines, in a single device, the three deviceswhich are typically required for circuit breaker

testing, including; Circuit breaker testing

Micro ohm measurement

Breaker supply

Figure 3: CIBANO 500's 3-in-1 solution

The measurements possible with this combinationof equipment enable the user to draw numerousconclusions regarding the condition of the circuitbreaker.

Through the analysis of coil circuits from thedifferent open and closed coils, it can bedetermined whether an operating characteristic ofany nature or manner is sluggish, and compare thechronological sequence with nominal values.

Timing analysis gives information on whether thedifferent main and auxiliary contacts are switchingwithin the correct time, according to themanufacturer's specified nominal behaviors.Synchronization of individual main contacts withina phase is therefore particularly important, but alsobetween the phases of the maximal permissibledeviations indicated by the manufacturer.

The dynamic resistance measurement allows therecording of resistance during the opening of the

main contacts. The point in time the current linepassed from the main to the arcing contact can beread from the curve. This time is decreased incomparison to earlier measurements so that thearcing contact becomes shorter. In combinationwith a travel analysis even the length of the arcingcontact in millimeter can be determined.

Figure 4: Dynamic resistance measurement (time in ms)

The motion analysis gives information on themechanical position of components of the circuitbreaker over time. The aim, if possible, is todetermine the position of the main contacts. Asthey are not directly accessible, motion sensorsare affixed to the closest possible points of themain contacts.

Statements that can be made from thismeasurement include whether the motion runswithin the specified boundary conditions. Also itcan show whether, for example, the damping of themotion towards the end of the switching processoccurs in the desired nature and manner.

The combination of dynamic resistancemeasurement and time travel analysis also allowsthe lengths of the arcing contacts to be added inmillimeters.

Static Resistance Measurement

The micro ohm measurement or static contactresistance measurement on the closed main

contacts is a further measurement that shouldtypically be undertaken.

It leads to a larger direct current via the maincontact and the voltage can be picked up withseparate cables as close as possible to the maincontact.

This measurement is particularly easy if it isundertaken with Kelvin clamps. A Kelvin clamp hastwo separately isolated terminal jaws. The currentfeeds to one side of the clamps and the voltage ismeasured on the other side. The clamps areperfectly suitable for massive lines like busbars or

conductor cables with large diameters.

Transfer from maincontact to arcingcontact

Opening of thearcing contact



Measuring on contact fingers, for example onmedium voltage circuit breakers, is more functionalwhen working with two separate clamps, wherebythe voltage clamps must then be nearer the maincontact.

Breaker SupplyTo test the circuit breaker the voltage must be leadto the trip and closing coils, but also the motortightening of the springs or the compression ofgases with which the circuit breaker operates, mustbe supplied.

To supply the circuit breaker during the test eitherthe previously used station battery or an externalsupply can be used. Using the station battery hasmany disadvantages:

the connection to the station battery can bevery dangerous depending on the system

the voltage of the station battery cannot becontrolled. It can fluctuate within a certain rangeand thus the test undertaken is onlyconditionally reproducible.

An external supply does not have thesedisadvantages if it is electronically stabilized,although unfortunately this is often not the case. Italso creates the need for an additional device.

With the CIBANO 500 the supply from coils andmotors is "on board". Thus you have more safetyfrom the independence of the station battery andperfect reproducibility due to the stable voltage. Additionally the setting of sources is automatically

realized in the protocol of the test.

Under-voltage tests through which the trip coils aretriggered with a voltage of 20% within the nominalvoltage for example, were previously verycomplicated. With the CIBANO 500 they onlyrequire a few mouse clicks.

Separate tests on the motor and recording of themotor current over time are also easy with the builtin supply.

CIBANO 500The CIBANO 500 main device offers all essentialfunctions that are required for testing all types ofcircuit breakers without the need for any peripheraldevices.

Figure 5:Medium-voltage, high-voltage and dead tankbreakers can be tested with CIBANO 500

It is therefore possible to undertake the followingfive standard tests on the circuit breaker:

Static contact resistance test (micro ohmmeasurement)

Test of the response threshold of trip and closecoils

Classic switching time tests

Recording of coil and motor current analyses

Under-voltage testsThus, the device offers all of the functions of asimple circuit breaker testing device, a source anda micro-ohmmeter combined in one device.

For high-voltage circuit breakers in particular, asimple circuit breaker testing device is notsufficient. Several interrupting units should bemeasured per phase simultaneously. In addition topure time analysis, a dynamic resistancemeasurement must also be performed. It is alsonecessary in high-voltage applications to leave thecircuit breaker grounded on both sides during the

entire test.The main contact modules CB MC2 (seen in smallpicture 4 between the interruption units) fulfill theserequirements and offer additional advantages.

Figure 6: CIBANO 500 with main contact modules CBMC2



The use of the main contact module offers thefollowing advantages:

Measurement of dynamic contact resistanceduring the opening and closing of the circuitbreaker

Measurement of several interrupting units at the

same time Both sides grounding of circuit breaker for

safety reasons during the entire measurement

Really simple cabling: The entire wiring is donedirectly on top of the circuit breaker and thecable only leads to the main device

Short cables: The digitalization is done directlyon top of the circuit breaker. Thus themeasurement errors through interference areminimized and the high-current cables are onlyshort and light

The external modules are connected via an

EtherCAT

®

Bus with the main device. Data is sentfrom and to the modules via the same cable thatalso supplies power to the module. The CB MC2modules temporarily require particular high powerin order to deliver up to 2 times 100 A for microohm measurements. They therefore have a built-intemporary power storage, however the current iselectronically stabilized.

The CB TN3 module can likewise be connected viathe EtherCAT

® Bus. Up to three analog or three

digital transducers can be optionally connected tothe module.

Figure 7:Module CB TN3 for recording of path/timediagrams

The travel or motion analysis provides furtherinsights into the condition of the circuit breaker.

The EtherCAT® Bus, which can supply the module

and synchronously deliver and collectmeasurement data from different positions of thecircuit breaker, offers even more expansionpossibilities of the circuit breaker measurementsystem in the future.

About the Authors

Aditya Taneja holds a

Bachelor’s degree in Power

Engineering (Electrical) from

National Power Training

Institute (India). He has

been working as Application

Engineer for Primary and

Secondary assets since

2009. He is currently

working as Regional

Application Specialist for Circuit Breakers and

Switchgears in Middle East & South Asia Region.

Ulrich Klapper studied electrical engineering at

the FernUniversität (Distance University) Hagen

and worked in different companies as a hardwareand software developer.

He has been working for OMICRON since 1998.Initially as a HardwareDeveloper and then later asProduct Manager. Today he is Innovation Manager(Development Manager) in the Business Unit forTesting and Diagnostic Solutions for Primary Assets.



www.omicron.at | www.omicronusa.com

OMICRON is an international company serving the electrical power industry with

innovative testing and diagnostic solutions. The application of OMICRON products

allows users to assess the condition of the primary and secondary equipment on

their systems with complete confidence. Services offered in the area of consulting,

commissioning, testing, diagnosis and training make the product range complete.

Customers in more than 140 countries rely on the company’s ability to supply leading-

edge technology of excellent quality. Service centers on all continents provide a broad

base of knowledge and extraordinary customer support. All of this together with ourstrong network of sales partners is what has made our company a market leader in the

electrical power industry.

For more information, additional literature,

and detailed contact information of our

worldwide offices please visit our website.

© OMICRON

http://www.omicron.at/

http://www.omicronusa.com/

http://www.omicronusa.com/

http://www.omicron.at/

2013 11 potm circuit breaker testing en

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