ABB UniPack-S Steel Compact Substation

International standards followed: from IEC 61330 to IEC 62271-202 ed. 2

Before 1995, there was no unified international standard for prefabricated CSS. In 1995, the International Electrotechnical Commission (IEC) released the first CSS standard IEC 61330 (formerly IEC 1330). This standard is based on IEC 298 (Metal Enclosed Switchgear) and specifies the rated values, design and operating rules, type testing, and routine testing requirements. It covers cable connected substations with transformer capacity not exceeding 1600kVA and significantly improves the internal arc safety level.

Since 2001, IEC has been unifying the relevant standards for medium voltage switchgear, adopting the IEC 62271 numbering system. In 2006, the standard for prefabricated substations was upgraded to IEC 62271-202, based on IEC 61330 and IEC 62271-200. This standard focuses on MV/LV or LV/MV CSS with rated voltage of 1kV to 52kV, frequency of 50/60Hz, cable connection, internal or external operation, and public accessibility.

In March 2014, the second edition of IEC 62271-202 was released, with major modifications including:

Update the temperature rise test method;

Consider electromagnetic field assessment;

Add optional tests;

Consider the impact of the product on the environment;

The internal arc test requirements are adapted to IEC 62271-200:2011;

Assessment requirements for increasing the pressure release volume under the floor.

3.1 Relevant standard system

All internal components of CSS must undergo type testing in advance according to their relevant standards, including:

IEC 62271-1 (General Specification for High Voltage Switchgear)

IEC 62271-200 (AC metal enclosed switchgear)

IEC 62271-201 (Insulated enclosed switchgear)

IEC 62271-202 (High Voltage/Low Voltage Prefabricated Substations)

IEC 60076 (Power Transformers)

IEC 61439 (Low Voltage Switchgear)

IEC/TR 62271-208 (Electromagnetic Field Technical Report)

IEC 60529 (Protection level)

IEC 62262 (Mechanical Shock Protection)

IEC 60721 (Classification of Environmental Conditions)

3.2 Classification of Type Tests

According to IEC 62271-202 ed. 2, type tests are divided into three categories:

Mandatory type tests: dielectric test, temperature rise test, short-time withstand current and peak withstand current test of main and grounding circuits, verification of protection level, calculation or testing of mechanical loads (snow, wind, impact), verification of auxiliary and control circuits.

Mandatory type tests when applicable: internal arc fault test (if IAC level is required), EMC test (complete CSS is usually not required as MV and LV equipment have been tested separately).

Optional tests: Sound level test (agreed upon with the manufacturer and user), electromagnetic field measurement or calculation.

The internal arc test is very important to ensure the safety of operators (IAC-A level) and the public (IAC-B level) when internal arcs occur under normal operating conditions.

Detailed explanation of UniPack-S structural design

4.1 Construction Composition

The UniPack-S casing is an above ground building installed on site foundations (ABB can provide additional or integrated foundations). Non walk-in is used for external operations, and there is an operating channel within the walk-in station.

4.2 Materials and Corrosion Protection

The standard shell is made of galvanized steel plate, which has higher corrosion protection than painted black steel. Galvanized metal parts are pre treated and further coated with pure polyester powder coating. According to ISO 12944, surface treatment corresponds to corrosion grade C4 H. Hot dip galvanized steel sheet ensures long-term mechanical life.

4.3 Ventilation system

Natural and effective ventilation is achieved through the air inlet on the door or ventilation wall components. Hot air is expelled from the top ventilation louvers. ABB has designed an efficient ventilation system that provides enclosures with low temperature ratings (10K or 20K) to enhance transformer performance and lifespan. For hot climates or continuous heavy-duty transformers, it is strongly recommended to use low-temperature grade enclosures. ABB can conduct thermal simulation as required to optimize the lifespan of transformers.

4.4 Roof

UniPack-S provides separate roofs for MV switchgear room, LV distribution panel room, and transformer room. The roof of the transformer is detachable, making it easy to install and maintain the transformer. The roof has two slopes: standard 6 degrees and 18 degrees for heavy snow weather. The roof design can withstand a minimum uniformly distributed load of 250kg/m ².

4.5 Doors

The door is made of pre galvanized steel plate, with a sturdy structure to prevent unauthorized entry, providing high IP rating, and protecting the public during internal arcing. Standard stainless steel hinges with high corrosion resistance and bending rigidity. According to the variant, use 2-point or 3-point locking (3-point locking provides better functionality and safety). The transformer room door is also equipped with safety barriers to remind operators to follow safety measures and prevent accidental entry. The walk-in CSS can be equipped with an internal door handle and an emergency push rod lock.