Drawing on its vast experience in voltage divider design and manufacturing, CONDIS’ damped capacitive-resistive divider (CR Divider) offers a proven and future proof solution for high bandwidth and transient voltage measurement on HV networks.
Electrical energy is a product and, like any other product, should satisfy the proper quality requirements. If electrical equipment is to operate correctly, it requires electrical energy to be supplied at a voltage that is within a specified range around the rated value. A significant part of the T&D equipment in use today, especially power electronics used for instance in renewable energy installations, often causes distortion of the voltage supply in the installation, because of its non-linear characteristics. This means, such equipment draws a non-sinusoidal current when a sinusoidal supply voltage is applied.
Furthermore, certain types of switchgear can cause high voltage transients in the electrical grid, leading to elevated electrical and thermal stresses to existing installed equipment in the MV and HV grid. Such elevated stresses, which are out of the nominal solicitation range, can cause reduced lifetimes of the over-solicited equipment, thus, reducing overall reliability of the electrical grid.
Measuring these distortions and high frequency phenomena in an electrical substation or generation installation is a challenge for conventional instrument transformers, especially in a high voltage installation. Inductive VTs are known to have resonance frequencies as low as some hundred Hz or a few kHz (the higher the nominal voltage, the lower the resonance frequencies). This means, conventional VTs can not be reasonably used for power quality measurement or transient monitoring in an HV or EHV environment.
Therefore, CONDIS SA developed damped capacitive-resistive dividers (CR Divider), also called a series-damped capacitive divider, for use in MV & HV substation installation. These types of dividers are typically used as impulse voltage dividers for high and highest voltages in HV laboratories. Damping resistors are integrated into the divider column in series with the capacitor stacks. This concept helps to suppress internal oscillations otherwise occurring at high frequencies in the pure capacitive divider. Combining this damped divider technology with standardized external HV design for instrument transformers, CONDIS proposes high accuracy measurement devices, so called low power voltage transformers (acc. IEC 61869-11), that can measure precisely from subharmonic frequencies up to several hundred kHz, as well as impulse voltages and travelling waves.
Article written by Dr. Thomas Heid, Product Engineering Manager at CONDIS
