Generator Set On-package Automatic Transfer Switch (ATS) Control Functionality

Getting to and from your primary utility source is an important function.  Learn of a way to accomplish that without adding cost to your system.  Feedback?  Write to us at powerbytes@cat.com.

Email us: powerbytes@cat.com
LinkedIn: https://www.linkedin.com/showcase/cat-electric-power/
Facebook: https://www.facebook.com/Caterpillar.Electric.Power/

Transcript

Lou: Good Day and welcome everyone to Power Bytes!  I am your host Lou Signorelli and Power Bytes is your destination Podcast for power generation conversations.  As always please know how much we appreciate you, our listeners.  We hope you find our topics both helpful and interesting.  We would appreciate feedback and suggestions for new topics. You can send us an email at powerbytes@cat.com, visit us at Cat Electric Power on Facebook or LinkedIn.  If you enjoy your time with us today, please leave us a 5-star rating wherever you listen to your favorite podcast; It really does help.

Lou: Today we are going to dive into a great little piece of technology that can both increase reliability and reduce costs when implemented in the right application.  That technology is called the Automatic Transfer Switch Functions or some might also refer to it as Mains Failure Transfer.

Joining me today is one of our resident application experts Mr. Bryan Snyder.  For our returning listeners you will recognize Bryan from his work on the Overcurrent Protection Podcast.  For our new listeners Bryan has 19 years of experience with Caterpillar and a career of focusing on integrated systems and gensets.  Welcome Bryan and thanks for joining us today.

Bryan: Thank you Lou,

Lou: I must say that I'm happy to be able to speak with you about how Advanced Control technologies are helping our customers.  Let's set the table; please review what has been traditionally done to transfer to and from the main supply of utility power in the past.

Bryan: All standby power systems require a means to transfer from the utility source to the emergency generator source if an outage occurs.  In most applications, an Automatic Transfer Switch or ATS is utilized to identify the failure of the primary source, request the start of the emergency source, and facilitate the transfer between sources.  While the ATS provides a critical function in an Electric Power System, the ATS drives additional cost in a system and can be a reliability concern as it can be a single point of failure in a system.

The traditional ATS is comprised of a transfer element and a controls element.  The transfer element can be a combination of breakers or a contactor based device enabling the transfer between the two sources.  Meanwhile, the control element provides the verification of available power sources, a run signal to the emergency backup system, and logic to transfer between the sources. 

Lou: Ok, that makes sense.  What does the ATS transfer function on the genset controller offer and can you share a bit about how it works?

Bryan:  The Cat EMCP 4 implements the Auto Mains Failure controls logic from the traditional ATS directly in the generator set controller.  This enhancement enables the EMCP to autonomously change the power source to the load between the utility and the generator via an open transition method. The EMCP 4 monitors the condition of the utility via a digital input to be provided by the customer.   When the EMCP receives the signal that Utility has been lost, it will automatically start the generator and send an open signal to the Utility breaker or Contact.  When the generator is up to speed it will send a close single to the generator breaker or contact.   By using the logic within the EMCP you are able to eliminate the ATS and use the breakers already within the system to control the available source. 

Lou:  Are there recommendations on how the customer should be monitoring the Utility?

Bryan: The identification of the utility failure requires the customer to monitor the incoming utility and determine when then source does not meet the desired conditions.  This can be accomplished in the simplest method using a relay to monitor the voltage at the mains side of the utility disconnect.  If this method is chosen, the minimum recommendation is to utilize a three-phase relay such that a loss of a single phase can be identified.  The customer can also choose to utilize a more complicated process with a multifunction relay to monitor various power conditions. 

Lou: So that covers the failure, what happens when the utility returns?

Bryan:  The return from emergency is also an open transition.  The EMCP 4 controls receive indication from the customer's monitoring device that utility has returned, and the generator breaker will receive a command from the EMCP and will open sending the gen into cooldown.  The EMCP will then send a signal to the utility breaker to close.  This will return utility power to the load.  

Lou: are there settings or time delays that can be applied to customize the systems operation? 

Bryan: 
Certainly, Utility to Generator Transfer Delay Time, Minimum Unpowered Load Time, Generator Ready to Accept Load Percentage & Load Delay Time, Utility Breaker Maximum Closing & Opening Time
 
Lou: Is this only available with the equivalent of a single ATS or can it support multiple transfers?

Bryan:  Complex operations can be developed to provide activation of multiple ATS or even sequence ATS loads, however these functions require additional programming and considerations beyond the standard controls configurations.  Customers should consult with their local dealers to determine if this would be a good fit.

Lou: This sounds like a great feature.  Should it work for all applications? 

Bryan:  This feature is typically recommended for simple systems as a means to transfer sources.  Complex application with detailed sequences or requirements may need a traditional ATS or paralleling switchgear.  One example is applications that require UL1008 certification.  This certification is more related to certifying the connection devices than the controls, but it considers both as a single piece.  Because the connection devices are separate products not necessarily something provided with the generator, we cannot certify our controls to meet this requirement.  This would require working with our Switchgear and ATS group to specify the right product. 

Lou: There you have it.  Thanks For joining us today Bryan and Thank you our listeners  for joining us here on Power Bytes.  For more information on this and other topics please contact your local Cat dealer or write us here at powerbytes@cat.com, visit Cat Electric Power on facebook or on LinkedIn.  Till next time; thanks for listening to Power Bytes.