EATON ELECTRICAL
7
Predictive Diagnostics
1.2 Principles of Operation
InsulGard has 15 signal inputs (Ch1 - Ch15) for partial discharge measurement and a
noise input dedicated for noise suppression (Ch16). All sixteen inputs have identical
conditioning circuits (CC) providing signal isolation, transient suppression, and high-
pass filtering of the input signals. The frequency band of the InsulGard is from 1 MHz to
20 MHz.
InsulGard acquires PD data in the form of three dimensional phase-resolved pulse
height distribution (PRPHD) - PD pulse count as a function of pulse magnitude and
60(50) Hz phase. It has 24 (15
0
) phase windows and a magnitude dynamic range of
about 70dB, divided in 21 magnitude windows.
The data can be stored in the internal device memory in the form of three-dimensional
PRPHD matrixes and/or in the brief form of integral quantities derived from these
matrixes. Each record is accompanied by three additional correlation parameters.
Before each measurement, InsulGard performs self-calibration and self-test. If any
problem is detected, the status relay dry contacts will open and an appropriate message
will appear on the InsulGard display. Loss of power will be indicated in the same way
by opening status relay contacts.
InsulGard measures signals from signal inputs sequentially multiplexing them to a single
metering channel. Each pulse from each sensor is validated by the allowed pulse width.
In the case of non-compliance, InsulGard will not count the pulse.
After each measurement, data from all active signal channels will be compared to alarm
thresholds. If any of the Yellow threshold limits are exceeded, the Warning LED will be
turned on and the Warning relay dry contacts will close. In the case of a Red level
achieved, InsulGard will trigger additional measurement and, if confirmed, an Alarm
LED will be turned on and the Alarm relay dry contacts will close. If Red alarm is
detected, full measurement data will be stored in the memory.
PD measurements can be performed on a time schedule (up to 50 per day) or in
specified time intervals (from 1 minute to 23hours 59 minutes). Four measurements per
day are recommended.
Between scheduled measurements, the “High Alarm” feature is enabled. All signal
sensors are connected to a summation unit and further to a separate “High Alarm”
channel. InsulGard continuously searches for an appearance of high magnitude pulses
and pulse series. Magnitude threshold and repetition in series are configurable. If five
events of pulse series were detected between the scheduled measurements, InsulGard
will trigger a full PD measurement, and display an alarm, if any.
