General Electric - Substation Transformer Auxilary Cooling

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General Electric - Substation Transformer Auxilary Cooling

General Electric had a problem. They were selling an auxiliary heat exchanger for substation transformers, but the control system just could not perform as desired. Their “Version 1” control system consisted of a custom designed and proprietary hardware and software solution that was limited in functionality and difficult to upgrade, maintain and configure. The product’s sales manager was frustrated because he knew that he could sell more systems if the functionality were improved. He was familiar with Dr. Serdakowski’s work, and invited Dr. Serdakowski to present a proposal to General Electric’s engineers. The proposal was accepted, and the rest is history.

This example demonstrates Dr. Serdakowski’s abilities to design a control system. In addition, Dr. Serdakowski prepared a computer simulation of this problem that is used by both GE design engineers and GE sales engineers. The details of the simulation are discussed at the bottom of this page.

Substation transformers are large devices (see image to the right) that weight tens of thousands of pounds (empty). They are filled with tens of thousands of gallons of heat transfer fluid. Although they are typically 99.8% efficient in the transforming of electricity from one voltage to another, processing hundreds of Mega Volts-Amps of electricity force the liberation of hundreds of BTUs per second. Overheating of a multi-million dollar transformer will shorten its life span. The addition of an auxiliary heat exchanger to take additional heat out of the heat transfer fluid is a cost effective method of extending the life and capacity of the transformer. Caution is advised however, since cooling the heat transfer fluid too much will result in a change of state with the fluid becoming conductive. GE markets this auxiliary heat exchanger under the name TransCool, and these units cost less than $100,000, a small fraction of the cost of a new transformer.

The industrial computers from SmallPC running Windows XP Pro were selected for the hardware. Advantech ADAM modules were selected for the analog to digital converters. The AutoControl application framework was selected for the software. AutoControl has four components. General Electric’s implementation of these components (named TransCool) is as follows:

Configure

The Configure program will run on any Windows computer (laptop or desktop). Before launching Configure, the process engineer establishes a phone link with the TransCool computer using standard Windows networking protocols.

Upon startup, the Configure program requires a password:

The main screen:

An unlimited number of TransCool units can be configured from this software. The top half of this screen manages the units and the transmittal of configuration data to and from the units. The bottom half controls the configuration. Note how configuration is a simple as “fill in the blanks”.

The Analog Input screen controls the calibration of up to 16 analog inputs. Dr. Serdakowski is a fan of a 6 point polynomial calibration scheme he developed. It proved to be quite helpful in the 11th hour when GE engineers realized that the flow meter was not linearized, and the 6 point scheme was able to compensate.

The Alerts screen allows the process engineer to specify the value of three critical parameters that would initiate a Fax of voice message to one or more recipients.

The Utilities screen allows the process engineer to change the password as well as generate a Microsoft Excel document that contains all of the configuration information.

This is a screen shot showing a fraction of the configuration report.

The Data Retrieval screen provides a simple and intuitive way of retrieving data from the TransCool computer over a low-bandwidth connection. Reports are generated as a Microsoft Excel workbook that includes tables and graphs:

Control

The Control program runs 24x7x365 on the TransCool computer. The user interface includes the ability to toggle between manual and automatic mode, and three different strip chart recorders.

WatchDog

The WatchDog program runs in the background. It occupies very little screen “real estate”. It assures the Control program is running correctly and updates the Control program when necessary.

Guardian

The Guardian has no user interface. It runs periodically and checks to assure both the Control and Watchdog programs are running correctly.

Computer Simulation of the TransCool process

Dr. Serdakowski prepared an Excel spreadsheet that simulates the temperature of a transformer with and without a TransCool attached to it. This model is used as both a simulation tool to help GE engineers better understand the effects of a TransCool. The model is also used by GE sales engineers to explain to the customers how the TransCool unit reduces the temperature of the transformer and extends the life of the transformer.

This is the input screen. The GE engineers enter the parameters for the transformer to be evaluated in the yellow boxes.

This output shows the temperature profile experienced by an unprotected transformer and transformers protected by 3 different TransCool systems. Note that in this case, only the TransCool 150 is large enough to maintain the temperature of the transformer within the desired operating range.

This graphic by itself is quite noisy and requires some explanation. It is from a PowerPoint presentation and was designed to be displayed 1 image at a time with a verbal description to accompany each step.

The substation transformer has a TransCool heat exchanger attached to it.

A series of temperature probes generate 4-20 milliamp output signals which pass through an Advantech ADAM analog input module.

An embedded Windows XP Pro computer records the temperatures and signals an Advantech ADAM relay module to operate a series

of switches that control pumps, fans and local alarms.

Three software programs written by Dr. Serdakowski assure 24x7x365 operation.

The embedded computer can be accessed remotely by an engineer running a fourth program to configure operation and download performance data into Excel.

The embedded computer will also send out periodic and emergency emails, faxes and phone calls.

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This web page was last updated at 04/30/2014 01:15 PM and is written in EXCEL!

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