The reliability of the electricity supply is determined by the producing and delivering tools, equipment, operation control system and the operating staff together. The single system of state-of-art and reliable equipment, adequate organisation, physical and data protection, the exact definition of responsibilities and well-educated operating staff committed to energetics is needed for the uninterrupted operation. All these are available at MAVIR.
The Transmission System Operator is responsible that the consumer shall receive the electricity in adequate quality and with safety, therefore it has to ensure always enough reserve capacity in the transmission network and reserve power in the power plants.
The safety of the delivery is increased that both the 220-400 kV transmission network and 120 kV distribution network is meshed. It means that there is a multidirectional connection between the individual network nodes, thus the tripping of one element does not cause a massive disturbance in the electricity supply (topological safety). The networks with different voltage levels mean natural reserves to each other, thus e.g. in case of tripping a 400 kV line, a part of the flowing power is loaded over to the other 400 kV lines and a part to the 120 kV network.
The networks of the individual countries operate interconnected and create system association. It increases not only the topological, but the production safety as well. In case of disturbances in power plants, the interconnected power systems participate in the replacement of the power lost. The interconnection covers every country in Western and Central Europe and means the cooperation of a power system of more than 300,000 MW (in comparison, the peak power of the Hungarian power system did not amount to 6000 MW last year).
Due to the physics of energy supply, the connection between the countries is extremely close and should be a shortage in any system, each energy systems in synchronous operation will participate in its replacement. The automatic emergency help ensures that the consumer does not experience the equipment breakdown occurred in any of the local power plants, independently of the extent of the breakdown. This power in the form of unplanned import cannot be used for unlimited time. There is a regulation that every power system has to restore the power balance within 15 minutes. This regulation ensures that the extensive European system is continuously prepared to give emergency help to its members. The most severe consequence for the infringement of the regulation that the connection is terminated with the system defaulting against regulation. There has not been such precedence in Hungary, although we had to curtail the consumption by cca. 300 MW in January, 2003.
The dispersed structure of the power system, its multi-meshed topology and the international cooperation ensures a supply with high safety. Supply failures occur or may occur located in small areas, for a small group of consumers and for a short time. The practice shows that the number of disturbances is very few where the consumer’s interruption exceeds 50 MWh classified as “to be reported” in the Grid Code, which defines the operation of the electricity industry.
Although the above facts suggest that safety of supply can be planned and supervised, the disturbances are much more “inventive” than to simplify the work of the transmission system operator. We must be prepared to deal with unplanned situation (See: What to do in trouble?). We collected some examples from the scarce cases when the disturbance in the electricity system was realised also by the consumer. There are weekly and daily events which are to be dealt with not less attention than the troubleshooting of the mentioned disturbances and to decrease their consequences, but they are known by only a narrow circle of owners and operators. That’s correct, not the difficulty, but the result of the work shall convince the consumer, i.e. if the disturbance remains unrecognisable.
Best way is to prevent. We said nothing new, but we should like to describe what it means for MAVIR. Safety must be grounded during system planning. At this time, we are preparing for expected events saving enough reserves in power plants and on the network.
There are events which may never occur, but are not to be excluded. There are life-boats on every ship and passengers are shown how to put the life jacket on, however, nobody believes that the ship may sink.
A governmental decree orders for MAVIR how to be prepared for incidents severely detrimental to the operation of the power system. Such a preparation is not unknown for the transmission system operator, there were always environmental damage protection plans supposing disturbances of different magnitude. There is a scenario even for the case when only the candles are lighting in the country, all power plants are stopped and every international line is disconnected. We have power plants that could start even in this case and the other power plants can be started with their assistance, thus the consumers could be gradually supplied.
In compliance with the governmental decree, MAVIR established and operates a body with a fairly frightful name, the Crisis Working Committee to prevent and to manage the critical situations. The Head of this Committee is the Chairman and CEO of MAVIR Rt. Its members are the power plants, two-two representatives nominated by distribution companies and electricity traders resp., the Hungarian Power Companies Ltd. as public utility wholesaler, Paks Nuclear Power Plant as prominent producer, one-one member is given from Chief Directorate of Catastrophe Prevention for Ministry of Interior Affairs, Ministry of Environment Protection and Water Management, Ministry of Economics and Transport and the Hungarian Energy Office.
The basic task of the Crisis Working Committee is the preparation of measures to be taken prior to and during the emergency. It means inter alia to give opinion on the regulations of electricity supply, to monitor the fuel stocks and to prepare the load shedding sequences and information systems.
The Working Committee set up on 1st April, 2003 had immediately a task: the constant failure of second reactor block in Paks Nuclear Power Plant necessitated the revision the maintenance plans for power plants and networks and the replacement of the missing electricity. The electricity system is preparing with special care for the winter that a cold snap similar to last year shall not cause difficulties in the supply. Under the approval of the Crisis Working Committee, the transmission system operator operates an operative discussion to co-ordinate the preparation which enables the representatives of Paks Nuclear Power Plant, Hungarian Energy Office, Ministry of Economics and Transport, MOL, Hungarian Power Companies Ltd. and MAVIR to evaluate, upon the most up-to-date information, the situation bi-weekly and to make proposals to solve the problems.
Should be the most accurate preparation, trouble could not be always avoided. If it even occurs, we have to do our best that it shall cause as less damage as possible.
Our goal is to maintain the operability and the international connections at any price. Actions to achieve this goal are not always painless.
Usually the serious disturbances turn over the power balance of the electricity system. The failure of a great or 2-3 small blocks does not mean an incident recognizable also for the consumer, we may or even must take it account. To have sufficient reserves for their fast replacement is included in the system operation. The worry begins when the missing power due to a disturbance considerably exceeds the volume of the reasonable reserves. We could operate much more reserves, but it would a high burden on the consumer’s purse.
If a power plant block is tripped, there are two options for restoring the power balance: to increase the production or to decrease the consumption. The first was discussed right now, this is the general practice. The second option, to decrease the consumption would be displeasing to the consumers disconnected, therefore it must be avoided where possible. If it is still the only available tool, we do it under severe rules according to the effective ministerial decrees. We always disconnect solely the absolutely necessary, fewest consumers. For this goal, we have pre-prepared packages and we know of each how much MW of consumers it contains. Only those consumers may be included in these packages – officially named: load shedding stages – who are not jeopardised with life danger or significant material damage by the disconnection. A hospital or a mine must not be disconnected, also a hazardous chemical work, the water works or subway must not be included into the interruptible consumers and we endeavour that the curtailment shall effect the broad public as later as possible. There are many factories, offices and household consumers where the disconnection is naturally displeasing, but it does not mean irreversible consequences. The existence of several load shedding stages give opportunity not to disconnect the same consumers for a long time, if necessary, they could be changed. We have never needed this.
Since the beginning of 1990s, the transmission system operator has not ordered load shedding, but lately two events have occurred, where we had to employ this tool to prevent the more severe consequences.
On June 2, 2002, at the 400kV substation in Paks (out and independently of the power plant) there was a disturbance and the Dispatcher Service had to deal with two problems: to restore the power balance of the Hungarian Electricity System and to ensure that the voltage considerably lowered in South Transdanubian region shall not lead to the expansion of the disturbance.
Fortunately, the balance could be restored fast and stably, but the voltage was the crucial issue. The injection to the 120 kV network was terminated by breaking the 400 kV bus bars at Paks substation. Since the servicemen were working on the other two 120 kV lines in the area and the third one suffered a short circuit in some minutes later and therefore it automatically disconnected, the appliances showed 85-90 kV instead of 120 kV in South Transdanubia. Pécs Power Plant did everything possible to mitigate the voltage dip, but a 60 MW block is not able to do miracles. The machine overloaded and disconnected. The transformers in Dunaújváros were operating on almost one and a half more of their nominal power. This state cannot be maintained in the heat wave for a long time, the overheating and disconnection of the transformers could have caused the interruption of entire South Transdanubia. Only the local decrease of the consumption could offer a solution in the situation. Therefore, the National Dispatcher Service ordered a 50 MW load shedding in the region. The actually disconnected 43 MW at the well-selected place proved enough until the reconnection of Paks bus bar, the network in Sándorfalva and the two 400/120 kV transformers in Paks.
The disturbance on 13 January, 2003 worn other characters when we had a consumption curtailment due to an irregularity successively occurred in several power plants.
Caused by the extraordinary cold, the fuel of Mátra Power Plant was frozen up. Two generators of Dunamenti Power Plant also stopped, Csepel Power Plant was not able to start. Complying with the international regulations, the Hungarian Electricity System is able to replace even the greatest power plant block, i.e. 460 MW lost power within fifteen minutes. But it all proved insufficient, the missing power was cca. three times more than the volume of reserves ordered by the regulation.
The value of the unplanned power flowing from the international network continuously exceeded, between 5.24 a.m. and 8.00 a.m., the maximum 100 MW defined by the European System Association. The peak value was reached at 6.22 a.m. In this situation, the ordination of load shedding was the only tool applicable by the dispatchers. Without this, we would not have been able to improve the balance of production and consumption and to decrease the unintended energy input from the international electricity system. We disconnected appr. 300 MW consumption. The load shedding was ended a few minutes after 8.00 a.m. when we could replace the shortage partially from local and partially from import sources.
The described facts are evident, but it is worth summarising:
Since electricity supply is via a single, common network, though with several players, an impartial transmission system operator is needed who is independent of other participants and whose single interest is to be responsible for the entire electricity system ensuring the same rights for every player of the service.
MAVIR is the organisation who sees the electricity system and its operation from production, via delivery, until the consumption, from planning until realisation. MAVIR has all the technical facilities needed for the operation of the system and by these means, all the data and information are in its possession. Under its operation licence granted by the Hungarian Energy Office, MAVIR is not only able and ready, but also entitled to interfere into the course of electricity supply. The goal of its activity, that You, the Consumer – should be a market participant or a part of public utility – shall feel only: electricity – naturally available.