This guide serves for information, knowledge, and interview test preparation. It presents a preliminary construction sequence for installing a three-phase, oil-immersed 380/132/13.8 kV autotransformer at an SEC transmission substation in Saudi Arabia. Use it for tender planning and site execution sequencing. Do not treat it as a substitute for approved method statements, lifting studies, the manufacturer’s installation manual, or the project’s Inspection and Test Plan (ITP).
This post is also a part of Extra High Voltage EHV Substation Design & 380kV Substation Design. If you are new on our website and want to learn 380kV Level, it is recommended to read first the below Posts
- 380kV Gantries & Gantry Equipment
- Inside a 380kV BSP: Overall Layout Drawing Explained
- 380kV Gas-Insulated Switchgear (GIS)
- Power Transformers
- Auxiliary Transformer Sizing for a 380kV BSP
- Vector Group of Transformers
- Autotransformers
We will complete this guide in 4 to 5 posts and two parts given below
- PART 1 – WORK BREAKDOWN (ACTIVITY SEQUENCE)
- PART 2 -COMPONENT-BY-COMPONENT INSTALLATION ANALYSIS
PART 1 – WORK BREAKDOWN (ACTIVITY SEQUENCE)
The following sequence is the recommended project baseline. Actual sequencing must follow the OEM’s instructions and the approved lifting, assembly, vacuum and oil-filling procedures.
- Site readiness and civil acceptance
- Foundation, rails, anchor bolts, oil containment, firewalls, drainage, access routes, lifting clearances, earthing and environmental protection.
- Delivery and receiving inspection
- Shipping documentation, impact recorder, tank pressure, nitrogen purity/condition where specified, dew point, accessories, transit damage and preservation records.
- Unloading, jacking, skidding and positioning
- Approved lift plan, crane or skidding system, transport frame removal, foundation alignment, leveling, wheel/rail restraints and anchoring.
- Main tank and accessory assembly
- Bushing turrets and bushings, radiators, coolers, conservator, OLTC drive, protective relays, instruments, control cabinets and auxiliary equipment.
- Internal inspection, where required
- OEM-controlled inspection of accessible internal components, active-part work if applicable, cleanliness and moisture exposure controls.
- Vacuum treatment and oil filling
- Tightness checks, approved vacuum sequence, oil processing, controlled filling, vacuum maintenance where specified, and oil sampling.
- Electrical, mechanical and functional testing
- Transformer electrical tests, oil quality, OLTC, CT circuits, alarms, trips, cooling controls, interlocks, monitoring and protection integration.
- Pre-energization acceptance
- Punch-list closure, approved test reports, protection settings, SEC inspections, readiness certificate and switching authorization.
- Energization and post-energization checks
- Support SEC operations, monitor sound, leaks, temperatures, alarms, oil levels and cooling operation, then complete handover documentation.
PART 2 – COMPONENT-BY-COMPONENT INSTALLATION ANALYSIS
For EACH component below we will provide you with INSTALLATION ANALYSIS :
- Foundation, rails/skids, anti-vibration and seismic anchoring, earthing, oil soak pit, fire walls
- Main tank: receiving inspection, impact recorder, gas pressure and dew point, internal inspection
- 380 kV (HV) bushings with turrets, bushing CTs and test taps
- 132 kV (IV) bushings with turrets and bushing CTs
- Neutral bushing and neutral earthing arrangement (solid earthing or NGR, if applicable)
- 13.8 kV tertiary bushings, tertiary delta closure, surge arresters on the tertiary, and tertiary connection (cable box / busduct)
- Radiators / coolers, headers, isolating valves, and ONAN / ONAF1 / ONAF2 fan groups with their control stages
- Oil pumps (only if applicable to this design)
- Main conservator with air cell or diaphragm, silica gel breather, magnetic oil level gauge
- On-load tap changer: diverter/selector parts, motor drive unit, drive shaft and bevel gears, OLTC conservator and breather, oil surveillance relay, tap position transmitter, oil filter unit
- Buchholz relay, pressure relief devices, sudden pressure relay and their trip circuits
- Oil temperature indicators (OTI), winding temperature indicators (WTI), RTDs and CT heater circuits
- Marshalling box, cooling control cabinet, cabling, glands, ferrules and SCADA / protection interface
- Surge arresters at HV and IV terminals (if supplied with the transformer) and flexible connections / jumpers
- Online monitoring (DGA, bushing monitoring, moisture) if specified
- Fire protection interface (deluge, nitrogen injection or equivalent as per SEC practice, to be verified)
- Oil handling system: new oil storage tanks, filter/degassing machine, vacuum pump, hoses, sampling points, oil testing before and after filling
- Vacuum treatment, oil filling and hot oil circulation (include hold times and sampling per manufacturer)
- Earthing connections and bonding of tank, radiators, cabinets and fences
- HV / IV / tertiary final connections to GIS, OHL or cable
- Final painting touch-up, nameplate, rating plate, valve position tags and warning labels