ERROR ANALYSIS AND RELAY COORDINATING IN ACCORDANCE WITH THE SMART NETWORK INFRASTRUCTURE OF A TRADITIONAL RING NETWORK
Mehmet Tan Turan, Yavuz Ateş, Erdin Gökalp, Mehmet Uzunoglu, Recep Yumurtacı, Arif Karakaş1
1 Department of Electrical Engineering
Yildiz Technical University
With the development of technology, new developments are emerging in order to provide better quality services to the consumer in the field of energy as well as in all areas. It is of great importance to take precautions against possible failures in a network, to intervene quickly, not to leave the consumer without energy. As a result of the error in traditional low voltage networks fed from one side, the consumer remains without power until the fault is repaired, while the faulty zone is isolated from the network and continues to energlyse the consumer over another line thanks to the system developed in smart networks. In this study® modeling of a ring network using MATLAB®, Simulink® and SimPowerSystems, various short circuits were created in the network and the system's response was measured. After the necessary arrangements have been made, the system has been made to ensure the continuity of energy by isolating the fault zone in any error and feeding the consumer from another line.
Keywords: Smart Networks, Ring Network, Relay Coordination
1. Error Analysis and Relay Coordination INTRODUCTION
New stations and new consumers are being added to existing networks in line with the growing energy needs today. Since the 20th century, 21st century network and computer technologies have been added to networks running on almost the same principle, creating smart grids. The components and technologies of a smart grid must include some structures, according to the Energy Department of America (DOE). These structures are composed of intelligent production, intelligent distribution, smart meters, integrated communication and advanced control methods.
Many problems are encountered in traditional networks that are already in use. The main problems are manual error detection, independent voltage regulation, unoptimized power flow and partial power management. Using smart networks, real-time error detection and remote-controlled switching perform dynamic simulations to reduce real-time power management and losses.
Modern network infrastructures are designed interconnected. Change at any point can affect a large area in a very short period of time, which can cause much more damage to the network. To solve this problem, the disadvantages of infrastructure that has become inadequate must be eliminated and improved network solutions should be offered. A reliable communication system is needed to detect and respond to possible failures in the network. To improve the reliability, efficiency and efficiency of the system, the communication system must work in the same way reliably and effectively.
As a result of the inclusion of communication in power systems, which is one of the most important subheadings of smart networks, reliable networks will be obtained. Another advantage that smart networks offer us is counter reading systems. Smart meters are predicted to be at 89% in 2012, up from 6% for home consumers in the United States in 2008. With the spread of smart meters, the energy demanded by consumers can be analyzed in more detail and smart pricing can be done. One of the most important benefits of smart networks occurs during errors in the system. With the use of systems with very fast response time, the error at some point will prevent it from affecting the rest of the network. With high-speed protection and remote control, the desired reliable results will be achieved. After error location detection is made in smart networks, various solutions are offered to ensure the continuity of energy and not to leave the consumer without energy.
In this study, a system was established and simulated for the continuity of energy for consumers in the network after the short circuit formed at any point for a ring network. After the short circuit in the system, instead of cutting the power of the entire network, only the relevant cutters were sent an opening signal and the energy continuity was provided by shutting down the cutters that were open before the error. It is accepted that the consumers connected to the network have a synchronous motor and various impedance loads. The system created in the study is modeled in accordance with the smart network infrastructure. In future studies, analyses will be carried out on the state of the distributed production facilities. In this study, selectability factor was added to the protection strategy in order to prevent the short circuit point from opening another cutter in the system with its distance to the transformer and error current values.
Following the introduction of the work carried out briefly, the system presentation in part 2 and the simulation study of the system developed, the current and voltage results showing the reactions of the system established in the short circuit in part 3, and the interpretation of these results were given in the 4th part of the study.
Error Analysis and Relay Coordination
2. SYSTEM DESCRIPTION AND METHODOLOGY
The general diagram of the system, which includes the control, control, communication and power system elements of the ring network created, is as shown in Figure 1. The system is a ring network and is fed by a and b generators.
In the event of any malfunction in the system, the system will continue to be fed by the other generator by disabling the error through cutters in the relevant area. Consumers in the system are fed through transformers located in the outputs of generators. Phase-neutral voltage changes of generators that feed consumers for normal operating situation where there are no errors in the model are seen in Figure 2 and Figure 3. As can be seen from the shapes, both generators have the same voltage level.
Impedance loads and a synchronous motor are modeled as consumers in the simulation, which is carried out to protect the power system elements in the grid against errors that will occur at any point. Relay and cutter models are used for protection structure. It is very important to intervene as soon as possible with an error that may occur in the system. After the detection of the area where the short circuit occurred, the cutters at other points and the control solutions of the cutter at the point of error should be different. Therefore, with the software developed, the cutter control is made to work as desired.
In order to test the reliability of the system, short circuits were created in various regions and the answers given by the system were examined. The regions where the predicted short circuit currents will be at the highest value are transformer output points. In this study, 4 different error scenarios were applied, including transformer outputs. The cutters used in the simulation work are controlled by external signal. Signals '1' or '0' have been sent to external entry points depending on whether the cutter is on or off. If the cutters are requested to be in an open position, the signal '0' should be applied and '1' should be applied if it is requested to be closed.
Error Analysis and Relay Coordination
The flow diagram of the generated control algorithm controls the output signal cutter as shown in Figure 4, while the input signal is obtained via the current transformer located on the distribution line. The input signal sends a signal '1' or '0' to the relevant output point according to the codes contained in the control algorithm. In order to prevent the system from entering the infinite loop after the desired signal is obtained in the control algorithm, the output signals are defined as the starting requirement over time delay. For blocks that provide time delays, the initial conditions are processed as '1' or '0' as is destened in the system.
7 different impedance loads and one a synchronous motor representing consumers were used in the simulation model of the study. Impedance loads are started from transformer outputs and placed at various points in the network. The data of the elements used in the network model is as shown in Table-1.
Table 1: Data on Elements Used in network model
|Active Power (P)||Reactive Power (QL)|
|Line Parameters||Resistance (ohm)||Indux (mH)|
|Transformers||Primary Voltage(V)||Secondary Voltage (V)|
|TR-A||13800 V (phase-phase)||400 V (phase-phase)|
|EN-B||13800 V (phase-phase)||400 V (phase-phase)|
Squirrel cage motor was used for a synchronous motor simulation. The power of the engine used is selected as 20 HP. The necessary values have been applied to the control algorithm so that the current of the motor does not affect the relays and cutters in the system. A synchronous motor input reference values are given from the Tm entry point. The TM value is provided by the unit digit block.
3. Error Analysis and Relay Coordination – TESTS AND RESULTS
The simulation results obtained by the ring network model are obtained by creating mathematical and electrical models of the components that make up the system in MATLAB, Simulink and SimPowerSystems software. The generators used in the ring network produce 13.8kV voltage. Transformers have conversion rates of 13.8kV/0.4kV.
The error blocks used in the simulation are connected to the system for 2 different points, including transformer output and away from the transformer. The time-based change of simulation results is given in the following ways, respectively.
Figure 5 transformer output as a result of short circuit change of current value is shown. The current value of the consumer before the short circuit is 20A. As a result of the short circuit occurring in 0.8 seconds, a short circuit current of 140A occurred and the cutters cut the current by opening the circuit. This arm where the short circuit occurs will be disabled until the fault is repaired.
Figure 6 shows the current graph of the consumer's nutrition from the line that did not pass the current before the short circuit, after which the cutters insulated the short-circuited area as a result of the short circuit at the transformer output. While the current value is zero before the short circuit, 20A is drawn from the line that was started to be used after the error. Feeding of the consumer in the short-circuited region has started to be provided by the other generator and a more reliable system has been obtained.
As shown in Figure 7, the voltage waveform before the short circuit moment is distorted by the effect of the short circuit in 0.8 seconds. As a result of isolating the fault zone of the cutters and starting to feed the consumer through the other generator, the voltage reached its value before the short circuit.
In Figure 8, the short circuit occurring in the system and the current-time change graph of the a synchronous engine are given. As shown in the graph, although the engine's current is up to 240A, no opening signal has been sent to the cutters. As a result of the short circuit occurring in 0.8.seconds, 0.01 seconds of current value was distorted and this distortion was corrected immediately with the feed from the other line. As shown in Figure 9, 240A current was pulled during the asenkron motor's journey, but no opening signal was sent to the cutters in the system. At the time of the short circuit, the current value has risen up to 190A, as well as figure 8. Nevertheless, as soon as the cutters in the system disabled the relevant area and supplied the feed from the other generator, the stator current graph of the a synchronous motor improved.
As shown in Figure 10, the peak value of the phase neutral voltage was at 320V until the short circuit occurred, but this value was 0V as a result of sending an opening signal to the cutters.
This area where the voltage is 0V is the area where the fault occurred and will remain isolated from the system until the fault is repaired. As shown in the general system configuration given in Figure 1, transmission will be carried out via lines without faults with any of the 2 generators in the system. As transmission will not occur in the isolated area, feeding should be made from another point so that the consumer does not go out of energy. This feature is provided as shown in Figure 11 and Figure 12.
Figure 11 shows the voltage graph of the line that started to feed the consumer. Considering the general system configuration in Figure 1, as shown in Figure 9 before the short circuit, the consumer fed with a generator started feeding from the B generator after the short circuit and the line from the A generator was isolated from the system.
As shown in Figure 12, the current passing through before the short circuit moment 0 A line after the short circuit moment began to carry a current worth 20 A.
It is clear from here that the line that feeds the consumer at the time of the short circuit was disabled and the consumer continued to be energized by feeding on another line.
4. Error Analysis and Relay Coordination RESULTS
In the study, a ring network suitable for smart network infrastructure was designed and error analyses were carried out by making the necessary simulations. When a short circuit occurs on traditional networks, the result is a power outage. Power outages negatively affect the efficiency and reliability of the system. The control algorithm is designed to minimize system negativity and increase efficiency. Thus, the faults were corrected as soon as possible and system stability was provided by coordinating the relay.
As a result of simulations and analyses carried out with the established ring network system, the system was developed by creating short-circuit and later scenarios. After any short circuit in the system, the consumer is energized from another point and the area where the error occurred is isolated. With the control algorithm created, the desired cutter was provided to work and the wrong area was prevented from being isolated. In this way, while repairing the short circuit zone, the consumer's de-energy status is eliminated. In the next study, it is targeted to provide relay coordination by adapting the production facilities distributed to the system. Thus, an important stage in the coordination of protection of smart networks will be folded.
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