87GT Generator Transformer Protection Relay

Description

What is 87GT Generator Transformer Protection?

• The 87GT Generator Transformer Protection Relay function is a differential protection scheme designed specifically for generator-transformer units.
• It compares the current entering and leaving the protected zone. Under normal conditions, the currents are equal. If a fault occurs inside the zone, the imbalance is detected instantly, and the relay issues a trip command to the circuit breaker.

Scope of Application

• This integrated protection and measurement-control device is applicable to transformers, earthing transformers and other equipment with voltage grades below 110 kV.
• Model AGP-449 serves as a differential protection device for medium and small generator-transformer units with a capacity not exceeding 10 MW.
• It can be installed in centralized panel assembly or decentralized layout.
• The 87GT relay adopts a professional generator transformer protection scheme to realize overall differential protection for the generator-transformer unit.

How 87GT Protection Works

The differential protection of generator transformer unit continuously monitors current on both sides of the generator-transformer unit.:

• Generator side current (Input)
• Transformer side current (Output)

Working Principle of Generator Transformer Overall Differential Protection:

• Normal condition: I1 = I2 → no trip
• Internal fault: I1 ≠ I2 → relay detects differential current
• Relay issues trip signal to circuit breaker
• Fault is isolated within milliseconds

This ensures fast and selective protection without affecting the entire power system.

Protection Function

Why Choose Our 87GT Protection Relay?

• Designed for modern power system requirements
• Suitable for IEC standard substations
• Reliable operation in harsh industrial environments
• Flexible configuration for different project needs
• Strong technical support for setting and commissioning

We also provide:

• Protection setting calculation support
• Engineering design assistance
• OEM/ODM customization for projects

Common Questions (FAQ)

What is 87GT protection used for?

It is used to protect generator-transformer units from internal faults using differential protection principles.

Why is differential protection important?

Because it detects internal faults within milliseconds, preventing severe equipment damage.

What causes false tripping in protection systems?

Usually CT mismatch, incorrect settings, or poor coordination between relays.

Can 87GT work with SCADA systems?

Yes, it supports communication protocols like Modbus or IEC 61850 for integration.

What is the difference between generator transformer differential protection (87GT) and transformer-only differential protection (87T)?

87GT covers the whole generator-transformer integral set, while 87T only protects the transformer alone. The 87GT relay needs phase and ratio compensation for both generator CT and transformer CT simultaneously.

Conclusion

Contact Us

If you need technical support, relay selection guidance, or a customized solution of digital relay protection of generator transformer for your project, feel free to contact our engineering team.