Structure of electric utility communications networks
Electric utility communications networks, as the network support and assurance systems, are responsible both for the communication of command and dispatch production instructions, and for handling administrative and automation information data. Due to the critical importance of electric power to any economy, power utility communications networks are usually private networks and, similar to the electrical grids, are nation-wide networks which are comprised of trunk line networks and local metro networks identical to any operator's national transmission network.
The trunk line transmission network mainly dispatches and manages large-capacity services between regional power utilities, requiring high reliability and relatively fewer network interface types. According to a country's size and administrative divisions, the trunk line networks can be further divided into national trunk lines and provincial trunk lines. The local metro networks are employed to transport information between regional electric power companies and the units directly under them, including electricity factories, electric power distribution stations, transformer stations/substations, and electric power sales and administration offices.
Features of electric utility communications services
Current electric power system services are divided into the following types according to their functions:
- Automation: Supervisory Control And Data Acquisition (SCADA) automatic dispatch, power metering system, integrated automation of transformer stations, production dispatch Management Information System (MIS), and technical support system.
- Protection: Fault recording system, power grid security stability control system, lightning detection system and relay protection system.
- Voice: Dispatch telephone service, administration telephone service and teleconference.
- Management and information: The MISs for power usage, finance, power supply projects, power production and security, human resources and operations, Office of Administration (OA) and geographical information systems (GIS).
- Video services: Videoconferencing, automatic monitoring for transformer stations.
The above power system communications services are provided by different service networks and will be transported as narrow band voice, narrow band low-speed data, broadband data, video and multimedia services.
- Voice and low-speed data services: These services are delivered by the 64K pulse code modulation (PCM) system and require transmission equipment to provide an E1 interface.
- Broadband data and multimedia services: Most of these are newly emerged utility communication services offered by an IP network. The IP network is comprised of routers and Ethernet switches and needs transmission interfaces such as FE/GE, POS, STM-N.
- Video services: They are mainly delivered by the videoconference system. The E1 or FE interface is required for the transmission network.
Different service networks can be carried over the same or different transmission networks. The PCM network is carried over the traditional SDH network; the IP-based network can be deployed through fibre direct connection, or carried over the traditional SDH or the multiservice transport platform (MSTP) network. The MSTP after years of applications supports a wide range of services and has become the preferred transmission method of electric power companies as it bears both the PCM and IP networks, avoiding overlapping investment and lowering overall costs. It is evident that the utility communication transport network can adapt to future needs with a layered, multiservice, and reliable architecture.
ZTE's electric utility communications solution
After years of research and product development, ZTE has successfully launched the Unitrans series of optical network products ranging from the large-capacity DWDM system (1600G) to the compact MSTP system (155M). These are now in service with over 130 operators in more than 70 countries. These products together with the unified network management solution can meet the requirements for layered networking and unified network management in utility communications networks (Fig.1). Electric power companies can make flexible choices based on their networks' capacity, interfaces and upgrade requirements.
Fig. 1 ZTE total power communication transmission network solution
ZTE offers a resilient, reconfigurable and reliable transport solution for the whole network.
Power utility communication transmission networks provide multiple services consisting of TDM services and the packet services. The packet services account for most of the new services and require different QoS levels. ZTE's MSTP-based resilient transport network can satisfy these requirements.
It adds Ethernet over SONET (EoS), resilient packet ring (RPR) and multiprotocol label switching (MPLS) technologies based on SDH to deliver both TDM and IP services and provide different QoS levels for IP services thus accommodating future services development. The EoS technology supports the L2 switching function and a variety of Ethernet services.
The RPR technology features 50ms carrier-class protection switching, topology discovery, rapid fairness algorithm, different levels of QoS, and a variety of networking typologies. The MPLS technology supports the Label Switched Path (LSP) with a control plane, 1+1 or 1:1 LSP protection, OAM management, an L2 VPN service, etc. ZTE's MSTP systems provide powerful data processing capabilities to fully meet the data transmission requirements of the power utilities.
The transmission network should be able to offer reconfigurability to enable future service diversification. ZTE's WDM and MSTP equipment take into account such requirements and capacity reconfiguration can be easily achieved by adding wavelengths and increasing the rate on single wavelengths. This means that the maximum capacities of, for example, the ZXWM M900 and ZXMP M800 are 160×10Gb/s and 800Gb/s respectively.
According to network requirements, the ZXMP M900 and ZXMP M800 can be configured as an optical terminal multiplexer (OTM), optical add-drop multiplexer (OADM), reconfigurable OADM or optical line amplifier (OLA), and can support point-to-point, chain, ring, ring and chain, and crossbar topologies.
By adopting a multi-ADM (MADM) design, ZTE's Unitrans series MSTP equipment can be flexibly configured as ADM, MADM, TM or REG network unit types to meet the requirements of multiple network topology modes, and support smooth upgrading from STM-1 to STM-64.
At the initial network construction stage, the network features relatively small scale with a few sites, simple topology and small bandwidth. As the network develops, the number of sites will become greater, the topology more complex, and the bandwidth more ample. Reconfigurable equipment makes it possible to implement effective network planning, ensure the sustainable development of the network, and offer phased investments to reduce the initial and overall construction costs.
Electric power grids have far reaching effects on the quality of life in all sectors of society and are crucial to a nation's development, thus they require high security and availability. ZTE can provide highly reliable network solutions. ZTE's optical transmission systems provide equipment-level protection with hardware redundant backups. For example, the ZXMP S385 adopts 1+1 hot backup for the cross-connect clock board and NCP, and 1:N protection for electrical tributary interface boards.
In terms of network-level protection, ZTE optical transmission equipment can implement all network protection modes adopted by ITU-T. It is worth noting that the ZXMP M800 is the only WDM equipment in the industry capable of offering six protection modes consisting of 2-fibre bidirectional path shared protection, 1+1 path protection, 2-fibre bidirectional multiplex section shared protection ring, subnetwork connection protection, 1:N OTU protection, 1+1 multiplex section protection.
Fig. 2 ZESCO抯 national optical transmission backbone network
ZTE was awarded a turnkey contract to install a national backbone optical network for Zambia's power utility Zesco this year. ZTE introduced Optical Fibre Composite Overhead Ground Wire (OPGW) technology and installed OPGW cables on Zesco's power lines, utilising existing resources such as the nation-wide electrical power towers.
The 1200-km optical transmission line covers Zambia's richest regions including the capital, Lusaka, Copperbelt Province, Central Province, Northern Province and Southern Province. The network is based on ZXMP S385 MSTP equipment that features unique logic sub-network protection function, smooth upgrade to the 10G system and provision of E1 and FE services, thus building an integrated multiservice transport platform for Zesco.
Communications is integral to modern electrical power management. ZTE as a world leading telecoms supplier can provide a resilient, reconfigurable and reliable transport solution to meet the requirements of utility communications services. ZTE's comprehensive range of optical products for all kinds of networks ensures that its solution can be customised for any utility operator and help them to effectively supervise and control power system operations.