Test Systems for Reliability and Adequacy Assessment of Electric

Power Systems

Roy Billinton, Dange Huang University of Saskatchewan

Canada

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Introduction

The RBTS is a 6 bus system composed of two generator buses, 5 load buses, 9 transmission lines and 11 generating units. The total installed capacity is 240 MW and the system peak load is 185 MW.

The RBTS was developed for educational and research purposes.

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Introduction The IEEE-RTS is a 24 bus system with 10 generator buses, 17 load buses, 33 transmission lines, 5 transformers and 32 generating units. The total installed capacity is 3405 MW and the system peak load is 2850 MW. The IEEE-RTS was developed by a Task Force of the Application of Probability Methods Subcommittee of the IEEE Power System Engineering Committee. It was developed to satisfy the need for a standard database to test and compare results from different power system reliability evaluation methodologies.%%

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The basic RBTS and the IEEE-RTS use a common load model in which the load at each hour of the year is expressed as a percentage of the assigned system peak. The structure permits the load to be represented by a chronological hourly load model or by aggregated annual or period load models.

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Introduction

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Hierarchical levels

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RBTS Data

•  Generation Data

Basic HL-I model

RBTS Data

•  The data in this table is extended in [11] to include derated state models for the 40 MW thermal generating units.

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RBTS-Generation DataReference 11 includes the relevant cost data on each generating unit including fuel costs, operating costs and capital costs. Two loading orders are provided. The first loading order is on a purely economic basis, in which the hydro units are loaded before the thermal units, due to their low operating costs. The second loading order allocates some hydro units as peaking capacity, which could reflect limited energy considerations.

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Additional generating capacity to meet future load growth is assumed to consist of 10 MW gas turbines with the reliability and cost data shown in [11]. A suggested seven step approximation to a normal distribution with a standard deviation of 4% is given to include load forecast uncertainty. Maximum and minimum generating unit MVAr capability data are provided for load flow purposes in subsequent composite system studies.

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RBTS-Generation Data

The relevant reliability data for the nine 230 kV lines in Fig. 1 in terms of the permanent and transient failure rates and the permanent outage repair times are given in [11]. The outage duration of a transient outage is considered to be less than one minute. Outages of substation components which are not switched as a part of a line are not included in the line data.

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RBTS-Transmission Data

RBTS-Transmission DataThe basic transmission outage data for the system in Fig. 1 is augmented in [11] by providing the necessary impedance, susceptance and current rating data to conduct AC load flow studies. Load bus data is provided in the form of peak load MW and MVAr values. Reference 11 suggests that the load at each bus should be classified in the two categories of firm load and curtailable load and that in the case of a relevant system problem, curtailable load should be curtailed first followed by curtailment of firm load if necessary.

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Single line diagram of the RBTS

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Extended single line diagram of the RBTS

RBTS-Distribution Data

+'"Bus 2 distribution systems of the RBTS

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RBTS-Distribution Data

Bus 6 distribution systems of the RBTS

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Complete single line diagram of the RBTS

IEEE-RTS Data

The basic objective of the Reliability Test System Task Force that developed the IEEE-RTS was “to establish a core system which can be supplemented by individual authors with additional or modified parameters needed in a particular application”.

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IEEE-RTS Data

This has certainly proved to be the case as the IEEE-RTS has been used in a wide range of studies, which in many cases involved additional or modified parameters. The original system provides a load model, a generation system and a transmission network. It does not include substation configurations, distribution systems, interconnections with other systems, protective relay configurations or future expansion considerations.

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IEEE-RTS Data

The generation facilities include steam capacity in the form of fossil-oil, fossil-coal and nuclear units, combustion turbine units and hydro units. Operating cost data is provided for each unit type, and data on hydro unit capacity and energy limitations are specified. The generating unit MVAr capabilities are provided in [12] for each unit size. Voltage correction devices with specified capability are provided at bus 14 (synchronous condenser) and bus 6 (reactor). Individual bus peak load power data are provided and a 98% power factor is assumed.

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IEEE-RTS Data

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The Generating Unit Reliability Data for the IEEE-RTS

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IEEE-RTS DataThe Generating Unit Reliability Data for

the IEEE-RTS

IEEE-RTS Data

As noted in Fig. 2, the connections from bus 1 to 2 and from bus 6 to 10 are 138 kV cables. Transmission line forced outage data are provided for each line and cable in terms of permanent outage rates and repair times and transient outage rates. The permanent outage rate includes a fixed component to account for faults on terminal equipment switched with the line. Data is presented on bus section and circuit breaker reliability but the report, by intent, does not include any substation configurations.

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Reference [12] also indicates that seven line pairs are on either a common right-of-way or a common tower structure for all or part of their length, but does not provide any reliability data. Impedance and rating data is provided for each line, cable and transformer. The point is made that the data in this paper is sufficient to completely define a DC load flow for the test system but is not completely defined to conduct an AC load flow as generator bus voltages and transformer tap information are required.

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IEEE-RTS Data

•  A modified version of the IEEE-RTS (RTS-79) was published in 1986 and designated as RTS-86 [16]. This paper removes some of the limitations which existed in the RTS-79 by including additional data pertaining to the generating system. In addition, RTS-86 contains a set of basic generation indices for the base and extended RTS. The indices were evaluated without any approximations in the evaluation process and therefore provide a set of exact indices against which the results of alternate and approximate methods can be compared.

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IEEE-RTS Data

The additions to RTS-79 contained in RTS-86 include generating unit derated states, load forecast uncertainty, unit scheduled maintenance conditions and the effect of interconnections. The data used to incorporate these conditions together with study results that indicate their effects on the HL-I reliability indices are presented in [16].

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IEEE-RTS Data

The IEEE-RTS was further extended in 1996 by the Reliability Test System Task Force of the Application of Probability Methods Subcommittee to produce RTS-96. Changes occurring in the electric utility industry motivated the Task Force to create a multi-area RTS incorporating additional data [17]. In addition to the basic RTS-79 configuration, the Task Force created a Two Area RTS-96 and a Three Area RTS-96 by linking various RTS-79 single systems.

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IEEE-RTS Data

A major addition in this revision is the inclusion of production cost related data for the generating units. Data on unit start-up heat input, net plant incremental heat rates, unit cycling restrictions and unit emission data were added to facilitate system production cost calculation and emission analysis.

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IEEE-RTS Data

The RTS-79 transmission system was enhanced by including a phase shifter, a two terminal DC transmission line and five inter-area ties. The transmission branch data for each area is described in tabular form. A DC interconnection between Area A and B is proposed based on a procedure and data presented in [18]. Figure 8 shows a single line diagram of the One Area RTS-96 including substations. The relevant circuit breaker failure data are given in [17]. Figure 8 was originally published in [19].

IEEE-RTS Data

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$$"Single line diagram of the IEEE One Area RTS-96

with substations

The RTS-96 also includes system dynamic data based on a classical generator model. Typical reactance and intertia data based on generators of the same type and size are provided. The IEEE-RTS published in 1979 has been extended by the addition of a wide range of enhancements. The 1996 Task Force noted that these enhancements should be considered as optional additions and no user should feel compelled to make use of them all.

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IEEE-RTS Data

The published literature contains numerous papers in which the IEEE-RTS is used as the studied system. In many cases, the IEEE-RTS was modified to meet the study requirements. The IEEE-RTS is basically a generation weak and transmission strong system. One of the more common modifications is to increase the generating capacity and the system load while retaining the original transmission system.

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IEEE-RTS Data

The IEEE-RTS in the form of the RTS-79, RTS-86 and RTS-96 does not include customer interruption cost data. Reference [20] contains customer interruption cost data on seven customer sectors and the sector load allocations at each load point in the IEEE-RTS. These data are then used to create composite customer damage functions and interrupted energy assessment rates at each load point.

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IEEE-RTS Data

This paper presents a general overview of the RBTS and the IEEE-RTS, and a brief summary of the evolution of these test systems. The paper does not attempt to provide a compilation of the test systems data contained in the references. As noted in the paper, the IEEE Reliability Test System Task Force was motivated to expand and enhance the IEEE-RTS in 1996 by the changes that had occurred in the electric utility industry. Considerable changes have occurred since 1996, which suggests that both the RBTS and the IEEE-RTS should be studied and enhanced to include data that would allow these changes to be incorporated and applied in basic electric power system reliability assessment.

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Conclusion