978-1-4799-3732-5/14/$31.00 ©2014 IEEE

Automation System Based On SIMATIC S7 300 PLC, for a Hydro Power Plant

R. Butuza, I. Nascu, O.Giurgioiu, R.Crisan Department of Automation

Technical University of Cluj-Napoca G. Bariţiu 26-28, 400027, Cluj-Napoca, Romania

alexbutuza@gmail.com, ioan.nascu@aut.utcluj.ro, octavian.giurgioiu@gmail.com, ruben.crisan@aut.utcluj.ro

Abstract – Based on SIMATIC S7-313C programmable logic controller (PLC) and SIMATIC TP 177B operating touch panel (HMI), this work presents an automation solution for monitoring and controlling a micro hydro power plant (MHC). Using the specified PLC and HMI, there was implemented a reliable automated system, which produces about 120 KWH of green energy, 24 hours a day, 7 days per week. The system was developed, tested and commissioned at ZANOAGA Drinking Water Treatment Plant and the owner is APASERV VALEA JIULUI.

Keywords — SCADA (Supervisory Control and Data Acquisition), PLC (Programmable Logic Controller), HMI (Human Machine Interface), Local Control, Remote Control, Micro Hydro Power Plant.

I. INTRODUCTION In the past, people used rivers for agricultural activities and

wheat grinding. Nowadays, the power of rivers is used not only for these types of activities, but for green energy production although [1]. The electrical power generated in hydro power plants is one of the most available and renewable energy sources in the world [2]. Two of the most important benefits of hydropower are its provision of clean and renewable energy [3]. SARFRAZ Ahmad Khan of Pakistan developed a new technology for hydro power energy production. His idea doesn’t require a basin to be built and the impact on the environment is minimal. The system based on his technology requires less financial resources for operating and maintenance. [4] The automation systems consisting of PLC and HMI, or PLC and SCADA systems can be reliable and economical solutions for monitoring and controlling different types of hydro stations [5]. Next chapters of this paper will describe the automation system, based on SIMATIC S7-300 programmable logic controller and SIMATIC TP 177B operating touch panel, for controlling and monitoring a small hydro power plant. The old automation system for this plant was based on third party electronic hardware and software components,

developed for this type of process. The most significant disadvantage of the old system was a very hard maintenance, after many years of functionality. So, the decision of developing and implementing a new automation system was the best solution for the customer, in order to keep alive this plant. Starting from an asynchrony generator and a Francis turbine, the project mission was to develop a reliable automation system for monitoring and controlling the hydro power plant. The system architecture chosen for this plant, allows interconnection between the PLC and a central control room, using different industrial communication protocols, such as: PROFIBUS DP, MPI or Industrial Ethernet. If PROFIBUS DP and MPI protocols are available immediately using CPU’s integrated interfaces, the Industrial Ethernet interface can be used, by adding a new SIMATIC Ethernet Processor in controller central rack. The main requirements for the new automation systems are: safety in exploitation, reliability, low cost maintenance, service time as short as possible, easy way of detecting and solving alarms, by implementing a new and modern alarm logging management system.

II. MHC MAIN FUNCTIONS The micro hydro power plant is equipped with a horizontally Francis turbine and one asynchrony generator with nominal speed rate of 1500 rpm. Two new valves were installed and commissioned on the main inlet pipe of drinking water and bypass pipe. New electromechanical equipment was installed for turbine control, called AKD. Different types of sensors were installed, for pressure and temperatures monitoring. The actual values read from these sensors are used as interlocks in PLC software application. The main steps on project implementation are shown in figure1. One electrical cabinet was built, for integrating all the electrical circuits, necessary for controlling the following equipment: inlet valve, bypass valve, lubrication pumps, AKD and main switch. Although, the electrical cabinet integrate

circuits for monitoring all the sensors in this system such as: inlet pipe water pressure, generator bearings temperatures, valves positioners and generator speed rate. The brain of the automatic system is the AKD. This is actually an electro-mechanic screw, driven by an inverter, which drives the turbine for opening and closing, depending on the logic implemented. The PLC uses an analogue output channel, configured for 0-10V, for AKD opening and closing.

Figure 1 – Automation System Developing Steps The AKD is used both in normal operation, for increasing or decreasing the pressure on the turbine but in emergency shutdown cases although, for decreasing to zero the pressure on turbine and stop the MHC, that is way an uninterruptible power supply (UPS) was installed, for a permanently power supply on the electrical circuits. Actually, there were installed two uninterruptible power supplies, one for PLC supply and one for AKD, inlet valve and bypass valve power circuits. In case of main power fault, this two power supplies guarantees safety closing of AKD and inlet valve and bypass opening. The electrical cabinet contains a central automation rack, equipped with a central processor unit, electronic modules for digital input and output signals, electronic modules for analogue input and output signals, one PAC 3200 for electrical parameters monitoring and one operating touch panel, type TP 177B 6”.

PAC 3200 is a power meter and it is used for electrical parameters monitoring, in low voltage power distribution. Main electrical parameters that can be monitored using this device are: phase to neutral voltage, phase to phase voltage, current, apparent power per phase, active power per phase, reactive power per phase, total apparent power, total active power, total reactive power, power factor, total power factor, line frequency, active energy, reactive energy, apparent energy.[7] Main functions developed for the PLC software are: automatic opening and closing of inlet and bypass valves, inlet water pressure monitoring, automatic bearings lubrication during starting and stopping the aggregate, bearings temperature monitoring, generator speed rate monitoring, automatic AKD opening and closing. Main protections implemented in control algorithm are: low and high voltage protection, inlet water pressure protection and over speed protection. Automation system consisting of programmable logic controller, operating touch panel and electrical measurement unit, PAC 3200, uses industrial PROFIBUS protocol, for data exchange. Regarding the operating mode of micro hydro aggregate, there were defined and implemented two operating modes: Local Mode and Remote Mode. In Local Mode, all the commands to electrical equipment, such as open / close inlet / bypass valve, start / stop lubrication pumps are sent from main control cabinet, using hard wired push buttons and selection keys, without PLC. In Remote Mode, the commands are sent from PLC, using Automatic Mode or Manual Mode, depending on the selection made on operating touch panel.

III. MHC SYSTEM ARCHITECTURE In the figure 2 it is displayed the automation system architecture. Main components of system architecture are: automation central rack, consisting of S7-300 CPU and ELECTRONIC MODULES for digital and analogue signals, electronic equipment for electrical parameters measurements, SENTRON PAC 3200 and the operating touch panel. Local Operating Mode was implemented for maintenance issues. This operating mode supposes that all commands to electrical equipment are sent by operator, using local selection keys and buttons, directly to electrical switch equipment, without using the PLC. In other words, this is a pure electrical regime. Remote Operating Mode is divided in two different branches: Manual Mode and Auto Mode. Manual Mode supposes that the operator will use the commands available on the operating panel, for manipulating all the equipment involved in this process. Most important commands, which the operator can sent to electrical equipment are: starting and stopping motors of lubrication pumps, opening and closing valves, coupling and decoupling main switch. Manual Operating Mode is conceptually identically with Local Operating Mode, but the

major difference is that in Local Mode, the PLC and HMI functionalities are not used. Auto Mode is actually “the brain” of the MHC. During this

operating mode, all the protections are active, and the algorithm is the one that controls the entire plant. The functional diagram of the MHC is displayed in figure 3. There were defined 4 steps for automatic AKD opening and closing, because it is important for maintaining inlet pressure, over the minimum accepted value. The operator will set the maximum value for the opening rate, and the PLC calculates the opening rate for each step. When the preset value is reached, the PLC will set the new set point. Every step, before the new set point is activated, the algorithm will check the inlet pressure value and it will define the new set point, only if the current value of the pressure is over the minimum value. Otherwise the PLC will start closing the AKD, until the inlet pressure is over the minimum value. Auto Mode was developed using three possible states for the system: Starting, Started and Stopping. When the operator

activates automatic start, the system goes from stopped state to starting state, only if all the equipment involved is in a ready to operation state. During starting mode, the system will open

the inlet valve in the same time with closing the bypass valve and the AKD will be opened. After the generator speed is over the minimum set value, the AKD opening rate is over a predefined value or the inlet valve position is over a minimum value, the PLC will link the system to the electrical network by coupling the main switch. The AKD will continue opening until the maximum allowed position is reached. This is the point, where the PLC reads the inlet pressure and acts by opening or closing the AKD, for maintaining the pressure over the accepted minimum value.

IV. IMPLEMENTATION MHC model described above was implemented using a SIMATIC S7 313C-2DP CPU with MPI and PROFIBUS interfaces built in.

Figure 2 – MHC Model

Operating interface was developed using SIMATIC WINCC Flexible platform and it is running on a SIMATIC TP 177B operating touch panel. Data exchange between the PLC and HMI is realized using PROFIBUS DP industrial protocol over RS 485 serial interface. PROFIBUS network integrates although, the electronic module SENTRON PAC 3200. A MAINSPRO decoupling relay was used for protecting the generator. All the protections like overvoltage, low voltage and overcurrent are implemented inside of this relay. The PLC monitors the signals coming from the protection relay and if a protection became active, the MHC will be stop. Electrical parameters read using SENTRON module, are displayed in figure 4. Process parameters, like: inlet water pressure, generator speed rate, bearings temperatures, temperatures of motor windings, valves opening rates are displayed in the main screen shown in figure 5. Opening rates for inlet and bypass valves are monitored using two analogs input channels which read the electrical

signals coming from the integrated positioners of the AUMA valves, using 4-20 mA unified signal. Inlet water pressure value is monitored using an IFM analog sensor for pressure monitoring and it is integrated in the PLC

using an analog input channel configured for 4-20 mA unified signal. The inlet (admission) valve installed in this location is produced by AUMA Company. Commands circuits for it were designed using RDOL (Reversible Direct Online) scheme, using two contactors for direct and reverse movements. The following protections signals are available for AUMA motor: thermal overload, opening torque and closing torque. All three signals are integrated as protective interlocks inside the PLC. The bypass valve is although produced by AUMA company and all the electrical protections used for admission valve, were activated in this case too. Using command buttons displayed in figure 6, the operator is able to activate the following commands: Start MHC group, Stop MHC group, Fast Stop the MHC group, Restart the group, Auto Mode activation, Manual Mode activation. The operator has the possibility to monitor the status of the automatic group using the information displayed in figure 6. A special screen, displayed in figure 7, was developed for process parameters settings.

There were defined two different levels for the inlet pressure as follows: Minimum Inlet Water Pressure at Starting and Minimum Inlet Water Pressure in Running.

Figure 3 – MHC Algorithm

Figure 4 – Electricals parameters monitoring

Using first parameter, the operator defines minimum value of the inlet pressure necessary for MHC starting. If the current value of the pressure is lower than this parameter, the MHC cannot be started.

Figure 5 – Main Screen of HMI

Second parameter is a protection condition, while MHC is started. If actual pressure of the inlet valve decreasing under this parameter, in running mode, more than a predefined time, the PLC will stop the MHC. This is a protecting condition for avoiding depressurization of the inlet pipe.

In normal operation, when the pressure sensor indicates a pressure decreasing, the PLC will start closing the AKD, as follows: the AKD opening value will be decreased with a preset value (3%). After the new value was set, a monitoring timer is started.

Figure 6 – MHC Commands

If the pressure decreasing does not stop, AKD opening rate will be decreased with another preset value. If, during this sequence, the real value of the inlet water decreases under the minimum value, the MHC will be stopped.

Figure 7 – Process parameters setting Next part of this work, will describe two of the most important components, implemented in the SCADA application: alarms system and protection levels. There were defined three methods for stopping the MHC: stopping caused by sensors information or fault conditions, stopping caused by protections and emergency stop. Emergency stop will be activated, is one of the next conditions becomes true: general protection coming from protection relay or UPS (Uninterruptible Power Supply) protection is activated.

MHC stopping is caused although if one of the next sensors activates the command: AKD analog position sensor indicates a fault value, like channel fault or wire break, inlet pressure is under minimum accepted value, generator over speed, generator speed monitoring sensor indicates a fault value, like channel fault or wire break and one of the temperature measuring sensors indicate a fault value. Another way to stop the MHC is using the protection signals. If one of the protection signals, defined, is activated, than the PLC will stop the micro hydro aggregate. The differences between the three ways of MHC stopping are the sequence that the PLC starts. Emergency stop of the process will switch off the generator from the network first, even during this sequence, an over speed of the generator occurs. During normal stop, the AKD and inlet valve will start closing and only after a period of time, the main switch will be unlinked. During this sequence, the speed of the generator remains constant, about 1500 rpm, but the force generated by the water is decreased. As a result of force decreasing, when the generator is unlinked, an over speed of the generator is avoided. In case of any malfunction during normal operation, there were defined suggestive alarms, not only for generator protection but for maintenance issues although. All the alarms are stored in the main memory of the operating panel and they are not erased, until the maintenance or operating personnel acknowledge them. Alarms are displayed on a screen, similar with the screen in the next image.

Figure 8 – Process alarms and warnings There were defined two levels of alarms: warnings and faults. The difference between the two types is that any fault in the system will stop the automatic sequence, while the warning messages were defined only for operating personnel alert. Both the alarms and the warnings have date and time stamp. Even if a warning occurs and disappears before the operator

acknowledge it, the operating panel will storage the event and it won’t erase it form the list only after acknowledge command.

V. CONCLUSIONS The automation system described in this work is physically implemented in ZANOAGA MHC and belongs to APA SERV VALEA JIULUI. During the commissioning phase, there were tested different scenarios, like starting, stopping in emergency cases, stopping in normal mode, inlet pressure variation during normal operation. The production energy level is about 2.4 MW/day. All the requirements that the customer asked in his tender were satisfied, that’s way the project was successfully closed. Rivers in mountain areas of Romania can provide low cost electricity with reduced impact on the environment. Besides the production of renewable and clean energy, small hydropower plants (MHC) have the following advantages: - flooding prevention by courses regulation; - providing water for people in the area; - economical increase by creation of new jobs - source of energy for isolated settlements; - opportunities for fishing [6].

VI. REFERENCES

[1] http://www.alternative-energy-news.info/technology/hydro/

[2] D. Mircescu, A. Astilean, O. Ghiran, “Complex Automation System of a Low Power Hydro plant”, 2010 IEEE International Conference on Automation,Quality and Testing, Robotics, CLUJ–NAPOCA, RO, May 2012.

[3] http://www.hydrofoundation.org/hydropower-education.html

[4] http://www.alternative-energy-news.info/technology/hydro/

[5] D. Montnorency, C. Montmorency, “Applying Standardized Industrial

Automation to the Small Hydro Plant.”, Innovative Small and Medium Hydro

Technologies Workshop, Portland, Oregon, 2007

[6] http://www.renespo-bucharest.com/hydropower-conference.html

[7] SENTRON PAC3200 Manual, 10/2007, A5E01168664B-03

[8] S7-300 Programmable Controller CPU Specifications, CPUs 312C to 314C-2DP/PtP, A5E00105475-01