Conference Agenda

This paper presents a new approach for protecting microgrids based on multi-agent systems and using the angular variation of currents. The multi-agent system was structured using a congregation organization with three agents: section agent, circuit breaker agent, and switch agent. In this proposal, section agents are located at the microgrid lines, obtaining the difference in current angles between the buses. Then, if a threshold is reached, it sends a trip signal to the circuit breaker agent. This agent is responsible for receiving the trip signals and determining the correct line to be isolated. Finally, the switch agent is responsible for monitoring the microgrid operating scenario and updating the adequate thresholds of the agents. The proposed method was assessed firstly using simulations in PSCAD. Next, the multi-agent strategy was embedded into a low-cost microcontroller unit and tested through hardware-in-the-loop (HIL) experiments using the Real-Time Digital Simulator (RTDS). The experimental and simulation results indicated the feasibility of the proposed method.

New grid elements such as Voltage Source Converters (VSC) and cables are being increasingly used in today’s power grid. These new grid elements behave differently compared to synchronous machines and overhead lines during transients and faults, impacting the present system’s legacy protection. An increased share of underground cables affects the system’s resonance frequencies whereas VSCs introduce actively controlled current phase shifts during short-circuit faults. Existing research mainly focuses on VSC impacts on phasor-based legacy protection. This paper studies the impact of these new grid elements on incremental quantity-based directional protection, which operates in the time domain, using EMT-type models and hardware experiments. First, cables introduce low frequency oscillations for remote, single phase faults and additionally under weak grid conditions. At low frequencies, these oscillations are not filtered out by the protection, which may result in a decrease of dependability margin (23% of the tested cases) and potential security issues. For the majority of studied cases, the relays worked correctly. Second, fast reactive current injection by a VSC can cause malfunction of incremental quantity protection. Malfunction occurred in 1 case and a decrease of dependability in 10% of the tested cases. This is especially problematic for grids with relatively low synchronous infeed.

Transient-based earth fault protection is widelyused in all types of resonant grounded networks, and thoughthe operating principles of the commonly available relays areusually derived from radial networks, manufacturers claimapplicability in meshed networks as well. This paper utilizesa laboratory setup to study the directional indication of fourtransient earth fault relays in non-radial resonant groundednetworks. Two of the relays considered are widely used analogsingle-purpose transient earth fault relays, whereas the other tworelays represent two transient-based earth fault functions foundin modern protective devices. The paper verifies the locationof crossover points according to the presented theory, i.e. faultlocations for which relays transition between seeing faults asforward and reverse faults, and demonstrates the viability ofthe proposed theoretical analysis of crossover points. However,presented analytical formulae only describe the two analog relaysaccurately, whereas the two modern relays have a more complexoperating principle which requires further analysis to quantifyproperly. Finally, it is shown that relay misoperation which isnot easily fixed by communication between relays can occur, andit is suggested that network operators conduct detailed relaycoordination when applying transient earth fault relays insteadof relying on standardized settings.

Due tothe unavailabilityof asuitablerelay for microgrid protection,various utilities are fitting available IEDs for the protection of microgrids. At present,microgrid protection is achievedusing a combination of conventional numerical relays. These numerical relays are not suitable for all kinds of microgrid architecturesand do not provide complete protection with inverter-based generators. Since these relays were designed considering the fault characteristics of synchronous generators, they fail to respond to the fault characterized by inverter-based generators. This paper proposes a new protection techniquethat is independent of the type of generating sources, control philosophyof inverters as well asmicrogrid architecture. Simulations are performed using PSCAD/EMTDCand performance of the protection scheme is also evaluated in real-time usingRTDS. Pertinentresults are presentedwhich demonstratethe effectiveness of the proposed scheme.

Detecting and recognizing the secondary arc extinction is considered as a backbone of the single pole auto reclosing schemes. This paper proposes a multi-channel convolutional network to detect the secondary arc extinction during in a long AC power transmission line arc fault. In contrast to the conventional methods, the proposed Machin learning-based method can automatically learn the features from the raw data given as input. Multivariate time series data of phase voltage, current and neutral reactor signals were used as the input to the proposed model. The features are extracted in the convolution layer instead of using hand-crafted feature extraction like most of the existing research. The softmax classifier is used to detect the fault and secondary arc extinction. Matlab Simulink is used to simulate the test system and collect the dataset to evaluate the proposed neural network model. To verify the generalizability of the proposed architecture datasets were collected at different locations and different phase lines. The proposed algorithm was able to detect the secondary arc extinction with 98.26% accuracy and able to give signal for auto-recloser logic with the maximum window length of three cycle. The result shows that the proposed neural network architecture is accurate and robust to detect the secondary arc extinction further can be used as a signal for a single pole adaptive auto recloser scheme.

This article investigates the use of the distance function to protect shunt reactors. For this purpose, mho phase comparator is assessed. To carry out a comparative evaluation, the distance function performance was further compared with the differential function performance. Moreover, the Alternative Transit Program (ATP) was applied to model an electrical system, in which the reactor is subjected to different faults, including phase-to-phase, phase-to-ground, turn-to-ground and turn-to-turn faults. The performance of the evaluated distance function was also investigated against the number of turns involved and the leakage factor. From the results obtained, it is suggested the joint use of the distance function with the differential protection, because if the differential function does
not operate, distance function would guarantee the operation for internal faults, including turn-to-ground and turn-to-turn faults, increasing reliability of protection scheme for shunt reactors.
Also, the present study may serve as a guide for further studies, for example, that evaluate the use of distance function to protect iron-core reactors.