Wednesday, May 4, 2016

Smart Motor Operators Make Better Sense When Replacing Old Disconnect Switches

Electrical generating substations have hundreds of aging disconnect switches. Many motor operators have reached the end of their useful life and need to be replaced. Instead of replacing them with the same 40 year old technology, engineers should consider replacing them with smart motor operators. Smart motor operators are grid friendly, much more efficient, safer, and mitigate some of the more common problems in substations, namely bounce, knocking, arc flashing, and maintaining contact pressure.

Bounce
Different makes and designs of air break disconnect switches provide their own level of bounce in their operations. From minor bouncing on high quality switches, to major bouncing on poorly designed air breaks. The problem can be so bad that entire structures oscillate causing major concerns to their users.

Knocking
There are some disconnect switches designs that do not have an efficient speed reducing mechanism and allow the isolators to knock hard into the jaw while closing, most likely several times, before moving into the contact fingers. As a result, the air break and insulators undergo undesirable vibrations and movement, and in some situations, knocking shortens the contact finger lifespan.

Electric Arcs
Large electric arcs are produced on high voltage switches during operation, injecting undesirable harmonics into the grid, tending to damage the power transformer’s solid insulation. This undesirable arc also causes early degradation of the main switch contacts causing pitting and wear.

Optimal Contact Pressure
Positioning of traditional motor operators typically use cam switches, which are very difficult to adjust, provide inadequate position precision and poor reliability. Overtime they tend to misalign, resulting in a and gradual change in closing position and causing the motor operator to stop outside the optimal closing range. This adversely effects the contact quality which causes overheating resulting in damaged the main contacts.

A better solution to traditional motor operators - the “smart” motor operator.

One manufacturer, EHT of  Boucherville, Canada, offers their IMCC Smart Motor Operator, a smart and robust motor operating mechanism for controlling and monitoring disconnect switches. It offers variable speed control, real time and condition based monitoring, alarm notification, IEC 61850/DNP3 communication, and optical positioning.

The IMCC, significantly reduces (or completely removes) bouncing. By configuring and fine-tuning the system to work with a given design, the IMCC Motor Operator neutralizes the various forces that occur during operations like compression, resistance and slack. The forces are neutralized by using smooth acceleration and deceleration along with precise position measurement.

Knocking is virtually eliminated through the IMCC’s variable speed capabilities by reducing speed before entering the jaw. Additionally, the variable speed controller reduces arcing time typically by over 50%.

With a smart design such as the IMCC, cam switches are replaced with an easy to configure, robust optical positioning system. Because of the optical controls, optimal positioning and contact pressure is assured, protecting the contact fingers from overheating, and more importantly, averting problems from the mechanism stopping in the middle of an operation due to a faulty cam alignment.


For more information, contact:
Arjay Automation
1178 E. Cliff Road
Burnsville, MN 55337-1577
Phone (800) 761-1749
Fax (612) 861-4292
www.arjaynet.com