Juan Carlos Cebrian

Hybrid Method to Assess Sensitive Process Interruption Costs Due to Faults in Electric Power Distribution Networks

This paper shows a new hybrid method for risk assessment regarding interruptions in sensitive processes due to faults in electric power distribution systems. This method determines indices related to long duration interruptions and short duration voltage variations (SDVV), such as voltage sags and swells in each customer supplied by the distribution network. Frequency of such occurrences and their impact on customer processes are determined for each bus and classified according to their corresponding magnitude and duration. The method is based on information regarding network configuration, system parameters and protective devices. It randomly generates a number of fault scenarios in order to assess risk areas regarding long duration interruptions and voltage sags and swells in an especially inventive way, including frequency of events according to their magnitude and duration. Based on sensitivity curves, the method determines frequency indices regarding disruption in customer processes that represent equipment malfunction and possible process interruptions due to voltage sags and swells. Such approach allows for the assessment of the annual costs associated with each one of the evaluated power quality indices.

Probabilistic Assessment of Financial Losses in Distribution Network Due to Fault-Induced Process Interruptions Considering Process Immunity Time

This paper introduces a stochastic methodology to assess annual performance of distribution network and individual customers with respect to voltage sags, long duration interruptions, equipment trips, and process trips. These values are then used to evaluate financial losses in the entire distribution network. For each of the large number of simulated faults throughout the network, a probability of sag and long duration interruption occurrences is evaluated at each network bus. The methodology then includes for the first time the concept of process immunity time in order to assess as accurately as possible the resulting financial loss due to process interruption. To increase the accuracy of the assessment of financial loss, the methodology also considers the possibility of equipment and process restart, reliability, and type of fault. The methodology is illustrated on a real distribution network and it shows that inclusion of PIT in financial loss assessment results in a reduction of about 25% in estimated financial loss.

Genetic algorithms applied for the optimal allocation of power quality monitors in distribution networks

This paper presents a methodology which determines the optimal allocation of power quality monitors, in order to monitor the occurrence of voltage sags and swells in distribution networks. Initially, the methodology characterizes the system under analysis regarding the occurrence of voltage sag and swells. This characterization is performed through the simulation of several short-circuits at different points of the system being studied and taking in to consideration several conditions (fault impedance, fault type, etc.). For this purpose, a new method that defines the most relevant short-circuit conditions is proposed. After the systems characterization, the methodology makes use of Genetic Algorithms (GA) to define the minimum number of monitors required to monitor the whole system, and also the places where these monitors should be installed in the power network.

Probabilistic Estimation of Distribution Network Performance With Respect to Voltage Sags and Interruptions Considering Network Protection Setting—Part I: The Methodology

Nowadays, modern industrial processes are controlled by equipment highly sensitive to voltage sags and interruptions. Although the proposed methods in the literature allow utilities to estimate annual equipment trips due to voltage sags and permanent interruptions, they do not assess explicitly momentary interruptions. This paper proposes a probabilistic methodology that includes the attempts of reclosers to clear nonpermanent faults during the estimation of annual voltage sags and momentary interruptions at each busbar. Furthermore, voltage-tolerance ranges for each type of equipment are taken into account to quantify annual equipment trips due to voltage sags and momentary interruptions for each customer in the distribution network. The results allow the utility to identify a geographic area where sets of customers face high equipment trips during the year. The proposed methodology can be used by utilities to prioritize corrective measures to improve the quality of service to those customers most affected by annual equipment trips.

Probabilistic Estimation of Distribution Network Performance With Respect to Voltage Sags and Interruptions Considering Network Protection Setting—Part II: Economic Assessment

Significant financial losses due to voltage sags, short duration interruptions (SDIs), and long duration interruptions (LDIs) have been reported over the past years. The methods proposed in the literature allow us to estimate the annual indices related to process trips, though, as they are confined to voltage sags and LDIs, they do not take into account SDIs. This paper proposes to estimate annual financial losses related to process trip (FLPT) for each customer in the distribution system. The methodology correlates the attempts of reclosers to clear nonpermanent faults along with the concept of process immunity time in order to separately estimate the annual FLPT due to voltage sags, SDIs, and LDIs. This division allows the utility to quantify the severity of each of them and identify geographic areas where mitigation solutions should be deployed to avoid customer complaints and penalties by regulatory agencies.

Restoration in Distribution Systems to Reduce Financial Losses Related to Process Trips

An important step toward a smart grid is the “smart” application of manual or automated sectionalizing switches, which can be operated in contingency conditions in order to improve the reliability indices. However, electric utilities do not have well-defined criteria for allocation of such devices. In this paper, annual financial losses related to process trips (AFLPT) are assessed taking into account - in a probabilistic manner - process immunity time (PIT) of each customer and the restoration duration of customers located upstream and downstream of the faulted section. AFLPT is used as an economic index along with collective reliability indices to select a better tradeoff between benefit and investment cost during the allocation of automated sectionalizing switches. Results show that the correlation between PIT and restoration duration allows electric utilities to identify geographic areas where economic investment in modern technologies, as self-healing, can be prioritized.

Voltage regulators, capacitor banks and distributed resources allocation in a distribution network system

This paper introduces a methodology to propose operational planning actions within a short-time horizon in distribution systems. This methodology considers real-load curves of distribution transformers and distributed-resources composed by photovoltaic and storage systems. Voltage regulators, capacitor banks and distributed-resources are installed in strategic places in order to maintain voltage in each bus and loading in each line within proper ranges. This methodology was applied in a real distribution network. The results show a reduction in maximum demand when considering distributed resources and, also a decrement of their impacts on voltage, current and losses for the entire distribution system.

Case studies of application of process immunity time in assessment of Financial Losses due to system faults induced industrial Process Interruptions

In this paper, the assessment of Financial Losses related to Process Trip (FLPT) due to voltage sags and Long Duration Interruptions (LDI) for the whole distribution network is carried out for different operating conditions in order to highlight the importance of probabilistic assessment of FLPT and in particular of inclusion of Process Immunity Time (PIT) in the evaluation. The FLPT due to voltage sags and LDIs are evaluated and compared. A geographic area of the network is clearly identified where high annual FLPT can be expected. It is demonstrated that this area is reduced when PIT is considered. The proposed methodology can be used by utilities to prioritize corrective measures to be taken in different parts of the network to improve quality of electricity supply to affected customers and by end users to assess and reduce their financial losses.