IEEE Power & Energy Magazine - July/August 2021 - 93

extinguished, and the required large air
gaps made for a less-than-compact design.
Also, it was found that the length
of time that these arcs were present
caused an unacceptable resonance
rise in voltage that, over time, led to
more faults from damaged insulation.
Figure 5 shows such an arc being drawn
during tests in Kalamazoo, Michigan.
General Electric, on the other
hand, began to develop a breaker that
could extinguish an arc under oil. Engineers
realized from their work on
New York City's Metropolitan Traction
Co. that the installed horsepower
of the generators and way they were
connected to their load would soon require
a level of protection that had not
yet been designed. The result was the
H-form circuit breaker. Several years
later, Westinghouse would abandon
the air break concept and produce its
own oil breaker.
The oil break switch had been in
use for several years. C.E.L. Brown
of Brown Boveri in Europe designed
one of the first oil circuit breakers in
1898. Elihu Thomson patented a handoperated
switch in 1894, and Alexander
Wutz, a Westinghouse engineer,
also patented a switch. These were not
power switches, however.
General Electric was the first of
the larger equipment manufacturers to
work on a power oil switch. By 1900,
it had put a 6,000-V power circuit oil
switch into service at the Metropolitan
Railway (Figure 6); it was designated
as an H form. The first installation of
this switch was on the two-phase system
of the second Adams plant in Niagara
Falls, New York (Figure 7). By
now, Westinghouse realized the limitations
of the air break switch and, in
1905, brought out its type G switch. At
about this time, the term oil switch had
been changed to oil circuit breaker.
Figure 8 shows the oil vessel of
an H-form breaker. According to
E.M. Hewlett, a GE engineer with
several patents dealing with current
interruption in a discussion in a 1919
AIEE Transactions paper by A.R.
Cheyney, the high rupturing capacity
of the switch is due to pressure from
july/august 2021
the gas produced by the arc. It expands
and forces oil under pressure
through the same aperture in which
the arc is drawn as the arc follows
the contact rod. This rush of oil both
cools the arc and injects a high resistance,
resulting in the opening of the
circuit. An arc struck in oil is typically
on the order of inches at most,
compared to one of several feet when
interrupted in air.
The study of the arc itself and its
action and nature under the conditions
found in circuit breakers was to be the
Power System Analysis
EasyPower
As Easy As
R
R
PANEL
PANEL
PANEL
.5 .6
1000
800
600
500
400
300
200
TX-2
1 / 1.288 MVA
13.8 - 0.48 kV
6%
100
80
60
50
40
30
20
BL-1
10
8
4
5
6
2
3
GE MVT-Plus
Sensor = 1600
Plug = 1600
Cur Set = 1.1 (1760A)
LT Band = 1
STPU = 2.5 (4400A)
ST Delay = Int
ST Delay I²t = Out
Override = 50000A
1
.8
.6
.5
.4
.3
.2
BL-3
GE MVT-9
Sensor = 800
Plug = 800
Cur Set = 0.5 (400A)
LT Band = 1
Inst = 4 (3200A)
TX-2
.1
.08
.06
.05
.04
.03
.02
BL-5
Cutler Hammer Series C
HFD
Frame = 225A (150AT)
Trip = 150
1000 / 1288 kVA
INRUSH
BL-3
29249A
.03
BL-5
20574A
.01
.5 .6
.8
1
2
3
4
5 6 7 8 9 10
2
3
4
5 6 7 8 9 100
2
3
4
5 6 7 8 9 1000
CURRENT IN AMPERES X 100 AT 480 VOLTS
2
3
4
.01
5 6 7 8 9 10000
.02
.1
.08
.06
.05
.04
BL-1
18627A
C-6
1 - 400 kcmil CU
.2
10
8
M-1
BL-5
C-H HFD
225/150
2
3
4
5
6
BL-1
TX-2
1000 / 1288 kVA
6%
SWG-4
BL-3
GE AKR-30H
800/400
GE AKR-50
1600/1760
.8
1
2
3
4
5 6 7 8 9 10
CURRENT IN AMPERES X 100 AT 480 VOLTS
2
3
TX-2
FLA
4
5 6 7 8 9 100
2
3
4
5 6 7 8 9 1000
2
3
4
5 6 7 8 9 10000
1000
800
600
500
400
300
200
100
80
60
50
40
30
20
1
.8
.6
.5
.4
.3
Arc Fault
Bus Name
BUS-3
BUS-7
M-1
REFINER
SWG-4
MCC-1
MCC-2
PNL-1
PNL-2
Arc Fault
Bus kV
13.8
13.8
MAIN SWG 3.8
2.4
0.48
Upstream
Trip Device
Name
R-6
R-7
0.48 BL-3
R-18
R-7
R-6
PNL-2
0.48 BL-2
0.48 BL-3
0.208 FS-2
0.208
Upstream
Trip Device
Function
51/50
51/50
51/50
51/50
51/50
Equip Type
Electrode
Configuration
Open Air VOA
Open Air VOA
Other
HCB
Switchgear VCB + HCB
Switchgear VCB + HCB
Switchgear
MCC
0.208
PNL-1
PNL-1
MCC
Panel
Panel
VCB + HCB
VCB
VCB
Panel
VCB + HBB
VCB
VCB
Electrode
Gap
(mm)
152
152
32
152
104
32
25
25
25
25
Est Arc Flash
Boundary
(inches)
32.1
30.5
Working
Distance
(inches)
Incident
Energy
(cal/cm2
+ 26 1.7
+ 26 1.5
31.6 + 18 3.8
189.3 + 18 59.3
261.9
213.2
+
+
53.6
53.1
48.2
57.8
18 122.8
18 135.1
+ 18
+ 18
+
57.8 + 18 7.7
+ 18
6.9
6.8
18 7.1
7.7
)
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ieeepower & energy magazine
93
TIME IN SECONDS
17.58 1.90
18.71
0.15
TIME IN SECONDS
24.13
19.48
4' - 0 "
6.0
0.48
3' - 6 "
1' - 0 "
Arc Flash and Shock Risk Hazard
Appropriate PPE Required
Flash Hazard Boundary
cal/cm2 at 18 inches - Arc Flash Incident Energy
kV Shock Hazard when cover is removed
Limited Approach
Restricted Approach
Equipment Name: SWG-4
(Fed By: 18A)
VALID FOR NORMAL SYSTEM CONFIGURATION ONLY
Arc Flash and Shock Risk Hazard
Appropriate PPE Required
4' - 0 "
6.0
0.48
3' - 6 "
1' - 0 "
Flash Hazard Boundary
cal/cm2 at 18 inches - Arc Flash Incident Energy
Arc-rated shirt and arc rated pants or arc rated coverall
kV Shock Hazard when cover is removed
Limited Approach
Restricted Approach
Equipment Name: MCC-23A
(Fed By: 27B)
VALID FOR NORMAL SYSTEM CONFIGURATION ONLY
http://www.EasyPower.com/demo
IEEE Power & Energy Magazine - July/August 2021

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