EATON ELECTRICAL
14
Predictive Diagnostics
1.3.9 Device Address and Communication Options
InsulGard has isolated RS-485 interface using ModBus RTU communication protocol
(most commonly used in industry) and can be networked to any local device network
supporting the protocol. InsulGard is shipped with the device address #1, unless
otherwise specified. The address can be changed from the keypad and set to the value
from 1 to 231. In any case, the address
must be unique
at each particular local device
network.
There are two communication options to the device from a PC for set up or to download
data. Most preferable is using a landline or cellular modem equipped with RS-485
interface. Up to 231 devices can be connected to one modem. A modem allows a user
to remotely download data and get an expert opinion on a critical situation within few
hours. Another option is using RS-485/232 converter or a device equipped with RS-232
interface to connect the device to PC directly. In this case, it would require a periodic
(monthly) connection to a device, or group of devices, connected by one RS-485
network with the converter and downloading the data into the database. In an
emergency, data from database can be e-mailed to an expert for analysis.
1.3.10 Self-test and Self-calibration
While powering up, and before each PD measurement, InsulGard performs a self-test
and calibration of PD and noise channels. In the case of a fault, an error message will
be displayed and the status relay contacts will open. Error status can be remotely
requested though interface.
1.3.11 PDI (Partial Discharge Intensity) and PPS (Pulse per Second PD pulse
repetition rate) Calculation
PDI and pulse count (PPS) are calculated for each channel at every measurement
starting from some preset magnitude zone and up. This feature allows for rejecting
background noise from affecting PDI and pulse count calculations. The low magnitude
threshold to calculate parameters can be set for each channel independently, based on
its own background noise level, if any. There are options to set these values manually
or automatically. Automatic low magnitude threshold detection could be launched only
from the keypad (usually during device start up or during initial period of operation).
1.3.12 Auxiliary Inputs
It is well known that operation conditions of monitored equipment can significantly affect
PD behavior. Correlation of PD activity changes can be used as valuable diagnostic
information for further defect type identification. In general, insulation temperature,
mechanical vibration reflected by load current, voltage on the object, and humidity of air
are some of the most valuable parameters to correlate with PD characteristics.
InsulGard has three auxiliary inputs. One of the inputs is strictly designated for
temperature. 10, 100, and 1000 Ohms RTD can be used as a sensor. This setting is
factory configured and should be specified at the time of device ordering.
