Medium Voltage Packaged Unit Substations


Modular systems built for flexibility within a small footprint

Our prefabricated unit substations provide comprehensive coverage from medium to low-voltage requirements and include essential components such as transformers, switchgear, protection technology, measuring systems and monitoring capabilities.

Main Technical Parameters

All the benefits of a standard substation without needing a full civil-designed building. Our packaged substations include fully functional HV/LV switching, control and protection, metering, reactor compensation and more. With the added advantages of small substation footprint, flexibility to move and relocate, low capital investment, unobtrusive and attractive appearance – our packaged substations are designed for use in high-rise buildings, residential districts, municipal facilities, industrial and mining enterprises, oilfields, ports, airports, construction site, roads, wind power plants, etc., and they will work in both indoor and outdoor settings.

  • Civil Cost
    • Land (30% space savings)
  • Construction Cost
    • Time (Decrease of time on site by 40%)
    • Material Availability
    • Labor Availability
  • Overall Cost
    • 25% lower than traditional substations
  • Quote Lead time
    • 3-4 Week Lead Time
  • Drawing Lead time
    • 3-4 Weeks after receipt of order
  • Product Lead time
    • 26 weeks after approved drawings
  • Flexibility
    • Ability to use multiple inverters and LV technology
  • Global Presence
    • 1800 Shipped substations
  • Factory Control
    • Testing and coordination details are handled by (1) OEM
    • Quality controlled in Factory setting
  • Knowledge and Engineering Capability
MV Equipment Description Unit Parameters
Rated voltage kV 7.2 15 27 38
Rated frequency Hz 50/60
Rated current of main circuit A 630 1250
Rated short-time withstand of the main circuit kA 20
Rated peak withstand current of the main circuit kA 50
Rated short-circuit duration S 3
Power-frequency withstand voltage, interphase, ground-to-ground and ordinary fracture/isolating fracture kV 32/36 43/49 95/110
Lightning impulse withstand voltage, interphase, ground-to-ground and ordinary fracture/isolating fracture kV 60/70 5/85 185/215
LV Equipment Rated Voltage kV Less than or equal to 1
Rated current of main circuit A 10 - 4000
Rated short-time withstand current kV 15 30 50
Rated peak withstand current kV 30 63 105
Rated current of branch circuits and number of circuit Line A Customized
Reactive compensation capacity kVAR 0 -------- 30%
Transformer Rated capacity kVA 50 -------- 5000
Rated voltage on the primary kV 3 -------- 35
Rated voltage on the secondary side kV Less than or equal to 1 (except for power transformation)

Skid & Container Solutions

The YB-series medium voltage prefabricated substation is a box made up of the HV/LV switchgear, distribution transformer, metering devices for electric energy and compensation devices for power factor, etc., serving as complete sets of power distribution and transformation unit in the power distribution and transformation grid with a rated frequency of 50Hz/60Hz.

Operating Conditions

Maximum temperature: +40°C; minimum temperature: -10°C (ordinary areas) and -25°C (alpine regions)

Enclosure: Rated for outdoor use.

Ground acceleration: Suited for standard and seismic applications.


This product is intended to be installed with predefined conduit entries and an approved surface to support weight. The packaged substation will greatly reduce labor and commissioning time on-site. If any special service conditions are required for installation, inform JST of any requirements. The special service conditions (if any) shall be proposed by and confirmed prior to order placement.

The Model & Meaning
  • Model of the box-type substation: YB-□/□-capacity (□ depending on the rated voltage on the HV/LV side)Rated capacity: 30~3,800kVA; if the capacity is larger than 3,800kVA, consult the technicians of the Company to provide a separate scheme.

    HV/LV rated voltage: The rated voltage ratio (7.2, 15, 27, 38 generally on the HV side; 0.27, 0.315, 0.4, 0.48, 0.52 and 0.69 generally on the LV side) on the HV and LV side.

    Example: YB-15/480-2,500

Transport & Rigging

Easy to handle and easy to transport. Our packaged solutions come with standardized interfaces, such as ISO-container corners, for quick and simple fastening, lifting and rigging. All while remaining within international transport requirements and not requiring oversize transport.

Maintenance & Repair

The electrical equipment (including the switchgear and transformers) inside the product shall be checked and maintained regularly, per the requirements in the installation instructions and relevant provisions. Impact with hard objects should be avoided, as it could damage the anti- corrosion protective coating. The door of the HV/LV switchgear may be opened, or the panel may be removed for ordinary maintenance from the front side. In case of overhaul or replacement of main equipment, the fixed nut of the top cover shall be removed. Lift the top cover away and then lift out the transformer or the switchgear for overhaul or replacement.

Ordering Information

The purchaser shall provide the following data related to the product during ordering:

  1. Type and capacity of the transformer and configuration of accessories.
  2. Wiring scheme of the HV/LV chamber and the specifications and model of electrical elements.
  3. The enclosure is routinely offered in ivory white or in light green. If a special color is needed, provide factory with sample. Customizing is required in case of special color requirements.
  4. Other client requirements may be requested during ordering.

The inclination shall not exceed 30° during product transportation. The vulnerable elements (such as the energy meters) during transportation may be removed before long-distance transportation. Anti-shock packages shall be used separately, and such elements shall be recovered after arriving at the destination. The product shall be placed at the normal usage position during transportation, and the transporting tools shall be fixed firmly to the base or the packing place. The products shall be free from movement and obvious shaking during transportation. Other positions are not allowed except for the hook at the base and the lifting rings at the top.

Premier Customer Service

Detailed Engineering & Technical Support

Industry Leading Lead Times

Fast Response

Flexible Solutions

Dedicated Project Managers

We Will Never Force A Solution. We Will Engineer The Answer.

We continually work to create products with higher efficiencies and better value. Each year we make substantial investments in the research & development of new products and manufacturing techniques.

We regularly innovate on behalf of our customers, collaborating with them to find solutions to their specific challenges.

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Meet The Experts

“Why JST? Our transformers combine superior quality without compromising on lead time.”

Emerson M.


“Our quality is your peace of mind. This promise extends from the initial delivery to when our products are in service. Feel free to send us any after sales service request you may have. We are here to help.”

David D.


“Engineered to value – this is reflected in the concise level of detail of our proposals and in the quality of our finished product.”

Juan E.


“We offer expert and end-to-end-support from the moment we receive your request until your switchgear is delivered.”

Rebeca C.


“Our switchgear is designed and tested according to industry standards, while reflecting best practices and learnings we have gathered as a manufacturer.”

Valeria G.


“Are you looking for a quality response on your transformer and switchgear needs? JST is here for you: with our team of experts, proven track record and industry insight.”

Jonathan W.


Have questions? Contact our team.

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Office Headquarters

30 Skyline Drive
Lake Mary, FL 32746


Contact Us

+1 407-632-4050
1-844-631-9046 (Toll Free)