I. Introduction

A SCADA system is, basically, a software tool permitting remote data in a technological process that can be controlled through communication tools (Padrón-Ramos, 2011;Rodríguez-Penin, 2013). Its main advantages are: it minimizes the operators tasks, achieves superior performance, increases the productivity, and offers higher security.

Currently, the SCADA systems are practically employed in every aspect of society including the automotive, railway, aerospace, chemical, petrochemical, food and beverages, textile, pharmaceutical, and electrical industries. Consequently, several companies around the world —such as Siemens, Schneider Electric, ABB, Wonderware, and Alstom— commercialize their own development platforms both for their usage in a punctual process and for their general usage in several processes.

The automation of the industrial sector is an important challenge in Cuba because of the elevated costs entailed in the installation and launching of projects using applications related with this. For this reason, the objectives creating benefits for the nation economy are prioritized such as the Cayo Santa María electrical system. This latter guarantees the generation, transmission, and distribution of all the electrical energy used in this important touristic area located in the center of the country. This system is not connected to the national network, so it is an isolated power supply system (Elices & Rouco, 2001). Its energy is produced through a scheme of batteries in engine-generators (gen-set) different on their technology(Hyundai, Mtu, and Man) and its generation capacity(1,700, 1,800, and 3,850 kW, respectively). Apart from the generation power plant, the system includes an electrical substation with 13.8 kV using Alstom technology, which can be remotely or locally commanded.

In the last decade, the increase in the installed generation capacity due to the continuous construction of installations related to the tourism entails a considerable challenge, even for the most experienced operators. The fact of being an isolated system is important to highlight that, when a minor incident arises, it might cause a chain reaction ending in a generalized power outage, affecting the quality of service provided to the clients. For the system management, an energetic control center where the information is integrated from both the generation and the electric substation in a unique SCADA system is not available. Each generation technology —such as the electric substation— has an independent supervisor; further, the generation control centers of the substation are geographically moved, resulting in inefficiencies in the operation.

The situation previously described was the trigger for the investigation described in this document, where the main objective is to implement a SCADA system by integrating the generation power plant and the electric substation and also providing flexible elements relative to the future projects, allowing to improve the operation of the electric system.

The structure of this article is as follow: section II presents a general background related with the implementation of SCADA systems to monitor electric systems; in section III, we describe the design of the local network. Section IV presents the architecture of the data gathering system, section V details the configuration of the reports and the coding of the web client. Section VI presents the results and their corresponding discussion and section VII finalizes the document with the conclusions.

II. Background

Several research works in the scientific literature address topics related with the design and implementation of SCADA systems for monitoring and supervising electrical systems. These systems are both isolated and synchronized in the network. We present a brief summary of the most important for us.

Villegas (2015) presents the design and implementation of a data gathering and monitoring system for the synchronous generators of the power experimental simulator for electrical systems of the SEPI-ESIME. This simulator is composed of four control areas and it is mainly used for research and teaching purposes. From the equipment point of view, it contains all the types of electrical machinery: special, escalated, and not escalated. It is even able to interconnect renewable energy sources. Data gathering is performed in real-time with configurable sampling times; the set of variables to monitor includes both the electrical and the mechanical variables of the generators. For this, a Field Programmable Gate Array [FPGA] is employed together with LabVIEW and MATLAB as software tools for monitoring and analyzing the signals.

Weber (2011) and Lanas (2011) present the implementation of a SCADA platform and a specialized program for the energy resources management. Both works pursue the optimization in the dispatch and the minimization of the operational costs in the isolated sustainable electrification system of Huatacondo (Chile). The electrical system is formed by some diesel gen-sets and distributed generation units based on renewable and non-conventional energies such as photovoltaic panels, storage systems based on batteries, and a wind power plant. For the interconnection of these generation elements, Ethernet, RS-485, and IEEE 802.15.4 (ZigBee) are employed through the OPC and Modbus protocols. The information flow is centralized in a server including a secure link through Internet via a Virtual Private Network [VPN] to remotely monitor the isolated system.

Manassero et al., (2012) propose an Integral Supervision System [ISS] to monitor in real-time both the physical variables of the gasoline system and the electrical variables of the engine-generators in the thermal power plants managed by the Energía Argentina company. The ISS is based on a distributed control system with Programmable Logic Controllers [PLC] through a physical network with star and bus topologies. Specifically, the data gathering is handled in three levels: a field level with RS-485 links through the Modbus RTU protocol; a second level using Modbus TCP over Ethernet in the automatons such as input/output distributed modules, Human-Machine Interfaces [HMI], and a gateway processing all the measurements to transmit them to the control center in the company; and a third level based on a satellite interface between the controller and the control center.

Silupú (2016) shows the design of a SCADA system to integrate the 66 kV substations of the electric interconnection called “Lote 1AB” to the distributed SCADA operated by the Pluspetrol Norte company. The substations interconnection is supported by an Ethernet network over optical fiber; the field variables gathering in each substation employs the Modbus (both RTU and TCP) protocol and the IEC61850 standard. Security interfaces such as firewall, DeMilitarized Zones [DMZ], and VPN are handled in the control center seeking to separate the industrial network from the corporate one. The development platform of Wonderware is employed as the software tool for this project.

In general terms, the most employed technologies in the development of SCADA systems are several and they mainly depend of the available economical resources to be invested in equipment. In the case of systems made by sources powered by renewable energies or low scale gen-sets, the trend is to use platforms such as Arduino and PIC microcontrollers (Fernández & Duarte, 2015; Guamán et al., 2016).This choice is substantiated by the considerable savings in the hardware processing the information gathered in the field and in the few variables to consider when monitoring these systems.

The isolated micro-networks connect electrical substations with high-power engine-generators for continuous operation plans. For this reason, SCADA commercial and control systems supported in PLC are generally installed and concurrently, the so-called Distribution Management Systems [DMS] are also installed to allow the integration of the SCADA with applications oriented to the operation of electrical networks.

Choosing to use proprietary solutions is a decision based on the complexity of the energy conversion processes, in the large number of variables to consider, and in the environmental conditions that the equipment will deal with. Their advantages are related with the optimization in the control and operation processes; furthermore, the necessary information to perform the equipment maintenance is provided. One of the main disadvantages of these systems relies in the fact of offering low flexibility when new devices are added; this requires investment to hire specialized engineering services.

In order to implement the proposed SCADA application we used Eros v.5.9, a development environment commercialized by the SERCONI Cuban company. It has reliable and tested functions in the production environments, although it does not offer all the solutions provided by other solutions such as WinCC, Intouch, and Movicon. Nevertheless, Eros complies with the essential operational and functional requirements to integrate the diversity of existing technologies at a fraction of the cost.

III. Design of the Local Network

The architecture of the physical network (see Figure 1) is based on a star topology using multimode fiber optics with 50/125 μm of diameter. The redundant link with six yarns between both control centers is seeking the benefit of an alternate communication way between the two sites with larger information exchange.

Within the local Networks, two Virtual Local Area Networks [VLAN] converge: an operative and a corporate one. Furthermore, the communication with the load dispatcher is backed up through a contract with the Cuban telecommunications company [ETECSA] by using two links via modem, one for each VLAN.

In every node of the fiber there exists: an Optical Distribution Frame [ODF], a media converter from fiber to copper, and a switch. These switches depending on the functionality are layer 2 and 3 devices of the Open System Interconnection [OSI] model. In order to manage the virtual subnetworks, two layer-3 switches located in both control centers are employed.

Figure 1
Architecture of the local network

IV. Data Gathering System Architecture

Substation

The 13.8 kV electrical substation is operated through DS Agile of Alstom (Figure 2). This solution is based on a main IEC 61850 network over Ethernet with redundant ring topology. Some Intelligent Electronic Devices [IED] such as bay controllers, network analyzers, digital protections, etc., are connected to the main network.

Figure 2
DS Agile automation system

For the remote control of the substation, three gateways based on Alstom devices are employed. These devices are configured with the IEC 60870-5-101/104 protocols, Dnp3, and the OPC [OLE for Process Control] standard. Likewise, the DAPServer controller(Alstom, 2013) is included; this one has an intrinsic real-time database to collect data and then transmit them —in this particular case— using the Modbus communications protocol over Ethernet. The integration of the substation parameters is carried out via the DAPServer controller.

Mtu Generation

Structurally, the Mtu engine-generators are located inside containers and —at the same time— all of them are within an additional container called mid voltage container. In this one, the output switches to the substation are located. For the working regime of each gen-set, the internal combustion engines work with diesel fuel.

The control and protection of each engine-generator pair is performed by the Mtu Diesel Engine Controller [MDEC] coupled to the Advanced Gen-set Controller [AGC]. The ACG is an IED based on a microprocessor and it has a triphasic measurement system, which is the base to perform all the control and protection functions of the generator (DEIF, 2008).

The integration of these groups is performed via the Can Bus J1939 and Modbus (Figure 3) industrial protocols. Each AGC is linked to the Moba Nport5600 serial port server and this latter is coupled to the SCADA via TCP/IP Ethernet. The Nport server gathers all the variables and using Component Object Model [COM] handlers, it establishes the connection in a transparent way between the serial ports and the COM local port of the host computer (Moxa, 2010).

Figure 3
Data gathering of the Mtu groups

Hyundai and Man Generation

The generation process of electrical energy used by these engine-generator technologies differs from the Mtu groups due to the fact that the combustion engines use fuel-oil as combustible. This fuel-oil is viscous and heavy, so it requires a previous heating in order the engine can use it. For this, a combustible treatment unit, a steam boiler, and a water chemical treatment plant are utilized.

Both processes are controlled through a distributed automation system based on PLC and SCADA systems. In the case of the Hyundai technology, the employed PLC is a Siemens S7-300 plus the Generator Parallel Controller [GPC] of DEIF. For SCADA we have the SIMATIC WinCC version 6.2, also from Siemens. On the other hand, the Man groups handle the series AC800 PLC and the industrial SCADA 800xA version 5.0, both from ABB.

The unification of the parameters in these groups to the application is employed through the OPC open standard. This protocol offers high reliability in the communications and considerable time savings in its configuration. In order to achieve this purpose, it is essential to use the Distributed Component Object Model [DCOM] technology and the OPC server finder —OPCENUM.exe— because the exchange between the servers and the client is remotely performed. Figure 4 shows the general architecture of the industrial network to integrate the Hyundai and Man generation.

Figure 4
Data gathering in the Hyundai and Man groups

V. Reporting System and Web Client

The Eros report system [SREros] allows the generation of reports from data and measurements obtained from the connection between Eros and its clients; they are presented as a web page or as a Microsoft Excel report. Specifically for this system, reports related with the generation, loads in the output circuits, energies, and the reserves are configured using 1-hour intervals and configured as Excel outputs.

On the other hand, the need of monitoring the electrical system parameters from the corporate network are based on a web client. Normally, the proprietary solutions integrate web servers and only a web browser is required. Once SCADA is in execution mode, it is possible to visualize the desired synoptics through this interface. In the Eros particular case, this is not directly available; however, dynamic web pages can be created via EROSNet for this purpose.

EROSNet is a COM server presented as Dynamic Link Library [DLL]. In general, this library exports the basic functionalities of Eros throughout the interaction with other systems supporting the COM technology. The applications based on EROSNet are the ones following the client-server paradigm, where Eros is the server and the client is the application developed by the user. Hence, only the creation of instances of the EROSClient class is required to deploy a client (Rodríguez-Hidalgo, 2010).

The client coding to acquire the variables included in the SCADA is developed employing the JavaScript language by using two fundamental methods: the first one is associated with the connection with Eros; the second one returns the variables directly as a character string. From the design point of view, the graphical interface is coded by using the Bootstrap front-end framework. This set of open code tools is compatible with most of the web browsers, it has design templates based on HTML and CSS and optional JavaScript extensions. Other features are related with the fact that the Bootstrap applications are responsive or adaptable; i.e., the pages are dynamically adapted according to the features of the employed device.

The representation of the system relevant information in the client is performed via tables by using the DataTables component of the JQuery library in JavaScript. DataTables provides controls and advanced interactions with HTML tables such as searching filters and paging elements (“JQuery…”, 2015).

VI. Results and Discussion

The data gathering system validation was performed using the ModbusPoll tool and the OPC client integrated in Eros. We performed three real tests with the sampling times defining the functional and operational requirements of the SCADA: 250 ms for variables related with the generation and 1,000 ms for the remaining ones.

The first test assessed the Modbus TCP link with the Dap server. As pointed before, this controller congregates the substation variables through the IEC61850 standard. The direct connection with the device is achieved after configuring the IP address, the identifier, and the port —by default, Modbus TCP uses the port 502—. The addressed variables are input registers [function 04] and discrete output registers [function 02].

Figure 5 shows the satisfactory reading of the selected variables. Several polls are performed [TX] providing results without error [Err]. The variables corresponding to discrete inputs represent states in a switch of the substation, whilst the input registers —the floating type ones— are the measurements of a switching cell. Finally, the part of the frame reading is illustrated.

The second experiment assessed the communication with the AGC controllers, specifically the one operating the Mtu1 group. The test was performed similarly to the previous case, the only difference is that now the link is serial Modbus. In order to establish connection, we defined the serial port to use, the speed and transmission mode, the datum length, parity, and the stop bit. The addressed variables are the input and discrete input registers; the first ones are measurements of the generator electrical parameters, whilst the discrete input one is a 16-bit register, where each bit represents an alarm triggered to protect the generator in case of a short circuit. If none alarm is triggered, the register value is zero. Figure 6 presents the successful connection and a fraction of the frame

Figure 5.
Measurements of input and output registers associated to the Dap server

Figure 6
Measurements of discrete input and output registers associated to the AGC controller

The third experiment [Figure 7] visualizes the communication with the Hyundai engine-generators through OPC. The link is performed after enabling and defining the authentication and security levels for both the DCOM and OPCenum.exe. The test shows a representative number of total variables handled —in this case, Boolean variables— symbolizing the stop/operation states of these engine-generators.

Figure 7
Registers reading of the Hyundai groups through OPC

From the user interface point of view, the operator interacts with 4 main synoptics from a total of 29 conforming the supervisor. The so-called begin is precisely where the application starts after the register data are introduced [login]. This interface has the general or total system measurements and the synoptic called generation allows the operator to supervise the state of every group and access to specific parameters of each one of them. The synoptic substation is conformed with the variables of each switching cell and the input and energy distribution circuits. Lastly, the interface related with the energetic consumption calculates the possible losses from the exported and billed energies. The SCADA also includes synoptics associated with the handling of alarms and trend graphs with historical data for posterior analysis. In Figure 8, the interface associated with the generation is displayed, whilst Figure 9 shows a section of the web client.

Figure 8
Interface related with the generation

Figure 9
Hyundai section of the web client

VII. Conclusions

The implementation of the SCADA system complied with the functional and operational requirements pre-established in its conception. The initial launch —started in 2015— has contributed to polish the operation of the electrical system.

The network design entailed in a successful interconnection of all the objectives at a physical level; the creation of virtual subnetworks made possible to isolate the technological network from the corporate, increasing the security.

The project execution was an economically viable solution due to the fact that it solved the problem associated to the purchasing of a high complexity and value software. The use of Eros allowed us to integrate several technologies and equipment currently in use without the need of betting to other platforms with higher features but also higher associated cost.

The coding of the web client helped in the system monitoring from the corporate network by easing the access to all the information included in the supervisor.

The application —in general terms— guarantees high flexibility towards future modifications for other projects such as the integration of new Mtu groups and measurements related with the fuel control.

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Author notes

Additional information

How to cite: Samada, S., Pozo, O., & Martínez, A. (2018). Web Client and SCADA Applications for Monitoring the “Cayo Santa María” Isolated Electric System. Sistemas & Telemática, 16(47), 59-70. https://doi.org/10.18046/syt.v16i47.3216