Theory 3: Protection Relay Inputs, Measuring Transformers, and Overcurrent Protection

Описание: This lecture explains how protection relays connect to the power system and how they measure, process, and act on electrical signals. You learn how input and output ports work, how measuring transformers and sensors support protection, and how overcurrent protection is applied in real networks.

Topics covered in this video:

Input and output ports of protection relays.

Binary inputs, trip contacts, indication contacts, and LEDs.

Advantages of microprocessor-based protection relays.

Flexibility, setting groups, self-supervision, and compact design.

Measuring transformers and their role in protection systems.

Current transformers and voltage transformers for measurement and protection.

Accuracy classes, saturation effects, and safety rules for CTs and VTs.

Rogowski coils and modern sensor-based measuring technology.

Capacitive, resistive, and optical voltage and current sensors.

Use of optical sensors based on Pockels and Faraday effects.

Protection devices in medium-voltage networks, fuses and relays.

Role of overcurrent protection in distribution and transmission systems.

Instantaneous overcurrent protection principles and protection zones.

Practical setting of pickup current and safety factors.

Independent time-delayed overcurrent protection and time coordination.

Coordination of instantaneous and time-delayed protection in radial networks.

You gain a clear understanding of how protection relays interface with the power system, how reliable measurements are achieved, and how overcurrent protection ensures fast, selective, and dependable fault clearing.

This video suits electrical engineering students, protection engineers, and professionals working with medium- and high-voltage power networks.

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