15kV Standard R-C Snubber Application Guide.pdf

Schneider Electric Engineering Services

COVER LETTER COVER PAGE

15kV Standard R-C Snubber Application Guide (INTERNAL USE ONLY)

Prepared by Christopher L. Fraley, P.E.

Issued: March 2012

Schneider Electric Engineering Services The following report was prepared by the Power System Engineering group of Schneider Electric Engineering Services, LLC (SEES) utilizing industry-accepted standards and practices along with the proprietary methodologies and analysis tools of SEES. Data used in this analysis was acquired by Power System Engineering and provided by others, through onsite discovery, published information, equipment nameplates, manufacturer ratings, testing, analysis, or other means. SEES assumes no responsibility for inaccuracies in data provided by others. The study is intended for use by qualified individuals to facilitate the installation, operation, maintenance, and safety of the electrical power system depicted. Modification of equipment, changes to system configuration, adjustment of protective device settings, or failure to properly maintain equipment may invalidate these results. The stylized trademarks “Square D” and “Schneider Electric” and any other trademarks and trade names that are the property of Schneider Electric USA, Inc are used by permission.

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TABLE OF CONTENTS

1

SUMMARY .....................................................................................................4

1.1

Introduction ...................................................................................................................................... 4

1.2

Results and Recommendations........................................................................................................ 4

1.3

Disclaimer.......................................................................................................................................... 5

2

SNUBBER COMPONENT SELECTION METHODOLOGY ...........................6

2.1

Background ....................................................................................................................................... 6

2.2

Selection of Resistor and Capacitor ................................................................................................ 9

2.3

Fuse Selection.................................................................................................................................. 10

2.4

Power System Constraints ............................................................................................................. 12

2.5

Fuse Monitoring.............................................................................................................................. 12

APPENDIX A:

CATALOG CUTS FOR RECOMMENDED COMPONENTS ....13

APPENDIX B: SNUBBER COMPONENT CALCULATIONS AND TIMECURRENT CURVE FOR FUSE APPLICATION.................................................14 APPENDIX C: POWER SYSTEM REQUIRMENTS CHART FOR APPLYING STANDARD 15KV SNUBBER COMPONENTS.................................................15

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1

SUMMARY

1.1

Introduction

This report documents the results of a 15kV R-C snubber component standardization project. The scope of this analysis is limited to selection of components for 15kV snubbers to reduce the probability of damage due to transformer-vacuum switching device interaction. When a transformer is switched into or out of a system, the transient voltage produced at the terminals of the transformer may contain several high frequency oscillatory components. When this oscillatory transformer terminal voltage has a frequency near one of the natural frequencies of the transformer and is of sufficient magnitude and duration, permanent damage to the transformer internal insulation structure may result. The R-C snubber is a mitigation method to reduce the peak internal voltage response of a transformer when its terminals are subjected to an oscillatory transient voltage (reproduced from IEEE Std C57.142-2010 Guide to Describe the Occurrence and Mitigation of Switching Transients Induced by Transformer, Switching Device, and System Interaction).

1.2

Results and Recommendations

15kV R-C snubber component selection was reviewed for power systems with the following configurations: ¾ ¾ ¾ ¾ ¾ ¾ ¾

12.47kV, 13.2kV and 13.8kV 60Hz solidly grounded wye power systems. Source transformer (transformer which feeds transformers with snubbers installed) size is 3750kVA or larger. Transformer in which snubber is applied is fed only by a utility source (no generator feeds). A maximum quantity of five transformers with snubbers are installed on the power system. Power cables feeding the transformer in which the snubber is applied are sized between #1/0 and 500kcmil with a single conductor per phase (no parallel conductors). A transformer with a close-coupled vacuum switching device is permitted. Cable length from the vacuum interrupting device to the transformer does not to exceed 500-feet to an individual transformer or a total of 2500-feet where multiple transformers are applied in a loop feed configuration. Medium-voltage power factor correction capacitors are not applied on the power system.

If each of the above power system configuration conditions are met the following standardized components are recommended for 15kV snubber application. If any of the power system configuration conditions are not met further analysis is required and the standardized components should not be applied until confirmed applicable. ¾

Resistors: Kanthal Globar 891SP250K ceramic non-inductive resistor, 16kV peak, 25Ω, 750W (with Kanthal Globar 36200 aluminum connector caps).

¾

Capacitors: ABB 2GUS031801A3 single-phase surge capacitor, 13.8 kV, 0.25 μF.

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Fuses: Hi-Tech HTFX240006, 15.5kV, 6A, 50kA interrupting. Fuse interrupting rating should be compared to power system available short-circuit current at the location of snubber application to verify adequacy.

¾

The use of properly-sized surge arresters, in addition to the snubber, is recommended. The surge arresters must be applied at the transformer primary terminals downstream of the vacuum switching device.

It is recommended that fuse monitoring be installed to provide indication that the snubber fuses are intact. One approach to monitoring with the recommended components is to mount the capacitor on insulating supports and measure the current in the grounded conductor from each capacitor using current transformers and relays. Sensitive relays detect loss of current if a fuse is blown.

1.3

Disclaimer

Although experience has shown snubber circuits to be effective at eliminating transformer damage due to transformer-vacuum switching device interaction, it must be understood that accurate modeling of this phenomenon is not practical due to the number of variables involved with modeling the behavior of vacuum switching device reignition behavior. Therefore, no absolute guarantee can be made that all transformer interwinding resonance concerns will be completely eliminated by application of the snubber with the components selected. However, the probability of such interactions is substantially reduced by use of the snubber. The use of properly-sized surge arresters, in addition to the snubber, is recommended. The surge arresters must be applied at the transformer primary terminals downstream of the vacuum switching device.

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2 2.1

SNUBBER COMPONENT SELECTION METHODOLOGY Background

An R-C snubber circuit consists of a resistor and capacitor in series, along with a fuse. This resistor-capacitor-fuse combination is connected line-to-ground in each phase of a 3-phase power system in order to dissipate energy associated with transient voltages, and to limit the frequencies associated with such transients. The circuit concept for an R-C snubber is shown in Figure 1 below. In this application the snubber is being used to protect a transformer from the effects of vacuum circuit breaker-transformer interaction. This interaction is described in IEEE Std C57.142-2010 Guide to Describe the Occurrence and Mitigation of Switching Transients Induced by Transformer, Switching Device, and System Interaction. Although this guide does not give an exact methodology for sizing such a snubber for every situation, it does represent the most complete technical description to date regarding the phenomena of interest in snubber design for the protection of transformers due to vacuum circuit breaker-transformer interaction.

Figure 1: R-C Snubber Circuit Concept (reproduced from IEEE Std C57.142-2010) Transformer winding capacitances, both turn-to-turn and turn-to-ground, play a significant role in the performance of the winding when it is subjected to high-frequency disturbances. The result is that, when subjected to such disturbances, voltages may be developed inside the winding that exceed the terminal voltages. Such behavior occurs when the frequency content of the disturbance contains frequencies at or near a natural frequency of the winding. The natural frequencies of a given winding are a function of the winding design, with the lowest typically being on the order of several kHz. Figure 2 below shows a representative example of the transformer voltage at the center of a transformer winding vs. frequency.

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Figure 2: Example of voltage at the center of a transformer HV winding vs. frequency (reproduced from IEEE Std C57.142-2010) Means of exciting a transformer winding at or near one of its natural frequencies is provided by a vacuum circuit breaker as it interrupts current. Multiple re-ignitions can occur as the vacuum contacts move apart during the opening cycle of the circuit breaker, and if any of the resulting disturbance frequencies set up by the re-ignitions is close to a natural frequency of the transformer, high internal winding voltages may result as described above. Similarly, the traveling voltage wave as a transformer is energized can excite a transformer close to one of its natural frequencies. Figure 3 below shows a representative transformer terminal voltage during a vacuum circuit breaker re-ignition sequence:

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Figure 3: Representative transformer terminal voltage during re-ignition sequence. Because of the variables involved in the performance of the circuit breaker, modeling of the transient performance of the system during circuit breaker switching for the purpose of predicting whether the transformer will be excited close to one of its natural frequencies is generally considered impractical. The IEEE C57.142-2010 standard does describe “system configurations of concern” and “loads of concern” where the probability of this phenomenon is increased. In general, these consist of frequently-switched transformers which are switched via a switching device directly connected to one or two transformers which are unloaded, very lightly loaded, or feeding nonlinear loads. Because transformer internal winding voltages can be higher than the terminal voltages when this phenomenon occurs, surge arresters applied at the transformer terminals are not an effective means of mitigating this phenomenon, although properly-sized surge arresters are recommended for protection from other types of transients to which the transformer might be exposed. An R-C snubber circuit performs two essential functions in the mitigation of the phenomenon described above: 1.) Dissipation of energy (damping) associated with the transient via the resistor element. 2.) Lowering of the frequency of voltage at the transformer terminals associated with the transient via the capacitor element.

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Selection of Resistor and Capacitor

The IEEE C57.142-2010 standard does not give concrete guidance on the selection of the resistor element; it states only that it “…should be on the order of 5 to 50 ohms.” It must be recognized that at power frequency voltage very little of the voltage drop across the snubber will be across the resistor due to the fact that the capacitor presents relatively high impedance in comparison. However, for the high-frequency transients of interest the opposite is true; the capacitor presents a very small impedance in comparison with the resistor, therefore the voltage drop is almost entirely across the resistor. In order to allow for dissipation of maximum transient energy, the resistor is sized to be approximately equal to the supply cable surge impedance. The surge impedance of the supply cable is independent of the circuit length and may be approximated as: Zs ≈

138 e

1/ 2

⎛D⎞ log⎜ ⎟ (Ω) ⎝d⎠

(1)

where Zs is the magnitude of the cable surge impedance D is the inside diameter of the outer ground sheath d is the diameter of the primary conductor e is the dielectric constant for the cable insulation: approximately 3.0 for EPR and 2.3 for XLP Cable data from various manufacturers, types and sizes were reviewed to determine the range of cable surge impedance for 15kV shielded cables. A cable surge impedance spreadsheet is included in the appendix showing the results of this investigation. As shown in the spreadsheet, for cables ranging from #1/0 through 500kcmil the surge impedance ranges from 16Ω to 29Ω. In practice the actual value of the resistor may be far from the ideal for maximum damping and the snubber will still yield the intended benefits. As such, a 25Ω resistor was chosen so that it could be applied across a wide range of cable sizes. Besides the resistance, the main resistor ratings of concern are the power and energy handling capabilities and the voltage rating. The snubber fuse is selected to protect the resistor according to its energy handling capabilities. Fuse selection is discussed in a separate section. Regarding voltage, resistors considered for this snubber application are assigned a “peak” voltage rating, which is an instantaneous voltage that may be applied across the resistor during normal or transient conditions. Under normal conditions, there is a small 60 Hz voltage drop across the resistor. If a capacitor were to fail in a short circuit mode, the 60 Hz voltage across the resistor would approach system line to neutral voltage. During transient conditions where high frequency voltages may be present, the snubber capacitor impedance may be much less than at 60 Hz and the instantaneous voltage across the resistor may be much higher. For conservatism, the resistor “peak” or instantaneous voltage rating should be higher than the peak of the 60 Hz line to neutral voltage (i.e., 10.8 kV for a 13.2 kV system). The recommended resistor has a peak voltage rating of 16kV, which is suitable for application on the power systems noted. The purpose of the capacitor is to lower the rate of rise time, and thus the frequency content, of transient voltages at the transformer terminals, and to allow for the damping action of the resistor to come into play a high frequencies while allowing the resistor to dissipate very little power at 60 Hz. As with the resistor, the IEEE Std C57.142-2010 does not give concrete guidance on the selection of the capacitor, only that the RC time constant could be “…approximately 1-10μs.” The 25Ω resistor thus requires a capacitor size in the range of 0.04 to 0.4μF. For this reason a

Issued: March 2012

Schneider Electric Engineering Services surge capacitor is normally used for this application; readily-available surge capacitors rated 13.8kV are available with a capacitance of 0.25μF, yielding a time constant of 6.25μs. The 60Hz impedance of a 0.25 μF capacitor is 10.6 kΩ. The resistor therefore may be calculated to require a power rating of 17W at 60Hz, assuming a worst-case 10% system overvoltage. Since some harmonic content will typically be present, the resistor will dissipate additional power due to harmonic current flow, and this must be taken into account. A substantially larger power rating is advisable, on the order of ~200W or greater. Under normal conditions, most of the 60 Hz line to neutral voltage is across the capacitor because its impedance at 60 Hz is much higher than that of the resistor. The capacitor voltage rating should be selected conservatively to allow for overvoltage. In this case, the system line-to-ground voltage has a nominal value of 7.967kV for the highest system voltage of 13.8kV for the standard snubber. A 10% 60 Hz overvoltage should also be taken into account, yielding a maximum voltage of 8.764kV under normal conditions. A capacitor voltage rating of 13.8kV meets the requirement for design overvoltage for a solidly grounded system. Catalog information for the snubber components is included in Appendix A. The calculations per above are included in Appendix B.

2.3

Fuse Selection

Fuses are a very important part of the snubber circuit. They provide protection for the snubber should the capacitor become shorted. Three criteria are used to select the fuses: 1.) The fuses should allow normal 60 Hz + harmonic currents to flow in the snubber 2.) The fuses should protect the capacitors per their rupture curve 3.) The fuses should protect the resistors per their allowable energy dissipation limits A full-range, current-limiting fuse is recommended. The 13.8kV system 60 Hz nominal current flow in the snubber circuit is calculated to be 0.82 A, assuming a worst-case 10% system overvoltage. To account for harmonics the fuse should be at least twice this size. Because the fuse must be rated for the 13.8kV operating voltage, the fuse continuous current rating selection will be limited. One fuse that meets these criteria is a Hi-Tech type FX fuse, available with a minimum rating of 3A with a rating of 15.5kV. A rating of 6A provides additional safety margin for harmonic current flow. Fuses for three phase application should generally be rated for system line-to-line voltage. Manufacturers do make allowances for using fuses rated for line to neutral voltage (or dual-rated fuses) on distribution systems for single-phase feeder taps or for particular transformer winding connections. However, a more conservative rating based on line to line voltage is recommended for the snubber application. ANSI C37.46-1981 American National Standard Specifications for Power Fuses and Fuse Disconnecting Switches states in section 8 “The rated voltage of a power fuse shall be selected on the basis of maximum line-to-line voltage, regardless of whether the fuse is to be applied on a grounded or ungrounded neutral system.” Also, IEEE C37.48-1997 IEEE Guide for the Application, Operation, and Maintenance of High-Voltage Fuses, Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Accessories states in section 3.7.1 for power class fuses “The fuse should have a maximum voltage rating equal to or exceeding the maximum system line-to-line voltage.” A further consideration is that unlike expulsion fuses, current-limiting fuses develop a voltage during interruption that exceeds system line-to-line voltage. Rated voltage of current-limiting fuses should therefore not greatly exceed

Issued: March 2012

Schneider Electric Engineering Services the system line-to-line voltage or the developed voltage may exceed the withstand capability of the system insulation. The capacitor rupture curve for the above recommended capacitor is readily available (and reproduced in Appendix A), however some calculations are required in order to establish the energy time/current withstand curve of the resistor. It should be noted that the “peak energy” value published by the manufacturer for the resistor is based upon a time frame of less than 10ms, and is not applicable for the purpose of establishing a time-current withstand curve for time periods above 10ms. Instead, the maximum allowable “rapid-rise temperature limit” and “longterm rise temperature limit” for the resistor must be established. Once this is done, for a given temperature limit the allowable energy dissipation may be calculated as: J = 4.184 × M × C × T (J)

(2)

where J is the allowable energy dissipation in Joules for rapid-rise or long-term time frame, depending upon the temperature limit value T used M is the mass of the resistor in grams C is the specific heat capacity for the resistor material, in cal/g-°C T is the rapid-rise or long-term rise temperature limit for the resistor Per the manufacturer, mass of the resistor is 1000g, the heat capacity of the resistor material is 0.25 cal/g-°C, the recommended rapid-rise temperature limit is 80°C, and the recommended longterm rise temperature limit is 350°C. Once the value for the allowable energy dissipation is calculated, it can be converted to a current value as follows: I2 t =

J R

(3)

I=

I2 t t

(4)

where I2t is the normalized energy limit in A2s R is the resistance value of the resistor t is the time basis for the calculation Using the above formulae, the withstand current for the resistor was calculated to be 12A at 100s, 58A at 1s, 183A at 0.1s, and 579A at 0.01s. The calculations for this are shown in Appendix B. Strictly speaking, complete protection per the criteria 2.) and 3.) above requires that the fuse timecurrent characteristic fall below and to the left of the capacitor case rupture and resistor withstand curves when plotted together on the same time-current curve (TCC) graph. A 6A, 15.5kV, 50 kA fuse, Hi-Tech catalog number HTFX240006, is selected for this application; catalog data for this fuse is shown in Appendix A. A TCC of the fuse, capacitor canister rupture, and resistor withstand curves is shown in Appendix B. This TCC shows that the specified capacitor is protected per its case rupture curve, and for higher levels of current the resistor is protected per its

Issued: March 2012

Schneider Electric Engineering Services calculated withstand curve. It should be noted that overload protection of the resistor is not possible with the fuse, and this is demonstrated by the resistor withstand curve crossing the fuse curve at a low current level; this is the reason that the resistor was conservatively chosen for steady-state power dissipation requirements. The value of this TCC is to illustrate the protection by the fuses for both the capacitor and resistor should the capacitor become shorted, which is the typical failure mode for a capacitor. The selected fuse has an interrupting rating of 50kA. This interrupting rating should be adequate on most 15kV systems however the fuse interrupting rating should be compared to the available short-circuit current at the location of snubber application to verify adequacy.

2.4

Power System Constraints

In applying the standardized snubber components additional capacitance is added to the power system creating a potential for parallel resonance between the snubber capacitance and source transformer. Resonant harmonics were reviewed for various quantities of snubbers, source transformer size and cable capacitance (see appendix B). The goal was to keep all resonant harmonic values above the 30th harmonic while providing margin for additional unknown system cable capacitances. Based on the results of these calculations the following constraints for application of the standard snubber components where developed: ¾ ¾

¾ ¾

¾

2.5

Source transformer (transformer which feeds transformers with snubbers installed) size is 3750kVA or larger. This requirement limits the source inductance to a maximum value therefore raising the resonant harmonic values. Transformer in which snubber is applied is fed only by a utility source (no generator feeds). A “weak” generator source can have an inductance high enough to as to be resonant with the snubber capacitor at a dominant system harmonic frequency (i.e., 5th and 7th harmonics). A maximum quantity of five transformers with snubbers are installed on the power system. This requirement limits the amount of capacitance added to the power system by the snubbers. Cable length from the vacuum interrupting device to the transformer does not to exceed 500-feet to an individual transformer or a total of 2500-feet where multiple transformers are applied in a loop configuration. This limits the amount of capacitance added to the power system by the power cables. Medium-voltage power factor correction capacitors are not applied on the power system. This requirement prevents the snubbers from shifting the resonant frequency of a power factor correction bank of capacitors to a dominant system harmonic frequency.

Fuse Monitoring

Fuse monitoring is essential since the snubber cannot provide protection on a given phase if the fuse on that phase has opened. One method of monitoring consists of mounting the capacitors on insulating supports and installing current transformers in each of the three grounded conductors from the capacitors. Sensitive relays detect loss of current if a fuse is blown. Local indicating lamps as well as alarm contacts indicate the status of each snubber pole. The monitoring circuit is compatible with various system voltages and control voltages.

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APPENDIX A:

Issued: March 2012

CATALOG CUTS FOR RECOMMENDED COMPONENTS

Series 800 and 1000 Tubular Resistors Product Information

Tubular Resistors – Series 800 and 1000 Series 800 and 1000 Tubular Non-Inductive Bulk Ceramic Resistors provide excellent performance for high peak power or high-energy pulses. Bulk construction advantageously produces an inherently non-inductive resistor; and it allows energy and power to be uniformly distributed through the

Type SP resistors are composed of materials that withstand high operating temperatures resulting in high power dissipation. Maximum continuous operating temperature is specified at 350°C. This type is suitable for use in oil without an oil-resistant coating.

entire ceramic resistor body – there is no film or wire to fail. We offer a full line of rugged, reliable ceramic resistors. We offer three distinctly different ceramic materials to afford the designer with unique components to meet the most demanding requirements:

Type AS resistors are best suited for high energy and voltage pulse applications. Maximum continuous operating temperature is specified at 230°C. The standard dielectric coating is recommended for use in air, and the oil-resistant coating is recommended for use in oil.

Type A is a high-power non-inductive resistor used when high resistance is required.

Globar bulk ceramic resistors are problem solvers for: Type SP

Type AS

Type A

• Motor drive circuits • Snubber circuits • High-frequency circuits • RF dummy loads • Dynamic braking • Transformer protection • Harmonic filter

• Impulse generators • High-voltage circuits • X-ray equipment • High voltage power supplies • Laser/Imaging equipment • Capacitor charge/discharge

• Bleeder • Capacitor charge/discharge … just to name a few uses.

Ordering Information Part Numbering System

Example Part Number: 890AS101KDS

890AS 101 K DS

Terminal End Options SP

No Suffix = Standard aluminum metalized ends No-arc terminal not available on SP products

Construction Type Resistance Value (Ω) For ≥ 10 Ω: First 2 digits are significant figures, third digit is number of zeros to follow, e.g. 101 = 100 Ω

Resistance Tolerance

G = Radial tab, riveted and soldered G1 = Radial tab, riveted and no solder AS

J = + 5% K = + 10% L = + 20%

N = No-arc terminal and dielectric coating NO = No-arc terminal with oil resistant coating DG = Radial tab, riveted and soldered with dielectric coating DG1 = Radial tab, riveted and no solder with dielectric coating GO = Radial tab, riveted and soldered with oil resistant coating

For < 10 Ω: An R replaces the decimal point, e.g. R50 = 0.50 Ω, 7R5 = 7.5 Ω

Contact Information

Kanthal Globar, 495 Commerce Drive, Ste. 7 Amherst, NY 14228-2311, USA 

Phone: (716) 691-4010 Fax: (716) 691-7850 Toll-Free: 877-GLOBAR-2 (877-456-2271) E-mail: [email protected] Website: www.globar.com

DS = Standard dielectric coating and silver metalized ends

TO = Soldered end and oil resistant coating A

No Suffix = Standard nickel metalized ends D = Dielectric coating DG = Radial tab, riveted and soldered with dielectric coating N = No-arc terminal and dielectric coating NO = No-arc terminal with oil resistant coating DG = Radial tab, riveted and soldered with dielectric coating DG1 = Radial tab, riveted and no solder with dielectric coating GO = Radial tab with oil resistant coating TO = Soldered end and oil resistant coating

High Voltage Resistors – High Power Resistors – High Energy Resistors Series 800 and 1000 Tubular Resistors are available in a wide variety of sizes and terminations from 2˝ to 24˝ in length and ½˝ to 2˝ in diameter. These resistors can handle up to 1000 watts, 165 kJ and 165 kV in resistance values from 1 ohm to 1 megohm.

Electrical Specifications Length and Diameter

Type

Average Power @ 40°C (watts)

Resistance Available (ohms) Min. to Max.

Peak* Voltage** (volts)

Peak* Energy (joules)

2˝ x 1/2˝

884SP

1.0

200

22.5

250

1,000

2 1/2˝ x 3/4˝

885SP

1.0

130

45

250

1,000

885AS

6.0

1200

15

2,800

8,000 3,750

885A 5˝ x 3/4˝

6˝ x 1˝

1500

220K

15

750

886SP

1.0

330

90

500

4,000

886AS

15.0

3300

30

7,000

20,000

886A

10,000

3900

390K

30

1,500

887SP

1.0

330

150

1,600

4,000

887AS

12.0

3300

50

13,000

30,000

887A

3900

390K

50

6,000

12,000

5.0

1200

70

30,000

30,000

6˝ x 1 1/2˝

1026AS

8˝ x 1”

888SP

1.0

390

190

2,100

6,000

888AS

15.0

3900

75

16,500

45,000

888A

4700

470K

60

7,500

15,000

6.5

1875

100

46,000

45,000

8˝ x 1 1/2˝

1028AS

12˝ x 1˝

889SP

1.0

680

275

3,200

10,000

889AS

25.0

6800

100

27,000

75,000

889A

8200

680K

90

12,500

25,000

9.0

2500

150

75,000

75,000

12˝ x 1 1/2˝

1032AS

18˝ x 1˝

890SP

1.0

1000

375

4,200

16,000

890AS

40.0

10K

150

43,000

120,000

18˝ x 1 1/2˝

890A

12K

1M

125

20,000

40,000

1038AS

15.0

3800

225

119,000

120,000 16,000

18˝ x 2˝

891SP

1.0

450

750

15,000

24˝ x 2˝

892SP

1.0

600

1000

17,500

22,000

24˝ x 1 1/2˝

1044AS

20.0

4800

300

164,000

165,000

* Allowable peak energy/voltage will depend on the resistance value. Consult factory. ** Derate by 50% with oil resistant coating on Type AS resistors. Energy ratings are based on pulses