Training Program 25.01.2014

Electrical Systems & Equipment E&A IC


Project : Ruwais Refinery Expansion Project

TRAINING PROGRAM ONMEDIUM VOLTAGE SWITCHGEAR

EPC


Training Program – Medium Voltage Switchgear

Main Objective:

• Familiarize the participants with the Medium Voltageswitchgear supplied by L&T.

• Operation, Installation & Maintenance Instructions

• Do’s & Dont’s


Content- Day 1Training Program on Medium Voltage Switchgear

Sr.no.

Topic Description TrainingSchedule

1 Introduction to L&T L&T Corporate Film & Brief Overview to L&T EAIC

Day 1Session-1

2 Basic Description Terminologies and equipment used in Switchgear

3 Evolution of MVSwitchgear

Brief overview of Arc quenching techniquesEvolution of Vacuum as an Arc quenching medium.Working principle of Vacuum Interrupter

4 MV Switchgear -Standard,classification andspecification

Details on product specificationsProduct classification as per IEC standards

LUNCH- BREAK5 MV Switchgear –

Panel Construction &operation

Basic Switchgear StructureOperating Sequence / InstructionImportance of Interlocks from Safety / Operation point of view.All in built Interlocks of VCB and earth switch

Day 1Session-2

6 Vacuum CircuitBreaker

Vacuum Circuit Breaker detail overview- VCB Design- Operating Mechanism- Familiarity with the electrical devices- Shutter Mechanism- SDS


Content- Day 2Training Program- Medium Voltage Switchgear

Sr.no.


7 Vacuum Contactor Unit VCU designApplication of VCUOperating Mechanism (Opening & Closing)Familiarity with the electrical componentsShutter MechanismComparison between VCB and VCU

Day 2Session-3

8 Earthing Switch Importance of Earthing.Operating principle of Earthing switchInterlocks with earthing switch

9 Operating Instructions &Interlocks

Operating Sequence of VCB / VCUOperating Sequence of Earth SwitchGeneral Interlocks

LUNCH- BREAK10 Type Tests information Significance of the Type tests as per the IEC standards

IEC 62271-100, IEC 62271-200, IEC 62271-102

Day 2Session-4

11 Installation of spares Mounting & Removal of Closing, Tripping Coils & Spring Chargingmotor

12 Maintenance Schedule Importance of Maintenance as a Preventive measure / Elongation ofproduct life.What to do?When to do?How to do?


Content- Day 3Training Program- Medium Voltage Switchgear

Sr.no.


13 Electrical Components Selection of CT, VT, Surge Arrester, Voltage detecting Indication etcImportance of Above electrical Components

DAY 3Session-5

14 Understanding of ElectricalScheme

Emphasis on understandingWiring SchemeControl CircuitPower CircuitWiring scheme Interlocks

LUNCH- BREAK16 Do’s & Don'ts Good operation and maintenance practices.

Preventive & Corrective Measures to be followed in a Substation.Special DO’s & Dont’s for MV Switchgear

DAY 3Session-617 Q&A Open Forum for Discussion /Queries.


INTRODUCTION TO L&T


L&T Corporate Video


E&A IC : Business Units

Control & Automation Systems (C&A) Metering & Protection Systems (MPS)

Electrical Systems & Equipment (ESE)

• Market leaders in LVsystems in India

• MV SWITCHGEAR• Comprehensive

product range• Manufacturing

facility in 6 countries

• Market leader inSwitchgear in India

• Comprehensive productrange compatible to

International standards• ASTA certified products

• Leading SystemIntegration & Automation

Solution Provider• Solutions based on“Open Architecture”

• SCADA, Drives, Robotics& Process automation

systems

• Leading manufacturerof static energy meters.• Market leader in highend Trivector meters.

• In-house products forpre-paid metering and

AMR

Electrical Standard Products (ESP)


Saudi Arabia• LV Switchgear & MCCs• Integrated Automation

Systems

Mumbai• LV Switchgear & MCCs

• Integrated Automation Systems

Ahmednagar• MV & LV Switchgear

Mysore• Metering & Protection

Systems

Jebel Ali, UAE• Integrated Automation Systems

Australia• MV switchboards

• Swgr Systems

Indonesia• MV Switchgear

• Switchgear Systems

Malaysia• MV Switchboards

E&A IC : Manufacturing Locations

Coimbatore• LV Switchgear & MCCs


Plant Location - Ahmednagar


Plant Location - Ahmednagar

Manufacturing Facilities

In House Test Facilities

Certifications


Model : AE255 NTMake : AMADA , JapanCapacity : 20 T45 Tool StationPunching up to 4 mm MSAuto sheet loader facility

Model : HDS 8025 NTMake : AMADA, JapanCapacity : 80 TBending length up to 2.5 M

Manufacturing FacilitiesCNC TURRET PUNCH PRESS

CNC PRESS BRAKE


Model: TOGU IIIMake: AMADAUsed for Sharpening the Tools

AUTOMATIC TOOL GRINDER

CNC TURRET PUNCH PRESS

Model : EUROMAC 1250Make : EUROMACCapacity : 35 TUsed for Cu / AL bus barand link punching up to10 mm Thick CU



BUS BAR POLISHING MACHINE MIG WELDING MACHINE



SPOT WELDING MACHINE GRINDING AND BUFFINGSTATION



9 tank process - Pretreatment facility

Fully Automated Powder coating line

Robotic painting applicator

PAINTING SET UP



80KV POWERFREQUENCY TESTER IMPULSE TEST LAB

Testing Facilities


VCB TESTING TROLLEYSECONDARY INJECTIONTROLLEY

Testing Facilities


PANEL TESTING TROLLEY CONDUCTIVITY METER

Testing Facilities


Painting Thickness Meter

Push Pull MeterLug Pull Tester

Surface Plate & MeasuringInstrument

Testing Facilities


Various In-House Type Tests

• Partial Discharge• Lightning Impulse• Corrosion resistance• Temperature Rise• Primary Injection

PARTIAL DISCHARGETEMPERATURE RECORDER

Testing Facilities


Quality Systems

• ISO 9001 - 2008 - BV

• ISO 14001 - BV

• OHSAS 18001 - BV

Certifications


DESCRIPTION OF MV Equipment



Introduction to Switchgear

A switch is simply a means of opening orclosing the current path in an electriccircuit.

• There is no special opening conditionfor short circuit or other fault.

SWITCH

A fuse is used for over current and shortcircuit protection.

A fuse is a part of the circuit whichconsists of conductor which melts easilyand breaks the connection when electriccurrent exceeds the predetermined value.

• Fuse has to be replaced after everyFault.

FUSE


The circuit breaker is a device which

• Makes or breaks a circuit either manually orby remote control under normal conditions

• Breaks a circuit automatically under faultconditions


CIRCUIT BREAKER


• Insulators - To insulate equipment from ground andother phases.

Busbar - To allow multiple connections from onefeeder to another feeder.

• Surge Arrester – Surge Arrester are the primaryprotection to make the circuit device immune todifferent types of over voltages and spikes eitheratmospheric or switching. Surge arrester are generallyconnected in parallel with the equipment to beprotected to divert the surge currents. A properlychosen and installed arrester is to be regarded aspractically maintenance free during its life time.



• CT – Current Transformer are instrument transformer that are

used to supply a reduced value of current to meters, protective

relays and other instrument. CT’s provide isolation from the high

voltage primary , permit grounding of the secondary for safety

and step down the magnitude of the measured current to a

value that can be safely handled by instruments

• CBCT - The core-balance CT (or CBCT) is normally of the ring

type, through the centre of which cable is passed that forms the

primary winding. An earth fault relay, connected to the

secondary winding, is energized only when there is residual

current in the primary system



• Voltage Transformers - Transformers which convert high

voltages into measurable and standardized voltages.

These are then proportional and in-phased to the primary

signal. They are intended to supply electrical measuring

instruments, meters, relays or other electrical devices.

Furthermore the connected measuring and protective

devices are electrically insulated against live parts.

• Voltage Detecting Unit – To detect voltage presence on

bus or cable side

• Capacitive Voltage Detector – To sense the voltage on

Busbar



Brain = Relay

Eyes, Ears, Nose &Skin =

CTs, VTs

Hands & Legs=

Circuit Breakers

Protection System Analogy


Relay Issues TripCommand To

Breaker

Sensed byInstrument

Transformers &communicated to

Relay

Breaker Trips& Clears Fault

Protection System Analogy

FAULT


Introduction to MV SWITCHGEAR



It is the generic term including the entire range of switching devices and theircombination with associated control, measuring, protecting, and regulatingequipment.

• Carrying the normal load current

• Making or breaking the normal load current

• Clearing the fault current (for which sensing devices like CT, PTand various relays are employed) Assemblies containing electrical switching,protection, metering and management devices

• Used in three-phase, high-power industrial, commercial and utilityapplications

• Covers a variety of actual uses, including motor control, distribution panelsand outdoor switchyards

• The term "switchgear" is plural, even when referring to a single switchgearassembly (never say, "switchgears")


SWITCHGEAR


Evolution of MV SWITCHGEAR



ARC Extinction Theory

When two current contacts just open, an arc bridges the contact gapthrough which the current gets a low resistive path to flow so there will notbe any sudden interruption of current.

The intensity of arc column depend up on the presence of ionized mediabetween separated electrical contacts, hence, special attention should begiven in reducing ionization or increasing deionization of media betweencontacts.

That is why the main designing feature of circuit breaker is to providedifferent pressure control methods, cooling methods for different arc mediain between circuit breaker contacts.


Oil is outdated in MV switchgear as insulating material because of firerisk and its susceptibility to contamination (moisture and by-productsafter switching). The maintenance requirements with its related costsalso plays a negative role in the application of oil.

BULK OIL CBOil is used as arc quenching media as well as insulating media between currentcarrying contacts and earthed parts of the breaker.

MINIMUM OIL CBA Minimum Oil circuit breaker places the interrupting unit in insulatingchamber at live potential. The insulating oil is available only in interruptingchamber.The features of designing MOCB is to reduce requirement of oil, andhence these breaker are called minimum oil circuit breaker.

OIL CIRCUIT BREAKER


AIR BLAST CB

Air can be considered outdated as arc-quenching medium, due to therelatively bulky volumes needed, sound aspects when operating andsensitivity for moisture.

Advantages Disadvantages

There is no chance of fire hazard causedby oil.

In order to have frequent operations, it isnecessary to have sufficiently highcapacity air compressor.

Arc quenching is much fasterduring operation of air blast circuit breaker.

Frequent maintenance of compressor,associated air pipes and automatic controlequipment is also

As the duration of arc is smaller , so lesseramount of heat realized from arc to currentcarrying contacts hence the service life ofthe contacts becomes longer.

Due to high speed current interruptionthere is always a chance of high rate ofrise of re-striking voltage and currentchopping.

Requires much less maintenancecompared to OIL Circuit Breaker

There also a chance of air pressureleakage from air pipes junctions.


The use of SF6 as an interrupting is not ecofriendly and advancedtechnology solutions like vacuum is available for upto 52KV. Howeverfor extra high voltages beyond this value it still remains the mostpractical solution.

Advantages Disadvantages

SF6 is a gas with good insulating properties,Have High dielectric strengthcolorless, odorless, non-toxic and non-flammable

SF6 is a potent greenhouse gas and should notbe released to the atmosphere.

SF6 molecule is electronegative, it providesexcellent insulation after extinction.

Density approximately five times that of air.

SF6 gives an excellent dissipation of heatwhich is cooling the arc and which is importantaround the zero crossing

Although pure SF6 is non-toxic, the by-products after arcing are extremely toxic formaintenance workers (in case of leakage).

Low force needed for contacts pressure SF6 arc byproducts (S -2 F-10) are hazardouswaste requiring special care for disposal.

Requires much less maintenance comparedto OIL & AIR Circuit Breaker

Special attention shall be given when theswitchgear has to be cleared at the end of itslife.

SF6 Circuit Breaker


Vacuum as an Arc quenching media have a number of attractive features like beingmaintenance-free, compact and environmentally friendly.

Other important features are:

• Large operation reliability: Because of its simple construction, the number ofcomponents is small (approximately 50 percent less than a comparable SF6 oroil circuit breaker).

• Small amount of operating energy. Due to the small stroke (≈8-12 mm) of thecontacts and the light weight of the accelerating mass, the required operatingforce is low. Consequently, the operating mechanism is of a very simple design.

• Low arcing voltage. Because of the low arcing voltage (≈30 V) the energy inthe arc is limited.

• Environmentally friendly: no danger of explosion and/or fi re, only little noisewhen operated.

• Excellent interrupting characteristics: arc duration below 10 ms

• Better Performance: Switching Life more than 3 times of that of a SF6 CB.

Vacuum Circuit Breaker

Vacuum Interrupter


MV SwitchgearStandard, Classification & Specification



IEC 62271-200:High-voltage switchgear and controlgear

AC metal-enclosed switchgear and controlgear for rated voltages above1 kV and up to and including 52 kV


Alternating-current circuit-breakers


Alternating Current Disconnectors and Earthing Switches

Compliance to IEC Standards


Product Classification

• Partition Metallic Class• (Metal Partitioned Compartment)• Partition Metallic Class• (Metal Partitioned Compartment)PMPM• Mechanical Endurance Class• (10,000 Mechanical Operations)• Mechanical Endurance Class• (10,000 Mechanical Operations)M2M2• Electrical Endurance Class• (Highest Breaking Capacity class for MV Switchgear)• Electrical Endurance Class• (Highest Breaking Capacity class for MV Switchgear)E2E2• Capacitive Switching Class• (Least chance of restriking during Capacitive Switching)• Capacitive Switching Class• (Least chance of restriking during Capacitive Switching)C2C2• Degree of Protection• (Ingress Protection against External agents)• Degree of Protection• (Ingress Protection against External agents)IP4XIP4X• Loss of Service Continuity Test• (Continuity access from one compartment to another)• Loss of Service Continuity Test• (Continuity access from one compartment to another)LSC-2BLSC-2B


Air insulated Switchgear

Vacuum Circuit BreakerPanel- VH1H12kV, 630A, 25kA

12kV, 1250A, 25kA

12kV, 2000A, 25kA

12kV, 2000A, 40kA

12kV, 3150A, 40kA

12kV, 3150A, 50kA

Vacuum Circuit BreakerPanel- VH1H12kV, 630A, 25kA

12kV, 1250A, 25kA

12kV, 2000A, 25kA

12kV, 2000A, 40kA

12kV, 3150A, 40kA

12kV, 3150A, 50kA

Vacuum ContactorUnit Panel2- Tier Design3.6kV, 400A, 50kA7.2kV, 400A, 40kA


AIS - 12 kV VCB Panel – up to 25kAType Designation VHIH

Voltage Upto 12 kV

Impulse withstand voltage 75 kVp

One minute power frequencywithstand voltage

28 kV rms

Frequency 50 Hz

Normal current Upto 1250 A

Short circuit breaking current25kA

63kAShort circuit making current

Duration of short circuit withstand 1 sec

Degree of Protection IP 41


AIS - 12 kV VCB Panel –31.5, 40 & 50kA

Type Designation VHIH

Voltage Upto 12 kV


One minute powerfrequency withstandvoltage

28 kV rms

Frequency 50 Hz

Normal current Upto 3150 A

Short circuit breakingcurrent 31.5kA

80kA

40kA

100kA

50kA

125kAShort circuit makingcurrent

Duration of short circuitwithstand

1 sec



AIS – 7.2 kV 2-Tier VCU PanelType Designation VHIH

Voltage3.6 kV 7.2 kV


One minute power frequencywithstand voltage

20 kV rms

Frequency 50 Hz

Normal current 400A

Short circuit breaking current40kA 50kA

Duration of short circuitwithstand

1 sec



Panel SpecificationParameters Rating / Description

System earthing Low Resistance Earthing

Insulation Level As per the System Voltage

Design Ambient 40 deg C

Auxiliary Supply-1 110 V DC

Auxiliary Supply-1 240 V AC

VCB Spring Charging Motor Supply 110V DC

Closing Coil Supply 110V DC

Trip Coil Supply 110V DC

Panel Space Heater Supply 240V AC, 50Hz

Plug & Socket Supply 240V AC, 50Hz

Panel Illumination Supply 240V AC, 50Hz

Power Cable Entry Rear Bottom

Auxiliary Control Supply Cable Front ( for 25kA Panels)Rear (for 31.5kA, 40kA & 50 kA Panels)


Scope of Supply

Board Details VCU400A

630A(25kA)

1250A(25kA)

2000A(25kA)

2000A(40kA)

3150A(40kA)

4000A(50kA)

SRNO

BOARDNO

NO. OFPANELS

QTY

1 MYB0230 31 20 3

2 MYB0231 12 7 3

3 MYB0232 33 25

4 MYB0233 37 49 3 3

5 MYB0234 45 . 34

6 MYB0235 4 2

7 MYB0236 22 15

8 MYB0237 17 14 3

9 MYB0238 16 11

10 MYB0239 19 13

TOTAL 236 70 3 2 3 84 6 37


MV Switchgear – Panel Construction



Type VHIH switchgear is completely metal-clad (LSC2B) and compartmentalized.

The switchgear is fully assembled, wired-up and tested in the factory beforedelivery.

The VHIH panel is fabricated from high grade pickled and oiled steel sheets,which is chemically treated before painting to provide adequate protectionagainst corrosion and weathering.

The cubicle parts are Powder coated process which provides optimum protectionagainst corrosion and weathering.

The paintwork is tested to withstand 1000 hours in a 5% salt spray.

Panel Construction


Panel Construction

The Panel consists of fourcompartments

• Circuit breaker compartment

• Busbar compartment

• Cable & CT compartment

• Low voltage compartment


Circuit breaker Compartment

The circuit breaker compartment contains a withdrawablevacuum circuit breaker which moves on two in-built rails.

It can be transferred between the Connected and Testpositions of circuit breaker compartment using a RackingHandle with the door closed.

In the Connected /service position, the moving upper andthe lower contact arms of the VCB engages with the fixedcontacts connected to the busbars and the outgoingcircuit respectively.

Shutters operated by the VCB movement in the Test/Disconnected positions, separates the contact arms andtheir fixed contacts.

These shutters prevent access to the fixed contacts,while in isolated position.


Cable Compartment

• No live parts are located less than 300 mmabove floor level.

• The cable termination height is well above floor• level, and generous space is provided for• terminating power cables.

• This ensures a higher bending radius as well• as reduces tension on the terminals.

• The cable chamber also houses the CT and the earthing Switch and main earthbusbar.

• The Gland Plate is fitted at rear bottom of cable compartment. The cable isaccessible from rear of the cubicle by opening the cable compartment covers.

• All CT, CBCT, fixed type VT, Surge Arrestors , Earth Switch are mounted here.

• Anti-condensation Space Heater along with the thermostat to keep moisture away.

• Pressure relief flaps are provided at top.

• Earthbar running throughout the switchboard


Busbar Compartment

Busbar Bushing / Fixed contacts isconnected to breaker.

The busbar extends from one Compartmentto the adjacent.

All the busbar joints are covered with PVCBoots.

Main busbar extensible at both ends

Main Busbars Boot


Low Voltage Compartment

The low voltage compartment contains theequipment viz.

• Fuses / MCBs• Control terminals• Protective relays• Indicating lamps• Meters• Push buttons• Control switches• Illumination Lamp

These equipment operating on Auxiliary Supplyvoltage are mounted on LV compartment door andinside LV Compartment


Arc Deflector / Gas Duct

Pressure relief flaps are provided at the top portion of the panel to ensuresafety to the operator in the event of an internal arc fault

The Arc Deflectors / Gas Duct at the top will ensure that the ionized gases aresafely evacuated


Shutter Mechanism

Shutter Operation

• Metallic Shutters covers the Fixed contactsin the VCB compartment.

• Opening / Closing of Shutters is actuatedwith the movement of the VCB.

• Shutters for Fixed contacts on Busbar andCable side can be padlocked individuallyduring maintenance.

• Metallic Shutters are earthed.


Shutter Mechanism- BusbarShutter Operation - Busbar

• Figure-1 shows the stud which actuatesthe movement of the Shutter Assembly(figure-2) in the VCB Compartment onLHS.

• Figure-3 shows the Busbar shutteropened.

Figure-1

Figure-2 Figure-3


Shutter Mechanism- CableShutter Operation - Cable

• Figure-4 shows the stud which actuatesthe movement of the Shutter Assembly(Figure-5) in the VCB Compartment onRHS.

• Figure-6 shows the Cable shutteropened.

Figure-4

Figure-5 Figure-6


Control Circuit Plug Arrangement

A removable plug at the panel connects these controlwires to the fixed wiring at the metering compartment.Ensure that the plug makes full connection beforefastening the clasp as shown below figure

The breaker can only be racked intothe CONNECTED position when thesecondary control plug is inserted.

Control circuit plug can be insertedby moving the Red leverDownwards.

Control Plug

Control PlugArrangementon VCB


VACUUM CIRCUIT BREAKER



Vacuum Circuit Breaker- DesignHorizontal Isolation

The mating of the contacts of the VCB is inhorizontal direction

Horizontal Draw-out out Type

The VCB Truck can be drawn out of the panelhorizontally.

Truck Mounted Design

The VCB mechanism is mounted on the truck(trolley).


VACUUM CIRCUIT BREAKER- Front


VACUUM CIRCUIT BREAKER- Rear


VACUUM CIRCUIT BREAKER- Mechanism

AuxiliarySwitch

ClosingSpring

Closing SpringCharging Motor

TrippingSpring

OperationCounter

Trip Coil

ClosingCoil


VCB Manual Operation

Note - Confirm that the circuit breaker is in the “OPEN” state indicated as bythe OFF position at the ON / OFF indicator.

a) Charging Operation

Manual charging can be performed in the event that the motor malfunctions.

The CHARGED/DISCHARGED indicator will change its color from white(DISCHARGED) to yellow(CHARGED), indicating that the closing spring isfully charged.

Push the CLOSE button to initiate the close operation. The indicators on thebreaker will now read CLOSED and DISCHARGED.

Push the TRIP button to initiate the opening operation. The indicator will nowread OPEN.


VCB Electrical Operation

When the power supply is connected to theoperation circuit, energy from the motor isstored in the closing spring.

When the spring charging is complete, thelimit switches opens and the motor stops.

The indicator shows CHARGED condition,confirming that the spring charging iscomplete.

As the closing spring may be released by aclosing signal, the limit switch closes whenthe closing operation terminates, causingthe motor to run.

A) Charging Operation Spring


B) Closing Operation

When the closing coil is excited by a closingsignal, the closing catch is released and theclosing cam is rotated by the closing spring,which in turn rotates the main shaft.

The main shaft drives the vacuum interruptersthrough the wipe spring, and the circuit breakercloses.

CAUTION: DO NOT repeat the closingoperation once the breaker is closed.

C) Tripping Operation

When the tripping coil is excited by a tripping signal, the trippingcatch is released, and the breaker is opened by the openingspring.

VCB Electrical Operation


A) Excellent Breaking Performance

B) High Reliability

C) Safety for personnel and operating safety

D) Minimized Maintenance

E) Compact & Light

VCB Features

VCB Safety Interlocks• VCB cannot be engaged or withdrawn unless it is in open

condition

• VCB can only be closed or opened if it is in engaged orisolated position (and in between)

• Interlocking with earth switch

• Interlocking with cubicle door


VCU Design and Application

VacuumContactor Unit


VCU Construction


HT FuseJaw

Contacts

VacuumInterrupter

Cradle

Shutter


Application of VCU

Main application in motor switching duty like Pumping stations

Cranes, Forward Reverse operations in mines, Lift Hoists

Transformer Switching

Neutral grounding of Generators, Operations of soft starters

Switching of Reactor Capacitor switching for reactive powercompensation


A) Excellent Breaking Performance

B) No Surge Protection Required

C) Safety for personnel and operating safety

D) Minimized Maintenance

E) Compact & Light

F) Low Power consumption

G) Conformity to Insdustrial Standard

VCU Features


Difference between VCB & VCU


Vacuum CircuitBreaker



CHARACTERISTIC CIRCUIT BREAKER CONTACTOR with FUSES

Continous Currents High (1200A, 2000A. 3000A, 4000A)Moderate (400A enclosed- NEMA size H3, or 720Aenclosed size H6)

Switching Capability

Switching current from very low(magnetising) values to full systemshort-circuit current

# Switching current from very low (magnetising)values to interrupting capability of vacuum contactorwithout fuses ( at least 10 x continous rating)

# Fuses operate for currents higher than theinterrupting capability capability of vacuumcontactor alone, up to the interrupting capcity of thefuse

Endurance-Mechanical

High (typically 10,000 operations) ( referto ANSI/IEEE C37.06) & IEC 62271 Very high, 10,00,000 to 25,00,000 operations

Endurance-Electrical High Very high.

# for Vacuum, typically 10,000operations at rated continous current

#Switching continuous current, 400,000 operationsfor 400A & 200,000 operations for 720A

# for Vacuum, typically 30 to 100operations at full short-circuit rating

Switching short-circuit current, endurence data notestablished in NEMA or UL standards; short-circuitcurrent interruption requires replacement of current-limiting fuses

Applicationlimitations

Not appropriate for very high endurenceapplications Well suited for very frequent switching operatioons

OperationsElectrically operated (manual operationfor maintance or emergency) Electrically operated only


CHARACTERISTIC CIRCUIT BREAKER CONTACTOR with FUSES

Control Scheme Mechanically latched- circuit breaker remainsclosed on loss of system voltage

# Usually magnetically held-vacuum contactoropens on loss of system voltage; vacuumcontactor will close automatically on systemvoltage return with two-wire control, manualrestart required on system voltage return withthree-wire control

# Latched contactors are also available

Overcurrent/ short-circuit protection Requires protective relays

Requires protective relays for overloadprotection and current limiting fuses for short-circuit protection

short-circuit let-through energy

High (three to five cycles or more of short-circuitcurrent)

Low (current-limiting fuses interrupt in 1/4 cyclefor highest short-circuit currents, and peakmagnitute is limited)

Remote operation Well suited Well suited

Control power Control power needed for protective relays, circuitbreaker operation and space heaters ( if present)

Control power usually provided by controlpower transformer (CPT) incorporated in thecontroller

Construction # Drawout, if metal-clad (ANSI/IEEE c37.20.2) #Stationary, if metal-enclosed (ANSI/IEEE C37.20.3) Drawout or Stationary

Space requirement # Large enclosure# NEC required workspace equal

# Smaller enclosure# NEC required workspace equal# Rear access not required

Purchase cost Relativally high Moderate

MaintenanceMedium (long maintenance intervals, need toclean insulation)

Low (simple mechanism, need to cleaninsulation, replace fuses)



Conclusion

Typical loads include transformers, capacitors, larger motors,generators or distribution feeders,

Ratings required exceed those of vacuum contactors 400A at upto7.2kV

Continuous load current is high ( larger transformer and largermotors)

Switching is not very frequent (e.g. weekly or monthly) high endurance(1000’s of operations) is satisfactory

Process continuity critical (e.g.no time for fuse replacement)

Circuit breakers are favored when

Vacuum Contactor Unit are favored when

Typical loads include motors or small transformers

Continuous load current is low or moderate ( e.g. smaller motor ortransformer )

Switching is very frequent (e.g. daily or several times per dayweekly or monthly) very high endurance (100000’s of operations) isneeded

Process continuity is compatible with fuse replacement time


Earthing Switch



Earthing Switch

Window forVCB racking

Handle

Window forEarthingSwitch

Operation

Rotate Earth switch Handle as perInstruction given . Do Not Rotatein Reverse Direction. It MayDamage the interlocks.


Earthing Switch

Earth SwitchOperation –

OFF Position

Earth SwitchOperation –ON Position

Earth SwitchHandle

Insert ESWHandle till Red

Mark


Earthing Switch & Interlocks

Basic Interlocks which are commonly provided in a MV switchboard. VCB can not be racked in or connected to service position from test

position when;a. VCB in closed position b. Without control Plug.c. Earth switch in closed position. d. Door is opened.

While VCB in service position;a. Earth switch can not be closed b. Control plug can not be removed.c. Closed VCB can not be racked out. d. VCB door can not be opened.

While VCB in intermediate position;a. VCB can not be closed b. Control plug can not be removed.

While VCB in Test position;a. VCB door can be opened b. ESW can be operated.c. Control plug can be removed and inserted.

VCB only can be opened and closed while in test and service position.

These are equipped with a snap action spring device which ensures anindependent closing speed. They can make and withstand short-circuitcurrents


Operating Sequence/ Instructions



VCB Rack-In Operation – Closed Door

1. ENSURE THE FOLLOWING BEFORERACK-IN;

a VCB IS IN ‘TEST’ POSITIONb CONTROL PLUG IS PROPERLYCONNECTED TO VCB.

c VCB IS IN ‘OPEN’ CONDITION.d. EARTH SWITCH IS OFF


a VCB IS IN ‘TEST’ POSITIONb CONTROL PLUG IS PROPERLYCONNECTED TO VCB.

c VCB IS IN ‘OPEN’ CONDITION.d. EARTH SWITCH IS OFF

2. CLOSE THE DOOR ANDTIGHTEN THE CAPTIVESCREW.


3. LIFT THE ‘LEVER A’, OPENTHE FLAP OF ‘SOCKET FORVCB RACKING HANDLE’, ANDINSERT THE VCB RACKINGHANDLE,

3. LIFT THE ‘LEVER A’, OPENTHE FLAP OF ‘SOCKET FORVCB RACKING HANDLE’, ANDINSERT THE VCB RACKINGHANDLE,

5. ROTATE THE RACKINGHANDLE CLOCKWISE UNTIL;

a VCB POSITION INDICATORSHOWS ;SERVICE’ ANDb MECHANICAL RESISTANCE ISFELT TO ROTATE HANDLE

5. ROTATE THE RACKINGHANDLE CLOCKWISE UNTIL;

a VCB POSITION INDICATORSHOWS ;SERVICE’ ANDb MECHANICAL RESISTANCE ISFELT TO ROTATE HANDLE

6. REMOVETHE RACKING

HANDLE.

6. REMOVETHE RACKING

HANDLE.


VCB Rack- Out Operation – Closed Door

1. ENSURE THE FOLLOWING BEFORE RACK-OUT;

a VCB IS IN ‘OPEN’ CONDITION.b VCB POSITION INDICATOR SHOWS‘SERVICE’ POSITION.


a VCB IS IN ‘OPEN’ CONDITION.b VCB POSITION INDICATOR SHOWS‘SERVICE’ POSITION.

2. LIFT THE ‘ LEVER A’. OPEN THEFLAP OF SOCKET FOR VCBRACKING HANDLE AND INSERT THEVCB RACKING HANDLE

2. LIFT THE ‘ LEVER A’. OPEN THEFLAP OF SOCKET FOR VCBRACKING HANDLE AND INSERT THEVCB RACKING HANDLE

3. ROTATE THE RACKING HANDLE ANTICLOCKWISEUNTIL

(a) THE HANDLE STARTS ROTATING FREELY AND

(b) VCB POSITION INDICATOR SHOWS ‘TEST’

3. ROTATE THE RACKING HANDLE ANTICLOCKWISEUNTIL

(a) THE HANDLE STARTS ROTATING FREELY AND

(b) VCB POSITION INDICATOR SHOWS ‘TEST’

4. REMOVE THERACKING HANDLE.

4. REMOVE THERACKING HANDLE.


VCU Rack-In Operation – Closed Door


a VCU POSITION INDICATIONS SHOWS‘DCON’b CONTROL PLUG IS PROPERLYCONNECTED TO VCU.

c VCU IS IN ‘OPEN’ CONDITION.d. EARTH SWITCH IS OFF


a VCU POSITION INDICATIONS SHOWS‘DCON’b CONTROL PLUG IS PROPERLYCONNECTED TO VCU.

c VCU IS IN ‘OPEN’ CONDITION.d. EARTH SWITCH IS OFF



3. OPEN THE VCU OPERATINGWINDOWAND INSERT THEVCU RACKING HANDLE

3. OPEN THE VCU OPERATINGWINDOWAND INSERT THEVCU RACKING HANDLE

4. PULL THE VCU HANDLE UP TODRIVE THE VCU TO CONNECTEDAND EARTH OFF POSITION

5. CHECK THE VCU POSITIONINDICATOR FOR ‘CON’ POSITION

4. PULL THE VCU HANDLE UP TODRIVE THE VCU TO CONNECTEDAND EARTH OFF POSITION

5. CHECK THE VCU POSITIONINDICATOR FOR ‘CON’ POSITION

6. REMOVETHE RACKINGHANDLE AND

CLOSE THEVCU

OPERATINGWINDOW.

6. REMOVETHE RACKINGHANDLE AND

CLOSE THEVCU

OPERATINGWINDOW.


VCU Rack- Out Operation – Closed Door


a VCU POSITION INDICATION SHOWS ‘CON’b VCU IS IN OPEN CONDITION


a VCU POSITION INDICATION SHOWS ‘CON’b VCU IS IN OPEN CONDITION

2. OPEN THE VCU OPERATINGWINDOW AND INSERT THE VCURACKING HANDLE

2. OPEN THE VCU OPERATINGWINDOW AND INSERT THE VCURACKING HANDLE

3. PUSH THE HANDLE DOWN TO BRING THE VCU TODISCONNECTED POSITION AND EARTH SWITH ONPOSITION.

4. CHECK THE VCU POSITION INDICATOR FOR‘DCON’ INDICATION

3. PUSH THE HANDLE DOWN TO BRING THE VCU TODISCONNECTED POSITION AND EARTH SWITH ONPOSITION.

4. CHECK THE VCU POSITION INDICATOR FOR‘DCON’ INDICATION

4. REMOVE THERACKING HANDLE ANDCLOSE THE VCUOPERATING WINDOW.

4. REMOVE THERACKING HANDLE ANDCLOSE THE VCUOPERATING WINDOW.


Earth Switch Operation

1. ENSURE THAT VCB IS AT‘DISCONNECTED’ & ‘TEST’ POSITION.1. ENSURE THAT VCB IS AT‘DISCONNECTED’ & ‘TEST’ POSITION.

2. MOVE THE ‘LEVER B’ TO LEFT TOOPEN THE COVER OF EARTH SWITCHOPERATING MECHANISM.

2. MOVE THE ‘LEVER B’ TO LEFT TOOPEN THE COVER OF EARTH SWITCHOPERATING MECHANISM.

3. INSERT THE EARTHSWITCH OPERATINGHANDLE.’

3. INSERT THE EARTHSWITCH OPERATINGHANDLE.’

4. PULL THEHANDLE UPWARDTO ‘SWITCH ON.

4. PULL THEHANDLE UPWARDTO ‘SWITCH ON.

5. REMOVE THERACKING HANDLE.5. REMOVE THERACKING HANDLE.


GeneralInterlocks



General Interlocks

SDS Interlock (Control Plug)VCB cannot be Racked in unless the Control plug is fitted.Ensure that SDS is Plugged in during VCB / VCU during Rack In.

SDS Interlock (Control Plug)VCB cannot be Racked in unless the Control plug is fitted.Ensure that SDS is Plugged in during VCB / VCU during Rack In.

VCB Positive InterlockVCB cannot be engaged or withdrawn unless it is in OPEN positionVCB Positive InterlockVCB cannot be engaged or withdrawn unless it is in OPEN position

VCB Negative InterlockVCB cannot be operated unless it is in Service or Test position. IeVCB cannot be closed when in intermediate position.

VCB Negative InterlockVCB cannot be operated unless it is in Service or Test position. IeVCB cannot be closed when in intermediate position.

Closed Door OperationsAll operations are behind closed door.In any case VCB/VCU should not be operated in open doorcondition

Closed Door OperationsAll operations are behind closed door.In any case VCB/VCU should not be operated in open doorcondition

Earth Switch InterlockVCB cannot be engaged when Earthing Switch is CLOSEDEarthing switch cannot be closed when VCB is engaged

Earth Switch InterlockVCB cannot be engaged when Earthing Switch is CLOSEDEarthing switch cannot be closed when VCB is engaged


General InterlocksOTHER INTERLOCKS

1. Racking in & racking out of VCB & VCU is not possible unless it is OFF

2. VCB/VCU can be closed only when it is in service or test position

3. VCB/VCU cannot be operated while it is in intermediate position

4. VCB/VCU cannot be racked in or operated unless control plug is inserted

5. VCB/VCU can be withdrawn only when control plug is removed

6. It shall not be possible to remove control plug while the VCB/VCU is inIntermediate or service position

7. Control Plug can be removed only when VCB/VCU is in Test DisconnectedPosition

8. VCB/VCU can be operated / moved from Disconnected position/ test position onlywhen Earth Switch is in OPEN condition

9. Earth Switch can be operated only when VCB/VCU is in test/disconnected position

10. Earth Switch cannot be operated if VCB/VCU is in service / intermediate position.Access to Earth switch Operating Handle is Blocked.


General Interlocks

OTHER INTERLOCKS

11. VCU trips automatically if VCU fuse is blown

12. Rating error preventer is provided to prevent rack in with different rating ofVCB/VCU

13. Door can be opened only when VCB/VCU is in test position

14. Door cannot be opened if VCB/VCU is in service position

15. Safety shutter opens when the VCB contactor is racked into service position

16. Safety shutter closes automatically once VCB/VCU is withdrawn from Serviceposition

17. VCB/VCU of same rating can be interchanged

PAD LOCKING FACILITY

1. VCB Door Handle

2. Safety Shutter


Type Test Details



Type tests

Short Time Current Withstand & Peak WithstandShort Time Current Withstand & Peak Withstand

Lightning Impulse Voltage WithstandLightning Impulse Voltage Withstand

HV Power Frequency Dry Withstand TestHV Power Frequency Dry Withstand Test

Temperature Rise Test & Measurement of ResistanceTemperature Rise Test & Measurement of Resistance

Degree of Protection TestDegree of Protection Test

Internal Arc Fault Withstand TestInternal Arc Fault Withstand Test

Mechanical Operation & Integrity of Interlocks TestMechanical Operation & Integrity of Interlocks Test

Basic Test DutyBasic Test Duty


Type testsShort Time Current Withstand & Peak Withstand

1. STC = Fault current duration in kA for 1 Sec / 3 Sec (rms)

2. Peak Current = 2.5 times (rms) for 50 Hz Application

3. Peak Current = 2.6times (rms) for 60Hz Application

4. Followed by supplementary test of contact resistance measurement & dry powerHV Withstand capacity test

HV Power Frequency Dry Withstand Voltage (PFWV)

1. Short Duration (1 minute) test voltage 2 to 4 times the rated maximum Voltage

Eg – For rated max. voltage 12 kV = 28kV rms (as per IEC standard)

Lightning Impulse Withstand Voltage (LIWV or BIL)

1. A fast rising voltage impulse 4 to 12 times rated Maximum voltage

2. Rise time = 1.2 microseconds and decay to 50% in 50 microseconds

Eg – for rated max voltage 12kV = 75kV peak (as per IEC standard)


Type testsMechanical Operation

Switching devices and withdrawable parts shall be operated 50 times,

Removable parts inserted 25 times and removed 25 times to verify satisfactoryoperation of the equipment

Ingress Protection - IP

Extent of protection provided by an enclosure, partition or shutter if applicable, againstaccess to hazardous parts, against ingress of solid foreign objects and/or ingress ofwater and verified by standardized test methodsEg – IP 4X for Indoor Sub station Panels

Basic Test Duty

1. Short circuit switching duties verified for different fault currents as under for breakeroperating sequence ( O - 0.3sec - CO – 3 min – CO )2. Switching Current (kA) = T10, T30, T60, T100s & T100a

3. Followed by supplementary test of contact resistance measurement & dry power HVWithstand capacity test


Type tests – Internal Arc Test - Classification

Classification: IAC ( “Internal Arc Classified” )

Accessibility: A (F, L, R)*B (F, L, R)*C

Test values: Current [ kA ] and duration [ s ]

Example 1: IAC A FLR 40 kA 1 s

Example 2: IAC B FL 31.5 kA 0.5 s

• F = Front; L = Lateral; R = Rear

• A= Autorised operators; B = GeneralPublic; C= Pole mounted /unreachable


• The technical committees responsible for the testing standards, incorporatethe learning from field experience & from the test lab experience.

• The whole idea is to built in more safety, better reliability, practical conditionsimulation......................to be able to protect the operators & general public.

Why IEC Evolved wrt Internal Arc


Overcoming Weaknesses of old IECOvercoming Weaknesses of old IEC

1: Old IEC allowed middle cubicle of the switch board for internal arc testing.•Consequence - The middle cubicle was supported from the 2 sides & was not testedfor the worst condition.

•Remedy - The new IEC makes it mandatory to perform the internal arc test on theextreme cubicle.

1: Old IEC allowed middle cubicle of the switch board for internal arc testing.•Consequence - The middle cubicle was supported from the 2 sides & was not testedfor the worst condition.

•Remedy - The new IEC makes it mandatory to perform the internal arc test on theextreme cubicle.

2: Old IEC did not demand simulation of room condition•Consequence - The hot gases, released from the test object, went up in the skywhereas in real condition these shall hit the roof & get reflected from the roof & maycause fatality.

•Remedy - The new IEC makes it mandatory to simulate side walls & roof like a room &then only test the switchgear.

2: Old IEC did not demand simulation of room condition•Consequence - The hot gases, released from the test object, went up in the skywhereas in real condition these shall hit the roof & get reflected from the roof & maycause fatality.

•Remedy - The new IEC makes it mandatory to simulate side walls & roof like a room &then only test the switchgear.

3: Old IEC did not demand close door operation•Consequence - The MV switchgear could be operated with the door open therebyexposing the operator directly to the possible arc products & rendering the IAC testmeaningless.

•Remedy - The new IEC makes it mandatory to test the switchgear in “real operatingcondition”. Implying that if the door has to be opened for operation then the switchgearbe tested with door open condition. Indirectly making “all operation behind closed doora mandatory feature.

3: Old IEC did not demand close door operation•Consequence - The MV switchgear could be operated with the door open therebyexposing the operator directly to the possible arc products & rendering the IAC testmeaningless.

•Remedy - The new IEC makes it mandatory to test the switchgear in “real operatingcondition”. Implying that if the door has to be opened for operation then the switchgearbe tested with door open condition. Indirectly making “all operation behind closed doora mandatory feature.

Internal Arc Fault


Type tests – Internal Arc TestInternal Arc Test in following compartments:

• CB Compartment

• Busbar Compartment

• Cable Compartment

Criteria 1 – Doors & Covers must not open

Criteria 2 – Parts of the Switchgear must not fly-off

Criteria 3 – Holes must not develop on the external parts ofthe enclosure

Criteria 4 – Indicators must not ignite

Criteria 5 – Earth connections must remain effective

Test Passing Criteria


Installation of Spares



Installation of Spares

Mounting Trip Coil

Removal of Trip coil

Mounting Spring Charging Motor

Removal of Spring Charging Motor

Removal of Closing coil


Maintenance Schedule



MAINTENANCE AND INSPECTION SCHEDULEWhy Maintenance ?

Preventive maintenance today, Can avoid costly failures tomorrow

The failures that can lead to….

Major breakdowns A loss of production A loss of property Even a loss of lives

Ultimately a loss to the Business


MAINTENANCE AND INSPECTION SCHEDULE

The frequency of the maintenance depends essentially onservice conditions viz.. Frequency of operation

Tripping on fault

Relative humidity

Presence of dust & reactive gases

After every 3000 mechanicaloperations OR

After six months if switchboard isexposed to dust OR

After an idle period longer than sixmonths ORevery year

It is Recommendedto carry outPreventive

Maintenance

When maintenance is required ?


Upkeep of switchboard room

Switchboard room should be clean, well

ventilated & dust free.

Ensure switchboard room to be free from

insects, rats & lizards

Closed loop air supply & exhaust system to be

ensured in dusty surrounding

Cable trenches, bus duct entries are to be

sealed to restrict the entry of lizards, rats &

snakes



Pressurized air circulation system to be used in a contaminatedenvironment where chemical gases, fumes, steam fumesetc,which can cause harmful effects to the switchboardequipment

Appropriate measures to be taken to avoid leakage & seepageof water through ceiling & walls inside the switchboard room asit can lead to flashovers

A thermometer should be installed in the vicinity of theswitchboard for monitoring ambient temperature

Entry to the switchboard room should be restricted toauthorized personnel only, preferably to have locking provision.




Name and telephone numbers of the nearest dispensary anddoctor should be displayed

Fire fighting equipment and Fire alarms as prescribed by thesafety department should be available in working condition.

Relevant drawings of switchboard e.g. General arrangementdrawing, Wiring diagram, should be kept inside the cupboardfor reference whenever required

A hydraulic or manual operated trolley should be keptavailable for loading & unloading of the Vacuum CircuitBreakers.




Before starting the maintenance

Switch off incoming power supply before starting maintenance. Lock out

incoming power supply. For safe operations, rack out incomer VCBs to

isolated position & lock them

Measure voltage on busbars to ensure that busbars are de-energized.

Switch off the control supply.

Isolate remote control voltage sources.

Ensure that only qualified personnel are instructed

and permitted to use the defeat mechanism

to gain access to an energized panel



Do not attempt to withdraw the unit or disconnect any terminations when

the defeat mechanism has been used to open a compartment door.

Current transformer primaries must not be energized when secondary's

are open circuited.

Only manufacturer recommended lubricants should be used.

For safety of personnel working on busbars, provide temporary earthing

using a metallic chain/strip near the workplace. Remove this earthing

only after the job is completed.




After maintenance, if Panel is going to be de-energised for a longer

period, switch on the panel space heaters to prevent moisture

condensation on the cables/insulators.

vacuum cleaners should be used to remove dust and avoid moisture

condensation in the switchboard

Use recommend tools and equipment for maintenance of switchboards




Recommended Tools for maintenance Cleaning

Dry cloth

CRC 2-26 Spray

Vacuum cleaner with small nozzle

WD - 40 ( Rust Preventer )

Zero Grade Emery Paper ( not for contacts )

Tightening

Screw drivers 6”, 8”, 10”

Double ended spanners ( 4mm to 19mm )

Socket spanner set ( upto 19mm )



Torque wrench 0.3 to 1.2 kg.m, 1.2 to 7 kg.m, 5.0 to 23.0 kg.m

Heavy duty Star Screw Driver (12 “)

Allen key set 0 - 10mm

Plier 8”

Tubular spanners

Nose pliers 8”

Wire stripper 0 - 6 sq.mm

Small star screw driver

Recommended Tools for maintenance



General Guidelines for switchboard maintenance

All electrical power should be de-energised, tagged and locked out

accordingly with established procedures.

Access covers and enclosures should be removed and all assemblies

should be hand cleaned with a dry lint free cloth and non metallic brushes.

Do not use cotton waste for cleaning.

Special attention should be given to insulating surfaces.

High power vacuums should be used to remove all loose debris.

Compressed air should be avoided to prevent forcing dust and

contaminates into other components.



Contacts in circuit breakers, contactors, and other switching equipment like

Earthing switches should be inspected & cleaned of all dirt.

All the components of switchboard should be examined for cracks, defective

plating, frayed wires, burnt insulation, and general overall condition

Ensure tightness of Cable, connections and components, also mechanical parts

of equipments should be free to function

Loose connections and damaged insulations should be repaired or replaced to

avoid Over heating and flashover

General Guidelines for switchboard maintenance


Busbar connections and fasteners to be ensured for tightness

Frame grounding cable for tight connections

Insulating materials / creep surfaces, clean, intact / retape taped bars asneeded

Fuses and earthbar links, right size and tight

Switches, knobs, present and all in good condition

Ensure VCB ON-OFF operation at least 4 to 5 times, also free operation ofother mechanical parts

Lubricate appropriate components, do not over lubricate

What to Inspect…?



Cables and bundles secured, no abrasive contacts

Charging handles and rails, in position and secured

Insulation matting, always in place

Equipment labeling is correct

Structural integrity of enclosures, Gas duct and IAF flaps are in place

Latches and locks operating

What to Inspect…?



(a) Cleaning• All dust and dirt found on the top covers should be brushed off and cleaned prior to

commencing any dismantling to minimize ingress of dirt into internal portions of theswitchgear panel. Use lint-free clean cloth to clean the switchgears.

(b)Insulation• All insulation surfaces should be cleaned and closely inspected for signs of tracking,

treeing, blistering, and delamination or mechanical damage. There should be no trace ofgrease on any part of the insulation surfaces especially at the spouts in the breakercompartment. Clean and dry insulators with a suitable cleaning agent.

• Caution: Cleaning agent cannot be used on the black & grey surfaces of the• bushing or on the copper bars.

(c) Heater• The operation of all heaters, where fitted, should be verified.

What to Inspect…?



(d) Main and Earth busbars connections• Ensure that all connections are tight and that good contact is maintained.• This examination should include opening the boots for torque checks on the

busbar bolt joints. There is a very slim chance for yearly shutdown of the bus, butchecks should be done at least once in three years.

(e) Secondary wiring and fuses• Ensure that the connections are tight and good contact is maintained. Verify the

continuity of wiring to the fuses, instrument transformers, relays, instruments andother associated devices.

• All contacts including that for the plug and socket contacts should be cleaned andlubricated sparingly with the correct lubricant. Fuses should be tested forcontinuity and inspected for signs of deterioration.

•

What to Inspect…?



(f) Auxiliary switches, indicating devices and interlocks• Auxiliary switches should be kept in a clean and operational condition because

they are critical to the correct functioning of the equipment, especially theprotection system.

• Indicating devices such as semaphores should be tested for good operations• and blown bulbs replaced. Interlocks and locking devices should receive

particular attention, especially those associated with earthing and testingfacilities. A strained or worn out

• device may result in a dangerous condition. It should be verified that any mal-operation is satisfactorily inhibited. Lubricate when necessary.

(g) Shutters• The shutter mechanisms should be verified for correct operation and lubricated

sparingly. This should normally be carried out immediately after the withdrawal ofthe breaker from its housing or immediately prior to reenergization.

What to Inspect…?



What to Inspect…?


(h) Isolating contacts• The isolating contacts should be examined for discoloration and

deformation due to overheating or environmental contamination. Replace ifnecessary. Replace conductors if cause is overheating. For environmentalcontamination, eliminate source of contamination and clean the platingsurface with appropriate cleaning agent.

(i) Earthing switches• Earthing switches should be examined for correct operation and its contacts

for good connections. The correct interlocking between the earthing switchand the breaker should be verified.



(j) Meters, Transducers and Batteries• For the following items, refer to the relevant manufacturer's instruction

manuals provided for operation checks:• Protection relays• Voltmeters and ammeters• Energy meters (active or reactive)• Transducers (voltage, current, watt, var)• DC tripping/control supply

(k) Protection relays• Wipe off any dust on the relay covers before removing them. Ensure that

the covers are securely replaced to minimize the ingress of dust into therelays. Injection testing by primary injection is preferred. However, regulartesting by secondary injection is sufficient to prove the integrity of the relays.

• Tests should be made on protection relays to verify the operating andresetting times, the pick-up and drop-off values.

What to Inspect…?



• In the case of electro-mechanical relays, great care should be taken toavoid damage to the relay mechanisms when manipulating the inductiondisc of the relay.

• In general, avoid subjecting protection relays to high-voltage tests. If suchtests are required, ensure that the correct test voltages are applied to avoiddamage to the relay, especially the solid state type.

• If it is necessary to disturb any connections for testing purposes, ensure thatthese connections are correctly restored before returning the switchgearsinto service.

(l) Current transformers (CT) and voltage transformers (VT)• Steps should be taken to ensure that voltage transformers are isolated and

discharged to earth before commencing examination. Care should be takento ensure that the transformers are not made live inadvertently due tofeedback from the secondary windings.

• In the case of the CT, attention is drawn to the dangerous voltages that mayresult if the secondary's are open-circuited while the primaries are on load.

What to Inspect…?



• Any connections removed for checking/testing must be correctly replacedand securely tightened. Insulation resistance and continuity tests of thesecondary windings should be carried out where possible.

• Generally, check CT's and VT's for physical appearance and that all relatedconnections are tight. The insulation material should be cleaned and closelyexamined for any signs of damage such as cracks, tracking marks orpeeling.

• In case of withdrawable VT's, the isolating contacts should be checked,cleaned and lubricated sparingly. The correct operation of safety shutters forthe VT truck should also be verified. Primary and secondary fuses shouldbe tested for continuity.

(m) Control relays or contactors• Inspect mechanical parts for free movement with the control and main

circuits isolated. Check the operation of the relays/contactors by energisingthe control circuit.

What to Inspect…?


Maintenance of Switchboard

BUSBAR ZONE

Check that power cables do not exert undue pressure on the termination

Ensure proper clamping of cables on the glands and cable clamps to avoidweight of cables acting directly on the termination

Close rear door covers/plates

Check whether joint shrouds are in it’s place

Remove rear door plates and check for tightness (at the specified torque values)of hardware for busbar / fishplate coupling. Poor connections will causeoverheating.


POWER CABLE ZONE


Check for unused holes, block them

Check for presence of shrouds/boots on outgoing terminals

Check for proper termination of extension links

Always use copper wires / cables for control purposes

Check all power and control circuit connections at terminal blocks, cable

terminals, switch terminals, contactor terminals, for tightness

Refer to the scheme diagrams and terminal chart before reconnecting the

meters and relays

Maintenance of SwitchboardMAINTENANCE AND INSPECTION SCHEDULE


Inspect all devices to ensure that the equipment is in proper working order

Check that all CT secondary shorting links are present

Ensure that the wires are not hanging loose. Temporary connections madeduring testing should be removed

Check the setting of Intelligent relays as per setting chart

Check the setting of overload relays and other protection relays

Check that fuses are fitted in main and auxiliary circuit and that ratings areappropriate for the circuit




Inspect all wiring for wear and cuts, wherever they pass on sharp edges

Look for wear of the silver plating on the contacts & on the earthing contacts fixed to VCBand at the point where they engage with the fixed contacts.

Clean & lubricate the contacts once a year with HP MPL (EXXON) grease

Look for indications of overheating, arcing or insulation breakdown Inspect power andcontrol contacts. Replace worn out contacts

Inspect all auxiliary and control circuits for desired functioning

Grease racking screw and telescopic rails at least once a year ( HP - LETHON - 2 orSYNTHOLUBE-20 of HJ Leach & Co.)

Inspect all door gaskets for wear and replace where necessary




Before energizing the switchboard Inspect busbar chamber, unit compartments and cable alleys, remove tools, conductor

strands and any other material lying loose

Use vacuum cleaner to remove dust, small particles etc.

Check tightness of electrical joints

Remove CT secondary shorting while connecting the meters or relays

Close all doors before energizing the board, do not operate any equipment with it’s

compartment door open when the board is energized

Ensure correct settings of protection relays for overload and short circuit coordination



Check for operation of the feeders as per scheme drawing

Equipment must be operated at rated voltages. Check the supply voltage before the circuit

is energized

Remove all temporary wires

Remake all connections removed for troubleshooting purposes

Check for the quality of the work after it’s completion

Ensure proper earthing connections

Be alert of undesirable grounds and eliminate them

Measure the insulation resistance with 2000 volts megger between phases and between

phase and ground. It should be more than 500 Mega-ohm

Before energizing the switchboard



Repeated HV test deteriorates the insulation properties. Avoid repeated HV

test

Ensure that all other VCBs and switches are OFF while making the Incomer

ON

Switch ON the space heaters beforeenergizing of Switchboard

Before energizing the switchboard


Space Heater

Effect of High humidity & Water sipage inSwitchgear



CHECKPOINT CHECK ITEM CHECK METHOD CRITERIA WHAT TO DO FREQUE

NCY

Entire VCB

Tightness of boltsand nuts

By tightening themwith screw driverand wrench

No loose connectionsRe-tighten looseconnections

Once in3

years*

Dust and foreignmatter

Visual checkThe VCB should beclear of dust andstains

Clean with a vacuumcleaner. Wipe with aclean, dry cloth andrecommended cleaningagent (AS66)

Deformation,excessive wearand damage

Visual checkNo deformation,excessive wear ordamage

Replace parts, ifnecessary

Lost or missingparts

Visual check No missing parts Replace missing parts

Controlcircuit

Electrical closingand tripping

Check at the“DISCONNECTED”position

The closing andtripping operationscan be done smoothlyMotor can springcharge automatically

Check circuits and theclosing and trippingdevices.When the motor cannotspring charge, check ifline fuse is blown.Replace if blown.

Once in3

years*



Operatingmechanism

Dust and foreignmatter

Visual checkThere should be nodust and foreignmatter

Remove foreignmatter withpressurized air

Once in 3years*

Smooth operation Manual operationOperation should besmooth

Clean off oldlubricant and apply asmall amount offresh lubricant, ifnecessary.

Lubricant ofbearing pins

Check by sightand touch

Shaft of closingand trippingportion

Visual check Must rotate smoothly

Main circuitdisconnects/contact finger

Dis-colouration ofcontacts

Visual checkThere should be a thinfilm of contact greaseon the contact surface

Clean the contactsurface of old greaseand apply a thin filmof new grease

Once in 3years*

Main barrierContaminationand dis-colouration

Visual check

There should be noforeign matter

Clean with pressuredair and then wipewith clean cloth Once in 3

years*There should be notracking marks, cracksor damages

Replace whendamaged

CHECK POINT CHECK ITEM CHECK METHOD CRITERIA WHAT TO DO FREQUENCY



Measurementof insulationresistance

When the insulationresistance betweenthe main circuitterminals is low,clean the surface ofthe vacuuminterrupter with a drycloth and then takethe measurementsagain

Once in 3years*

Main conductor-Ground / Mainconductors

500MΩ or more 2000V

Control circuit Ground 2 MΩ or more 500V

Measurementof contactresistance

Measuring location Resistance TesterCheck wipe andcontact gaps

Once in 3years*Across each set

contacts1250A <75µΩ

Micro-O-meter

Timing Test Across each set ofcontacts

Trip test & Close test As per specs

Carried outwhen speedof operationis critical

CHECK POINT CHECK ITEM CHECK METHOD CRITERIA WHAT TO DO FREQUENCY


Troubleshooting

Part Trouble Possible Cause Remedy

DO

OR

Handle cannot belocked

Wrong key (if any)

Internal mechanism rusted

Internal mechanism faulty

1. Check key number

2. Lubricate hole

3. If in emergency, cut off thehandle

Loose handleFixing screws loose

Internal mechanism worn out

1. Re-tighten the screws

2. Replace handle

STR

UC

TUR

E

Door warped and loose

Loose screws at the hinges

Hinge pin bent

Door deformed by external force

Re-adjust the door and tighten thescrews

Rectify the hinge pin

Repair the deformed portion

Internal noise

Partition plates vibrating due toelectromagnetic Induction/loose screwson partition plates

Cable touching gland plate.

Partial discharge due to stained or moistinsulating material

For screwed on partition plates,retighten the screws.

For gland plates, add sealingcompound between cable andplate

Shutdown power and clean thesurface of the insulatingmaterial. Switch on the heatersto dry the air inside the cubicle


TroubleshootingM

AIN

CO

ND

UC

TOR

S Connections overheated1. Loose bolts

2. Overload

Re-tighten bolts to specified torqueor replace busbar if necessary

Limit current to the rated value

Ground fault or faileddielectric tests

Insulators cracked

Insulators stained with foreign matters andmoisture

Intrusion of rodents

1. Replace insulators

2. Clean and dry insulators withsuitable cleaning agent

3. Plug gaps and openings andremove rodents

ControlCircuit

Extinction of indicatingtights

Bulb filament broken

Fuse or resistor burnt

Poor contact of auxiliary switches at thebreaker

Auxiliary supply switches open circulated

Limit switch contact shifted or faulty

Replace bulb

Replace fuse or resistor

Clean the auxiliary contacts

Check MCCB of fuse and wireterminals

Check limit switches contact andoperation of limit switch.

Simultaneous lighting ofboth ON and OFFindicating lights

Poor contact of breaker auxiliary switches

Contact resistance increased due to dustcontamination or oxidation of contacts(especially when they are not operated forprolonged period)

Clean contacts of auxiliary switch

Operate the auxiliary switch severaltimes

Poor operation of controlcircuits

Loose screws on the terminal blocks

Control circuit plug not properly connected

1. Re-tighten screws on theterminal blocks

2. Re-insert the control circuit plug



TroubleshootingVA

CU

UM

CIR

CU

IT B

REA

KER

VCB cannot close

Circuit breaker not fully inserted

REMOTE/LOCAL selector switch incorrectlyselected

Auxiliary supply MCCB open

Control circuit plug not connected

Control circuit voltage drop

Closing coil burnt

1. Breaker to be aligned withthe CONNECTED positionsticker

2. Switch to correct position

3. Close the MCCB

4. Connect the control plug

5. Restore the voltage

6. Replace the coil

VCB cannot open

1. REMOTE/LOCAL selector switchincorrectly selected

2. Auxiliary supply MCB/switch open

3. Control circuit voltage drop

Switch to correct position

Close the MCB/Switch

Restore the voltage

VCB cannot be inserted intocubicle

Wrong rating of breaker

Lock lever does not lift up due to theCLOSED position of breaker

Insert the breaker of the correctrating

Trip the breaker

Adjust the shutter mechanism,lubricate the moving part

SHU

TTER

Shutters cannot close1. Shutter damaged

2. Moving parts poorly adjustment andlubricating oil deteriorated

Repair damaged shutters

Adjust moving parts and applylubricating oil

Clean the moving part



Electrical Components



Understanding of Electrical Scheme





DO’s

DO’s

All operation behind Close Door.

Ensure following before racking VCB from TEST toSERVICE position1. VCB is in TEST Position2. VCB is in OPEN condition3. Earth Switch is in OFF condition4. Control Circuit plug is fully engaged. Red lever on control

plug mechanism should come upward direction whenControl Plug is fully engaged

Earth Switch shall be operated when VCB is inDISCONNECTED position.Earth switch handle shall be rotated in direction shown only.


DO’s

DO’s

Cross check rating of VCB before insertion inside the panel

Complete switchboard shall be free from Dust & other foreignparticles

All opening including hole provided for earthing connectionare properly closed with seal to avoid vermin/reptile entry

Ensure VCB Compartment door is fully closed and all Allenbolts on VCB compartment door is fully tightened. Then DoorPadlock shall be done.


DONT’s

DON’Ts

Do not apply any flammable lubrication on busbar jointsor VCB finger contacts

Do not perform any operation in OPEN door condition

Do not try to rack in VCB when control plug is notengaged. By operating the VCB forcefully it may damagethe control plug mechanism

Do not try to rack in VCB when VCB is in CLOSEDcondition

Do not try to operate Earth Switch when VCB is inCONNECTED position


DONT’s

DON’Ts

Do not try to insert wrong rating VCB inside the panel

Do not insert VCB without unlatching the shutterassemblies

Do not try to by pass VCB compartment door interlockwhen the feeder is in live condition

Do Not operate the padlock handles if door bolts are nottightened fully by Allen key.

All Interlocks are designed as per IEC working withcertain Torque Limits. Do not exert force higher than 750Newton as per IEC.

Do Not try to rotate ESW in the wrong direction


Q & A


Thank you

Documents

Training Program 25.01.2014