Donald McGillis

Operation of Impedance Protection Relays with the STATCOm

This paper presents analytical and simulation results for investigating the operation of impedance-based protection relays in a power system containing a flexible alternating current transmission (FACTS) controller such as static synchronous compensator (STATCOM). The analyses are based on steady state operation for modeling the STATCOM and the protection relays. The impact of the FACTS device on protection relays is studied for normal operating conditions as well as for fault conditions under different loading levels. Results for a case study are given.

The Process of System Collapse Based on Areas of Vulnerability

The purpose of this paper is to introduce a new approach to the process of system collapse based on areas of vulnerability. For this purpose, a new category of contingencies called abnormal contingencies and a new system operating state called verge-of-collapse are proposed. The application of these abnormal contingencies to the vulnerable areas can lead to a system on the verge-of-collapse. In particular, there are two conditions that generally occur for a system to be on the verge-of-collapse: firstly, the system is in a degraded state or close to its operation limits and secondly it must be subjected to abnormal contingencies in the areas of vulnerability. The result of this study is to define areas of vulnerability in a network which can then be identified and appropriate remedial action initiated when required. Different stages are required for the protection of systems on the verge of collapse, namely: a) how to define areas of vulnerability, b) how to identify these areas of vulnerability and c) how to protect the system in the presence of areas of vulnerability. This paper is the first stage in proposing a new approach to the protection of systems on the verge of collapse

Power system reliability in a deregulated environment

At the present time, the deterministic approach to transmission reliability has not been able to incorporate the effect of simultaneous power transactions on system adequacy or the effect of system security on the feasibility of power transactions. In this paper, a probabilistic approach to analyze the security of power transactions under random trading has been developed based on a region-wise approach to security analysis. In particular, the feasibility and security regions in the transaction space are derived from a transaction matrix model. By classifying each feasible transaction matrix as either secure or insecure based on prescribed system security criteria, a set of transaction-based security indices are defined. The concepts developed in this paper indicate that while the security of the transmission system is a given, the adequacy is compromised when a large number of bilateral contracts are involved.

Comprehensive transmission distance protection settings using an intelligent-based analysis of events and consequences

This paper introduces a new methodology for settings of transmission system distance protection based on an intelligent analysis of events and their consequences. The output of the proposed methodology is comprehensive distance relay settings which include not only the zone reaches and zone time delays, as in the existing approaches, but also the optimal impedance operating characteristics, the fault detection settings, and the required relay sensitivities in terms of voltage and current. The need for this methodology is the result of the increased complexity of interconnected power systems protected with a large number of relays with different relay technologies, such as electromechanical, static, and numerical as well as diversity in their operating algorithms. The relay settings are automatically updated after every major change in the state of the network topology. Since it is not possible to include all design details of the proposed system, sample design events and rules are given to illustrate the proposed methodology.

FACTS controllers and the deregulated electric utility environment

The push towards deregulation in the electric utility industry is forcing a revaluation of the way transmission systems are operated. Reliance on the natural flow of current cannot meet the new requirements imposed by deregulation. One method to dictate the power flows is the increased reliance of Flexible AC Transmission Systems (FACTS). This paper presents some of the new directions being investigated to adapt and exploit the potential of power electronic converters to increase the flexibility and reliability of modern power systems.

Severity Index for Estimating the Impact of Wind Generation on System Vulnerability

This paper proposes a severity index for estimating the impact of penetration of wind energy on the vulnerability of a power system. This index is the risk of not meeting the load and is in fact the risk of failure of the probability distributions of the system load and the system generation including the wind penetration. This probabilistic approach is appropriate for a system with large wind generation installation due to the random nature of the wind generation output. The severity index is proposed to recognize the possible existence of an area of vulnerability at the point of common coupling (PCC). This approach does not preclude applying this methodology to a specific PCC bus in order to verify the impact on the security at each PCC bus in the planning stage and to alert the system operator of any possible shortfall of generation. A case study is provided to demonstrate the proposed approach.

The performance specification of transmission line protection using a knowledge-based approach

This paper introduces an automated approach to transmission line protection design for implementation in the form of a performance specification. The need for automation is the result of the increased complexity of interconnected power systems and despite numerous proprietary computer programs, the analysis of power system behavior requires significant engineering time and effort. Many scenarios have to be investigated before selecting and setting a protective relay and its equipment. By automating the running of the various computer programs and analyzing the results in a specific manner, the design scenarios can be investigated relatively quickly, cover all possible cases, remove protection design redundancy, preserve protection design methods, and assure consistency in protection system design. Additionally, by changing the system loading to some future anticipated value, it can be determined if specified relays and their equipment can be adjusted or will have to be replaced. It is also clear that such a design tool is useful in training system protection design engineers.

A knowledge-based system for the structural design of high-voltage lines

The basic structure of the knowledge-based system consists of a database of tower configurations and associated parameters, a knowledge base of design rules and a program to fire the rules so as to produce one or several designs based on the specified design criteria. An examination of existing software on tower design was carried out but it was found that these programs were too detailed and too specific to be of use for the preliminary design of a number of alternatives. The input to this expert system consists of the voltage level and the physical environment. Selection of the conductor assembly is probably the most important aspect of transmission line design. For EHV lines the minimum conductor is determined from corona considerations, namely the audible noise (AN) and radio interference (RI) standards. Larger conductors can be evaluated based on the increased cost of the lines and the reduced cost of the losses for a given power transfer. The methodology itself consists, first of all, in obtaining the knowledge associated with the structural design of towers from recognized experts. The second step consists in formalizing this knowledge as a series of heuristic rules. It also includes the development of a hierarchy of objects to represent the design parameters. The third step involves integrating the rules and objects in the form of software and making sure this software is functional. The output of this knowledge-based system is the cost per kilometer of high-voltage transmission lines as a function of any combination of the specified design parameters. This output is vital to the planning of HV transmission systems.

Areas of Vulnerability in an Environment of Uncertainty

This paper addresses the vulnerability of power system operating in an environment of increasing uncertainty. Uncertainty can be related to the performance of a system under stress and the measures whereby this condition of possible system collapse could be identified and averted through remedial actions. For this reason, the paper begins with a definition of a vulnerable system as one that is in a degraded state and is then subjected to moderate disturbances that can lead to system collapse. When uncertain generation such as wind generation or deregulation is then introduced, these moderate disturbances can be regarded as variations in the wind generation or the system topology.

The effect of capacity gaming on the cost of system reliability

The effect of capacity gaming on the cost of system reliability is investigated. For this purpose, the concept of an adjusted forced outage rate for de-ratings to represent capacity gaming is introduced. Through this new concept, the increased cost of supplying load and of spinning reserve due to capacity gaming can be estimated. In addition, the lost opportunities to those who are gaming will become evident. A simple but compelling example of a three-generator system demonstrates clearly these effects. In a sense, gaming is more a moral problem than a technical one since the net benefit to the consumer or producer from this exercise is questionable.