Michel Kibkalo, Areva Transmission & Distribution, France

Romania’s transmission system operator, Transelectrica is installing the latest in power telecommunications technology to aid the flow of communication in its network.

Running a high voltage electricity grid used to be all about maintaining equipment, and was never an insignificant task, but since market deregulation, transmission system operators have had to contend with more than just supplying power.

Figure 1. Telecom cubicles at site (SDH equipment)
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As such, a precursor to any market deregulation is the necessity to have a modern, up-to-date system capable of managing the flows of electricity, money and information.

Areva T&D, which until recently was the Transmission & Distribution Sector of Alstom, has moved with the market and specialised in all three flows. The company is well-known for its transmission and distribution products, systems and services offering, and is the market leader in energy software for both energy management and market systems, but its expertise also extends to the telecommunications side of information flow.

Telecommunications are an essential part of a power network, primarily because of the flow of real-time vital information they carry about the condition and operation of the network. For example, protection equipment needed to trigger the shutdown of lines in case of accidents or faults uses the telecoms network that runs alongside the power network to transmit and receive vital signals. As monitoring and control technology advances, the greater the utilities’ need for reliable, independent and powerful telecommunications networks.

Figure 2. Telecom cubicle at site (access equipment)
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At the end of December 2002, T&D won a contract to create a complete telecommunications network for the Romanian national transmission and system operator, Transelectrica, established in 2000.

Romania, along with many other east European countries, is structuring its electricity industry along the lines of many of its west European counterparts, i.e. ‘unbundling’ into separate generation, transmission and distribution companies.

Transelectrica is charged with developing the Romanian high voltage network while preserving its operational stability and safety. It decided to totally revamp its telecommunications system because of three factors: the current system was aging and out-of-date; the demand for power was increasing; and financial help was available to carry out the upgrade from the European Bank of Reconstruction and Development.

The contract with T&D is for a complete telecommunications network for the country, based on the use of fibre optic cables, which will be supplied and installed by other contractors.

Areva T&D is constructing a network that will allow the utility to transmit and receive vital information between substations, five regional electricity control centres and the national control centre in Bucharest. Transelectrica’s headquarters and all its transmission subsidiaries will also be connected to the system, making a total of 65 sites in all, and 125 access points connecting to the digital backbone. The network will be ‘fully meshed’, allowing direct communication between all parts of the system.

Operational services

The services that the communication network will provide can be classified into four groups with different requirements in terms of network availability, fault tolerance and time constraints.

The main services required from a power company communication network correspond to the specific real-time applications related to the operation of the power system. A high voltage electricity network needs to exchange information quickly between substations, in case of incidents or failure, in order to protect the system. Such protection schemes for high voltage lines or power network components require end-to-end communication channels with high quality information delivered as quickly as possible via permanently available channels. This applies to both differential protection and teleprotection signalling schemes.

To allow the network operators to react quickly in case of emergencies, the main electrical grid stations are being equipped with hotline telephone connections to the territorial and national dispatch centres (TDC and NDC) and to the regional headquarters (HQR). A number of additional hotline telephone connections are also needed between the control centres and the headquarters.

Modern control systems need to exchange real-time data between the various computers in the control centres and the remote terminal units (RTUs) in the substations. The interconnection of regional and national control centre local area networks (LANs) generate a more sporadic and time-insensitive traffic with much larger data volumes to be exchanged in each transaction. Areva T&D is also providing a communication environment for operational LAN interconnections.

T&D is also installing a number of video connections, which allow Transelectrica to monitor access to certain sites and survey critical equipment from the regional headquarters. In addition to the hotline telephone systems described above, each grid substation requires around 30 switched telephone extensions with network-wide call connectivity and modern voice network facilities. The voice network connectivity must cover not only the grid substations and the control centres, but also the different administrative sites of the utility. Logistics, maintenance offices, planning and engineering departments need to make frequent communications between the operational and the corporate world.

External services

External users, who may be integrated into the network in the future, would generally require voice and data interconnections between their sites dispersed across the country.

T&D’s attractiveness in the telecommunications field derives from its thorough knowledge of the requirements of power system operators. Its expertise is linked not only to its thorough knowledge of the transmission industry but also to its ability to take the best equipment available on the market, work it into a complete network design and fully integrate it on site.

So how can the company be sure that all these different pieces of equipment will work together out in the field? For the Romania project, Transelectrica asked T&D to create a replica system at T&D’s factory at Massy, Paris, in order to test the interconnectivity of the various equipment and the efficiency of the overall design.

This system, called the Reference Factory System (RFS), was assembled at Massy and comprised three interconnected subsystems: a telephone network, an access layer and a transmission network.

The three subsystems were equipped with management platforms, allowing T&D to test both the functionality of the subsystems themselves and the interactions between the different systems. After substantial and thorough testing, Transelectrica granted a system acceptance certificate and Areva T&D began putting the system in place in Romania.

The telecoms system uses the latest Dense Wave Digital Multiplexing (DWDM) and SDH (Synchronous Digital Hierarchy) technologies. These technologies allow a considerable amount of data to be transmitted. The transmission network uses optical fibres to connect 65 sites through DWDM/SDH technologies at 2.5 Gbps covering the whole territory of Romania, and including Transelectrica’s national control centre, five territorial control centres, nine regional headquarters and 125 different access points are connected to this digital backbone.

In addition, there is an ethernet LAN interconnection for 15 sites (national and regional control centres and headquarters) at 2 Mbps including all LAN switches and converters. There is also a multi-service ATM network over 15 sites (national and regional control centres and headquarters) operating at 155 Mbps.

Figure 3. Entrance of the Darste 400 kV substation
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The national telephone network transit core is composed of eight ‘fully meshed’ large exchanges and 48 new telephone exchanges for on-grid stations and control centres. As the network is ‘fully meshed’, each exchange can communicate directly with another without having to go through a central exchange. T&D will also upgrade and integrate 12 large existing exchanges of different types.

Areva T&D is also installing an automatic cable fault localisation system. This system reports any cable faults on the network to a central facility, and is accurate to within 5 m.

This architecture has several main advantages. The use of fibre optic cables and modern telecommunications technologies gives both secure communications and high performance levels.

The DWDM technology used means that Transelectrica has plently of bandwidth to expand the use of its telecom network at some time in the future to cover new needs and new users, either internal or external.

SDH technology gives reliable communications, due to protection mechanisms within the SDH layer, which guarantee network resilience. The network management systems used give a better quality of service for end-users, avoiding loss of service and reducing downtime in case of incident.

The project is due to finish on time at the end of this year and Transelectrica will have one of the most advanced power telecommunications systems of any utility anywhere in the world.