On-line monitoring of substation condition a Romanian experience. V. ZAHARESCU, Vl. ROSCA Nova Industrial SA. CN Transelectrica SA Romania

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1 21, rue d Artois, F PARIS http : // B3_201 CIGRE 2012 On-line monitoring of substation condition a Romanian experience C. MOLDOVEANU*, V. BREZOIANU, S. GAL, V. METIU, A. VASILE, V. URSIANU, I. IONIŢǍ, C. DIACONU, I.D. HATEGAN, F. GONI, C. RADU V. ZAHARESCU, Vl. ROSCA Nova Industrial SA CN Transelectrica SA Romania Romania T. FAGARASAN, G. MORARU Smart SA Romania SUMMARY The paper presents the results of the correct on-line evaluation of the current technical condition of the electrical equipment in high voltage substations owned and operated by Romanian Power Grid Company - CN Transelectrica SA, using intelligent monitoring systems. The paper describes parts of the intelligent systems dedicated to on-line monitoring of all primary equipment used in the 400/110 kv Darste substation (the 400/110 kv Darste substation is the first high voltage substation completely on-line monitored in Romania). The complex system realized for the on-line monitoring of 400/110 kv Darste substation includes dedicated systems designed for the on-line monitoring of power transformer, shunt reactors, circuit breakers, disconnectors, voltage & current transformers and surge arresters. These intelligent monitoring systems can be used stand-alone or within an integrated system for on-line monitoring of electric power stations and substations Smart Grids. Also the paper describes the software that makes the integration of the mentioned intelligent systems as a whole and makes also their connection to the RCM integrated software designed for managing the technical condition and maintenance of the HV power transformers, shunt reactors, current and voltage transformers, circuit breakers, disconnectors and surge arresters in the 110 kv kv substations of the Romanian Power Grid. The paper points out also specific aspects, based on the experience and knowledge gained in projects developed for CN Transelectrica, related to the on-line substation condition monitoring system. KEYWORDS Substations, on-line monitoring, Smart Grids, HV equipment, power transformers, shunt reactors, circuit breakers, disconnectors, current and voltage transformers, surge arresters *CMoldoveanu@novaindustrialsa.ro

2 1. INTRODUCTION The age of the existing high voltage electrical equipment in operation in the national power system is continuously increasing and their failure rate grows with the increase in age. The great majority of failures appears as a result of the combined action of the thermal and electric stresses, to which mechanical stresses are added. In order to repair the faulty equipment, it is often necessary to take them out of operation for a long period of time. The policy related to the management of the operation and maintenance of the existing high voltage electrical equipment is based on the following main principles: Their maintenance or even replacement should take into consideration their momentary technical condition in the first place and not their age; The on and/or off- line monitoring activity should discover (identify) the modification in the momentary technical condition in due time, in order to minimize the risk of major outages, accompanied or not by fire or other losses; Extending the service lifetime in operation, by the means of adequate maintenance. The Romanian Power Grid Company (CN Transelectrica) intends to implement "Smart Grids" networks based on on-line monitoring systems dedicated to: high voltage substations, overhead power lines and power quality (figure 1). Figure 1 CN Transelectrica concept to integration in Smart Grid networks of the on-line monitoring systems dedicated to high voltage substations, overhead power lines and power quality CN Transelectrica started the pilot project for the on-line monitoring of primary equipment in the high voltage power stations, part of the National Power Transmission Network, in CN Transelectrica chose three stations (one 400/110 kv and two of 220/110 kv) of those not included in the plan to be refurbished in the close future, but with most of the major equipment with consumed lifetime greater than 25 years. The 400/110 kv Darste substation (one of the three stations) is now the first high voltage substation completely on-line monitored in Romania (the project was completed entirely in 2010). The 400/110 kv Darste substation diagram is presented in Figure 2. Figure 2. Single line diagram of 400/110 kv Darste substation The paper briefly describes the technological solutions and experience gained in projects developed for CN Transelectrica related to life and operating management of high voltage equipment using the on-line substation condition monitoring system. 2. COMPLEX SYSTEM FOR THE ON-LINE MONITORING OF 400/110 kv DARSTE SUBSTATION The EMCSIT complex system for the on-line monitoring of 400/110 kv Darste substation includes (Figure 3): 167 pcs. apparatus for on-line monitoring of the technical condition and the operating parameters of 400 kv and 110 kv electrical equipment, all created and developed 100% in Romania, based on original ideas and conceptions : 1

3 o 2 pcs complex systems for on-line monitoring of 250/250/80 MVA 400/121/20 kv power transformer and respectively of 100 MVAr, 400 kv shunt reactor ; o 30 pcs for circuit breakers monitoring; o 104 pcs for disconnectors monitoring; o 22 pcs for current transformers and voltage transformers monitoring; o 13 pcs for surge arresters monitoring; 2 pcs. on-line monitoring systems to control the power quality; a substation video monitoring system; hundreds of special sensors and transducers; GPS modules for synchronization; PC servers, etc. Transformer IED Surge arrester monitors Disconnector monitors HV bushing monitor Current/voltage transformer monitors Circuit breaker monitors PC screens in 400/110 kv Darste substation control room Figure 3. Images from the on-line monitored 400/110 kv Darste substation 2.1. Intelligent monitoring systems for high voltage electrical equipment in Darste substation System for on-line monitoring of the 250/250/80 MVA power transformer and of the 100 MVAr shunt reactor This system assures on-line data acquisition regarding: a) Operating condition: power transformer or shunt reactor meets / does not meet the standards of operation; it is connected / disconnected to / from grid; b) Operating parameters: currents, overloads, voltages, overvoltages, voltage increase, frequency, power factor; powers: active, reactive, apparent; temperatures: winding temperatures, oil temperature, hot spot temperature, ambient temperature, inlet/outlet cooler temperatures, etc.; c) Operating condition for the active part (core + windings + inner connections) through on-line monitoring of: dissolved gas-in-oil: hydrogen (H2), acetylene (C2H2) and carbon monoxide (CO) concentrations; partial discharges: acoustical signals produced by partial discharges; the moisture level of insulation by: on-line measurement of water-in-oil content and evaluation of the water content in the solid insulation; d) Operating condition of the cooling system, by: displaying the number of the coolers (cooling batteries) in operation; highlighting the operating oil pumps and fans; evaluating the efficiency of the coolers activity; evaluating the total operating time or between overhauls/ repairs of oil pumps and / or electric fans; displaying the proper or inadequate state of the cooling system; e) The insulation condition of high voltage bushings equipped with tap for measuring the power / dissipation factor, by: measuring of the current through C1 dielectric (bushing tap current) and assessing the unbalance current resulted from the phase sum of the currents through the C1 dielectric of the bushings mounted on R, S, T phases of the same three-phase windings; 2

4 measuring the capacity of the C1 dielectric on each high voltage; measuring the tangent of the phase angle between the bushing insulation currents for each pair of bushings of the same three-phase winding; displaying the proper or inadequate state of the high voltage bushings; f) The operating condition of the on-load tap changer - OLTC- (only for on-line monitoring of the power transformer), by: monitoring the operation position of the tap changer; measuring the load current of the drive mechanism motor and its stamp; counting the cumulated number of OLTC operation; displaying the proper or inadequate state of the tap changer. g) The condition of the oil conservator associated to the transformer tank: the oil level in the tank, signaling of the moment when oil in conservator reaches the maximum or minimum level; h) The condition of the oil conservator associated to the tap changer compartment: signaling of the moment when oil reaches the maximum or minimum level; i) The operating condition of the Buchholz relay: the signaling step and the tripping step; j) The operating condition of the pressure relay associated to the OLTC diverter switch compartment; k) The operating condition of overpressure protection devices associated to the main tank of the transformer. Each on-line monitoring system contains one IED - Intelligent Electronic Device that receives signals from sensors, transducers or monitoring subsystems, and sends the information regarding the operating parameters and momentary state of the monitored equipment, to the control room or to the protection systems. The dedicated software of the on-line monitoring system is compatible with Microsoft Windows XP and it is designed on a client-server architecture. Figure 4 Software main view for the on-line monitoring of 250/250/80 MVA power transformer The software allows: the real-time viewing of the parameters which are monitored on-line, the diagnose of the monitored power transformer, the display of historical measurements (stored in a database) and their evolution in time (as charts, tables, etc.), the export of the data monitored online in the RCM (Reliability Centered Maintenance) database, for the on-line and off-line analysis, the technical expertise and prediction of the remaining lifetime, based on the information stored in the RCM database, etc. In Figure no. 5 it is presented as example, the data acquisition form regarding the gases content [hydrogen (H2), acetylene (C2H2), carbon monoxide (CO)] and water content in 250/250/80 MVA transformer oil. Figure 5 On-line monitoring of the gases and water content in transformer oil In Figure no. 6 it is presented as example, the data acquisition form regarding the current through C1 dielectric, the capacity of the C1 dielectric on each high voltage, the tangent of the phase angle between the bushing insulation currents for each pair of bushings of the same three-phase winding; 3

5 displaying the proper or inadequate state of the 400 kv and 110 kv bushings of the mentioned power transformer. Figure 6 On-line monitoring of 400 kv and 110 kv bushings The on-line monitoring equipment of the partial discharges (acoustical signals), installed on the 250/250/80 MVA power transformer and 100 MVAr shunt reactor, indicates big differences between the values of the same parameters (figures 7a and b), due to signals produced by mechanical vibrations, higher at the shunt reactor than at the power transformer. 7a 7b Figure 7 The on-line monitoring of partial discharges (acoustic signals) of partial discharges at 250/250/80 MVA transformer (7a) and at 100 MVAr shunt reactor (7b) System for on-line monitoring of the 400 kv and 110 kv circuit breakers This system ensures the on-line data acquisition regarding the operating parameters and the condition of all monitored circuit breakers from substation, such as: circuit breaker technical condition, close / open operating condition, operating times, lack of synchronization of operation between poles, arcing times, contact speed, re-ignition, number of operations, wearing of the contacts, pressure of the insulating fluid, the ambient temperature, the operating condition of the operating mechanism (current through motor, operating times. Each monitoring apparatus works connected to a local data processing unit. The processing unit provides recording and processing of data coming from several on-line monitoring apparatus. The processing unit stores the data and then transmits them through the LAN, to the control room of the substation, or through WAN to the Regional Monitoring Center. The operation of each on-line circuit breaker monitoring apparatus is divided into three sections, namely: a) Section for measuring the parameters in stand-by, where the following parameters are measured: operative voltage, ambient temperature, SF6 gas pressure, etc.; b) Section for measuring the operating parameters, where the following parameters are measured: currents (through opening and closing coils), each phase line current, dynamic characteristics of the circuit breaker (calculated by software, based on parameters measured directly). Each measurement lasts 3 seconds, the whole event being completely recorded. In this section the digital signals are also included - opening, closing, end of stroke, etc. c) Section for signaling, where signalization events generated by incorrect operation of the monitored circuit breaker (including switchgear) are measured, for example: lack or fall below a certain limit of the battery voltage, fall below a certain limit of the SF6 gas pressure, the lack of some mandatory digital signals - end of stroke after a close or open operation, etc. 4

6 The software dedicated to the on-line monitoring system for high voltage circuit breakers is structured in the following modules: a) server application software, for data acquisition and Oracle database storage EMCSIT-I Server ; b) client application software, for viewing analog and digital parameters (states) EMCSIT-I Client, c) application software for viewing and analyzing events EMCSIT - I Event graphics ; d) application software for viewing history information recorded in the database EMCSIT-I History. The interface of client/server application software allows the user to view values for the monitored analog and digital parameters (Figure 8) and to view information on the events that involved the monitored circuit breaker (Figure 9). Figure 8. Main view EMCSIT - I server Figure 9. A circuit breaker opening operation System for on-line monitoring of the 400 kv and 110 kv disconnectors The system provides the on-line monitoring of all high voltage disconnectors from substation, ensuring on-line data acquisition regarding the operating parameters and the condition of the monitored equipment, such as: disconnector technical condition, close / open operating condition, operation times, lack of synchronization of operation between poles, contact speed, number of operations, the ambient temperature, the operating condition of the driver mechanism (current through motor, operating times, etc.). Each monitoring apparatus works connected to a local data processing unit. The software for disconectors on-line monitoring contains similar modules as those mentioned for the on-line monitoring of circuit breakers (Client, Server, Event graphics, History). The interface of client/server software allows the user to view values for the monitored analog and digital parameters (Figure 10) and to view information on the events that involved the monitored disconnector (Figure 11). Figure 10. Main view EMCSIT-S server Figure 11. A disconnector opening operation 5

7 System for on-line monitoring of the 400 kv and 110 kv current and voltage transformers This system provides the on-line monitoring of current and/or voltage instrument transformers, ensuring on-line data acquisition regarding the operating parameters and the condition of the monitored equipment, such as: the technical condition of the transformer, the operating condition, the pressure of the insulating fluid, etc. The equipment can also ensure data on current and/or voltage over-stresses (the estimated amplitude, the occurrence time, the event duration, etc.) in the power network where the instrument transformer is mounted. The software for the current/voltage transformer on-line monitoring contains similar modules as mentioned for the on-line monitoring of circuit breakers (Client, Server, Event graphics, History).The interface of client/server software allows the user to view values for the monitored analog and digital parameters (Figure 12) and to view information on the events that involved the monitored current/voltage transformer (Figure 13). Figure 12. Main view EMCSIT TC/TT server Figure 14. Main window EMCSIT - D server monitored analog parameters (Figure 14). Figure 13 An instrument transformer event capture System for on-line monitoring of the 400 kv and 110 kv surge arresters The system ensures the on-line data acquisition regarding the operating parameters and the condition of all monitored surge arresters from substation, such as: the technical condition of the surge arrester, the total current passing through each surge arrester on the R, S, T phases of the same power network, the unbalance current resulting from the total currents passing through the surge arresters on the three phases of the network, the third harmonics of the total current through each surge arrester, the number of operations for each surge arrester on R, S, T phases. The software for surge arrester on-line monitoring contains the following modules: Client, Server, History. The interface of client/server application software allows the user to view values for the All on-line monitoring equipment EMCSIT TRAFOMON, I, S, TC / TT and D are integrated into the SCADA system, into the Transelectrica s intranet (fiber optic and GSM) network, and also can be used as standalone equipment or integrated into an on-line monitoring system of primary equipment in high voltage substations - Smart Grid Integrating intelligent EMCSIT systems in the complex system for on-line monitoring of 400/110 kv Darste substation All mentioned on-line monitoring systems, dedicated for the on-line monitoring of all high voltage equipment in 400/110 kv Darste substation, were integrated into EMCSIT INFO station, a complex 6

8 software system for substation monitoring. This dynamical software application offers the users a simple and easy to use graphical interface, allowing to acquire information on the monitored parameters and technical data from the local servers corresponding to the dedicated monitoring systems that individually monitor all primary equipment in Darste substation. Figure 15. The graphical interface of EMCSIT INFO station application presents the monitored substation s schematic electrical circuit diagram The EMCSIT INFO station software is installed on the central server which is in the same LAN with the local servers from the substation relay rooms. The software updates the information displayed every minute, so any change in the values of the monitored parameters or states, for each one of the types of items displayed, can be viewed. In terms of connecting all EMCSIT monitoring equipment in the substation, the software acquires signals in real time and updates the substation s diagram, according to the information received (Figure 15). When the user moves the mouse cursor over the graphic element that represents a type of primary equipment, information such as name and most recent measured values for the monitored parameters will be displayed. If user requests a detailed view for a specific monitored equipment, by clicking with the mouse on the graphic element corresponding to that device, a new window will appear, containing the client software for that specific equipment. For example if a disconnector was selected, EMCSIT INFO station software will connect to the server database, will make the correlation between name of the device and the ID recorded in the database for that equipment and will open a new window for the dedicated EMCSIT - S Client application software. EMCSIT - S Client runs within the same LAN with EMCSIT - S Server application and acquires the latest information recorded in the database for the selected device. 3. CONCLUSIONS Clearly the on-line monitoring of primary equipment in high power substations reduces the volume and the costs of maintenance works, and provides a grounded justification for the transition from timebased predictive maintenance, to maintenance based on technical condition of equipment. The intelligent on-line monitoring systems described above and used within in 400/110 kv Darste substation provides to the user (CN Transelectrica) quick and correct information about the operating parameters and the technical condition of all monitored high voltage equipment, being an optimal support for best real time decisions, on the management and safe operation of substations, with relatively reduced costs. In addition to that, important useful information was obtained in real time, with the equipment in operation, some being impossible to obtain with off-line measurements and tests. 7

9 The solutions adopted for 400/110 kv Darste substation will be applied as a first phase to the other two 220/110 kv substations, part of the CN Transelectrica pilot project for a Smart Grid system for on-line monitoring of power substations. 4. BIBLIOGRAPHY [1] C. Moldoveanu, V. Brezoianu, A. Vasile, V. Ursianu, F. Goni, C. Radu, Ir. Ioniţă: Intelligent System for the On-Line Real Time Monitoring of High Voltage Substations Proceedings of the International IEEE Conference Innovative Smart Grid Technologies-Europe, October-11-13, 2010, Gothenburg, Sweden, paper ; [2] S. Gal, V. Zaharescu, T. Fagarasan, M. Oltean, C. Moldoveanu - Integrated system of on-line ETG monitoring parameters, part of the Smart Grid development. Case study: ST Sibiu Proc. of the 10th Edition of WEC Regional Energy Forum - FOREN 2010, paper S3-22; [3] C. Moldoveanu, Ci. Diaconu - "On and off-line monitoring of large power transformers - a Romanian experience, Proceedings of the International Conference on Condition Monitoring and Diagnosis CMD 2006 Changwon, Korea, April 2-5, 2006, paper 408; [4] C. Moldoveanu, Ci. Diaconu, R. Ursianu, E. Ursianu E., E. Mihalcea E.; M. Nestor M.; F. Goni; L. Goia, P.G. Curiac, V. Ursianu - Determination of the optimal moments for investigating technical state of primary equipments for the purpose of assuring the safety levels - Proc. of the International Conference on Condition Monitoring and Diagnosis, CMD 2008, April 2008 Page(s): , IEEE Catalog number; CFP0830D-PRT; ISBN ; [5] C. Moldoveanu., Ci. Diaconu, C. Pop, V. Ursianu, C. Radu Expert systems for condition and maintenance assessment of HV equipment from CN Transelectrica s substations - Proceedings of CIGRE Session 2006, Report B *. * 8