edoc commissioning circuit breakers

7/31/2019 Edoc Commissioning Circuit Breakers

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7/4/2011 Module Three 1

SUBSTATIONCOMMISSIONING COURSE

MODULE FOUR

CIRCUIT BREAKERSTESTING PROCEDURES


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INTRODUCTION

The electrical commissioning andacceptance testing of electric powersystems is essential for theenergization of any electrical systemfor the first time


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INTRODUCTION

Module Four

Discuss theory and ratings Safety issues Test equipment operation &

hands on testing


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INTRODUCTION

Skills learned in MODULE FOUR:

Acceptance testing for CircuitBreakers

Operate Breaker analyzer Apply safe work practices

Analyze test values Complete test forms


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CIRCUIT BREAKERS

North American Standards

US Standards NEMA ANSI/IEEE IEEE standards are

harmonized with IEC IEC are harmonized with IEEE


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CIRCUIT BREAKERS

Most Significant Standards

C37.04 Rating Structure for AC High Voltage CircuitBreakers

C37.06 AC High Voltage Circuit Breakers Rated on aSymmetrical Current Basis PreferredRatings and Related Required Capabilities

C37.09 Standard Test Procedures for AC HighVoltage Circuit Breakers Rated on a

Symmetrical Current Basis C37.010 Application Guide for AC High Voltage CircuitBreakers Rated on a Symmetrical CurrentBasis


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CIRCUIT BREAKERS


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CIRCUIT BREAKERS

Maximum Voltage Voltage range factor

Continuous current Short circuit

Symmetrical current Asymmetrical current

% DC component Interrupting time Maximum tripping delay

TRV Transient recoveryvoltage

Withstand voltage Power frequency Lightning impulse

Closing and latching

current

Rated Characteristics


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CIRCUIT BREAKERS

Application Considerations

Circuit Beaker definition (IEEE C37.100)

A circuit breaker is a mechanical device capable ofmaking, carrying and breaking currents under normalcircuit conditions and also making, carrying for aspecific time and breaking currents under specified

abnormal conditions such as those of short circuit


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CIRCUIT BREAKERS

The upper limit of the system voltage for continuousoperation

Rated maximum voltage: 4.76 kV 8.25 kV

15 & 15.5 kV 25.8 kV 38 kV

Maximum Voltage


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CIRCUIT BREAKERS

All North American Beakers are rated at 60Hz

Manufacturers to be consulted for operation at otherfrequencies

Frequency


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CIRCUIT BREAKERS

Operating within temperature rise specification Continuous current rating for normal operating

conditions Ambient temperature between -30 C to 40 C Installed above sea level and below 1000 m Free of extreme environmental contamination

Not affected by solar radiation Short time over current permissible for Motor starting, cold load pick-up, emergency

conditions

Continuous Current


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CIRCUIT BREAKERS

Rated constant symmetrical current rating in KA rms Synonymous with SF6 and vacuum breakers

Older breakers rated in constant MVA (oil, air-magnetic)

Isym = (Rated Isc) x (Rated Vmax / Vop) or Isym = MVA / (Vop x 3)

Short Circuit Current - Symmetrical


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CIRCUIT BREAKERS

Multiplier factor for symmetrical current rating Modern / future breakers will be rated at K = 1

Factor K to be eliminated in future standards Breakers to be rated on a constant symmetrical

current rating K Factor to address older breaker rated in constant

MVA

Voltage Range Factor K


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CIRCUIT BREAKERS

Asymmetrical current rating Symmetrical rating multiplied by S

Based on % DC rating for modern breakers %DC using standard decay curve for X/R = 17

Short Circuit Current - Asymmetrical


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% DC rating related to the speed of the breaker Fast breakers interrupt more DC current

Peak currents can be 2X symmetrical peak value Symmetrical current rides on decaying DC current DC current decay based on X/R of system

Slow breakers interrupt less DC current

Current falls towards symmetrical value

% DC


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CIRCUIT BREAKERS

The standard DC decay time constant can becalculated by:

= (X/R) / (2 f)

for X/R ratio of 17, = 45 msec



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CIRCUIT BREAKERS

The asymmetrical interrupting rating is calculated by:Iassym = Isym x S

S = [ 1 + 2 (%dc/100)2 ]

Iassym = Isym x [ 1 + 2 (%dc/100)2 ]



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CIRCUIT BREAKERS

Maximum allowable time between Energization of trip coil and arc extinction time

Rating based on: Rated control voltage Maximum opening mechanical pressure Arc extinction in all 3 poles

Interrupting time


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Why Delay tripping ? Breaker contacts works less, less wear and tear

Trade-off between increased interrupter / contactheating and speed

Contact heating a function of I2t

Permissible Tripping Delay T


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CIRCUIT BREAKERS

Asymmetrical current rating for closing unto a fault

Enables downstream protection to operate Can be man made faults leaving grounds on

Closing and Latching Current


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Power Frequency (60 Hz) dielectric test 1 minute time duration

Part of total lightning impulse tests

Trivia: Rate of rise at 2%/sec of the 75% level Test voltage reached between 60-70 sec, 90 sec

OK

Dielectric Withstand


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Series of factory dielectric tests Power frequency test; dry (1 minute), wet (10 sec)

Full-wave lightning impulse Chopped wave lightning impulse Switching impulse

Tests the insulation system Phase to ground Across open contacts

LightningImpulse Withstand Voltage


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CIRCUIT BREAKERS

Voltage generated across open contact after currentinterruption

Fast rise time and can peak at 2X ac crest value Dielectric must not flash-over after contact have

stopped and parted Contact separation is greater than required for

current interruption Rated in dV/dT or kV peak / time to peak

TRV Transient Recovery Voltage


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Norm. operating pressure Min. operating pressure

Volume of oil per tank Weight Instruction book number Part list number Capacitance current

switching Out of phase current

switching

Nameplate Data


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Close coil volt. range Trip coil volt. range

Closing / closing current Motor current / voltage Low pressure alarm / lock

out pressure operatingpoints

Wiring diagram number Instruction book number Parts list number

Mechanism Nameplate Data


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CIRCUIT BREAKERS

Shall includeidentification and

pertinent operatingcharacteristics

Accessories Nameplate Data


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Essential markingsshould be provided

Operating devices andpositions

Instructions foroperation

Special precautions Environmental

warnings

Instructions and WarningSigns


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CIRCUIT BREAKERS

Types ofcircuit Breakers

Air magnetic Oil Air blast SF6 Vacuum

Air Magnetic

Obsolete technology forMV class

Uses air as the dielectric In use until 1975


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Oil (tank / minimum / bulk)

Obsolete technologyexcept for low voltageapplications

Cease production is the1990s

Uses oil as the dielectric Up to 230 kV

Minimum oil was areplacement for air-magnetic in MV class


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SF6

Todays technology Use SF6 as the dielectric Use in MV and HV class


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Vacuum

Todays technology Use vacuum as the

dielectric Limited to MV

applications


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CIRCUIT BREAKERS

Functions ofCircuit

Breakers

Switching Fault Interruption

Interrupters Current interruption

Switching

Control the flow of electricalenergy by opening orclosing its main contacts

Breaker can be controlledlocally or remotely viaSCADA

Operations accomplished by

energizing the tripping orclosing coils


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CIRCUIT BREAKERS

Functions ofCircuit

Breakers



Fault Interruption

The primary equipment usedfor interrupting short circuitcurrents

A circuit breaker used forthree-phase is called a threepole breaker.

One interrupter per pole for

MV circuit breakers Series interrupters per polefor HV circuit breakers


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CIRCUIT BREAKERS

Functions ofCircuit

Breakers



Current interruption

Arcing contact separates Arc energy used to built

dielectric pressure Dielectric moves between

contacts at current zerocrossing

Maintained dielectric

equates to currentinterruption


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SAFETY CONSIDERATION

High Voltage Safety

Electrical safety using high voltage test equipment Testing performed by qualified personnel Familiarization with test set operations Know the hazards for the specific test

Safe working practice and guidelines

Safety practice regulations IEEE standard 510-1983; Recommended Practicefor Safety in High Voltage Testing and High PowerTesting


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X-Ray Radiation

High voltage across vacuum gap can produce x-rayradiation

Vacuum bottle integrity test voltage not to exceedmanufacturers recommended levels or 75% of thefactory dielectric test

Indoor breaker optimally tested in the test /

disconnected position for shielding Outdoor breakers tested at 1 metre distance withcovers in place as per indoor breakers outside itscubicle


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StaticHigh Voltage

Electrostatic charge may be retained after highvoltage potential is removed

Ground the primary bushing and mid-band ring for atleast 60 seconds


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Stored Energy

Mechanical adjustments and checks should only beattempted after: Stored energy have been discharge / isolated Operating mechanism have been blocked

Circuit breaker operation rely on the release /application of energy for closing and tripping

operations Charged spring / pneumatic pressure / hydraulicpressure

Energizing large operating coils


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CIRCUIT BREAKER TESTING

Mechanical Testing Inspection Manual tripping and

closing

Mechanical interlocks Contact timing

Electrical Testing Insulation resistance Dielectric withstand Vacuum bottle integrity

Contact resistance Operations PF (maintenance test

as required)


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closing


Inspection

Verify the ratingsmatches the designspecifications

Verify installed correctly Determine of any physical

damage duringinstallation or transport

Check all auxiliaryequipment are supplied


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closing


Manual tripping / closing

Energy storage devices Trip / latch mechanism Manual charging system

Operations counter


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closing


Mechanical Interlocks

Positive interlock Spring discharge interlock Rating interference plate


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as required)

Insulation Resistance

DC voltage test 100% of the Rated AC

phase-ground crest value

Crest value = 1.414 xVAC rms

Preliminary to thedielectric withstand test

Note: Value > NETArecommended test value


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Electrical Testing Insulation resistance Dielectricwithstand Vacuum bottle integrity


as required)

Dielectric Withstand

AC 60 Hz test at 75% ofthe factory test value

Voltage applied across

open contacts Voltage applied across

phase to ground withcontacts closed

Untested terminalgrounded


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as required)

Vacuum bottle integrity AC 60 Hz test at 75% of

the factory test value Voltage applied across

open contacts Test time can be limited

to 10 sec for somebreaker type


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as required)

Contact Resistance

100 Adc Resistance from bushing

terminal to bushing

terminal Using 4-wire resistance

measurement test set


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Electrical Testing PFTest (Classified as a

maintenance test

Insulation test Bushing test

Power Factor Test

Establish initial baselinereading for comparisonand trending

Similar to the capacitanceand power dissipationtest

Test voltage below

operating phase-to-ground value


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Electrical Testing PF (maintenance test

as required) Insulation test

Bushing test

Bushing Test

Hot collar test Non condenser

bushing

GST Collar material

Conducting Uniform dimension


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TEST SET MANUAL

Module 4:Breaker Timing Test setPower Factor Test Set

Module 2 & 3CT Tester15 KV Insulation Resistance Test setAC High Potential Test set

DC High Potential Test setDigital Low Resistance Test set


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edoc commissioning circuit breakers

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