Comparison of national standards requirements established to basic electrical energy quality

indicesAlexander Smirnov, Natalia Borisenkova

A. Smirnov, N. Borisenkova are with the Saint-Petersburg State University of Ways of Communications, Saint-Petersburg, Russia (e-mail: avgustovskaya@mail.ru )

Abstract – Modern power industry is advancing towards national and regional electrical power systems intensive consolidation. The systems often use different standards in electrical energy quality field.

Main line of modern world power engineering development is to create powerful energy pools, covering enormous areas with energy supplies and productive capacities distributed very unevenly. Synchronous networks operation has to provide appropriate quality of the electrical energy. Electric power quality maintenance is not only the most important condition of power network normal operation, but also the condition of modern electric power market operation.

The UES/UPS 13109-97 standard and international EN50160 standard, which is in force within UCTE and NORDEL systems, have several distinctions. Requirements to frequency and voltage levels in high voltage systems and general-purpose systems differ in different countries. The specified parameters are of a great importance for networks integration. Therefore, calculation methods and extreme intervals for the parameters need to be unified.

Index Terms – energy associations, power quality, standards in electrical energy quality field

I. ITRODUCTION

Modern power industry is advancing towards national and regional electrical power systems intensive consolidation. The systems often use different standards in electrical energy quality field. Indicated situation demands to analyze and to unify appropriate normative documents.

II. INTERNATIONAL NETWORKS INTEGRATION

Main line of modern world power engineering development is to create powerful energy pools (EP), covering enormous areas with energy supplies and productive capacities distributed very unevenly. The EP creation is accompanied by generating capacity structures and backbone networks complication. Supervisory and emergency control systems became substantially complicated as well. At the same time, development of powerful energy associations provides considerable cost efficiency and enhances consumer power service reliability.

There are three large energy associations in Europe today:

- Western synchronous area (UCTE) includes power networks of France, Spain, Portugal, Germany, Austria, Italy, Belgium, Western Denmark, Switzerland, Luxemburg, Republic of Slovenia, Republic of Croatia, Poland, Slovakia, Hungary (1st area), Greece, Bosnia, Herzegovina, Macedonia, Serbia and Montenegro, Albania, Bulgaria and Romania (2nd area). Great Britain power networks are connected to UCTE via submerged cable lying under English Channel. Western Ukraine power system operates in parallel to UCTE from July 1 the year 2002 (so called Byrshtynsky island).

- Northern synchronous system (NORDEL) consolidates Northern Europe countries (Sweden, Norway, Denmark, Finland and Iceland). At that, western (continental) part of Denmark power system operates in parallel to UCTE, and the eastern one – to NORDEL. Iceland power system operates autonomous;

- Eastern synchronous area (UES/UPS) consolidates Russian power grid, Commonwealth of Independent States network systems (excluding Armenia and Turkmenia systems, which operates in parallel to Iran power system) and Baltic integrated power network (including Estonia, Latvia and Lithuania systems).

The energy associations developed almost independently from each other. The associations embrace multifarious territories and have manifold interior interaction management and different control ways.

Main factors providing enhancing efficiency of large EA establishment are the following:

- reduction of total power stations installed capacity, necessary to cover EP peak load in tote. That can be achieved by the systems load diagrams combination;

-EP emergency power reserve reduction due to mutual assistance of the systems operating in parallel;

- repairing power reserve reduction, that lightens capital repair;

- electric power stations agglomeration and plant unit capacity enhancing, that allows to decrease 1 kW cost of new generating capacity and to increase working efficiency at electric power stations development and operation;

- reliability, electric power supply quality and power quality enhancing, owing to frequency and voltage higher stability maintenance;

- system interconnection allowing to solve integrated hydropower engineering problems more effectively. That is based on large coordinated hydroelectric system establishment, providing additional fuel saving, especially abounding in water years;

- diminution of difficulties, caused by unscheduled capacity and individual system electric power balances deviation.

Power systems interconnection in parallel and large EP establishment provides substantial economic efficiency. Generally, frequency and active power flow are regulated jointly in EP via basic tie lines. Several European countries have different frequency maintenance limits (in nominal conditions), Hz:

- in England and Northern Ireland - 49.5 ÷ 50.5- in Poland - 49.5 ÷ 50.2- in Ireland, Germany and Hungary - 49.8 ÷ 50.2- in Sweden and Norway - 49.9 ÷ 50.1- in Russia - 49.8 ÷ 50.2

Moreover, additional requirements are established in guidelines to electric power stations and appropriate equipment operation on beyond frequency conditions.

Voltage levels are standardized as well. Usually, under normal operation conditions network voltage is maintained close to the rated value. Permissible voltage deviation is ± 5% in the most countries and it equals to ± 10% in several others.

Voltage maintenance standards currently in force at power networks in European countries are listed in Table I [1].

TABLE IVOLTAGE MAINTENANCE STANDARDS CURRENTLY IN

FORCE AT POWER NETWORKS OF EUROPEAN COUNTRIES

Voltage level, kV

CountryPermissible continuous voltage deviation level,

%

400

England, Wales, Poland

-10 %, +5 %

Hungary ± 5%

Ireland -7.5%, +2.5 %

Norway -2.5 %, +5 %

Germanyis stated by electric

power company independently

Russia (330 kV) ± 10%

220

Northern Ireland - 4.5 %, 9%

Germany +10 %

Hungary -14 %, +11 %

Poland ± 10%

Russia ± 5 %

110

Poland, Northern Ireland

± 10 %

Ireland - 4.5 %, 9 %

Russia ± 5 %

In the beginning of the year 2002, Electric Power Council of Commonwealth of Independent States (EPC CIS) has expressed an interest in simultaneous integration of UES/UPS and UCTE systems.

At present time, there is no any power network in the world integrating more than 10 time zones and possessing different load characteristics and generation arrangements. The networks under consideration supply electric power to more than 700 millions people living at two continents.

The investigation basic objective is to estimate possibilities and conditions of Western and Eastern networks simultaneous integration from technical, operational, organizational and juridical points of view. Arrangement list for each network is to be compiled for the integration process, and appropriate expenditure is to be evaluated. The project includes combination of simultaneously integrated networks investigation and numerical simulation of the networks operating modes on conditions that the participated systems keep own principles and performance standards. The main precedent condition in the case is to maintain sufficient reliability and safety levels of the networks.

While synchronous networks operation has to provide appropriate quality of the electrical energy.

III. ELECTRICAL POWER QUALITY MAINTENANCE

Exchange relations development in the power engineering field inspires scientific activity increase in the electrical power quality area. Fig. 1 shows number of world publications containing term “electrical power quality” versus time [2].

As can be observed from the figure, particular interest to the problem has increased from the year 1995. From that time one begun to realize significance of the power quality management problem.

There are several reasons for increased interest to the issue. The main of them are the following:

- power and consumer equipment became of less tolerance to electric power deterioration.

Fig.1. Time dependence of number of world publications dedicated to the problem of electric power quality.

Loss of electric power quality leads to incorrect equipment control and to making process delay, that results in production value considerable increase,

- liberalism in power engineering leads to revision of electric power conception. Previously electric power was supposed as a “general good”. Today exchange relations are developing and the electric power is the article possessing certain characteristics. Purchaser has the right to put in a claim to the electric power quality and to receive information describing quality factors.

- international relations development in the power engineering. Russian electric power export to many European countries is impossible because of the power discrepancy to international standards.

Electric power quality maintenance is not only the most important condition of power network normal operation, but also the condition of modern electric power market operation.

IV. NEED FOR INTERNATIONAL STANDARDS UNIFICATION

The problem of possible UCTE, NORDEL and UES/UPS networks integration comes to the following: which standards should be satisfied by the electric power quality. The UES/UPS 13109-97 standard [3] and international EN50160 standard, which is in force within UCTE and NORDEL systems, have several distinctions. While similar quality coefficients are determined according to different algorithms and in different time intervals. Frequency and voltage levels are the basic quality indices in all countries. Requirements to frequency and voltage levels in high voltage systems (Table I) and general-purpose systems (Table II) differ in different countries.

TABLE IICOMPARISON OF REQUIREMENT ESTABLISHED TO

ELECTRIC POWER QUALITY INDICES CALCULATION

№ Quality index

Calculation according to

Standard (GOST) 13109-97

Calculation according to

Standard EN50160

1. Steady-state voltage deviation δ Us

Observation takes place during 24 hours. Not less than 18 observations were carried out per 1 min. Averaging interval is 60 sek.

Indirect Magnitude of Voltage Supply (root-mean-square phase voltage).1-week statistics is available. Averaging intervals are 10 min.

2.

Frequency deviation f

Observation takes place during 24 hours. Averaging interval is 20 sek.

Power Frequency. 1 week statistics within the range of ±0.5 Hz from -3 to +2 Hz are available. Averaging intervals are 10 min, with possibility to fix interval duration of 10 msek. Min/max (during half period) for each 10 min.

The specified parameters are of a great importance for networks integration. Therefore, calculation methods and extreme intervals for the parameters need to be unified.

Detailed analysis of standard requirements established to other electric power quality indices allows to reveal which of them are important and to develop, finally, unified standards for electric power quality.

REFERENCES

[1] Решетов В.И., Семенов В.А., Лисицын Н.В., Единая энергетическая система России на рубеже веков. Москва: ЗАО «Издательство НЦ ЭНАС», 2002, 221 с.

[2] M. H. J. Bollen, I. Y.-H. Gu, Signal Processing Of Power Quality Disturbances, By the Institute of Electrical and Electronics Engineers, 2006, 861 р.

[3] ГОСТ 13109-97 «Качество электрической энергии. Совместимость технических средств электромагнитная. Нормы качества электрической энергии в системах электроснабжения общего назначения», Москва: Издательство Стандартов, 1998, 38 с.