Page 4 - Basic PD Theory

Partial Discharge for Stator Windings

Introduction

Iris Seminar – PD Investigations
ou are about to embark upon an incredible journey into the world of partial discharge (PD) testing. The purpose of
this journey is to understand how to monitor the condition of the stator winding insulation used in motors and
generators. This seminar is designed for individuals wishing to use either the PDA-IV, TGA-B, TGA-S,
Y
BusGuard, TurboGuard, HydroGuard, BusTrac, HydroTrac or PDTrac instruments to assist in that
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process. This manual is a textbook that is used as a reference for this seminar and is only intended to enable the reader to better
perform PD testing on motors and generators. The manual should not be considered a technical presentation of insulation
designs or partial discharge theories. There are a wide variety of techniques for monitoring PD, this textbook will only focus on
the methods used and marketed by Iris Power LP. For information about other methods, refer to the papers, books, industrial
guides and standards listed in the reference [Appendix H. ].
The partial discharge testing setup described here is designed to be done with the machine operational and by non-experts in the
PD fields. Thus, the test is simple to perform and the data easy to interpret enabling you to plan maintenance when needed.
The purpose of this seminar is to give you enough information to do the following:
• to understand basic PD theory
• to understand basic review procedures for PD data
• to understand additional tests that should be done to investigate PD sources
Every student should have the following prerequisites:
• Understanding of basic electrical theory
• Understanding of rotating machine components and function
• Understanding of safety issues related to working with potential electrical hazards

Maintenance Overview

Too often maintenance personnel perform exploratory surgery before they have any idea about a problem. They wait until the
machine is scheduled for an outage and then disassemble it looking for things to fix. Though a visual inspection and a battery of
off-line tests may be quite useful in ascertaining the extent of some problems, they are very costly and time-consuming to
conduct. Not to mention the fact that often more damage is done to a machine during the disassembly/re-assembly process
than if it had been left in service.
A more economical approach to machine maintenance is to periodically monitor as much of the machine as feasible during
normal operations, and only when a problem is detected, plan for a more extensive evaluation in the form of off-line testing.
And finally, only if the off-line testing establishes the requirement for a visual inspection or repairs, disassemble the machine and
conduct the exploratory surgery. In other words, plan your maintenance activities based on the condition of the machine and
not time frequency.

1 TGA, PDA-IV, BusGuard, TurboGuard, HydroGuard, HydroTrac, BusTrac, and PDTrac are products of
Iris Power LP.

www.irispower.com

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