Series Arc Effects (DC & AC)

A series arc can have catastrophic effects on other components / structures surrounding it. While efforts continue to develop techniques for the detection of series arcing, it is clear to aHV that the most likely scenario for detection results from the transition of a series arc to a parallel arc.

In this scenario, a series arc would generate a significant amount of local power (a 50A arc would likely produce 2kW of heat in a small area based on a 40V arc voltage). That heat would then cause damage to the local insulation system and result in the development of a phase-ground or phase-phase. We believe testing to quantify the amount of damage that could result is essential to help deliver safe high voltage systems. 

We also believe there is a need for AC testing to understand when an AC series arc will be extinguished. While this is predictable in a DC system it is less so in an AC system and the use of inverters mean the voltage waveforms present around a current zero further complicate our understanding. 

Proposed Project Scope

aHV have developed series arc test capability that is capable of at least 340A. We would like to expand this capability to ensure we can test at low pressure - this is a relatively simple change. At the same time we believe the purchase of a COTS 800V inverter system would allow for work on AC arcs that would provide clear benefit.

  • Mapping The Series To Parallel Arc Transition: Work would take a range of components provided by partners such as cable bundles, connectors and power electronic boards. These components would be fitted into a large series arc test rig that could be operated at low pressure and with currents of up to 340A. Tests would be carried out to characterise the level of damage that was done to the components before a parallel arc developed. Intended Outcome: A standard test method that would allow the measurement of the time taken for a parallel arc to develop following a series arc. As a result of this, an estimate of the energy levels that must be managed without these levels causing damage to surrounding structures.  

  • Predicting The Extinction Of AC Arcs: Modelling tells us that a DC arc in an 800V system can likely reach lengths of around 20cm (even before we consider low pressure). In an AC arc, the presence of a regular current zero is beneficial as this provides a regular time when the current can be interrupted. Whether current flow takes place after the current zero depends on the conductivity of the arc channel and whether this has reduced to a level necessary to stop the current flow. Testing would use an 800V inverter feeding a suitable active load along with an actuator mechanism to generate series arcs.  Intended Outcome: A way of forecasting the maximum length of AC arc that can be expected in higher voltage systems and as a result of this, an estimate of the energy levels that must be managed without these levels causing damage to surrounding structures following a series-parallel arc transition.

Timings

Our target timings for this project are as follows:

  • Agreement of project scope - May
  • Finalisation of project scope and costings - July
  • Project kick-off - September

Expressions Of Interest

If you would like to receive more details of this project, please contact h.jahangiri@aerospacehv.com
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