11- Generator Unbalance Protection—Negative Sequence Overcurrent (46) & Testing

Описание: Negative Sequence Overcurrent Protection (ANSI 46) is essential for protecting generators against unbalanced operating conditions such as phase-to-phase faults, broken conductors, and unbalanced loads.
In this video, we explain how negative sequence currents are created, why they are particularly dangerous for synchronous generators, and how they cause double-frequency rotor currents that lead to severe rotor heating and mechanical stress.
We cover the theory of symmetrical components, typical generator withstand limits based on I₂²·t characteristics, and how modern numerical relays implement negative sequence protection using both alarm and trip stages.

🔍 What You Will Learn
• What negative sequence current (I₂) is and how it is produced
• Common sources of generator unbalance:
o Phase-to-phase faults
o Open or broken conductors
o Unbalanced loads
o Asymmetrical system faults
• Why negative sequence currents are dangerous for generators
• Rotor heating caused by double-frequency (2f) currents
• Difference between stator current limits and rotor thermal limits
• ANSI 46 protection principles and operating logic
• Generator negative sequence withstands capability (I₂²·t)
• Typical alarm and trip settings for negative sequence protection
• Coordination of 46 protection with system and generator limits
• Practical testing concepts for negative sequence protection using numerical relays

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#powersystemprotection #relaytesting #numericalrelays #omicron #electricalengineering #energyprotection

00:00 – Introduction to Negative Sequence Protection (46)
00:33 – Why Generator Unbalance Is Dangerous
01:37 – Symmetrical Components Overview (I₁, I₂, I₀)
02:28 – Sources of Negative Sequence Currents
03:20 – Generator Thermal Limits & I₂²·t Concept
06:52 – ANSI 46 Protection Operating Principle
08:45 – Numerical Relay Implementation of Negative Sequence Protection
09:21 – Typical Generator 46 Settings & Coordination
13:43 – Testing Pickup Verification & Time Characteristic Testing
15:26 – Practical Testing Considerations & Common Mistakes