National electricity system with backbone parts including electric transmission network and distribution, is one of the most important infrastructure systems of national economy. Vietnamese electric network has experienced many stages of formation and development with various brands of device, from those of XoViet Union to European and North America. The economic development requires higher value of power quality together with new services. It forces the electricity industry to modernize, synchronize equipments, improve operational efficiency, ensure the reliability and safety of supplying electricity.
On 26/12/2001, the first integrated substation project in Vietnam has been accepted and set into operation at Substation of 220 kV Vinh Long 2, starting the process of dramatically changing in the operation of electrical system of the Vietnam Electricity group (EVN). After nearly 10 years of applying new technology- protection and control substation integrated system which based on the actual exploitation and operation of the system @ Station has been operating at about 30 substations on electric transmission grid of the Corporation, National transmission. Since we could see more clearly the undeniable benefits of these systems.
Investment cost of the whole life-cycle project
Automation station is the replacement of protection control system and electromechanic, monitor system and communication equipments in the station by microprocessor relays, other digitalization devices called generally IED (Intelligent Electronic Devices) and integrated computer systems. Substation automation relates to application of digital information network in the station, from one station to others and to the application control centers. Therefore, the initial investment costs may be higher but the operation and maintenance costs, upgrade costs and especially minimizing incidental costs, time to fix in the old station greatly reduced. Consequently, for the whole life cycle of project, can easily recognise the economic benefits that the substation automation system brings in.
In @Station system, devices of protecting relay, controlling and gathering data are set in the controlling cabinet of outdoor protection or cabinets placed in containers. These cabinets are connected to the optical LAN network and the computer system in the central control room. Interlock signal is transmitted over LAN network according to IEC-61850 protocol. Therefore, the amount of cable decreased to 50-70% in comparison with traditional type, impressive amount of investment cost.
Integrated system is also available with the ability to connect remote supervising center, regulating center of power system according to common protocols such as IEC-60870-5-101, RP570. This allows ignoring the requirements of connecting RTU system to these centers.
Cost of risk
Optical LAN network of integrated system replaced largely copper cables in the substation yard, minimizing the risk of accidents caused by electric cables as happened in old system.
Integrated system significantly reduces the intermediate devices, devices with particular functions and are flexible in changing the requirements of continuous operation, maintenance and minimization of handling problems time with the active support of integrated systems and intelligent electronic devices. At the same time, the IED is always supervised and the system will provide warnings concerning the working status of these devices as soon as occurring abnormality. Other network devices with the ability to "plug and play" helps minimizing repair time instead.
These show that the benefits from reduction cost of risk in comparison with the traditional stations.
Operation and maintenance cost
Station automation provides outstanding ability in monitoring operation of system, collecting automatic performance data, producing reports and storing data to make the input for new facilities and applications. Thus, important equipments such as transformers, cutting machine, ... may be maintained at the right time rather than periodically checked as before. Basing on full and accurate information stored and analyzed in the process of operation, devices can be only replaced, station can be only expanded when actually necessary without wasteful investment.
Integrated substation system was built according to the technical process of electrical safety of substation, which issued by Vietnam Electricity Corporation. Specifically:
- Operation interface has friendly design, enables operators to easily use and monitor the performance of the station.
- Dual LAN network system, with equal structure and Mimic control system in outdoor cabinets, allows the operator to control devices even when the whole computer system gets into troubles. This feature is in the general design principle: "Any trouble in element does not allowed to disrupt the operation of other elements in the system."
- The system offers many convenient applications in operating and troubleshooting, such as automatically recognizing incidents which have integrated time and GPS satellite clocks, calculating the temperature in the transformer on real time, accessing measurement parameters by the SMS system etc. ..
Upgrading and expansion cost
As mentioned above, upgrading and expansion costs are reduced as the result of investment right time, right place. Moreover, open characteristics of the system allow the integration of multiple devices from different companies as well as allow the users to build their own applications suiting each individual station. The system is built in accordance with common standards in the world, not only reduce the monopoly of suppling goods but also create big advantages for the users on upgrading and expanding systems in the future.
Improve the efficiency of system operation
Beside warning function, measuring direct supervision of equipment and operating parameters in the traditional stations, the elements of the integrated system, which is supervised continuously operating information is stored automatically, warnings are stored with accurate information on time, shifts, faulty equipments,... ensure that the operation achieved the best performance in any situation.
Reports are stored and will be printed according to the requirement of system operation to keep information accurate in both parameter and time.
The past data of the system is very useful for the investigation and analyzing troubles, analysing the system stability and fulfill the demand on training, improving professional skills for relevant subjects.
The utility of calculating real time of systems or facilities developed by the users open a great opportunity to improve operational efficiency upon request of users as well as new requirements in the future.
Anticipating trend of development
The application of integrated substation system is the inevitable trend in the era of information technology. Beside the fulfillment of requirements of easily upgrading and expanding the system, integrated system is also the starting point for the digitization and data storage of power system, gradually replacing the concept of operating system according to practical experience.
Power system data in real time which are stored and exploited mainly on demand of consumers is an integrated part in construction and regulating forming power market.
Integrated substation system is the first step in constructing "Smart Grid", a new concept that has become the inevitable trend in the improvement of power systems worldwide.