EATON ELECTRICAL
12
Predictive Diagnostics
InsulGard has two Megabytes of internal flash memory for data storage allowing for its
standalone operation. When the memory is filled, the device starts replacing the oldest
data with the latest data. The rate of the memory consumption depends upon a number
of active channels, frequency of measurements, and frequency of PRPDD storage. As
an example, if all 15 channels are active for measurements four times a day and
PRPDD are stored twice a month, the device holds 17 months of the latest PD data in
its internal memory. All stored data and settings can be accessed from the keypad, or
remotely from a PC.
1.3.4 Alarms
InsulGard has two configurable alarms, Red and Yellow that connect to two C-form
relays. There are two groups of parameters that can generate an alarm. One is if an
alarm set point is exceeded (Partial Discharge Intensity (PDI) and its trend or PD pulse
magnitude and its trend). One of two, PDI or Magnitude, can be configured for alarm at
one time. The same parameter is configured for 4-20 mAmp interface output
automatically. 4-20 mAmp output provides a signal with the slope of 10% of Red Alarm
Threshold per 1mAmp. That means that Red alarm threshold corresponds to 14 mAmps
output.
Alarm set points for PDI are represented in terms of mW. Magnitude is represented in
terms of mV.
Trend is set in terms of times per year for both PDI and Magnitude. Alarm on trend is
enabled after a training period of 1/3 of the trend-sliding window.
Yellow and Red alarms operate differently. In the case of a Yellow alarm, it will appear
on the corresponding relay as received. In the case of a Red alarm, InsulGard will
initiate an additional measurement at the time of alarm, and only if confirmed, will
indicate the alarm by relay. If the Red alarm is not confirmed, the status of the alarm will
be set per the last measurement. If at any measurement the alarm status will be
reduced, InsulGard will indicate the reduced alarm status with both an alarm LED
reading and relay.
Alarm relays can operate in two modes (configurable). Relays lock in an alarm status
received at the last measurements, until the next measurement. Or a relay can operate
for a limited configurable time and then open the contacts. At the next measurement, if
an alarm status is detected, relays will hold the alarm contacts closed for the same time.
1.3.5 Trend
InsulGard calculates trend of a parameter enabled for alarm. Trend is normalized to the
value of the parameter change in times per year. Trend has two alarm thresholds,
Yellow and Red, connected to alarm relays and also to the alarm status LED at the front
panel of the device. Trend is calculated as a linear approximation of data over specified
time interval (default is 18 weeks). This 18-week time window is sliding over time while
device monitors partial discharges.
