What is electrical power system relay protection coordination study? The electrical protection coordination study is a study or analysis to determine the proper setting of protection relay and circuit breaker. Its main purpose is to obtain an optimal compromise between protection and selectivity. The study includes determining fault clearing time and coordination of upstream electrical protective equipment. Proper coordination and disruption clearing times can help reduce damage to electrical equipment and protect workers from harm. Study and analysis of coordination of protection equipment is one part of the electric power systems study. Protection coordination analysis studies is carried out after a load flow study and short circuit study is carried out. Protection system coordination studies are usually carried out using software such as Easypower, PPS, ETAP, SKM, and so on. —Omazaki Engineering is a consultant who provides electrical power system relay protection coordination study, analysis, validating or evaluation throughout Indonesia and South East Asia. Contact us if you need protection relay coordination analysis and study consultants by sending an email to cs@omazaki.co.id or filling in the form in contact.
Introduction
The coordination study determines the extent of coordination of overcurrent protection devices in the electrical system. It also provides an analysis of all possible operating scenarios that will be or have been affected by proposed or completed additions or changes to the system.
- Selective Coordination
Determines the type of protection equipment, characteristics, settings, or rated current rating that provides the correct selective coordination, equipment protection and interrupt rating for the bolted circuit of short circuit current available at the point of application for each overcurrent protection device. - Interrupted Coordination
Determines the type of protection equipment, characteristics, settings, or ampere rating that allows the non-coordination range of the overcurrent protection device. In this case, the coordination of the overcurrent protection equipment may be impaired because of the selected or installed overcurrent protective device or to achieve the protection of the selected or installed equipment.
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Why is It Important to Conduct Protection Coordination Studies?
Electrical power systems usually use fuses and circuit breakers to protect electrical equipment such as cables, transformers, motors, and other components. If there is a fault in the equipment, usually a short circuit, it is recommended that the fault only affects that part of the system where the fault occurs. If a disturbance in a piece of equipment turns out to be affecting the entire system then something is wrong.
Suppose a factory has a short circuit fault in the electrical load which is relatively far from the main distribution panel. However, this disturbance caused the main breaker to trip and ended up with a blackout. It should only be the circuit breaker closest to the fault point that trips. This is the case that often occurs in electrical distribution systems with protective equipment that are not well designed and coordinated. This is where the study of protection coordination in electrical system is important.
Facilities with the correct protection coordination scheme can save you money in reducing the effects of blackouts.
In addition, a protective coordination study is also needed to ensure the safety of personnel and the general public. Also, it is to ensure that equipment is not damaged in a fault condition according to the requirements of established standards. The study includes the determination of fault clearing time and coordination of electrical protection devices. Proper coordination and proper fault clearing times can help reduce damage to electrical equipment and protect workers from harm.
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Purposes and Objectives of Protection Coordination Study
The objective of the power system protection coordination study is to verify that all protective equipment in the system such as relays, breakers, fuses, etc., are properly coordinated and are sized according to the protected equipment.
The benefits of a protective equipment coordination study include:
- Improved system and facility reliability
- Reduces the cost impact of a disruption
- Improved equipment protection
- Increased operating efficiency
- Assist in operations and help prevent unnecessary downtime
- Prevent damage by identifying underrated equipment
- Prevent breakdown by identifying overloaded equipment
In a properly coordinated system, protective equipment is selected and adjusted to minimize the impact of equipment interference in a system. A coordination study analyzes the characteristic curves of the fuse and breaker and compares them to each other on a log-plot similar to the one shown in the following figure. Any areas of miscoordination will be visible with overlapping curves from various devices.
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How to Conduct Relay Protection Coordination Study?
Reference Standard
- IEEE 141 – Recommended Practice for Electric Power Distribution and Coordination of Industrial and Commercial Power Systems
- IEEE 242 – Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems
- IEEE 399 – Recommended Practice for Industrial and Commercial Power System Analysis
- IEEE 241 – Recommended Practice for Electric Power Systems in Commercial Buildings
- IEEE 1015 – Recommended Practice for Applying Low-Voltage Circuit Breakers Used in Industrial and Commercial Power Systems.
- IdEEE 1584 – Guide for Performing Arc-Flash Hazard Calculationsl
- ANSI C57.12.00 – Standard General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers
- ANSI C37.13 – Standard for Low Voltage AC Power Circuit Breakers Used in Enclosures
- ANSI C37.010 – Standard Application Guide for AC High Voltage Circuit Breakers Rated on a Symmetrical Current Basis
- ANSI C 37.41 – Standard Design Tests for High Voltage Fuses, Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches and Accessories.
- NFPA 70 – National Electrical Code, latest edition
- NFPA 70E – Standard for Electrical Safety in the Workplace, latest edition
Study Steps for Protection Equipment Coordination
The protection coordination study consists of the following steps:
- Short circuit study
- Data collection – In addition to the data collected for short circuit studies, additional information on the settings and current ratings of all protective devices is required.
- Manufacturer data – Each protective device has unique response characteristics, documented on the manufacturer’s “time-moment curve” required for the study.
- Computer analysis – Although protection coordination studies can be done by hand, it is much easier to use computer software available in the market. Many programs have time-current curve libraries for most of the devices found in the power system. Those that are not in the library can be entered and saved for future use.
- The computer program then allows the technician to determine the optimal settings that will provide the best protection for the system. In some cases, coordination between two devices is not possible. Engineering assessments are then used to determine the most appropriate arrangement that will minimize equipment damage.
- Results tab – Settings and ratings of each protective device (circuit breaker, fuse, motor controller, etc.) as determined by the analysis, are put in the table for comparison with the setting and current field values.
- Final report – A detailed report describing the scope of the study, all assumptions, data origins (including current-time curve), tabulated results, and recommendations for corrective action are published at the end of the study.
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Contact Omazaki Engineering if you are looking for electrical power system and device protection relay coordination study analysis, validation, evaluation and review consulting services from a professional consultant to assist your new or existing project in Indonesia and South East Asia.
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Related Articles:
- Power System Study & Analysis
- Load Flow Study & Analysis
- Short-Circuit Study & Analysis
- Motor Starting Study and Analysis
- Power System Transient Stability Study
- Harmonic Study and Analysis
- Arc Flash Study & Assessment
- Power Quality Study & Assessment
- Voltage Drop Study & Analysis
- Voltage Imbalance (Unbalance) Study
References:
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