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In this paper simulation studies have been conducted using Simulink/MATLAB software in order to investigate the impact of STATCOM on the positive-offset mho element loss of excitation (LOE) protection scheme in synchronous generator. The obtained results show that the operation of the positive-offset protection scheme takes more time under the integration of STATCOM in the transmission line. Moreover,...
Evaluation of relay misoperations provides an opportunity to improve the design of backup protection schemes. Existing generator station backup protection schemes use distance protection (21) or voltage controlled/restrained overcurrent protection (51V) elements for clearing phase faults that are not cleared by either line protection or generator protection. Many schemes also use transformer ground...
Offshore platforms have critical and isolated electrical power supply system including large direct-online motors connected to the generation bus. This paper discusses complications involved in applying protection systems including generator and generator-transformer differentials in coordination with motor starting and motor protection for such applications. Recommendations are provided for applying...
Conventional distribution networks are mostly radial and are fed by central sources located at the transmission level. The power flow direction in these networks is unilaterally from sources to load feeders. In recent years, to meet the growth of demand, there has been an upward trend in the integration of distributed generation (DG) units to distribution networks. Although, the connection of DG units...
A three phase synchronous machine is one of the critical and important equipment of power generating unit used in captive, co-generation and indipendent power plants(IPPs) in verious ratings. To protect the generator against power system abnormilities or fault within itself, it needs quick isolation from rest of the system for maintaining stability in power system. As generators are associated to...
This paper describes a system for development and testing microgrid control and protection functions in a realistic controller-in-the-loop real-time simulation environment. The method presented in this paper utilizes high resolution time domain models for distributed energy resources and their primary controllers interfaced with supervisory microgrid controllers and protection relays either through...
This paper is a case study outlining the successful Power System Study (PSS) of the electrical distribution system at a century-old paper mill. The electrical distribution system has been upgraded over the years with six in-house generators controlling the steam pressure and flow throughout the plant. Three generators operate at 13 800 Volts, and three generators operate at 2400 Volts. The self-generation...
This paper evaluates the dynamic behaviour of a system with different scenarios of generation and loads considering renewable distributed generation. The impact on protection subsystems and islanding detection is assessed in time-domain disturbance simulations that lead to islanding situations. Specifically, the simulations will be dedicated to model the dynamic behaviour of the system with Wind Power...
This paper analyses the existing protection scheme of a real distribution system with distributed generators, in Greece. Network protection utilizes three successive reclosers at the main trunk and fuses at the laterals. The generating units are protected by overcurrent and voltage/frequency relays. The analysis focuses on the fault-ride-through capability of the generating units and proposes the...
Study on use of UFLS scheme in the prevention of voltage collapse on Nigerian 330 kV network. The network was modelled using PSS/E. Three simulation cases were considered: case one determined the network convergence status, case two considered AC contingency study to see the network weak points and case three dealt with the situation of voltage collapse as occurred on the grid on 27th May, 2013 and...
Our work focuses on the European Network Code on Emergency and Restoration (NC-ER) which introduced an harmonization requirement of Under-frequency Load Shedding (UFLS) schemes. This new requirement implies that in the medium term, the UFLS scheme of all European countries will have to evolve. It stipulates an acceptable range for the main factors that define an UFLS scheme, namely: the number of...
In order to have proper operation of the “relay” protection devices, their behavior shall be studied and tested for different possible operational conditions. The harmonic spectrum in the supervised circuits may affect the protection functions. Harmonics can be generated in the primary circuits by faults, non-linear loads, converters, etc. Harmonics can also be induced in the secondary circuits by...
Interest has recently grown in efficiently analyzing unstructured data such as social network graphs and protein structures. A fundamental graph algorithm for doing such task is the Breadth-First Search (BFS) algorithm, the foundation for many other important graph algorithms such as calculating the shortest path or finding the maximum flow in graphs. In this paper, we share our experience of designing...
Synchronous Resonance (SSR) is a phenomenon in which electrical energy is exchanged between generators and transmission systems below power frequency. It can be caused due to interaction of a series compensated transmission line with a generator; in addition, results in oscillation in the shaft and power swing. SSR causes increasing the magnitudes of voltage and current consequently occurrence of...
Transmission and Distribution (T&D) Companies tie to several generation plants and other utilities to make an electric transmission grid. Each of the interconnection facilities is governed by the Guidelines that ensure smooth operation of the Power System. However, the Interconnection guidelines are generally limited to equipment at the Point of Interconnection (POI), therefore a thorough investigation...
Introduction This paper provides detailed technical analysis of several catastrophic relay misoperations and demonstrates how to prevent them from occurring. It also provides an example of using data recorded by a relay during onerous conditions to implement a new protection scheme.
Steam turbines can be damaged upon loss of steam flow while the generator remains connected to the power system. Reverse power relays are used to detect the motoring power into the electrical machine and open the generator main breaker to prevent damage from this abnormal operating condition. The motoring power for large steam turbines can be a very small fraction of the power rating, leading to sensitivity...
Pumped storage hydroelectric (PSH) units provide protection complexity not encountered in conventional generating plants. As PSH units operate in both generating and pumping modes, attention must be given to the frequency and phase rotation presented to the relaying. In some PSH applications, additional relays and switching of VT and CT connections are applied to cope with these challenges. This paper...
Load shedding is the latest and most expensive operation action in order to prevent the loss of voltage and frequency of electricity networks. In this paper LS (load shedding) is occurred by means of four-step frequency relays and five-step frequency and voltage relays which consider the importance of loads and their priority.
This paper presents the permutation of rate of change of under frequency (ROCOUF) relay to avoid the frequency instability and voltage collapses in microgrid. When some of distributed generators (DGs) in a microgrid are disconnected from the main grid, the system may be imbalance between the power supply and the power demand, resulting in a rapid frequency decline that causes frequency instability...
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