Operation Of Protective Relays Research Articles

Study on Protective Relay Operation in a Power Distribution System with a Trigger-Type SFCL Using Twice Triggering Operations

This paper proposes a trigger type superconducting fault current limiter (SFCL), which consists of a switch, two superconducting modules, and two series connected current limiting resistances (CLRs), using twice triggering operations. The suggested trigger type SFCL has twice the triggering operations according to the amplitude of the fault current. However, these operations are thought to affect the operation of the protective relay in a power distribution system. According to the fault conditions that affect the operation of the protective relay in a power distribution system, the fault location was selected. With two representative fault locations, the fault current limiting and the bus-voltage sag suppressing characteristics in a power distribution system with the suggested SFCL were analyzed. For comparative studies, the operation of the protective relay due to the conventional trigger type SFCL using one CLR was additionally described.

Adaptive overcurrent protection against ferroresonance

Catastrophic equipment failures continue to occur today due to ferroresonance even though this phenomenon has been extensively studied over the past 90 years. Ferroresonance may also cause mal operation of some protective devices like overcurrent protection. Manitoba hydro network is analysed in PSCAD/EMTDC to recognise ferroresonance in case of line and plant outage. Impact of ferroresonance on mal operation of current-based protective relays is analysed. Then, an adaptive algorithm is designed in the relay to recognise ferroresonance and prevent mal operation of the relay.

Особенности релейной защиты и автоматики вдольтрассовых линий электропередачи

The article presents acomprehensive analysis of existing relay protection and automatic control systems of 6(10) kV overhead power lines laid along the pipeline route, including the basic circuits of sectioning and 10/0.4 kV substations. A procedure for selecting current cut off protection stages for power line linear parts with a single-side power supply is presented, and the choice of current protection parameters for sectioning substations on the basis of modern reclosers is substantiated in a detailed manner. The principles for designing modern systems supplying power to consumers situated along the trunk gas transmission lineroute areconsidered. The specific feature spertinent to application of relay protection equipment and operation algorithms of power line automatic controls are presented.

On the Coordination of Current Transformers and Relay Protection and Automation Operation of Electric-Power Systems in Transient Short-Circuit States

Due to the increasing number of incorrect actions of relay protection in transient processes accompanied by saturation of current-transformer (CT) cores, there is a need for developing a domestic standard for protective CTs designed to operate in transient states. The following ways to provide proper relay protection operation in transient states accompanied by saturation of CTs in operation are considered: (a) CT shedding that includes an increase in control cables’ cross sections, (b) development of relay-protection and automation algorithms based on the recognition of crash conditions in an appropriate CT transformation time interval of 2–3 ms, (c) development of relay-protection and automation algorithms with virtual CT error compensation, and (d) development and introduction of new primary-current converters. It is concluded that, for existing large power plants with installed TPX current transformers, it is advisable to use improved digital relay-protection algorithms for information processing obtained from CTs, for example, by methods (b) and/or (c).

DLR-supported overcurrent line protection for blackout prevention

Analysis of recent blackouts over the past decade has indicated overloads as being responsible for initiation and development of most large area failures. The overload occurrences have also been found to correspond especially with the overcurrent and distance protection, often causing their overfunction under allowable power system operating conditions. It is highly desired to improve the operation of protection relays for the sake of avoiding future blackout occurrences or at least lowering their scale. One of the possibilities to do so is an application of the Dynamic Line Rating algorithms into the standard overcurrent relay with the hope of ensuring safe relay behavior during overloads.The Dynamic Line Rating is usually proposed to be used for increasing the line transfer capacity by monitoring of the overhead conductors temperature and weather conditions. It is clear that one must also take into account the impact of DLR-operated line on the existing protection devices. It is required to adapt their decision-making algorithms to the new conditions, while satisfying arbitrarily established protection principles.This paper presents firstly chosen recent decade blackouts, highlighting the main causes of their formation and development process. Applicable solutions for overcurrent relay improvement are then proposed, which is followed by analyses of the new relay algorithms’ operation during allowable overloads and faults. The enhanced overcurrent relay solution introduced in this paper proved to be an efficient technique also for blackout prevention.

Research on the unbalance degree of four-circuit overhead lines on the same tower with different phase sequence arrangements

The phase sequence arrangements of multi-circuit overhead lines on the same tower, commonly used in extremely high voltage/ultra-high voltage (EHV/UHV) transmission lines, directly affects the symmetry of power transmission systems, which influence the operation of power grid and relay protection. It is difficult to achieve complete transposition of four-circuit overhead lines on the same tower because of their complex structure, and it is a practical and effective way to select a proper phase sequence arrangement to improve the symmetry of the line parameters. This paper presents an evaluation index based method for evaluating the symmetry of four-circuit overhead lines on the same tower and selecting the optimal phase sequence arrangement. First, the unbalance degrees of the single-sequence component and composite-sequence component are defined as the basic evaluation index of the symmetry of the parameters and obtained by the calculation of the line sequence parameters. Furthermore, the unbalance degree comprehensive evaluation index is constructed by the weighted sum based on the ranking of basic evaluation indexes. The weight distribution factors of various unbalance degrees are calculated according to the exponential (0,2) scale algorithm. The unbalance degree comprehensive evaluation index is used to evaluate the symmetry of transmission line parameters and select the optimal phase sequence arrangements of four-circuit overhead lines on the same tower. Finally, the optimal phase sequence arrangements for the different towers with typical structures, such as vertical, horizontal, d-type and e-type towers are obtained by using the above analysis method and verified by simulation of PSCAD/EMTDC.

Verification of the distance protection relay operation

Verification of the distance protection relay operation

A Compound Relay Protection Operation Criterion Based on Kirchhoff’s Current Law and Abnormal Data Detecting Algorithm

A compound relay protection operation criterion is proposed based on Kirchhoff’s Current Law and abnormal data detecting algorithm. The abnormal data detecting algorithm are proposed after deep research on the abnormal data properties. The current transformer status monitoring system and current phase angle detecting system is introduced. A simulation model containing different power sources and loads is established in Matlab. The simulation results show that this compound criterion can work quickly and reliably in all conditions.

A Short-Term Outage Model of Wind Turbines with Doubly Fed Induction Generators Based on Supervisory Control and Data Acquisition Data

This paper presents a short-term wind turbine (WT) outage model based on the data collected from a wind farm supervisory control and data acquisition (SCADA) system. Neural networks (NNs) are used to establish prediction models of the WT condition parameters that are dependent on environmental conditions such as ambient temperature and wind speed. The prediction error distributions are discussed and used to calculate probabilities of the operation of protection relays (POPRs) that were caused by the threshold exceedance of the environmentally sensitive parameters. The POPRs for other condition parameters are based on the setting time of the operation of protection relays. The union probability method is used to integrate the probabilities of operation of each protection relay to predict the WT short term outage probability. The proposed method has been used for real 1.5 MW WTs with doubly fed induction generators (DFIGs). The results show that the proposed method is more effective in WT outage probability prediction than traditional methods.

ENGLISH

Ferroresonance is one of the main causes of failures in electrical network. It results in increasing the magnitude of voltage and current, which causes operation of protective relays. Impedance measured by distance relay is deviated in effect of Ferroresonance; furthermore, swing behaviour of power and impedance in effect of Ferroresonance causes operation of OSB (Out of Step Blocking) element of distance relay; hence, operation of relay is blocked. In this paper, Ferroresonant states are examined in Manitoba Hydro 230 kV electrical network by means of PSCAD/EMTDC. Ferroresonance is detected by means of visual detection tools. Effect of Ferroresonance on distance relay and OSB element is analyzed. An adaptive Logical algorithm, which is based on THD (Total Harmonic Distortion) and Fr.d (Frequency deviation) measurement in time domain, is implemented in the software. Ferroresonant states are re-examined in presence of the logical algorithm in distance relay to prevent mal-operation of the relay; furthermore, stability domain boundary of voltage based on THD and frequency deviation is specified by the algorithm in the network.

An adaptive distance protection scheme in the presence of phase shifting transformer

Distance relays detect transmission line faults and their locations by measuring the voltage and the current signals. Also, phase shifting transformers (PSTs) are used to control the power flow in electrical power systems. PSTs protect transmission lines from thermal overloading, improve the stability of transmission system and control the power flow between different networks. Unfortunately, existence of PST in a transmission line vitiates the operation of protection relays by altering the voltage and current signals. In this paper, the effects of the delta–hexagonal PST on the operation of distance relays are investigated by both analytical and computational methods under different fault types and locations. Results of investigations reveal that the PST causes the distance relays to under-reach. Finally, a feasible method for eliminating the PST detrimental effects on the operation of the distance relays is presented. This method uses the voltage difference between the PST terminals to modify the operation of the distance relays. The phasor measurement units (PMUs) are used to calculate this voltage and remote signal systems are used to transfer it to the system protection center (SPC). All the simulations are conducted with electro-magnetic transient program (EMTPWorks).

Research and application of jet stream arc-quenching lightning protection gap (JSALPG) for transmission lines

Traditional lightning protection measures of transmission lines have been restricted by a variety of uncontrollable factors, and it has been difficult to achieve the ideal effect. In this paper, a novel Jet Stream Arc-quenching Lightning Protection Gap (JSALPG), based on the channeling type lightning protection method, was studied. JSALPG may be triggered to generate high-speed jet streams while its parallel gap is broken down by lightning strokes; the resulting jet stream will intensely act on the initial development stage of subsequent power frequency arc and completely extinguish the arc in a much shorter time than the operation of relay protection; thus, suppressing the “arc establishing rate” and reducing the lightning tripout rate significantly. In this paper, the operating principle of JSALPG is introduced, and the MHD model and modified Mayr arc model of jet stream arc-quenching field are developed. Relevant numerical calculations, simulations and experiments are carried out to verify the arc-quenching effect of JSALPG. Finally, the actual operation of JSALPG on a 35 kV line is analyzed, verifying the validity and reliability of JSALPG.

A Fault Detection and Classification Technique Based on Sequential Components

This paper presents a fault classification technique for transmission lines based on the fault sequence components, for fast and reliable operation of protective relays. First, symmetrical components of fault current and voltage signals are extracted. Next, the fault type is classified using the zero and negative sequences. To realize the faulted phases in ground faults, a criterion index based on the zero and negative sequences is defined. The imaginary part of the defined criterion index is used. This index is maximum in the faulted phase in single-phase-to-ground faults, and it is minimum in one of the faulted phases in phase-to-phase-to-ground faults. In addition, to identify ungrounded faults, a different criterion index using the positive and negative sequences is defined. The results show that the scheme provides a fast fault classification, without the need for a threshold to operate.

Probabilistic assessment of new time-domain distance relay algorithms

In this paper we propose novel distance relay algorithms and a new test methodology for assessing the security and dependability of protective relay operations. The proposed algorithms with a polygonal operating characteristic are based on a time-domain phase comparator and compared to an algorithm based on discrete Fourier transformation (DFT), which is considered as a classical solution in this area.Algorithms are usually tested on the worst case scenarios which purpose is to check if the algorithm would maloperate under some conditions and this kind of tests is necessary considering the enormous economic damage in case of power system blackouts. However, this approach is not enough for comparison of different algorithms if each of them passed those tests. Every comparison based on our choice of the test cases is in some way subjective and is not enough for assessment of security, dependability and average tripping time. In order to avoid a subjective selection of the simulation parameters we propose a probabilistic approach where the real frequency of some network conditions is considered using the probability density functions of the main variables measured in a real power system. The security, dependability and the relay tripping time are evaluated through a few thousand fault simulations and comparisons of the algorithms are presented in the paper. The proposed testing model can be adjusted to any transmission network if appropriate data is available.

System-Level Tests of Transformer Differential Protection Using an IEC 61850 Process Bus

The IEC 61850 family of standards for substation communication systems was released in the early 2000s and includes IEC 61850-8-1 and IEC 61850-9-2 that enable Ethernet to be used for process-level connections between transmission substation switchyards and control rooms. This paper presents an investigation of process bus protection performance, since the inservice behavior of multifunction process buses is largely unknown. An experimental approach was adopted that used a Real Time Digital Simulator and “live” substation automation devices. The effect of sampling synchronization error and network traffic on transformer differential protection performance was assessed and compared to conventional hard-wired connections. Ethernet was used for all sampled value measurements, circuit breaker tripping, transformer tap-changer position reports, and precision time protocol synchronization of sampled value merging unit sampling. Test results showed that the protection relay under investigation operated correctly with process bus network traffic approaching 100% capacity. The protection system was not adversely affected by synchronizing errors significantly larger than the standards permit, suggesting that these requirements may be overly conservative. This “closed loop” approach, using substation automation hardware, validated the operation of protection relays under extreme conditions. Digital connections using a single shared Ethernet network outperformed conventional hard-wired solutions.

Reliability of Latvian Power System’S 330 KV Substations

Abstract Substation reliability is always a topical problem. The authors consider the techniques for reliability calculation based on logical-probabilistic approach to the evaluation of electrical substation switchgear schemes and equipment at emergency situations with disconnections of individual elements of the substation equipment or false operation of relay protection and automation devices. Based on the reliability analysis made for the 330kV substations of Latvian Electric Power System, recommendations are given concerning the reconstruction of switchgear schemes for some substations

Modeling and simulation of the industrial numerical distance relay aimed at knowledge discovery in resident event reporting

In the motivation of tapping the strong potential of computational intelligence in discovering knowledge of protective relay operations using data mining, modeling and simulation of an actual industrial numerical distance relay and its recording facility are a vital requisite. This is justified by the practicality and necessity of divulging the decision algorithm hidden in the recorded relay event report using computational intelligence-based data mining. Thus, this paper studies the detailed modeling and simulation of an industrial AREVA MiCOM P441 distance relay, accommodated together with its own simulated event report recording facility. The idea is to provide the flexibility of allowing the simulated event report to have sufficiently significant depth and breadth for data mining purposes. The modeled relay has operated correctly and discriminatively in deciding circuit breaker pole(s) to be tripped in stipulated assertion times as per the Malaysian licensee’s requirements for various faults and protected zones along a transmission line. It has subsequently been validated successfully by the performance of the real field AREVA MiCOM P441 distance relay belonging to the Malaysian licensee. With the successful modeling and simulation of the AREVA MiCOM P441 distance relay and its recording facility, such subsequent works as data extraction and preparation, computational intelligence-based data mining for relay decision algorithm discovery and finally a relay analysis expert system development can certainly be executed. These subsequent applications are briefly explored as a demonstration of the benefit offered after the successful modeling of the relay.

Distance Protection of AC Grid With HVDC-Connected Offshore Wind Generators

When a transmission line close to points of common coupling (PCCs) experiences a short-circuit (SC) fault, the fast reactive power control of voltage-source converter-HVDC (VSC-HVDC) is likely to affect the protective relay operation of transmission lines. To study the performance of distance relays on an ac grid with an offshore wind HVDC network, this paper presents an apparent impedance calculation method, which utilizes the bus impedance matrix (Zbus) to calculate the impedances viewed by distance relays during a three-phase SC fault. The proposed method is used to identify the potential miscoordinated Zone 2 relays in the proposed combined ac/dc system. The analysis is verified by software simulation results. It is shown that the proposed method results in accurate impedances viewed by distance relays. It also identifies the protective device settings on the ac grid that need to be adjusted due to HVDC control of offshore wind generators.

Fault Current Behaviour of Large Wind Farms and their Protection Performance

Transmission system operation with wind generation has been well analysed for aspects like forecasting, reliability, control, power quality and fault ride through impacts following large scale integration. However, there are still no standardised protection schemes for wind farms such as those practised for the protection of conventional generation plants. Wind generators’ collective response under high penetration scenarios needs special attention especially during abnormal operations such as grid disturbances and faults. Different wind generation technologies exhibit different dynamic characteristics while compared to conventional synchronous generator plants. Network characteristics and their interaction with available wind technologies also impact fault behaviour. This paper first comprehensively reviews the integration characteristics and criteria for three different wind generator technologies connected to high voltage transmission systems. A case study in PowerFactory DigSILENT has been developed to assess and compare the fault response of wind generator technology types. For weaker interconnecting grids, protection schemes performance and relay operation are assessed for various wing turbine generator types. Various challenges and difficulties experienced are highlighted before drawing conclusions.

Fault current behaviour of large wind farms and their protection performance

Transmission system operation with wind generation has been well analysed for aspects like forecasting, reliability, control, power quality and fault ride through impacts following large scale integration. However, there are still no standardised protection schemes for wind farms such as those practised for the protection of conventional generation plants. Wind generators' collective response under high penetration scenarios needs special attention especially during abnormal operations such as grid disturbances and faults. Different wind generation technologies exhibit different dynamic characteristics while compared to conventional synchronous generator plants. Network characteristics and their interaction with available wind technologies also impact fault behaviour. This paper first comprehensively reviews the integration characteristics and criteria for three different wind generator technologies connected to high voltage transmission systems. A case study in Power Factory Dig SILENT has been developed to assess and compare the fault response of wind generator technology types. For weaker interconnecting grids, protection schemes performance and relay operation are assessed for various wing turbine generator types. Various challenges and difficulties experienced are highlighted before drawing conclusions.