Page 7 - GuardII+ Series 4208 Platform EV User Manual

Introduction

NOTE:
A GuardII+ EV card is a component of larger system, and requires a
GuardII+ Series 4208 Platform to function. GuardII+ EV cards are not
compatible with original GuardII monitors and original GuardII EV cards
are not compatible with GuardII+ monitors.

NOTE:
A GuardII+ monitor can only support one EV card, although that card may
include other monitoring technologies.

1. Introduction

1.1. Application

The GuardII+ EV card is an optional add-on for the GuardII+ Series 4208 Platform
continuous on-line monitor that is used to measure endwinding vibration (EV) activity in motor
and generator stators. This system collects and analyzes vibration data from accelerometers,
providing maintenance staff with a tool to collect and trend endwinding and support system
vibration conditions.
The GuardII+ monitor computes vibration amplitudes and phase across the important
frequency range. Once configured, the monitor requires no user intervention, will alert when
significant vibrations are detected, and is ideal for fingerprinting and trending the vibration as
the endwinding and support system loosen and age.
On-line measurements require the permanent installation of accelerometers on the stator
endwinding to measure the structures vibration spectra. The EV sensors used by GuardII+
are application specific fiber optic accelerometers developed to be immune to strong electric
and magnetic fields and work in high temperature conditions. The sensors come in single or
dual-axis configuration allowing users to monitor radial, tangential, and axial directions.
The optical signal from the sensor is converted to an electrical signal via an electro-optical
driver (EOD) which is independent of the sensor and located in a NEMA4X enclosure external
to the machine. This increases system reliability as the EOD can be directly accessed for
repair/calibration with no machine disassembly.
In the case of hydrogen-cooled machines, the sensor leads are routed out of the machine
through a hermetically sealed feedthrough penetration. This hydrogen penetration kit consists
of a penetration that can support up to 16 individual fiber-optic cables and is pressure tested
to 400 PSI using nitrogen gas. Depending on the number of sensors installed, multiple
penetrations may be required.

In general, EV sensors should be located according to the level of concern for any area of
the endwinding which can be practically evaluated based on the results of off-line impact
vibration testing (also known as “bump testing”). Typically, phase connections and jumpers
see more significant vibrations and are thus sites of concern. In addition, sensors should be
installed on chosen coil ends and connections circumferentially around the endwinding to
detect global patterns of vibration.

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