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Y R K E S H Ö G S K O L A N

SERIES R: REPORTS 6/2014

SCADA SYSTEM FOROFF-GRID ENERGYSOLUTIONS ON REMOTEISLANDS

Mathias Bjork & Johan Westo

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Abstract

Remote off-grid energy solutions in the archipelago need to be monitored and controlledfrom the mainland. This report proposes a solution for how such a supervisory control anddata acquisition system could be set up. The proposed solution relies on local systems thatcan work independently to control the power production on site but that at the same timecan be supervised remotely. This is accomplished by letting local systems connect to theInternet using a 3G connection. For this purpose, access to a 3G network has also beenverified at one possible location in the archipelago (Mickelsorarna).

Sammanfattning

Avlagsna off-grid energilosningar ute i skargarden maste kunna overvakas och sty-ras fran fastlandet. Denna rapport presenterar en tankbar losning for hur ett styr- ochovervakningssystem kunde implementeras. Den tankta losningen omfattar lokala systemute i skargarden som ar tillrackligt avancerade for att hantera energiproduktionen lokaltmen som pa samma gang aven kan overvakas och styras pa distans. Denna kombinationmojliggors genom att lata de lokala systemen ansluta till Internet genom en 3G anslutning.For andamalet sa har aven mojligheten att ansluta till ett 3G natverk ute i skargardenverifierats vid ett tankbart lage (Mickelsorarna).

Publisher: Novia University of Applied Sciences, Wolffskavagen 35 B, 65200 Vasa, Finlandc© Mathias Bjork, Johan Westo & Novia University of Applied Sciences

Novia Publications and Productions, series R: Reports 6/2014ISSN: 1799-4179,ISBN: 978-952-5839-91-3 (online)Layout: Johan Westo

Contents

1 Introduction 1

2 Background 12.1 Supervisory control and data acquisition . . . . . . . . . . . . . . . . . . . . 12.2 Internet connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.3 Dynamic Domain Name System . . . . . . . . . . . . . . . . . . . . . . . . . 2

3 System specification 3

4 Network accessibility tests 3

5 Proposed solution 55.1 Local systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55.2 The central system and its HMI . . . . . . . . . . . . . . . . . . . . . . . . . 65.3 Products and costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

6 Summary 7

References 7

Appendices 8A I/O list for local system PLCs . . . . . . . . . . . . . . . . . . . . . . . . . . 8

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1 Introduction

Supervisory control and data acquisitionsystems are vital for ensuring proper op-

eration of machines and processes at remotelocations, and these systems are commonlyused for monitoring and controlling the elec-trical grid at a nation wide scale. In a similarfashion, this type of systems could also beused for ensuring proper operation of smallscale off-grid energy solutions at remote is-lands in the archipelago.

Several island groups in the Kvarkenarchipelago hold nature stations, cafes, andaccommodation. These kind of buildings areall in need of off-grid energy solutions tomaintain operations, and it would be veryuseful to have a system that would makeremote monitoring and control possible.

This report focuses on different aspects ofremote monitoring and control, and presentsa proposal for how a supervisory controland data acquisition systems could be imple-mented for an off-grid energy solution on aremote island, Mickelsorarna, in the Kvarkenarchipelago. Furthermore, the proposed so-lution is structured in such a way that it canbe easily extended to also cover more islandgroups in the future. This is accomplishedby keeping the system’s central parts on themainland and letting local systems, local-ized on islands in the archipelago, connectto the central system using a 3G internetconnection.

The work was conducted within theproject Pisara meressa (English transla-tion: A drop in the sea). This was a 3 yearproject set out to investigate and developsmall-scale decentralized solutions for inte-grating automated renewable energy sourcesin a sustainable manner. The investigationwas divided into different areas regardingproduction, distribution, and usage of therenewable energy sources, including the prof-itability aspect of the implemented solutions.Funding was received from the Centre forEconomic Development, Transport, and theEnvironment, and the European AgriculturalFund for Rural Development. The projectwas run by the Vaasa Energy Institute (VEI)

and the University of Jyvaskyla in cooper-ation with the Metsahallitus unit in Vasa.VEI is a cooperative organisation founded bythe University of Vaasa, the Levon Institute,Novia University of Applied Sciences, andVaasa University of Applied Sciences, witha long term goal to increase local know-howwithin energy related fields (Vaasa EnergyInstitute, n.d.; Levon-instituutti, 2012).

2 Background

2.1 Supervisory control and dataacquisition

Supervisory control and data acquisition(SCADA) systems are used to monitor andcontrol processes in real time, and to storehistorical data. These systems can vary insize from a tank level process in industry toa nation wide electric grid (Cegrell & Sand-berg, 1994). Historically, SCADA systemshave been developed for specific applications,such as the electrical grid or large processplants, where the need for real time controland monitoring have motivated the requiredinvestment. These kind of systems are oftenvery expensive, but cheaper SCADA-like1

alternatives have emerged for building au-tomation applications.

SCADA systems usually consists of thefollowing parts (Cegrell & Sandberg, 1994):

1. sensors and actuators,

2. local systems,

3. a communication infrastructure,

4. central systems, and

5. a Human-Machine Interface (HMI).

Sensors and actuators are connected to lo-cal systems, such as Remote Terminal Units(RTUs) or Programmable Logic Controllers(PLCs). These gather data locally, and they

1SCADA-like is here referring to systems thatshare the supervisory control and data acquisitionstructure, but possibly lack the strict real time re-quirements found in traditional SCADA systems.

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can also run simpler local control algorithms.Central systems, such as system servers, col-lect data from all local systems and can alsosend instructions or control commands tothese. The communication infrastructuretherefore have to secure a communicationchannel that allows local and central sys-tems to exchange information continuously.Finally, the HMI allows humans access thecentral systems by visualizing collected data,presenting current process states in real time,and by letting the user set control parame-ters.

A SCADA system designed for monitor-ing and controlling energy solutions on re-mote islands could therefore utilize the fol-lowing design:

1. sensors and actuators,

2. one or more local PLCs at each islandgroup,

3. 3G routers connecting local systemsto the Internet,

4. a central system server located onthe mainland or in the cloud, and

5. an HMI that can be accessed re-motely through a web browser orthrough a remote desktop connec-tion.

Several PLC providers, or providers ofsimilar products, also provide a SCADA solu-tion for their products that include softwarefor the central systems as well as softwarefor creating a HMI. This software is nor-mally licensed and can be quite expensive. Acheaper solution would be to use free on-lineservices for similar tasks, but our experi-ence indicate that these do not constitute acomplete product, and that interoperabilityissues are a big problem that can make thesolution very expensive in the end.

2.2 Internet connectivity

The Finnish telecommunications companiesElisa Oyj, DNA Oy, and TeliaSonera Fin-

land Oyj all provide coverage for 3G2 net-works in parts of the Kvarken archipelago.However, based upon coverage maps fromdifferent telecommunication companies (seeElisa, DNA, and Sonera), the coverage onMickelsorarna is questionable. Despite this,the tests performed on site, presented in sec-tion 4, still indicate that the 3G receptionon Mickelsorarna could be satisfactory.

2.3 Dynamic Domain Name Sys-tem

Each computer or device connected to theInternet is identified with an Internet Pro-tocol (IP) address, provided by the Internetservice provider. The addresses for the mostcommon IP version, IPv4, are in short sup-ply; devices connected to Local Area Net-works (LANs) therefore normally share oneor several global IP addresses3 when commu-nicating with other devices outside the LAN.For example, your Internet service provideronly assigns one IPv4 address to your homerouter, and this address is shared amongall devices, connected to the router, for out-bound communication. This works fine whencommunication is initiated within the LANto an external device with a global address,as when visiting websites, but it becomesproblematic when a device on the Internetwants to initiate communication with a de-vice inside a LAN (Kurose & Ross, 2010).

Central SCADA systems must be ableto initiate communication to local systems;this then corresponds to the previously pre-sented problematic situation as PLCs nor-mally are found within a local system LAN.Furthermore, Internet service providers nor-mally assign addresses dynamically. A devicecan therefore be assigned a new address fromtime to time. In order to secure a communica-tion channel, over the Internet and initiated

23G stand for the third generation of mobiletelecommunication technology and supports commu-nication rates of at least 200 kbits/s (Wikipedia,n.d.).

3A global IP address differs from local IPaddresses by being globally routable.

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by central SCADA systems, the followingtwo problems must be solved:

1. The router connecting a local systemLAN to the internet must be reach-able on a fixed address.

2. Inbound communication from centralsystems to a local system LAN mustbe recognizable and rerouted to thecorrect device within the LAN.

The first problem can be solved in twodifferent ways: 1) At an additional cost, itis possible to lease static IP addresses fromInternet service providers. 2) IP addressescan be linked to domain names, such aswww.google.fi, and a dynamic IP addresscan thus be linked to a static domain name(Kurose & Ross, 2010). Free services existthat allows a router (if this service is sup-ported) or a computer to associate their IPaddress with a domain name. Each timethe router’s or the computer’s IP addresschanges, it simply announces its new IP ad-dress, whereupon the service updates the IPaddress associated with a selected domainname. Hence, the router or the computercan always be reached using a fixed domainname. A couple of such service providers are:NO-IP, DNSdynamic, Dyn, and ZoneEdit.

The second problem can be solved by leas-ing a fixed IPv4 address for the server run-ning the SCADA program. As the SCADAsoftware is communicating through a fixedTransmission Control Protocol (TCP) port,local system routers can use port forwardingto route traffic from a specific IP addressand TCP port to a specific device within theLAN. Hence, communication between localand central systems over the Internet requireat least one static global IPv4 address, andif dynamic domain names can not be sup-ported for the local systems, then anotherstatic global IPv4 address is needed for eachlocal system as well.

3 System specification

The currently implemented electric sys-tem at Mickelsorarna is depicted in Fig-

ure 1. Conceptually, the electric demandshould be covered with wind and solar power,but in practice this is not the case and gener-ators are used during such circumstances. Alocal control system on site should thereforebe able to control generator usage in orderto make sure that power is always available.Additionally, the local systems should moni-tor total electricity demand and production,as well as the radiator based heating system.

In order to comply with the above pur-poses, it was here determined that the localsystem should monitor:

Temperatures outdoors, inside the cafete-ria, at the top and bottom in the hotwater tank, and in the ingoing/outgoingwater pipes to the radiator system.

Voltages for both the generator batteriesand the battery bank.

Power production by the generator andpower demand for the cafeteria, the ac-commodations, and for the whole site.

High and low levels for the fuel tank.

Taken together, the above requires local sys-tem PLCs to have the capacity to handle thesignals listed in Table A-1 (Appendix A).

Central systems located on the mainlandshould gather data from the local system onsite, provide an overview of the heating sys-tem as well as the current electricity demandand production, allow for remote control ofthe electricity production, and store gatheredmeasurement values in a database. Addition-ally, the control and monitoring offered bythe central systems HMI must be accessibleremotely.

4 Network accessibility tests

Coverage maps for different network op-erators indicate that access to a 3G net-

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Figure 1: Simplified flow-chart of the electrical system on Mickelsorarna with local systemmeasurement points marked, adapted from (Puig et al., 2012).

work on Mickelsorarna might not be guar-anteed. For this reason, a connectivity testwas carried out on site (coordinates 63.4604,21.7731 on Google maps). The test equip-ment consisted of a Huavei USB 3G-modem,provided by Saunalahti (owned by Elisa Oyj),and a laptop. This equipment was placedinside the coast guard station (main build-ing) at its highest point. From this loca-tion, both the 2G:EDGE and 3G:HSPA+networks were reachable, and both were sub-sequently tested with a separate ping andspeed test.

A ping test sends a packet of predefinedsize to a remote web service, in this caseto cosm, and measures the delay betweentransmission and received response (response

time). Here, the test was performed with theAxence NetTools software, using a packetsize of 1024 bytes and a threshold time of5000 ms (max response time before a packetis considered lost). The results from a 5 minlong ping test for both networks are shownin Table 1. Package loss for the 3G:HSPA+network was 0 % and the average responsetime was 290 ms. Corresponding numbersfor the 2G:EDGE network were 5 % and 1094ms respectively.

The speed test utilized is a common webservice speed test. This test measures down-load and upload rates to a close by internetserver and hence provides an estimate ofthe speed of an internet connection. Resultsobtained from this speed test are shown in

Table 1: Results from 5 minute long ping tests with different network connections and usingthe Axence NetTools software

Packets Response time (ms)Network Sent Received Lost Avg. Min Max

2G-EDGE 334 316 (95 %) 18 (5 %) 1094 678 46463G-HSPA+ 282 282 (100 %) 0 (0 %) 292 261 423

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Table 2: Measured download and uploadrates for the two network connections

Network Download Upload

2G-EDGE 0.08 Mbit/s 0.55 Mbit/s3G-HSPA+ 2.88 Mbit/s 1.45 Mbit/s

Table 2. The 3G:HSPA+ network performedgreat with a download rate of 2.88 Mbit/sand an upload rate of 1.45 Mbit/s, whereasthe 2G:EDGE network performed signifi-cantly worse with a download rate of 0.08Mbit/s and an upload rate of 0.55 Mbit/s.However, contrary to the ping test, this testdoes not show the amount of lost packetsduring a specific time.

Even if the above tests indicate that a 3Ginternet connection could connect devices onMickelsorarna to the Internet, the reliabilityof such a connection should also be takeninto account. The implemented tests wereperformed during midday on one day only. Itis therefore possible that the network couldperform worse during evenings, weekend, orduring days with different weather conditions.In order to rule out such events, it would berecommended to redo the connectivity testunder a longer time period before a decisionto use a 3G network is taken.

5 Proposed solution

We propose a SCADA system based onthe structure in Figure 2 for control

and monitoring of the off-grid energy solutionat Mickelsorarna. This structure allows localsystems to operate independently and alsooffers good possibilities for extending theSCADA system to other island groups inthe future. That is, similar local systemsas the one suggested for Mickelsorarna canbe installed on other sites and supervisedfrom the same central system. This is madepossible by letting the complete system usethe Internet as its communication channel.

Below follows a more detailed descriptionof the local systems, the central systems, theHMI, and possible products.

5.1 Local systems

The local system consists of one or severalPLCs (or other similar devices). These col-lect data from sensors and send control sig-nals to actuators. Local PLCs can, for exam-ple, be programmed to start the generatorsautomatically when the voltage in the bat-tery bank drops below a certain threshold.Similarly, alarms can also be generated inresponse to a low fuel level.

If needed, a computer or a touch screencan be used to provide a local HMI. Thiscould be useful for presenting local sensorreadings and for controlling certain aspectsof the energy solution manually. Dependingon the hardware, this local HMI could be con-nected directly to the PLC or via the router.The local HMI together with local controlalgorithms then makes it possible for a lo-cal system to function independently. Thatis, the local system will continue to worknormally even if the connection to centralsystems is lost.

Internet connectivity is required for com-munication with the central systems locatedon the mainland. The local system shouldtherefore be equipped with a 3G router thatconnects the local system LAN to the In-ternet. As presented in subsection 2.3, thisrouter needs to be reachable using a staticglobal IP address or with a domain name.However, only certain routers support dy-namic domain name services and this haveto be checked in advance. Additionally, notall SCADA software support replacing IPaddresses with domain names and for thesereason it might be better to lease a static IPaddress.

In order to avoid unnecessary devices fortranslation between different communicationprotocols, it is recommended that the usedPLC supports TCP/IP communication. Ifseveral PLCs are needed in order to complywith the I/O list in Table A-1 (Appendix A),these might have to be connected in a mas-ter slave like fashion using a product specificprotocol. This makes sure that all IO chan-nels can be accessed from the master PLC.The 3G router can only port forward traffic

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Figure 2: Proposed SCADA solution for remote monitoring and control of off-grid energysolutions at remote islands.

from central systems to one device withinthe local system LAN, and it is thereforeimportant that all IOs are accessible fromthis device.

5.2 The central system and itsHMI

The central system consist of a server with astatic IP address running the SCADA soft-ware together with backup systems. Theserver will collect measurements and vari-able data from local systems and store thesevalues in a database. This makes it possibleto keep a historical record on, for example,generator running times, electricity produc-tion and demand, and temperatures. Thecentral system also has access to local systemIOs, which allows for a remote start of thegenerator in response to an increased antic-ipated demand or for adjustments of othercontrol signals.

Present states, alarms, historical data,and possible control measures for all localsystems are presented using a HMI connectedto the central systems. A human operatorcan therefore get an overview of all connected

local systems and also set control parame-ters for these. As this HMI is running on thecentral system server, the human operatorhave to be localized at the server or accessit remotely. Depending on the SCADA soft-ware used, this can be accomplished trougheither a web interface or a remote desktopconnection. Hence, assuming internet con-nectivity, it becomes possible for a humanoperator to access the HMI remotely fromanywhere in the world.

5.3 Products and costs

Both Regin and National Instruments havesuitable product families and accompanyingSCADA software that would fit the require-ments for the proposed solution. Regin offertwo PLC like devices (EXOflex and EXOcom-pact) that are used for building automationsystems, whereas National Instruments havea PLC like device called compactRIO.

The hardware and software cost for im-plementing the proposed system will amountto 10 000 – 15 000 AC. Additional installa-tion costs will also derive from installing allsystems, programming the PLCs, and from

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setting up the SCADA system. Once in-stalled, there might further be yearly feesfor some software licenses and for static IPaddresses.

6 Summary

Some remote islands in the Kvarkenarchipelago are equipped with nature sta-tions, cafes, and accommodations possibil-ities, and these buildings require off-gridenergy solutions in order to maintain opera-tion. This report has presented a possiblestructure for a SCADA system meant tocentralise control of such off-grid energysolutions. The solution consist of a centralserver, located on the main land, that cangather data and send control signals to localsystems on remote island groups over theInternet. Each local system is responsiblefor controlling the local energy solution, andit is also capable to do so if the connec-tion to the mainland is lost. As no wiredInternet connections are available in thearchipelago, each local systems connects tothe Internet using a 3G connection. Networkcoverage varies in the archipelago, but apromising connectivity test was carried outon Mickelsorarna. At present, the systemwas specified for only one local system, on

Mickelsorarna, but the proposed SCADAsystem can be scaled up to handle localsystems on multiple island groups.

References

Cegrell, T. & Sandberg, U. (1994). Indus-triella styrsystem. SIFU.

Kurose, J. F. & Ross, K. W. (2010). Com-puter networking: a top-down approach.New York: Pearson, cop. 2010.

Levon-instituutti. (2012). Pisara meressa:tutkimus- ja kehitysohjelma. Unpub-lished report.

Puig, O. A., Eebes, T., Hopchet, C., Lah-maidi, R., Liang, H., & Lillqvist, S.(2012). European project semester: offgrid energy supply solution. Unpub-lished report.

Vaasa Energy Institute. (n.d.). Energy in-stitute [Webpage]. Retrieved June 13,2013, from http://vei.fi/content/en/11501/10/10.html

Wikipedia. (n.d.). 3G. Retrieved February24, 2014, from http://en.wikipedia.org/wiki/3G

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A I/O list for local system PLCs

Table A-1: Suggested I/O list for local system PLCs on Mickelsorarna

I/O Type Range Location/Description

AI-01 Temperature -30 ◦C – 30 ◦C CafeteriaAI-02 Temperature -30 ◦C – 30 ◦C OutdoorsAI-03 Temperature -30 ◦C – 100 ◦C Water temp. (to radiators)AI-04 Temperature -30 ◦C – 100 ◦C Water temp. (from radiators)AI-05 Temperature -30 ◦C – 100 ◦C Water tank temp. (top)AI-06 Temperature -30 ◦C – 100 ◦C Water tank temp. (bottom)AI-07 Voltage 0 – 60 VDC Battery bankAI-08 Voltage 0 – 24 VDC Generator batteryAI-09 Power 230 VAC, 0 – 60 A Cafeteria demandAI-10 Power 230 VAC, 0 – 60 A Accommodation demandAI-11 Power 230 VAC, 0 – 60 A Total demandAI-12 Power 230 VAC, 0 – 60 A Generator supply

DI-01 Low level ON/OFF Fuel level (Fuel tank)DI-02 High level ON/OFF Fuel level (Fuel tank)

DO-01 Switch ON/OFF Main powerDO-02 Switch ON/OFF Battery bankDO-03 Switch ON/OFF Fuel pumpDO-04 Switch ON/OFF GeneratorDO-05 Switch ON/OFF Water pump

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