Fuel cells are used to generate electrical power. There are several types of fuel cells and various uses for them. It is possible, for example to construct a power plant using a plurality of cell stack assemblies that each comprises many individual fuel cells. The number of cell stack assemblies and the number of cells in each stack depends on the desired total power output.
One of the issues present in fuel cell power plants is protecting against fault conditions that would result in an interruption of power output or damage to the power plant. For example, it is necessary to detect an electrical short within one of the cell stack assemblies. Such a short may occur when there is an electrical path between at least one of the cells and the manifold that is used to distribute fuel to the cells in a cell stack assembly, for example.
The manifolds are designed to be electrically isolated from the cells of the cell stack assembly. One approach includes a layer of a polytetrafluoroethylene-based material between the cells and the manifold. Under some conditions, that integrity of that layer can be compromised resulting in an electrical path between at least one of the cells and the manifold. Another situation that can occur in phosphoric acid fuel cell stack assemblies is that phosphoric acid can accumulate at the anode cell in a manner that results in an electrical path between the cell and the manifold.
Detecting such a short is important to maintaining a functional power plant. Unfortunately, conventional fuses are not suitable for detecting such shorts. There are known fuses that include an indicator switch that is activated responsive to a current surge with an associated voltage change of at least 75 Volts. When there is a short between a single cell and the manifold of a cell stack assembly, there is often only a single volt associated with the shorting event. Therefore, conventional fuses will not provide any indication of the shorting event because the associated change in voltage is well below the threshold of the indicator switch.