c09g0000 power limit monitor 1 (2)

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Technical Manual

Power Limit & Monitor Board

www.natoil.com

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CLIENT DOCUMENT NUMBER

lient Document Number C

P/N: C09G0000

REFERENCE REFERENCE DESCRIPTION

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contains proprietary andNational Oilwell; it is lo

y and remains the property of Nation lwell. Reproduction, inhole or in part; or use of this design or distribution of this

National-Oilwell L.P.1530 W. Sam Houston Pkwy. N

xas 77043

confidential informationed for limited purposeswh

onlanal Oi

winformation to others is not permitted without the express writtenconsent of National Oilwell. This document is to be returned toNational Oilwell upon request and in any event upon completion of the use for which it was loaned.© National Oilwell

Houston, TeUSAPhone +1 713 935 8000Fax +1 713 935 8382

DOCUMENT NUMBER

Document Number (ID) B

REV



Document numberRevision B

REVISION HISTORY

B 06.05.2005 Updated to New Template BKF

Rev Date (dd.mm.yyyy) Reason for issue Prepared Checked Approved

CHANGE DESCRIPTION

Revision Change Descript ion

A Initial ReleaseB Update to new template.

Tel: (713)-530-8800 Fax: (713)-530-8803www.natoil.com




www.natoil.com Tel: (713)-530-8800 Fax: (713)-530-8803

TABLE OF CONTENTS

1 DESCRIPTION.................................................................................................................. 4 2 FEATURES....................................................................................................................... 4

2.1 Inputs: See DWG #C09501B0 and C09401B0..................................................... 5 2.2 Outputs................................................................................................................... 6 2.3 Programming of Power Limiting.............................................................................. 7 2.4 Calibration of P1 (Rated KW) and P2 (Rated KVA)................................................ 8 2.5 Functional Description............................................................................................9 2.6 Power Factor........................................................................................................ 10 2.7

Block Diagram: See Dwg. #C09501B0............................................................... 11

2.8 Interconnection: See Dwg. #C09401B0.............................................................. 11





1 DESCRIPTION

The Power Limit & Monitor Bd. Is a quick-disconnect rugged module that provides KW,

KVA or KW/KVA Power Limit and monitoring for Engine/Generator/SCR systems. TheKW power limit guarantees that all engines are sharing the load and the KVA powerlimit, that the generators parallel correctly.

This module can work in conjunction with the Bus Overload Limit & Monitor Board, P/N:B10G0000, for power limiting the SCR converters.

2 FEATURES

The following is a list of the functions of the module:

1. Adjustment Pot. for rated KW.

2. Adjustment Pot. for rated KVA.

3. KW Power Limit Output.

4. KVA Power Limit Output.

5. KW/KVA Power Limit Output.

6. KW’s metering output.

7. KVAR;s metering output.

8. Current meter output.

9. Power Factor metering output.

10. Percent Power Available metering output.

11. Relay contact for KW, KVA or KW/KVA Over Limit.

12. Stand-Alone power supply.





2.1 Inputs: See DWG # C09501B0 and C09401B0

TB1 1, 2 AC Input . 120 vac.

TB1 3, 8 Common

TB1 4 +15 vdc.

TB1 5 -15 vdc.

TB1 6 Vcb. 120 vac. for full generator voltage.

TB1 7 Vab. 120 vac. for full generator voltage.

TB1 9 Ia. The voltage at t his terminal is given by the ratio of the CT utilized onphase C times 0.5. Where 0.5 is a burden resistor connected betweenthe terminal and common.

i.e. If a 1000 : 5 CT is used, then the voltage at the terminal will be:

5 X 0.5 = 2.5 vac.

TB1 10 Ic. See explanation for terminal TB1-9.

TB2 11 Rated KW Input from P1. See Dwg. #C09501B0.

TB2 12 Rated KVA Input from P2. See Dwg. #C09501B0.




2.2 Outputs

TB1 12 KW meter output. +5 vdc full scale, assuming that the CT’s used have a

5 Amps. Induced current at full load and also that the potentialtransformers have a secondary voltage of 120 vac at full generatorvoltage.

TB1 13 KW output. 0 to +10 vdc. With the assumptions described for TB1-12

TB1 14 KVAR output. -10 vdc to +10 vdc. With the same assumptionsdescribed for TB1-12.

TB1 15 KVAR meter output. -5.0 vdc. to +5.0 vdc full scale. Negative voltagefor lagging and positive voltages for leading. With the same assumptions

described for TB1-12.

TB1 16 Current meter output. This output gives an output of +5 vdc for fullamperage on the selected phase current in the Current Switch, See Dwg.#C09501B0. This is assuming that the CT’s utilized provide 5 Amps. of induced current when the AC Generator is delivering maximum power.

TB1 18TB1 19TB1 20

Over limit Relay Contact. This is a form C contact, where: #18 =common, #19 = N.C. and #20 = N.O. See Dwg. #C09501B0.

TB2 1 Percent of Power Available Meter . This output must be connected to TB2-1 of all other Power Limit & Monitor Boards in the system that is on-line, one per AC generator. See Dwg. #C09401B0. This output will be+5 vdc if the power available is 100% and it will decrease proportionally tothe power available in the system.

TB2 2 KVA power limit. This signal is active only after the AC generator is overits 100 % rating set by P2. The output will change by a ratio of +2 vdc forevery 10% of overload, +2 vdc for 110% KVA’s. This signal can be usedfor power limiting the SCR converters and so protecting the AC generator

from over loading by KVA’s.

TB2 5 Current Output. This output gives an out put of +10 vdc for fullamperage on the selected phase current in the Current Switch. This isassuming that the CT’s utilized provide 5 Amps. of induced current whenthe AC generator is delivering maximum power.





TB2 7 Rated KVA Output . This output will be +5 vdc for full rating of ACgenerator. The KVA AC generator rating must be previously set with P2.See the Calibration section.

TB2 9 Rated KW Output. This output will be +15 vdc for full rating of ACgenerator. The KW AC generator rating must be previously set with P1.See the Calibration section.

TB2 12 KW power limit. This signal is active only after the AC generator is overits 100 % rating set by P1. The output will change by a ratio of +2 vdc forevery 10% of overload, +2 vdc for 110% KW’s. This signal can be usedfor power limiting the SCR converters and so protecting the dieselengines from overloading by KW’s.

TB2 13 Power Factor Meter Output. This signal swings from -5 vdc to +5 vdc fullscale, for a power factor of .5 lagging to .5 leading. This signal is non-linear and follows a cosine function. The negative sign is for laggingpower factor and the positive for leading. The output voltage relates tothe power factor as follows:

Power Factor = Cosine VOLTAGE AT TB2-13 X 605

* Cosine Argument is in degrees.

2.3 Programming of Power Limi ting

The Power Limit & Monitor Module has the flexibility of power limiting by KW’s, KVA’sor by both, which in the last case, whichever gets greater than the maximum set by P1and P2, it will command the power limiting.

KW Power Limiting

Output terminal: TB2-12.

J umper: Between TB2-4 and TB2-8.

In this case the Over Limit Relay will detect KW’s limit only.






KVA Power Limit ing

Output terminal: TB2-2.

J umper: Between TB2-3 and TB2-6.

In this case the Over Limit Relay will detect KVA’s limit only.

KW and KVA Power Limiting

Output terminals: TB2-2 or TB2-12.

J umpers: Between TB2-2 and TB2-12, TB2-3 and TB2-6, and alsobetween TB2-4 and TB2-8.

In this case the Over Limit Relay will detect KVA’s and KW’s limit.

2.4 Calibration of P1 (Rated KW) and P2 (Rated KVA)

Define the following parameters:

KWN = Rated KW of engine.

VN = Nominal Voltage.

CTR = Current Xformer primary rating.

KVAN = Rated KVA of Genrator.

P1: Rated KW Setting.

The setting of P1 will be calculated based on the parameters specified above. The value will be in “Kohms”. To set P1, it will be necessary to disconnect thecable from the module at TB2-11, and then adjust P1 to the calculated ohmicvalue.

P1 (Kohms) = 25 X A _ 10 = Kohm5 – A

A = 5 X KWN X 10001.73 X Vin X CTR





P2: Rated KVA Setting.

The setting of P2 will be calculated based on the parameters specified above.

The value will be in “Kohms”. To set P2, it will be necessary to disconnect thecable form the module at TB2-10, and then adjust P2 to the calculated ohmicvalue.

B = 2.2 X KVAN X 10001.73 X VN X CTR

P2 (Kohms) = 25 X B _ 5 = KOHM5 – B

2.5 Functional Description

NOTE: One of this modules should be utilized per engine/generator set to providepower limiting to the SCR converters. For electrical interconnections referto Dwgs. #C09501B0 and C09401B0.

KW’s The Power Limit & Monitor module continuously calculates the kilo-wattsdelivered by the AC generator to th e load and when programmed it canpower limit the SCR converters to prevent overloading of the dieselengines.

The kilo-watts is the real force that produces work and when the loaddemands more than the capacity of the diesel engines, which are thesuppliers of this power, they can be overloaded and if this happens theirspeed will start decreasing which will force the generator’s control to openthe main circuit breaker by under-voltage or under-frequency. This inturn, can cause the other engine/generator sets to get overloaded, and asa result having a complete blackout.

KVAR’s The Power Limit & Monitor module provides and putput of the Kilo-volt-ampere-reactive for metering.

The kvar’s is a component of power supplied by the AC generator thatdoes not produce actual work and produces low power factor. KVAR’sincreases with bigger inductive or capacitive loads on the AC generator.




KVA’s The Power Limit & Monitor module also continuously calculates the kilo-volt-amperes delivered by the AC generator to the load and whenprogrammed it can power limit the SCR converters from overloading theAC generator.

The kilo-volt-amperes is the total power delivered by the AC generator tothe load and this includes the KW’s and KVAR’s. AC generators arerated in Kilo-volt-amperes rather than in kilo-watts, because their lossesand heating are very nearly determined by voltage and current regardlessof power factor.

In an AC generator, if the load requires more kilo-volt-amperes than themaximum capacity of the AC generator, it will get overloaded and itsvoltage will start decreasing, which in turn can cause the main circuitbreaker to open by undervoltage, and like with the KW’s overloading, starta complete blackout.

2.6 Power Factor

The Power Limit & Monitor module continuously calculates the power factor formetering purposes.

Power Factor is a measure of the phase shift between the voltage generated by an ACgenerator and the current it delivers. Inductive loads, like motors, produce a lag currentwith respect to the voltage. And capacitive loads, like over-excited AC generators,produces a lead current with respect to the voltage. A purely resistive load or a load

with equal inductive and capacitive components does not produce lag or lead of thecurrent with respect to the voltage.

Power Factor = Cosine Phase Shift, in degrees, betweenthe voltage and current.

A lag current produces a positive argument for the Cosine function and a lead current anegative.

The supplied power factor in SCR converters is low when the output voltage is lessthan the maximum that is when the firing angle large. AS the firing angle increases, thedisplacement angle between voltage and current increases and the converter drawsmore lagging reactive power, thereby decreasing the power factor. Low power factormeans more current and greater copper losses in the AC generator and it producespoor voltage regulation as well.






2.7 Block Diagram: See Dwg. # C09501B0

2.8 Interconnection: See Dwg. # C09401B0

c09g0000 power limit monitor 1 (2)

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