Power Generation Automation – Requirements
Wi-Fi, a WLAN conforming to IEEE 802.11b is emerging as a good replacement for LAN. It allows people to log onto the Internet and receive e-mails on the move. WiMAX an 802.16 wireless metropolitan-area network with a range of 50 km, facilitates wireless broadband access in metros and rural areas, and is a cost effective alternative to cables...
The growth of the power sector is a key parameter to drive economic development. Over the years, installed generating capacity in India has increased from a meagre 1713 MW in 1950 to 288.665 GW as on 29th Feb., 2016. Electricity generation has also increased from 5.1 billion kWh in 1950 to 1048.673 billion kWh in 2014-15 indicating of 8.43% even though the per capita consumption of electricity in India is only 1010 kWh (2014-15), which is abysmally low compared to 4000 KWh of China with developed nations averaging around 15000 KWh of developed nations. As per IEA estimation, the per-capita energy consumption in India will be 1895 kWh by 2030. Even against this per capita consumption, the installed capacity should be more than 5, 00,000 MW by 2030 along with associated transmission and distribution network.
The Global Trends in Power Sector
Europe: State of the art technology & automation; deregulation.
Japan: State of the art technology & automation; deregulation.
US: Newer technologies & automation; deregulation on hold.
Middle East: Mix of new & not so new technologies & automation; preparing for deregulation.
Asia: Slow trend to acquire new technologies; Non-serious deregulation.
India: Slow adoption of new technologies; deregulation decelerated; huge gap between demand & supply; huge technical & commercial losses.
Present State of Information Technology in India
It has been observed that the approach of the Power Companies/Utilities in implementing IT has been piecemeal with standalone applications deployed for a limited operational requirement. In other words, IT has been used as a tool to address a specific issue at a time and not as a long-term, holistic strategy. The gap in IT adoption at home and abroad is apparent and glaring.
Common IT Strategy in All Power Utilities
From an overall view of the power sector in India, the nature of processes and other issues are similar across different utilities. It is, therefore, possible to prepare a common IT strategy. The common IT strategy can then be adopted by individual utilities, customising it for their specific needs, taking into account their functions and operational processes. The investments in IT would need to be phased and prioritised taking into account business criticality, organisation readiness and value to business. The implementation of IT would be long-term, and the advantages accrue only through disciplined usage. Therefore, to make it viable as well as to gain confidence and commitment of the users, several short-term, highly visible IT applications must be delivered with clearly measurable benefits. In this respect, introduction of automation in Power generation plants shall bring about immediate efficiency thus increasing generation from the same generators.
System Requirements for the Generation Plant Automation
The functions and the business processes in power system network are as per Table 1.
The automation modules should cover all these processes and all the applications are required to be integrated with centralised control. Further details for Generation automation are given in Table 2.
Case Study of 10 MW Biomass Based Plant in Village Jalkheri (Punjab)
The utilities are very cautious in selecting and implementing computerised automation in power plants because already pneumatic and other remote controls exist. Therefore, normally, the mechanical operations are automated as can be seen in the case study of 10 MW Biomass (rice/wheat straw, mustard straw, rice husk, saw dust, cotton waste, or tree chips etc.) based plant of Punjab State Power Corporation Limited (erstwhile PSEB) set up in village Jalkheri (Distt. Patiala) in 1991. This is basically a mini thermal plant, which uses biomass as fuel instead of coal for releasing heat energy. Automation of the mechanical functions of this plant has been carried out by installing signal transmitters (transducers) at various locations as shown in logic control screen shot. The temperature/pressure signals are picked up by these transducers and are transmitted to the Programmable Logical Units (PLCc) via copper cables. The PLCs perform I/O functions and are further linked to the computer control unit. The screen shot of the control is as under in Figure 1.
The logic control has all the necessary commands. The trends with respect to various equipment’s under control are displayed in screen under Trends Display. Any abnormal behaviour of any equipment sets an alarm which is displayed in the screen as Alarms Display. The unit can be set for manual or for auto control as shown in Figure 2. The control can be applied to equipment’s as shown in Figure 3.
One can control the governor to regulate the steam in the turbine, the air supply and furnace draught can be changed and in case of fault in any equipment such as pumps etc., the standby can also be selected while sitting before the computer screen. The automation of the plant has facilitated the real time monitoring and control of the plant. This automation application can be applied for electrical controls as well as for asset management. Different plants can be networked and controlled from a distance location as shown in Figure 4.
Plant functions such as operation, maintenance, and management should be tightly integrated across all plant functional areas. The system should embrace the latest information and communication technologies (ICT), and multiple communication channels. Flexible, switchable interfaces should be at the heart of the systems.
Classification of Data Communications
Communication is and will increasingly be a must tool for the operation and maintenance of the power network as well as for administrative purposes. Technically speaking, from being a limiting factor, the increasing communication capacities now provide possibilities for operating and maintaining the power network and related businesses in different and more efficient ways. There are now diverse media for communications as discussed hereunder:
PLC (Power Line Communication) or BPL (Broadband over Power Lines), also called EOP (Ethernet Over Power) refers to the transmission of signals over electrical lines, at frequencies other than the 50/60 Hz of the alternating current. This technology turns any electrical plug into a potential connection to all telecommunication services.
Although it has been widely used on SCADA systems from the beginning, the bandwidth is quite limited. Nevertheless, further research done over the last years is encouraging and it has been established that the information can be transmitted over low-tension electrical links at speeds of up to 45 Mb/s. Anyway, although high speed PLC transmission is still under development, it is the recommended solution – as it allows enterprises to cut down on expenses in infrastructure, and it is also an alternative to other technologies in case their use is not profitable, or not possible.
• Telephone is the original communications network that uses the existing phone lines to deliver broadband. Broadband performance over telephone can vary a lot, depending on whether line is VDSL, ADSL or ADSL2+.
• VDSL is the best broadband service available with speeds up to 20Mbps or more in a radius of about 800 m from exchange or broadband cabinet.
• ADSL2+ delivers speeds of up to 10Mbps to properties located within a 2km radius from a broadband cabinet. ADSL is the most basic broadband connection available on telephone network. It delivers around 2 Mbps for distances up to 6km from the local cabinet.
DSL delivers reliable, high-speed office-to-office connectivity over traditional copper wires and is available in most regions from ISPs, local phone companies or alternative exchange carriers. DSL provides speeds of 100 Mbps (megabits per second) or so. DSL permits the transfer of everything from e-mail and Web pages to multimedia files, enables remote users to rapidly access and make use of applications.
Fibre allows to do more online in less time with minimal or no disruptions. This internationally favoured broadband connection uses fibre optic cable, which houses hundreds of strands of fibre to transport huge amounts of data at speeds not seen in any other connection type. Fibre performance doesn’t degrade over distance, so broadband speed is consistent no matter how near or far the business is located from the exchange or cabinet. Fiber-optic broadband communication highways (range of 100 Mb/s), make it possible to build WAN, providing high capacity facilities to/from office sites and substations. Most of the private operators have rolled out state of the art optic fiber based networks crisscrossing the country besides adopting the wireless in local loop route for connectivity. Fiber optic is the ideal material of serial communication used because of larger data transfer over lesser area with no electromagnetic interference, no external noise and is practically maintenance free.
The use of radio and microwave signals is also a good solution to long distance transmissions. Solutions based on the 802.11 standard offer reach of up to several kilometres. It must be taken under consideration that the longer the link is, the lower is the effective transmission rate that can be obtained. Also, an important investment must be done in the antenna equipment when trying to communicate two distant points.
Wi-Fi & WiMax
Wi-Fi (wireless fidelity), a WLAN conforming to IEEE 802.11b is emerging as a good replacement for LAN. It allows people to log onto the Internet and receive e-mails on the move. WiMAX (Worldwide Interoperability for Microwave Access) an 802.16 wireless metropolitan-area network with a range of 50 km, facilitates wireless broadband access in metros and rural areas, and is a cost effective alternative to cables. Wireless network attached storage (NAS) functioning as file servers lets users access their allotted storage space on WI-Fi. Radio Frequency Identification (RFID) makes use of radio frequency waves to capture data in small, lightweight electronic read/write storage devices called `tags`. Data is accessible through handheld and fixed -mount readers in real time, using RF signals to transfer data to and from tags even in absence of line of sight.
Selection of Communication Media
But while selecting the communication media, the focus should, to a greater extent, be on analysing communication needs and requirements, providing a basis for a technical design. The different needs and requirements can be classified into three different main categories, reflecting the degree of importance of various communications needs.
• Real-time operational communication requirements
• Administrative communication requirements
Real-Time Operational Communication Requirements
Real-time operational communication encompasses communication in real time that is required to maintain operation of the power system. This class is, in turn, divided into real-time operational data communication and real-time operational speech communication.
• Protection function
• Status function
The communication is characterised by the fact that interaction must take place in real time, with hard time requirements. The communication requirements define the design of the technical solutions. For protection purposes, messages should be transmitted within a very short time frame. The maximum allowed time is in the range of 12-20 ms, depending on the type of protection scheme. The requirement has its origin in the fact that fault current disconnection shall function within approximately 100 ms.
Status functions are of the Supervisory Control And Data Acquisition/Energy Management System (SCADA/EMS) type. Measured values must not be older than 15s, when arriving at the control centre. Breaker information shall arrive no later than 2 s after the event has occurred.
Administrative Communication Requirements
Data and information is made available to different functionaries for analysis and decision making so as to reduce down time, increase efficiency and profitability etc.
Interconnection of Workstations/Computers
The workstations/computers, servers and other devices installed in the power houses & at control centres are interconnected as discussed above by selecting particular communication technology depending upon the function and speed requirement. The interconnection of such devices in a particular geographical area is known as LAN (Local Area Network).
To connect two or more LANs together, each LAN needs a device called an access router. The access router connects to a switch or hub on the local network and serves as a gateway to the WAN. The access routers establish LAN-to-LAN connections and forward network traffic between users at the remote sites.
WAN traffic can travel via the Internet, the public telephone network or a private network. Internet Service Providers (ISPs), telephone companies and many other alternate exchange carriers provide private network connections, which are dedicated lines that the power utility can lease.
Private networks operate independently of the public telephone infrastructure and the Internet and therefore offer the highest security. Connectivity over a public infrastructure is simpler to operate and less costly. A foremost security solution is VPN (Virtual Private Network). VPNs create protective virtual 'tunnels' through which data can travel between two locations.
They safeguard business communications over a public network like the Internet. The WAN connection depends on the data traffic and the types of connectivity services that are available in the region.
Operations and Maintenance
Having deployed the IT solutions, there is a need to sustain, maintain and effectively run the same. This is done by Networking and Systems Management (NSM) platforms which can be done in – house or can be outsourced.
2014 was most remarkable for demonstrating that everything connected to the Internet can, and will be hacked. On daily basis we heard of retailers, financial institutions, technology companies etc. being hacked. Therefore, cybersecurity particularly of generating stations is of utmost importance. To safeguard the proprietary, sensitive or business-critical communications, we need to deploy a VPN solution.
A viable, affordable strategy, VPNs enable data to travel in encrypted virtual 'tunnels' between sites and offer very high levels of protection with the use of VPN-enabled firewalls. Use of password and authentication techniques must be mandatory to permits only those who are designated to enter the network.
An automation system must be designed to optimise the economics of plant assets. Deregulation has acquired greater awareness of optimising operations. Maximising availability, efficiency and safety are crucial roles of an automation system. Furthermore, monitoring, reporting, and controlling emissions are required to be elevated to the highest corporate level, largely because of regulatory scrutiny. In sum, the current operational environment places more emphasis on automation and proper strategies to mitigate the key challenges for the development of power sector to ensure India’s march towards inclusive growth. But as is the present reality, in spite of being fore-runner in IT solutions, India just barely scratched the surface of automation in the power supply system.
AUTHOR CREDIT & PHOTOGRAPH
K S Sidhu
B. E. Elec. (Hon’s) & MBA/IT
Ex Joint Director /Regulations, PSEB
Also, Ex Joint Director /Regulations
Punjab State Electricity Regulatory Commission