Microprocessor protection relays: new prospects or new problems?

The internal architecture and principles of operation of microprocessor-based devices including so-called "microprocessor protective relays" have little in common with devices called "electric relays". But microprocessor-based relay protection devices are gradually driving out the traditional electromechanical and even electronic relay protection of virtually from all fields of power and electrical engineering. Advantages of microprocessor-based protection means over traditional ones are far from being absolute or obvious, yet this is a general trend. In reality, however, microprocessorbased protection means have several specific 12 drawbacks too. In this paper, some of these problems are discusse

BEHAVIOR OF BUSBAR DIFFERENTIAL RELAYS WITH AIR-GAP CORE CURRENT TRANSFORMERS

Protective relays normally estimate the magnitude and phase angle of current. Since the level of current is normally too high to permit a direct connection to the power system, a Current Transformer (CT) is used to scale down the current value. A CT should faithfully replicate waveform of the primary current. Power utilities normally use air-gap core and solid-core CTs. Air-gap core CTs are expensive and hard to maintain but they are able to reproduce the primary current without becoming saturated unlike solid-core CTs. Nowadays relay manufacturers claim that no matter what type of CT is used in the power grid, protective relays can intelligently sense a saturated waveform produced by a CT, and facilitates a correct decision, based on a unique algorithm. Therefore, continued use of the air-gap core CTs is being questioned. To verify relay manufacturer’s claim, behavior of protective relays when subjected to solid-core and air-gap core CT output waveforms need to be analyzed. Therefore, a mathematical model for both CT types is needed. Output waveform of a solid-core CT is already simulated by IEEE Power System Relaying Committee. In this thesis, a mathematical model of an air-gap core CT is developed and simulated on the Excel platform. Output waveform of the proposed model is then verified using the IEEE PSRC CT Simulator. Then, two commercially available busbar differential relays with CT saturation detection logic were subjected to the output waveforms of solid-core and air- gap core CTs. After testing about hundred scenarios on each relay, it is concluded that first, there is no difference in the relays’ performances for internal faults. Besides, for external faults, an air-gap core CT renders the trip output less sensitive to the relay setting. Further, the relay might be considerably slow in operation for an evolving fault, if a solid-core CT is involved

Integration testing of protection relays

This Bachelor’s thesis has been made for the research and development department at ABB Oy, Distribution Automation. The purpose of Distribution Automation products is to improve the safety, the reliability and the performance of the power distribution process. This sets high demands on product testing and verification. Integration testing is a part of the test process aimed at exposing the problems that arise from the combination of modules. The aim of this thesis work was to investigate the possibility to use SATEEN in the integration testing of protection relays. SATEEN stands for Substation Automation TEsting ENvironment and is originally designed for automated test execution in system-level testing. SATEEN is developed by ABB and only meant for internal use. Therefore there will be two versions of this Bachelor’s thesis, one for internal use only and one official version. The official version contains only theoretical information about substation automation including protection relays and product development. This Bachelor’s thesis resulted in a set of test cases that can be used for both integration and regression testing. Information about these test cases and the system under test will be presented only in the internal version of this Bachelor’s thesis.Detta ingenjörsarbete har utarbetats för forsknings- och utvecklingsavdelningen inom ABB Oy, Distribution Automation. Syftet med deras produkter är att förbättra säkerheten, tillförlitligheten och prestandan i eldistributionsprocessen. Detta ställer höga krav på testning och verifiering. Integrationstestning är den del av testprocessen som är till för att exponera de problem som uppkommer vid kombineringen av moduler. Syftet med detta ingenjörsarbete var att undersöka möjligheten att använda SATEEN i integrationstestandet av reläskydd. SATEEN står för Substation Automation TEsting ENvironment och är ursprungligen utvecklat för automatiska testsekvenser för testning på systemnivå. SATEEN är utvecklat av ABB och är endast ämnat för internt bruk. Därför finns det två versioner av detta ingenjörsarbete, en för internt bruk och en officiell version. Den officiella versionen innehåller endast teoretisk information om stationsautomation inklusive skyddsreläer och produktutveckling. Detta examensarbete resulterade i en uppsättning av tester som kan användas både vid integrations- och regressionstestning. Information om dessa tester och testsystemet finns med i endast den version av examensarbetet som är ämnad för internt bruk.Tämä opinnäytetyö on tehty ABB Oy, Sähkönjakeluautomaation tutkimus- ja tuotekehitysosastolle. Sähkönjakeluautomaatiotuotteiden tarkoitus on parantaa sähkönjakeluprosessin turvallisuutta, luotettavuutta ja suorituskykyä. Tämä asettaa suuria vaatimuksia tuotteiden testaukselle ja verifioinnille. Integraatiotestaus on osa testiprosessia ja sen tarkoitus on paljastaa ongelmat, jotka syntyvät eri moduuleita yhdistettäessä. Opinnäytetyön tavoitteena oli tutkia mahdollisuutta käyttää SATEENia suojareleiden integraatiotestauksessa. SATEEN koostuu sanoista Substation Automation TEsting ENvironment ja on alun perin suunniteltu automaattisten testisekvenssien suorittamiseen järjestelmätason testauksessa. SATEEN on ABB:n kehittämä ja on tarkoitettu ainoastaan sisäiseen käyttöön. Tästä johtuen löytyy kaksi versiota opinnäytetyöstä, yksi ainoastaan sisäiseen käyttöön ja yksi virallinen versio. Virallinen versio sisältää vain teoreettista tietoa sähköasema-automaatiosta, mukaan lukien suojareleet ja tuotekehitys. Tämän opinnäytetyön tuloksena on sarja testejä, joita voidaan käyttää sekä integraatio- että regressiotestauksessa. Tietoa näistä testeistä ja testiympäristöstä esitellään ainoastaan opinnäytetyön sisäisessä versiossa

Selection of Digital Filter for Microprocessor Protection Relays

The article considers some issues related to replacement of electromechanical relays used for protection of power facilities with microprocessor relays. One of the urgent problems connected with implementation of microprocessor overcurrent protections is how to use current transducers other than usual current transformers and in particular Rogowski coils that become more and more widespread. In the article are compared twelve methods of synthesis of a digital filter basing on the analog prototype – second-order integrating filter. The bilinear filter and Boxer-Thaler filters are analyzed in respect to their use in microprocessor relays. Basing on the research results a technique for selection of parameters of digital integrating filters for microprocessor relays is proposed. Simulation results show that Boxer-Thaler and bilinear filters have better accuracy during transient current measurements than the analog filter. The study allows concluding that in many cases the digital second-order bilinear filter is the best choice for use in microprocessor relays

Technological advance in relay protection: dangerous tendencies

In the article, the modern lines in the development of relay protection are considered: complication, increasing number of functions, use of non-determined and free-programmed logic, use of Ethernet and Wi-Fi communications channels, decreasing reliability. The article highlights the danger of the existing tendencies in relay protection development and the necessity for creation of new lines of relay protection that are independent of the current developers and manufacturers. The article calls for creation of an Expert Coordination Council of specialists for development of the general strategy and ways of relay protection.Розглядаються сучасні тенденції розвитку релейного захисту: ускладнення, збільшення кількості виконуваних функцій, застосування недетермінованої та вільно-програмованої логіки, використання Ethernet та Wi-Fi каналів зв'язку, зниження надійності. Визначається небезпека існуючих тенденцій розвитку релейного захисту й необхідність створення незалежного від розробників та виробників реле захисту експертної координаційної ради фахівців для вироблення загальної стратегії та шляхів розвитку релейного захисту

Voltage dip mitigation for motor starters using an adaptive high speed relay protection on the high voltage transmission system

Currently, the aging state of the protection systems for industrial facilities is calling for a system-wide review of the equipment and the protection schemes used in all these places, calling for a new approach in the design and implementation of these systems. Some of these facilities house critical processes that can be seriously affected by a misoperation of equipment or a disturbance in the system, aspects ranging from safety of plant workers to millions of dollars in loss of production. In this thesis different contingency situations were explored for problems in the utility transmission system that could affect large industrial facilities with continuing critical processes. Different situations were analyzed including, but not limited to, disturbances caused by momentary short circuits and different types of faults in the system. In this thesis for each scenario, one communication aided protective scheme was developed to provide the best adaptive protection to meet the needs of the industrial plant and automatically adapt and protect the industrial facility, and basically keep the electric equipment running. The developed protection scheme then was verified in comparison between one test case using digital simulation by ASPEN ONELINER and using a DOBLE power system simulator on one open loop case simulation using a real scale model with real time data acquisition

Cal Poly EE 518 Electric Power Protection Laboratory

Facing a rapidly-changing power industry, the electrical engineering department at Cal Poly San Luis Obispo proposed Advanced Power Systems Initiatives to better prepare its students for entering the power industry. These initiatives call for the creation of a new laboratory curriculum that utilizes microprocessor-based relays to reinforce the fundamental concepts of power system protection. The electric power protection laboratory (EPPL) senior project is the validation of lab manuals written for the planned EE-518 power system protections laboratory looking to be offered in Spring 2020 alongside the current lecture class under the same designation. This report evaluates the lab manual, verifies SEL relay settings, updates experiment requirements and resources, and provides feedback on improving the coursework. The microgrid integrates photovoltaics, real time simulation, and power system protection devices ensuring the future EE 518 laboratory will provide hands-on experience with power system components and operation. The experiments expose students to the capabilities of industry-standard microprocessor-based relays through hands-on procedures that demonstrate common power system protection schemes. Relays studied in this project support transformer, transmission line, and induction motor protection. This senior project and the Cal Poly microgrid project as a whole was created as an initiative by the power engineering faculty and electrical engineering department to provide additional lab course for students concentrating in power engineering