Jean Constantinescu

ISBN 978-606-92862-0-3
Editor: ROENP
Cover picture: Pablo Picasso, 1932

Keywords: unbundling; power system; system model; de-regulation; energy services; system operation and control; system functionality

Importance of the field and why it is likely to be of interest to readers

The unbundling approach may be recommended, firstly, for its ability to simplify the matters through reduction of their size. Simpler issues, simpler solutions and, frequently overlooked, easier reasoning on them. The models of electric power systems became considerably complex due to continuous physical interconnection. The unbundling joins the outstanding trends towards set up of de-regulated electricity markets and "parallelization" of numerical computation, as well. Unbundling of power systems' models and functions can bring significant gain of efficiency and clearness in the systems' solution.


"Unbundling" (lat. - disligare; rom. - dezlegare) is a word full of significance in a number of languages including the Romanian, designating solution or reveal of a complicated matter. The more intricate an issue, the righter does appear an "unbundling" approch.

By game of chance, the author has dealt with electricity, with the power system (PS) functionality particularly. As a biginner in PS research, he was strongly marked by the diakoptics method that Gabriel Kron proposed in early 50'. The book gathers related findings from a research work that has spread on more than 40 years and may still have contemporary significance. Presented models and methodes are not simply theoretical conjectures. In general, they were implemented in computer codes, most of them being production codes used in the operation and planning of Romanian PS.

By mere coincidence, the author's steady interest for unbundling PS operational models met the recent, overwhelming, trend towards deregulation of electric market. Or, competition can be only achieved if the basic services of power system are unbundled as against the electricity customers. In the last two decades, the unbundling of electricity services has everywhere become a news of the day for electricity, and the author has the chance to bring a modest contribution to this area of energy reform in Romania.

Facing of a new power system model, we are firstly trying to identify the relevant variables and process components (subsystems) that can be settled separately. Afterwards, we seek for the "system conditions" that offer the basis for articulation of individual solutions. A successful "interconnection" pattern is actually the critical step in the solution process. So, in general, the unbundling includes steps in which solutions of the subsystems are determined, and steps these "partial" solutions are "interconnected".

The unbundling would be of variables if solution interconnection signified "correction". The unbundling would be of processes if interconnection appeard as simply assembly of partial solutions, since a pre-established computational accuracy was already ensured. Decoupling is a particular unbundling with only two subsystems.

Considering the physical nature of interdepencies that are candidating to unbundling, and the particular partitioning criterion, the following three classes of unbundling can be identified:
a)        Inter-action (functional) unbundling whereby subsystems are the result of neglecting relatively weak functional inter-actions.
b)        Spatial (structural) unbundling whereby the subsystems are the result of decomposition of a network - structured model.
c)        Temporal (variational) unbundling whereby the subsystems are the result of variable and process separation on the time domain, during certain time periods or over the whole simulation time.

NB. It is a bilingual book, Romanian and English, with 167 pages.