Definition
A package substation is a factory-assembled, fully tested electrical installation that integrates medium voltage (MV) switchgear, a power transformer, and a low voltage (LV) distribution panel within a single compact enclosure. It converts incoming MV supply (typically 13.8 kV or 33 kV in Saudi Arabia) to utilisation voltage (380/400 V), ready for direct connection to a facility's LV distribution network.
Main Components of a Package Substation
1. Medium Voltage (MV) Switchgear Ring Main Unit (RMU)
The Ring Main Unit is the MV interface between the incoming SEC or project supply network and the transformer. It provides switching, isolation, and protection functions at the medium voltage level. In package substations supplied to Saudi projects, the RMU is typically SF₆-insulated (sealed-for-life) with rated voltages of 12 kV, 17.5 kV, or 36 kV depending on the incoming supply.
A standard RMU configuration for a loop-fed SEC network is 2L+T (two load-break switches for the incoming and outgoing ring cables, plus one fused or circuit-breaker-protected transformer feeder). More complex configurations 3L+T, 4L+T are used where multiple ring feeds or transformer feeders are required.
2. Power Transformer
The transformer steps down the MV voltage to the LV utilisation level. Package substations in Saudi Arabia use either:
| Transformer Type | Cooling Method | Typical Application | Advantage |
|---|---|---|---|
| Oil-immersed (ONAN/ONAF) | Oil natural / forced air | Outdoor industrial, infrastructure | Lower cost, well-proven, easier repair |
| Dry-type (AN/AF) | Air natural / forced air | Indoor installations, buildings | No fire risk, no oil containment required |
| Cast resin (AN/AF) | Air natural / forced air | Harsh environments, offshore, mines | Highest moisture and contamination resistance |
Standard ratings for Saudi project package substations range from 250 kVA to 2,500 kVA. Larger ratings (up to 5,000 kVA) are available in skid-mounted and containerised formats. Transformer vector groups are typically Dyn11 for distribution and YNyn0 for special applications as specified by SEC or project requirements.
3. Low Voltage (LV) Distribution Panel
The LV panel receives the transformer secondary output and distributes it to the facility's outgoing feeders. In a package substation, the LV panel is factory-wired and tested as part of the complete assembly. It typically includes:
- •Incomer circuit breaker (ACB or MCCB) with metering kWh, kVAR, power factor, demand
- •Outgoing feeder MCCBs or ACBs rated for individual distribution circuits
- •Busbar assembly rated from 630A to 4,000A depending on transformer rating
- •Neutral and earth busbars with appropriate sizing
- •Current transformers (CTs) for metering and protection
- •Capacitor bank terminals for future APFC panel connection (where specified)
4. Protection Systems
Package substations incorporate layered protection to meet IEC and SEC requirements:
| Protection Function | Location | Device |
|---|---|---|
| MV overcurrent & earth fault | RMU transformer feeder | HRC fuses or relay-controlled VCB |
| Transformer overtemperature | Transformer body | Winding temperature indicator (WTI/OTI) |
| Buchholz relay (oil transformers) | Transformer conservator pipe | Gas and surge detection relay |
| LV overcurrent | LV panel incomer | ACB/MCCB with trip unit |
| LV earth fault | LV panel incomer | Residual current relay or ELCB |
| Transformer overpressure (oil type) | Transformer tank | Pressure relief device |
Power Flow Through a Package Substation Step by Step
MV Incoming Supply
RMU Switching and Protection
MV/LV Transformation
LV Panel Distribution
Earthing and Bonding
Indoor vs Outdoor Package Substations
| Parameter | Indoor (Walk-In / Kiosk) | Outdoor (Pad-Mounted / Containerised) |
|---|---|---|
| Enclosure | Steel or GRP kiosk, IP33–IP54 | Weatherproof steel/GRP, IP54–IP65 |
| Ventilation | Natural or forced louvred panels | Forced ventilation with filters rated for dusty environments |
| Climate control | Optional air conditioning | Thermostat-controlled forced ventilation or A/C |
| Access | Walk-in or hinged door panels | Side or end-access doors with padlocking |
| Installation | On concrete pad or raised plinth | Direct ground mounting on prepared pad |
| Saudi suitability | Suitable for temperate zones | Required in outdoor industrial and remote sites |
| Typical Saudi use | Inside industrial buildings, commercial basements | NEOM sites, water plants, oil & gas remote locations |
In Saudi Arabia's outdoor industrial and infrastructure environments where summer ambient temperatures routinely exceed 45°C and windborne sand causes rapid filter clogging outdoor package substations must be specified with Class E2 environmental protection (IEC 62271-202) as a minimum, with forced ventilation systems incorporating sand filters and high-temperature-rated components throughout.
Compliance: IEC Standards and SEC Requirements
Package substations supplied to Saudi projects must comply with the following standards as a minimum:
| Standard | Scope |
|---|---|
| IEC 62271-202 | Primary requirement for factory-built package substations (High-voltage/low-voltage prefabricated substations) |
| IEC 62271-200 | AC metal-enclosed switchgear and controlgear (MV switchboard within substation) |
| IEC 60076 | Power transformers general requirements, temperature rise, losses |
| IEC 61439-1 / -2 | Low voltage switchgear and controlgear assemblies (the LV panel) |
| IEC 60529 | IP degree of protection enclosure classification |
| SEC Distribution Standards | Saudi Electric Company technical requirements for substations connected to the SEC MV network specifies RMU configuration, metering, protection settings, and earthing systems |
| SASO | Saudi Standards, Metrology and Quality Organization mandatory product certification for equipment supplied within the Kingdom |
Where Package Substations Are Used in Saudi Arabia
Industrial Zones (Jubail, Yanbu, Ras Al Khair)
Large manufacturing, petrochemical, and fabrication facilities require multiple package substations to step down from the SEC 13.8 kV or 33 kV ring network to utilisation voltage for motors, welding, and process loads.
Oil & Gas Infrastructure
Remote pump stations, pipelines, and compressor stations use containerised or skid-mounted package substations where conventional civil substation construction is impractical and delivery speed is critical.
Water and Desalination Plants
NWC-operated pump stations and SWCC desalination facilities throughout the Kingdom use package substations for distributed MV-to-LV transformation, with multiple substations serving different process areas.
Commercial Developments
High-rise buildings, shopping malls, and mixed-use developments in Riyadh, Jeddah, and Dammam use indoor kiosk-type package substations in electrical rooms to serve tenant and common area loads.
Giga-Projects (NEOM, Diriyah, Red Sea)
Vision 2030 infrastructure projects require rapid deployment of electrical infrastructure. Containerised package substations are used extensively at construction phase to power temporary camps, manufacturing facilities, and permanent infrastructure.
Universities and Government Facilities
Campus-style facilities such as KFUPM use package substations to distribute power from a central MV ring to individual buildings eliminating the need for a dedicated transformer room in each building.
Frequently Asked Questions
Q: What is the difference between a package substation and a unit substation?
A: A package substation integrates three components in one factory-assembled enclosure: an MV Ring Main Unit (RMU), a transformer, and an LV distribution panel. A unit substation contains only a transformer and LV panel it connects to a separately installed MV switchgear. Package substations are self-contained and require no external MV connections beyond the incoming cable.
Q: What voltage levels are used in package substations in Saudi Arabia?
A: The most common MV incoming voltages for SEC-connected package substations in Saudi Arabia are 13.8 kV and 33 kV, with 11 kV in some legacy systems. LV output is typically 380/400V three-phase at 50 Hz. Standard transformer ratings range from 250 kVA to 2,500 kVA, with larger ratings available in skid or containerised formats.
Q: Are EAMFCO package substations factory tested before delivery?
A: Yes. All EAMFCO package and unit substations are factory assembled and tested before shipment, including high-voltage dielectric tests on MV switchgear, insulation resistance testing on all interconnecting wiring, functional testing of protection relays, and verification of interlocks. A factory acceptance test (FAT) report is provided with each unit.
Q: How long does it take to install a package substation?
A: Because all components are pre-assembled and tested at the factory, on-site installation is significantly faster than a conventional substation. A single compact package substation can typically be placed, cabled, and energised within 1 to 3 days. Multiple unit installations on large projects may require phased energisation over 1 to 2 weeks.
EAMFCO - Factory-Assembled Package Substations for Saudi Arabia
EAMFCO manufactures package and unit substations integrating SF₆ RMUs, oil and dry-type transformers, and IEC 61439-compliant LV panels factory assembled, tested, and documented for Saudi industrial, oil & gas, and infrastructure projects. Continue reading: