Measurement

Up to several hundred cells are interconnected in series to form stacks, within electrolyzers and fuel cells.  Individual cells require an average operating voltage from less than 1V up to 4V DC; the stack voltages typically reach hundreds of volts. In larger systems, stacks are combined in series to create strings, with considerably higher total voltages.  The current trend suggests string voltages up to 1500 VDC.

Continuous and highly accurate measurement of cell groupings, stack, and string voltages is necessary for early detection of defects and degradation of cells.  Often, current and temperature are also monitored for these condition monitoring purposes.  To achieve these measurements, transducers must meet robust electrical isolation requirements.  This is due to the cells being arranged in a series configuration.  This means that even if measuring relatviely low voltage associated with a small grouping of cells, if the cells are part of an overall larger string, the isolation needed for the low voltage measurement needs to be at the overall potential of the entire string.  This makes measurements particularly challenging!  Transducers must also be fail-safe and maintenance-free, as plant availability depends on the reliability of the measurement technology.

Thanks to their accuracy, isolation levels, and long-term stability, Knick Interface‘s P40000 series are optimal solutions for voltage, current, and temperature measurement in electrolyzers and fuel cells. These transducers, with isolation up to 3600 VDC, achieve an MTBF of approximately 96 years, (according to EN 61709), thanks to the conservative and fully encapsulated electronics design. They are also characterized by excellent transmission properties, with an amplification error of less than 0.3% of measured value.  Like all Knick products, they do not require recalibration over their entire service life.  Many models contain the ability to configure input and output ranges specific to the application and bring additional flexibility through an onboard universal power supply.  The P40000 series is relatively small in size and mountable by way of standard din-rail, making them easy to work with in both new and retrofit applications.