Models and Solution
Updated 04/01/2014: Model solutions were compared between WindMil and CYME, requiring updates to the models and assumptions. The updated model information and results can be found at:
Updated 04/01/2014: In case questions arise for comparison, the original models and solutions are also available:
Description of The Comprehensive Distribution Test Feeder
W. H. Kersting, Life Fellow, IEEE
W. H. Kersting is a consultant to Milsoft Utility Solutions and a partner in WH Power Consultants, Las Cruces, NM.
Abstract – In 1991 a paper giving the data for four distribution system test feeders was published . The purpose of the test feeders was to give software developers a common set of data that could be used to verify the correctness of their programs. Since then the original four test feeders along with additional special purpose test feeders have been made available on the IEEE website . The purpose of this paper is to present a “comprehensive” test feeder that will allow for the models of all the standard components of a distribution system to be tested. Only the system will be described in this paper. The total data will be found on the IEEE website .
Index Terms-Test feeders, distribution lines, regulators, transformers, capacitors, loads, component models
Each of the original test feeders had special characteristics that provided a test for the accuracy of the distribution component models and the convergence characteristics of the program being tested. The original four test feeders are:
- 13 Node Test Feeder – provided a good test of the convergence of a program for a very unbalanced system
- 34 Node Test Feeder – a very long feeder requiring the application of voltage regulators to satisfy ANSI voltage standards
- 37 Node Test Feeder – a three wire delta underground system
- 123 Node Test Feeder – a large system consisting of overhead and underground single phase, two phase and three phase laterals along with step voltage regulators and shunt capacitors
Additional test feeders have been added for the special purpose of testing transformer connection models and induction machine models.
II. COMPREHENSIVE FEEDER
Figure 1 displays the one-line diagram for the comprehensive feeder. It should be noted that this drawing is not to scale. All nodes, transformers, regulators switches and capacitors have been numbered.
Examples of Overhead Lines
The spacings of the conductors on the poles are defined in the data on the website.
A special case for the overhead lines is to model two lines in parallel. In Figure 1 the parallel overhead lines go from node 713 to nodes 717 and 704. The mutual coupling between the two lines must be modeled. This is a case of two lines physically in parallel but not electrically parallel.
Transformer T2 at node 719 is a single-phase centered tapped transformer serving a secondary system composed of a triplex cable. Each of the load points consists of two 120 volt loads and a 240 volt load.
Transformer T4 is an ungrounded wye-delta bank serving a three-phase secondary system consisting of a quadraplex cable. Two load points serve the 120 and 240 volt single phase loads. The third load point serves a three-phase induction motor.
Examples of Underground Cables
A special case for the underground lines is to model two lines in parallel. In Figure 1 there are two concentric1/3 neutral cables in parallel between nodes 702 and 703 and 713. For this case there is a three phase switch that connects node 703 to 713. With the switch open the lines are physically in parallel and with the switch closed the two lines are electrically in parallel. Since the cable sizes are different for the two lines, there is a difference between the results for physically parallel and electrically parallel.
Center Tapped Transformers
Step Voltage Regulators
There are five step voltage regulators in the system. The regulators utilize different connections. For all regulators the primary CT rating and PT ratios are defined as well as the compensator R and X settings and the desired voltage level. The five regulators are:
Initially SW-1 is closed with the other two switches open. Closing SW-2 will be a test on program convergence for a loop. With SW-1 open and SW-2 closed a new configuration is established. The purpose of SW-3 is to model the two underground three-phase lines as either physically parallel or electrically parallel. With SW-3 open the physically parallel is modeled while with SW-3 closed the electrically parallel case is modeled.
Examples of Distributed Loads
Examples of Spot Loads
Switched Capacitor Banks
There are four three-phase switched shunt capacitor banks in the system.
Center Tapped Loads
The loads on the centered tapped transformers will be modeled the same as spot loads. For single phase centered tapped transformers there will be two 120 volt loads and one 240 volt load. For three-phase banks the center tapped transformer will have the two 120 volt loads, one 240 volt load and a three-phase load. Some of the three phase loads are static loads and others will be induction machines.
The substation transformer is three phase connected delta-grounded wye. The impedance is specified. The station voltage is regulated by Regulator – 1.
Equivalent Source System
The equivalent source system is specified by the nominal voltage of 115 kV. For short circuit studies the three phase and single phase short circuit studies the equivalent system positive and zero sequence impedances are given.
The comprehensive IEEE test feeder has been developed in order to test the models of all distribution components and to test the convergence qualities of a verity of switching schemes. In this paper only the one-line diagram and a description of the various components has been presented. The actual data for the feeder can be found in . Preliminary results for the power flow analysis will appear also in . It is hoped that more developers will use this test feeder to test all aspects of their software. In time additional components such as photovoltaic arrays will be added.
- IEEE Distribution Planning Working Group Report, “Radial distribution test feeders”, IEEE Transactions on Power Systems,. August 1991, Volume 6, Number 3, pp 975-985.