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Communication Possibilities for Remote Control and Condition Monitoring of

Small-Scale Hydro Power Plant

Tuomo Lindh

Lappeenranta University of

Technology

Department of Electrical

EngineeringP. O. Box 20,

Lappeenranta, Finland

+358 5 621 6779

Fax +358 5 621 6799

E-mail: [email protected]

Jero Ahola


Technology




+358 5 621 6761

Fax +358 5 621 6799


Jarmo Partanen


Technology




+358 5 621 6702

Fax +358 5 621 6799


Heikki Pirttiniemi

Waterpumps WP Oy

Karhusuontie 39

00780 Helsinki

Helsinki, Finland

+358 9 3855 907

Fax +358 9 345 4002

E-mail:[email protected]

ABSTRACT

In this paper we compare different remote controlling

methods for a small-scale hydropower plant in terms of cost

efficiency, complexity and capability to provide

information. In addition, requirements of each solution for

hardware software and communication media are

discussed. Examples of different solutions are presented by

implementations in laboratory conditions and in the pilot

plants of Tirva HPP in Valkeala and Hiitolanjoen Voima

HPP in Simpele. The costs of the presented controlling

applications are much lower than in traditional remote

control systems used in power plants.

Keywords: Small-scale hydro power, remote controlling,

remote access, condition monitoring.

1 INTRODUCTION

Small-scale hydropower plants can be profitable if both the

investment costs and the running costs are low enough.

Especially, if the government subsidises the small-scalerenewable energy production. However, because the amount of

energy production is low, the plants controlling equipment

should be inexpensive. On the other hand, the plant should be

remote controllable so that the labour costs are minimised. The

labour costs are normally very low in fully automated plants butthey will be increased as service visits are done. The optimum

between investments in remote controlling and amount of

labour costs depends on the type, size and location of the plant.

In addition, controlling solution depends on the skills ofoperators. For example, if the controlling tasks require

programming skills, normal operator is not able to control the

plant or at least the risks of use are too high. Direct plantcontroller connection, field bus gateways, remote access server

based controlling and SMS based controlling are the

alternatives for the conventional distribution automation. Inaddition, web-based techniques can be applied in controlling

tasks. The condition monitoring and remote diagnostics hasalso an important role in unmanned plants. It is an integrated

part of the field level automation.

2 TYPICAL INFRASTRUCTURE OF SMALL SCALE

POWER PLANT

The small-scale or micro-scale hydro power plant can have a

power generation from approximately 50 kW to 2 MW (figure

1). The main circuit of a small-scale hydro power plant is

illustrated in figure 2. In the most usual cases the generators arelow voltage synchronous or asynchronous generators. The

switchboard of the plant automatically runs startup and

shutdown procedures and controls the power generation

according to a set value. The set value is calculated for examplefrom the difference between actual level and aimed level of the

up water. The energy produced by generators is fed to medium

voltage network through distribution transformer. The energy is

usually measured from low voltage side of the transformer.

Figure 1. A small-scale power plant (1 MW) in rural area faraway from service personnel.

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MF MF

F

3

200 kW

690 /400Vcos=0.841500r/min

1.1 kW

400Vcos =0.81500r/min

200kW

690/ 400Vcos =0.841500r/min

1.1kW

400Vcos =0.81500r/min

3~ 50Hz 380V

V

250kVAr

3x185+50(Cu),

150Cu

1000A

MKEM 3x2.5+2.5

40A 40A

Powerfactor cotroller

Cu 30x10

500 A 500 A

63Aaux supply

3x300Cu +120 Cu

0Q0

1Q0 2Q0

VS1

2x150Cu

1Q1 2Q1

0Q120A

0FS2

CONTROLCIRCUITS

1F2

1K2 2K2

2F2

MKEM 3x2.5+2.5

CONTROLCIRCUITS

Surge arrester

2x(3x300 Cu) +2x120Cu)

150Cu

3x300Cu +120Cu

3x185+50 (Cu),

2x(180Cu)

In=800A , Ip=65 kA

3

PE Bar

Figure 2. The main circuit of a small-scale hydro power plant.

The main components are illustrated using pictures.

3 ALTERNATIVES FOR REMOTE CONTROLLING

Some alternatives for remote controlling of small-scale power

plant are presented in this chapter.

Plant PLC and GSM- or PTT-modemThe simplest remote controlling or monitoring implementation

requires only GSM- or PTT-modem and approximately 30 rows

of programmable logic (PLC) program code (figure 3). This

applies to one directional data transfer, usually a SMS message

that alarms or just informs the personnel. If a PLC program canhandle the most usual abnormal situations this kind of an

implementation can reduce the service costs delivering the

necessary information about the failure or alarm. Based on this

information can be determined whether the service visit is

required or not. In pilot hydro plants, the typical messages areloss of mains or return of mains. The investment costs of this

type of system is approximately 1000.

This type of implementation can also receive SMS messages.However, it requires more PLC code than a simple

unidirectional data communications and the complexity of thePLC program increases but the implementation costs still

remain low. The number of feasible instructions is quite limiteddue to restrictions PLC (memory restriction).

PLCPLC PLC

PLC

Plant Controller

Generator Controllers

Field Bus

GSM GSM

Figure 3. The simplest remote monitoring implementation, oneway data transfer from PLC to GSM using SMS.

It is also possible to have a more sophisticated monitoring and

remote control by using a very simple fieldbus protocol through

a modem. This implementation requires that remote controllingof the plant (user side) is done by a computer instead of a GSM

telephone. A schema of communications is illustrated in figure

4 and implementation is illustrated in figure 5.The functionalityof the implementation is described in the text and the flowchart

(figure 6) below.

PLCPLC PLC

PLC

Plant Controller


Field Bus

GSM GSM

PC

Remote

Control

Figure 4. Schema of simple PLC based remote control for a

small-scale power plant.

Figure 5. Implementation of PLC based remote control. Simplefieldus protocol is driven over a telephone line.

When something abnormal happens in the plant the plant

controller PLC changes modem to SMS mode and sends the

SMS message to the remote controlling PC. Subsequently, the

PLC changes the modem in normal mode and waits forconnection from the remote control program. When the call to

modem is received, the PLC answers to the call and starts

waiting for the fielbus command from remote PC that operates

as master unit. Respectively, the plant controller PLC operates

as slave. The whole data memory area of the plant controllerPLC can be read and written by the specially built PC program.

The hardware costs are increased with a client side computer

only. The implementation is still quite simple but the

programming work both in plant side and in remote controller

side are remarkably bigger that in previously presented cases.However, when the programs are made the costs remain very

low with increased controlling capacity compared to previously

presented communication structures.

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MESSAGESTO

SEND

WAIT FOR MODEMEVENTS

MODEMCOMMUNICATION

RUNNING

CHANGE TO SMS MODE

SEND THE MESSAGE

BACK TO NORMAL MODE

MODEMCALLS

WAIT FOR FIELDBUSCOMMANDS

FIELDBUSCOMMAND

OK

ESCAPE CODE

NO

NO

NO

NO

SEND ERRORCODE

NO

YES

YES

YES

YES

YES

PROCESS AND SEND

Figure 6. Initialisation and execution of PLC remote control.

Plant PLC, local PC-supervision, modem line and remote PCIf a versatile plan man machine interface (MMI) interface is

required at the plant, one solution is industrial PC or in somecases even an ordinary PC (figure 7). In this implementation,the control and reporting possibilities become much better than

in previous implementations and number of feasible functions

increases. In this implementation also all the communication

examples presented in previous paragraphs are possible.

PLCPLC PLC

PLC

Plant Controller


Field Bus

GSM GSM

PC

Remote

Control

PC

Local

Control

Figure 7. Versatile PC based remote controlling for a small-

scale power plant.

Local PC can send SMS-messages and transfer data between plant controller PLC and the remote controlling computer.

Local PC works as a fieldbus gateway. This type of

implementation has some advantageous properties. The amount

of transferred data between plant and remote controller is low

when only the information that is needed is transferred. Thiskind of implementation has one drawback. The computer of the

plant cannot be administered with this solution. If full

administration is needed the remote access program can be used

instead of this solution.

The remote access programs such as PCAnywhere or VNCoffer cheap or free solution of remote controlling. They can be

used in WAN-network or with modems also. When used with

modems a dial-up Internet connection of PC is used. The local

plant computer acts as a remote access master and remote useras slave. The advantage of the remote access program is that the

user can control the plant computer as a local user. The user canopen programs, shut programs even re-program the plant PLC

if needed. The disadvantage of the solution is that the amountof transferred data is big when the whole display of the plant

computer is transferred to the user. Every action takes lot of

time even if the display of the plant computer is transferred to

user with minimum number of colours. Another drawback isthat the user can do everything that can be done locally

meaning that even the removal of programs is possible. Theunauthorized use is prevented with passwords of remote access

program and by restricting the access to plant from predefinedphone numbers only.

Internet/JAVA techniques can be used with this hardware

structure also. The same dial up Internet connection that is used

with remote access programs can be used to provide WEB-

services such as interactive applet with monitoring and

controlling possibilities. The user only needs Internet browserand modem in the client side computer. The disadvantages of

this kind of system are also the slow communication speed and

the single user environment. The later restriction also applies to

WAP connections.

Integration to existing DA-systems of electricity companyIf the remote control of the plant (substation level automation)

is made by systems separate from existing integrated DA-system of an electricity company the operational costs may

increase. However, it is possible to integrate some of the

systems presented previously to existing DA by very simple

and low costs method. The leading DA/DSM systems utilizedatabases with ODBC and JDBC connectivity. The integration

to DA/DSM can be done in control room by these methods and

control of small-scale plant can be done utilizing the database

services as will be presented.

The communication infrastructure presented in this chapter

allows multiple simultaneous users, which is not normally

needed in controlling tasks in small-scale hydro power plants.However, it may be an attractive alternative for example in the

cases where green energy is sold. The customers can view the

energy production in Internet. Another reason to present this

method here, as mentioned before, is that it supplies means forintegration of systems presented here to existing DA/DSM

systems used in electricity companies. The system is described

in detail in [Lin01].

At the control centre level or at the plant level the systems canbe integrated using databases. The control room level software

is illustrated in figure 8. On the other hand, the samefunctionality can be installed at the plant level (figure 10). All

measurement data or registers of devices are read and writtenthrough database tables. Global connection is available for user

by a standard web-browser. When a connection to http-portof server is opened, an applet with graphical user interface

(GUI) and connection data is loaded to the browser. Based onthe log data, the system determines the actions that are allowed

for user. The user can execute only the functions that are codedto the applet.

LAN

DA/DSM

Data Interface

CONTROL CENTER LEVEL

Data Storage

Management

ODBC client OPC client

Data managerDataStoragedb

(WINDOWS service )

PLANT CONTROLLER

Fieldbus Master

MODEM LINE

Fieldbus Slave

Figure 8. Integration between existing DA/DSM and remote

control of small-scale plant.

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At program level, a connection to a database is formed withJDBC API. The JDBC is a standardised interface that provides

connectivity to a wide range of SQL databases. JDBC driver isloaded with Java applet. Installation of programs or any other

files is not needed in a client computer. In our demonstration,

type 3 JDBC driver is used which means that calls are not made

from client to DBMS-server directly. The JDBC driver

translates JDBC calls to a protocol that server side data servertranslates to a DBMS protocol.

The connection to local databases can be done using standard

ODBC or OPC interfaces. In our demonstration it was donewith OPC connection. The OPC server handles connections to

the Profibus and serves simultaneously multiple OPC clients.

The server is capable of reading and writing registers ofindividual device connected to field bus.

Database server acts as the software interface between web

applications or control centre applications (DA/DSM) andapplications performing data transmission between control

centre level and field level. The database server is a standard

Microsof SQL Server. Measured values, configuration of

field device registers (OPC tags) and requests for changes of

registers are all stored in the database tables.

A Windows NT service was developed for this demonstration.It consists of OPC client part, ODBC client part and of service

routines. The service monitors the changes in configuration

tables. Based on these changes, the service transfers data

through OPC and ODBC interfaces between the fieldbus

devices and database server.

4 REQUIREMENTS OF CONDITION MONITORING

There are needs for condition monitoring also in small-scale

power plants. The small-scale plants are typically unmanned

due to economical limitations. Therefore, the condition

monitoring should be based on automatic and remotediagnostics. The condition monitoring and diagnostics system

have two requirements. It should detect possible failures before

they lead to emergency shutdown of the plant. Secondly, thesystem should be robust and not to alarm when a real failure

does not exist.

For example, in small-scale hydro power plants there are

numerous important objects that should be monitored. The most

important objects to be monitored are generator and turbine.

Overheating can destroy the windings of the generator.

Respectively, an increase of humidity indicates a leakage inturbine-generator package. The bearings are also possible

reason for generator failure. Therefore, also a bearing

monitoring should be introduced.

The condition monitoring equipment can be connected into theplants field bus and the remote diagnostics can be realised by

communications methods presented in previous chapters.

Generally it can be assumed that the condition monitoringfunctions do not need large data transfer capacity. The need of

capacity depends mainly on the fact, where the condition

monitoring data is analysed. Local analysis and intelligent

sensors shrink the needed bandwidth. Respectively, transferringof raw measurement data dramatically increases need of the

bandwidth.

Condition monitoring functions for underwater hydro powergenerators have been developed. A microprocessor based

sensor can be installed inside the generators frame. The sensortakes supply power directly from the terminals of the generator.

The sensor measures and analyses for example vibrations,temperature and humidity. The analysed data is transferred

from the sensor using generators feeder cable as a

communications channel. Based on [Aho02], low voltage

power cables are applicable for power-line communications. In

system under development, the master unit is located at theswitchboard. It receives the data that the sensor has sent and

links it into plants field bus. Thus, the condition monitoring

data is available for remote diagnostics.

5 EXPERIMENTS FROM PILOT PLANTS

The first pilot, Tirva HPP, was equipped with the GSM-modem

connected to PLC as in figure 3. With this very simple schemathe number of service visits was reduced remarkably. The

problem was that the SMS message could not inform the

personnel as much as they wanted. For example, alarms for

intruders were many (surveillance of the yard was included),but no harm was done when checked in plant. Also the need for

local reporting with event log was discovered. The local PC

was added and because there was an existing telephone line at

the plant the PTT modem was installed in parallel with theGSM modem. Further, the remote access program was installed

so that events can be checked remotely. The system includes

also the WEB-camera that shows the view at the dam. The

number of unnecessary service visits was further decreased.The repayment of investment is estimated to be two years. The

final schema is presented in figure 7.

PLCPLC PLC

PLC

Plant Controller


Field Bus

GSM GSM

PC

Remote

Control

PC Local

Control

Modem ModemTelephone line

Figure 9. The structure of the controlling system in pilot plantin Tirva.

Second pilot in Simpele also includes local PC-controlling

program. The wired telephone line is used for the energy

measurement collection use only. Therefore the GSM have to

be used in communication between plant and the service personnel. The principal structure of the communication is as

presented in Fig. 3. The investment costs of communicationsare low but the operational costs are higher than in previous

example because of the higher costs of communication.

6 CONCLUSIONS

It is too expensive to connect micro scale or small scale power

plant as a part of the conventional distribution automation

system with local RTU, (perhaps local SCADA), radio

communication and remote SCADA. This does not mean thatthe unmanned use is too expensive nor that the system cannot

be integrated to existing DA/DSM. GSM-modem or PTT-

modem connected to plant controller PLC offer the very low

cost methods for remote control. The service cost reductions pay the investment practically in all cases where unmanned

operation of plant is in use and also if the plant is partiallymanned (not 24 hours per day).

If the monitoring of plants operation is needed locally and the

local environmental conditions are good enough the use of PC

is justified. Furthermore, if only the one directional

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communication is used, the personnel have to visit the plantalmost weekly in order to be sure that the no service actions are

needed. Fieldbus gateway through modem and loacal computerrequires less communication capacity than the use of the remote

access programs when only the needed information is

transferred. However, the remote access programs make

possible more versatile control of the plant. The integration to

existing DA/DSM can be done at control room level using opendata interfaces. The condition monitoring functions can be

integrated as a part of automation systems of a plant and thus as

a part of the remote controlling schema.

WWW -Browser

INTERNET

WAN

Plant ControllerPLC

Field Bus

G G

Hydropower Plant

Process Control Level

ProtectionRelay

GeneratorControllerPLC

Condition

MonitoringDevice

I V f

Process

GeneratorControllerPLC

0

1

2

3

4

5

6

7

8

9

10

1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3

Local Web server

Local Controlling Computer

Figure 10. Plant level Internet connection.

REFERENCES

[Lin01] Tuomo Lindh, Jero Ahola, Jarmo Partanen, Sauli

Antila, Pertti Jrventausta, Kimmo Kivikko, PekkaVerho, Pekka Ruupunen, Web-based monitoring

functions utilising data management system,DistribuTECH Europe 2001, Berlin, Germany, 6-8

November 2001.

[Aho02] Jero Ahola, Tuomo Lindh, Jarmo Partanen,

Determination of Properties of Low Voltage Power

Cables at Frequency Band 100 kHz 30 MHz ,ICEM 2002, Bruges, Belgium 26-28 August, 2002.

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