SF6 Circuit Breaker Radiator Heating and Particle Trapping

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Solution Overview

Problem

Existing circuit breaker systems face challenges with sulfur hexafluoride (SF6) heating and particle trapping, particularly at low temperatures where SF6 liquefaction reduces its density, and particle contamination can lead to flashovers due to levitation by electric fields.

Innovation Solution

A unique SF6 insulated circuit breaker system incorporating a heating radiator that also functions as a particle trap, where the radiator is thermally coupled to an external heater and mounted inside the tank to radiate heat and shield particles from electric fields, preventing levitation and flashovers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If an internal heater is used to heat SF6, then heating effectiveness is improved, but sealing complexity and reliability risks increase due to required seals and welding

Engineering Contradiction:

ImproveSF6 temperatureVSAvoidsealing reliability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The heater is extracted from the SF6 tank and relocated to an external position. The heater remains outside the tank while still providing thermal energy to the SF6 gas through the tank wall, eliminating the need for seals and welding connections between the heater and tank interior.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The tank wall serves as an intermediary medium that transfers thermal energy from the external heater to the SF6 gas. Heat conducts through the tank wall material, allowing thermal coupling without direct physical connection between the heater and the gas.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If particles are allowed to settle at the bottom of the tank, then particle trapping is achieved, but flashover risk increases due to electric field levitation

Engineering Contradiction:

Improveparticle trappingVSAvoidflashover risk

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The bottom of the tank is designed as an equipotential surface, meaning it is at the same electrical potential as the surrounding structure. This eliminates electric field gradients that would otherwise cause charged particles to levitate, allowing particles to safely settle without creating flashover hazards.

Inventive Principle:

Principle #12Equipotentiality

3Device complexity

If the heater is externalized, then sealing complexity is reduced, but thermal coupling efficiency may worsen

Engineering Contradiction:

Improvesealing complexityVSAvoidheating efficiency

Core Design Contradiction:

Device complexityVSUse of energy by moving object

Solution Approach 1:

The tank wall acts as a thermal intermediary that efficiently conducts heat from the external heater to the SF6 gas. This intermediary approach maintains effective thermal coupling while preserving the benefits of external heater placement.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Direct mechanical contact between the heater and SF6 gas is replaced with thermal conduction through the tank wall. This substitution eliminates the need for complex sealing mechanisms while maintaining heating functionality through a different physical mechanism.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 system effectively maintains SF6 density for optimal arc quenching, prevents particle-induced flashovers by trapping particles at the tank bottom, and avoids the need for seals or sealing welds by externalizing the heater, ensuring reliable operation and reduced maintenance risks.

Implementation Method 1

a heating system having a heater and a radiator thermally coupled to the heater via the wall, the heater being disposed on the wall externally of the tank and the radiator being disposed on the wall inside the tank

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

the radiator being constructed to radiate heat received from the heater via the wall to the SF6 in the tank

Methodology Applied

Scientific EffectThermal radiation: Thermal Radiation

Implementation Method 3

the radiator is constructed to trap particles at the bottom of the tank

Methodology Applied

Scientific EffectElectric field shielding: Faraday Cage

Data Source

PatentUS10121619B2Circuit breaker system with heating radiator and particle trap

Publication Date: 2018.11.06 HITACHI ENERGY LTD

AI summary

A circuit breaker system has an SF6 tank having a wall, and an SF6 heating system. The SF6 heating system includes a heater disposed externally of the tank, and a radiator disposed on the wall inside the SF6 tank. The radiator is thermally coupled to the heater via the wall. The heating system is constructed to conduct heat from the heater through the wall to the radiator. The radiator is constructed to radiate the heat to the SF6 in the tank. A circuit breaker system has an SF6 tank having a wall, and a particle trap. The particle trap has a spar extending radially inward from the wall and a wing extending outward from each side of the spar. Each wing is spaced apart from the wall and forms a region having no electric field at the bottom of the tank adjacent the spar.