Network Protection & Automation Guide (NPAG)

In order to provide the modern practicing substation engineer with reference material, AREVA's Network Protection & Automation Guide provides a substantially revised and expanded edition of PRAG incorporating new chapters on all levels of network automation.


The first part of the book deals with the fundamentals, basic technology, fault calculations and the models of power system plant, including the transient response and saturation problems that affect instrument transformers.

The typical data provided on power system plant has been updated and significantly expanded following research that showed its popularity.

The book then provides detailed analysis on the application of protection systems. This includes a new chapter on the protection of a.c. electrified railways. Existing chapters on distance, busbar and generator protection have been completely revised to take account of new developments, including improvements due to numerical protection techniques and the application problems of embedded generation. The chapter on relay testing and commissioning has been completely updated to reflect modern techniques. Finally, new chapters covering the fields of power system measurements, power quality, and substation and distribution automation are found, to reflect the importance of these fields for the modern power system engineer.

The intention is to make NPAG the standard reference work in its' subject area - while still helping the student and young engineer new to the field.

To obtain the NPAG book, by download or CD-ROM, please use the contact form in the link below.


The following is a short description of the content of the individual chapters of NPAG:

Chapter 10 Unit Protection of Feeders

The graded overcurrent systems described in Chapter 9, though attractively simple in principle, do not meet all the protection requirements of a power system.
Application difficulties are encountered for two reasons: firstly, satisfactory grading cannot always be arranged for a complex network, and secondly, the settings may lead to maximum tripping times at points in the system that are too long to prevent excessive disturbances occurring.

These problems led to the concept of 'Unit Protection', whereby sections of the power system are protected individually as a complete unit without reference to other sections. One form of 'Unit Protection' is also known as 'Differential Protection', as the principle is to sense the difference in currents between the incoming and outgoing terminals of the unit being protected.

Other forms can be based on directional comparison, distance teleprotection schemes or phase comparison protection.

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