Tap Changer Overflow Venting for Flash-Over Pressure Relief
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Solution Overview
Problem
Existing tap changer assemblies fail to effectively manage large and fast pressure increases during flash-overs, leading to potential transformer fires due to inadequate pressure relief, as conventional pressure relief devices are not capable of fully depressurizing at higher energy faults.
Innovation Solution
A tap changer assembly with a housing that includes a tap changer volume and an overflow volume, connected via an overflow assembly which allows fluid communication only when pressure exceeds a predetermined threshold, delaying pressure relief into the environment and preventing immediate over-pressure release, with additional thresholds for further pressure management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pressure relief devices are used, then pressure relief is provided at low-pressure trip levels, but they fail to fully depressurize at larger energy faults
Solution Approach 1:
The pressure relief system is segmented into multiple stages: a first pressure relief device for low-pressure trips and a second pressure relief device for high-pressure trips. This segmentation allows each device to be optimized for its specific pressure range, ensuring reliable pressure relief across the full spectrum of fault conditions without requiring a single device to handle all scenarios.
Solution Approach 2:
The system changes the pressure threshold parameter by employing two distinct pressure relief devices with different trip levels. The first device operates at a lower pressure threshold while the second device operates at a higher pressure threshold, allowing the system to adaptively respond to different magnitudes of energy faults through parameter differentiation.
2Speed
If pressure is immediately relieved outside the housing, then over-pressure is reduced quickly, but oil may be pushed out causing transformer fire
Solution Approach 1:
The overflow volume acts as an intermediary chamber between the tap changer volume and the external environment. When over-pressure occurs, it is first relieved into this intermediate overflow volume rather than directly to the outside, which contains the pressure relief process and prevents immediate oil ejection that could cause fire, while still achieving pressure management.
3Loss of time
If pressure relief is delayed, then circuit breaker has time to activate, but over-pressure may damage components
Solution Approach 1:
The pressure relief process is segmented into controlled stages with different threshold levels. The first pressure relief device activates at a lower threshold to provide initial relief, while the second device activates at a higher threshold as a backup. This segmentation ensures that pressure is relieved at appropriate moments - delayed enough to allow circuit breaker activation but with multiple safety stages to prevent excessive pressure buildup that could damage components.
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 delays pressure release to allow circuit breakers to extinguish arcs, reducing the risk of transformer fires by managing pressure through sequential relief stages, preventing oil leakage and maintaining internal pressure within safe limits.
Implementation Method 1
When the pressure in the tap changer volume is equal to or higher than the predetermined overflow pressure threshold, fluid communication between the tap changer volume and the overflow volume via the overflow assembly is enabled
Data Source
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AI summary
The disclosure relates to a tap changer assembly 100 comprising a tap changer assembly housing 110 completely enclosing a tap changer volume 10 and an overflow volume 12, respectively. The tap changer assembly 100 further comprising at least a part of a tap changer 13 located in the tap changer volume 10. The tap changer volume 10 and the overflow volume 12 are connectable to each other via an overflow assembly 16. The overflow assembly 16 is such that when a pressure in the tap changer volume 10 is lower than a predetermined overflow pressure threshold, fluid communication between the tap changer volume 10 and the overflow volume 12 via the overflow assembly 16 is prevented and when the pressure in the tap changer volume 10 is equal to or higher than the predetermined overflow pressure threshold, fluid communication between the tap changer volume 10 and the overflow volume 12 via the overflow assembly 16 is enabled. The disclosure further relates to a transformer tank assembly 300 comprising a transformer tank 30 and the tap changer 100 assembly according to the above.