New challenges for natural gas distribution network operators arise, due to the liberalization of the energy markets and the started regulation of natural gas networks in Europe. Regulation authorities compare the efficiency of different network operators and limit the profit of inefficient networks. In order to obtain revenues, natural gas network operators are forced to increase the efficiency of the networks. An exclusive consideration of network costs to determine efficient network structures entails the risk of a cost-based reduction of the reliability of supply. Therefore the reliability of supply has to be considered as a boundary condition during the network planning process.

In this paper the combination of two computer-based methods is presented in order to estimate cost-efficient natural gas distribution networks under consideration of the reliability of supply. First, a heuristic optimization method to calculate long term cost-efficient network structures based on Genetic Algorithms is introduced. The objective function of the method is the minimization of network costs including equipment costs, costs for pipe laying and underground engineering as well as operational costs. For this purpose the position of customers and their feed-in or demand, the topography of the supply area and the position of usable routes are needed as input data. The degrees of freedom are the number and feed-in pressure of pressure regulators, the choice of usable routes and dimensioning of equipment. The calculated networks fulfill all technical and economical boundary conditions. The second part of this paper presents a method to evaluate the reliability of supply. Input data of this method is the estimated cost-efficient network. Via a Monte-Carlo-Simulation the reliability parameters for the given network, as frequency of interruptions, endurance of interruptions and non-availability, are calculated. Hereby areas of poor reliability can be identified and passed to a second iteration of the network planning process in order to improve the reliability by considering the reliability of supply as an additional boundary condition.

At the end of this paper exemplary results are presented to verify the functionality of the described method. Therefore a real natural gas network is analyzed. At first, reliability parameters of the existing network are calculated in order to have a reference value. Afterwards a cost-efficient network is estimated for the given supply task by means of the computer based optimization method. The cost reduction as well as the impact of the network optimization on the reliability is shown.

  1. Introduction

  2. Network Optimization

  3. Reliability of Supply

  4. Exemplary Results

  5. Conclusions


In the liberalized European energy market customers may choose their power supplier. Therefore, a non-discriminating grid access for all power suppliers must be guaranteed. In order to reduce the transmission fees and increase their transparency an incentive regulation has been established in Germany 2009. Transmission fees are limited depending on the relative efficiency of the network operator. As a result of the regulatory framework in the European power and gas markets distribution companies are facing a high cost pressure.

This content is only available via PDF.
You can access this article if you purchase or spend a download.