In-Country Training On Operation, Maintenance, Protection & Control of 33/11 kV Substation Project Name: Design, Supply, Installation, Testing & Commissioning of 33/11 kV sub-stations with source end feeder bays. Contract No: BREB/UREDS/W-01A-001/02/2016-2017 BREB/UREDS/W-01A-002/03/2016-2017 BREB/UREDS/W-01A-004/04/2016-2017

1. Installation
Operation & Maintenance of 33kV & 11kV
Switchgear

2. Maintenance & Inspection of S/S Equipment
• Maintenance of Substation Equipment
Preventive and Schedule Maintenance
Emergency or Break-down maintenance
• Inspection of Substation Equipment
Daily Inspection
Weekly Inspection
Monthly Inspection
Quarterly Inspection
Half-yearly Inspection
Annual Inspection

3. Operation of Power Transformer
Operation of
tap changer
Operation of cooling
control system
Operation of
breathing system

4. Maintenance of a Power Transformer
Test oil sample of transformer main tank & tap changer tank
 Check condition of oil gauges and oil level
 Check for oil leakage & integrity of gasket joints
 Check the tightness of nuts & bolts
 Check the insulation resistance of bushing
 Check that silica gel crystals are blue
 Re-greasing of bearings
 Check the performance of oil temperature & winding temperature
meter
 Change the oil of OLTC
 Check the control system and driving mechanism of OLTC
 Check insulation resistance between each winding and ground.
 Calculate the Dielectric Absorption Ratio-
DAR = (I.R. of 60 sec)/(I.R. of 15 sec)

5. Test of Insulating Oil
Test/Parameter Reference value
• Dielectric strength test: Min 30kV at 2.5 mm gap (12.5mm sphere)
• Acidity test: Acid value less than 0.02 mg KOH/g
• Moisture content in oil: 50-60 ppm
• Viscosity at 20°C : 40 cst
• Pour point maximum: -10°c
• Flash point: 140°c
• Dissipation factor or
Power Factor/loss tan delta: 0.5% (at 90°c), 0.1% (at 20°c)
• Resistivity : 5.7×1014
Ω-cm
• Interfacial tension at 27°C: minimum 0.04 N/m
• Dielectric constant: 2 to 2.5
• Specific gravity 0.895 (at 20 °C)

6. Operation and Maintenance of Breakers
• Timing test
• Insulation resistance test
• Measurement of contact resistance
• Check SF6 gas pressure
• Check the Charging Mechanism
• Check security of couplings and pipes
• Measurement condensation temperature (Dew point) of
gas
• Check operation of pressure gauges

7. Instrument X-former
 Two Types:
 Current X-former
 Potential X-former
 Use:
 For Protection
 For metering
 Maintenance:
 Check of physical condition
 Check the insulation resistance
 Check tightness of primary side & secondary terminals
 Check the ratio
 Justify the accuracy
 Check for oil leakage for oil immerged CT and PT
 Check the dielectric strength of oil

8. Class of Accuracy
For Current X-former:
• Metering purpose: 0.1% to 1.0%
• Protection purpose: 5P10 to 5P20
Special Accuracy For Differential Protection:
X / PS class
For Potential X-former: 0.5-2%
Burden= Voltage * Current =VA

9. Operation and Maintenance of Post Insulator,
Lightning Arrester & Bus Bar
Operation and Maintenance of Insulator:
• Check security of nuts, bolts and clamps securing drive parts.
• Clean and inspect porcelain insulators
• Check split pins in clevis and oil all clevis pins
• Clean and lubricate auxiliary switch contacts
Operation and Maintenance of Lightning Arrester:
• Wash Diverter housing
• Check for damage to porcelain housing and for deformation of corona
or stress rings.
Operation and Maintenance of Bus Bar:
• Cleaning of insulators
• Tightening or changing of clamps
• Checking of insulation resistance

10. Battery and Battery Charger
• Battery and Battery Charger
 Importance
 Working principle of battery charger
• Maintenance of Battery and Battery Charger
 Measurement of individual cell voltage
 Measurement of individual cell specific gravity
 Check of electrolyte level
 Cleaning of terminals and charger unit
 Observation of back-up support
 Check the voltage and current at float and boost condition

11. Devices of Relay panel for 33 & 11KV side
• Protective Relays
• Annunciator
• Control switches
• Energy meters
• Voltmeters, ammeters, power factor meter
• Semaphore indicator
• Heater
• Auxiliary Relays
• Terminal strip and Test terminal block.

12. Protection of power system
Requirement of protection:
• Normal operation
• Prevention of electrical failure
• Mitigation of the effects of electrical failure
Functional characteristics of protective relaying
• Sensitivity, Selectivity and Speed
• Reliability

13. Faults of power system
Classification of faults of power system
• Short Circuit fault
• Three phase fault (with or without earth)
• Two phase fault (with or without earth)
• Single line to ground fault
• Open circuit fault
• Simultaneous fault

14. Operation & Maintenance of Control Relay Panel
• General cleaning of both inside and outside
• Check for looseness of connections
• Checking of heater
• Check operation and accuracy of instruments
• Carry out insulation tests between wiring and earth,
and between circuits
• Check operation of all alarms and control functions
• Carry out secondary injection tests of relays

15. Different testing instruments and equipment
of a Substation
• Meggar
• AVO Meter
• Low Ohm Meter
• Digital Transformer oil testing set
• Oil centrifuging machine
• Earth tester
• Thermometer infrared mini
• Mili ampere measuring clip on ammeter
• Clip on ammeter
• Polarity tester
• Tan delta test set
• Testing board with necessary cables lugs
• CT Vk testing set (knee point voltage test)
• Moisture test set for transformer oil
• Capsule vacuum gauge 0-50mbar
• Turn ratio test set
• Gas burner
• Secondary injection set

16. Testing equipment for switch gear
• Insulation tester
• AVO meter
• Micro Ohm meter
• Breaker operation time measuring equipment
• Gas pressure checking meter gauge
• Gas leak detector
• High voltage test set
• Vacuum pump
• Gas filling device

17. Testing equipment for Isolator & PT
Testing equipment for Isolator:
• Meggar- 1000V / 2500V / 5000V
• Micro Ohm meter
Testing Equipment for PT:
• AC high voltage test set
• Meggar – 1000V / 2500V
• Ratio test meter
• AVO meter
• Single phase AC supply lead with clamp and MCB

18. Testing Equipment for Outdoor Bus & Indoor Bus
Testing Equipment for Outdoor Bus:
• Meggar
• High voltage test set
• Micro Ohm meter
• Single phase AC supply lead with supporting clamp & MCCB
Testing Equipment for Indoor Bus:
• Meggar
• High voltage test set
• Micro Ohm meter

19. Testing and Commissioning
• Switchgear:
– No load mechanical operation test
– To verify the operation of switchgear
(operation at 85% and 110% of rated voltage)
– Check the contact travel characteristics
– Measurement of contact resistance
– High voltage test
– Voltage tests on auxiliary circuits
– Insulation resistance measurement
– Check the spring charge mechanism
– SF6 gas test

20. Transformer:
• Visual check
• Insulation resistance measurement
• Vector group test
• Measurement of winding resistance
• Ratio test of Bushing CT
• Magnetizing test of Bushing CT
• Polarity test of Bushing CT
• Dielectric test of oil
• Short circuit test
• Magnetic balance test
• Oil / winding temperature meter test
• Impedance test
Testing and Commissioning

21. CT :
• Insulation resistance test
• Ratio test
• Polarity test
• Magnetization test
PT:
• Insulation resistance test
• Ratio test
Dis-connector Switch/Isolator:
• Insulation resistance test
• Contact resistance
• Interlocking test
• Check the operating mechanism
Testing and Commissioning

22. LIGHTNING ARRESTER:
• Insulation resistance test
AUXILIARY TRANSFORMER:
• Insulation resistance measurement
• Ratio test
• Vector group test
HIGH VOLTAGE CABLE TEST:
• Visual check
• Insulation resistance test
• High voltage test
Testing and Commissioning

23. Thank you