The ICMmonitor is part of the Power Diagnostix ICMseries of digital partial discharge detectors. It is a compact, stand-alone instrument for evaluating the condition of medium and high voltage insulation. A built-in four-, or twelve-channel multiplexer offers scanning of three-phase systems or multiple sensors. It is used principally for permanent, continuous on-line monitoring of rotating machines, cable systems, power transformers, and gas-insulated switch gear (GIS).
Partial discharge (PD) measurements are a proven method for effective, nondestructive evaluation of electrical insulation, preventing expensive unplanned outages by detecting insulation problems before they can cause breakdowns. The Power Diagnostix ICMmonitor is a noninvasive digital PD detector for permanent installation and continuous monitoring of medium and high-voltage insulation.
The ICMmonitor has a simple push-button interface to navigate on-screen menus in an embedded LCD panel. The LCD display modes include a monochrome phase-resolved PD pattern display for characterization of defects, a scope-like display showing phase summed charge pulses superimposed with the applied voltage wave, 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 supresses phase-stable noise for certain portions of each applied high voltage wave. Additionally, appropriate choice of the external preamplifier can limit noise by detecting PD in a frequency band outside the range of the 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 sound, appear on the LCD display, and activate an output on the ICMmonitor that can be used to drive a relay for interfacing with 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 to select frequency bands with less 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 channel multiplexer to directly select the input signal. The instrument provides five different display modes and several interfaces like e.g. TCP/IP or modem for remote control and diagnosis.