ML18100A317

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Isolation Tests Process Instrumentation Isolation Amplifier Westinghouse Hagan Computer Sys Div Model 131-110.
ML18100A317
Person / Time
Site: Salem PSEG icon.png
Issue date: 04/30/1975
From: Bruno J, Eicheldinger C
WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML18100A314 List:
References
WCAP-7509-P-A, NUDOCS 9304210006
Download: ML18100A317 (34)
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Text

9304210006 930126 PDR ADOCK 05000272 P*  ! PDR

WCAP-7509-P-A WESTINGHOUSE CLASS 3 ISOLATION TESTS PROCESS'- INSTRUMEN!f"ATHlW iSOlAHON~ AMPLIFIER WESTINGHOUSE' HAGAfi' COMPtffER SYSTEMS'- Di VISION MODEL 1 31-110 J. Bruno April, 1975 C. Eicheldinger~*Man er Nuclear- Safety- Department Work*Sponsered by, Projects* Department e /97.5' Westinghouse Electric Corp.

WESTINGHOUSE* ELECTRH> Ct>RPORATION Nuclear*** Energy* Systems P. O.*Box 355 Pittsburgh*,~ Pe~nsyi vani a -

  • 15230

UHITED ST/,Tr::S ATOM IC EN El;:G y co:,11.,*1 I SSlON

., WASHINGTON. D.C. 20~*15 JUH G 1973 Mr. Romano Salvatori, Manager Safety and Licensing P\i/R Systems Division Westinghouse Electric Corp.

P. 0. Box 335

- Pittsburgh, Pennsylvania 15230

Dear Mr. Salvatori:

The Regulatory staff has completed its review of Westinghouse Electric Corpora ti on Topical Reports \'JC!\P-7509-L (Proprietary) and \,JCAP-782f~

(Non-Proprietary), both of which are entitled Test Report of Process 11 Instrumentation Isolation Amplifiers 1

'.. The reports describe the test program and summarize the test results used to verify the electrical isolation cc.pabil ities of the \*lestinghouse Hagan Computer Systf:'ms n-i,1ic-ir.n

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design funct"ion of this device is to electr*ically isolc~te the input (protection) circuit when the output (non-protection) circuit is

  • subjected to shorts, opens, or the application of a-c or d-c voltag~s

.(oiT.-r.only present in the control room. The voltages applied to the output terminals during these tests included 48 an&-120 Volts d..:.e (both polarities); 115 Volts d-c (positive polarity); and 117 and 460 Volts a**c.

As a result of our revie\'J, \'le have concluded that \o!CAP-7509-L (Pro-prietary) provides sufficient information to support the conclusion that the testing, as reported, demonstrates the ability of the device to perform its electrica.l isolatfon function \'/here the possibility of f au*1 ts on the output of the device is 1i mited to the range of conditions defined above. To this extent, WCAP-7509-L (Proprietary) will be acceptab 1e as a reference in 0pp 1i cations fo1* construction permits and operating licenses, provided that WCAP-7824, the non-pr.oprietary version, *is referenced in each application v1hich references the_ proprietary _report.

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  • Mr. Romano Salvatori JUN Since the reports do not cover seismic or environffiental testing, the acceptability of this device is also conditioned on appropr"iate seismic and en vi ronr;-:enta 1 quu 1 'ifi ca ti on testing .

Sincerely,

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D. B. Vassallo, Chief Pressurized Water Reactors Branch ~lo. l Directorate of Licensing

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.TABLE OF CONTENTS Section Title Page ABSTRACT v

1.0 INTRODUCTION

SUMMARY

1-1 2.0 EQUIPMENT TESTED 2-1 2.1 Circuit Description 2-1 2.2 Operational Specifications 2-2 3.0 TEST SCOPE 3-1 3.1 Test Procedure 3-1 3.2 Test Results 3-3

4.0 CONCLUSION

S 4-1

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LIST OF ILLUSTRATIONS Figure Title Page 2.1 Signal Isolator Model 131-110 Termina] Connections 2-3 2.2 Signal Isolator Model 131-110 Outline 2-3 2.3 Signal Isolator Functional Block Diagram 2-4 2.4 Signal Isolator Model 131-110 Schematic 2-5 3.1 Normal Mode Voltage Application 3-4 3.2 Common Mode Voltage Application 3-4 3.3 Isolation Test +48 VDC (Normal Mode) 3-9 3.4 Isolation Test -48 VDC (Normal Mode) 3-10

t. 3.5 Isolation Test -t- US VDC (Common ModP) ,,

..J- ..L.L 3.6 Isolation Test 117 VAC (Common Mode) 3-12 f

3.7 Isolation Test 460 VAC (Common Mode) 3-13 3.8 Isolation Test Open & Short Circuit 3-14 3.9 Isolation Test 117 VAC (Normal Mode) 3-15 ~

3.10 Isolation Test +120 VDC (Normal Mode) 3-16 3.11 Isolation Test -120 VDC (Normal Mode) 3-17 3.12 Isolation Test 460 VAC (Normal Mode) 3-18 3.13 Isolation Test 460 VAC (Normal Mode) 3-19 j

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ABSTRACT In Westinghouse Nuclear Steam Supply System (NSSS) control and electrical equipment, isolation amplifiers (isolators) are used where it is necessary to transmit intelligence out of the Reactor Protection and Safeguards System from process analog channels. The isolation amplifiers ensure that separation between protection and control functions is maintained.

Three standard production isolation amplifiers, Model 131-110, manufactured by Westinghouse Hagan Computer Systems Division, were tested at normal ambient temperature for isolation characteristics. The isolation amplifiers maintained input circuit integrity (protection circuit) for all disturbances applied both c.ommon mode an<l norm.:il mode to the out~11t circ11ir- In some cases, the output stage was damaged by the applied disturbance, but the protection circuit remain-ed functional and within design accuracy limits.

SECTION 1. 0 INTRODUCTION AND

SUMMARY

In Westinghouse NSSS, electrical and control equipment which initiates reactor trips or actuates safeguards systems, are independent, separate and redundant circuits.

All process analog channels in the plant protection and safeguards system are grouped into four protection sets. Each protection set contains not more than one analog channel of any redundant process measurement. The equipment com-prising each protection set is independent of and separated from each of the other protection sets. This protection equipment is normally located in the plant's main control room or an adjacent instrument room, except for the sensors, together with the remainder of the primary plant analog P.quipment.

In addition to separation from all other protection sets, each protection

  • set must be independent of and separated from all other control and electrical equipment groups within the*plant. Process analog equipment in this latter category is generally referred to as control equipment (as distinguished from protection equipment). However, certain process analog signals from channels within one protection set must be available outside the physical and electrical I t

boundary of the protection set. These signals are used to provide intelligence ['

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to data loggers, recorders, indicators and certain control channels. Isolation  :

i amplifiers (signal isolators) are used to insure that electrical separation f exists between the protection set and the remainder of the plant control f

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'I and electrical equipment.* r

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The isolation amplifier then becomes the electrical boundary of the protection set. For this electrical interface to be a valid isolation boundary it must be shown that electrical disturbances outside of the protection set will not

. in any way prevent the protection set from perforrn_ing its design function.

To demonstrate the ability of the Westinghouse signal isolator, model 131-110 to maintain the desired isolation,tests were performed using all voltages normally available in the analog system rack area as the disturbance applied to the output tenninals. The results are conclusive. At no time during the tests was an electrical disturbance greater than eleven millivolts (:0.25 per-cent of input span) observed at the input tenninals of the signal isolator.

The duration of this disturbance in all cases was less than 0.1 second. In no way would such a disturbance cause the protection channel to become in-operative.

This report has been prepared entirely on the basis of the information con-tained in Product Qualification_Report VR-9 Model 131-110 Signal Isolator, dated February 10, 1970, which is being retained by Westinghouse Hagan/Computer Systems Division, Pittsburgh, Pennsylvania.

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1-2

SECTION 2. 0 EQUIPMENT TESTED The isolation amplifiers subjected to isolation tests consisted of three Westinghouse Hagan Computer Systems Division (H/CSD) Signal Isolators, model number 131-110. The H/CSD assembly drawing number for this unit is 4111083.

The isolators tested for output-input isolation were randomly selected pro-duction units which had been used for product verification testing.

2.1 Circuit Description

--* To assure electrical isolation of the input circuit from the output, physically separate plugs are used to terminate the incoming and outgoing signals as shown in Figure 2.1. The. ph::s:!.cal outl:.r.e s"t-.Oi,.;n in Figure 2.2 is identical to other protection system rack mounted components.

Functionally, the isolation amplifier is shown (in simplified block diagram form) in Figure 2.3.

The output signal current is supplied through transformers T2 and T3 from the 1.5 kc oscill~tor. Transistor Q5 controls the output current by varying the conductance of these transformers. The output of current regulator Q5 is prop-portional to the input signal. The feedback signal for the current amplifier stage is obtained from the current across resistor R23. Changes in amplitude or frequency of the 1.5 kc oscillator do not affect the output current since current regulator Q5 maintains a constant current for a constant input signal.

The output transformer, T3, provides the isolation between input and output circuits. However, as with any transformer, this isolation between primary and secondary windings is not complete. A distributed capacitance, designated as CT in Figure 2.3, between these windings allows some electrical coupling between primary and secondary windings. The voltage divider consisting of capacitors ClO and CT determines the amount of disturbance in the input circuit 2-1

re~ulting from an alternating voltage applied. to the output current loop. The 6

ratio of these two capacitances is less than 0.5 x 10- and consequently the output to input alternating current attentuation at 60 Hz is better than -120 db.

The direct current isolation is essentially infinite until voltage breakdown occurs between the primary and secondary of T3. The breakdown voltage is greater than 600 VDC.

Figure 2-4 is a schematic diagram of the signal isolator.

2.2 Operational Specifications The following list of signal isolator specifications is provided as background information:

Input: 1-5 VDC Output: 4-20 ma into 0-1000 ohms Input Impedance: lOOK ohms Operating Temperature: +40°F to 120°F Power Supply: 117 + 10 percent VAC, 60 .+/- 2 percent Hz Powe:i: Consumption: 15 watts Accuracy: +0.5 percent of output span Frequency Response: Down 3 db at a frequency greater than 10 Hz Noise (RMS): 0.25 percent of output span Temperature Coefficient: 0.005 percent of output span per OF Line Voltage Coefficient: 0.005 percent of output span per volt Output-input isolation: For the following nominal disturbances on the output circuit, applied either common mode or normal mode, the input circuit disturbance shall not exceed the above stated accuracy Disturbance:

a. 48 VDC (applied both polarities)
b. 125 VDC (applied both polarities)
c. 120 VDC
d. 440 VDC

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f. Short circuit output 2-2

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SECTION 3. 0 TEST SCOPE Isolation tests were performed by applying electrical disturbances both common mode (between isolator output terminals and chassis ground) and normal mode (between positive and negative output terminals), The disturbances were applied with the isolation amplifiers operating at nominal design con-ditions of supply voltage and frequency and ambient temperature. The dis-turbances applied were as follow~:

(a) +48 VDC Normal mode (b) -48 VDC Normal mode (c) +llS VDC Common mode (d) l17 VAC Common mode (e) 460 VAC Common mode (f) Open &

Shorted Output Common mode (g) 117 VAC Normal mode (h) +120 VDC Normal mode (i) -120 VDC Normal mode (j) 460 VAC Normal mode 3.1 Test Procedure Each of the following tests were performed on a single isolator.

3.1.1 Set line voltage and frequency to reference conditions for this entire series of tests.

3-1

  • 3.1.2 Apply 1.0 VDC to the input of one signal isolator. Short the output for one minute, recording the input and output voltages on an oscillo-graph.

3.1.3 With 1.0 VDC on the input, open the output for one minute and record both input and output on an oscillograph.

3.1.4 Load the output of one isolator with 250 ohms and apply 1.0 VAC to the input. Connect the output of a loop power supply (H/CSD Model 121) across the output of the isolator for one minute. High side of power supply is to be connected to high side of isolator output. Record output, common mode input voltage and normal mode input voltage of isolator on an oscillo-graph. Record the exact.values of input and output voltages before and after applying the test voltage to the output.

3.1.5 Reverse the polarity of the loop power supply output and repeat 3.1.4.

3.1.6 Load the output of one isolator with 250 ohms and apply 1.0 VDC to the input. Apply +115 VDC common mode to high side of the output for one

.I minute. Connect the low side of the 115 VDC line to isolator chassis ground. Record output, common mode input, and normal mode input voltages of the isolator on an oscillograph. Record the exact _values of input and output voltages before and after applying the test voltage to the output.

3.1.7 Repeat 3.1.6 except apply the high side of the 117 VAC line to the high side of the isolator output and the low side to isolator chassis ground.

3.1.8 Repeat 3.1.6 except apply the high of the 460 VAC line to the high side of the isolator output and the low side to the isolator chassis ground.

1*

Note: The 115 VDC, 117 VAC and 460 VAC lines all have their neutrals connected to earth ground.

3-2

3.1.9 Repeat 3.1.6 except apply the high side of the 117 VAC line to the high side of the isolator output and the low side to the low side of the isolator output.

3.1.10 Repeat 3.1.6 except apply the high side of the 120 vnc line to the high side of the isolator output and the low side to the low side of the isolator output.

3.1.11 Repeat 3.1.6 except apply the high side of the 120 Vue line to the low side of the isolator output and the low side to the high side of the isolator output.

3.1.12 Repeat 3.1.6 except apply one phase of the 460 VAC line to the high side of the isolator output and another phase of the 460 VAC line to the low side of the isolator output.

3.1.13 Detail the damage resulting from each of the above tests.

I 3.2 Test Results All normal mode voltages are applied as shown in Figure 3.1. The common mode voltages are applied as shown in Figure 3.2. All input and output voltages are measured across a 250-ohm load resistor. Therefore, for the normal circuit span of 4 to 20 ma, a voltage of 1 to 5 VDC will be monitored. Thus, a change of + 0.5 percent of span is + 20 mv. The 250-ohm load resistor is identical to those normally connected across the output in actual operation.

3.2.1 Reference Figure 3.3, + 48 VDC Applied Normal Mode -- No detectable disturbance to input circuit. The unit continued to operate.

3.2.2 Reference Figure 3.4, -48 VDC Applied Normal Mode -- A +6 mv spike

(~0.1 second duration) appeared across the input terminals on application of the test voltage and a +2.5 mv spike c:o.1 second duration) occurred when the test voltage was removed. The unit remained operational and did not change value except as noted above.

3-3

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INPUT SIGNAL 250 OHMS OUTPUT SIGNAL } TEST VOLTAGE APPLIED HERE CHASSIS GROUND ISOLATED FROM INPUT AND OUTPUT SIGNALS Figure 3-1. Normal Mode Voltage Application

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INPUT ISOLATION AMPLIFIER 250 OUTPUT SIGNAL OHMS SIGNAL TEST VOLTAGE APPLIED HERE CHASSIS GROUND ISOLATED FROM INPUT AHO OUTPUT SIGNALS Figure 3-2. Commo~ Mode Voltage Application 3-4'

3.2.3 Reference Figure 3.5, +115 VDC Applied Common Mode -- A +5.5 mv spike c~o.1 sec duration) appeared across the input terminals when the test voltage was removed. The unit continued to operate normally after the test.

3.2.4 Reference Figure 3.6, 117 VAC Applied Common Mode A +9 mv spike (:0.1 sec duration) appeared across the input terminals on application of the test voltage and a - 5.5 mv spike c~o.1 sec duration) occurred when the test voltage was removed. The unit remained operational and did not change value except as noted above.

3.2.5 Reference Figure 3.7, 460 VAC Applied Common Mode A -2 mv spike (:O.l sec duration) appeared across the input terminals on application of the test voltage and a -4 mv.spike c~o.1 sec duration) occurred when the test voltage was removed. The unit remained operational and did not

--* 3.2.6 change value except as noted above.

Referense Figure 3.8, Open and Shorted Circuit Test -- ~o de~ectable disturbance to the input circuit. The unit remained operational.

3.2.7 Reference Figure 3.9, 117 VAC Applied Normal Mode A -2 mv spike (:O.l sec duration) appeared across the input terminals on application of the test voltage and a +9.5 mv spike (:O.l sec duration) occurred when the test voltage was removed. Damage occurred to the output circuitry rendering the unit inoperative. This did not impair normal operation of the input circuit. A tabulation of the failed components is given below. The order in which the components are listed does not necessarily represent the chronological sequence of component failure; this sequence was, in general, not determined~

3-5

Schematic Item Nature of Number (Ref. Fig. 2. 4) Type Component Failure Load Resistor (2501i!) Resistor Open 12 Choke (Inductor) Open D21 Diode Shorted D22 Diode Shorted D23 Diode Shorted D24 Diode Shorted 3.2.8 Reference Figure 3.10, +120 VDC Applied Normal Mode -- A +0.5 mv spike c~o.1 sec duration) appeared across the input terminals on application of the test voltage and a +l mv spike (O.l sec duration) occurred when the test voltage was removed. The unit remained operational after the test. Only the load resistor failed during the test.

3.2.9 Reference Figure 3.11, -120 VDC Applied Normal Mode -- A small spike of less thQn +0.5 mv (~0.1 S8C duration) appeared across the input ter-minals on application of the test voltage and a +2 mv c:o.1 sec duration) occurred when the test voltage was removed. Damage occurred to the out-

' put circuitry rendering the unit inoperative. This did not impair nor-mal operation of the input circuit. A tabulation of the failed compo-nents is given below:

Schematic Item Nature of Number (Ref.Fig.2.4) Type Component Failure 12 Choke (Inductor) Open Load Resistor (2501i!) Resistor Open D21 Diode Shorted D22 Diode Shorted D23 Diode Open D24 Diode Open 1.

3-6

3.2.10 Reference Figures 3.12 and 3.13, 460 VAC Applied Normal Mode -- A --1.5 mv spike (:O.l sec duration) appeared across the input terminals shortly after application of the test voltage. This was caused by failure of the output filter circuit. Within one second the load resistor failed causing a +5 mv spike (:O.l sec duration) to occur across the input terminals. Another positive spike (:10.2 mv and 0.1 sec duration) occurred approximately 45 seconds into the test. No spike occurred on removal of the test voltage. Damage occurred to the output circuitry rendering the unit inoperative. This did not impair normal operation of the input circuit. A tabulation of the failed components is given below:

Schematic Nature of Item Number Type Component Failure Load Resistor (250~) Resistor Open L2 Choke (inductor) Open D21 Diode Open D22 Diode Open D23 Diode Open D24 Diode Open C16 Capac tor Open cs Capac tor Shorted Damage to the Printed Circuit Card:

1. The conductor between R61 and E41 was burned open
2. The conductor between 12 and E44 was burned open
3. The conductor between D22 and E40 was burned open
4. Tie points E40 and E41 were missing
5. Conductors between E40 and E41 and connector J2 showed signs of excessive current In all the isolation tests, the input loop of the isolator remained operational and well within design limits. Areview of the failed components, resulting from the normal mode tests, shows that the damage was restricted to the output filter 3-7
    • stage and load resistor. The only exception to this was in the 460 VAC normal mode test where some damage occurred to the printed circuit board. The diodes, choke, and load resistor failed within 0.1 second after the test voltage was applied. After these components failed the 460 VAC was maintained by the output cable and capacitor Cl6 in the output filter for 45 seconds before a voltage breakdown at the tie points for the output cable on the printed circuit card destroyed this section of the card. Even with the extensive damage in the output section during the 460 VAC test the isolator input loop remained isolated and operational. There was an approximate negative 80 VDC common mode voltage recorded on the input loop when the voltage breakdown occurred. This voltage between signal ground and chassis ground will not be detrimental since the coupling capacitor between these two grounds in all the H/CSD Model 131-110 isolators is rated at 200 volts and all input circuits in the process analog protection sets are ungrounded.

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w Figure 3.6. Isolation Test 117 VAC (Common ~ode)

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Figure 3.8. Isolation Test Open &

Short Circuit

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Figure 3.13. Isolation Test 460 \'AC (:.:orr.,al :[ode)

SECTION 4.0 i '

CONCLUSIONS The specified accuracy of the isolation amplifier is +0.5 percent of span. At no time during the isolation tests did a disturbance of greater than +0.26 percent of span occur on the input circuit.

Damage occurred in the output circuit of the isolation amplifier only under normal mode testing. This rendered the output signal useless, however, this signal is used only for remote indication or control application where manual backup is available. The failures in the output circuit did not in any way disrupt normal operation of the input circuit of the isolator, and hence the protection set's ability to maintain the nuclear power plant in a safe con-dition.

I 'T-.

4-1

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