Protection Coordination Studies

What are Protection Coordination Studies?

• Protective relays are very important in industrial power systems because they can prevent large losses of production due to an unnecessary equipment outage or damage occurring due to a short circuit fault or overloading conditions.

• Protection coordination is the selection and/or setting of protective devices to isolate only the portion of the system where the abnormality occurs.

• When a short circuit or an abnormal power flow occurs, the protective devices should react to isolate the problem with minimum disruption to the balance of the system. This is the objective of protection coordination studies.

What is the Importance of Protection Coordination Studies?

The main purpose of protection coordination studies is:

• To determine the optimum settings for the protective devices.

• To limit the extent and duration of service interruption whenever equipment failure, human error, or adverse natural events occur on any portion of the system.

• Minimize the damage to the system equipment involved in the failure.

• To reduce the cost of equipment damage or service interruption.

• To determine the fault clearing time and analyze the time-coordination curve.

How Do We Perform Protection Coordination Studies?

• Step-1: Data collection such as single line diagram (SLD), protective device manufacturer, type, and ratings, trip settings, circuit breaker, short circuit current at each bus, full load current of all loads, voltage rating, transformers, Current and potential transformers, lines/cables, system data, all other sources, etc.

• Step-2: Modeling the study system using PSCAD/EMTDC software.

• Step-3: Preparation of simulation case studies with the study scenarios accepted by the clients.

• Step-4: Preparation of technical report and submission to clients.

What Standards can be Referred for Protection Coordination Studies?

• IEEE Std 399-1997 - Recommended Practice for Industrial and Commercial Power Systems Analysis.

• IEEE 242™ - Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems.

• IEEE Std 3004.11-2019 - Recommended Practice for Bus and Switchgear Protection in Industrial and Commercial Power Systems.

• IEEE Std 3004.3™-2020 - Recommended Practice for Application of Low-Voltage Fuses in Industrial and Commercial Power Systems.

• IEEE Std 3004.8™-2016 - Recommended Practice for Motor Protection in Industrial and Commercial Power Systems.

• IEEE Std 3004.5™-2014 - Recommended Practice for the Application of Low-Voltage Circuit Breakers in Industrial and Commercial Power Systems.