Line Current Differential Protection Research Articles

Reference Phasor-Based Data Self-Synchronization Scheme for Line Current Differential Protection in Active Distribution Networks

Reference Phasor-Based Data Self-Synchronization Scheme for Line Current Differential Protection in Active Distribution Networks

Advancements in Line Protection for the Future Grid

Advancements in line protection provide effective protection in power systems with diverse combinations of renewable and conventional generation. These technological advancements improve grid resiliency when the power system experiences reduced fault current levels and abnormal current waveforms, which are common in networks with inverter-based resources (IBRs) such as photovoltaic, wind, and battery energy sources. The technologies described in this article include advanced line current differential protection, communications channels for protection applications, high-accuracy traveling-wave (TW) fault locating, and digital secondary systems (DSSs), also known as digital substations. This article describes the fundamental principles of these technologies.

Applying Line Current Differential Protection in Systems with Inverter-Based Resources

Applying Line Current Differential Protection in Systems with Inverter-Based Resources

Current mapping strategy for improving two-terminal series-compensated line current differential protection

This paper presents a particular case of the generalized alpha plane called current mapping strategy (CMS) formulation applied to differential protection of series-compensated transmission lines. The proposed formulation presents two unique features, control over the internal fault settlement region (FSR) and the use of an operation characteristic (OC). The FSR and the OC are two concentric circles defined on the alpha plane. Additionally, the proposed CMS allows the user to adjust the center and radius of the FSR and OC, according to the desired sensitivity and security of the protection. To validate and test the performance of the improved CMS, numerous computer simulations have been carried out using the Alternative Transients Program (ATP) on a 400 km long series-compensated, 500-kV transmission line. Furthermore, analysis of an extensive database of cases is conducted to highlight the CMS’s sensitivity. The obtained results demonstrate the effectiveness of the settings of the CMS and a smooth trajectory to the FSR. The CMS also proved to be stable and reliable even under severe subsynchronous oscillations and outfeed conditions.

Impact of Inverter Based Resources on System Protection

Inverter-based resources (IBRs) exhibit different short-circuit characteristics compared to traditional synchronous generators (SGs). Hence, increased uptake of IBRs in the power system is expected to impact the performance of traditional protective relay schemes—set under the assumption of a SG-dominated power system. Protection engineers need to study these challenges and develop remedial solutions ensuring the effectiveness of system protection under higher levels of IBRs. To address this need, this paper studies the impact of IBRs on a variety of protective relay schemes including line distance protection, memory-polarized zero sequence directional protective relay element, negative sequence quantities-based protection, line current differential protection, phase comparison protection, rate-of-change-of-frequency, and power swing detection. For each protection function, potential misoperation scenarios are identified, and recommendations are provided to address the misoperation issue. The objective is to provide an improved understanding of the way IBRs may negatively impact the performance of traditional protection schemes as a first step towards developing future remedial solutions ensuring effective protection under high share of IBRs.

Determining alpha plane characteristics of line current differential protection in two-terminal high voltage transmission with different current transformer ratio

Determining alpha plane characteristics of line current differential protection in two-terminal high voltage transmission with different current transformer ratio

The Communication System and its Impacts on Line Current Differential Protection in Distributed Feeder Automation

As one of the core technologies of distributed feeder automation (DFA), line current differential protection (LCDP) can locate faults quickly and accurately and have the ability to cope with multi-directional flow. However, LCDP algorithm has high requirements for communication speed, and is sensitive to communication quality. In order to apply the LCDP algorithm to a real project, the communication system and its impacts on LCDP need to be studied in depth. In this paper, the design method of a communication system for LCDP, including communication mode, topology, communication protocol, and synchronization, is analyzed in detail. For better parameter determination, the communication models are investigated, and the impact of time delay, data loss, and jitter on LCDP are discussed. Further, the distribution network based on a real project is built in a cyber-physical co-simulation environment, and the impact of electrical fails and communication fails on LCDP are studied. The results show that the design method and parameters determination method proposed in this paper are effective.

Revisions on Alpha Plane for Enhanced Sensitivity of Line Differential Protection

Line current differential protection based on the traditional alpha plane may block internal faults with outfeed when providing higher security for external faults under current transformer (CT) saturation. This letter proves analytically that the external faults under CT saturation plot away from the negative real-axis of the complex plane and accordingly proposes revisions of the alpha plane characteristics. The modified alpha plane enhances the sensitivity of line current differential protection by unblocking more space along the negative real-axis where internal faults with outfeed are plotted.

Investigating the impact of network security on the line current differential protection system

This paper analyses the influence of network security measures on the system behaviour of a power system protection device. In this particular case, an IP-based Ethernet protection interface of a line current differential protection system is considered. IPsec has previously been proposed to be part of the security concept of the protection interface. Therefore, the authors conduct a trade-off analysis regarding the influence of IPsec on the protection function and consequently on the system safety. This work shows that the protection function of the relay is not impaired as long as the additional CPU performance for the encryption by the protection relay is available and the necessary bandwidth on the communication channel is provided.

Design, implementation, and evaluation of secure communication for line current differential protection systems over packet switched networks

In this work we propose a secure communication concept for the protection of critical power supply and distribution infrastructure. Especially, we consider the line current differential protection method for modern smart grid implementations. This protection system operates on critical infrastructure, and it requires a precise time behavior on the communication between devices on both ends of a protected power line. Therefore, the communication has to fulfill deterministic constraints and low-delay requirements and additionally needs to be protected against cyber attacks. Existing systems are often either costly and based on deprecated technology or suffering from maloperations. In order to allow for both, economical and reliable operation, we present the first holistic communication concept capable of using state-of-the-art packet switched networks. Our solution consists of three parts: (i) we develop a list of design requirements for line current differential protection systems communication; (ii) we propose a communication concept obeying these design requirements by combining cryptographical and physical security approaches; and (iii) we evaluate our solution in a practical setup. Our evaluation shows a clock accuracy of 3 µs with a resilience to asymmetric delay attacks down to 8 ns/s. This demonstrates the secure and fault-free operation of a line current differential protection system communicating over a state-of-the-art network.

Communication Modeling for Differential Protection in IEC-61850-Based Substations

Today's power utilities, around the world, own multiple substations that are connected together to form a complex energy network. The functions within and between these substations are being automated according to globally accepted power utility automation standard IEC 61850. This automation results in efficient operation and enhanced protection of power network with the aid of the communication system. Implementing the protection schemes modeled using communication configurations of standardized information exchange will lead to digital power grid. Designing an IEC-61850-based protection scheme to take care of the faults outside the substations is a challenge, as the typical local-area-network-based generic-object-oriented substation events and sampled-value messages need to be transmitted over a wide-area network. This paper presents communication configuration for line current differential protection schemes applied between two automated substations. It presents the simulation results of communication configuration network between two substations. Its performance is evaluated using a network simulator tool. This study intends to guide the development of a robust protection scheme with IEC-61850-based communication configuration.

Accurate clock synchronization for power systems protection devices over packet switched networks

Channel based clock synchronization in packet switched networks (PSNs) is considered for, but not limited to, the time and safety/security critical application of power system protection. The synchronization accuracy requirement of power system protection devices used for line current differential protection is $$10\,\upmu $$10μs, which could be achieved in time division multiplexing networks that were traditionally used in that domain. In PSN, highly accurate synchronization can be achieved with the standard synchronization method IEEE 1588-2008 Precision Time Protocol (PTP) when devices in the communication network are equipped with so called boundary clocks (BCs) or transparent clocks (TCs). However, when BCs or TCs are not available, the required accuracy can hardly be achieved. In this work, a modification of the PTP is proposed that replaces the clock parameter estimation and the computation of the clock control signal. Thereby, the statistics of measured packet delays are considered to select optimum estimation schemes. It is shown that the here proposed method outperforms the Linux PTP in terms of timing accuracy by a factor of 2 in enterprise local area networks and by a factor of 10 in Carrier Ethernet wide area networks.

Uncertainty in Transmission Line Parameters: Estimation and Impact on Line Current Differential Protection

This paper presents a method to estimate the transmission line parameters using synchrophasor measurements from phasor measurement units (PMUs), as well as hybrid measurements from PMU and supervisory control and data acquisition system. It also proposes a method to estimate transmission line parameter uncertainties considering the measurement inaccuracies. Transmission line protection is important for secure and reliable operation of the power system. With the advent of the synchrophasor technology and advances in the communication system, current differential relays can be implemented as a reliable protection system for the transmission lines. In this paper, a new current differential protection scheme has been suggested for transmission line protection using synchronized measurements. The effect of parameter uncertainty on the protection scheme is also investigated.

Novel principle and adaptive scheme of phase correlation line current differential protection

SUMMARY Current differential protection is widely used in transmission line due to its inherent simplicity and good performance. In order to strive to increase sensitivity of protection without compromising stability on external faults, phase correlation current differential protection is presented in this paper. Current phase difference is introduced to the differential current principle so as to improve the sensitivity and reliability of differential protection simultaneously. Comprehensive analysis and comparisons of performance characteristics in Alpha Plane demonstrate that phase correlation current differential protection has preferable performance than that of conventional current differential protection. As far as CT saturation is concerned, the proposed protection scheme has flexible adaptability to ensure significant improvement in sensitivity and dependability for internal faults while still improving stability for external faults. The performance of the proposed protection is investigated for various faults of transmission line simulated by Electro-Magnetic Transients Program including DC and record fault data from real power system. The test results show that the proposed protection has satisfactory operation performance. Copyright © 2013 John Wiley & Sons, Ltd.

Phase Current Differential Protection for Transformers in Wye-delta Mode

For the current transformers (CTs) on the delta side measure the line current instead of the phase current, line current differential protection is adopted in transformers connected in wye-delta mode currently. However, the symmetry feature of inrush current in line current differential protection may invalidate the inrush current restrained criterion. A calculating method of current through delta windings according the measured current from CT is proposed in this paper. Using this calculated current, phase current differential protection can be realized. Based on the method an adaptive second harmonic restrained scheme for magnetizing inrush current is presented. The scheme not only adaptively adjusts the secondary harmonic ratio of restrained current but also guarantees the fast action when transformers with internal faults are no-load energized. Consequently the performance of transformer differential protection is greatly improved. Simulation results in Matlab/Simulink validate the proposed method. DOI: http://dx.doi.org/10.11591/telkomnika.v10i6.1413 Full Text: PDF

Influence of current transformer saturation on line current differential protection algorithms

The performance of line current differential protection algorithms during current transformer (CT) saturation is analysed. The study covers popularly used algorithms and presents their degree of immunity to CT saturation. The degree of error in phasor measurement due to CT saturation is estimated through simulation studies and this information is used to decide the CT dimensioning for the relay.