The ICMmonitor has an easy-to-use push-button interface to navigate on-screen menus displayed on an embedded LCD panel. The LCD modes include a monochrome phase-resolved PD pattern display for classification of defects, a scope-like display showing charge pulses as a vertical line at the phase angle where they occur, a time trending display, and a monitoring display showing bar graphs of two key partial discharge quantities (Qp and NQS). Qp is the apparent charge value of the PD activity, and NQS is the absolute discharge current obtained by integrating the discharge values (summing up the total charge moved and dividing by the time interval, Q/t = [As]/[s]).
The ICMmonitor features various noise handling techniques. The noise gating module can be connected to an antenna or a current transformer to sense and remove noise without losing significant PD data. Another method available is simple windowing, that suppresses phase-stable pulses occuring in the defined wiondows. Additionally, an appropriate choice of external preamplifiers can limit PD acquisition to a frequency band with less background noise.
Alarms and Trending
Users can set alarm levels of NQS or Qp that will trigger when those values are exceeded. A triggered alarm will appear on the LC display and activate an output relay of the ICMmonitor that can be used to drive a local alarm system. The ICMmonitor also collects and displays PD data over a specified time interval for easy trending and observations of changes in the Qp and NQS levels in the monitored system. Optionally, up to eight DC signals such as temperature or load can be added to this trending.
Observing the frequency spectrum of a harshly disturbed PD signal allows the selection of frequency bands with fewer disturbances. Using this center frequency for a PD acquisition, gives a largely improved signal-to-noise ratio resulting in a clear pattern acquisition. The combination of spectrum analyzer and PD detector within one instrument greatly expands the measurement possibilities when analyzing the insulation systems in a noisy environment.
The ICMmonitor with spectrum analysis comes with a four- or eight-channel multiplexer to directly select the input signal. The instrument provides five different display modes as well as a variety of connectivity options including TCP/IP and USB.