Busbar Protection Scheme Research Articles

Resilient bus-bar protection scheme for DC microgrids connected to AC electric grids

ABSTRACT In recent years, there has been a growing interest in incorporating microgrids into existing electrical power networks to reduce reliance on conventional grids. This is further due to the numerous benefits of microgrids, most notably the ability to operate in either autonomous or grid-connected mode, making microgrids a highly versatile structure to incorporate intermittent production and energy storage. However, despite the many benefits, it is difficult to present resilience protection for DC bus bar to ensure the efficient operation of a DC microgrid, as there is a non-zero crossing phenomenon of DC fault current, while zero crossing phenomenon of an AC fault. Additionally, the DC bus bar has both an AC side with rectified DC and a DC line current, creating protection concerns for microgrids. To address these issues, this article proposes a novel fast fault detection scheme for DC microgrids with multiple renewable energy sources, energy storage, and loads. The scheme incorporates current and voltage sensing through current and voltage transformers, along with advanced digital relays, to detect and isolate faults on the DC microgrid. By analyzing rectified AC and DC line data, the scheme employs a differential current-based protection strategy to safeguard the DC bus bar. Validated through comprehensive fault simulations in PSS/SINCAL, the method proves effective in maintaining DC bus voltage stability and enhancing microgrid flexibility.

Novel busbar protection scheme for impedance-earthed distribution networks

Due to the vast number of substations at the distribution level and increased costs of differential busbar protection, DSOs are in search of cost-effective protection schemes for busbar protection. This includes the use of various communication-based protection schemes, such as the reverse-blocking schemes used at Stedin. However, due to impedance grounding, the single-phase-to-ground short circuit currents have small values in medium voltage impedance-earthed distribution grids. As a result, the reverse-blocking scheme fails to detect this type of fault. This paper introduces a novel distributed protection scheme based on the detection of zero-sequence components of the currents and voltages and the negative-sequence current component. The proposed scheme successfully detects single-phase-to-ground busbar faults by using the standard settings of the widely available overcurrent IEDs, and an IEC 61850 communication between them. Firstly, the detection of the zero- and negative-sequence current components is used to distinguish between a busbar and a feeder fault. Secondly, zero-sequence voltage detection is used to distinguish between the faulty and healthy sections of the busbar when the busbar coupler is opened. This also increases the proposed scheme’s reliability by avoiding miss-operation due to human errors during maintenance or testing. The grid is modeled in a Real Time Digital Simulator (RTDS), and a Hardware-in-the-Loop (HiL) simulation is carried out to test the protection scheme. The extensive simulations show the strengths and the limitations of the proposed scheme. Based on the research results, the developed protection scheme is implemented as a standard protection scheme in all of Stedin’s new distribution substations.

Reverse Blocking Over Current Busbar Protection Scheme Based on IEC 61850 Architecture

Substation Automation System (SAS) is currently in a matured state of technology that shall facilitate transformational changes from conventional protection scheme. IEC 61850 protocol is considered as the crux of digital SAS due to its multifunction features that include seamless communication, ability to integrate various intelligent electronic devices, potential for improved real-time condition monitoring, reliable protection, and control of critical electrical assets. Because the application of IEC 61850 in SAS is relatively new and has not fully implemented in many substations yet, further feasibility studies using multivendor equipment to assess its performance under different operating conditions is imperative. In this article, a practical reliable and efficient reverse blocking over current bus bar protection scheme based on IEC 61850 is implemented and tested. Also, a comparison of digital SAS and conventional protection scheme is presented to highlight the superiority of the former one. Experimental results attest the reliability and effectiveness of the proposed digital protection scheme along with the accuracy and security of transmitting data packets using sampled values and generic objective-oriented substation event communication protocols adopted by IEC 61850.

A superimposed current based busbar protection scheme using slope degree of grey incidence analysis model

Superimposed current components contain effective information, which can be employed to enhance the dependability and security of busbar protection relays. This study aims to investigate the use of the slope degree of grey incidence analysis model to design a methodology for busbar protection. A grey-based busbar protection criterion has been established to inspect the similarities of the superimposed currents measured by nearby CTs inside busbar protection zone. It is concluded that fault is internal if all of the superimposed currents are similar, otherwise, fault is external. It is shown that in all of the simulated cases, the authors’ methodology can make reliable discrimination between internal and external faults. Moreover, the results demonstrated that the protection indexes of the proposed scheme including security, dependability, sensitivity, and selectivity, are satisfactory for different conditions including fault type, fault resistance (to 500 Ω), fault inception angle, simultaneous faults, evolving faults, faults during transformer energization, CT saturation and normal operating switchings and white noise. Besides, the improvements noted in our algorithm are achieved with a low computational burden and sampling rate. Also, the scheme can be implemented in digital relays. It means that the existing busbar protection scheme can be replaced by the proposed scheme.

Integrated busbar protection scheme utilizing a numerical technique based on coherence method

A Busbar (BB) is one of the most important elements of a power system, which links a variety of elements such as generators, power transformers, transmission lines and loads. The BB fault current magnitude is very large, which has to be immediately cleared in order to minimize the failure in the power system, and to avoid the CT saturation effects. This paper presents a novel BB protection scheme based on closed-tripping characteristics of coherence coefficients computed for BB current signals. Three-phase current signals of each circuit connected to the protected busbar are measured for calculating nine cross-coherence coefficients. These coefficients are compared with each other and with a pre-determined threshold value to identify the fault location, classification and direction discrimination, as well as to differentiate the internal and external faults with CT saturation extent. The scheme is tested under different types of external and internal faults with variations of faulty phase(s), fault locations, fault resistances, fault inception angles, and power flow angles. ATP platform is used for power system simulation, and MATLAB software is applied to validate the proposed protection algorithm. The simulation results prove that the scheme is fast, where its operating time is within a sub-cycle time range, and it has the ability to discriminate between internal and external faults with/without CT saturation condition. Moreover, the numerical technique is immune to CT saturation effect, and it is simple, effective, secure, reliable, stable and feasible.

Enhanced Back Controlled Phase Fault and Earth Fault Busbar Protection Scheme using Overcurrent and Earth Fault Relays

Enhanced Back Controlled Phase Fault and Earth Fault Busbar Protection Scheme using Overcurrent and Earth Fault Relays

A hybrid intelligent busbar protection strategy using hyperbolic S‐transforms and extreme learning machines

AbstractIn power systems, busbars connect important components such as generators, transmission lines, and loads. A typical fault occurrence on the busbar may result in the isolation of faulty sections from other normally operating parts of the system resulting from differential protection operation. Although the main busbars' protection scheme is differential protection, its operation is significantly affected by magnetic saturation of the current transformer (CT), particularly during external fault occurrence or energizing power transformers. Saturation of the CT may generate a spurious differential current and is the main reason for the differential scheme malfunctioning. Previous research presented different methods to modify and improve busbars' differential protection scheme. However, there has been lack of a comprehensive study to assess the efficiency of the busbar protection scheme regarding all involved, and influencing aspects including various fault types, energizing power transformer, (high) fault resistance, fault angle (changing from 0° to 360°), and the angle of the sources. Thus, in this study, a hybrid intelligent busbar protection scheme is proposed and the effects of all these factors are investigated. The proposed strategy utilizes the hyperbolic S‐transform as a signal processing technique to extract an efficient feature that is able to discriminate internal faults from other abnormal modes, that is, external faults and inrush current under CT saturation. To obtain this goal, a learning‐based classification method known as extreme learning machines is used to classify the system conditions based on the selected features. The proposed protection scheme was found to have low sensitivity to CT saturation and noise and was able to accurately detect internal faults from half a cycle to one cycle of the power system depending on the fault resistance.

A new time domain-based busbar protection algorithm

This paper presents a new time domain busbar protection algorithm which uses current samples and their half-cycle incremental quantities to implement a fast and reliable tripping logic. The sign of incremental quantities is used to determine the fault direction and to distinguish internal from external busbar faults. Also, a differential incremental current is calculated for properly selecting the circuit breakers that must be opened to clear the fault. In order to test the proposed technique, a double-bus single-breaker busbar configuration was modeled in ATP/ATPDraw software and several types of internal, external and evolving faults are simulated. The results reveal the proposed function quickly operates for internal faults and ensures security for external faults. Moreover, the proposed approach allows a fast detection of internal faults during an external fault. Hence, although the proposed function is based on well-known fundamentals, it achieves the principal requirements for a busbar protection scheme with a high degree of adaptability and reliability for severe cases.

Sampled value‐based bus zone protection scheme with dq ‐components

This study presents a novel algorithm based on dq-components, which has been effectively used for bus zone protection. The analogue current transformer (CT) secondary signals are acquired and converted into sampled values. Then, the fundamentals of an instantaneous current-based differential protection scheme (87B) have been considered to establish the trip logic of the proposed scheme. Its performance has been validated by simulating faults on an existing 400-kV substation with a double-bus-single-breaker configuration. Moreover, a laboratory test bench has been developed to test the authenticity of the proposed scheme for various fault scenarios. The obtained results from the simulation model and laboratory prototype testify the claims of higher sensitivity during internal faults and better stability during external faults with CT saturation. The proposed scheme has been able to provide high-speed busbar protection against a wide range of internal faults. Comparative evaluation with contemporary busbar protection schemes clearly indicates its superiority.

IEC 61850-Based Centralized Busbar Differential Protection with Data Desynchronization Compensation

This paper proposes an IEC 61850-based centralized busbar differential protection scheme, in which data desynchronization between intelligent electronic devices (IEDs) leads to differential current errors. As the differential current errors could result in erroneous operation of the centralized busbar differential protection, data desynchronization should be compensated for. The main causes of data desynchronization are subdivided into measurement timing and time synchronization errors. In this paper, the first-order Lagrange interpolation polynomial is used to compensate for measurement timing errors and the voltage angle differences between IEDs are used to compensate for time synchronization errors. The centralized busbar differential protection is tested using a real-time digital simulator and IEC 61850-based IEDs, which are implemented with the MMS-EASE Lite library and Smart Grid Infrastructure Evaluation Module. The test results show that the data desynchronization compensation can significantly reduce differential current errors, and thus prevent erroneous operation of the IEC 61850-based centralized busbar differential protection.

Design and Performance Analysis of a Bus-Bar Transmission System Protection Scheme Using MATLAB/SIMULINK

Protective systems form an important part of all electric power networks, making it of major importance to study the performance of these systems. This paper deals with the design and simulation of a bus bar protection scheme using MATLAB/SIMULINK for a 132 kV section of the Karbala transmission network, which is used as a case study for the paper. A performance analysis of a three phase to ground fault is analysed within the simulated system, in which a differential relay is used as the main protection element and an overcurrent relay is used as backup protection.

Initial travelling wavefront‐based bus zone protection scheme

A high-speed busbar protection scheme based on initial travelling wavefronts is presented in this study. The aerial mode current travelling waves (TWs) across all lines connected to the busbar are calculated using Karenbauer transformation. Thereafter, the polarity and magnitude of wavelet transform modulus maximas of line current appearing after fault inception are analysed for fault zone and faulty phase identification. Its performance has been evaluated by modelling an existing 750 kV Indian substation in PSCAD/EMTDC software package. The simulation results reveal that the proposed scheme provides better stability for external faults and higher reliability in case of internal faults in comparison with conventional low-impedance busbar differential protection scheme (87B). Moreover, it remains immune to the current transformer saturation problems. In the end, comparative evaluation of the proposed scheme with the existing busbar protection schemes proves its superiority in terms of stability against external faults, sensitivity for internal faults, computational obligations, and communication requirements.

Withdrawn: Implementation of a Selective Busbar Protection scheme for a 33kV Substation using standard Directional OC/EF relays and GOOSE

Withdrawn: Implementation of a Selective Busbar Protection scheme for a 33kV Substation using standard Directional OC/EF relays and GOOSE

Numerical busbar differential protection using generalised alpha plane

This study presents a digital differential busbar protection scheme based on generalised alpha plane approach which combines the benefits of percentage differential approach and two-restrain alpha plane approach. The proposed scheme utilises one cycle current transformer (CT) secondary current signals of all the bays connected to the busbar to map the operating points on a complex alpha plane. The proposed scheme has been evaluated by modelling an existing 400 kV Indian power generating station in PSCAD/EMTDC software package. The performance of the proposed scheme has been evaluated on large numbers of cases with wide variation in system and fault parameters. In order to verify authenticity of the proposed scheme, a laboratory prototype of the proposed busbar protection scheme has been developed. From the developed prototype, CT secondary current signals are captured during internal faults and external fault with CT saturation condition. Comparison between the simulation and prototype results clearly shows the effectiveness of the proposed scheme in terms of higher sensitivity during internal faults and better stability in case of external faults. The proposed protection scheme has a high response speed (around 5 ms) and hence can be considered on par with modern busbar protection schemes.

Intelligent busbar protection scheme based on combination of support vector machine and S‐transform

Differential protection is the main protective scheme of busbar in power systems but its operation degrades during current transformer (CT) saturation conditions. In this study, the busbar differential protection scheme is improved by the addition of a new feature extracted from differential current using S-transform analysis. S-transform as a powerful signal processing technique gives a complete visualisation of the signal in both time and frequency domains. The new extracted feature as well as the magnitude of the differential and restraint currents are utilised to increase the security of traditional busbar differential protection scheme. With the addition of this new feature, distinctive regions are created in the feature space which can be separated by an appropriate classifier. In this study, the well-known classifier, i.e. support vector machine is employed to effectively discriminate internal faults from external faults. To evaluate the performance of the proposed method, a part of Iranian 400-kV power system grid is simulated in the PSCAD/EMTDC environment. The transient behaviour of CTs during saturation conditions is simulated based on the precise Jiles–Atherton model. The obtained results justify the superiority of the proposed method in terms of speed and security even in noisy conditions.

Improved differential relay for bus bar protection scheme with saturated current transformers based on second order harmonics

Differential relays security to the external faults is affected by the saturation of branches’ current transformers (CTs). In this paper, a simple scheme is proposed to enhance the security of differential numerical relay by extracting the 2nd order harmonic using Fast Fourier Transform (FFT) to produce a restraint signal to inhibit the relay operation during external faults. The operation signal of differential relay is produced by comparing the vector addition of secondary currents of branches’ CTs (differential current) with pre-set value; the restraint signal is produced by comparing the algebraic sum of 2nd order harmonic of individual secondary currents with the 2nd order harmonic of differential current. The proposed scheme is investigated using PSCAD/EMTDC simulation and tested during internal and external faults for saturated CTs. The obtained results reveal how this scheme is effective and secure to the external faults for different suggested scenarios. The proposed scheme is using the simplest technique of signal processing compared to other proposed techniques.

Hilbert–Huang transform‐based transient busbar protection algorithm

A new algorithm for busbar protection is proposed based on the Hilbert–Huang transform in this study. The algorithm decomposes currents of all lines connecting to the busbar into intrinsic-mode functions and calculates the instantaneous amplitude of the first intrinsic mode function (IMF). Then, the instantaneous amplitude is normalised to eliminate the impact of fault initial angle and transition resistance. When a fault occurs on the busbar, the initial travelling waves on head ends of the lines all have great instantaneous amplitudes; when a fault occurs on any line, the travelling wave on the faulted line is of great instantaneous amplitude, whereas the initial travelling waves on healthy lines are of small instantaneous amplitudes. Thus, through analysing the detected instantaneous amplitudes of travelling waves, a new busbar protection scheme can be constructed, which achieves a high reliability relative to other fault-travel-wave-based algorithms. According to simulation results on a 500 kV substation modelled in ATP-Draw, the graphical preprocessor to ATP-EMTP windows version, the proposed algorithm is effective in determining various types of faults.

Experimental results and technique evaluation based on alienation coefficients for busbar protection scheme

Abstract In modern digital power protection systems, statistical coefficients technique is recently used for fault analysis. An alienation technique is developed for busbar protection against all ten types of shunt faults, which may locate in busbar protection zone, under different loading levels, fault resistances and fault inception angle. It does not need any extra equipment as it depends only on the three-line currents measurements, of all feeders connected to the protected busbar, which are mostly available at the relay location. It is able to perform fault detection, fault confirmation, faulty phase selection and determine the fault location in about a half-cycle period. Thus, the alienation technique is well suited for implementation in digital protection schemes. The technique is efficient to detect current transformer saturation conditions without needing any additional algorithm. The effects of DC components and harmonics are eliminated with estimation of alienation coefficients. The proposed scheme is applied for an experimental circuit. LABVIEW program and MATLAB package are used to implement the proposed technique.

Comparison of the Operational Speed of Hard-wired and IEC 61850 Standard-based Implementations of a Reverse Blocking Protection Scheme

This paper focuses on the reverse blocking busbar protection scheme with aim to improve the speed of its operation and at the same time to increase operational reliability, flexibility and stability of the protection during external and internal faults by implementation of the extended functionality provided by the IEC61850 standard-based protective Intelligent Electronic Devices (IEDs). The practical implementation of the scheme by the use of IEC 61850 standard communication protocol is investigated. The proposed scheme is designed for a radial type of a distribution network and is modeled and simulated in the DigSILENT software environment for various faults on the busbar and its outgoing feeders. A laboratory test bench is built using three ABB IEDs 670 series that are compliant with the IEC 61850 standard, CMC 356 Omicron test injection device, PC, MOXA switch, and a DC power supplier. Two types of the reverse blocking signals between the IEDs in the test bench are considered: hard wired and Ethernet communication by using IEC 61850 standard GOOSE messages. Comparative experimental study of the operational trip response speeds of the two implementations for various traffic conditions of the communication network shows that the performance of the protection scheme for the case of Ethernet IEC 61850 standard-based communication is better.

Busbar Protection Scheme Based on Alienation Coefficients for Current Signals

In modern digital power system protection systems, statistical coefficients technique is recently used for fault analysis. An alienation technique is developed for busbar protection against all ten types of shunt faults, which may locate in busbar protection zone, under different loading levels, fault resistances and fault inception angle. It does not need any extra equipment as it depends only on the three-line currents measurements, of all feeders connected to the protected busbar, which are mostly available at the relay location. It is able to perform fault detection, fault confirmation, faulty phase selection and determine the fault location in about a half-cycle period. Thus, the alienation technique is well suited for implementation in digital protection schemes. The technique is efficient to detect current transformer saturation conditions without needing any additional algorithm. The effects of DC components and harmonics are eliminated with estimation of alienation coefficients. The proposed methodology is applied for a part of 500 KV Egyptian network. Alternative transient program (ATP) and MATLAB package are used to implement the proposed technique.