NETA MV Breaker Testing

SUBSTATION COMMISSIONING COURSE Page 1 of 60

SUBSTATION COMMISSIONINGCOURSE

MODULE FOUR

COMMISSIONINGCIRCUIT BREAKERS

Written by:Raymond Lee, Technical TrainerCopyright ©2010

Electrical Industry Training Centre of Alberta4234 – 93 StreetEdmonton, Alberta, CanadaPhone: (780) 462-5729Fax: (780) 437-0248

Module 4 Commissioning Circuit Breakers 1 of 60


TABLE OF CONTENT

Headings Page



IntroductionThis module will detail the requirements for performing electrical and mechanical tests on the MV circuit breakers. The purpose of the test, testing requirements and procedures are presented.

This module will introduce the NETA acceptance testing procedures for circuit breakers comprising of mechanical and visual inspections, electrical testing and test data analysis. General guidelines for acceptance testing will be presented. When equipment specific instructions are required the equipment manuals should be consulted.

Circuit breaker are used to control power flow and designed to interrupt short circuit current with the use of protective relays. An understanding on the theory of operations, functions, types and ratings are discussed and this information will be useful when performing acceptance tests. The discussion will be applicable to the medium voltage class, station type and indoor / outdoor circuit breakers. Circuit breakers for application in Gas Insulated Substation (GIS) and generator circuit breakers are not discussed.

It is beyond the scope of this module to discuss the details of circuit breaker design and their arc extinguishing technologies. Any breaker design discussions will be limited in scope.

ObjectiveBy the end of this module the participants will have the basic skills to perform acceptance testing on circuit breakers, conduct visual and mechanical inspections, perform insulation resistance tests, dielectric withstand test, contact resistance test, timing test, operational tests, control circuit checks, power factor test and completing the inspection / test forms and conducting an assessment of the test data.



1. North American Circuit Breaker StandardsThe principle North American AC high voltage circuit breaker standards in use today are the US standards which comprise of the ANSI/IEEE, and NEMA standards. ANSI/IEEE standards for the most part have been harmonized with the IEC standards and in turn the IEC standards have been harmonized with the ANSI/IEEE standards.

There are no existing Canadian CSA standards for the AC high voltage circuit breakers for rating or application guidelines / specifications.

Table 1 lists the principle standards that are applicable to AC high voltage circuit breakers. The standards listed are not all inclusive as it excludes the generator breakers and applications for shunt capacitor and reactor applications. There are also other standards that are applicable to relays, device numbers, wires and equipment or devices for use in conjunction with circuit breakers that are not listed.

The more significant ANSI/IEEE standards are:• 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



Table 1: North American AC High Voltage Circuit Breaker StaandardsSTANDARD REV SPONSOR TITLE WORKING

GROUPC22.021 1999 IEEE Standard for Metal Clad SwitchgearC37.04 1999 IEEE Standard Rating Structure for AC HV Circuit Breakers IEEEC37.06 2009 ANSI/IEEE Standard for AC HV Circuit Breakers Rated on a Symmetrical

Current Basis – Preferred Ratings and Related Required Capabilities for voltages above 1000 V

NEMA

C37.09 1999 ANSI/IEEE Test Procedure for AC HV Circuit Breakers Rated on a Symmetrical Current Basis

IEEE

C37.010 1999 ANSI /IEEE

Application Guide for AC HV Circuit Breakers Rated on a Symmetrical Current Basis

IEEE

C37.11 1997 ANSI/IEEE Requirements for Electrical Control for AC High Voltage Circuit Breakers Rated on a Symmetrical Current Basis

IEEE

C37.12 1991 ANSI AC High Voltage Circuit Breakers Rated on a Symmetrical Current Basis – Specification Guide

AEIC

C37.24 2003 ANSI/IEEE Guide for Evaluating the Effects of Solar Radiation on Outdoor Metal-Enclosed Switchgear

C37.85 2002 ANSI/IEEE AC high Voltage power vacuum Interrupters– Safety Requirements for X-Radiation Limits

NEMA

C57.13 2008 IEEE Standard Requirements for Instrument Transformers IEEESG-4 2009 NEMA Alternating Current High Voltage Circuit Breakers NEMA

1. Indoor circuit breakers are recognized in C37.09 for their unique test and application requirements as dictated by their use in metal-clad switchgear.



1.1 RatingThe ratings of a circuit breaker are considered to be the minimum design limits that are expected to be met by the device operating under defined operating conditions. This includes its operating devices and auxiliary equipment.

Rated Characteristics• Maximum voltage; kV rms• Voltage range factor; K• Continuous Current, Amperes rms• Symmetrical Interrupting current; kA rms• % DC component (asymmetrical Interrupting current, kA peak• Interrupting time, msec• Maximum Permissible Tripping Time Delay; sec• Transient recovery voltage; kV peak, μsec time to peak• Withstand voltage, power frequency; kV rms• Withstand voltage, BIL; kV crest• Closing and latching current; kA peak

Table 2 and 3 shows the preferred rating for the medium voltage circuit breakers as tabled in IEEE C37.06.



Table 2: Preferred Ratings for Indoor Circuit Breakers with Rated Voltage Range Factor K=1.0Rated

MaximumVoltage(kV rms)

Rated Continuous Current

(Amperes rms)

Rated Short-circuit and Short Time

Currents(kA rms)

Rated Transient Recovery Voltage

Rated Interrupting

Time(ms)

Maximum Permissible

Tripping Time Delay Y

(sec)

Rated Closing and latching

Current(kA peak)

Rated Peak

Voltage E2

(kV peak)

Rated Time to Peak T2

(μ sec)4.76 1200, 2000 31.5 8.9 50 83 2 824.76 1200, 2000 40 8.9 50 83 2 1044.76 1200, 2000, 3000 50 8.9 50 83 2 1308.25 1200, 2000, 3000 40 15.5 60 83 2 1015 1200, 2000 20 28 75 83 2 5215 1200, 2000 25 28 75 83 2 6515 1200, 2000 31.5 28 75 83 2 8215 1200, 2000, 3000 40 28 75 83 2 10415 1200, 2000, 3000 50 28 75 83 2 13015 1200, 2000, 3000 63 28 75 83 2 16427 1200 16 51 105 83 2 4227 1200, 2000 25 51 105 83 2 6538 1200 16 71 125 83 2 4238 1200, 2000 25 71 125 83 2 6538 1200, 2000, 3000 31.5 71 125 83 2 8238 1200, 2000, 3000 40 71 125 83 2 104



Table 3: Preferred Ratings for Outdoor Circuit Breakers 72.5 kV and Below Including Circuit Breakers Applied in Gas Insulated Substation with Rated Voltage Range Factor K=1.0

Rated MaximumVoltage(kV rms)

Rated Continuous Current

(Amperes rms)

Rated Short-circuit and Short Time

Currents(kA rms)

Rated Transient Recovery Voltage

Rated Interrupting

Time(ms)

Maximum Permissible

Tripping Time Delay Y

(sec)

Rated Closing and latching

Current(kA peak)

Rated Peak

Voltage E2

(kV peak)

Rated Time to Peak T2

(μ sec)15.5 600, 1200 12.5 29 36 83 2 3315.5 1200, 2000 20 29 36 83 2 5215.5 1200, 2000 25 29 36 83 2 6515.5 1200, 2000, 3000 40 29 36 83 2 10425.8 1200, 2000 12.5 48.5 52 83 2 3325.8 1200, 2000 25 48.5 52 83 2 6538 1200, 2000 16 71 63 83 2 4238 1200, 2000 20 71 63 83 2 5238 1200, 2000 25 71 63 83 2 6538 1200, 2000 31.5 71 63 83 2 8238 1200, 2000, 3000 40 71 63 83 2 104

48.3 1200, 2000 20 91 80 83 2 5248.3 1200, 2000 31.5 91 80 83 2 8248.3 1200, 2000, 3000 40 91 80 83 2 10472.5 1200, 2000 20 136 106 83 2 5272.5 1200, 2000 31.5 136 106 83 2 8272.5 1200, 2000, 3000 40 136 106 82 2 104



1.2 Application ConsiderationsThe main functions of circuit breakers can be found in its definition in IEEE C37.100. Circuit breaker applications must address many items of technical importance to ensure that misapplication does not happen.

“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”.

The following notes will present a brief explanation of the breaker ratings without an in depth technical explanations. Technical details can be found in the referenced standards and suggested reading section.

Maximum voltageThe rated maximum voltage is the upper limit of the system voltage for which the breaker application is to be used on a continuous basis.

Rated maximum voltage for medium voltage class circuit breakers are:• 4.76, 8.25, 15, 15.5, 25.8, 38 kV

FrequencyThe rated North American frequency is 60 Hz. Manufacturers should be consulted for applications at other frequencies.

Continuous CurrentThe rated continuous current rating sets the upper limit for the temperature rise of the breaker operating for usual service conditions such as:

• Operating at an ambient temperature not exceeding 40 ºC• Installed at an altitude above sea level and up to 1000m or less• Effects of solar radiation is not significant• Seismic loading is not significant relative to total weight (.2g x Hor, .16g x

Vert. measured at the centre of gravity)

When a circuit breaker is properly selected for continuous current operation, it may be used for starting equipment such as motors, synchronous condensers and cold loads. Under these conditions, the continuous current rating may be momentarily exceeded without causing damage to the circuit breakers.

The preferred continuous current ratings are:



• 600, 1200, 2000, and 3000 amperes.

Short Circuit Current RatingThe rated short circuit current rating corresponds to the maximum value of symmetrical currents that can be interrupted by the circuit breaker.

Voltage Range Factor KThe rated voltage range factor K will be 1.0 for current and all future circuit breakers. This makes the circuit breaker short circuit current rating constant for all operating voltages up to the rated maximum voltage. Future standards will eliminate the voltage range factor as breakers will be treated as a constant current interrupting rated circuit breaker.

The constant current interrupting rating for circuit breakers are applicable to the vacuum and SF6 breaker whereas air magnetic and oil circuit breakers have a higher interrupting rating when operating at a voltage that is lower than the rated voltage. However since the air-magnetic and oil circuit breakers are obsolete, today’s standards are addressing the future direction of circuit breaker design and applications.

Symmetrical Interrupting CapabilityThe maximum symmetrical interrupting capability for a circuit breaker is K times the rated short circuit current. For modern breakers the interrupting capability is its symmetrical interrupting current since its K factor is equal to 1.0.

Note: For older circuit breakers, the symmetrical interrupting capability between the rated maximum voltage and 1/K times the rated maximum voltage is:

Isym = (Rated Isc) x (Rated Vmax / Voperate) or

Isym = MVA / (Voperate x √3)

% DC ComponentThe % DC component is related to the asymmetrical interrupting capability of the circuit breaker as defined by the symmetrical current. It is used to derive a multiplying factor for the symmetrical current to result in the asymmetrical current value.



The % dc requirement that circuit breakers are required to interrupt correlates to the contact parting time obtained from a standard decay curve based on an X/R ratio of 17 at 60 Hz. Refer to Figure 1.

Figure 1: Standard DC Decay curve for X/R ratio of 17 at 60 HZ.

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

Where:X = the system’s inductive reactance in ohms (Ω)R = the system’s resistance in ohms (Ω)π = phiF = frequency



The asymmetrical interrupting rating is calculated multiplying the symmetrical rating by a factor S. Calculation for S:

S = 2)100

%(21dc×+

Where:%dc = the short circuit percent DC current breaking requirement as related t

to the breaker speed for systems with X/R = 17.

Therefore:

It = Isym x S

or

It = Isym x 2)100

%(21dc×+

Interrupting TimeThe rated interrupting time is the maximum allowable time between the energization of the trip circuit at rated voltage (and rated mechanism pressure for gas circuit breakers) and the arcing extinction time at the main contact in all poles.

It is used to classify breakers at different speeds. Refer to figure 2.

Note: Oil and air magnetic circuit breakers may have interrupting time greater than the rated interrupting time when interrupting below 25% of the rated interrupting capability at maximum voltage.

Note: Rated interrupting time can be exceeded for extreme cold weather condition, low control voltage, low stored energy mechanism and certain fault types.

Figure 2 shows the various time interval for a circuit breaker with resistor contacts.



Figure 2: Resistorized Breaker Operating Time

Permissible Tripping Delay TThe rated permissible tripping delay is a thermal limit when considering delayed tripping schemes to reduce asymmetrical fault currents to decay towards the symmetrical fault current values.

Total energy dissipated = I2t (joules)

Closing and Latching CurrentThe closing and latching current is the asymmetrical peak current rating that the breaker must be able to withstand closing onto a faulted situation and stays in the latched position. The ability to stay latched and overcome the mechanical short circuit forces is required to enable downstream protection to operate and isolate the faulted part of the power system.Power Frequency Dielectric Withstand



The rated power frequency dielectric withstand capability is its voltage withstand capability with specified magnitudes and waveshapes of voltage applied under specified conditions.

The 1 minute power frequency dielectric withstand test provides a margin of safety for minor contamination, deterioration and voltage surges encountered during service.

• Dry power frequency withstand for indoor circuit breakers• Dry and wet power frequency withstand for outdoor circuit breakers

Field acceptance test are conducted at 75% of the factory values.

Table 4 shows the preferred factory dielectric withstand rating for dry and wet test applied to indoor and outdoor medium voltage breakers as tabled in IEEE C37.06.

Table 4: Preferred Dielectric Withstand Rating at 60 Hz 1

Rated maximum

voltage(kV rms)

1 Minute Dry(kV rms)

10 Second Wet

(kV rms)

Indoor Circuit Breakers4.76 19 Not required8.25 36 Not required15.0 36 Not required27 60 Not required38 80 Not required

Outdoor Circuit Breakers15.5 50 4525.8 60 5038 80 75

1. Not applicable for breakers used in gas insulated substation.



Lightning Impulse Withstand VoltageLightning impulse insulation level (or BIL basic impulse level) must be coordinated with surge arresters installed locations and specifications. A breaker in the open position may be subjected to surge voltage which can double due to reflection and may result in a line-to ground fault or an open gap dielectric failure of the circuit breaker.

The factory lightning impulse withstand voltage tests are:• Full-wave lightning impulse• Impulse voltage test for interrupters and resistors• Chopped wave lightning impulse (for outdoor circuit breakers rated 15.5 kV

and above)

The basic purpose of all dielectric withstand test is to ensure that insulation system to ground potential and the insulating medium across the open contacts in the breaker poles will not fail.

Transient Recovery VoltageTransient recovery voltage is the voltage limits to which the circuit breaker terminals can be exposed to following arc interruption. This is the voltage that will appear across the interrupters and which it must withstand in order to sustain an interruption. Failure of the dielectric to withstand the TRV after the contact parting cycle will result in a re-ignition or re-strike across the open contact and a failure of the interrupters.

Circuit breakers must be capable of interrupting three-phase grounded and ungrounded terminal faults and the rated short circuit current in any circuit in which the TRV does not exceed the rated TRV envelope.



Figure 3: Fault Current Interruption and Resulting TRV

The TRV rating is specified in kV peak (E2) and the time to achieve peak voltage in μsec (T2).

Below 100 kV, E2 specified at 1.88 x rated maximum voltage and T2 varies with rated voltage. Refer to table 2 and 3.

1.3 Nameplate DataThe nameplate data show the minimum requirement for equipment information.

Circuit breaker nameplate data shall include the following:• Manufacturer’s name• Manufacturer’s type designation• Manufacturer’s serial number• Year of manufacture• Rated maximum voltage• Rated power frequency• Rated continuous current



• Rated full wave lightning impulse withstand voltage• Rated switching-impulse withstand voltage1. Terminal-to-ground circuit breaker closed2. Terminal-to-ground circuit breaker open• Rated operating duty cycle• Rated interrupting time• Rated short circuit current• Percent dc component• Short time current duration• Normal operating pressure• Minimum operating pressure• Volume of oil per tank or weight of as per circuit breaker• Weight of circuit breaker complete (with oil or gas)• Instruction book number• Part list number• Rating for capacitance current switching1. Rated overhead line charging current2. Rated isolated cable and isolated shunt capacitor bank switching current

3. rated back-to-back cable and isolated shunt capacitor bank switching current4. Rated transient inrush current peak5. Rated transient inrush current frequency

• Rated out-of-phase switching current

Note: It is beyond the scope of this module to provide a full description of all the nameplate data. The rating structure provides a basic understanding of the rating / nameplate data specifications of the circuit breaker.

Operating Mechanism Nameplate DataThe operating mechanism nameplate data may be combined with the circuit breaker nameplate data.

Operating mechanism nameplate data shall include the following:• Manufacturer’s name• Manufacturer’s type designation• Manufacturer’s serial number• Year of manufacture• Closing control voltage range



• Tripping control voltage range• Closing current• Tripping current• Compressor or hydraulic pump or spring charging motor control voltage

range• Compressor or hydraulic pump or spring charging motor current• Compressor or hydraulic pump control switch closing and opening pressure• Low-pressure alarm switch closing and opening pressure• Low-pressure lockout switch closing and opening pressure• Wiring diagram number• Instruction book number• Parts list number

AccessoriesNameplate of all accessories shall include identification and pertinent operating characteristics

1.4 Instructions and Warning SignsEssential marking should be provided to identify, provide or call attention to:

• operating devices and positions• instructions for operation• special precautions• environmental warnings

2. Types of Circuit Breakers

Note: It is beyond the scope of this module to provide a detailed description of the various circuit breaker types, operating principles and various interrupting technologies. Circuit breaker design information can be found in the listed references and suggested reading section.

Circuit breakers types are classified according to their arc interrupting technology. The circuit breaker types are:

• Air magnetic• Oil (tank oil, minimum oil and bulk oil)• Air Blast - Two-pressure and single pressure air blast• SF6 - Two pressure and single pressure SF6• Vacuum



Air Magnetic circuit breakers were older equipment used for indoor applications, 5kV – 38 kV were in dominant use until the 1975 time period. Air magnetic circuit breakers are currently in use for low voltage applications.

Bulk oil circuit breakers were made up to 150 kV and were superseded by the minimum oil circuit breaker in the 1930’s. Bulk oil circuit breakers ceased production in early mid-century and the minimum oil circuit breakers ceased production in the late 1980’s.

Air blast circuit breakers began production at the same time as the minimum oil circuit breakers in the 1930’s and was an alternative to the minimum oil circuit breakers. Air blast circuit breakers were used in MV to HV applications up to 500 kV. Air blast circuit breakers ceased production in the 1990’s.

The SF6 circuit breakers have their dominant position in the HV to Ultra HV applications and also available for MV application. SF6 circuit breakers began production in the 1960 as a two pressure SF6 circuit breaker. Advancement in design produced the single pressure SF6 circuit breaker which appeared in late 1970’s. SF6 circuit breakers are still in production today from the MV to the Ultra HV class.

The vacuum circuit breakers have their dominant position in the MV classs. It was introduced in the early 1970’s after the SF6 circuit breakers appeared. Vacuum circuit breaker are limited to use below 60 kV due to the non-linearity of the vacuum pressure dielectric strength at higher voltages as compared to SF6 gas dielectric property which are more linear when applied at higher gas pressures.

Note: The vacuum and SF6 circuit breakers are the two predominant types manufactured today for use above 1000V.

3. Functions of Circuit Breakers

3.1 SwitchingCircuit breakers are used to control the flow of electrical energy in an electrical networks by closing / tripping (or opening) its main contacts. Electrical energy is applied to downstream circuits when the breaker is closed and removed when the breaker is tripped.



Breaker operations can be performed locally at the breaker, from a local control station or remotely from a central station via SCADA. Breaker operations are accomplished by energizing the associated tripping and closing coils.

3.2 Fault interruptionCircuit breakers are the primary equipment used for interrupting short circuit currents. A circuit breaker used for three phase operation is called a three-pole circuit breaker. Each pole comprises of one interrupter or arc-extinguishing chamber. In HV applications, each pole may be fitted with multiple series interrupters and provisioned with grading capacitors or resistors for minimizing switching surges.

InterruptersThe interrupters are mounted on support insulators. The interrupter encloses a set of fixed and moving contacts called the main contacts. The moving contacts are connected to an insulated operating rod and can be drawn apart by linkages of the operating mechanism. The operating mechanism provides the mechanical energy for opening and closing of the main contacts at rated velocity.

3.3 Current InterruptionDuring contact separation, a dielectric media is introduced between the main contacts parting surfaces. The dielectric media’s functions are to cool the arc, to extinguish the arc and to provide a dielectric medium between the parting contacts. If re-ignition and re-strike of the arc is prevented, current interruption will be successful.



4. Circuit Breakers Testing

Note: The testing procedures described in this module are for vacuum and SF6 circuit breakers only. Oil, air-blast and air-magnetic circuit breakers which are obsolete and which are not encountered on new installation are not included.

4.1 Safety Considerations

4.1.1 High Voltage SafetyMany of the tests involve the use of high voltage test equipment, testing should be done by qualified personnel familiar with the test set operations and the hazards associated with the tests.

Safety working practices and guidelines are covered in module two.

Refer to module two for safety work practice when testing with high voltages.

Refer to IEEE Standard 510 – 1983, Recommended Practice for Safety in High Voltage & High Power Testing.

4.1.2 X-Ray RadiationHigh voltages applied across the open main contacts of the vacuum interrupters can produce x-rays. During vacuum bottle integrity tests, indoor vacuum breakers can be tested with maximum enclosure shielding when tested in the CONNECTED position. For testing indoor breakers outside of the enclosure, maintain a minimum distance of one meter. For testing outdoor circuit breakers, maintain a minimum distance of one meter with the covers in place.

Test voltage should not exceed the manufacturer’s suggested field testing levels or 75% of the factory dielectric test voltage levels.

4.1.3 Electrostatic ChargeAn electrostatic charge may be retained by the vacuum interrupters after high voltage potential is removed. Electrostatic charge should be discharged by direct grounding to prevent an electrical shock. All six primary bushings of the circuit breaker and the metallic mid-band ring should be grounded for at least 60 seconds.



4.1.4 Stored EnergyMechanical adjustments and checks should only be attempted after all stored energy devices have been discharged, isolated or after the application of blocking devices to the operating mechanism. Only manufacturer’s approved blocking devices should be used. Care should be taken to prevent the inadvertent application of energy to the breaker mechanism during testing.

Circuit breaker operations typically rely on the release of stored energy devices for its closing and tripping functions. Stored energy devices can consist of charged springs and pneumatic pressures or hydraulic pressure from accumulator storage systems. Circuit breaker function can also be initiated by the energization of large operating coils where its magnetic energy provides the power to move the operating mechanism.

4.1.5 Safety InterlocksMechanical interlocks are provided to ensure the safe operation of the equipment thus preventing hazardous condition to arise with may be injurious to personnel.

CAUTION:Do not defeat any safety interlocks that are provided for the proper operations of the circuit breakers.



4.2 Mechanical Testing:Mechanical testing consists of:

• Mechanical Inspections• Manual tripping and closing• Mechanical interlocks checks• Contact timing test / time travel test

4.2.1 Mechanical InspectionThe mechanical inspections are used to:

• Verify the circuit breaker ratings matches the design specifications• Verify the circuit breakers are installed correctly• Determine any physical damage resulting from installation or transport• Check supply of auxiliary equipment as listed in the manual

Mechanical Inspection Procedure1. For indoor circuit breakers remove the circuit breaker from the enclosure for

inspection.- Check for total freedom of movement of the wheels on a level surface. Roll the breaker steering with the metal frame.- Check for proper mechanical operation of the lifting hoist / truck devices

Caution: Do not handle or move the circuit breakers by the primary disconnecting devices, as damage may occur.

2. Confirm the nameplate rating with the contract specification, bill of material list or applicable drawings / one line diagrams / three line diagrams.

3. Confirm that the cubicles are properly grounded.

4. Confirm that the cubicles / structures are installed level and plumb.

5. Inspect the circuit breaker for signs of damage during shipping or installation.

6. Check the bushings for any signs of chipping for cracking.

7. Inspect the sealing compound between porcelain and the center conductor.

8. Ensure that the correct breaker is in the correct location / position.



4.2.2 Manual Closing and TrippingManual tripping and closing operations are conducted to verify the functionality of the:

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

Manual tripping and closing are performed with the circuit breakers out of the cubicle cell or tested in the cubicle cell in the TEST / DISCONNECTED position. The breaker operations counter will count of the number of operating cycles that the breaker has been subjected to. One operating cycle comprise of a Close and a Trip operation.

Manual Closing Procedure1. Record the operations counter reading

2. Verify that both the OPEN and DISCHARGE indications are shown.

3. Insert the manual charging handle into the appropriate slot for charging the ratchet drive for the closing spring.

4. Charge the closing spring by operating the manual charging handle.

Note: It may take several operations of the charging handle to fully charge the closing spring.

5. Listen for an audible indication that the holding pawl has latched onto the spring drive mechanism once the closing spring is charged.

6. Confirm that the CHARGED indicator is shown.

7. Remove the charging handle.

8. Depress the manual CLOSE pushbutton.

9. Verify that both the CLOSED and DISCHARGED indications are shown.

Manual Tripping Procedure



1. Verify that the CLOSED indication and discharged indication are shown.

2. Depress the manual OPEN pushbutton.

3. Verify that both the OPEN and DISCHARGED indications are shown.

4. Verify that the operations counter has incremented by one for mechanically operated counters.

4.2.3 Mechanical Interlock CheckThe mechanical interlock checks are performed for indoor circuit breaker to ensure that a circuit breaker cannot be inserted or disengaged from the primary bus with the main contacts left in the Closed position.

The most common mechanical interlocks are:• Positive interlock: Prevent moving the breaker to or from the CONNECTED

position while the main contacts are closed• Positive interlock: Prevent closing the main contacts unless the breaker is in

the fully connected position• Spring discharge interlock: To discharge all store energy in the breaker

mechanism whenever the breaker is withdrawn from the cubicle• Rating interference plate: Permits only a breaker with a matching continuous

current rating to be inserted into a compartment of identical rating

Mechanical Interlock Test Procedure

Note: The control power must be ON to enable the closing spring charging motor to function.

1. Insert the breaker into the cubicle cell and rack-in into the TEST / DISCONNECTED position.

2. Close the breaker main contacts.

3. Rack-in the breaker towards the CONNECTED position.

4. Verify that the mechanical interlock had opened the main contact before the cluster fingers engages the primary stabs.

5. Rack-in the breaker into the CONECTED position.



6. Close the breaker main contacts

7. Rack-out the breaker towards to the DISCONNECTED position, if possible.

8. Verify that the mechanical interlock prevents racking out of the breaker in the Close position, or had opened the main contact before the cluster fingers disengages from the primary stabs.

9. Rack-out the breaker to the TEST / DISCONNECTED position. The charged closing spring should have been discharged during the racking-out interval.

4.2.4 Contact Timing / Time Travel Test

Timing testThe breaker timing test is a mechanical test that analyzes the speed and position of the breaker main contacts before, during and after an operation. A contact monitor is applied to the breaker contacts and a position transducer is attached to the operating mechanism. The breaker is then cycled for a close and open operation. The contact change of state is timed and the travel signature of the operating mechanism is recorded.

There are two general types of timer in use:• digital contact timers• digital contact timers and breaker travel analyzers.

The digital contact timers are used for contact timing, it measure the contact transition time from the energization of the closing or tripping coils to the time that the main contacts changes position.

The travel analyzer measures the operating rod velocity, total travel, over travel, bounce back, speed / acceleration rate and the contacts operating time. The operating rod signature can be used to evaluate the condition of mechanical parts of the breaker, such as closing mechanism, springs and shock absorbers. Test data are analyzed and compared to the original factory specifications.



Operating TimesThere are 3 operating time parameters that assess the condition of the circuit breaker main contacts:

• Discrepancy time (or pole spread time)• Closing time• Opening time

Discrepancy time (td)Discrepancy time is the difference in time between the first and the last contact operations between phases or between multiple contacts within a pole.

Closing time (tc)Closing time is the time interval between the instant the closing circuit is energized and the instant when the contacts have touched in all phases.

Opening time (to)Opening time is the time interval between the instant the tripping circuit is energized and the instant the contacts have separated in all phases.

Figure 4 shows a three pole breaker motion analyzer trace showing the various breaker times.

Figure 4: Breaker Contact Timing Chart and DC CurrentMeasurement



Figure 5 shows a simplified connection diagram for a digital timer test set with internal trip and close coil current monitor.

Figure 5: Circuit Breaker Timing Test Connection Diagram

Timing / Time Travel Test Procedure1. Connect the contact monitor / timing leads for phase-A, phase-B and phase-C.

2. Connect the +ve control voltage to the supply input for the trip and close control on the circuit breaker timer test set.

3. Connect the switched Close output of the circuit breaker timer test set to the close terminal (C) of the circuit breaker.

4. Connect the switched Trip output of the circuit breaker timer test set to the trip terminal (T) of the circuit breaker.

5. Set the circuit breaker timer test to monitor the closing and tripping current.

6. Connect the position transducer (LVDT or RVDT) to monitor the main operating rod as required. Refer to the circuit breaker manual for the proper placement of the transducer (if required).

7. Perform a closing and opening operation to set the travel limits of the transducer (if required).

8. Perform an opening operation recording all required parameters.



9. Perform a closing operation recording all required parameters.

4.3 Electrical Testing

Electrical testing consists of:• Insulation resistance test• Dielectric withstand test• Vacuum bottle integrity test• Contact resistance test• Operations test• Power factor test (for maintenance baseline values as required)

4.3.1 Insulation Resistance TestThe insulation resistance test is a DC voltage test conducted at 100% of the rated AC insulation phase-to-ground crest level. The DC equivalent is at 1.414 of the AC RMS rated insulation to ground value.

Note: The above value is higher than the recommended NETA insulation resistance test level.

Note: For indoor circuit breakers, the insulation resistance tests can be combined with the switchgear insulation resistance test with the breaker in the connected position and the main contacts closed. Refer to module 2

The results of the test serves as a preliminary assessment of the primary insulation system to determine if it is should be subjected to the power frequency dielectric withstand test.

Note: Insulation resistance testing is best performed when the ambient temperature is at 20° C.



Figure 6: Insulation Resistance Test Connection Diagram.

Insulation Resistance Test Procedure1. For outdoor circuit breaker, isolate the equipment, apply working grounds to all

incoming and outgoing cables and disconnect all incoming and outgoing cables from the breaker bushing terminals connections. Disconnected cables should have sufficient clearance from the switchgear terminals greater that the phase spacing distance. Use nylon rope to hold cable away from incoming and outgoing terminals as required.

2. For indoor circuit breaker isolate the breaker by placing the circuit breaker in the test / disconnected position or withdraw the breaker from the cubicle cell.

3. Ensure that the equipment is properly grounded.

4. Close the main contacts.

5. Apply the test voltage at the test duration on phase-A terminals with the frame and all other phases grounded.

6. Record test values

7. Repeat step 5 and 6 for phase-B and phase-C



4.3.2 Power Frequency Withstand TestThe 60 Hz dielectric withstand tests are conducted at 75% of the factory dielectric withstand test voltage level of the test values given in Table 4.

The AC test voltage shall have a crest equal to 1.414 times the RMS value specified in Table 4. The wave shape shall be essentially sinusoidal. The frequency shall be within 20% of the rated power frequency. The test voltage is to be increased gradually from zero at a rate no greater than 1000 V per second to reach the required test value and shall be held there for 1 minute. Consult the manufacturer’s manual for limited rate of rise at 500V per second.

Note: For SF6 circuit breakers the dielectric withstand tests are conducted on a per phase basis with the main contacts in the opened and closed positions while the untested phase or pole grounded.

Note: For vacuum circuit breakers, the dielectric withstand test are conducted on a per phase basis with the main contacts closed while the untested phase or pole grounded

Figure7: Vacuum and SF6 Circuit Breakers Dielectric Withstand Test Connection Diagram.



Power Frequency Withstand Test Procedure1. For outdoor circuit breaker, isolate the equipment, apply working grounds to all




4. Close the main contacts for vacuum and SF6 circuit breakers.

5. Apply the test voltage at the test duration on phase-A terminals with the frame and all other phases grounded.

6. Record test values.

7. Repeat step 5 and 6 for phase-B and phase-C.

8. For SF6 circuit breakers only: Open the main contacts.

9. Apply the test voltage at the test duration on phase-A incoming terminal with phase-A outgoing terminal and all other phases grounded.

10.Record test values.

11.Apply the test voltage at the test duration on phase-A outgoing terminal with phase-A incoming terminal and all other phases grounded.


13.Repeat step 9 to 11 for phase-B and phase-C.



4.3.3 Vacuum Bottle Integrity TestThe Vacuum bottle integrity test is a power frequency dielectric withstand tests conducted at 75% of the factory dielectric withstand test voltage level of the test values given in Table 4.

The AC test voltage shall have a crest equal to 1.414 times the RMS value specified in Table 4. The wave shape shall be essentially sinusoidal. The frequency shall be within 20% of the rated power frequency. The test voltage is to be increased gradually from zero at a rate no greater than 1000 V per second to reach the required test value. Consult the manufacturer’s manual for limited rate of rise at 500V per second.

Note: For vacuum bottle integrity test are conducted on a per phase basis across an opened main contact opened while the untested phase or pole grounded. This is a 10 second test for some breaker. Consult the manual to determine the applicable test time duration (10 sec or 1 minute).

Figure 8: Vacuum Bottle Integrity Test Connection Diagram



Vacuum Bottle Integrity Test Procedure1. For outdoor circuit breaker, isolate the equipment, apply working grounds to all




4. Open the main contacts

5. Apply the test voltage at the test duration on phase-A incoming terminals with the frame and all other terminals grounded.





4.3.4 Contact Resistance TestThe contact resistance test is performed by injecting a constant 100Adc current between the incoming and the outgoing terminals on each phase. The voltage drop across the main contact is read using a 4-wire resistance measurement circuit which eliminates the measuring voltage leads wire resistance to obtain the contact resistance value.

The breaker contact resistance test should be measure across the main contacts with the breaker in the closed position. The best lead placement using the 4 wire method is to place the current source leads furthest from the resistance to be measured and the voltage measuring leads closest to the resistance to be measured.

Figure 9: Contact Resistance Measurement Connection Diagram.



Contact Resistance Test Procedure1. Close the main contacts.

2. Connect the +ve current lead at the incoming primary terminal on phase-A and the –ve current lead on phase-A outgoing terminal.

3. Connect the +ve voltage lead at the incoming primary terminal on phase-A and the –ve voltage lead on phase-A outgoing terminal.

Note: Place the voltage leads between the current lead and the main contact.

4. Inject 100 Adc through phase-A main contacts.

5. Record test value.

6. Repeat step 2 to step 5 for phase-B and phase-C

4.3.5 Operational TestThe operational test is conducted with the breaker in the normal operating position. For indoor circuit breakers, it must be inserted in the cubicles in the CONNECTED position. The control power should be present at the breaker controls and all associated control circuits.

Note: The control circuit wiring insulation resistance test must be completed and the control wiring must be free of short circuits and grounds. The power supply polarity, voltage levels and type (AC / DC) should be checked prior to energizing the control circuits and fused properly as per specified drawings.

The operational tests include:• Close and trip test• Trip-free test• Anti-pump test• Anti-slam test• Interlock test



Note: Circuit breaker operations should only be attempted using the designated trip / close push buttons, electrical trip / close control switches / relays or designated control devices. No attempt should be me made to manually disengage any of the mechanical latching devices to initiate a tripping or closing operation.

Close TestThe close test will confirm the closing operation of a tripped breaker from all designated locations. The breaker should Close and the indicators should show Red.

Trip TestThe trip test will confirm the tripping operation of a closed breaker from all designated locations. The breaker should Trip and the indicators should show Green.

Trip-free TestThe trip-free test will confirm the failure of the closing operation when a maintained trip signal is present during a Close command. Since the tripping function overrides the closing function, the presence of a maintained trip signal during a close operation should collapse the closing mechanism pivot point and prevent the operating rod from completing a full closing stroke. Ideally, the main contacts should not touch during a trip-free condition.

Note: To determine the travel motion of the operating rod, a motion analyzer should be connected. This exercise may not be practical for circuit breaker having minimal operating stroke.

Anti-pump TestThe anti-pump test will confirm the operation of the anti-pump circuit. The anti-pump circuit is enabled during the Close command and prevents pumping of the circuit breaker for a failure of the mechanical latch to hold the main contacts in the Closed position. The circuit breaker shall make one failed closing operation without reclosing.

Anti-slam TestThe anti-slam test will confirm the prevention of the closing mechanism to operate when the main contacts are already in the Closed position. The anti-slam function prevents hammering of the main contacts. This function is normally achieved by inclusion of an “b” contact in the closing coil circuit path.



Interlock TestThe interlock test will confirm the blocking of the Close command or automatic initiation of Trip command from the various control devices included in the circuit design.

Control Circuit TestThe control circuit test is to verify the functionality of all circuit paths as per design drawings. These include all breaker controls, indications, alarms, interlocks and other controls.

Operational Test Procedure1. Obtained the most up-to-date as built schematics for the breaker control scheme

and associated control prints.

2. Place the breaker in the normal operating position as connected to the primary bus. Ensure the breaker is isolated / grounded with applicable test and work permit in place.

3. Apply control power to the breaker control circuits and associated control circuits to be tested.

4. Perform Trip and Close command from all designated control location. The breaker should Trip and Close from each control location.

5. With the breaker in the open position, put a maintained trip signal via any one of the tripping devices. Initiate a maintained Close command. Verify that the trip-free function works and anti-pump works correctly and that the breaker did not close and did not pump.

Note: A close watch on the circuit breaker operations is required as multiple tripping and closing operations will occur if the anti-pump function does not work. Remove the Close comand if this situation arises.

6. With the breaker in the Close position, initiate a Close command to the breaker. Verify that the operating mechanism did not operate and that the anti-slam function works correctly.



7. With the breaker in the Open position, initiate each close permissive device individually and initiate a Close command. Verify that the breaker did not operate.

8. With the breaker in the Close position, initiate each automatic tripping devices individually. Verify that the breaker did Tripped.

9. Verify all local and remote indications.

10.Initiate each alarm devices individually. Verify that each device is correctly annunciated and properly designated. Refer to the appropriated alarm schematics for the alarm designations.



5. Power Factor Testing

Note: Power factor testing information has been included in this module since it may be a required to be conducted to establish a baseline reading for future maintenance comparison and trending. Power factor test is similar to the power dissipation / capacitance test which is also a maintenance test, but are not included in this module.

The first power factor test is used to establish the initial baseline reading for which future comparison and trending are made. Normal insulation system degradation and aging are synonymous with a gradual deteriorating test results which can take years to develop while unexpected large sudden changes could be indicative of an insulation system that has quickly degraded or been contaminated which could lead to insulation system failure if not addressed.

5.1 Theory of Power Factor TestingThe power factor test is an AC, 60Hz, voltage application test that is used to measure the capacitive and resistive currents at a fixed voltage. The capacitive current is representative of the capacitive nature of dielectrics while the resistive current is representative of the dielectric losses. Temperature correction is used to normalize all readings to 20° C such that successive test results can be compared and proper trending and analysis can be performed.

The equivalent circuit of an insulation system can be represented by a simple R-C parallel circuit. The resistor represents the dissipated loss and the capacitor represents the insulation capacitance.

E = test voltageIT = total currentIC = capacitive currentIR = resistive currentCP = equivalent parallel capacitanceRP = equivalent parallel resistance



Figure 10: Insulation System Equivalent Parallel Circuit

From the values of IR, IC and IT, the watts loss, power factor, capacitance and resistance of the insulation system can be calculated. A good insulation is characterized by a power factor approaching unity (or a cosine of 90º) as in a pure capacitor and exhibiting a very small watts loss (or a small IR component). A deteriorating insulation system is characterized by a decreasing power factor and an increasing watts loss value.

E = test voltageIT = total currentIC = capacitive currentIR = resistive currentθ = phase angle between E and IT

Figure 11: Vector component of parallel RC circuit.

5.2 Power Factor Test Voltage

Total Insulation SystemThe test is conducted at a voltage level below the operating phase-to-ground stress level.

Table 5: Circuit Breaker Power Factor Test Voltage LevelsBreaker Voltage

Rating(kV)

Test Voltage(kV)1,2

15 kV and above 107.2 and 7.5 5

5 21. Air-magnetic, SF6 and vacuum circuit breakers should be tested at the maximum voltage

selected at the initial test. The initial test voltages are made at a voltage below the corona inception voltage up to the rated operating line-to ground voltage to determine that there is no appreciable increase in watts-loss or power factor is observed to indicate the presence of corona.

2. Air-magnetic, grounded-tank SF6 and vacuum breakers rated at 13.8 kV may be tested at 10 kV for a 10-25% overvoltage providing condition of item 1 are met.

Bushing



Table 6 list the recommended test voltage for bushing of the medium voltage class rated up to 10 kV. Each bushing may have a different rating than the circuit breaker maximum voltage rating which can be found on the bushing nameplate data.

Table 6: Non Condenser Bushing Power Factor Test Voltage LevelsBushing Rating

(kV)Test Voltage

(kV)8.7 kV and above 10

8.7 55.0 54.3 21.2 1

The main function of a bushing is to provide an insulated entrance for an energized conductor into an apparatus tank or chamber. A bushing may also serve as a support for other energized parts of the apparatus.

Bushings used outdoor medium voltage class circuit breakers are typically of the non-condenser type. Non condenser types are:

• Solid core or alternate layers of solid and liquid insulation• Solid mass of homogeneous insulating material (such as solid porcelain)• Gas filled

The primary insulation is contained in a porcelain housing filled with insulating oil or SF6 gas. Some solid bushings may use oil to fill the space between the conductor and inner wall of the porcelain housing.

5.2 Power Factor Test ModeThe basic power factor test set is provisioned with three test leads comprising of the:

• High voltage lead• Low voltage lead• Ground lead

The HV lead is connected to the specimen are where the HV potential is applied. The position of the measuring circuit, relative to the LV lead or the ground lead provides three modes of operation.

• Grounded specimen test



• Guarded specimen test• Ungrounded specimen test

Grounded specimen test measure the total current to the ground lead.

Guarded specimen test does not measure the current in the LV lead.The LV lead is guarded.

Ungrounded specimen test does not measure the current in the ground lead.The ground lead is guarded.

Figure 12: Power Factor operating test mode

Note: Power factor test set may be provided with two LV test leads which can be selectively guarded and grounded. It is beyond the scope of this module to discuss the connection variations and its metering implications.

Note: The power factor test is typically applied to outdoor circuit breakers provisioned with bushing terminals but may be applied to bushingless indoor circuit breakers if required by the customer.



5.3 Circuit Breaker Test ConnectionTable 6 details the connection requirements for testing the MV circuit breakers.

Table 6: Circuit Breaker Power factor Test Mode and Connections1

Test number

Breaker Position

Test Mode BushingEnergized

BushingFloating

BushingUST

All Breakers1 Open GST 1 2 ---2 Open GST 2 1 ---3 Open GST 3 4 ---4 Open GST 4 3 ---5 Open GST 5 6 ---6 Open GST 6 5 ---

Oil Circuit Breakers7 Closed GST 1 & 2 --- ---8 Closed GST 3 & 4 --- ---9 Closed GST 5 & 6 --- ---

Air-Magnetic, Vacuum and Grounded-Tank SF6 (single interrupter)7 Open UST 1 --- 28 Open UST 3 --- 49 Open UST 5 --- 6

Grounded-Tank SF6 (two interrupters in series)10 Closed GST 1 & 2 --- ---11 Closed GST 3 & 4 --- ---12 Closed GST 5 & 6 --- ---

1. For candlestick type SF6 circuit breakers only 2 tests are required per pole. T2 to the HV lead, T1 to the LV lead and T3 grounded.

Circuit Breaker Power Factor Test Procedure1. For outdoor circuit breakers isolate the equipment and apply working grounds

to all incoming and outgoing cables.

For indoor circuit breakers isolate the breaker by placing the circuit breaker in the test / disconnected position or withdraw the breaker from the cubicle cell.

2. For outdoor Circuit breakers disconnect all incoming and outgoing cables from the breaker bushing terminal connections.



Disconnected cables should have sufficient clearance from the circuit breaker terminals greater that the phase spacing distance. Use nylon rope to hold cable away from incoming and outgoing terminals as required.

3. Ensure that the equipment / frame is properly grounded.

4. Close the main contacts.

5. Apply the test voltage on phase-A terminals with the frame and all other phases grounded.



8. Open the main contact.

9. Apply the test voltage on phase-A incoming terminal with phase-A outgoing terminal and all other terminals grounded.


11.Apply the test voltage on phase-A outgoing terminal with phase-A incoming terminal and all other phases grounded.


13.Repeat step 9 to 11 for phase-B and phase-C.

5.4 Bushing Hot Collar Test ConnectionThe hot collar test is used for testing dry-type-solid-porcelain bushings and oil filled bushings. Non-condenser bushings are tested by the hot collar test in the GST mode.

The hot collar test applies an increased voltage stress in the upper region of the bushing below the first skirt (or top petticoat). The upper region is the most probable location for moisture ingress or insulation deterioration.

The conducting collar is drawn tightly around the bushing to ensure intimate contact with the surface. Collar material can be conducting rubber or metallic



materials. The collar is energized while the center conductor is grounded.

Figure 13: Bushing Hot Collar Connection Diagram

Bushing Hot Collar Test Procedure1. For outdoor circuit breakers isolate the equipment and apply working grounds

to all incoming and outgoing cables.

For indoor circuit breakers isolate the breaker by placing the circuit breaker in the test / disconnected position or withdraw the breaker from the cubicle cell.

2. For outdoor Circuit breakers disconnect all incoming and outgoing cables from the breaker bushing terminal connections.

Disconnected cables should have sufficient clearance from the circuit breaker terminals greater that the phase spacing distance. Use nylon rope to hold cable away from incoming and outgoing terminals as required.

3. Ensure that the equipment / frame is properly grounded.

4. Connect the PF test set as per bushing hot collar connection diagram for phase-A incoming terminal.

5. Perform a GST test.

6. Record test values

7. Repeat step 4 to 6 for all other bushings.



6. NETA Circuit Breaker Acceptance Test Procedure

Note: The NETA circuit breaker acceptance testing procedures applicable to the MV class has been condensed and recompiled.

6.1 Visual and Mechanical Inspection

6.1.1 General – Visual and Mechanical Inspection

Note: Consult the manufacturer’s manual for equipment specific instructions.

1. Compare equipment nameplate data with drawings and specifications

2. Inspect physical and mechanical condition.

3. Inspect anchorage, alignment, and grounding.

4. Verify that all maintenance devices, special tools, external gauges /indicators, manual racking handles, breaker lifting carts, umbilical cords are available for servicing and operating the breaker.

5. Verify the unit is clean.

6. Perform all mechanical operation tests on the operating mechanism.• Red “CLOSED” mechanical indicator• Green “OPEN” mechanical indicator• Yellow with black lettering “CHARGED” mechanical indicator• White with black lettering “DISCHARGED” mechanical indicator• Manual release OPEN and CLOSE• Trip-free and anti-pump feature• Racking and mechanism interlocks• Primary and secondary disconnects

7. Inspect accessible bolted connections for high resistance by either• calibrated torque-wrench method or Table 2• low resistance ohm meter

8. Verify cell fit and element alignment.



9. Verify racking mechanism operation.

10.Verify appropriate lubrication on moving current-carrying parts and on moving and sliding surfaces.

6.1.2 Air Circuit Breaker Visual and Mechanical Inspection1. Verify the arc chutes are intact.

2. Inspect moving and stationary contact condition and alignment.

3. Verify arcing and main contact sequence, contact wipe via slow closing if applicable.

4. Verify / inspect puffer action.

6.1.3 Oil Circuit Breaker1. Verify correct oil level in all tanks and bushings.

2. Verify Breather vents are clear.

3. Inspect pneumatic and hydraulic systems.

6.1.4 Vacuum Circuit Breaker1. Perform contact gap / wear measurements as per manufacture’s manual as

required.

6.1.5 SF6 Circuit Breaker1. Verify gas operating pressure shall be within 1% of the indicated pressure

requirements.

2. Perform gas purity and density test if sampling valve is provided. Convert density test to reference temperature at 20°C. Consult manufacturer’s manual for required specifications

3. Operate low pressure gas switched if isolation valve and purge / sampling valve is provided. Confirm operating low pressure setting is as per manufacturer’s manual.

4. Check for leaks if as pressure indicator is below acceptable limits.



Note: The procedure is different than those listed in the NETA standards. The reader is urged to review the NETA standard and adopt those practices that are applicable to their requirements.

6.2 Electrical Test

6.2.1General - Electrical Test1. Perform resistance measurements through bolted connections with a low-

resistance ohmmeter, if applicable.

2. Perform insulation-resistance tests for one minute on each phase with the main contacts closed and the other phase and frame grounded.

Apply voltage at the crest value of the rated maximum voltage

3. Perform a dielectric withstand voltage test on each phase with the circuit breaker closed and the phases not under test grounded. Apply voltage at 75% of the factory power frequency withstand test level for 1 minute.

4. Perform a power-factor or capacitance / dissipation tests on each pole with the breaker open and on each phase with the breaker closed for station and outdoor breakers fitted with bushing terminals as required.

4a.Performed hot collar tests on bushing as required.

5. Perform main contacts resistance tests from pole to pole using a 100 Adc low resistance ohm meter.

6. Perform time-travel analysis on the main operating rod if feasible.

6a.Perform contact timing test and trip / close coil current monitor.

7. Perform a one minute insulation-resistance tests on all control wiring with respect to ground. Apply 500 Vdc for 300-volt rated cable and 1000 Vac for 600-volt rated cable.

For units with solid-state components or control devices that can not tolerate the applied voltage, follow manufacturer’s recommendation.

8. Perform operational test using normal source power:



i. Trip and close breaker with the control switch.ii. Trip breaker by operating each of its protective relays.iii. Confirm proper operation of the breaker’s mechanical / electrical position

indicators.iv. Verify trip-free, anti-pump and anti-slam functions.v. Record as-found and as-left operation-counter readingsvi. Perform minimum pickup voltage tests on trip and close coils in accordance

with manufacturer’s published data as required.

Note: This procedure can be achieved with the use of a suitable capacity variable power supply source but may not always be feasible to perform if the operating coils inrush current is very large. Step 6a coil current monitor test results can be used to determine if portable any portable power supply source has the capacity to deliver the inrush current.

9. Perform instrument transformer test as detailed in module 3.

10.Verify that heaters and anti-condensate circuit and temperature controller are operational.

6.2.2 Air Circuit Breaker Electrical Test1. Measure the blow-out coil resistance.

6.2.3 Oil Circuit Breaker Electrical Test1. Remove a sample of insulating oil for analysis. Sample shall be tested for:

• Dielectric breakdown voltage: ASTM D-877• Color: ASTM D-924• Power Factor: ASTM D-924• Clarity: ASTM D-1554

6.2.4 Vacuum Circuit Breaker Electrical Test1. Perform vacuum bottle integrity test (dielectric withstand voltage) test across

each vacuum bottle with the breaker in the open position. Voltage level applied shall be as per manufacture’s manual.



6.2.5 SF6 Circuit Breaker Electrical Test1. Verify low gas pressure switch alarm indication.

2. Verify low-low gas pressure switch emergency trip operation.

3. Verify extra low pressure block closing function.



6.3 Test Values

6.3.1 Visual and Mechanical

General Test Values – Visual and Mechanical1. Compare bolted connection resistance values to values of similar connections.

Investigate values which deviate from those of similar bolted connections by more than 50 percent of the lowest value.

2. Bolt-torque levels shall be in accordance with manufacturer’s published data. In the absence of manufacturer’s published data, use Table 100.12.

3. Main operating rod travel and velocity curve shall be in accordance with manufacturer’s published data.

4. Operations counter shall advance one digit per close-open cycle.

Note: The preferred arrangement is for the counter to advance during the opening cycle.

Air Circuit Breaker Visual and Mechanical Inspection1. Mechanical and operations and contact alignment / wipe shall be as per

manufacturer’s manual.

Oil Circuit Breaker Visual and Mechanical Inspection1. Oil level shall be as per manufacturer’s manual

Vacuum Breaker Visual and Mechanical Inspection1. Contact gap / wear measurements shall be as per manufacture’s manual.

SF6 Breaker Visual and Mechanical Inspection1. Temperature compensated gas pressure shall be as per manufacturer’s manual.

2. Gas purity and density shall be as per manufacturer’s manual.

6.3.2 Test values - Electrical1. Compare bolted connection resistance values to values of similar connections.

Investigate values which deviate from those of similar bolted connections by more than 50 percent of the lowest value.



2. Insulation-resistance values of circuit breakers shall be in accordance with manufacturer’s published data. In the absence of manufacturer’s published data, use Table 100.1. Values of insulation resistance less than this table or manufacturer’s recommendations should be investigated.

3. Insulation-resistance values of control wiring shall not be less than two megohms.

4. Main contacts resistance values from pole to pole shall be as per manufacturer’s manual.

5. Breaker mechanism charge, close, open, trip, trip-free, anti-pump and anti-slam features shall function as designed.

6. Minimum pickup voltage of the trip and close coils shall conform to the manufacturer’s published data. In the absence of the manufacturer’s published data, refer to Table 100.20.

9. If no evidence of distress or insulation failure is observed by the end of the total time of voltage application during the dielectric withstand test, the circuit breaker is considered to have passed the test.

10.Instrument transformer test values shall be satisfactory as detailed in module 3.

11.Heaters shall be operational.

Air Circuit Breaker Test Values - Electrical1. The blowout coil circuit shall exhibit continuity.

Oil Circuit Breakers Test Values – Electrical1. Insulating liquid test shall be as per table 100.4

2. Power-factor or dissipation-factor values and tank loss index shall be compared to manufacturer’s published data. In the absence of manufacturer’s published data, the comparison shall be made to test data from similar breakers or data from test equipment manufacturers.

3. Power-factor or dissipation-factor and capacitance values shall be within ten percent of nameplate rating for bushings. Hot collar tests are evaluated on a milliampere / milliwatt loss basis, and the results should be compared to values



of similar bushings.

Vacuum Circuit Breakers Test Values – Electrical1. If no evidence of distress or insulation failure is observed by the end of the total

time of voltage application during the vacuum bottle integrity test, the circuit breaker is considered to have passed the test.

SF6 Circuit Breakers Test Values – Electrical1. Pressure switches operating set point shall be as per manufacturer’s manual.



7. Test Set Operational Manual

Breaker Timing Test Set

Power Factor Test Set



8. Circuit Breaker Test Forms

Vacuum Breaker Test Form

SF6 Breaker Test Form







References and Suggested Reading

IEEE C37.04-1999Standard rating Structure for AC High-Voltage Circuit BreakersCopyright © 1999 by the Institute of Electrical and Electronics Engineers, Inc.3 Park Avenue, New York, NY 100-16-5997, USAPDF: ISBN 0-7381-1781-1Print: ISBN 0-7381-1782-X

ANSI / IEEE C37.06-2009AC High-Voltage Circuit Breakers rated on a Symmetrical Current Basis – Preferred ratings and Related Required CapabilitiesCopyright © 2009 by the Institute of Electrical and Electronics Engineers, Inc.3 Park Avenue, New York, NY 100-16-5997, USAPDF: ISBN 978-0-7381-6078-8Print: ISBN 978-0-7381-6079-5

IEEE C37.09-1999Standard Test Procedure for AC High-Voltage Circuit Breakers rated on a Symmetrical Current BasisCopyright © 1999 by the Institute of Electrical and Electronics Engineers, Inc.3 Park Avenue, New York, NY 100-16-5997, USAPDF: ISBN 0-7381-1784-6Print: ISBN 0-7381-1783-8

IEEE C37.010-1999Application Guide for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current BasisCopyright © 2000 by the Institute of Electrical and Electronics Engineers, Inc.3 Park Avenue, New York, NY 100-16-5997, USAPDF: ISBN 0-7381-1828-1Print: ISBN 0-7381-1827-1

Doble Test ProceduresCopyright © 2000 by Doble Engineering Company85 Walnut Street, Watertown, Massachusetts, 02472-4037, USAPN 500-0397



ANSI/NETA ATS 2009American National StandardStandard for Acceptance Testing Specifications for Electrical Power Equipment and SystemsCopyright © 2009 by International Electrical testing Association3050 Old Centre Avenue, Suite 102, Portage, MI 49024, USA

High Voltage Circuit Breakers Design and ApplicationsWritten by: Ruben D. Garzon, Squared D Co.Copyright © 1997 by Marcel Dekker, Inc.270 Madison Avenue, New York, New York 10016ISBN 0-8247-9821-X (hardcover)


Documents

NETA MV Breaker Testing