Data Transmission System
Currently, the reasonable choice of data transmission systems is one of the main problems of information technology in the power sector. Lifen and Huaiyu (2015) wrote, “The wireless sensor network (WSN) technology penetrated from the field of military reconnaissance to industrial areas in recent years, which became the most popular areas of wireless networks” (p. 1). The transmission of information signals about operating modes, power consumption, types and location of the accident, and others is made with the help of energy system’s communication channels. This chapter will discuss an application of wireless sensors in the gas turbine power plant.
The reliability of data transmission systems has a significant effect on the entire power system. The greatest attention is paid to the interference immunity of wireless communication channels in harsh industrial environments. Wireless data transmission is carried out by the means of electromagnetic waves, where external sources of electromagnetic interference affect the radio channel. The rapid and accurate location of the accident overhead power transmission line reduces the search time of accident and fault correction time, and, thus, increases the reliability of the entire system. In addition, the data transmission system is a key element of intelligent systems in the energy sector.
More specifically, the wireless solution may be defined as the ability to initiate actions or communicate by radio frequency or infrared signals, as opposed to conventional wired connections. Thus, in order to perform any actions, it is necessary to have at least two devices: a transmitter and a receiver. One or both of them can operate as transceivers. The beginning of RF-technology invention can be regarded as the one of radio, but, until recently, the technology has not been used in the automation of building systems. However, it is necessary to note that significant changes in many industries, namely in the industry of control means with the wireless devices, do not have the tangible application.
The concept of wireless communication and control is definitely attractive, but it cannot serve as an incentive for adoption and wide dissemination of technology – at least among the engineers, setting requirements for engineering solutions. Economic benefits and the ability to move wireless devices, where you want to change the internal layout of the building company are the spread incentives of wireless devices.
The Concept of Wireless Sensors
A sensor is a primary transducer, an element of measurement, signal, regulating or control unit of systems, which converts the monitored quantities, namely pressure, temperature, frequency, velocity, displacement, strain, electrical current, etc. to the signal. Also, it is convenient to use it to measure, transmit, storage and register data, as well as impact on the controlled processes. According to the Powerbyproxi (2015), “Wireless sensors are used to measure numerous parameters including temperature, vibration, and pressure depending on the application and are often part of a wider network which enables for more accurate monitoring of phenomena” (p. 1). The structure of the sensor includes receptive or sensitive authority and one or more intermediate converters. The sensor consists of only one sensing body, namely a thermocouple, a resistance thermometer detector, a strain gage and others. Output signals vary in kind of energy – electrical, mechanical, pneumatic (rarely, hydraulic) and the nature of modulation of energy flux.
Compared with wired technology, the main advantage of wireless solutions is a quick and easy installation, the low cost and the mobility of staff maintaining the system. Installation is much faster, since there is no need to stretch the wires or install cable channels. Compared with wired devices, saving installation costs of wireless devices can be varied over a wide range, as the type and length of required cables have an impact on this installation. Failure to wire also reduces construction work in rooms with people to a minimum. It is especially important in the reconstruction of flowing during working hours. The wireless technology also gives staff the freedom of movement in the building and gives it an opportunity not to be tied to a workstation or terminal. Reconfiguration of working premises can be made easier, as wireless sensors can be installed almost anywhere within the sensitivity of the receiver. There are many situations, especially in the reconstruction, when wiring is very expensive; for example, when laying in concrete, or impossible, for example, in glass or marble walls or expensive surfaces that cannot be damaged.
Sensors, whose operation is based on measuring the electrical resistance, capacitance, inductance and mutual inductance of the electrical circuit (rheostat, capacitive, inductive sensors, etc.), as well as an electromotive force of induction when exposing to controlled mechanical, acoustic, thermal, electrical, magnetic, optical or radiation values (load cell, displacement, piezoelectric, pressure sensors and photocell) are the most common. According to the classification adopted in the state system of instruments and automation, the sensors refer to the technical means of collection and processing of test data. The sensors are one of the key elements in the remote measurement, telemetry and remote signaling, regulation and control, as well as in a variety of instruments and devices for performing measurements in physics, biology and medicine to control human life, animals or plants. In connection with the automation of the production the sensors for measuring and recording density and concentration of the solutions, the composition and properties of substances, the dynamic viscosity and flow of different media, humidity, transparency, intensity, color, thickness, temperature, elasticity and other parameters, characterizing processes, are of great importance. The sensors based on ultrasound, radio wave, optical, radiation and other methods of measurement are often used for this purpose. Random number generators are used to simulate real-world conditions in testing automatic control systems and computer technology for solving statistical methods.
Wireless Sensors in Gas Turbine Power Plant
The degree of automation of gas turbine power plant allows engineers to eliminate the constant presence of staff in the control unit. Badami (2012) argued, “Advanced sensing and analytics are being used increasingly in power systems, to improve diagnostic and prognostic capabilities for expensive power generation equipment, increase performance and operability, estimate remaining useful life, and manage risk” (p. 1). Control of gas turbine power plants can be made from the main control board that comes with a set of equipment gas turbine power plants. During operation of the gas turbine power plant, three people should provide its operation: an operator, a duty electrician and a mechanic. In case of emergency, a reliable protection system is provided to ensure the safety of personnel, systems and components of gas turbine power plants. Such a protection can be provided with wireless sensors.
The software system of remote monitoring and technical diagnostics are installed on a single computer that is connected to an automatic control system using the communication module. Thus, remote monitoring software reads the sensors directly from the monitoring object of the automatic control system. Further, in this system, there is data processing and distribution: data communication to the server of technical diagnostics and result receipt of the processed data; binary data record and archiving; parameters recorded in the database, according to the serial number of the engine; interactive data presentation. Once a day, there is a transfer of an archive file to the remote monitoring center, through a dedicated internet link. Remote monitoring allows the staff to make the connection in real time and send the entire data package to the remote client.
Software remote monitoring center is installed on a dedicated server, which stores the information that comes from all monitoring sites, according to the accepted format. The data is received in archive files, and then made their decompression, processing and recording the data in the database, according to the serial number of the engine. This server is a part of local network with workstations operators, allowing operators with software to perform the following: connect to the on-line remote monitoring systems (if the internet network is available); view and connect to archived information, using the database locally or remotely; construction of a diagram or archive files.
Wireless Fire Alarm
Currently, the most promising direction in the field of fire safety is a wireless fire alarm of objects. For example, at sites where there is no way to lay cable and other traditional cable lines, wireless fire alarm systems can ensure compliance with the requirements of fire protection for the power plant and other enterprises. Morris (2011) stated, “San Diego Gas & Electric wanted to implement a wireless architecture throughout the Palomar Energy Center combined cycle plant to access data that was previously unattainable through traditional wired solutions” (p. 1). In addition, the installation of fire alarm radio channels makes it possible to significantly reduce the timing of installation and commissioning in the period.
If a fire alarm is installed with irregularities in the case of fire, the cable may burn before the system detects the source of fire. Modern wireless fire alarm systems allow the staff to monitor the dynamics of fire, including the appearance of secondary fires, and quickly manage the evacuation and fire alarm, change the order in view of fire, thanks to the continuous communication between the system’s devices. The efficiency of wireless fire alarm system is achieved by operating all system devices interactively, the use of reserve channels, and constant self-devices in the system, as well as quality control of radio communication between devices. In view of the above, it can be said that the wireless fire alarm system provides not less reliability in operation than a traditional wired system does.
Technical service of wireless fire alarm is an important aspect of the system after commissioning. It is mandatory and is regulated by the rules of fire safety. Here, the wireless fire alarm system has several advantages over a conventional fire alarm. The advantages are obvious: there is no need to clean all the detectors every six months because this procedure shortens their lifespan, the system itself should inform about the degree of dust content in flue chambers of an individual detector; also, there is no need to maintain the cable runs, which significantly affects the maintenance cost.
Professional wireless fire alarm consists of the same components, as the traditional wired fire alarm system; the only difference between them is that the connection between all devices in the system is carried out with a wireless link. In order to understand the benefits of a wireless fire alarm system, it is necessary to know what the structure of a fire protection facility is and which problems it solves. Fire protection systems of buildings and structures are almost everywhere automated, so the question of automatic fire alarm systems is very relevant.
Automatic installation of fire alarm system is designed to perform the following tasks: timely detection of signs of fire, fixing a fire on the basis of detected signs of formation and transmission of fire alarm to the operator panel, the post of fire protection and provided means of fire alarm in an enterprise, the supply command to the target device: the installation of automatic fire extinguishing, ventilation and smoke systems, blocking the devices of elevators and doors, etc.
Automatic fire alarm systems can vary greatly in complexity, composition and number of elements, but have a similar structure. The detectors are sensors of different operating principles (thermal, optical, infrared, etc.). They are the sensors through which the alarm system receives the data on primary signs of fire. Sensors-detectors can detect the occurrence of smoke, heat, a sharp rise in temperature, the appearance of an open flame, which may occur in the infrared or ultraviolet spectrum.
The monitoring device receives and controls information that comes from sensors-detectors through the loops or electrical cables that connect a group of sensors, detectors to the control unit. Typically, the loop combines sensors that monitor the condition of its premises. Loop cables perform a dual function: firstly, transmitting signals from the sensors-detectors to the control unit, and secondly, supply power to the sensors themselves.
By the method of tracking sensor indices, the monitoring devices are divided into targeted and untargeted. Conventional control devices react to the signal in the loop, not knowing which of the units transmits a signal. These devices give a signal about the fire within a loop. If the object consists of a relatively small room, such a precision is usually sufficient.
If the diode shines greenly, the controlled premise is in the “norm”. If the diode is red, it means there is fire or an unauthorized entry in this premise. Motion sensors react well to the movement of air heated by fire and the one of a person, so there is often one system, combining fire and security functions in one small premise. Often, such a security and fire alarm system has cables connected to the sensors of opening the door and windows. In such a simple system, the control device performs all the functions of a central console – evaluates the signals from the sensor signal loops, including, if necessary, warning means, namely siren, light boards, transmits a signal fire to the post of fire protection. Also, the signal concerning opening of the control device and failure is certainly transmitted to the post. In addition, the control device is equipped with a compact source of autonomous power that can maintain the system in working condition, even when power supply takes from several hours to several days. Communicating with the post of fire protection can be carried out via telephone line, a mobile network or through the Internet. Also, an automatic call is provided.
If the object is composed of a large area of premise, localization of a signal via untargeted alarm systems can be achieved by increasing the number of loops, which leads to a complication of the system and results in a decrease of its reliability. In such a case, engineers prefer the address control devices. The address control unit carries out a cyclic two-way communication with sensors-detectors. The device sends, in turn, a request-signal to each of the sensors and receives a reply signal. However, if the unit does not receive the reply, it generates a message about defects. Application of the principle of address makes it possible not only to isolate the sensor’s signal, but also determine the signal’s nature (the “fire”, “smoke”, “movement”, etc.), depending on which sensor is triggered. As you can see, the fire alarm system is a complex set of interconnected devices that support the information exchange. Certain devices are connected between each other by a cable to enable communication. As a result, a complex object can be literally enmeshed in a web of cables of complex security and fire systems. Thus, the wireless fire alarm is a great solution. Thus, this system has a number of undoubted advantages: reduce the number of wires and, consequently, the risk of damage entailing a system failure, save costs on cabling, and equip the fire alarm in fully built and decorated premises without overhaul.
Drawbacks of Wireless Sensors
However, the use of such systems is limited by the fact that wireless fire alarm systems have serious drawbacks: low immunity, false alarms because of the work of powerful electrical appliances, especially electric motors and generators and due to the impact of atmospheric electricity. According to the research in this field, it is necessary to note that this system has some disadvantages. Puers (2005) wrote, “In many cases, the drift can become so important that the amplifier, which is coupled to the sensor, will not be able to follow the signal and will turn into saturation, with of course signal loss as a major consequence” (p. 2). The elements of the system must be in line of sight for reliable signal reception. The presence of partitions significantly reduces the range of interaction of components. Massive metal obstacles can completely shield the signal.
The radio channel cannot be used for the transmission of electric power supply of enough strength, so all the elements of the alarm system must be connected to the mains (which leads to an increase in fire hazards), or have a self-contained power supply (which greatly increases the cost elements). However, in the modern world, fire detectors are widely used, thanks to these small and relatively inexpensive electronic devices, preventing a lot of fire in the early stages of formation. The fire detector, depending on the type (smoke, heat and manual), is designed to respond to its controlled parameter (smoke, temperature, pressing), transmit the alarm at the guard post and run the automation system (warning, smoke, firefighting) with the help of a fire alarm control panel.
However, sometimes it is impossible to determine the reason for a signal without the sign of fire. Such situations are possible because one should remember that when an electric current passes through the power lines and the current of charged particles forms an electromagnetic field. Huertas, Barraza, and Echeverry (2010) argued, “Electromagnetic noise generated around high voltage power lines is an undesirable disturbance, which affects wireless data transmission” (p. 89). Power surges, for example 400 kV, affect devices with high sensitivity; these devices are the wireless sensors. Such surges lead to false alarms and reduce the service life.
It should be noted that point smoke detectors are most prone to false responses. As it is well known, a smoke detector consists of an optical camera and an electronic circuit that analyzes the state of a camera. If you get any solid particles, a dust or insect, the detector will react. Also, the electronic part of the scheme under the influence of electromagnetic interference may issue a false alarm. Therefore, careful consideration should be given to the protection of sensors. Unprotected wireless nodes can serve as a loophole for hackers trying to crack your network. Ways to prevent such a possibility should be communicated to users of wireless sensors, and/or they should be automatically integrated by the manufacturer.
Wireless Temperature Sensors
Application of wireless temperature sensors directly in the hazardous area is possible in the gas turbine power plant. The receiving unit is mounted outside of the hazardous area. Thus, there is no need for expensive installation with safety barriers and power dividers. Wireless signal transmission technology transmits data of temperature measurement from hazardous areas to its outside. The transmitter can be located even in a zone in which an explosive gas mixture is present permanently or for extended periods of time and in a zone in which there is a possibility of presence of explosive gas mixture under normal operating conditions. This makes it possible to abandon sensitive interferences, expensive cabling joints as temperature sensors, based on wireless signal transmission are designed to operate in difficult industrial conditions and explosive zones. Thus, it allows the directors of gas turbine power plants to reduce the costs of maintenance, repair and re-assembling, as compared with systems that transmit measurement data by means of cables. Thanks to these improvements, there is the prospect of using a convenient process of temperature measurement and transmission of data in the totally new areas.
Also, this type of sensor makes it possible in an explosive area to be fully isolated from the “outside world”. The transmitter is also located in the handle of the probe and protected with the water- and dust-proof housing. The sensors being resistant to the ambient temperature to 125 ° C are used where the electronic unit of transmitting device should be located in the immediate area of the working process.
The introduction of advanced technology of wireless signal transmission opens up broad prospects and significantly reduces the installation costs. The following benefits are obvious: long connecting wires used in systems with cable connections tend to create difficulties to the user. Temperature probes with wireless transmission of data over traditional wired models offer an efficient and convenient alternative, especially when using them in the processes at elevated temperatures.
The Cost of Wireless Sensors
Despite the fact that an acceptable price for a typical installation in a residential or office building is strongly dependent on the end user, it can be assumed that over some time, the cost of wireless sensor drops, so it would be acceptable for widespread use in all types of premises. Perillo and Heinzelman (n.d.) wrote, “In the coming years, as advances in micro-fabrication technology allow the cost of manufacturing sensor nodes to continue to drop, increasing deployments of wireless sensor networks are expected, with the networks eventually growing to large numbers of nodes (e.g., thousands)” (p. 1). Although wireless technology is very promising, it cannot solve all the problems of management. It is impossible that the same thing can be used by all users. Therefore, wireless technology should not be seen as a goal, but as a tool to help engineers in the most economical way to achieve goals of comfort of the internal environment of the building.
In essence, the wireless technology quickly became a powerful engineering tool. Therefore, engineers and specialists who define the basic parameters of the control system of building installations, providing for the use of new technology, should understand the capabilities of wireless devices and the limitations of their use.
First of all, most advanced wireless temperature sensors, using radio frequency for communication, are limited by their distance and usually allow the distance of about 30 meters, although this distance can be increased by using repeaters. Obstacles and close materials, such as a solid metal door or chambers, concrete walls or floors can sometimes weaken or even completely block the signal. Therefore, placement of the device can be a very challenging task. For example, when workers install a wireless sensor on a wall containing a large beam of a structural steel, the communication distance of the device can be reduced by half. Also, wireless devices may be susceptible to interferences from other wireless networks operating in the same frequency band from wireless phones, broadband transmitters, microwave ovens, and other radio communication devices.
Some experts in the field of building management believe that the power of batteries of wireless devices may be both a constraint, and an advantage. Energy consumption and battery life are determined by three main factors: the volume of transmitted and/or received information; the distance at which it is necessary to pass this information, as this distance indirectly affects the desired transmit power; a frequency or a cycle time data, for example, every 10 seconds or every minute. However, when setting the battery life it is necessary to take into account the location of the device and the way it is convenient to replace the batteries. At the same time, some experts see the problem is the impact that may have a low voltage battery for continuous operation of critical equipment and system components. However, in general, this problem is solved with a timely warning of the low-voltage batteries to pre-pay attention to it, while the low voltage does not become a problem. In addition, most prevention programs must include the procedures for inspection and maintenance to prevent problems with low voltage batteries.
Wireless Sensors as a Powerful Engineering Tool
The analysis of the installation of wireless sensors in the building shows the ease with which a network of sensors can be organized to monitor the work system. Sohraby, Minoli, and Znati (2007) stated, “The convergence of the Internet, communications, and information technologies, coupled with recent engineering advances, is paving the way for a new generation of inexpensive sensors and actuators, capable of achieving a high order of spatial and temporal resolution and accuracy” (p. 11). This new technology makes it possible to save a lot of time due to the fact that it is necessary to run the signal cables from the sensor nodes to the point of data collection. It is not necessary to worry about violations in the building’s body, which can occur when installing the wiring from the sensor. During the research, it was found out that the reliability of the electronic devices becomes lower with time, but there are reasons to believe that the improvement of these devices will reduce this problem. It was also found out that the absence of ready-to-use sensors that are built into electronic devices creates the greatest obstacles to install a network of wireless sensors.
It is necessary to note that it is possible to install the network of sensors easily and with a large margin of safety, and the experience of many companies shows that this statement is mostly true. Although the degree of safety is still in question, the appeal of the use of wireless sensors for monitoring of climatic parameters of the building is evident.
However, existing wireless solutions provide tangible benefits in building management systems. This industry is in the early stages of technological improvements in the field of wireless devices that can solve a lot of problems that are encountered in the implementation of decisions and control buildings. Thus, the introduction of this technology has become very interesting for engineers and professionals, since it is very important to use such an innovation and keep abreast of methods of its application, affecting the performance and efficiency of life support systems of buildings.