Three acronyms fit on the nameplate of a medium voltage (MV) switchgear panel, and they decide how much can be opened while the plant stays in service and what happens to personnel if an arc occurs: LSC, PM/PI and IAC. They are defined by IEC 62271-200, the International Electrotechnical Commission (IEC) standard for metal-enclosed MV switchgear. The Colombian electrical code (RETIE, Reglamento Técnico de Instalaciones Eléctricas), in its current version, Resolution 40284 of 2026 of the Ministry of Mines and Energy, requires the internal arc to be declared on the nameplate, but it does not require a class.

Resolution 567 of 2026 of the UPME (Unidad de Planeación Minero Energética, Colombia's mining and energy planning unit), dated 6 August, recognizes 55 substations of the National Interconnected System whose short-circuit currents exceed the capacity of their circuit breakers, and 36 in a critical state, above 90 percent of that capacity. These are transmission substations, not MV switchgear, but system short-circuit levels keep growing, which is why the kA and the seconds on your nameplate matter.

What does IEC 62271-200 say, and how do you read a switchgear nameplate?

The nameplate summarizes what the manufacturer tested. Take this generic sample nameplate: IEC 62271-200 | Ur 24 kV | Ir 1250 A | 25 kA 1 s | LSC2B-PM | IAC A FLR 25 kA 1 s.

What does LSC mean, and what changes between LSC1, LSC2A and LSC2B?

LSC (Loss of Service Continuity category) indicates which other compartments and functional units can stay energized while one accessible compartment is opened. According to amendment AMD1:2024 of IEC 62271-200, it is assigned only to units with a connection compartment and does not describe reliability levels.

LSC1. Opening an accessible compartment requires taking at least one other functional unit out of service. LSC2. The connection compartment, the cable compartment, can be opened with one busbar section and the other units in service (Switchgear Content, 2 March 2020).

LSC2A. With the unit's circuit de-energized and earthed, other accessible compartments are opened, except the busbar compartment; that unit's cable is not energized. LSC2B. In addition, the connection compartment can stay energized while another one, such as the circuit breaker compartment, is opened, with full compartmentation between busbars, apparatus and connection. The difference lies in the incoming cable: LSC2B makes sense when the cable can be live from the other end, as in ring networks or with generation (Switchgear Content; Schneider Electric, FAQ FA35365).

What is the difference between PM and PI in a switchgear panel under IEC 62271-200?

PM indicates earthed metallic partitions or shutters between the live parts and the open compartment. PI indicates that at least one partition is made of insulating material.

LSC and partition class are independent: if the specification asks for LSC2B but not the partition class, the barrier is left to the manufacturer. And the partition class describes the barrier; protection against the arc is provided by the IAC.

How do you read the IAC A FLR 25 kA 1 s classification of IEC 62271-200?

In IEC 62271-200, IAC (Internal Arc Classified) follows the format "IAC [A, B or C] [F, L, R] [kA] [s]". A means access for authorized personnel; B, unrestricted access, including the general public; C, restricted accessibility by installation out of reach (Schneider Electric, FAQ FA239950). F, L and R are the sides that passed the test: front, lateral and rear. The most common durations are 1 s, 0.5 s and 0.1 s, and a 0.1 s IAC only works if the protection really clears the fault in that time. For example, IAC AFL 12.5 kA 1 s leaves the rear side unclassified.

The test is passed against five criteria: doors and covers remain closed; no fragmentation of the enclosure; no holes in the accessible sides; indicators do not ignite due to hot gases; and effective earthing. Edition 3 adds the "1 s rule": indicators must not ignite during the following second either (Intertek, July 2022).

IAC is not short-circuit withstand, which is tested separately, nor the incident energy of IEEE 1584, which is calculated for the installation. Nor is it the IP and IK rating of the enclosure, which we explained in our 6 October article.

What does RETIE require about IEC 62271-200, and what does it leave to your judgment?

Article 2.3.31.4 of Resolution 40284 of 23 June 2026, published in the Diario Oficial 53.539 of 1 July, requires the internal arc to be declared on the nameplate, without requiring a specific IAC class. It adapts requirements from IEC 62271-1 and IEC 62271-200, among other standards.

It requires a nameplate with 20 minimum data items, including the internal arc classification, the accessibility type, the arc test current and its duration. It does not mention LSC or PM/PI: those decisions stay in your specification.

Paragraph 2 of article 2.3.31.4.2 allows the certification body, while the country has no laboratories, to accept simulations, validated by a laboratory with accredited electrical testing or assisted by a university laboratory, in place of short-circuit and internal arc tests. The certificate must state whether it was based on simulation or on testing.

What should you specify for each type of plant?

Ask who can be near the switchgear, what it costs to shut down the busbars, what the real clearing time is and where the gases exit. If it will go in a transformer substation or a shelter, compare the available height with the test height: in edition 3 it is the minimum height of the shelter or room, and ask for the gas exhaust duct.

What should you check in the IEC 62271-200 test report and at the FAT?

IEC 62271-200 edition 3.0 was published on 27 May 2021 (IEC Webstore) and its amendment AMD1 on 27 June 2024 (IEC Webstore). Some reports still cite edition 2 of 2011, which edition 3.0 replaced.

Specification lesson. Write the complete nameplate into the specification: IEC 62271-200, LSC category, partition class and IAC with letter, kA and seconds. And demand the type test report and the type of RETIE certificate. Declaring the arc is not the same as having tested it.

Frequently asked questions

What is IEC 62271-200 in one sentence?

It is the IEC standard for metal-enclosed medium voltage switchgear. It defines LSC, the partition class (PM or PI) and the IAC internal arc test.

What is the difference between LSC2A and LSC2B?

In LSC2A the unit's cable is de-energized and earthed when another compartment is opened. In LSC2B the connection compartment can stay energized, with full compartmentation between busbars, apparatus and connection.

What does IAC A FLR 25 kA 1 s mean?

It means authorized personnel (A) are protected at the front, lateral and rear sides (FLR) against an internal arc of 25 kA lasting 1 s.

Does RETIE require an IAC class or LSC2B?

No. Resolution 40284 of 2026 requires the internal arc, its test current and its duration to be declared, among other data, but not a specific IAC class, and it does not mention LSC or PM/PI.

Which edition of IEC 62271-200 should I ask for?

The current one is edition 3.0 of 2021 with amendment AMD1 of 2024. Some reports still cite edition 2, which has been replaced: check which edition yours cites.