NETA Journal's

Insulation Resistance Testing: How Many Megohms Does it Take to Start a Motor?

All of us in the electrical service industry test the winding ground insulation resistance of machines such as motors and generators. A frequent question is: What is the minimum acceptable megohm value for this winding? Fortunately there is a standard that identifies minimum values for insulation resistance of rotating machines.

Tech Quiz #83 - Motors

You perform a polarization index on a generator winding. The polarization index test result is 1.1. How would you evaluate its condition?

Partial Discharge Testing of Rotating Apparatus

Statistics indicate that up to 37 percent of rotating equipment failures occur due to stator insulation breakdown. For several decades, partial discharge (PD) testing has been a very beneficial tool for assessing the stator insulation condition of medium-voltage rotating apparatus.

What's Wrong with this Picture?

You are to filter the oil on a 13.2 kV primary transformer. After starting the work the following photo is taken of the high side section. What’s wrong with this picture?

Step and Touch Potentials

For theoretical considerations, "true earth" can be viewed as a conductor deep in the ground, one with virtually no resistance. With this understanding,
ground resistance can be thought of as the resistance between, say, a ground mat or substation grid and true earth.

OSHA Releases New Subpart S

The Occupational Safety and Health Administration (OSHA) has released a new Subpart S (Part II) of the 29 CFR Part 1910, Electrical Standard General Industry Electrical Installation regulation as a Federal Register dated February 14, 2007. This document will become federal law effective August 13, 2007 (see Figure 1).

ATS07 to Begin Process of Becoming ANSI Standard

The need for acceptance testing of electrical power systems is very clear to those with extensive startup and/or operating experience. Shipping and installation damage, field and factory wiring errors, manufacturing defects, and systems and components not in accordance with drawings and specifications are some of the many problems that can be detected by appropriate testing.

New Techniques for Dynamic Relay Testing

In part 1, the following four problem areas experienced by utilities that have tried dynamic relay testing were presented.

Testing for Corrosive Sulfur Effects

Over the past several years there have been a number of failures of power transformers and reactors where there are indicators of copper corrosion and formation of copper sulfides on conductors and insulating materials.

Interchangeability of Drawout Circuit Breakers in Switchgear Assemblies

One of the key features of switchgear assemblies using drawout circuit breakers is the interchangeability of circuit breakers within an assembly.

Critical Maintenance for Circuit Breakers

Circuit breakers aren't much fun. They don't do a whole lot; just open contacts and close contacts. Pretty boring. However, if a breaker doesn't operate when it's supposed to, life can get very exciting!

World Class Maintenance

As maintenance departments have become major cost centers within industrial plant organizations, more management attention is being applied to reducing maintenance costs while maintaining operability and reliability.

News that’s NETA

NETA's Board of Directors smiled for the camera in the midst of the activity at PowerTest 2007.

Circuit Breaker Lubrication in the Field


There have been many circuit breaker failures attributed to lack of lubrication or improper lubrication. Many of these failures have lead to arc-flash incidents that have damaged equipment or injured personnel. 

What's Wrong With This Picture

You walk up to a padmount transformer that was connected by others, and notice the following conditions.

Taking Lockout Too Far

Until recently I didn't think you could take a lockout program too far. How wrong I was! On a recent trip to Indonesia I met an electrical engineer who told me a story about a medium-voltage equipment failure that occurred during a normal lockout procedure.

Tech Quiz #80 - Low Voltage Power Circuit Breakers

Low-voltage power circuit breakers are virtually everywhere. These devices are a critical part of the protective system but are often overlooked and much abused. Even though they are so critical, many equipment owners know almost nothing about them. How much do you know?

Corona Imaging — See the Invisible

It felt like a fine spring morning in eastern Oregon as my colleague and I rolled up the power plant driveway, although the date on my Blackberry indicated mid-February. After some friendly greetings and hand-shaking with maintenance personnel, we signed in at the control room and viewed the not too lengthy or boring safety video.

Tables, Labels, and HRCs

When using the NFPA 70E, do you understand the tables in Article 130 and how they are intended to be used? Do you apply the parameters
of the tables properly? Let's discuss the tables, the labels, and the Hazard/Risk Categories (HRCs). There are two factors in the tables to
consider, the hazard and the risk.

Hidden Hazard in CT Shorting Blocks

There was a hospital with a fairly new 15 kV main switchboard. Installed in their main switchboard was a basic power meter. You know the type - amperes, volts, kW, and PF.

Winter Answers - Manhole Mystery

There is a worker in this manhole doing a cable splice. Based on what you can see, what's wrong with this picture?

Case Studies in On-Line and Off-Line Motor Analysis

Current signature analysis (CSA) has become the standard for detecting broken rotor bars by analyzing the sidebands around line frequency.

The No-Outage Testing Matrix

Although no-outage inspections can be very valuable tools, always remember to comply with proper safely guidelines when conducting
the energized "on-line" inspections.

Maintenance Catch 22: The Aging Workforce Meets the Skills Shortage

Maintenance and reliability careers, like many manufacturing positions, suffer from an "image" problem and fail to attract Generation Y workers. These and other factors are creating a rapidly expanding maintenance skills shortage.

Safety Grounding

Safety is the first and paramount consideration in virtually all electrical applications. Fortunately, properly certified consumer goods (to UL?, for
example) and building wiring (if in conformance to the National Electrical Code?) make safety concerns second nature in everyday contact.