See Also: Blow-up Reports
This report was written by Mike Joyce.
The Problem
The Eminence Substation had one phase that was 3 to 4 Volts lower than the other two phases.
The Cat That Caught The Mouse
At the Eminence substation the Supervisory Control And Data Acquisition (SCADA) system we have is an old Visicode system. This type of system only has one
voltage that can be observed. Since the dispatchers (see Dispatching) could only read A-phase volts there was no way they could tell that one
phase was lower than the other two. This is why it is great that we have Dennis
Cobb on the job. Dennis operates Sho-Me’s new metering system (with the help of Tom and Jim) and through his keen eyes
and intuition he noticed something strange coming out of the Eminence meter.
Dennis noticed that one phase had a voltage lower than the other two. Dennis
brought this to the attention of Max and Jeff. The ball was now in their court.
Course of Action
The sub crew went to Eminence and took an Oil sample and did a Gas check. The Relay crew went down and did a phase Angle test between voltages and check the ground for any Current. So after great thought and investigation about the only logical conclusion
to the problem was that the Transformer or the tapchanger could be having a problem. Plans were being made to send a
mobile sub to Eminence so a Doble test and ratio check could be performed on
the transformer.
A Man with Great Intuition
Ron Tracy another man with great intuition had cut his vacation short. He was
just in Time to be consulted about the problem that was occurring at Eminence. Ron
suggested that the Capacitor bank was a possible source of the problem. The dispatchers checked the
capacitor bank. At that point the capacitor bank showed an indication that all
three oil Switches were closed. Ron asked Larry Langdon if he would check the capacitor bank.
It was discovered that a lift rod in one of the oil switches was broken. The
lift rod would not let the contacts close but would let the oil switch
indicate that the switch was closed.
Conclusion
In future substations when we have a phase voltage higher or lower than the
other two phases. One of the things that we can do to try and alleviate the
problem is to open the capacitor bank oil switches. This might only happen every
once in awhile so if we can imbed this into the back of our brains. Then
sometime down the road this may save all the time and effort of sending mobile sub
down the road.