1. Presentation on Sub-station Design, Operation, Maintenance & Safety
Prepared & Presented by
Engr. SK Md. Ruhul Amin
GCE
PRAN-RFL Group

2. Presentation at a Glance
Topic Slide
Considering points for Sub-station design
Procedures of a new Sub-Station establishment
Safety rules of Sub-station
Compliance points on Sub-station
Standard procedure of Sub-station maintenance
Standard & major Sub-station equipments
Testing of sub-station equipments
How to operate sub-station safely
Electrical check list for sub-station equipments

3. Considering points for Sub-station design
Major following points must be considered for new sub-station design-
Nature of load
Total load
Source
Location
Safety
Easy operation
Cost effective

4. Procedures of a new Sub-Station establishment
Have to follow the following points to make a new sub-station-
Site selection considering load center
Proper load calculation
Design & drawing considering safety, operation & cost
Equipments selection considering load character & power use with safety.
BOQ with details specification & estimate.
Equipment procurement as per BOQ
Proper installation as per design & drawing
Testing
Commissioning
Operation

5. Safety rules OF Sub-station
Sub-station control room height should be 3 to 3.6 meters
Safety clearance for substation & power station equipments should be provided (For LT panel meters & for HT panel meters)
Illumination must be sufficient ( lux)
Floors, floor openings, passageways, stairs should be wide enough
Evacuation routes should be clearly marked
Installation of equipment:
Protective grounding
Guarding live parts
Working space above electrical equipment

6. Safety rules OF Sub-station (Cont.)
While working inside the boundaries of electric sub-stations all employees shall wear the following personal protective equipment-
1. Hard hats
2. Safety glasses (non-metallic frame)
3. Steel-toed Shoes
4. Hand gloves
5. Mask (If required)
6. Flame retardant clothing
7. Torch light or other light to check the insight of panels
8. Required testing equipments
9. Grounding kits (To discharge the static charge before work)
10. Others as directed by competent person

7. Compliance points on Sub-station
Planning
Typical physical security configuration
Alarm monitoring
Employee indoctrination
Compliance Aides
All equipments should vermin proof with proper ventilation facilities
All equipments must have double earthing system
Visitor Control-Escorts
Visitor Control-Access point monitor
Lock & Key

8. Compliance points on Sub-station (Cont.)
Implementation Issues
Recommended Practices
Proper single line diagram of sub-station should be hanged in the entrance
Proper single line diagrams should be hanged in front of the panels
Proper single line diagram of power distribution system with conductor size and switchgear specifications
All test reports of equipments should be compiled in sub-station
Defense in depth
Change Management Process
Checklist should be hanged in the sub-station

9. Compliance points on Sub-station (Cont.)
Routine maintenance schedule should be kept and maintained properly
Maintenance works record should be kept
Keeping unnecessary materials inside the sub-station strictly prohibited
Rubber mats must be kept in front of the panels
Sub-station should have enough ventilation system
Main earthing should be connected properly through earthing bus bar
Power-station should be implemented with sound protective system for standard acceptable sound

10. Standard procedure of Sub-station maintenance
Before starting the normal maintenance procedure, the following operation must be done-
Ensure the HT switchgear is in the off position
Ensure the HT isolator/abs is in the off position
Ensure the earthing switch is in the on position
Ensure static charge will discharge by the earth
All load switch should be in the off position
Equipment terminals should be connected with the earth until complete the maintenance works
Maintenance tag should be hanged in front of HT switchgear

11. Standard procedure of Sub-station maintenance (Cont.)
Then normal maintenance procedure will start as follows-
Inspection
Troubleshooting
Circuit diagram & drawing study
Servicing
Testing
Overhaul
Guidelines for maintenance of switchgear
Follow the safety instruction during maintenance time
Maintenance schedule check list
Maintenance of circuit breaker-
a. General Inspection
b. Cleaning & Drying
c. Insulation surface
d. Interrupter
e. Mechanism
f. Interpole linkages

12. Standard procedure of Sub-station maintenance (Cont.)
Likely troubles and essential periodic checks to avoid them
Maintenance of transformers
Care and maintenance of earthing
Insulation resistance measurement
Maintenance of generators
Relays and protection circuit maintenance
HT panel maintenance
LT panel maintenance
PFI panel maintenance
Distribution system maintenance
MDB, DB, SDB maintenance

13. Standard & major Sub-station equipments
HT switchgear
LT switchgear
Transformer
PFI unit
Lightning arrester
Current transformer
Potential transformer
Bus bar
Circuit breakers
Isolator switch/ ABS.
Control and relay panel
Protective relays
DC power supply for control Ckt.

14. Standard & major Sub-station equipments (Cont.)
Associated system in sub-station-
1. Sub-station earthing system
2. Overhead earth wire shielding
3. Illumination system
4. Protection system
5. Control cable
6. Power cable
7. PLCC system (power line carrier communication system)
8. Telephone, telex, microwave, OPF
9. Auxiliary standby power system
10. Fire Fighting system

15. Testing of Sub-station equipments
Thermal scanning
Infrared temperature gun test
Voltage test by voltmeter
Ampere check by clamp meter
Insulation resistance test by meagger
Earth resistance test by earth tester
Phase sequence test by sequence test meter
Core loss & copper loss test (By open circuit & short circuit method)
Capacitive reactance test
Inductive reactance test
Series lamp test
Visual Test

16. How to operate Sub-station safely
To operate the sub-station safely, the following sequence of procedures must be maintained strictly-
Ensure the required voltage & frequency
Ensure the earth switch is in the off position
Ensure the isolator switch/abs is in the on position
Ensure the LT main switch is in the off position
HT switchgear is turned on
Ensure the output voltage of HT switchgear
Check the incoming voltage of LT panel (If require voltage is ok)
LT main switchgear is turned on

17. How to operate Sub-station safely (Cont.)
Ensure the required voltage of bus bar
Load will be on step by step
After connecting all load, operators will monitor all LT and HT switchgear
Note: For any emergency shutdown, operator must turn off the HT switchgear instead of LT switchgear for better safety

18. Electrical check list for Sub-station equipments with standard time duration
General inspection (Daily)
Visual inspection (Daily)
Check insulation resistance of each pole of phase to ground across terminals with cable (after 6 months)
Check the dielectrical strength of transformer oil (yearly)
Check mechanical operations of switchgears (yearly)
Check oil level of transformer (Daily)
Clean the external surface of equipments by air blower (Daily)
Clean the internal surface of all panels by air blower (Weekly)
Measure contact resistance of conductor (After 3 months)
HT & LT bushing leakage (Daily)
Cable size check considering load (Every year)

19. Electrical check list for Sub-station equipments with standard time duration
Contact point check by thermal scanner (Every 3 month)
Contact point thermal check by infrared gun (Every week)
Servicing as per schedule & instruction of manufacturer
Control wiring check (Every 3 months)
Safety signage, rubber mats (Daily)
Artificial respiration
Distribution boards installed in compliant locations
Multi looping of wiring (Weekly)
Color code check
HT drop out fuse (Visual check every day, continuity test every month)
Cable laying phase sequence (Yearly)

20. Electrical check list for Sub-station equipments with standard time duration
Insulation resistance measurement (Every 6 months)
Fire detection, security and alarm system (Daily))
Switchyards, sub-station ground connection & earthing system check (Every 3 month)
Distribution line & power cable test (Yearly)
Emergency lighting (Daily)
Lightning arresters (Every 6 months)
Transformer temperature check (Daily)
Transformer silica gel color check (Daily)
All meter readings & parameters check (Daily)
Cable joint visual check (Always)
Phase to phase, phase to neutral & neutral to earthing test (Monthly)

21. THANKS