Communication of critical power meter measurements and to manage relays, reclosers, and switchgear that make up low and medium voltage electric grids is an essential part of any smart grid. Achieving this digital transformation for operating rural electric grids can bring previously isolated communities into the modern economy and have a huge impact on the standard of living. Electrification has been critical to increasing the standard of living in large parts of China and India. Evolving electric grids in rural areas are unlikely to have broadband or fiber optic communication technologies to enable the high-speed digital communications used to manage modern electric grids. In rural areas, the only practical solution to transmit the digital information required to keep electric power flowing reliably, safely, and cost effectively is wireless communications systems.
GSM (Global System for Mobile communication) is a digital mobile network widely used in the mobile phone carrier infrastructure in Europe and other parts of the world. GSM is also key to managing the electric grid in less developed rural areas. Using a variation of time division multiple access (TDMA) GSM is the most widely used of the three digital wireless telephony technologies, the other two being TDMA and code-division multiple access (CDMA). GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot. It operates at either the 900 megahertz (MHz) or 1,800 MHz frequency band.
GSM, together with other technologies, is part of the evolution of wireless mobile telecommunications that includes High-Speed Circuit-Switched Data (HSCSD), General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), and Universal Mobile Telecommunications Service (UMTS).
Many see the expanded use of GSM as a practical way to automate low and medium voltage systems in rural areas that lack wired communication networks. A family of GSM or IoT (Internet of Things) technology-based products is needed to create a smart grid control system that can automate low and medium voltage electric distribution systems using GSM. Although operation of SCADA systems on GSM networks have been discontinued in most markets where faster and more advanced networking is available to utilities, such as 5G connectivity. It remains a popular option in developing countries due to its wide availability and relative cost to fulfill short-term needs.
With the flexibility to operate over GSM, GPRS, or Internet networks, VP.Start makes it possible for utilities to monitor and control electric distribution systems from its proprietary SCADA system, through Smartphones, or Desktop PCs. Providing advanced controller functions (ADVC) and Pole Top Control Cubicle (PTCC) for protection relays are critical functions for remote monitoring and control of reclosers.
This capability can manage outages by restoring power to the affected area when an auxiliary supply is available. Using a combination of feeder, mid-point and tie reclosers retains protection, sectionalizes faults and minimizes the affected areas. This automation scheme can restore supply to customers in the shortest possible time.
By collecting data on power flow measurements and automating protective relays, reclosers and switchgear, utilities can improve the management of low and medium voltage distribution systems. These communications enable additional functions such as:
Metering of electric power has always been an essential part of managing electric grids both for billing purposes and operations. Smart meters and communications over GSM, GPRS, and internet-enabled networks can allow the utility to quickly identify outage situations and quickly act to restore power to customers. Measuring meter and recloser data across an electrical network can illustrate the situation of the electric power distribution system. This information allows identifying and correcting faults. It may be possible to reroute power remotely or isolate the outage to restore as many customers as possible, while line workers are dispatched to fix the physical issues like broken equipment. To ensure security, meter data should be encrypted before being communicated over GSM or GPRS, networks. Secure, timely, and accurate data is needed for use in smart controllers or when transferring data between devices and control systems.
To understand how an electric grid is operating and where power is flowing, metering the power is essential. Metering typically means measuring current, voltage, and power factor. From these measurements it is possible to compute the power quality. Electric power quality is the degree to which the voltage, frequency, and waveform of a power supply system conform to established specifications. Good power quality has a steady supply voltage that stays within the prescribed range, and has a frequency close to the rated value, and a smooth voltage waveform (ideally nearly a pure sine wave).
Wholesale electricity costs are paid for by market participants that purchase electricity from a wholesale market for either their own use, or because they are a supplier to retail consumers. In turn, suppliers and utilities provide electricity to retail consumers based on the retail market structures. Markets like this vary in different countries, but accurate and timely metering is an essential requirement for billing.
Metering is used for operational and billing purposes and the ability to log metering data allows an understanding of time of use (TOU) as the cost of power will vary during on peak and off-peak time periods or it may vary constantly throughout the day as most modern utilities are dynamically computing the wholesale market value of electricity, maybe once every hour. Metering can also help to determine the power lost in the distribution system. All systems lose some power due to resistive losses in lines and transformers, but additional losses can result from insulator failures and vegetation. Collecting metering data can be very useful to identify power losses.
An MMS System (Meter Management System) can help electric utilities better manage activities by optimizing accurate data collection at the right points remotely, securely, and promptly across the electrical grid. Automatic data collection & monitoring, alarms and notification, daily meter reporting, power analysis, peak load reporting and meter power data plotting make an MMS system more useful for grid operators.
Utilities often build out electrical distribution with above ground poles and wires. Line voltage can be adjusted by step down transformers when connecting to a substation. Sometimes transformers are pole or ground mounted and in cities they may be located in underground chambers. To provide safety, protective devices like circuit breakers or reclosers are installed in various branch circuits or in feeder lines at a substation. Various faults can occur due to car crashes, vegetation encroachment, insulator failures, or other faults. Without adequate automated and data-driven monitoring enabled by modern digital MMS or SCADA systems, the utility may only discover this fault when customers call to complain the power is out. In some cases, multiple branches may be involved in an outage. Utilities can better manage their grid when they can understand the situation through data. Data gathering and communications can enable alarming, control, GSM-Call-Control, real time trending, event logging, and device configuration, even from applications on mobile phones and tablets.
Utilities can benefit from bringing grid automation hardware and software together at a control center. With the collection of grid information, remote operators can determine the operational situation and evaluate the actions that will need to be taken for a wide range of failures. Situational awareness, automation strategies, and a knowledgeable grid operator coupled with the ability to manipulate protective relays, reclosers, and switchgear can provide many operational benefits to electric grid customers. Grid operators typically have a series of displays (like Single Line diagrams), equipment tables, detailed equipment configuration displays along with trending and alarming functions. The potential savings can include:
ARC has been following the remarkable electrification of China and India which has brought electric power to the whole countryside. This same trend is continuing in other parts of the world that are expanding electric power for the first time. The issues of financing and building out electric grids in rural areas of Africa, Asia and South America are significant. New capable low-cost communications systems that can monitor and control the switchgear on the distribution side of rural power networks are enabling grids to expand and allowing rural populations to prosper with the benefits that reliable electric power can provide.
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Keywords: Smart Grid, Control System, SCADA System, DRS (Distribution Remote System), DRC (Distributed Remote Control), Recloser, Switchgear, GSM (Global System for Mobile), ARC Advisory Group.