EATON ELECTRICAL
17
Predictive Diagnostics
2.1.3 Noise Aspects
Noise is a major issue in any type of partial discharge measurement. Noise is always
site specific. There is not an absolute solution for noise suppression in the modern
world. However, most noise issues can be overcome. InsulGard has been designed
with several noise suppressing algorithms and, along with recommended sensors, is
able to suppress most industrial noises. While planning InsulGard installation, keep in
mind most common noise sources:
•
Power thyristor firing
•
Switching power supplies in modern metering and protective electronics
•
Arcing and sparking somewhere at the facility
•
Aerial corona on overhead lines on high voltage substation
•
Partial discharges in the adjacent equipment
•
Pulse signals coming from incoming lines and feeders
2.1.4 Device Location and Environmental Issues
InsulGard can be shipped with or without an environmental enclosure. Without the
enclosure, it can be used indoors on switchgear lineups (given a relatively clean
environment).
In most applications, indoor and outdoor, InsulGard is contained in a NEMA-4 enclosure
protecting the device from direct rain, sun, and dust. If the application environment is a
chemically aggressive medium, or a company policy requires a stainless steel enclosure
(NEMA-4X), please, specify this while ordering InsulGard. Also you may use if specified
NEMA4X plastic enclosure with a clear window.
In a switchgear lineup InsulGard can be installed without an environmental enclosure.
When planning to install InsulGard, consider a non-vibrating location, conveniently
located in a centralized position between all sensors and possible communicating
means (phone jack, tray to control room for alarms, etc.). The length of PD signal
coaxial cables (RG58 or similar, 50 Ohm) can be up to 150ft. It is preferred to keep the
PD signal cables short and uniform in length.
2.1.5 What Additional Parameters to Measure?
Several factors can affect PD level: temperature, humidity, voltage, mechanical
vibration, etc. In North America voltage commonly is not an issue. It is stable and does
not commonly affect PD. If more than +/-5% voltage variation is expected, plan
correlating PD to voltage. Temperature is very important for rotating machine
monitoring. Temperature variations can change size of voids and surface conductivity
thus affecting PDs. Humidity is also a factor for line terminals in rotating machines,
especially in an outdoor installation.
Temperature and humidity are important factors in switchgear; often affecting
contaminated surface conductivity or condensing moisture on some surfaces and
