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

Presentation at a Glance Topic Slide Considering points for Sub-station design 3 Procedures of a new Sub-Station establishment 4 Safety rules of Sub-station 5-6 Compliance points on Sub-station 7-9 Standard procedure of Sub-station maintenance 10-12 Standard & major Sub-station equipments 13-14 Testing of sub-station equipments 15 How to operate sub-station safely 16-17 Electrical check list for sub-station equipments 18-20

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

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

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 1.02 -- 1.4 meters & for HT panel 1.4 -- 2.6 meters) Illumination must be sufficient (150-200 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

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

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

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

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

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

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

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

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.

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

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

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

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

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)

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)

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)

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