Turbine trip due to walkie talkie interference


Thread Starter


Turbine tripped due to walkie talkie operation near the thermocouple to mA converter module in the field. What could be the solution for the same?
You have a few options:

* Shield the converter by placing it inside a metallic enclosure.
* Extend the time delay on trip circuit.
* Replace the converter with one that is immune to RF.

Good Luck

Jake Brodsky

You could have problems with shielding and/or grounding. Don't forget corrosion. Besides the potential for signal errors, some corrosion can rectify nearby radio signals. You might also try installing common mode ferrite RF traps.

Much of what I say here depends upon what band the hand held radios are working on, and what sort of thermocouple you're using. It may take one or more of these suggestions to deal with this problem. Keep in mind that thermocouple signals are pretty weak. You may find that you can improve the situation by using a different type of thermocouple.

An experienced instrumentation technician ought be able to figure out what is going on here and help you fix it.
Don't transmit with the walkie-talkie near the T/C-mA converter.

If the power of the tranmitter is high enough it's not uncommon for an improperly shielded wire pair being used to connect the converter to the turbine control system to sense a very high mA input current when a walkie-talkie is transmitting and then all kinds of unexpected and possibly trip-inducing problems can occur. One can see this when using a volt-ohm-milliamp (VOM) meter to measure a signal and transmitting with a walkie-talkie; usually the signal reading will spike briefly while transmitting, and especially when measuring mA currents with the meter

So, the first thing to check is to make sure that a properly grounded twisted, shielded pair cable was used to connect the converter to the turbine control system. Remember, the standard accepted practice is to ground the shield drain wire at one end only. This can be made more complicated if there are multiple terminations between the converter and the turbine control system, but the same practice still applies to each isolated portion of the shield: the ground wire is to be grounded at one end only.

It's also not uncommon for lengths of unshielded T/C leads or T/C extension wire to cause problems for the very same reason.

Also, check to see if the converter requires grounding or can be grounded.

Many times these "problems" can be traced to improper selection of components, usually choosing the least expensive component without considering the real-world usage and application (where walkie-talkies are routinely used, and some of them are required to be very powerful because of structural steel, distance, and obstructions).

Without really being able to see the entire installation at your site it's not really possible to say exactly what the cause is or may be. But, it's most like a cable shielding issue or a converter selection/installation issue.