module 4 commissioning circuit breakers

04/09/23 Module Three 1

SUBSTATION COMMISSIONING COURSE

MODULE FOUR

CIRCUIT BREAKERSTESTING PROCEDURES


INTRODUCTION

• The electrical commissioning and acceptance testing of electric power systems is essential for the energization of any electrical system for the first time


INTRODUCTION

Module Four

• Discuss theory and ratings• Safety issues• Test equipment operation & hands

on testing


INTRODUCTION

Skills learned in MODULE FOUR:

• Acceptance testing for Circuit Breakers

• Operate Breaker analyzer• Apply safe work practices• Analyze test values• Complete test forms


CIRCUIT BREAKERS

North American Standards

• US Standards– NEMA– ANSI/IEEE– IEEE standards are harmonized

with IEC– IEC are harmonized with IEEE


CIRCUIT BREAKERS

Most Significant Standards

• C37.04 Rating Structure for AC High Voltage Circuit Breakers

• C37.06 AC High Voltage Circuit Breakers Rated on a Symmetrical Current Basis – Preferred

Ratings and Related Required Capabilities• C37.09 Standard Test Procedures for AC High

Voltage Circuit Breakers Rated on a Symmetrical Current Basis

• C37.010 Application Guide for AC High Voltage Circuit Breakers Rated on a Symmetrical Current Basis


CIRCUIT BREAKERS


CIRCUIT BREAKERS

• Maximum Voltage• Voltage range factor• Continuous current• Short circuit

– Symmetrical current– Asymmetrical current

• % DC component• Interrupting time• Maximum tripping delay

• TRV – Transient recovery voltage

• Withstand voltage– Power frequency– Lightning impulse

• Closing and latching current

Rated Characteristics


CIRCUIT BREAKERS


CIRCUIT BREAKERS

Application Considerations

• Circuit Beaker definition (IEEE C37.100)

A circuit breaker is a mechanical device capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specific time and breaking currents under specified abnormal conditions such as those of short circuit


CIRCUIT BREAKERS

• The upper limit of the system voltage for continuous operation

• Rated maximum voltage:– 4.76 kV– 8.25 kV– 15 & 15.5 kV– 25.8 kV– 38 kV

Maximum Voltage


CIRCUIT BREAKERS

• All North American Beakers are rated at 60Hz

• Manufacturers to be consulted for operation at other frequencies

Frequency


CIRCUIT BREAKERS

• Operating within temperature rise specification• Continuous current rating for normal operating

conditions– Ambient temperature between -30 ºC to 40 ºC– 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


CIRCUIT BREAKERS

• Preferred continuous current ratings:– 600 A– 1200 A– 2000 A– 3000 A

• > 3000A required force cooling for indoor metalclad

Continuous Current


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


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


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


CIRCUIT BREAKERS


CIRCUIT BREAKERS

• % 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


CIRCUIT BREAKERS

• The standard DC decay time constant can be calculated by:

τ = (X/R) / (2 π f)

for X/R ratio of 17, τ = 45 msec



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 ]



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


CIRCUIT BREAKERS


CIRCUIT BREAKERS

• Why Delay tripping ?– Breaker contacts works less, less wear and tear– Trade-off between increased interrupter / contact

heating and speed

• Contact heating a function of I2t

Permissible Tripping Delay T


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


CIRCUIT BREAKERS

• 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


CIRCUIT BREAKERS


CIRCUIT BREAKERS

• 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

Lightning Impulse Withstand Voltage


CIRCUIT BREAKERS

• Voltage generated across open contact after current interruption

• 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


CIRCUIT BREAKERS


CIRCUIT BREAKERS

• Name• Type• Serial number• Year of manufacture• Maximum voltage• Continuous current• Frequency• Withstand voltages

• Duty cycle• Interrupting time• Short circuit current• % dc• Short time current

duration

Nameplate Data


CIRCUIT BREAKERS

• 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


CIRCUIT BREAKERS

• Close coil volt. range• Trip coil volt. range• Closing / closing current• Motor current / voltage• Low pressure alarm / lock

out pressure operating points

• Wiring diagram number• Instruction book number• Parts list number

Mechanism Nameplate Data


CIRCUIT BREAKERS

• Shall include identification and pertinent operating characteristics

Accessories Nameplate Data


CIRCUIT BREAKERS

• Essential markings should be provided– Operating devices and

positions– Instructions for

operation– Special precautions– Environmental

warnings

Instructions and Warning Signs


CIRCUIT BREAKERS

Types of circuit Breakers• Air magnetic• Oil• Air blast• SF6• Vacuum

Air Magnetic• Obsolete technology for

MV class• Uses air as the dielectric• In use until 1975


CIRCUIT BREAKERS


Oil (tank / minimum / bulk)• Obsolete technology

except for low voltage applications

• Cease production is the 1990’s

• Uses oil as the dielectric• Up to 230 kV• Minimum oil was a

replacement for air-magnetic in MV class


CIRCUIT BREAKERS


Air Blast• Obsolete technology• Use dry air as the

dielectric• Up to 500 kV• Hi pressure up to 3600

psi


CIRCUIT BREAKERS


SF6• Today’s technology• Use SF6 as the dielectric• Use in MV and HV class


CIRCUIT BREAKERS


Vacuum• Today’s technology• Use vacuum as the

dielectric• Limited to MV

applications


CIRCUIT BREAKERS

Functions of Circuit Breakers

• Switching• Fault Interruption

– Interrupters– Current interruption

Switching• Control the flow of electrical

energy by opening or closing its main contacts

• Breaker can be controlled locally or remotely via SCADA

• Operations accomplished by energizing the tripping or closing coils


CIRCUIT BREAKERS




Fault Interruption• The primary equipment used

for interrupting short circuit currents

• A circuit breaker used for three-phase is called a three pole breaker.

• One interrupter per pole for MV circuit breakers

• Series interrupters per pole for HV circuit breakers


CIRCUIT BREAKERS




Interrupters• Mounted on insulators• Encloses main contacts in

an insulating medium• Moving contact connected to

an insulated operating rod• Operating rod connected to

the operating mechanism• Mechanism provides energy

to operate at rated speed


CIRCUIT BREAKERS




Current interruption• Arcing contact separates• Arc energy used to built

dielectric pressure• Dielectric moves between

contacts at current zero crossing

• Maintained dielectric equates to current interruption


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 Practice

for Safety in High Voltage Testing and High Power Testing



X-Ray Radiation

• High voltage across vacuum gap can produce x-ray radiation

• Vacuum bottle integrity test voltage not to exceed manufacturer’s recommended levels or 75% of the factory dielectric test

• Indoor breaker optimally tested in the test / disconnected position for shielding

• Outdoor breakers tested at 1 metre distance with covers in place as per indoor breakers outside its cubicle



Static High Voltage

• Electrostatic charge may be retained after high voltage potential is removed

• Ground the primary bushing and mid-band ring for at least 60 seconds



Stored Energy• Mechanical adjustments and checks should only be

attempted 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 / hydraulic

pressure– Energizing large operating coils


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)





Inspection• Verify the ratings

matches the design specifications

• Verify installed correctly• Determine of any physical

damage during installation or transport

• Check all auxiliary equipment are supplied





Manual tripping / closing• Energy storage devices• Trip / latch mechanism• Manual charging system• Operations counter





Mechanical Interlocks• Positive interlock• Spring discharge interlock• Rating interference plate





Contact Timing• Measure the operating

parameters– Closing / tripping time– Discrepency time– Operating rod travel

performance• Two types of timer

– Digital timer– Digital timer and travel

analyzers




as required)

Insulation Resistance• DC voltage test• 100% of the Rated AC

phase-ground crest value• Crest value = 1.414 x

VAC rms• Preliminary to the

dielectric withstand test

Note: Value > NETA recommended test value




as required)

Dielectric Withstand• AC 60 Hz test at 75% of

the factory test value• Voltage applied across

open contacts • Voltage applied across

phase to ground with contacts closed

• Untested terminal grounded




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 some breaker type




as required)

Contact Resistance• 100 Adc• Resistance from bushing

terminal to bushing terminal

• Using 4-wire resistance measurement test set




as required)

Operations• Breaker in the normal

pos’n• Control circuit wiring

tested (shorts / grounds)• Operation tests for:

– Close and trip test– Trip-free test– Ant-pump test– Anti-slam test– Interlock test



• Electrical Testing– PF Test– (Classified as a

maintenance test• Insulation test• Bushing test

Power Factor Test• Establish initial baseline

reading for comparison and trending

• Similar to the capacitance and power dissipation test

• Test voltage below operating phase-to-ground value



• Electrical Testing– PF (maintenance test

as required)• Insulation test• Bushing test

Insulation Test



• 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


NETA STANDARD

6. NETA Acceptance Testing Procedure

» 6.1 Visual and Mechanical Inspection

» 6.2 Electrical Test

» 6.3 Test Values


TEST SET MANUAL

Module 4:Breaker Timing Test setPower Factor Test Set

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

module 4 commissioning circuit breakers

Documents

current module

circuit breakersfrequency

circuit breakersclosing

dc current current falls

normal circuit conditions

kv742011 module

dc rating

modern breakers