Proceedings Volume Cover
6200 North Central Expressway  
Dallas, Texas 75206  
SPE 2088  
Fifty Years of Supervisory Control  
Paul W. Schirmer, Quindar Electronics, Inc., Springfield, N. J.  
common trip and close pushbuttons generally are  
used to open or close the breaker, transmitting  
separate code different from a select code.  
Supervisory control apparently got its  
start sometime about 1920. According to  
It is hard to tell how many of these sys•  
available history on the subject, an engineer  
from a switch gear builder attended an AIEE  
meeting in March, 1920. At that time most of  
the electric utility sub-stations were under  
automatic control, and the young engineer was  
questioned about the adequacy of this. He  
admitted that it had some shortcomings and also  
that remote control equipment could be devel•  
oped patterned on telephone switching circuits.  
One customer at the meeting stated that this  
was just the kind of equipment his system  
needed and asked when he could get some. This  
put the wheels in motion; the switch gear  
builder contacted an independent telephone  
builder, and the first supervisory system was  
developed. At approximately the same time,  
another switch gear builder also went to an  
independent telephone manufacturer and, borrow•  
ing some of their techniques and eqUipment, came  
tems were built over the years, but they were  
numerous, and they have provided excellent  
service. Many of them are still in operation.  
until less than 10 years ago, the super•  
visory control business moved along practically  
unnoticed; then, the advent of solid state  
techniques began to disturb it. Solid state  
techniques employ a continuous scanning prin•  
ciple in generating the codes that transmit the  
information from one station to another. In  
generating these discrete codes certain error  
detection methods can be used to provide greater  
security. When  
code, the code generally is repeated until  
channel is clear and the information is  
received. The receiving station is thus up•  
a blast of noise eliminates a  
dated. In some of the older quiescent systems,  
a message could be obliterated by noise blast;  
because many remote units of this early design  
did not speak more than once, the information  
was permanently lost. Using the scanning  
principle, supervisory designers were able to  
develop larger systems in which one master  
station could handle many remote stations. In  
this case, it would be basically an interroga•  
tion scanning system whereby the remote sta•  
tions are normally quiescent but the master  
station sequentially interrogates each remote  
for a message to transmit. If there is one,  
up with  
similar system. Each could be  
select check-before-operate  
described as  
system, operating in  
a quiescent mode.  
quiescent system has no parts or cir•  
cuits in motion when at rest. In this kind of  
point may be addressed either from the  
master station, where the address is set up by  
momentarily operating the select key, or from  
the remote station, where the breaker trips the  
it sends  
a complete scan of station information  
auxiliary switch contact, delivers  
a signal to  
to the master. The master then moves to the  
next remote requesting the same information.  
This process continues and repeats until all  
remote stations are pollen and any transmitted  
information is updated in the master.  
the supervisory, and generates an address that  
is transmitte-d to the master station. The mas•  
ter station then puts the point number in stor•  
age and confirms the address code back to the  
remote station. Then the remote station trans•  
mits the new status or indication to the master,  
updating the point escutcheon. When the  
address is generated at the master station, the  
point escutcheon starts the master station in  
motion; the address is transmitted to the remote  
station, put in storage, and reconfirmed to the  
master station creating the select check opera•  
tion. To control the operation remotely,  
Illustrations at end of paper.  
Because solid state techniques made  
quiescent systems virtually obsolete, these  
systems will be retired for the purposes of  
this paper. Also, in the larger interrogation  
scanning systems, they are in the minority when  
it comes to  
control. This then leaves  
to operate in between the obsolete and the  
general coverage of  
a supervisory  
very large orbit