Power Quality - Site Survey

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2006 IEEE PES Transmission and Distribution Conference and Exposition Latin America, Venezuela

Power Quality Site Survey Process for Regulated Electricity Market A. Abreu, and B. Castellano electrical system. It is developed in the Electric Utility “Energía Eléctrica de Venezuela (ENELVEN)”, which distributes in networks of 23.9 kV of aerial typed line construction area, and provides electrical power to part of the Western Venezuelan Area. The scope of this paper is to explain how the different aspects of the PQ are driven by a distribution company, and to analyze the result of the 202 PQ site surveys made in the different types of facilities. II. POWER QUALITY PROBLEMS When a disturbance exceeds the compatibility level a great probability exist that the loads, specially the sensitive ones, begin operating in an erratic way or with failures. These disturbances can be originated from the electrical networks or within the same facilities and installations of the users. Index Terms—Methodology, Market, Site Survey.

Power

Quality,

Regulated

I. INTRODUCTION

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he growing technological development in the last decades have driven to the use of loads based in electronics, and liable to electromagnetic disturbances such as: Harmonic distortion, flicker, transients, Sags, Swell; which form the different disturbances with which the Power Quality (PQ) is measured. When these exceed, the compatibility levels can cause the erratic functioning or failure of a load or equipment, bringing up three fundamental problems: Non fulfillment of the parameters of service quality agreed with the user, increase in operational cost by the failure on industrial productive processes, and a safety problem and integrity of persons before the failure on equipment in important facilities such as hospitals, airports, among others. Due to the fact of searching for satisfaction of quality needs by the customer, the distribution company invests resources in disturbance analysis, evaluation of user’s installations, and distribution network, with the purpose of determining under whose responsibility relies the problem detected. Currently the Venezuelan´s laws frame sets several duties and rights, where part of the PQ parameters is regulated, which protect both the users and the distribution companies. This paper develops the experience through eight (8) years of the PQ process since the beginning of the research, going through the stage of the attention of claims, until reaching the stage of being into a regulated A. Abreu and B. Castellano work in the electric utility “Energía Eléctrica de Venezuela (ENELVEN)”, Maracaibo, Zulia State, Venezuela, Operational Center “Teolindo Acosta – COTA”, (e-mail: [email protected], [email protected]).

1-4244-0288-3/06/$20.00 ©2006 IEEE

Environmental Conditions

Residential Voltage Quality

Distribution Network

Commercial PCC

Disturbances of the Transmission Network

Current Quality

Industrial Types of Users

Fig. 1. Lack of the PQ carried out in a distribution network.

In Fig. 1, the process where the distribution network is involved, and the electrical installation of the users is shown. The legal frame between the electrical distribution company and the users is the power meter (invoicing) which it is defined as a point of common coupling (PCC). Basically the distribution company is the one responsible of the voltage quality placed in the PCC, as this is the one responsible of generating, transporting and distributing the electrical power. The voltage quality can be affected specially by issues such as: maintenance, design, location of the capacitors, grounding systems, protection systems, regulating problems and low short circuit level, among others. Also, the user is responsible for not introducing disturbances to the distribution network, which can interfere in other users connected to the same network. Generally, the customer when they see affected the normal functioning of their loads and the problem is not an evident failure in some mechanism of the equipment, or variations in the brightness of the lighting system are observed, they put the responsibility previous to a deficiency in the PQ given by the distribution

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company. The user as the main affected due to the deficiencies of power quality, can feel one or several of the following symptoms: failures, erratic operation, decrease of the useful live, fluctuation of the brightness of the lamps, overheating in conductors, cables and motors, among others. Due to this reason, the users, specially the ones in the industrial and commercial sectors, which depend of the productive processes, sometimes in continuous periods during the 24 hours of the day during all year round, require from the Electric Utility, a quality level in a way that their productive processes are not affected. III. POWER QUALITY REQUIREMENTS From the beginning of the electrical systems, the Electric Utility have seen the quality focused in time and frequency of interruptions of the circuit feeders to a medium voltage, the regulation of voltage and the fundamental frequency, which for the Venezuelan case is of 60 Hz. No type of disturbance was monitored, neither systematically studied, nor did control limits legally required exist. The PQ surveys begin in the electrical systems of ENELVEN in the year 1997, because of a need of the petroleum sector due to the injection of current harmonic current distortion caused by the power converters. For research purposes, and meeting other kind of requirements from industries and from the commercial sector, a methodology for the attention of claims was developed by PQ. 80

I

70

II

III

60 50 40 30 20 10 0 1998

1999

2000

2001

2002

2003

2004

2005

Fig.2 Amount of PQ site surveys carried out during the period from 1998 to 2005.

In Fig 2, the evolution of the amount of PQ Surveys carried out to the installations of the customer and the distribution networks is shown. In the same, three (3) stages are shown. One first stage between the years 1998 – 2001, during this period the approach of surveys was focused to the research area and to identify large industrial users, who are possible generators of PQ problems. During year 1998, the distribution circuits of a sub - station with petroleum load and other one with industrial load where evaluated. In the year 2000 an aleatory assessment of the installations of the residential and commercial users was made. A second stage, during the years 2002 – 2004, where what was learned in this previous stage was implemented, including the assistance to big industries. Finally, the third stage begins in the year 2005, where an increase of the amount of surveys resulting from optimizing works in the methodology defined for the execution of the same, was observed. In this stage it is started to get to the sectors of the smaller commercial and industrial users, and in

some cases to the residential ones. During the eight (8) years of research, 202 PQ surveys were developed. During the second period of year 2003, the technical regulations [9] and [10] at National wide (Regulated Market), where the rules about the duties and rights related to the disturbances set forth for the PQ are stipulated. The concept of the quality of the Technical Product (TP) where the levels voltages, harmonic voltages and flicker is introduced. In this stage, it is stipulated that the users have the right to claim due to TP problems, and the distribution company shall make an aleatory assessment of the different users supported in the measuring of the electrical parameters. A. Customer Requirements During more than 100 years that ENELVEN has been distributing electrical power, claims where the user gives complaints due to fluctuations of the electric service and damages of the appliances have been attended, which have been managed through teams of electric technicians that standardally were limited to check the condition of the connections from the distribution transformer to the power meter, and sometimes, voltage recorders with paper and ink where installed until the time when the voltage registers appeared at the beginning of the 90’s. It is as of the year 1997, added to the increase in the use of non linear and sensitive loads, when at ENELVEN began to study that some other causes might have been giving origin to said problems, and to look for solutions in a timely and successful way. This is why the engineering personnel are dedicated to see about the cases that the crew of workers cannot solve. B. Government Regulation Requirements The Government to prove that the power utilities are investing in works and maintenance of the networks establishes mechanisms to supervise the technical product quality. This is made through a government utility regulation office which is responsible to look after the compliance of the technical regulations by supervisions. For the Venezuelan case the supervision is only directed or based in the voltage level, voltage harmonic and flicker. In the present time this requirement of the government utility regulation office is in the introductory stage at National wide. In Venezuela, Technical Product Quality supervising experience only exists in a distribution company located in the Eastern area of Venezuela [13] specifically in the tourist area, there aren’t any flicker or harmonic voltage problems. They also have the experience in the capital area of Venezuela [14], where flicker of harmonic voltage problems exist, but in a small amount. This shows that the PQ problems depend in a combination of factors such as the short circuit level, type load among other. It should be pointed out that the supervising mechanism, even though it is a requirement of the government regulation, shall be seen by the distribution company as a preventive mechanism to detect problems in the network which have not been detected through the claims of the users. Therefore, this supervision shall be seen as a mechanism proper of the operation of the network.

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C. Electric Utility Requirements The new trend is to keep the customer satisfied with the service given, not only selling power but also offering additional services especially to the big customer with high invoicing levels, which represent a strategy of improvement of customer’s satisfaction. This also helps to know the characteristic of the load and in a preventive way, problems can be detected and the technical product quality that it is sold to them can be certified. With this strategy of the distribution companies toward the big customers, valuable alliances can be established and strategic partners are obtained. Therefore, the PQ Process can be differentiated from three (3) different points of view: Claims, Supervisions and Certification. Next, the three types of processes identified from different points of view are described, describing the requirements of the customer, and government regulation towards the distribution company, and from this one to the customer. IV. POWER QUALITY PROCESS As a result of combination of the customer’s requirement, the government and the same distribution companies to cover the needs of its customers, conclude that the PQ in a distribution company has three (3) processes: answer claims, quality certify and supervise technical product quality. Next, each one of them is described. A. Certification This kind of survey can be requested by the customers when they require installing a reactive compensation in their system, to make extensions or to confirm the technical product quality delivered to their facility by the distribution company is within the national and international regulations. Also, this type of survey is made by the initiative of a distribution company, especially towards the big industrial customers as a mechanism to approach and get to know the kind of load. B. Claim This is requested by the customer when he declares to have problems in the electric supply. This process does not only consist in measuring the electrical parameters and to capture the disturbances, but also in determining the cause that arises such disturbance, to investigate if the same comes from the distribution network or from the customers installation, as it is shown in the methodological process shown in Figure 3. The importance of this process is that it shows directly the existence of some problems or a disturbance out of limit, shown in a “non normal” behavior of the loads. C. Supervising This is a PQ application area, where an aleatory sampling of different points of the distribution system is made, with the purpose of detecting disturbance values, out of what it is set forth in the government regulations. Not all the disturbances are regulated, there are only brought up the voltage level, the harmonic of voltage and flicker. This kind of measurement campaign requested by the government utility regulation office has as a goal to take a sample of the power sales points

of several customers, in order to asses the quality of the technical product delivered. The difference between a claim and supervision is that in the claim the customer already declares to have a problem and in the supervision a search to see if a problem exists will be carried out. The certification and supervision processes are very similar, as in the first one the distribution company chooses the customers, and in the second one is the government utility regulation office the one that chooses them. The measuring campaigns are a tool, where through the monitoring; they can plan the maintenance in the distribution network such as it was demonstrated in [13]. V. POWER QUALITY INDICATORS During the eight (8) years of PQ development in ENELVEN, technical standards such as IEEE 1159 [1], IEEE 1100 [2] and IEEE 519 [3] and the series of the IEC 61000 [5] and [6] were used for the analysis. In Venezuela they only had the COVENIN 159 [8], were limits are stipulated for the levels of low, medium and high voltage. The need to have a National standard with the purpose that the other Electric Utility of the country can make evaluations in their distribution networks under the same reference. One of the PQ parameter that has suffered changes has been the flicker with the Pst indicator. Before the curves described in [3] were used, then the “Flickermeter” measurement method set forth in the regulation IEC 61000-4-15 [6] appears. This same regulation undergoes changes in the measurement methodology, which makes that the registries give different Pst values when being injected by the same signal, such as it was demonstrated in [12]. This is solved in the year 2003 with the publication of a new version of this standard, being in-force up to date. In relation to the harmonic ones the procedure set forth in the standard IEC 61000-4-7 [6] is used, through the THDv (Total Harmonics Distortion of Voltage), THDi (Total Harmonics Distortion of Current) and the TDD (Total Distortion Demand) indicators. Additionally the voltage unbalance indicators are evaluated with the calculation methodology set forth in the standard IEEE 1159 [1]. The indicator of the power factor is handled, that, even though it is not a disturbance, it is an important factor in the regulation of the voltage and in the amplification of the harmonic current. For this reason it is assessed through the limit (0.9 inductive) stipulated in the technical regulation [9]. Additional to the limits of the parameters to evaluate its impact the duration in time of the non compliance of the same shall be calculated. Currently, at the level of the technical regulations and standards only the THDv, THDi, TDD [7] and Pst [10] indicators are required that the limits should not be exceeded in a 95% of the measurement period. For the case of the voltage regulation in Venezuela a 97% is required through what it is set forth in the technical regulation [10]. For the case of the Power Factor Indicators, Voltage Unbalance and Current, there does not exist any reference, National or International, where the compliance time is stipulated. In the present time, in order to evaluate its impact, the 95% of the compliance is used as a reference. With respect to the Transient, Sags and Swell no indicator is handled. At

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world’s level it does not exist uniformity on an indicator for this parameter and the ones that exist are based in the measurement period of one year. The practice, especially in the case of the surveys for claims, is to evaluate if the registered Transient, Sags or Swell is the responsible of causes the failure or erratic operation, studying its origin. VI. DEVELOPED METHODOLOGY

A. Initial Data Collection The basic information that shall be collected by the PQ Engineer begins by knowing the problem and type of loads that the electrical installation has. Therefore, the subscriber is given a form to be filled out with the help of their electrical maintenance personnel. Also an interview is made where unknown issues are explained and which the PQ Engineer shall make: x What kind of equipment has problems?. x Is it a sensitive load?. x What sensitivity do those equipment present?. x Does the equipment present problems from the time it was installed?. x When do these disturbances occur (time/date)?. x Are they recurrent or not?. x Recently they have made changes in the grounding system of the installation?. x Do the installations have motors of great power?. x Does it observe falls in the brightness of the incandescent light bulbs?.

The methodology proposed mainly includes five stages, initial data collecting, and inspection to the electric installation of the customer, inspection to the distribution circuit, measurement of the PQ parameters and analysis of the case; this latter allows to propose several recommendations, and to stipulate the causes that can minimize the presence of the disturbance. As it is observed in Fig. 3, the supervision and certification processes are the simpler ones, as in these ones, only a measurement in the point of power sale is made (PCC) and the results are compared with the technical regulations and standards. If the deviated values result to the stipulated values, the methodology of the claim is applied with the purpose of B. Inspection of the customer’s electrical installation determining the cause. The three more common main issues that shall be checked Power Quality Site Survey in an electrical installation are: 1) Distribution Transformer Inspection x Visual inspection of the connections. Certification Claim Supervising x “TAP” position. x Type of connection (Delta or Star). Initial Data Collection x Capacity of the transformer. x Type of transformer. Inspection of the Customer x Impedance. Electrical Installation x Temperature measurement. x Existence of vibrations. Inspection of the Distribution Network x Hum detection (possible arching, bad connection). 2) Low Voltage Electrical Panel Inspection Measurement of the x Visual inspection of connections. Electrical Parameters in the x Measurement of the impedance of the neutral and Point of Power Sale grounding conductor. x Verification of the phases rotation. x Is the size of the conductor adequate?. To Stipulate Recommendations x Hum detection (possible arching, bad connection). N Comply with the Cumple con las and the carry out the Solution of Regulation? Normas ? x To determine the presence of burning smell (possibly a the Problems bad connection or an overload of the conductor). Yes 3) Wiring and Grounding System Inspection x To validate if the grounding design is suitable for that It is Certified that the Feeding of the installation as is set forth in the National Electric Installation or Network does not have Code. Power Quality Problems x Visual inspection of the electrodes and connections, looking for corrosion signs, or possible disconnection. Fig 3. PQ process in a Distribution Company. x See visual inspection of the connection adjustments. When a claim is received, the first thing that it is done is to x Current measurement in the electrode grounding exhaust the site survey stage, with operative units that make a conductor. checking or revision to the installations of the Electric Utility x Measurement of the grounding impedance. (e.g., a loose connection, and oil leak in the TX, etc), once that 4) Equipment the emergency unit determines that it has not found any sign x True RMS hand held with oscilloscope and calculate that relates the customer’s complaint, then the execution of the THDv, THDi, power factor. PQ survey is activated. x Heat Tracer.

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medium installations, up to buildings with great computer concentrations. Within the typical loads found in the ENELVEN network, in the industrial area, it includes melting C. Distribution Network Inspection furnaces by electrical arch, power converter AC/DC and It consists in revising the environmental and physical AC/AC of small and great power. elements that can influence the primary distribution network In this section the analysis of the results of the PQ surveys of the Electric Utility. The elements that might cause voltage will be developed. That the 83% of the totality of the cases disturbances from the distribution network are: studied are focused in industrial (43%) and commercial (40%) x Banks of switchable capacitors. customers. A 10% of the cases analyzed distribution network x Adjacent loads with high potency motors. and only a 7% of the cases in residential installation. x Bad condition of the conductor insistent fractures. A. Electrical Parameters which are a Responsibility of the x Continuous presence of electrical storms. Electric Utility x High impedances in the primary network (non In Fig. 4, the four parameters which are responsibility of adequate conductor gauge). the Electric Utility are observed, it was found that for the x It is convenient to obtain the circuit failure during the voltage level case the compliance degree of more than 70% year is advisable. followed of a 80% related to the voltage unbalance of the D. PQ Parameters Measurements studied cases. The voltage harmonic and flicker exceed more The first measurement that shall be made is in the common than 90% of the survey cases. 202 PQ Site Survey natural point of common coupling (PCC) between the 100% distribution company and the customers, which is the power 90% sales point. Based in the results to make measurements to the 80% head of the distribution network is evaluated or to make them 70% directly in the load that is having problems. As a standard, it 60% is convenient to use a measurement period of seven (7) days, 50% with the purpose of obtaining a behavior profile during a week 40% with an interval of 10 min. A great variety of PQ recorders exist in the market. In the present, there are 2 types of 30% recorders the A and B set forth in the IEC 61000-4-30 [6] 20% standard. The class A recorders have unique features for all 10% the manufacturers, but the class B ones leave a space for the 0% manufacturers to include the parameters features to be Voltaje Level Voltage Voltage Flicker (Pst) measured. This makes that a great variety of class B exist, Unbalance Harmonics which in average can cost one third compared with the ones of Complies With Does Not Comply With class A. When a case is presented, a class B recorder is Fig 4. Responsible parameters of the Electric Utility. installed and out of regulation parameters are measured, or the problem that this is causing, the erratic operation of the load is The problem with the voltage harmonics appeared in case not being detected, then, the installation of the equipment class of petroleum installations that use power converters connected A is made. This allows the optimization of the resources. to rural distribution network which present low level of short E. Case Analysis circuit. For the Flicker case, it only appears in case of arc The last step, previous to reporting the result, consists in furnaces, crushing machines, basically with industrial user. analyzing all the collected information. This analysis may B. Electrical Parameters Customers´ Responsibility consist mainly in confirming the limits of the indicators In Fig. 5, the three parameters which are responsibility of mentioned above in accordance to the applicable standards the customers are observed, it was found that for the current and regulations. Also, and not least important, it is necessary unbalance case the compliance was of a 20% followed of a to analyze the result of the inspection made which give several hints in order to find the origin of the problem, this analysis 30% related to the power factor and the current harmonic ones can be simple on the contrary it may be complex according to only reaches a 40% of compliance degree of the survey cases. The current balances and the power factor impact directly in the load characteristics and to the process that the customer the voltage regulation. Additionally, it is observed how at the manages. It is important to remind that each case is specific. western Venezuela area, because of the type of load used, the harmonic currents have a higher impact at the distribution VII. RESULT OF THE POWER QUALITY SURVEY networks. FOR THE YEARS 1998 - 2005 x Grounding test devices. x Digital Camera.

The distribution network where the surveys were made is an extraordinary sample as there are different kinds of loads. In the industrial area from the petroleum loads, carboniferous, cement makers, siderurgical ones, as also in the light and medium industries. In the commercial area, from small and to

6 202 PQ Site Survey

100% 90% 80% 70% 60% 50%

It is recommended to the rest of the distribution companies to collect the results of the PQ Surveys in order to obtain attendance at National level that will be useful as a base to estipulate the technical regulations and standards in order to satisfy the quality requirements requested by the customers in accordance to the reality of the electrical sector of each country.

40%

IX. REFERENCES

30%

[1]

20%

[2]

10% 0%

[3] Current Unbalance

Power Factor

Complies With

Total Demand of Harmonic Distortion

Does Not Comply With

Fig 5. Parameters Customers´ Responsibility.

C. Responsibility of the PQ Claims Issued by the Customers Of the 202 cases 121, were evaluated claims, the 82% represent problems at the PQ parameters under the responsibility of the customer, and an 18% of the cases are associated to problems in the distribution company. This data gives a trend in the surveys of PQ survey where the results direct to a responsibility proportion of 20-80 between the distribution company and the customers. Additionally, at electrical installations level, only a 88% of the inspected cases with section 408 regarding to board and an 90% of performance at section 250 regarding to grounding system referred at the CEN [15] (National Electrical Code of Venezuela).

[4] [5]

[6]

[7] [8] [9] [10] [11]

[12]

VIII. CONCLUSION The PQ site surveys have allowed us to establish a more effective communication between the customer and the Electric Utility. When claims have been presented we dedicated hours/man in order to find and present the customer not only the origin of the problem but also the possible solutions that might be applied and the optimum use of the service. Through the claim for PQ, it can give you an idea of the condition of the distribution networks Technical Product Quality. The knowledge of the results of the PQ Surveys made in Venezuela provide a valuable information to the government utility regulation office as it gives an approximation to the quality level of the technical product that is provided to the customers before making the supervisions through measurement campaigns. At knowledge of the areas or types of loads where problems already exist, through the claim attention and the effort of the measurement campaign, the resources can be directed to areas where a high claim incidence rate doesn’t exist, and in this way the equipment, and man-hours can be reduced for the supervision of the Technical Product Quality. The PQ Engineer has obtained a very important role as he is the responsible for looking after the Technical Product Quality that is sold to the customers.

[13]

[14] [15]

IEEE Recommended Practice for Monitoring Electric Power Quality, IEEE Standard 1159-1995. IEEE Recommended Practice for Powering and Grounding Sensitive Electronic Equipment Emerald Book, IEEE Standard 1100-1999. IEEE Recommended Practices and Requirements for Harmonics Control in Electrical Power Systems, IEEE Standard 519-1992, IEEE Recommended Practice for Measurement and Limits of Voltage Flicker on AC Power Systems, IEEE Standard 1453-2004. IEC (International Electrotechnical Commission) Standards, IEC 61000-2-1 (Electromagnetic Compatibility, Part 2: Environment, Section 1: Description of the environment), IEC 61000-2-2 1990. IEC (International Electrotechnical Commission) Standards, IEC 61000-4 (Electromagnetic Compatibility, Part 4: Testing and Measurement Techniques) Section 7: IEC 61000-4-7, 1991. Section 14: IEC 61000-4-15, 2003. Section 30: IEC 61000-4-30. COVENIN Harmonic Control in Electrical System, COVENIN 3842:2004, COVENIN Standardalized Voltages, COVENIN 159:1997 Technical Regulation, “Service Regulation”, (November 2003), Official Gazette # 37.825. Technical Regulation “Quality of the Power Distribution Service”, (August 2004), Official Gazette # 38.004. Abreu A, Ochoa C, Villalobos J, “Industrial Loads: PQProblem Sources in the Electrical System of ENELVEN”, work Published in congress IEEE ANDESCON, 1999. Abreu A, Kermendy E, “Comparative Analysis of Flicker Measurement with Different Makes of Recorders with Certification IEC 61000-4-15”, Published in the First Conference Cycle on Technical Product Quality , Program Organized by the Ministry of Energy and Petroleum of Venezuela, 2004. Salazar L, Hernández I, “Quality Control of the Electrical Service as a Tool in Investment Planning”. CIER – International Seminar on Distribution Systems Planning and Quality, 2001, Argentina. Ascanio C., Alves R., “Power Service Quality Evaluation in the AES – ELEGUA Distribution system”. “CEN National Electrical Code of Venezuela”, CODELECTRA 2004.

X. BIOGRAPHIES Augusto Abreu M., Electrical Engineer graduated from the Rafael Urdaneta University, in 1997. His professional experience goes from planning Network Transition and Distribution, PQ Survey, Forensic Engineering, Distribution Network Maintenance, Materials Technical Specifications, and Evaluations of Material Quality. Currently he works as a Conceptual Engineer in the Distribution Engineering area in “Energía Eléctrica de Venezuela (ENELVEN)”. He belongs to the team that is preparing the technical PQ standards for CODELECTRA. E-mail: [email protected] Benita Castellano., Electrical Engineer graduated from the University of Zulia in 2001. Her professional experience goes from the electrical maintenance of the industrial installations specifically on telephone central systems, and the execution of PQ Surveys. Currently she works as a Conceptual Engineer in the Transmission Engineering area in “Energía Eléctrica de Venezuela (ENELVEN)”. E-mail: [email protected]