Almost every panel manufacturer in India prints the same three words in its brochure: type tested assembly. Very few can put the laboratory report on the table. A framed certificate tells you nothing unless you know what was done to the panel behind it.
At Accu-Panels Energy we build LT electrical panels for solar plants, industrial facilities, hospitals and infrastructure projects, and between December 2023 and February 2024 we had our 800 V, 3,200 A reference design verified by test at CPRI. This article explains what “IEC 61439 type tested” actually means in the language of the standard, walks through the four tests in our CPRI report with the applied values and results, explains why a design verification is only half the story, and lists the questions I would ask any panel supplier. It is written for buyers, consultants and plant engineers who have to sign off a switchboard.
Figures reflect published standards and product documentation as of November 2026.
Key facts at a glance
- Laboratory and reference: CPRI STDS Bhopal, APEPL/23-24/CPRI/01, Dec 2023 – Feb 2024
- Reference design: 800 V, 3,200 A LT panel
- Short-circuit withstand: 50 kA r.m.s. for 1 s, 105 kA peak, no abnormality
- Impulse and power-frequency: 9.3 kV peak 1.2/50 µs both polarities; 2.7 kV r.m.s. 60 s
- Degree of protection: IP55; IR > 2,000 MΩ after test
In this guide
What “IEC 61439 type tested” means in the standard’s own terms
IEC 61439 does not use the phrase “type tested”. The older IEC 60439 had type-tested and partially type-tested assemblies; IEC 61439 replaced them with design verification of the reference design (by test, by comparison with a tested reference design, or by assessment, per IEC 61439-1:2011, Table D.1) and routine verification of every assembly before it leaves the works. When the market says “type tested”, the correct reading is design-verified to IEC 61439 (verified by test) at an accredited laboratory. Two checks can never be done by assessment alone: short-circuit withstand (test or comparison only) and the dielectric tests. Those are the pages of the report to read first.
Four tests, one panel, one laboratory
We sent a single reference assembly, an 800 V, 3,200 A LT panel, to the Switchgear Testing and Development Station of the Central Power Research Institute (CPRI STDS) at Bhopal, under reference APEPL/23-24/CPRI/01. The laboratory then tried four ways to break it.
1. Short-circuit withstand
The main horizontal busbar carried 50 kA r.m.s. for one second, with an initial peak of 105 kA. That peak is what IEC 61439-1:2011, Table 7 expects: for a prospective current in the 20–50 kA band the factor n is 2.1, and 2.1 × 50 = 105 kA peak. The report records no abnormality, all busbars and supports intact and the fine-wire fuse intact (the fuse across the circuit is the laboratory’s indicator that no arc occurred). Afterwards the assembly withstood 2.5 kV r.m.s. for 60 s to show that the insulation had not been damaged. The rating is therefore Icw = 50 kA for 1 s and Ipk = 105 kA, two different quantities that should never be quoted as one number.
2. Temperature rise
The incoming feeder, rated 3,200 A behind a 4,000 A air circuit-breaker, and two outgoing feeders at 630 A and 250 A were loaded at full rated current for three days while thermocouples recorded every joint and terminal. IEC 61439-1:2011, Table 6 sets 70 K for terminals of external insulated conductors, or the lower limit declared by the device manufacturer; the ACB manufacturer’s declared terminal limit of 65 K was the governing figure. Every point stayed within its limit. A second 2.5 kV r.m.s., 60 s dielectric test followed. Temperature rise is reported in kelvin above ambient, not in degrees Celsius.
3. Impulse and power-frequency withstand
An impulse of 1.2/50 µs waveform at 9.3 kV peak, corrected for the altitude of Bhopal, was applied to the main circuit in both polarities with no disruptive discharge. For reference, IEC 61439-1:2011, Table 10 lists 9.8 kV at sea level falling to 8.0 kV at 2,000 m for a declared Uimp of 8 kV, which is the preferred value for an 800 V system at the origin of the installation (Table G.1). The main circuit then held 2.7 kV r.m.s. for 60 s. Metal foil was wrapped around the operating handles of the 4,000 A ACB, the 630 A MCCB and the 250 A MCCB to simulate a hand, and 4.05 kV r.m.s. was applied to each for one minute, that is 1.5 times the main-circuit value; all withstood.
4. Degree of protection IP55
IP55 does not mean hermetically sealed. Under IEC 60529 the first numeral 5 permits limited dust ingress provided it does not interfere with safe operation, and the second numeral 5 permits limited water ingress from jets on the same condition. Small powder traces after the dust chamber and minor moisture traces after the water jets were observed, which is IP55 behaving as designed. Insulation resistance measured above 2,000 MΩ after the test, and the enclosure then withstood 2.5 kV r.m.s. for one minute.
The figures above are from the provisional report; the institute’s final formal documentation followed with identical verified values.
Results at a glance
| Test | Applied value | Limit or criterion | Result |
|---|---|---|---|
| Short-circuit withstand | 50 kA r.m.s. for 1 s; 105 kA peak | No deformation, supports intact, fuse intact; Ipk ≥ n × Icw with n = 2.1 (Table 7) | No abnormality; passed |
| Dielectric after short circuit | 2.5 kV r.m.s., 60 s | No breakdown or flashover | Withstood |
| Temperature rise | 3,200 A incomer (4,000 A ACB), 630 A and 250 A outgoing, three days | ACB terminals ≤ 65 K (manufacturer limit); Table 6 limits elsewhere | Within limits at every point |
| Dielectric after temperature rise | 2.5 kV r.m.s., 60 s | No breakdown or flashover | Withstood |
| Impulse withstand | 1.2/50 µs, 9.3 kV peak (altitude-corrected), both polarities | No disruptive discharge | Passed |
| Power-frequency withstand, main circuit | 2.7 kV r.m.s., 60 s | No breakdown or flashover | Withstood |
| Power-frequency, foil-wrapped handles | 4.05 kV r.m.s., 1 min on each handle | No breakdown (1.5 × main-circuit value) | Withstood |
| Degree of protection | IP55 dust chamber and water jets | Limited traces permitted; safe operation maintained | Passed; IR > 2,000 MΩ; 2.5 kV 60 s withstood |
One design tested, then every unit verified
A design verification by test proves that the architecture survives extreme short circuits, thermal load, surges and the environment. It does not prove that the specific panel delivered to your site was wired and assembled correctly. That is the job of routine verification under IEC 61439-1:2011, Clause 11, which every assembly receives before packing:
- Insulation resistance at 1,000 V DC across all circuits, recorded.
- Dielectric test phase-to-phase, phase-to-neutral and phase-to-earth at the standard’s levels, with zero tolerance for flashover.
- Protective-earth continuity measured in milliohms and compared against the allowed limit.
- Mechanical checks of doors, interlocks, handles and operating mechanisms.
- Calibration traceability for every instrument used.
The design test validates the design; the routine test verifies the unit in front of you. A buyer needs both, and both should be serial-numbered.
Why untested panels still sell
On day one a verified panel and an unverified assembly look identical: the same paint, switchgear and ferruling. The difference appears in year three, at two in the morning, when a cable fault drives fault current through a busbar joint never proven to withstand it. Price comparisons rarely include that night.
Five questions every buyer should ask
- Which accredited laboratory tested this design, and can I see the complete report rather than a one-line certificate?
- At what short-circuit current and duration, and what peak? (For example 50 kA for 1 s, 105 kA peak.)
- What was the maximum measured temperature rise at the terminals where my cables connect, and what was the allowed limit?
- Does every panel receive its own serial-numbered routine verification report?
- If my layout differs from the tested reference design, how were the deviations verified? Comparison with the reference design uses the checklist of IEC 61439-1:2011, Table 13; any “no” in that checklist means a test is required.
Choosing the hard route
Design verification by test costs capital and months, and it can expose weaknesses that must be re-engineered. Routine verification adds an inspection station and documentation to every panel. We chose both because operators stand in front of these switchboards every day. Leading international manufacturers describe the same two-layer approach in their published documentation; it is what the standard was written to require.
Standards referenced: IEC 61439-1, IEC 61439-2, IEC 60529; laboratory and certification bodies: CPRI and BIS. The verified platform is applied across the Accu-Panels Energy range: a typical specification reads a PCC panel or MCC panel with Icw 50 kA for 1 s, or an 800 V LT panel with Uimp 8 kV, each with a routine verification report issued under the quality process described above.
Frequently asked questions
Is a CPRI report valid for every panel the manufacturer builds?
It is valid for the tested reference design and for variants verified by comparison with it under IEC 61439-1:2011, Table 13. A layout outside those limits needs its own verification.
Why are Icw and Ipk quoted separately?
Icw is the r.m.s. current the busbar carries for a stated time and governs heating; Ipk is the first peak and governs the mechanical force on supports. Table 7 links them through the factor n, 2.1 in the 20–50 kA band.
Does a routine test replace the design verification?
No. Routine verification checks workmanship and dielectric integrity of one unit; it does not subject the busbar to fault current or full-load heating. Both are required.
Related reading
Disclaimer. This article is general engineering information based on published standards and product documentation as of November 2026. Ratings, settings and protection schemes must be confirmed by a qualified engineer for each installation. Nothing here is a design specification.
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