In power system networks, protection must be designed so that protective relays isolate the faulted portion of the network, preventing equipment damage and operator injury, and ensuring minimal system disruption, allowing service to the healthy portion of the network to continue.
To achieve proper fault identification and fault clearance sequence, relay coordination is used. These relays must be able to distinguish between normal operating currents and short-term overcurrents caused by normal equipment operation, such as motor starting currents, transformer inrush currents, and sustained overcurrent caused by fault conditions. Power system relaying and overcurrent protection are concepts that are mutually dependent and contribute to the plant’s smooth operation. Protection coordination or protective device coordination research will include the calculation of protection relay settings as well as power system protection and switchgear such as MCB, Fuse, ACB, VCB, and so on.
As protection is a major concern in any industry, and they rely on protective devices for the same, a relay coordination study and analysis is performed to ensure that the system’s safety operations are functioning correctly and to avoid nuisance tripping. The cause of nuisance tripping is the modification of protective devices and their settings during maintenance without appropriate study and analysis.
A coordination study’s goal is to determine the characteristics, ratings, and settings of overcurrent protective devices that will ensure that the minimum unfaulty load is interrupted when protective devices isolate a fault or overload anywhere in the system. A coordination study should be carried out.
How Relay Coordination Study Services Gets Performed?
The majority of Relay Coordination Study Services, research and analysis are computer-aided. There are several computer programmes available for power system protection coordination analysis. Short circuit analysis and device time-current characteristics are examples of such programmes. The primary function of protective coordination software is to generate one-line diagrams, relay setting calculations, and time-current coordination drawings. The software will include features for modeling various protective devices and equipment damage curves, as well as storing data for future use. The device characteristics can be retrieved from the library and used for coordination studies using the software.
- Desktop or Microcomputers: This type of application requires either a stand-alone or network-connected computer with sufficient memory. In addition, a high-quality laser printer and a good graphic monitor are required. An examination of several alternatives can be conducted on a personal computer before a final solution arrives. The information can be saved on the computer for later use or verification of the calculations. The one-line drawings, TCC, and output can all be printed as part of a report. These files can also be copied and pasted into word processing documents.
- Graphical representation and Curves of Characteristics: For demonstration purposes, the one-line diagram of the electrical circuit and the device coordination curves can be displayed on the graphical monitor. This type of display aids in identifying the necessary corrections to be made before printing the diagrams or graphs.
- Single-line diagrams: For report preparation, a one-line diagram of the electrical circuit for which coordination is performed is always required. The software can be used to create a one-line diagram that includes all of the necessary devices. This method eliminates the need to deal with drawing office support for the security study.
Plot the fixed and continuous points of all electrical devices under consideration on time-current, Log-log paper. Before attempting to determine coordination, all currents must be referred to a common voltage, either primary or secondary, while plotting the time-current characteristic curves. The current that the primary fuse sees as a result of a secondary fault on a delta-wye system depends on the type of fault as well as the severity of the fault.
If the research is on a new or existing system, obtain or create a one-line diagram of the system or a portion of the system in question. The diagram should display the following information:
- Determine the behaviour of the plant/system over its entire operating range: start-up, shutdown, and accident scenarios.
- Ensure proper design and material selections, which can result in significant cost savings in plant construction (avoid overly conservative approach).
- Combination of control and plant thermal-hydraulic simulation to determine if operating problems, such as emissions, control philosophy, and so on, exist.
- A good control strategy can help you save a lot of money on your operations (avoid an overly conservative approach).
- Design and optimise components to ensure optimal system behaviour, even when the system is not in use or is in a transient state.
- Simulations are used to design and commission control systems.
- Dynamic integrated simulations will identify bottlenecks, inefficiencies, and safety risks that steady-state simulations will miss.
- Data files for a project: A database is a type of digital data storage system. The database can be designed to store all of the required device characteristics, short circuit data, and coordination data. These programmes can compute the inrush current, device settings, and project details. For analysis, the project data can be copied from one computer to another.
- Enquiry of Short Circuits: Obtain or conduct a comprehensive short-circuit study that includes momentary and interrupting ratings. It must also have inputs from every single short-circuit current source, as well as the highest and lowest anticipated fault interrupting duties. Collect the time-current characteristic curves for each protective device under consideration.
- Data repository:Programs like these come with a large data library from a variety of manufacturers. In the library are models for overcurrent relays, ground relays, static trip breakers, moulded case circuit breakers, cable damage curves, transformer damage curves, motor overloads, and reclosers.
- Data entry Engaging:It is not always possible to have data from the device library available for the selected study. If the data is not available but the equation or graphical data is, the data can be entered interactively. The data points can be entered one at a time and saved for later use.
- Scale Selection of the current:Because the study’s overall goal is to achieve time-sequenced tripping of overcurrent protective equipment, the curve of the device closest to the load is plotted as far to the left 4- by a 4-cycle graph as possible, so as not to pack the source side curves too close together. The right-hand limit of the curves represents the system’s highest short-circuit current.
- Coordination at a Glance:If selective coordination is to be achieved, the time-current characteristic curves of protective devices should not overlap, nor should the primary device of the transformer trip on inrush. The protective equipment should be configured to protect motors, cables, and system gear from overload and short-circuit states.
Coordination is TEAMWORK. In the context of protection, it refers to how the various protection devices in an electrical distribution network collaborate to achieve the common goal of power supply continuity even under the most adverse conditions of fault in the network, by isolating only the faulty portion network.
Selectivity, Stability, Speed, and Sensitivity are the four main characteristics of a good protection system. The first and most important is selectivity. It implies that, in the event of a network fault, only the protective device closest to the fault should respond first and isolate the faulty portion of the network from the healthier portions.
Benefits of employing Relay Coordination Study Services:
Relay Coordination Study Services is very important according to the Electrical safety standards and regulations to protect the downstream and upstream breakers to avoid faults in circuit breakers. This coordination study is required to reduce power system faults and successfully sequentially isolate faults.
To minimize damage to the distribution system, relay coordination studies are used in any distribution system to isolate faults in the protective system promptly. The primary purpose of the protective study is to safeguard the power system’s upstream protective devices.
The protection principle chosen affects the protection’s operating speed, which has a significant impact on the harm caused by short circuits. The faster the protection operates, the fewer the hazards, damage, and thermal stress that result. Furthermore, the faster the protection operates, the shorter the duration of the voltage dip caused by the short circuit fault.
Consequently, Undervoltage will have less impact on other parts of the network. The protection’s quick operation also reduces post-fault load peaks, which, when combined with a drop in voltage, makes the disturbance more likely to spread.
Here at SAS Powertech, we provide a wide range of Cost-effective Relay Coordination Study services.
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