Major companies using their own regeneration capacities face the problem of complex automation of different control systems at regeneration equipment used. Lack of a unified management system at Multi-unit Energy Centre leads to continuous operation of generation equipment at partial loads. Caused wear of generation equipment reduces interval between maintenance. Ultimately, it leads to an increase in the cost of a kilowatt-hour produced, and, hence, it reduces the economic effect of the autonomous generation site. ROLT energy service (ROLT group) has the know-how to integrate individual generator sets into a single automated power complex. Upgrade of computer-aided process control made by ROLT energy service for JSC«Novosibirskneftegaz», provided significant saving by optimizing the process of power generation and distribution, the influence of the "human factor" reduced, the cost of kWh minimized by increasing the intervals between repairs and reduction of specific fuel consumption.
Upper Tarskoye oil production field (VTNM) located in the north of Novosibirsk region, in the North district, is considered the major oil field in the region. Industrial operation is lead by JSC "Novosibirskneftegaz" ("NNG").
Power supply centre was controlled practically manually. To start and stop diesel and gas powered electrical generators the plant personnel performed all the necessary steps directly on the control panel of the unit, receiving commands from the controller and using radio or telephone communication. During emergency stop of one of the plants (particularly —gas turbine) all the overloaded generators were consistently turned off. It took up to eight hours to restore regeneration fund with access to normal operation. All the time the oil field was not working, production stopped. Downtime led to a significant reduction in oil production and, consequently, to a decrease in profitability.
In 2013, at the background of unstable operation of energy centre a long-term service contract was concluded between JSC "Novosibirskneftegaz" (NNG) and ROLT energy service. The subject of the contract was services, including round the clock operation and maintenance of power equipment and electrical networks, repair and overhaul for uninterrupted power supply of industrial and administrative facilities of VTNM and other fields developed by the company.
ROLT energy service management, by replacing an energy service company from Nizhnevartovsk, defined the modernization goal of computer-aided process control power centre as of first priority. Actually, the existing control system had low reliability and was inconvenient for operation personnel. Beside, different control panels did not interact between each other. The policy that limits access to control system for operational personnel, accepted by major generation equipment producers, did not allow to produce the required adjustments and changes to implement mutual automatic unit operation.
Upgrade of computer-aided process control of power supply centre at Upper Tarskoye oil field was divided into three stages:
- replacement of computer-aided process control on gas reciprocating and diesel generator units;
- control and management arrangement for generator switches and load switches in indoor switchgear cells;
- unification of all generator units and indoor switchgear in a single computer-aided process control.
ROLT energy service started implementation of the project in March 2014. All works were conducted using a schedule approved by NNG without brakes in power supply of the production field and were finished in the middle of April 2014. Within several weeks ROLT energy service tested control system operation in different modes, modelling different non-standards situations. Complex tests were conducted successfully and at the beginning of summer 2014 Upper Tarskoye oil production field power centre is controlled using single computer-aided process control.
Control system operation logic included optimization of mutual work of generation equipment in terms of fuel flow rate and reliability. Actually, gas reciprocating power units have high electrical efficiency, but adversely react to load discharge/rise. Also they are not operable under load of less than 50% of nominal value. Diesel power stations, in turn, have better dynamic characteristics, but they have limited fuel capacity. Besides, the cost of diesel fuel with consideration of logistical expenditures is relatively high. Gas turbine stations easily make load discharge/rise and can work under load close to zero, but have lower electrical efficiency than gas reciprocating units. Taking into account the distinctive features of different types of equipment, generators were divided into groups according to their functional purpose:
- Main group. Gas reciprocating power units work basically in the main mode with existing stable load with ratio from 50% to 80%.
- Reserve group. Gas turbine plants are loaded in 50%, creating capacity reserve for automatic load discharge/rise.
- Emergency group. Diesel power units are used as emergency sources, ready to be launched at any time and take load to avoid stop of the whole power supply centre.
For that all gas reciprocating and diesel generator plants not depending on engine manufacturer has controllers IS-NT-BB produced by ComAp. The replacement allowed to unite generators different by type and capacity based on internal combustion engine in a single control and monitoring system. All the controllers are connected between each other via single CAN-bus. Due to length of information lines the data transmission bus at long areas was implemented with use of optical fibre cable and application CAN-bus repeaters HD67181.
Each controller sees characteristics of other stations, included into single control system, which allows to apply the following functions:
- Аutomatic start of the required number of gas reciprocating generator units;
- Capacity control (start and stop depend on load);
- Manual or automatic priority adjustment depending on working hours or load requirements (most effective adjustment);
- Separation of active and reactive power;
- Gradual load and discharge of gas reciprocating and diesel generator units;
- Distribution of generator units into groups "Main – Reserve – Emergency".
Data collection and control signal connection in indoor cells allow to control the connected load urgently and check the output capacity from the generating units. All the consumers are divided into 5 categories according to importance to start and 5 categories to stop in emergency in accordance with degree the consumer influences the production process. Under emergency situations the operation features of computer-aided process control envisage consecutive consumer switch off in accordance with preset category priority in order to reduce the common load. The approach provides practically zero possibility that all generating units stop due to overload.
Processing of all information received at the upper level from reciprocating units, indoor switchgear and automatic control of gas reciprocating units is made on industrial computers Automation PC 910, equipped with high technology processors Intel® Core™ i-series and controller B&R Х20System with input-output modules.
The system allowed to unite control and monitoring of the main values in the single dispatching system. Power centre control unit consists of four working places: Automated working station of dispatch control head, automated working station of generation operator, automated working station of a gas-turbine thermal power plant operator, automated working station of gas reciprocating power plant operator. Computer-aided process control admits connection of several remote working places to control power centre operation without a possibility of control.
Computer-aided process control receives input data from detectors, alarms, end switches of electrical units, local computer-aided process controls and operator work stations. It also processes the information received by preset algorithms, forms control signals to the actuators, records control information about the state of the process equipment.
Mnemocircuit of station capacity complex regulation reflect main information in the whole complex, such as: total capacity, capacity of gas reciprocating power plant-gas-turbine thermal power plant-diesel power station, power, graphics, control button reserve. Interface visualizes the information on power output, load and reserve of basic, additional and reserve capacity in a form convenient for analysis. Value change in time may be displayed as a diagram.
Main function of control system at power centre Upper Tarskoye oil field JSC "NNG":
- Remote control of a gas turbine plant, gas reciprocating power unit, diesel power plant.
- Operating station feature control.
- Preparation for start of required number of stations, or stop.
- Hot reserve support.
- Electronic history log formation.
- Displaying alarms and faults on operator screen.
- Operating value log formation.
- Remote value change.
ROLT energy service engineers managed to unite generator units in a single automated power complex. It gave a possibility not only to centralize control, management and monitoring for several work stations, but provided further data transmission in real time mode.
According to general director of ROLT energy service Vladimir Litvinov, the successful modernization of power supply control system with use of innovative technical solutions allowed to completely automate power generating equipment at Upper Tarskoye production field of JSC "NNG". "We managed to switch all diesel power stations into "hot reserve" mode and reduce discharge of diesel fuel practically to zero. — Vladimir Litvinov, general director of ROLT energy service is saying. — Using new control system, JSC "NNG" reached significant saving by optimizing the process of power generation and distribution, the influence of the "human factor" reduced, the cost of kWh minimized by increasing the intervals between repairs and reduction of specific fuel consumption.
Chief electrical supervisor JSC "Novosibirskneftegaz" А.V. Fedoseev marked: "Since computer-aided process control of power supply has been commissioned the consumption of diesel fuel reduced in dozens of times. Thus, in September 2013 diesel power stations worked in 1101 hour and consumed 145 818 kg of fuel, and for the same period in 2014, after only 66 hours, consumed 7570 kg of fuel. Besides, number of emergency shutoff reduced in 67% (from 106 to 36 outages). I would like to remark that the time to restore production field power supply during emergency outage has significantly decreased – from 8 hours to 2 hours".
«The biggest advantage of our system is its openness and operability, — adds Vladimir Litvinov. Indeed, the computer-aided process control based on the software with open source, which means that it allows rapid setting when you change the hardware configuration. In addition, open-source software, if necessary, allows to change algorithms in all energy centre or its individual components at minimal costs. Modular structure of computer-aided process control makes it possible to increase freely the total capacity of the energy complex through the integration of new generating plants in the currently running system.
«From the beginning of cooperation with the NNG we set ourselves the task of providing efficient and reliable power supply at entrusted site. Since we explicitly follow that plan», — Vladimir sums up.