According to a survey carried out in eight utilities by the CIGRE Task Force 34.06 (2002), reliability indexes were between 92% and 97.5%. The three utilities with the best indexes, above 97%, had carried out an extensive refurbishment program of their protection system. Although this may seem obvious, it must be emphasized

that refurbishment is the easiest way to achieve protection reliability improvement.

There are two main drivers for refurbishment:

Measurement Equipment

The measurement equipment used is as follows:

• Increasing protection requirements are coming from the grid. For example, in the case of Spain there has been an increase in load of 32% in the last seven years. This increase has resulted in a reduction of critical clearing times and new requirements for protection.
• Protection assets are becoming older. According to aforementioned CIGRE Task Force, 40 to 50% of the protection relays of some utilities were electromechanical and more than 30 years old.

Taking these two facts into account, we must think of protection as a strategic asset that should be able to cope with more and more demanding requirements from the grid now and in the future. In order to achieve this, state of the art protection systems will need to be installed in the grid.

But let's go even further -- improvements in reliability that can be obtained from new digital relays. According to

Iberdrola's experience with causes of protection failure in new substations, only around 15% of the failures are internal to the relays. However, 40% of the failures are outside the relays, mainly due to wiring. and 45% of the failures are caused by setting errors. The good news is that 85% of these failures could be eliminated by the utility.

Consider the three main ways to achieve reliability improvement:

• Standardization: in order to reduce engineering and construction errors.
• Commissioning testing: in order to identify and correct these errors.
• Fault analysis: in order to detect any faulty operation

Modern protection and control systems offer new opportunities for improvement in these three approaches.

Here are examples of best practices:

Standardization

Red Eléctrica de España (REE), which is the TSO in Spain, is carrying out a very ambitious protection refurbishment campaign in the whole transmission system. The key to achieving their goal is standardization and wiring reduction.

This standardization has allowed REE to increase the reliability of their protection system and to fulfill deadlines with their refurbishment program.

Commissioning testing

New devices based on IEC 61850 allow for new functionality. Therefore testing can be carried out directly from the configuration files of the substation and completed automatically. This opens new opportunities to reduce testing time and more efficient identification of failures.

Fault analysis

These days, with new digital protection, the problem is not having the information, but how to deal with it.

• In this respect, we think that protection management systems are crucial. The system we are using in Iberdrola covers the functions of communication with relays, fault analysis tools, setting database and fault database. This system is the heart of our protection organization and helps us to achieve our goal of attending and correcting significant protection failures in 24 hours.
• A second step would be to develop analysis tools to automatically help the engineer with a diagnosis. However, in order to do this, standardization is essential.

It's clear that digital technology offers new opportunities for improvement; there are also several drawbacks, related with people. Protection engineers have difficulties with the new protection constraints such as:

• Complexity. A modern relay usually has 200 or more parameters to be adjusted.
• Relays become obsolete quite rapidly. And within the life span of each relay, versions are changed several times.

Version control is probably the main problem with digital technology.

• Protection people need new skills to deal with Information Technology. For example, in the past it was quite easy to change a wired signal connected to a relay. Now, to change the configuration of a multi-vendor SAS could be a really complex task.
• Of course, there are also the well-known constraints of less commissioning time, fewer resources and difficulties to recruit new staff; but these are not only related to digital technology.

How can we solve all these problems? I believe that the only solution is a black-box approach. Protection engineers should be able to work with different models of relays in a conceptual way. We should be able to work using the same tools and with the same functional models. This will allow us to gain experience and give added value to our work. Please try to focus on this basic knowledge and try to avoid spending time with details that will be useless in the short term.

Going back to the improvement based on standardization, in Iberdrola we think that the key to this approach is standardization based on IEC 61850. That is the reason why we have developed a multivendor IEC 61850 based SAS. The first substation was commissioned last year and this year we have three new IEC 61850 substations projects.

In conclusion, my opinion regarding the application of digital protection and control by utilities could be summed up in two ideas:

• Protection is the strategic asset to support the new requirements and constraints on the grid, now and in the future.
• Protection engineers have never before had so many and such challenging opportunities to improve reliability.