Device for detection of short circuits in industrial uses

A method and apparatus for detecting a short circuit across a Vacuum Control Switch by electrically connecting the apparatus to that side of the Vacuum Control Switch which should be dead at anytime the Vacuum Control Switch has manually been placed in the off configuration, and utilizing the arcing and shorting voltage felt there in the event of a malfunction to produce a signal to actuate visual and audio alarm circuits. More particularly, the invention is intended for use with Vacuum Control Switches placed in very high voltage circuits such as industrial furnaces. Its primary purpose is to prevent personal injury by warning maintenance personnel of a malfunction which could produce lethal voltage on components that would be expected to be without electrical voltage whenever the Vacuum Control Switch is in the off position. The apparatus is not independently powered for detection, but utilizes that voltage which is felt on the off side of the open Vacuum Control Switch by virtue of the malfunction. The alarm circuits are physically separated from the industrial use and locked so that the alarm will continue to warn until a knowledgeable party physically shuts the warning system off.

BACKGROUND OF THE INVENTION 
This invention is best suited for the detecting of short circuits occurring 
across the Vacuum Switch. 
In industrial situations, vacuum switches are used to bring high voltage 
electrical power from main supply lines to their industrial use. The 
switches can be placed in their open position in order to work on 
equipment and prevent electrical power to reach the industrial use being 
worked on. However, if a short circuit should occur across the vacuum 
switch when the industrial use is being worked on, dangerous and lethal 
voltage may surge across the switch towards the industrial use. Without an 
adequate warning system, a repariman may suffer serious injuries. 
This invention provides an audio-visual detection of short circuits across 
vacuum switches or similar devices, and prevents maintenance personnel 
from inadvertently or unknowingly disengaging the alarm by placing the 
alarm control panel in a remote place. 
Certain prior patents have approached the solution of this problem by 
monitoring the vacuum switch itself to detect malfunction. U.S. Pat. Nos. 
3,594,754 of Roy E. Voshell and 3,403,297 of Donald W. Couch describe 
methods whereby the pressure in the vacuum type circuit interrupter is 
measured. U.S. Pat. No. 1,733,904 by Prince is basically a redesign of the 
vacuum switch itself by incorporating a vacuum gauge or device which would 
impair the operation of the switch should the vacuum be reduced. U.S. Pat. 
No. 3,735,201 by May is an arcing time relay which is designed to be used 
with vacuum circuit breakers, and the primary purpose is detection of the 
loss of vacuum as manifested by an increase of arcing time. The detection 
device of this invention is a highly sensitive relay. These patents detect 
malfunction in the vacuum switch, but do not detect mechanical malfunction 
such as fused points or other malfunctions which can occur between the 
vacuum switch and the industrial use. In addition, the detection devices 
of the vacuum switches are complex and do not utilize the simple principle 
of using the malfunction voltage itself to excite alarm circuits. 
U.S. Pat. No. 3,558,984 by Smith and Gray describes an A. C. System Fault 
Indicator which utilizes coils as sensing devices and is devised to detect 
various faults in phase or current in a conductor such as a distribution 
line. U.S. Pat. No. 3,851,322 by Compoly and Temple detects short circuits 
in static converters by monitoring line voltages in currents. Both these 
patents differ from the present invention in at least one aspect in that 
the present invention monitors an inert circuit. 
The above inventions monitor possible malfunctions but in doing so have to 
use complex monitoring devices. Those detection devices which monitor the 
vacuum switch only, do not prevent a mechanical malfunction which can 
occur between the vacuum switch and the industrial use. The present 
invention uses the voltage of the malfunction itself to excite the warning 
system. 
SUMMARY OF THE INVENTION 
The present invention detects malfunctions in a vacuum switch caused by 
both fusing of points or arcing due to pressure loss and also detects 
possible mechnical malfunction. The invention does not depend upon the 
proper functioning of indirect sensing devices, but directly utilizes the 
malfunction voltage to excite alarm circuits. Because it monitors a 
normally inert circuit no elaborate discrimination or measurement device 
need be employed. Voltage of any magnitude can be utilized to trigger the 
incorporated alarm devices. The controls of disengaging the alarm 
circuitry are physically separated and locked so that inexperienced 
personnel will be unable to inadvertently or unknowingly disengage the 
protective device. 
A Vacuum Control Switch controls the high voltage electrical supply to the 
electrical equipment used. When the vacuum switch is manually placed in 
the open position thereby preventing the flow of electrical energy, 
certain contacts are closed connecting the line running from the off side 
of the vacuum switch to a metering circuit which actuates the warning 
circuit in the event of a malfunction. 
If a short circuit or arcing is felt across the Vacuum Control Switch, when 
it has manually been placed in the off position, voltage will be directed 
to a voltage detector relay which determines whether the voltage has 
reached a pre-selected minimum. If it has, the voltage detector relay 
causes switches to close, allowing common voltage to activate the alarm 
circuits.

DETAILED DESCRIPTION 
In an industrial plant 20 an alarm system 34 uses actual malfuntion voltage 
passing past the vacuum switch 24 towards the industrial use 30 to excite 
an alarm system 34. 
A common point 28 is positioned between the transformer 26 and the 
industrial use 30. Therefore, when the industrial use 20 is shut down and 
no current is to flow between the transformer 26 and the industrial use 
30, if a malfunction does occur, current will flow through the common 
point 28 towards the alarm system 34. 
In FIG. 1 the physical separation of the alarm system 34 from the 
industrial use 30 is shown schematically. 
FIG. 1 is a schematic diagram showing the physical separation of the alarm 
system 34 from the industrial use 30. In an industrial plant 20 a power 
source 22 delivers electrical energy to the industrial use 30 through a 
common point 28. Physically separated is a control panel 32 and an alarm 
system 34 placed in a maintenance only area 36, thereby preventing 
unauthorized personnel from turning off the alarm system 34. 
The schematic of FIG. 2 sets forth the location of the common point 28 
between the vacuum switch 24 and the industrial use 30, thereby allowing 
any surge of electrical energy past the vacuum switch 24 towards the 
industrial use 30 to be felt at the common point 28 and thus relayed to 
the alarm system 34. The common point 28 may be placed on any one of the 
three electrical power lines 36, or three common points may be placed on 
each of the three power lines 36. In each of the above listed 
configurations involving the common point 28, sufficient voltage will be 
felt across the alarm system 34 to activate the alarm in case of 
malfunction. 
FIGS. 3 and 4 show in more detail the circuitry that activates the warning 
system in the event of a malfunction. 
In relating the alarm system 34 and the control 32 of FIGS. 1 and 2 within 
the circuitry of FIGS. 3 and 4, the following elements constitute the 
alarm system; voltage detector relay meter 44, switch 50, switch 51, meter 
reset timer relay 66, switch 67, relay 62, switches 64 and 65, bell 54, 
and light 56. 
The following elements constitute the control: silence switch 60, switches 
58 and 59, and switches 38 and 48. 
When the industrial use 30 is either shut down or being worked upon, the 
vacuum switch 24 is placed in an off position thereby preventing the 
passage of electrical energy. When the vacuum switch 24 is in the off 
position, the switch 42, FIG. 3, between the common point 28 and the alarm 
system 34 is manually placed in the connecting position 40, thereby 
allowing electrical energy to flow to the alarm system 34 if current is 
experienced at the common point 28. Thus, when a malfunction occurs, 
either across the vacuum switch 24 or due to a mechanical malfunction, 
current experienced at the common point 28, will be experienced at the 
voltage detector relay meter 44. 
In the preferred embodiment a Simpson voltage detection meter is utilized. 
The Simpson Co. is located at 853 Dundee Ave., Elgin, Illinois. The 
specific Simpson voltage detection meter relay utilized is found under 
Simpson publication specification 55-100001 revision number 9 published 
June of 1975. 
When the industrial use 22 is being used, the switch 42 is placed in the 
closed position 38, thereby preventing current to flow through to the 
voltage detector relay meter 44. 
When the industrial equipment 30 is in use, the switches 48 are in an open 
position preventing common voltage 52 from being applied to the control 
panel 32 and alarm system 34 circuits. When the industrial use 30 is not 
being used and the vacuum switch 24 is open, the switches 48 are closed 
allowing common voltage 52 to be potentially applied to the control panel 
32 and alarm system 34 circuits. The common voltage 52 is prevented from 
reaching the alarm circuit 46 when there is not a malfunction, for switch 
50 is in an open position and switch 51 is in a closed position. 
If and when a malfunction occurs when the vacuum switch 34 is off, current 
is felt at the common point 28. Since the switch 42 is placed in the 
closed position 40, current continues to the voltage detector relay meter 
44. Switch 42 is operated manually. Since switch 51 is in a closed 
position, the malfunction current flows through the voltage detector relay 
meter 44. The voltage detector relay meter 44 is set at a pre-selected 
minimum so that if a voltage is detected greater than the minimum set on 
the voltage detector meter 44, switch 50 is closed and switch 51 is 
opened. 
In FIG. 3 the switch 51 is in a closed position and switch 50 is in an open 
position. Thus, FIG. 3 illustrates the condition where the vacuum switch 
24 is in an open position and there should be no current felt at the 
common point 28. In this circumstance, the common voltage 52 is connected 
to the alarm system 34 and control system 32 by the switches 48. It should 
also be pointed out that in FIG. 3, no malfunction current has been 
experienced at the voltage detector meter relay 44 to cause the closing of 
switch 50. 
Upon experiencing malfunction current of sufficient magnitude, voltage 
detector meter relay 44 closes switch 50 thereby allowing common voltage 
52 to activate the alarm circuits 46. The voltage experienced at common 
point 28 during the malfunction necessary to activate the alarm circuit 46 
is variable and is easily modified by determining a set point on the 
voltage detector relay meter 44. 
In FIG. 4 the voltage detector meter relay 44, malfunction current greater 
than a pre-selected minimum has been experienced by the voltage detector 
meter relay 44. Having experienced the malfunction current, the voltage 
detector meter relay has caused switch 51 to open and switch 50 to close. 
Thus, common voltage 52 is experienced by the alarm circuit 46. 
The alarm circuit 46 may be composed of both audio and visual warning 
elements, represented in the circuit of FIG. 4 as a bell 54 and light 56. 
In addition to the basic alarm circuitry described above, there is a test 
alarm feature of the circuit as shown in FIG. 4. The testing of the alarm 
circuit is accomplished when the vacuum switch 24 is in the closed 
position allowing voltage to be applied to the industrial use 30, thus the 
switch 42 is in the open position 38. To test, the switch 58 is closed and 
switch 59 is opened allowing common voltage 52 to reach the voltage 
detector meter relay 44. The current from the power supply 52 reaching 
voltge detector meter relay 44 is necessarily sufficient to close switch 
50 thereby allowing common voltage 52 to the alarm circuit 46. 
The circuit of FIG. 4 also allows for the alarm system to be silenced. When 
the warning is on, current flows to the bell 54 and light 56. To silence 
the alarm, silence switch 60 is closed, thereby energizing control relay 
62 which opens switch 64 and closes switch 65 thereby locking up the relay 
62. The opening of switch 64 interrupts current to the light 56 and bell 
54, thus silencing the alarms after the hazards have been detected and 
maintenance is in progress. 
After the malfunction has been corrected, switches 48 are opened thereby 
cutting off the common voltage 52 from the alarm 46. Once common voltage 
52 is no longer experienced across meter reset timer relay 66, after a 
given period of time meter reset timer relay 66 closes switch 67 which in 
turn closes switch 51 and opens switch 50. 
In the preferred embodiment, the meter reset timer relay 66 is a part of 
the Simpson voltage detection meter relay described previously. The 
specific Simpson voltage detection meter relay utilized is found under 
Simpson publication specification 55-100001 revision number 9 published 
June of 1975. 
Thus, the closing of switch 51 and opening of switch 50 is done internally 
within the voltage detection meter relay 44. The advantage of the meter 
reset timer relay 66 is that the voltage detection meter 44 is always in a 
condition for detection of current and there is no reliance on manually 
setting the voltage detection meter relay 44 for detection. 
The illustrated embodiment can be varied within the scope of the invention. 
Thus, it is possible, for example to vary the warning devices and vary the 
circuit which actuates the warning devices. The important feature of the 
invention is that the warning devices are not actuated directly by the 
voltage produced from the malfunction itself. 
Although, a particular preferred embodiment of the invention has been 
disclosed above for illustrative purposes, it will be understood that 
variations of modifications thereof which lie within the scope of the 
appended claims are contemplated.