Transient Limiting Device for Power Distribution Feeder Protection
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Solution Overview
Problem
Low-voltage network power distribution systems face damage and failures during backfeed, particularly due to arcing single line-to-ground faults, leading to multiple insulation failures and microprocessor network protector relay failures, which hinder efficient fault repair and system reliability.
Innovation Solution
A network primary feeder self-protected transient limiting device is introduced, which limits high transient overvoltages by inserting resistance into the zero-sequence network of primary feeders, preventing insulation failures and reducing relay failures through controlled grounding and surge arresters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistance is inserted into the zero-sequence network to limit transient overvoltages, then insulation failure prevention is improved, but device complexity increases
Solution Approach 1:
A transient limiting device is introduced as an intermediary component connected to the zero-sequence network of the primary feeder. This device includes resistors and switches that are activated during fault conditions to limit transient overvoltages, thereby preventing insulation failures without requiring complete system redesign
Solution Approach 2:
The device changes the electrical parameters of the zero-sequence network by inserting resistance during transient conditions. The resistor value is specifically calculated to limit the transient overvoltage magnitude, transforming the network's impedance characteristics dynamically to protect insulation while maintaining normal operation
2Reliability
If transient overvoltages are limited during arcing faults, then relay failure reduction is improved, but loss of time for fault detection increases
Solution Approach 1:
The transient limiting device is pre-configured and connected to the system before faults occur. The switches are normally open but ready to close instantly when fault conditions are detected, and the resistors are pre-positioned to be inserted into the circuit, eliminating setup time during actual fault events
Solution Approach 2:
The device provides beforehand protection by having the transient limiting components ready in advance. The resistors act as a cushion against transient overvoltages before they can cause relay damage, and the control system is pre-programmed to detect and respond to arcing fault conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents multiple insulation failures and reduces failures in microprocessor relays, allowing for quicker fault repair and maintaining system reliability by mitigating high transient overvoltages during arcing faults, thus minimizing downtime and operational costs.
Implementation Method 1
limits high transient overvoltages due to arcing single line-to-ground (SLG) faults on a primary feeder by inserting resistance into the zero-sequence network
Implementation Method 2
equipped with a grounding switch, and surge arresters to clamp transient overvoltages
Data Source
AI summary
A device is presented for use in power distribution networks, for limiting transient overvoltages during backfeed on a network primary feeder whose feeder breaker is open and whose network protector fails to open. The device is self-contained and self-protecting, and limits the transient voltages due to an arcing single line-to-ground fault by inserting a resistance into the zero-sequence network of the primary feeder. Limiting transient overvoltages reduces damage to and prevents failures of various network components, and in particular, prevents multiple insulation failures during backfeed and reduces failures during backfeed in microprocessor network protector relays on the secondary side of network transformers whose protectors are open. In addition, the device reduces transient overvoltages associated with re-energizing a network primary feeder by closing the station breaker when all network protectors on the feeder are open, as occurs when restoring a network primary feeder that has been out of service.