Surge Arresters
Electrical Apparatus
VariGAP®
Type AZR Heavy Duty
Distribution Class Riser Pole Gapped MOV Arrester
235-50
GENERAL
The Cooper Power Systems VariGAP®
Type AZR heavy duty distribution
class riser pole gapped MOV arrester
(Figure 1) in ratings of 3 through 36 kV,
incorporates the latest in metal oxide
varistor (MOV) and resistance graded gap technology. With this unique
combination of technologies, Cooper
Power Systems has advanced the
performance characteristics of distribution class arresters beyond previously attainable limits.
CONSTRUCTION
The VariGAP Type AZR arrester is a
combination of both metal oxide and
gapped arrester technologies.
Construction consists of metal oxide
varistors in series with a nonlinear
resistance graded gap structure. The
mating of these two service-proven
technologies results in a sharing of
voltage during steady state conditions, minimizing voltage stress on
both components.The VariGAP Type
AZR arrester is also designed with a
60 Hz sparkover in excess of 1.5 times
duty cycle rating. These two features
ensure a temporary overvoltage
(TOV) capability 50% higher than that
available with gapless metal oxide
arresters.
The VariGAP Type AZR design is
available with or without an isolator
and can be supplied with or without a
NEMA cross arm mounting bracket.
Figure 1.
VariGAP Type AZR Heavy Duty Distribution Class Riser Pole Gapped MOV
Arrester.
OPERATION
PRODUCTION TESTS
The operation of the VariGAP Type
AZR arrester differs from conventional gapless metal oxide arresters.
When current surges occur, the gaps
spark over, leaving only the metal
oxide varistors in the circuit. This
results in lower sparkover and discharge voltages than are possible
with silicon carbide arresters, and
lower discharge voltages than are
possible with gapless metal oxide
arresters.
The superior protective characteristics of the VariGAP Type AZR arresters
provide excellent protection against
repeated high energy switching
surge discharges. They are ideal for
applications such as underground
system protection, multiple lines and
cable circuits.
A complete production test program
ensures a quality product. Each
VariGAP metal oxide varistor receives
a series of electrical tests. Quality is
further assured by a series of
destructive tests performed on every
batch of varistors. Listed are the tests
that are performed on the varistors:
■ 100% Physical Inspection
■ 100% Discharge Voltage Test
■ 100% V1mA/cm2
■ 100% Leakage Current at 80% of
V1mA/cm2 Voltage
■ Batch High-current, Short duration Test
■ Batch Thermal Stability Test
■ Batch Disk Aging Test
August 1994 • Supercedes 1/92 • © 1994 Cooper Power Systems, Inc.
Printed in U.S.A.
Each VariGAP Type AZR arrester
must pass the following production
tests:
■ 100% Physical Inspection
■ 100% Vacuum over Fluid Seal Test
■ 100% Leakage Current Test
■ 100% RIV Test
■ 100% Sparkover Level Test
STANDARDS
The VariGAP Type AZR arrester complies with the latest revision of
ANSI/IEEE C62.11 “IEEE Standard for
Metal Oxide Surge Arresters of AC
Power Circuits”.
1
Features and Detailed Description
INSULATING TERMINAL CAP
Polymer cap provides superior
wildlife protection.
GENERAL APPLICATION
RECOMMENDATIONS
,,,
MOV DISKS
Highly nonlinear metal
oxide varistors provide
exceptional surge protection.
,,,
HIGH STRENGTH
WET PROCESS
GLAZED PORCELAIN
Withstands thermal
and mechanical
shocks; excellent
washing characteristics; provides high
creepage distance
above and below the
hanger bracket.
RESISTANCE
GRADED GAPS
Provide consistent
sparkover characteristics
even for rapidly rising
surge waves.
ALUMINUM SPACER
Provides additional
length for extended
creepage porcelain.
HEAVY STEEL COIL
SPRING
Maintains high pressure
on disks for effective
contact surfaces; protects from mechanical
shock.
COPPER STRAP
Provides a low resistance shunt for surge
current discharge.
SOLDERLESS
CONNECTOR
Accommodates
No. 10 solid
through No. 2/0
stranded line and
ground leads.
Figure 2.
Cutaway illustration of VariGAP Type AZR Arrester.
2
IDENTIFICATION
INFORMATION
Convenient reference
for arrester type,
MCOV, voltage rating
and year and quarter
of manufacture.
ISOLATOR™ GROUND
LEAD DISCONNECTOR
Provides positive
isolation and visual
identification if arrester
becomes damaged
internally.
The rating of an arrester is the power
frequency line-to-ground voltage at
which the arrester is designed to
pass an operating duty-cycle test.
Table 1 provides a general application guide for the selection of the
proper arrester rating for a given system voltage and system grounding
configuration.
Cooper Power Systems application
engineers are available to make recommendations. The following information is normally required:
1.System maximum operating
voltage.
2.System grounding conditions.
A. For four-wire circuits, grounding
conditions depend upon
whether the system is multigrounded, whether it has a neutral impedance and whether
common primary and secondary
neutrals are used.
B. For three-wire circuits, grounding
conditions depend upon
whether the system is solidly
grounded at the source, grounded through neutral impedance at
the source transformers or
ungrounded.
Where unusual conditions exist
(high ground resistance, high capacitive load, arc-welding equipment,
etc.) the following supplementary
information is necessary:
1.The unusual condition.
2.Type of construction, phase
spacing, length of line, conductor
size.
3.BIL of equipment and line
insulation.
4.Phase-sequence components of
impedences on the load side of the
distribution substation.
The impedance of the transformer
and the impedance and grounding
of supply to the substation all affect
the voltage during faults.
TEMPORARY
OVERVOLTAGE
(TOV) CAPABILITY
TABLE 1
Commonly Applied Voltage Ratings of the VariGAP type AZR Arrester
System Voltage
(kV rms)
Recommended Arrester Rating*
(kV rms)
Four-Wire Wye Three-Wire Wye
Multi-Grounded Solidly Grounded
Neutral
Neutral
Nominal
Maximum
2.4
4.16Y/2.4
4.16
4.8
6.9
8.32Y/4.8
12.0Y/6.93
12.47Y/7.2
13.2Y/7.62
13.8Y/7.97
13.8
20.78Y/12.0
22.86Y/13.2
23
24.94Y/14.4
27.6Y/15.93
34.5Y/19.92
46Y/26.6
2.54
4.4Y/2.54
4.4
5.08
7.26
8.8Y/5.08
12.7Y/7.33
13.2Y/7.62
13.97Y/8.07
14.52Y/8.38
14.52
22Y/12.7
24.2Y/13.87
24.34
26.4Y/15.24
29.3Y/16.89
36.5Y/21.08
48.3Y/28
––
3
––
––
––
6
9
9
10
10
––
15
18
––
18
21
27
36
Delta and
Ungrounded
Wye
––
6
––
––
––
9
12
15
15
15
––
21
24
––
27
30
36
––
PERFORMANCE TEST
CHARACTERISTICS
3
6
6
6
9
––
––
––
––
––
18
––
––
30
––
––
––
––
The VariGAP Type AZR arrester consistently withstands the following
design tests as described by
ANSI/IEEE C62.11:
■ Duty Cycle:
20 current surges of 10 kA crest
8/20 µs waveshape followed by 2
current surges of 40 kA crest
8/20 µs waveshape.
■ High-current, Short-duration
Discharge:
2 current surges of 100 kA crest
4/10 µs waveshape.
■ Low-current, Long-duration
Discharge:
20 current surges of 250 A crest
2000 µs rectangle wave duration.
Following each of these tests, the
arresters remain thermally stable as
verified by:
■ Continually decreasing power values during a thirty minute power
monitoring period.
■ No evidence of physical or electrical deterioration.
■ The 60 Hz sparkover and 10 kA
(8/20 µs) discharge voltages
measured after each test changed
by less than 10% from the initial
values.
* Per IEEE Std. C62.22 [lower rating may be used if fault durations are not to exceed the
temporary overvoltage (TOV) capability of the arrester.]
2.2
2
1.8
The Temporary Overvoltage (TOV)
capability of the VariGAP Type AZR
arrester is shown in Figure 3.
Per Unit MCOV
1.6
Per Unit Arrester Rating
1.4
1.2
1
0.1
1
10
100
1000
10 4
10 5
TIME (Seconds)
Figure 3.
Temporary overvoltage curve. No prior duty – 60° C ambient.
3
235-50
PROTECTIVE
CHARACTERISTICS
The protective characteristics of the
VariGAP Type AZR arresters are
shown in Table 2.
TABLE 2
Protective Characteristics
Arrester
Rating
(kV rms)
MCOV
(kV rms)
3
6
9
10
12
15
18
21
24
27
30
36
2.55
5.10
7.65
8.40
10.20
12.70
15.30
17.00
19.50
22.00
24.40
29.00
Minimum
Front-of-wave
60 Hz
Protective
Sparkover
Level*
(kV crest√2)
(kV crest)
9.0
15.0
16.5
16.5
21.0
25.0
31.0
34.0
39.0
45.0
50.0
60.0
Maximum Discharge Voltage (kV crest)
8/20 µs Current Wave
8/12
15/23
21/24
21/27
29/35
37/39
44/47
51/52
58/63
64/71
71/78
85/91
1.5 kA
3 kA
8.2
15.8
16.4
18.4
24.5
27.0
32.7
36.0
43.4
49.1
54.0
63.0
8.7
16.8
17.4
19.5
26.0
28.7
34.7
38.2
46.0
52.1
57.3
66.9
5 kA
9.2
17.7
18.4
20.7
27.5
30.3
36.7
40.4
48.7
55.1
60.6
70.7
10 kA
20 kA
40 kA
10.0
19.3
20.0
22.5
30.0
33.0
40.0
44.0
53.0
60.0
66.0
77.0
11.3
21.7
22.5
25.3
33.8
37.2
45.0
49.6
59.7
67.6
74.3
86.7
13.6
26.2
27.1
30.5
40.7
44.8
54.2
59.7
71.9
81.4
89.5
104.4
* Number 1/Number 2
Number 1 – This is the value of the sparkover of the gap assembly based on a wave rising 100 kV per 12 kV of arrester rating.
Number 2 – Based on 10 kA current impulse that results in a discharge voltage cresting in 0.5 µs.
INSULATION
CHARACTERISTICS
The insulation characteristics of the
VariGAP Type AZR arresters are
shown in Table 3.
TABLE 3
Insulation Characteristics
Arrester
Rating
(kV rms)
3
6
9
10
12
15
18
21
24
27
30
36
Creepage
(in.)
2.8
6.6
10.4
10.4
13.2
13.2
17.9
17.9
21.7
21.7
26.4
26.4
(cm)
7.1
16.8
26.4
26.4
33.5
33.5
45.5
45.5
55.1
55.1
67.1
67.1
Strike
(in.)
2.0
4.5
7.0
7.0
8.9
8.9
12.0
12.0
14.4
14.4
17.5
17.5
(cm)
5.1
11.4
17.8
17.8
22.6
22.6
30.5
30.5
36.6
36.6
44.5
44.5
Insulation Withstand Voltages
1.2/50 µs
1 min.
10 sec.
Impulse
Dry
Wet
(kV crest)
(kV rms)
(kV rms)
45
60
75
75
95
95
125
125
150
150
200
200
15
21
27
27
35
35
42
42
70
70
95
95
13
20
24
24
30
30
36
36
60
60
80
80
4
235-50
DIMENSIONS AND
CLEARANCES
The dimensions and clearances of
the VariGAP Type AZR arresters are
shown in Figure 4.
A
0.20”
Minimum
Recommended
Clearances*
Dimensions
B
Phase-to-Ground
2.68”
TO
4.00”
Phase-to-Phase
Arrester
Rating
(kV rms)
(in.)
(cm)
(in.)
(cm)
(in.)
(cm)
(in.)
(cm)
3
6
9
10
12
15
18
21
24
27
30
36
9.19
11.67
14.77
14.77
17.25
17.25
20.97
20.97
24.07
24.07
27.79
27.79
23.3
29.6
37.5
37.5
43.8
43.8
53.3
53.3
61.1
61.1
70.6
70.6
5.20
5.20
5.82
5.82
6.44
6.44
7.06
7.06
7.68
7.68
8.30
8.30
13.2
13.2
14.8
14.8
16.4
16.4
17.9
17.9
19.5
19.5
21.1
21.1
3.4
4.4
5.6
5.6
6.4
7.1
9.6
9.6
11.1
11.1
11.1
13.1
8.6
11.2
14.2
14.2
16.3
18.0
24.4
24.4
28.2
28.2
28.2
33.3
5.2
6.5
8.0
8.0
8.7
9.7
12.2
12.2
14.2
14.2
14.2
17.2
13.2
16.5
20.3
20.3
22.1
24.6
31.0
31.0
36.1
36.1
36.1
43.7
4.00”
TO
5.00”
3.06”
DIA.
A
2.56”
1.69”
B
2.34”
3.87”
* All clearances are measured from centerline of arrester per IEEE C62.22.
Figure 4.
Dimensions for AZR501B and AZR502B series.
ORDERING INFORMATION
To order a Cooper Power Systems
VariGAP Type AZR arrester, determine the voltage rating for the
intended application using Table 1.
Specify the appropriate catalog
number from Table 4. Contact the
Cooper Power Systems sales
engineer in your location for
applications not listed.
TABLE 4
Ordering Information
Catalog Numbers:
VariGAP Type AZR Arrester
Arrester
Rating
(kV rms)
3
6
9
10
12
15
18
21
24
27
30
36
With NEMA
Crossarm
Bracket
Without NEMA
Crossarm
Bracket
AZR501B3R
AZR501B6R
AZR501B9R
AZR501B10R
AZR501B12R
AZR501B15R
AZR501B18R
AZR501B21R
AZR501B24R
AZR501B27R
AZR501B30R
AZR501B36R
AZR502B3R
AZR502B6R
AZR502B9R
AZR502B10R
AZR502B12R
AZR502B15R
AZR502B18R
AZR502B21R
AZR502B24R
AZR502B27R
AZR502B30R
AZR502B36R
CAUTION: The values
shown in Figure 4 are the
minimum clearances recommended
by Cooper Power Systems. These
clearances may be revised to meet
local or system requirements for
spacing or energized equipment.
However, safe operating procedures must always be followed.
!
VariGAP® is a registered trademark of Cooper Power Systems, Inc.
Isolator™ is a trademark of Cooper Power Systems, Inc.
5
P.O. Box 1640
Waukesha, WI 53187