Why Prequalification is becoming increasingly important

In order to select the new assets according to their technical feasibility before any pricing issues are evaluated, a prequalification process can be introduced that a manufacturer and their product have to undergo before applying for a tender.

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Why Prequalification is becoming increasingly important

At first glance, incorporating an additional step in the tender process does not make sense. However, a second view, with more detailed insight, establishes it is a very important step for efficient work practices and for increasing the quality of the assets. Many utilities struggle with the multitude of the manufacturers’ devices. Before ordering new assets, they may publish a tender voluntarily or are required to publish a tender that describes the requirements which have to be fulfilled by the product. In order to select the new assets according to their technical feasibility before any pricing issues are evaluated, a prequalification process can be introduced that a manufacturer and their product have to undergo before applying for a tender.

Such a process segregates the technical requirements and the commercial interests. In addition, the technical requirements can be continuously checked, even if there is no tender published. After the manufacturer, has prequalified, they can apply for tenders within the next, for instance, 4 years without recertification as long as the main features of the product do not change in the meantime.

Important steps in a prequalification process

The prequalification procedure consists of several steps (fig 1). They are ordered in such a manner that the first steps deal with quite general issues that could be applied to all new assets, independent of whether they are transformers, circuit breakers or protection devices.  The later steps are very specific and, in the case of protection devices for example, can describe the prequalification procedure for certain protective functions in detail (a distance protection device is used in this example).

  • Application for prequalification: The manufacturer applies for prequalification for a certain product category. The utility informs them about the process, sends them the specification sheet and invites them to deliver the necessary documents.
  • Check of suitability of manufacturer: The utility checks if the manufacturer is suitable in general, for instance, if they have technical support, enough resources to produce the assets, or how long spare parts are available.
  • Product check according to the specification sheet: The manufacturer returns the necessary documents (including features of the product, test results, etc.)
  • Using a ranking system given by the specification sheet, the utility rates the product.
  • Further product tests: For new manufacturers, the utility can initiate further tests according to:

o   Commissioning guidelines of the utility

o   IEC 60255-121

o   IEC 61850

o   Critical faults from the past

o   Influence of CT saturation

o   Performance with relays of other manufacturers.

Fig.1 Steps of Prequalifi cation

How does this process deal with quality and efficiency?

For quality management, it is essential to document the process. This is also valid for the prequalification process which requires:

  • Rules of procedure
  • Application form for prequalification
  • Eligibility requirements in general
  • Installation of a scoring system
  • Eligibility requirements for protection devices
  • Process description in general
  • Description of protection functions for 400-kV-network
  • Description of protection functions for transformers
  • Typical protection settings etc.

With a documented procedure, the comparison of assets from different manufacturers will be achieved. All assets have to undergo the same tests and from a technical point of view, the best one will be found. The tests in a prequalification procedure can be developed in a way which allows most parts to be used directly for any assets (same type of asset). This leads to shorter test times and with comparable results.


The manufacturer is obliged to inform the utility about any changes of hardware and software. In addition, changes to the user software have to be indicated. If there are significant modifications, the utility can decide:

  • If no technical check is needed
  • If a technical check of the changed functions is needed
  • Or if a complete check is needed.

This approach can also be used to keep the number of recertification procedures low.

Fig.2: Test scenario for dynamic tests
Fig.3: Test results for IEC60255-121 tests


This procedure has several benefits:

  • It decouples the prequalification from the tender, no time pressure
  • The utility knows that the product will work properly in the power system
  • There is a clear ranking between the different products that passed the test
  • The procedure can be out-sourced to an institute of certification
  • The manufacturer can use the prequalification document for marketing issues.

The prequalification process can be applied to any type of asset used by a utility. The manufacturers and their new asset have to undergo numerous tests which will conclude with a prequalification certificate. This approach guarantees that only devices which are suitable for the utility are offered during the tendering process.

With experience from several projects in the field of prequalification, OMICRON can also be your partner in analysing existing procedures and setting up an optimised prequalification and certification procedure.