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Hardware Design and Layout of a R econfigurable Power D istribution A utomation


Hardware Design and Layout of a R</i>econfigurable Power D</i>istribution A</i>utomation
and C</i>ontrol L</i>aboratory (RDAC)


Karen Miu, Chika Nwankpa, Xiaoguang Yang and Anthony Madonna

Department of Electrical and Computer Engineering
Drexel University
Philadelphia, Pennsylvania





Abstract: This paper will present the hardware design and detailed physical layout of a scaled
power distribution system laboratory under construction at Drexel University. Engineers with
formal knowledge about power distribution systems are needed to design, upgrade and operate
large-scale distribution power systems and their automation and control techniques. In response,
at Drexel, we are developing a power distribution systems curriculum centered around a
r</i>econfigurable d</i>istribution a</i>utomation and c</i>ontrol laboratory, RDAC. This paper focuses on the
physical layout and presentation of large-scale distribution power systems.


I.

INTRODUCTION

A renewed focus on maintaining and improving reliability and power quality has highlighted the
need for increased monitoring and control of power distribution systems both in the utility and
within industrial plants and buildings. Brought on by utility restructuring efforts and the
continued thrust towards deployment and use of automated devices, industries, such as power
distribution companies, automotive companies, architectural engineering firms, ship builders,
pharmaceuticals, etc., are increasingly concerned with their energy systems and hire engineers for
the planning and operation of lower power, lower voltage (<115kV) distribution systems.

As such, the topic of power distribution systems has been addressed at several universities in
terms of classes and software laboratories, with a smaller number of universities addressing
hardware laboratories. Some existing laboratories are now discussed. Software laboratories
explicitly for distribution system planning can be found in [1]. At the University of Florida, a
hardware laboratory was established for power quality and energy studies [2]. In Taiwan, a
distribution automation laboratory was created for wider types of studies [3]. More recently, at
Milwaukee School of Engineering, [4] documents the development of a building electrical power
systems design specialty where a link between architectural engineering and industrial plant
management is created with power distribution system studies.

At Drexel, an interconnected power system laboratory (IPSL), focusing on generation and
transmission studies, has been incorporated into the existing ECE curriculum [5][6] and
disseminated and reproduced at the University of Hong Kong. IPSL has successfully combined
four existing generation and transmission system laboratories into an interconnected three-bus
power system with real-time data acquisition. It is envisioned that the power distribution system
focus of RDAC will complement the generation and transmission oriented laboratories already

available. RDAC will provide students with hands-on learning experiences in the analysis,
operation and planning of electric power distribution systems.

A comprehensive curriculum is targeted to expose all electrical and computer engineering
students to power distribution systems through RDAC laboratory modules and to provide more
formal education to upper-level electrical engineering students through full courses and
laboratories. RDAC is designed to be reconfigurable both in its physical construction and
electrically, through computer and manually controlled devices. With embedded network
switches allowing for reconfiguration of electrical connections, RDAC can address second-year
level material such the differences between parallel and series connections of impedances and
other basic circuit theory concepts in the context of power distribution networks. At a more
advanced level, the flexibility of the distribution network will allow students to perform
experiments in three-phase power flow analysis, network reconfiguration of load balancing,
service restoration after faults and capacitor placement for voltage regulations. At a senior
design/capstone and graduate level, students may design and test their own control schemes and
measure the effects different distribution automation and control schemes have on the system.

RDAC consists of four modular stations that can combine for a total of 36 buses, 16 lines, 16
normally closed switches and a number of possible load connections. A supervisory control and
data acquisition (SCADA) system has also been designed with facilities such as signal
conditioning hardware, data acquisition equipment, and remote terminal units (RTUs). The
SCADA system will allow students to view network voltages, currents, and power flow in a user
friendly and realistic manner. Procedures and results of detailed hardware equipment tests
performed on components listed and depicted in this paper were presented in [7]. In this paper,
special attention to the layouts of the hardware components and the entire laboratory has been
made to facilitate the presentation of large numbers of interconnected components. In addition,
the modular construction and the physical layout are designed to accommodate several groups of
students and several interchangeable experiments

This paper presents the electrical and physical layout of a three-phase, 36 bus, reconfigurable,
power distribution system. The distribution system will be typically operated in an electrically
radial manner with 4 identical student laboratory stations focusing on 8 buses each. Within each
laboratory station four main parts exist: (i) the power station, (ii) the distribution feeder box, (iii)
the transfer station and (iv) a PC for data acquisition and computer control. The paper progresses
by introducing the entire power distribution laboratory layout and then focuses on individual
stations used to supply power, deliver power and transfer power.


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Figure 1. One-line diagram of the 7 kW three-phase RDAC laboratory in a typical setup

II.

LABORATORY OVERVIEW AND LAYOUT

A general laboratory electrical configuration and physical layout are now discussed. The electric
infrastructure of RDAC will be multi-phased and normally operated in a radial manner. It can be
reconfigured conveniently for different experiments. A one-line diagram of a general
configuration of RDAC is shown in Figure 1. Please note, in this layout, four identical feeders
each with one branching lateral can be identified.

The system will normally be operated at a frequency of 60Hz and a voltage level of 120V phase
to neutral. However, it can also be reconfigured to operate as a DC system. RDAC consists of the
following, where detailed descriptions of components can be found in [12]:
An AC source providing power for typical loading conditions, up to 7kW with four feeders
connected;
A DC source (achieved by using an industrial three-phase rectifier)
4 1:1 variable three-phase auto transformers;
4 three-phase over-current circuit breakers with maximum current of 30A, which
correspond to the protection devices in Figure 1;
4 feeders with one lateral on each feeder: for a total of 16 three-phase lines represented by
48 inductors each with a 20A current rating;
48 normally opened and 48 normally closed digital relays are used to model 16 three-phase
sectionalizing switches and 16 three-phase tie switches. Each relay can be controlled
individually;

ZIP loads with various compositions, including individual constant impedance, constant
current, and constant power loads. They can be connected in both balanced and/or
unbalanced fashions.
Hall-effect devices, for AC and DC measurements, at eac