Western System Coordinating Council Research Articles

Regional model assesses economy energy purchases

A description is given of a program that models the loads, resources, interconnected transmission systems, and firm power commitments of each major region served by the Western Systems Coordinating Council (WSCC) interconnected network. The program is used to determine the quantity and price of economy energy ultimately available to Californian utilities. The model determines the amount of economy energy that will be purchased by individual California utilities by using economy energy demand curves for each purchasing utility. Following a discussion of the origins and development of the model, the information required by the model and the results the model generates are explained. A simple flow diagram shows the general structure of the model in sufficient detail to explain how it works, without dwelling on its intricacies. An example of the program's application in a transmission line certification proceeding is presented. A specification of the hardware necessary to run the program and discussion of ongoing enhancements are included.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Inter-utility communications within WSCC

The development of real-time interutility data communications capabilities has resulted in many implementations in the western United States. The current state of these implementations and the future plans for additional capabilities spanning the entire Western Systems Coordinating Council (WSCC) are presented. In 1982, the WSCC formed a group to develop a protocol and a set of guidelines for real-time interutility data exchange. All the major utilities within the WSCC now have or are planning implementations based on the guidelines. Other implementations outside the WSCC are discussed. The impetus for this move is economic benefits realized by reduced hardware installation, better power system modeling that allows optimal use of existing resources, visibility outside a utility's control area, better restoration coordination, and the ability to quickly match power system resources to markets at mutually beneficial prices.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Modified automatic time error control and inadvertent interchange reduction for the WSCC interconnected power systems

An automatic generation control (AGC) system is described that simultaneously reduces time error and accumulated inadvertent interchange energy in interconnected power systems. The Western Systems Coordinating Council (WSCC) adopted this control method in January, 1989 based on the results of the simulation studies described. Also described are accumulated inadvertent interchange reduction (AIIR) control characteristics and experience in the WSCC interconnected systems. >

Eigenvalue and frequency-domain analysis of the intermountain power project and the WSCC network

The Western Systems Coordinating Council (WSCC) has several interarea modes of oscillation in the range of 0.3 to 0.8 Hz. The results of an investigation of how various network parameters and operating conditions affect the stability of those modes are presented. Eigenvalue and frequency-domain techniques are used. The study results show that numerous system parameters can have a significant impact on overall network stability. These parameters can include control settings, such as those in HVDC systems or power system stabilizers, or operational parameters, such as scheduled tie-line flows. The results show that careful analysis and tuning of all significant controls in a large network are necessary to ensure overall system stability and satisfactory performance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Operating problems with parallel flows

This paper is one of a series presented on behalf of the System Operations Subcommittee with the intent of focusing industry attention on current problems faced by electric utilities in the operation of the bulk power system. The paper is a compilation of short notes that describe the ramifications of loop flows on the power systems of the Penn- sylvania - New Jersey - Maryland Interconnec- tion, American Electric Power System, and the members of the Western Systems Coordinating Council. The operating problems caused by large loop flows are fairly well understood. The purpose of these short notes is to highlight the complexity of the problem and underscore the need for a full comprehension of the problem within the engineering community.

Contingency arming system implementation for the Intermountain Power Project HVDC transmission system

Implementation of an automated contingency arming system (CAS) to trip Intermountain Power Project generators based on network transfer level and transmission failure mode in coordination with AC/DC controls provides network stability to the Western Systems Coordinating Council system and achieves an increased Intermountain DC transfer level. The authors present the concept of the Intermountain CAS and its enhancement to system performance. Planning issues associated with the design and implementation of the CAS are discussed, and the validation of transfer level is demonstrated by transient stability study results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Contingency Arming System Implementation for the Intermountain Power Project HVDC Transmission System

Implementation of an automated contingency arming system (CAS) to trip Intermountain Power Project generators based on network transfer level and transmission failure mode in coordination with AC/DC controls provides network stability to the Western Systems Coordinating Council system and achieves an increased Intermountain DC transfer level. The authors present the concept of the Intermountain CAS and its enhancement to system performance. Planning issues associated with the design and implementation of the CAS are discussed, and the validation of transfer level is demonstrated by transient stability study results. >

The Intermountain Power Project 1600 MW HVDC transmission system

The 1660 MW HVDC transmission system of the Intermountain Power Project (IPP) is designed to deliver energy from a coal-fired, two-unit generating plant in Delta, Utah, to load centers in southern California, USA. To minimize disturbance to the adjacent AC network and the relatively isolated generating plant, several special control features as well as high short-time and steady-state overload capability are required in the design of the IPP HVDC converter stations. The power system reliability requirements of the Western Systems Coordinating Council (WSCC) on the DC transmission system resulted in the specification of guaranteed reliability and availability requirements. The main features in the design of the main circuit equipment, HVDC controls, and the reliability and availability consideration of the IPP transmission system are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Planning Considerations for the Intermountain HVDC Transmission System

Planning of an HVDC transmission system embedded into an existing ac network may require unique control and converter equipment capability in order to satisfy stability requirements of the network. The planning and design of the Intermountain Power Project HVDC transmission system are based on unique control performance features for power transfers during terminal ac faults, rapid power recovery following fault clearing and utilization of exceptionally high transient overload capability of 2 per unit during the post-fault period to maintain system stability. The Department, in its efforts to meet the Western Systems Coordinating Council's (WSCC) reliability criteria, developed and incorporated into its HVDC specifications very rigorous reliability and availability requirements. One objective of this project was to attain the unusually low bipolar converter system outage frequency goal of one outage in five years to achieve a bipole performance rating equivalent to two ac circuits of similar capability. The reliability goals of this project have provided one of the impetus for revisions to the WSCC Reliability Criteria for System Design. The reliability goals and other features adopted for the Intermountain HVDC transmission system are discussed in this paper and study results are included to demonstrate the effectiveness of various controls implemented as stability enhancement techniques.