INSTRUCTION MANUAL FOR
RPM-8 Reactive Power Manager Relay – 8 Stage
Sl.No. Topic Description
Installation & Wiring
Settings & Programming
Display & Menu Operations
Alarms in RPM-8
Appendix-1 Guidelines for Cap. Bank selection
Appendix-2 Effect of high rate of load fluctuation
1.0 INTRODUCTION Reactive Power Manager Relay (Model RPM-8) is designed for automatic control of capacitor banks in 3 phase 4 wire LT distribution systems. The relay maintains the system power factor at a set value, under fluctuating load conditions, by connecting or disconnecting capacitor banks to the 415V bus. The relay employs state of the art micro controller design for measurement of reactive power compensation required, system power factor, voltage and current. A specially formulated optimization program for capacitor bank switching ensures accurate power factor control at the set point and hunt free operation. RPM-8 is designed to control up to 8 capacitor banks. The front panel arrangements and other features of the unit are explained in the following sections: 1.1
Non uniform Banks: RPM-8 can accept capacitor banks whose values are at random (i.e.) it is not necessary to connect banks in ratios of 1: 1: 1: or 1: 2: 2: or 1: 2: 4: …etc. The kVAR ratings of the banks can be in any random denomination. It is not necessary that the banks should be in multiples of the smallest bank. This feature helps in providing maximum kVAR compensation with least number of banks (the number banks can go up to 8) ………2
-2Bank Configuration: The user will have facility to enter the bank size of each bank (in kVAR) at the time of commissioning. Any bank which is not connected will have to be entered as zero kVAR. The banks whose values are entered as zero will be treated as unconnected banks. The relay will not switch these „zero value‟ banks in its normal operation. Consequently the time for PF correction will be minimized.
Automatic c/k selection: The user need not perform complicated mathematics to calculate c/k ratio and set in the relay. The relay will do the PF correction without the need for c/k ratio. It automatically calculates the threshold kVAR by taking into account the bank values already entered. Hence there is no need to set the c/k ratio.
Accurate display of Power Factor: The unit uses a specially designed measurement circuit, which facilitates accurate measurement and steady display of PF, even in conditions where harmonics are present.
Optimization of connected banks: RPM-8 will constantly monitor the kVAR compensation required and select the right combination of banks to ensure that the plant PF is maintained very close or equal to the set value.
Hunt Free operation: A unique optimization program for bank switching, combined with online monitoring of total reactive compensation required as mentioned above, ensures that the relay does not hunt at a bank value during load fluctuations. ………3
Multi parameter Display: RPM-8 has a 4 digits, seven segment, super bright LED display on the front panel. The unit shows the plant PF as a default display. On demand, the unit can also display feeder current, bus voltage, kVAR, settings and bank values.
Measurement sensitivity of 1%: The unit can continue PF correction even when the load current goes up to 1% of the rated value. Thus PF correction is ensured even in very low load conditions (like in night times or during the initial stages of a plant commissioning).
Alarms: RPM-8 provides an alarm contact whenever there is an abnormality – like over voltage, under current, CT polarity reversal, over compensation and under compensation.
1.10 Design Philosophy: RPM-8 uses a unique combination of two powerful, state of the art integrated circuits – one for doing analog measurements accurately and the other for doing the peripheral functions efficiently. The analog IC carries out the measurement of Voltage, current, active energy and apparent energy with the accuracy levels required in energy measurement instruments. The measured values are transferred to a high memory micro controller with built in EEPROM – which carries out the peripheral functions like display, switching logic and push button access for menu options. Consequently, the circuit has very few components, which increases the reliability of the device as a whole. ………4
2.0 INSTALLATION & WIRING 2.1
Preliminary checks: The relay package consists of: - 1 no. RPM-8 Relay - 2 nos. mounting clamps - 1 no. Instruction Manual - 1 no. Test certificate Check the RPM-8 relay for any damage. If damaged, please inform nearest L&T office or dealer. If found OK, follow the instructions below for basic functional checks: a) Remove the terminal cover from the rear terminal block and Connect 240 V AC supply at terminals 1 & 2. b) Switch on the supply voltage. The display will show PFR8, the power factor and then the error code uCrr. The LEDs marked Auto and Alarm will glow continuously. All other LEDs will remain off. If the unit has passed above checks, it is ready for panel mounting.
MOUNTING ON PANEL: RPM-8 relay is designed for flush mounting on any control panel. Please refer to the dimensional drawing shown below for understanding the overall & cutout dimensions of RPM-8.
Provide a cut-out of 138mm x 138 mm on the panel. Push the RPM-8 relay through the cut out and fix the relay to the panel by means of the two mounting clamps. ………6
WIRING OF RPM-8 RELAY ON PANEL: Please refer wiring diagram shown below (the same is affixed on top side of the unit). There are 4 groups of connections as explained below:
a) Auxiliary supply to RPM-8: Please connect R phase voltage of the capacitor bank panel to terminals 1 & 2 of the unit. Please note that it should be 240 V AC 50 Hz supply (Phase to neutral voltage). Phase is connected to 1 terminal and neutral is connected to the 2 terminal of the unit. RPM-8 uses this supply as the auxiliary supply for electronic circuit as well as measuring voltage for PF and kVAR computation. ……7
-7b) CT input to RPM-8: The unit is suitable for connecting to CT secondary of either 1A or 5A rating. Please ensure that the CT is on R phase. CT secondary is to be connected as follows: 1A rating – Terminals 8 & 9 5A rating – Terminals 7 & 9 c) Supply to Capacitor Bank contactor coil supply: RPM-8 is meant for connecting up to 8 capacitor banks through external contactors. Consequently it provides 8 relay contact outputs. - One terminal of all 8 contactor coils is to be connected to neutral of the contactor coil supply. - The other terminal of each of the contactor coil has to be connected to RPM-8 terminals 17 to 24 as shown in the wiring diagram. - The phase supply of contactor coil should be connected to terminal 14 of RPM-8 d) Alarm Circuit: RPM-8 provides a change over contact at terminals 4, 5, 6. this is an 8A rated contact and can be used for energizing a buzzer.
Note: Please ensure that: a) The auxiliary supply is 240 V ac b) The CT is on the same phase as the auxiliary supply c) Earth connection to the relay is provided properly ………8
-8The relay terminals are suitable for 2.5 sq.mm lugs. After completing the wiring, fix the protective cover back on the terminal block with the help of 4 screws.
SETTINGS & PROGRAMMING
FRONT PANEL OF RPM-8 As shown in Fig. 1 on page 9, the front panel of RPM-8 has the following provisions:
3.1.1. 4 digit seven segment LED display: The on line measured values and various set values will be displayed in the seven segment display. The default display is the plant PF. All other parameters are to be read by manipulating the PBs as explained in Section 4. 3.1.2
A row of 8 nos. Capacitor bank status LEDs: The row of 8 LEDs will indicate Capacitor bank (CB) on / off status. Since the relay is meant for connecting up to 8 stages of capacitor banks, there are 8 LEDs in a row, each with the bank number associated with it. If a particular LED is on, the respective CB is switched on. If the LED is off, the respective CB is switched off. For example, if LED 4 is on, capacitor bank 4 (CB04) is switched on. ………9
-103.1.3 A column 5 nos. Plant status Leeds: The column of 5 LEDs indicates the plant status. “Lead” LED will be ON during leading PF in the plant. “Lag” LED will be ON during lagging PF in the plant. “Auto” LED will be ON at all times, except when the PBs are pressed for some kind of manual operation. This LED indicates that the RPM-8 relay is in auto mode of PF correction. “Manual” LED will come ON whenever the RPM-8 relay is taken in to manual mode of operation. “Alarm” LED will come ON if the plant goes into any of the alarm conditions as explained in Section 6.
3.1.4 Push buttons (PBs): The 4 PBs, marked as “Menu”, “▲”, “▼”, and “Enter” are used to view display parameters, settings in the relay and to change / programmed the settings in the relay as is explained in detail in Section 4. ………11
DISPLAY & MENU OPERATIONS RPM-8 will display plant PF at all times as a default display. The user can also view and programme many other parameters as explained in following sections.
Main Menu: Connect auxiliary supply to RPM-8. Press the PBs in the sequence shown in the table below and observe the respective displays. Operation Press Menu Press ▲ Press ▲ Press ▲
Display d.dAt d.SEt P.SEt d.dAt
It can be seen that, when the Menu PB is pressed, it opens up three more sub menu options namely: a)
d.dAt : In this option, RPM-8 displays on line data.
d.SEt : In this option, RPM-8 displays all the parameter Settings.
P.SEt : In this option, user can change the set parameters. (Programme settings). ………13
Online value display - d.dAt menu options: As mentioned earlier, this sub menu helps user to view on line values. Following table shows the procedure to view on line values: Display of measured values Operation Display Press Menu d.dAt Press Enter volt Press Enter 0246 Press Enter Cur Press Enter 0127 Press Enter vAr Press Enter 0056 Press Enter volt
Remarks Displays value of phase to neutral voltage of the bus. Displays value of feeder Current Displays plant kVAr value Repeat show
Parameter settings display - d.SEt menu options This sub menu helps the user to view all settings of various feeder parameters as listed below: Display of parameter settings Operation Display Press Menu d.dAt Press ▲ d.Set Press Enter TrPF Press Enter 00.98 CtSl Press Enter Press Enter 0005 Press Enter Ctrt Press Enter 0050 Press Enter Td Press Enter 0030 Press Enter Cb01 Press Enter 0005 Press Enter Cb02 Press Enter 0010 Press Enter Cb03 Press Enter 0015 Press Enter Cb04 Press Enter 0020
Remarks Choose dset option Display of Target PF Display of CT secondary rating (1A or 5A) Display of feeder CT ratio Display of interbank Switch on delay (sec) Display of kVAR connected at Bank1 Display of kVAR connected at Bank2 Display of kVAR connected at Bank3 Display of kVAR connected at Bank4 ……….15
-15Display of parameter settings (contd…) Operation Display Remarks Press Enter Display of Cb05 connected at Bank5 Press Enter 0025 Press Enter Display of Cb06 connected at Bank6 Press Enter 0030 Press Enter Display of Cb07 connected at Bank7 Press Enter 0040 Press Enter Display of Cb08 connected at Bank8 Press Enter 0050 Press Enter Repeat show TrPF 4.4
kVAR kVAR kVAR kVAR
Parameter programming - P.SEt menu option: This option helps the user to programme the feeder parameters in RPM-8. Once the feeder parameters are entered correctly, the RPM-8 will do PF correction automatically, 24 hours a day. Before entering into this menu, please keep the following feeder related values at hand. - the CT ratio - kVAR values of all banks connected at stages 1 to 8 - recommended time delay in sec. for inter bank switch on - target PF required to be achieved Since Programming/changing the set values in the RPM-8 is an authorized function, entry into P.Set option is made tricky. Please refer table below for entering into PSEt option and do programming. ………16
-16Parameter Programming – P.SEt Menu Operation Display Remarks Press Menu d.dAt Press ▲ Choose d.set option d.Set Press ▲ Choose P.set option P.Set Press Enter, then ▼, TrPF Ready to change target and release Enter pF setting Press Enter Set value of target PF 00.95 (00.95) will flash (flash) Press ▲ for increase The trPF value is or ▼ for decrease of 00.98 changed to 00.98 (will display value trPF remain flashing) (flash) Press Enter (after New trPF value is reaching the desired CtSl registered. Next setting value for trPF CT sec. ready is ready to setting) be changed. Press Enter The set value of CT sec 0005 (0005) will flash (flash) Press ▲ for increase The new CtSl value is or ▼ for decrease of 0001 changed to 0001 (1A) display value Ctrt (will remain flashing) (flash) Press Enter (after Ctrt The CtSL value is reaching the desired registered. Next setting value of CtSL sec CT ratio is ready to be setting) changed ………17
-17Parameter Programming (contd…) Operation Display Remarks Press Enter The set value of CT ratio 0250 (0250) will flash (flash) Press ▲ for increase The new Ctrt value is or ▼ for decrease of 0300 changed to 0300 (will display value Ctrt remain flashing) (flash) Press Enter (after Td The Ctrt value is reaching the desired registered. Next setting value for Ctrt Cap. Bank switch on setting) time delay is ready to be changed Press Enter The set value of time 0035 delay (0035) will flash (flash) Press ▲ for increase The new td value is or ▼ for decrease of 0030 changed to 0030 sec display value td (will remain flashing) (flash) Press Enter (after The td value is reaching the desired Cb01 registered. Next setting, value for td setting) Bank 1 kVAR value is ready to be changed. Press Enter Already set value of 0001 Bank 1 kVAR (0001) (flash) will flash Press ▲ for increase CB01 value is changed to or ▼ for decrease of 0005 0005 kVAR display value Cb01 (will remain flashing) (flash) ………18
-18Parameter Programming (contd…) Operation Display Remarks Press Enter (after The new Cb01 value is reaching the desired Cb02 registered. Next setting, value for Cb01 Bank 2 kVAR value is setting) ready to be changed. Press Enter Already set value of 0003 Bank 2 kVAR (0003) (flash) will flash Press ▲ for increase CB02 value has been or ▼ for decrease of 0010 changed to 0010 kVAR display value Cb02 (will remain flashing) (flash) Press Enter (after The new Cb02 value is reaching the desired Cb03 registered. Next setting, value for Cb02 Bank 3 kVAR value is setting) ready to be changed. Press Enter Already set value of bank 0006 3 kVAR (0006) will flash (flash) Press ▲ for increase CB03 value has been or ▼ for decrease of 0015 changed to 0015 kVAR display value Cb03 (will remain flashing) (flash) Press Enter (after The new Cb03 value is reaching the desired Cb04 registered. Next setting, value for Cb03 Bank 4 kVAR value is setting) ready to be changed. ………19
-19Parameter Programming (contd…) Operation Display Remarks Press Enter Already set value of bank 0008 4 kVAR (0008) will flash (flash) Press ▲ for increase CB04 value has been or ▼ for decrease of 0020 changed to 0020 kVAR display value Cb04 (will remain flashing) (flash) Press Enter (after The new Cb04 value is reaching the desired Cb05 registered. Next setting, value for Cb04 Bank 5 kVAR value is setting) ready to be changed. Press Enter Already set value of bank 0010 5 kVAR (0010) will flash (flash) Press ▲ for increase CB05 value has been or ▼ for decrease of 0025 changed to 0025 kVAR display value Cb05 (will remain flashing) (flash) Press Enter (after The new Cb05 value is reaching the desired Cb06 registered. Next setting, value for Cb05 Bank 6 kVAR value is setting) ready to be changed. Press Enter Already set value of bank 0015 6 kVAR (0015) will flash (flash) Press ▲ for increase CB06 value has been or ▼ for decrease of 0030 changed to 0030 kVAR display value Cb06 (will remain flashing) (flash) ………20
-20Parameter Programming (contd…) Operation Display Remarks Press Enter (after The new Cb06 value is reaching the desired Cb07 registered. Next setting, value for Cb06 Bank 7 kVAR value is setting) ready to be changed. Press Enter Already set value of bank 0020 7 kVAR (0020) will flash (flash) Press ▲ for increase CB07 value has been or ▼ for decrease of 0035 changed to 0035 kVAR display value Cb07 (will remain flashing) (flash) Press Enter (after The new Cb07 value is reaching the desired Cb08 registered. Next setting, value for Cb07 Bank 8 kVAR value is setting) ready to be changed. Press Enter Already set value of bank 0025 8 kVAR (0025) will flash (flash) Press ▲ for increase CB08 value has been or ▼ for decrease of 0040 changed to 0040 kVAR display value Cb08 (will remain flashing) (flash) Press Enter (after The new Cb08 value is reaching the desired TrPF registered and the menu value for Cb08 will return to the first setting) parameter, the target PF ………21
-21As can be seen, there are a total of 11 parameters to be set in the relay RPM-8 for satisfactory PF control.
RPM-8 OPERATION Main objective of RPM-8 relay to perform PF control in a LT sub-station, by adding or deleting capacitor banks to / from a three phase 415V bus. RPM-8 can work in two modes - Auto and manual mode.
Operation in Auto mode: Whenever powered on, RPM-8 goes into auto mode operation by default (since its function is to correct power factor automatically). No special activity is required to bring the unit to auto mode. In this mode, the unit continuously displays the plant PF, measures the required kVAR for compensation and carries out the power factor correction as per set parameters automatically, without any intervention from the operator.
Operation in Manual mode: In this mode the user can add or delete capacitor banks by pressing the PBs on the front panel of the RPM-8. The main purpose of providing this feature is to check the wiring of RPM-8 to various banks, while commissioning. Procedure for manual operation is explained in following table. ………22
-22Manual addition of Capacitor banks from RPM-8 Operation Display Remarks Press Menu d.dAt Press ▲ Choose dset menu d.Set Press Enter TrPF Display of target PF Press Enter 00.98 Press Enter CtSL Display of CT Ratio Press Enter 0005 Press Enter Ctrt Display of CT sec. Rating Press Enter 0250 Press Enter Td Display of time bank switching time delay Press Enter 0030 Press Enter Cb01 Display of Bank 1 kVAR value Press Enter 0005 Press ▲ Bank 1 will be switched on. 0005 Press ▼ Bank 1 will be switched off. 0005 Press Enter CB02 Display of Bank 2 kVAR Press Enter 0010 Press ▲ Bank 2 will be switched on. 0010 Press ▼ Bank 2 will be switched off. 0010 Press Enter CB03 Display of Bank 3 kVAR Press Enter 0015 ……….23
-23Manual addition of Capacitor banks from RPM-8 (Contd.) Operation Display Remarks Press ▲ 0015 Bank 3 will be switched on. Press ▼ 0015 Bank 3 will be switched off. Press Enter CB04 Display of Bank 4 kVAR Press Enter 0020 Press ▲ 0020 Bank 4 will be switched on. Press ▼ 0020 Bank 4 will be switched off. Press Enter CB05 Display of Bank 5 kVAR Press Enter 0025 Press ▲ 0025 Bank 5 will be switched on. Press ▼ 0025 Bank 5 will be switched off. Press Enter CB06 Display of Bank 6 kVAR Press Enter 0030 Press ▲ 0030 Bank 6 will be switched on. Press ▼ 0030 Bank 6 will be switched off. Press Enter CB07 Display of Bank 7 kVAR Press Enter 0035 Press ▲ 0035 Bank 7 will be switched on. Press ▼ 0035 Bank 7 will be switched off. Press Enter CB08 Display of Bank 8 kVAR Press Enter 0040 Press ▲ 0040 Bank 8 will be switched on. Press ▼ 0040 Bank 8 will be switched off. ………24
It should be noted that, RPM-8 goes to manual Mode, only when any PB is pressed on the front panel. If no PB is pressed for more than 30 sec (approx.), the unit returns to Auto mode by itself. In manual mode, the unit does not perform any measurement or PF correction. The operator is expected to do the PF correction by manually adding / deleting the capacitor banks. In case it is required to do PF correction in manual mode for a long duration, following provisions should be made on the PF correction panel. a) A pair of dedicated On/Off PBs for each capacitor bank b) An Auto/Manual switch - This switch has to be kept in Auto position when the PF correction is to be done automatically by RPM-8. Wiring should be such that, the phase supply of all contactor coils will be connected to terminal 14 of RPM-8 only if the this switch is in auto position. -
The switch is to be kept in manual position, when capacitor banks are to be added / deleted manually. When in manual position, the phase supply of all contactor coils will be disconnected to terminal 14 of RPM-8. ………25
-25Thus the RPM-8 will be prevented to do any capacitor bank addition /deletion. However, the operator is free to add / delete the capacitor banks by means of the dedicated PBs on the main control panel. The RPM-8 will keep indicating the PF and guiding the operator as to whether the target PF has been reached or not.
ALARMS IN RPM-8 RPM-8 is designed to provide alarms under 5 abnormal conditions. The alarm will be in the form of a change over contact output at terminals 4, 5, 6 and an error code display on the front seven segments LED. Following are the details of alarms.
CT polarity reversal ( Ctrv ) : As explained earlier, the RPM-8 needs a 240 V AC input and 1A/5A CT secondary input for measuring PF and kVAR. Both these inputs must be from the same phase in the APFC panel. Some times the polarity of S1 & S2 terminals of CT may be reversed when connecting the CT input to RPM-8. If this happens, the PF calculations will go wrong. RPM-8 has a built in check system for detecting CT polarity problem at the commissioning stage itself. Immediately after power on, with all banks in switched off condition, the unit will show Ctrv display if there is a CT reversal. At the same time the alarm contact will come on. This alarm is indicated only for first 30 second. ………26
-26If this alarm is observed following must be done: a) Switch off the voltage connection b) Short the CT secondary terminals at the terminal strip at bottom of the panel c) Interchange the CT connection at terminals 9 & 7of RPM-8 d) Power on again and ensure that the alarm is off. 6.2
Under Current Alarm (Ucrr): RPM-8 is designed to work up to a load current level of 1% of rated value. Some times this current can go even below 1% - any PF correction at this stage may take the plant to leading PF state for a long time - which may not be desirable. RPM-8 gives an alarm Ucrr under such conditions – and all the capacitor banks will be switched off so that plant PF does not go to leading PF unnecessarily.
Over Compensation alarm ( OCPn ): Many times, if the load is small, the PF may go lead even without the least capacitor bank on. This is a case of over compensation – this will result in pulling down average PF of the plant. RPM-8 will give OCPn alarm under such condition
Under compensation ( UCPn ) There can be condition (particularly when the plant is on full load) that all 8 banks are switched on – but the target PF is not reached. ………27
-27This is a clear indication that the capacitor banks, as sized, are inadequate for the plant. Under such conditions, RPM-8 will give UCPn alarm – so that user can re-configure the capacitor bank sizes. 6.5
Over Voltage alarm ( OvoL ) RPM-8 has a built in over voltage protection at +20% of rated voltage (288 V). If the input voltage exceeds the 2885 V point, the RPM-8 will give OvoL alarm. At the same time all banks will be switched off so that, the capacitor banks are saved from exposure to over voltages.
TECHNICAL SPECIFICATIONS OF RPM-8 Voltage Input Current Input
240V AC 15%, 50 Hz, 5A / 1A from CT secondary (Field selectable)
50 Hz 2.5%
Accuracy of PF Display
1% ±1digit between 0.7 lag to 0.8 lead other ranges 2% ±1digit.
Accuracy of other 2% ± digit Display Parameter Target PF setting CT ratio
0.7 lags to 0.9 lead For 1 Amp secondary 1 to 6400 For 5 Amp secondary 1 to 1280 Threshold reactive Auto Current setting (C/K ratio) Bank selection
Relay will recognize number of Connected banks automatically
Bank configuration Suitable for non-uniform cap. Banks Safety lock out time 30 sec 10% Auto / Manual Operation
-29Capacitor bank a) 1 to 250sec in steps of 1 sec Switching on delay for switching between two different banks b) 60 sec for same Bank switching (Timing Accuracy ± 10%) Operational Indicators
LEDs for all relays‟ status LED for `ALARM` LED for `AUTO/MANUAL` LEDs for Lead / Lag Four 7-segment displays for display of Plant PF, Current, kVAR, ALARM-Codes, capacitor bank values, Target PF, and Time delay for switching.
Power Factor Control Range
From 1% to 120% of rated current
< 0.3 VA at CT input at nominal voltage < 15VA at PT input at nominal voltage
Out put contacts
8 nos. N/O contacts for bank contactor switching 1 N/O for alarm ………30
250V AC, 5A for bank contactor switching, 250V AC, 6A for alarm
Resistance to As per IEC 255-21-1/2 Class 1 Vibration &Shocks Temperature
Operating Temperature 00 to 600 C Storage temperature -200 to 700 C
Case Front Bezel Panel Cutout Depth
144 x 144 mm 138 x 138 mm 100 mm
2 kg approx.
Electrical Performance specifications: a) Insulation As per IEC 60255-5, 2 kV AC, RMS, 50 Hz for one minute across independent circuits & 1 kV AC, RMS, 50 Hz for one minute across open contacts b) Impulse withstand 5 kV (CM), 2kV (DM) peak, 1.2/50 micro sec, as per IEC 60255-5
-31c) Surge Immunity As per IEC 61000-4-5, Level 4, 4 kV (CM), 2kV (DM) d) Electrical fast Transient As per IEC 60255-22-4, 2 kV, 5 kHz e) Conducted Disturbance As per IEC 61000-4-6, Level 3, 10V, 150 kHz to 80 MHz f) Electro Static Discharge As per IEC 60255-22-2, air discharge 8 kV g) Immunity to voltage Variations, dips and short Interrupts As per IEC 61000-4-11, 200 ms
WARRANTY LARSEN & TOUBRO LIMITED (L&T) warrants that the protective Relay model RPM-8 will meet L&T„s published specifications and will be free from defects in workmanship and materials for a period of 12 months from the date of shipment. L&T‟s obligation under this warranty shall be limited to servicing or replacing the defective parts provided that notice of such defects and satisfactory proof thereof is given to L&T by it‟s customer within the warranty period. This warranty does not cover any defect caused by accident, misuse, neglect alteration, modification or substitution of any of the components or parts or any attempts at internal adjustment by unauthorized service personnel. Under no circumstances shall L&T be liable for any consequential damage, resulting injury, loss or expense, directly or indirectly, arising from the use of this product. This forgoing warranty is in lieu of all other warranties expressed or implied and is the sole and exclusive remedy for any claim arising from the defect in the product. ……….33
Appendix-1 Guidelines for selection of Capacitor Bank size: The RPM-8 relay will continuously evaluate the required kVAR compensation and keep adding to the bus- thus bringing the plant PF close to the set value. Some times, in operation, RPM-8 may not find the closest match for the required kVAR and may stop adding. This may result in a PF much less than the set target. In order that RPM-8 brings the plant PF closest to target PF, the system should have right denomination of capacitor banks as required by the load conditions of the plant. To determine, the right denomination of bank sizes (8 in total), following approach may be followed: Plant kVAR requirement >100kVAR Bank Size (kVAR) no. 1 X 2 2X 3 3X 4 5X 5 10X 6 20X 7 30X 8 40X
Plant kVAR requirement < 100kVAR Bank no. Size (kVAR) 1 2 3 4 5 6 7 8
X X 2X 2X 3X 5X 10X 15X ………34
Appendix-2 Effect of high rate of load fluctuation on PF control: RPM-8 corrects PF by adding or deleting the connected capacitor banks. As per the requirement of standards for Capacitor banks, the banks are switched on / off with a set time delay. This inter bank switch on delay is normally of the order of 15 to 30 sec. In case the loads are fluctuating faster than this 15 sec, the time delay can be reduced to the order of 5 sec. However, whenever the same bank is switched on, the delay is preset to 60 sec as required by the Standards. It can now be seen that whenever the load fluctuates in less than 15 sec period, the switching action of RPM-8 may not match with the correction requirements. This is mainly because, the load changes before the action of RPM-8 is completed- with the result that RPM-8 may not add capacitor at all. This will lead to a situation where despite installing RPM-8, there is a large gap between the target PF and actual plant PF reached – like target PF may be 0.95, actual may be 0.87. It should be noted that RPM-8 has brought the plant PF up to 0.87 – it is not able to improve because it is not able to add additional capacitors due to rapid fluctuations in load. This is particularly true for small plants where the total kVAR itself is less than 10 kVAR. For such applications it is advisable to have more small value bankslike 1 kVAR, 1.5 kVAR etc. Alternately it is better to have individual capacitors connected across each load.
Manufactured by LARSEN & TOUBRO LIMITED, KIADB INDUSTRIAL ESTATE, HEBBAL, HOOTAGALLY, MYSORE – 570 018. INDIA. Visit us
@ www.lntmps.com www.lntebg.com www.larsentoubro.com Reach us @ [email protected]
4D060111 Rev. 4