INSTRUCTION MANUAL FOR

MC31A DUAL RATED CT

3 Phase Over Current and Earth Fault Relay

CONTENTS

Description Page No. 1. Introduction 1 2. General characteristics

2.1 Non volatile Memory 1 2.2 Auxiliary Power Supply Range 1 2.3 Relay outputs 2

2.4 Starter Relay 2 2.5 CT Ratings 2

2.6 Trip time Characteristic Curves 3 2.7 Current measurements 3 2.8 Event Recordings 4 2.9 Diagnostics 4 2.10 Signalization 4 2.11 Reset Time 5

3. Installation & Maintenance 3.1 Preliminary checks 6 3.2 Mounting & Wiring 6

3.3 Testing 7 3.4 Handling Precautions 7 3.5 Fault Detection & Repair 8

3.6 Instructions for Draw-out & Plug-in 8

4. Operation 4.1 Push button and Display operation 11 4.2 Menu operations 11 4.3 Recording of Tripping 12 4.4 Recording of current Values 13 4.5 Display of settings 13

Display of Parameter settings Display of relay configuration CT ratio settings Erase the recorded values

4.6 Programming of the settings 15

Programming of the parameter settings Programming the relay configurations Erasing the Recorded Values Programming of CT Ratings 4.7 Test 18 5. Technical Specifications 19 6. Wiring Diagram 23 7. Overall Dimensions 24 8. Time current Curves 25 ANNEXURE-1 26 Modifications for 2 NO-2 NC type of MC31A ANNEXURE-2 27 Relay Settings Form ANNEXURE-3 28 Secondary current injection test for MC31A

Warranty 29

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1. INTRODUCTION

Over current & Earth fault Relay model MC31A is numeric type, non- directional 3 phase Over current relay. It is suitable for Over current & Earth fault protection schemes in LV, MV and HV power distribution systems. It is also suitable for applications such as providing selective protection for overhead and underground feeders, AC machines, Transformers etc.

Its Micro controller based design offers a wide range of field selectable Trip time characteristics. It also provides starter and time delayed programmable outputs for Over Current as well as Earth Fault.

The relay has a unique provision where by, it can be made suitable for operation from either a 1A CT secondary or 5A CT secondary - this CT rating can be selected in the field through menu operations.

2. GENERAL CHARACTERISTICS 2.1 Non Volatile Memory The relay has EEPROM, which retains the programmed pickup values, characteristics, Trip time settings and recorded parameters even when the auxiliary supply is switched off. 2.2 Auxiliary Power Supply Range The relay has wide range AC/DC auxiliary power supply. There are two models available. Type 1: 24V to 110V AC / DC +/- 15 % Type 2: 95V to 240V AC / DC +/- 15 %

The type of the power supply is highlighted in the wiring diagram label. Before energizing the relay, check the power supply voltage is within limits and wiring is done as per the wiring diagram.

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2.3 Relay outputs

MC31A relay has 5 relay outputs namely R1 to R5. Relays R1 to R4 can be configured for any one or more protection functions. R1 relay can be programmed to operate as self-reset type or manual reset type. R1 relay cannot be assigned to starter functions. Also, any relay assigned to starter functions can not be assigned to any other protection. The relay R5 is meant for providing alarm for internal fault conditions. It will be always energized during normal operation and de-energized when the relay is in Program mode or in the event of auxiliary control supply failure or any malfunction detected inside the relay. Note: All the output relays will de-energize when auxiliary supply is switched off even in hand reset mode. However, the output relay will regain the original status after the power up condition when supply is restored. 2.4 Starter Relay The over current and earth fault function follows the selected characteristic curve for its timing. Except R1 relay, other outputs can be programmed for instantaneous or time delayed operation of low set in over current or earth fault mode. When the protection function is programmed as instantaneous, this output is useful as an alarm relay or a blocking output to any upstream over current relay. It should not be associated to trip the breaker. The breaker trip function has to be achieved by the time delayed contact of protection function. 2.5 CT Rating

The default setting of the CT rating is 1 Amp (i.e.) P1E1 . The CT rating of the unit can be changed in the programming (ProG) menu and can be viewed in the display setting (dSEt) menu.

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The display codes for various CT ratings are:

P5E5 - Phase CT 5 A and Earth CT 5A P1E1 - Phase CT 1 A and Earth CT 1A P1E5 - Phase CT 1 A and Earth CT 5A P5E1 - Phase CT 5 A and Earth CT 1A

Note: After the modifications in the CT ratings, mark the present CT ratings on the label stuck on the right side of the unit. 2.6 Trip Time Characteristic Curves

Algorithms for time current curves Algorithms for different Time current curves are given below: t(I) = [ A ] * TMS t(I) = Trip time [ (I/Is)a – 1 ] I = Fault current Is = Setting current TMS = Time Multiplier Setting Curve Name A a Normal Inverse 1.3 Sec 0.0613 0.02 Normal Inverse 3 sec 0.1414 0.02 Very inverse 13.5 1 Extremely Inverse 80 2

2.7 Current measurements

The relay shows RMS values of three phase & Earth leakage currents at regular interval on display in scroll mode. (If the current is more than ‘9999’ A, then relay will display ‘ - - - -').

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2.8 Event Recordings

The relay records following parameters.

1. Trip data of last 5 tripping. The Trip data includes Trip cause (over current lowset, Earth Fault lowset etc.) and over current values when the fault occurred.

2. The number of Tripping due to Over current & Earth fault.

3. The RMS current value measured during Switch-ON of Feeder and highest current measured during its ON condition. These values are integrated over a period of 100 millisec.

2.9 Diagnostics The relay has a built-in watchdog facility, which monitors correct operation of program flow. During Power-ON a detailed test is conducted to check EEPROM, RAM & EPROM and other parts of the relay. Additionally, diagnostic routines are executed continuously to verify memory contents. Any time of relay’s normal operation, a test can be initiated manually by pressing the Push button. This test has the option of including or excluding trip relay operations. Under any fault condition, the relay will show the fault code “Error ” in the seven-segment display, the Error LED will glow and relay R5 will de-energize. 2.10 Signalization

The 4 seven-segment displays and 4-phase indicator LEDs show parameter settings, current values etc. The Trip window at the bottom has 4 LEDs for R, Y, B, E phases. They indicate the phase on which fault has occurred.

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These LEDs will start flashing when a fault has developed and will glow steady when the trip has occurred. The LED indication can be reset by a Reset button. However reset is not possible when fault is present. The Reset button also resets the R1 relay if it is programmed in Hand reset mode.

2.11 Reset time The relay has a unique facility – a programmable reset time for the lowset fault is provided in the relay. If fault current has appeared for a duration less than the set trip time delay, relay will hold the elapsed trip time for the duration of the programmed reset time. If the relay now senses the fault within the reset time, it will run the timer only for the remaining duration and will give the trip time command to the breaker. After issuing the trip command the relay will reset immediately irrespective of the reset time.

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3. INSTALLATION & MAINTENANCE

3.1 Preliminary checks

Relay packing consists of

1. Relay MC31A 2. Mounting clamps 3. Instruction Manual 4. Test certificate

Check the relay for any obvious damage. Please inform nearest L & T office or dealer in case of any damage. Check the Auxiliary Supply Range, Current Setting Range and Rated Current for which the unit has been configured. This is indicated on a label fixed to one side of the relay, which also shows external wiring details. Ensure that these specifications are as per your order.

Remove the protective cover from the terminal block by removing two screws. Connect suitable auxiliary supply between terminal 25 and 26. Switch ON the supply, the display and LEDs all will blink once and the display will show model number (31A) and Software version (u _.__) of the relay . After this the relay will enter into current measurement mode.

This completes the preliminary check. Disconnect the auxiliary supply and fix the protective covers on front panel and terminal block.

3.2 Mounting and Wiring:

Relay MC31A is designed for flush mounting on the panel. Refer Fig.3 for panel cutout dimensions and space required behind the panel. Insert the relay through the panel cutout and hold it firmly against the panel. Fix the mounting clamps on top & bottom side of the relay. Tighten the screws on the mounting bracket.

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Wire the relay terminals as shown in the wiring diagram (Refer Fig.2). Relay terminals are suitable for 2.5 sq mm. lugs. Fix the protective cover back on the terminal block with the help of two screws after completing the wiring.

NOTE: 1. ENSURE PROPER EARTH CONNECTION TO THE

RELAY 2. IT IS RECOMMEDED TO REMOVE THE RELAY

FROM THE PANEL DURING TRANSPORTATION.

3.3 Testing

A detailed testing of the relay can be initiated manually by running the 'TEST' menu. The testing can be done in two ways as follows. a) The "diSP" test, which does not trip the output relays. b) The "rly" test, which also trips all the relay outputs.

This test will not trip output relays when current input is sensed.

In the event of a relay failure detected during testing, the fault code will be displayed and "Error" LED will light up. The internal fault relay R5 will de-energize. 3.4 Handling Precautions In case of relay malfunction, the electronic module alone can be removed and replaced without removing the complete relay assembly with its housing from the panel. Care has to be exercised while handling the modules. The electronic components can be damaged by electrostatic discharge while handling the module. Hence care has to be taken while handling the cards as mentioned in the following page :

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a) Before removing the module ensure that you are at the same electrostatic potential as the equipment by touching the same.

b) Handle the module by its front-plate, frame, or edges of

the printed circuit board. Avoid touching the electronic components, printed circuits and connectors.

c) Do not pass the module to any person without first

ensuring that both of you are at the same potential. Shaking hands achieves equipotential.

d) Place the module on an antistatic surface, on a

conducting surface, which is at the same potential as yourself.

e) Store or transport the module in a conductive bag. 3.5 Fault Detection & Repair Internal settings and components in the relay should not be altered. For repair please contact nearest L&T sales office. 3.6 Instructions for Draw-out & Plug-in

Refer to the following diagram for relay Draw-out & Plug-in. The relay has four locking screws. These are normally in “locked position” (i.e) the slots in the screws will be vertical.

Draw-out operation:

Rotate the four locking screws by 90 Degrees. Now the screws will be in unlocked position, that is, the slots in the screws will be in horizontal position as shown in the diagram.

Hold the label handle by the fingers and pull out the module.

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The relay has CT shorting facility and hence the CT secondary will be automatically in shorted condition when the module is plugged out.

Plug-in operation:

First ensure the four locking screws are unlocked, by verifying the screwdriver mark is in horizontal position.

Position the module such that it gets engaged to the card guides in the housing. Push the module into the connector. Push all four screws and rotate by 90 degrees. They will get locked to the housing.

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! WARNING While plugging the module, If any of the Locking screws are in locked position (i.e. the screwdriver mark in the screw is vertical), the module can not be plugged fully. In such a case, The CT shorting may not have opened. To avoid this problem, ensure the screws are in unlocked position while pushing the module.

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4.1 Push-button and Display operation

Four Push-buttons marked as “Select”, “=”, “>”, “ Enter”, and a four digit seven segment LED display mounted in the front panel allow the user to program settings and read the recorded data. The different commands selected by the keys and data values are displayed in the seven segment LED display.

The Reset key is used to reset the Trip flag LED indication. 4.2 Menu operations:

The menu is arranged in a tree structure. First, main menu is to be selected, followed by sub-menus.

After Power-on checks the relay will be continuously displaying the 3phase current & Earth current values in a scrolling fashion. To enter into menu, press the “Select” button. This will select main menu. The choices in main will appear one after the other for each “=” or “>” button pressings. To select a choice, the “Enter” button has to be pressed. After this relay will display the chosen sub menu. The sub menu choices can be selected again, by operating either “=” or “>” buttons. The “Select” key also serves as a deselect key for a selected menu. Thus, from any sub-menu, to exit to scrolling current value display, the select key has to be pressed till all the menus get deselected. The menu structure is explained more in detail in following pages :

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-12- The main menu is classified into 5 categories as given below: Choices in Main menu when “=” key is operated are : Menu Choice Description

1. d.trP. Display Trip values (Cause & Trip current levels) 2. d.cur. Display maximum current values recorded. 3. d.Set. Display relay setting values 4. ProG Program the relay setting values 5. tESt Relay testing mode.

4.3 Recording of Tripping

The relay records tripping causes (Over current / Earth fault) and values of currents when trip occurred. Last 5 trip recordings are stored at any time. It also records the number of tripping due to over current and Earth fault in the feeder.

The tripping recordings is selected in the menu for “d.trP” (Display Trip Values):

L.tr.C Last Trip count values showing number of trip in Over Current and Earth Fault (Arranged as type of fault, data,.....)

L.5.tr. Last 5 Trip- data values

(Arranged as Trip number and cause of fault, R, Y, B & E current values)

In these sub menus, data is viewed by “=” key operation, the recorded data will appear sequentially with every “=” key operation. Note: In last 5 trip, trip no.1 represents latest trip followed by cause. Cause notations are OC. = Over Current lowset EF. = Earth Fault lowset (i.e.) 1.OC should be read as Latest trip is due to Over Current.

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4.4 Recording of current Values

Recording of Maximum and Starting Current values:

The relay records the current values of the three phase and Earth currents during Switch-on of the feeder. Every new Switch-on value will overwrite on the old values. This current value is an integrated RMS value of first five current cycles. The highest current values in a 5 cycle-integration period is displayed. In addition to displaying this switch on value, the relay records highest current value occurred during the normal ON period of the feeder. These current values will be overwritten only when a higher current value is measured. A switch-OFF and switch-ON of the relay will not erase this value.

The recordings of Maximum and Starting current value is selected in the menu for “d.cur” ( Display Maximum current values).

P.cur (Running max. Current) R; Y; B; E Current Values) S.cur (Starting maximum current) R; Y; B; E Current Values) 4.5 Display of settings Any time when the relay is in operation, the programmed values of parameter settings and relay configurations can be viewed. This menu choice is divided into four categories.

a) Parameter Settings b) Relay Configuration c) CT Rating d) Erase the Recorded Values

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The main selection is in “d. Set” ( Display of setting values). Sub-menu selections in the menu for “d. Set.” are : a) Parameter Setting: P.Set Parameter settings OC. Over current Pickup setting. OC.Ch. Over current characteristic setting OC.tS. Over current Time multiplier setting EF. Earth fault Pickup setting EF.Ch. Earth fault characteristic setting EF.tS. Earth fault Time multiplier setting t.rS t Reset time Ph.Ct CT ratio for Phase CTs. EF.Ct CT ratio for Earth fault CT. b)Display of relay configuration rly Relay configurations OC.St. Instantaneous over current Trip output OC. Time delayed over current Trip output EF.St. Instantaneous Earth fault Trip output EF. Time delayed Earth fault Trip output 1.rES Reset mode for R1 relay (Self /Hand reset) c)Display of CT Rating

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CT Internal CT Rating.

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d)Erase the Recorded Values

Note: The sequence of setting parameters can be viewed without pressing “Select” “=” or “>” buttons – this can be done just by pressing "Enter" push button in particular sub menu of setting.

4.6 Programming of the settings An example to modify pickup value of over current settings, is described below:

Step1. To enter into program mode, Press select key, followed by “=” key twice to get “ProG” menu. Now press “=” key and “>” key simultaneously for a while. The Prog/Error LED will flash indicating the relay has entered into Program mode. The display will show “P.SEt”. Step 2. Now press “Enter” key to get the display of “OC.”. Press “Enter” key once more, the display will show current pickup setting. Step 3. To modify the pickup setting, press either “=” or “>” key to get the desired pickup value. Step 4. To confirm the selected value, press “Enter” key .The display will start flashing. Press “Enter” key once more. The new value is registered in the relay as the new setting.

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Clr ( Clears the trip count value & trip recordings.) Press “���� “ & “ ����” keys together till "clr" display starts flashing and press enter.

Clr ( Clears the trip count value & trip recordings.)

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Sub-menu selections in the menu (ProG) for Programming of relay settings are:

Programming of the parameter settings P.Set. Parameter programming OC. 20; 25; 30; …200 (Over current pickup settings) OC.Ch. nI1.3 Normal Inverse 1.3 sec. Curve; nI 3 Normal Inverse 3 sec. Curve ; vI Very Inverse curve ; EI Extremely Inverse curve; d.1 Definite time 1 sec.; d.10 Definite time 10sec.; d.100 Definite time 100 sec. (Overcurrent curve selections) OC.tS. 0.1; 0.15; 0.2; ...1.6 (Time multiplier selection) EF. 5; 10; 15; 20...80 (Earth fault pickup setting) EF.Ch. nI1.3; nI 3; vI; EI; d.1;d.10; d.100 (Earth fault Curve selections) EF.tS. 0.1; 0.15; 0.2;....1.6 (Earth fault Time multiplier selection) t.rS t 0.1; 0.2 ;0.3; 0.4 ; …;10 or Dis(Reset time) Ph.Ct Primary phase CT ratio value. Range 0001 to

9999 (E.g. For CT ratio of 100/5 value to be entered is 20)

EF.Ct CBCT or primary Phase CT ratio value. Range 0001 to 9999 (“=” Key is to set number “>” Key is to move to next digit)

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Programming the relay configurations rly Relay output configuration OC.St. (Relay output for over current starter) OC. ( Trip relay for time delayed over current ) EF.St. ( Relay output for Earth fault starter ) EF. ( Trip relay for time delayed Earth fault )

(“=” key is to select or deselect relay. Here 1,2,3,4 represent R1, R2, R3, and R4. “>” key is to move to next relay )

1.rES S / H (Self or Hand reset for Relay 1)

Erase the Recorded Values

Changing the CT rating

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Clr ( Clears the trip count value & trip recordings.) Press “====” or “ >>>>” keys together till "clr" display starts flashing and press “Enter”.

CT For changing the internal CT rating of the relay, hold

“=” , “>”and Enter push buttons together till the Ct display starts blinking. Then press “Enter” button to enter the Ct rating menu . Select the required CT rating and press “Enter” two times to register the selection . A “conF” message is displayed which confirms the configuration change

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4.7 Test Sub-menu selections for the menu ( tESt ) – Relay testing diSP ( Testing without energizing output relays) rly (Testing including output relays )

If current value is sensed this menu will not energize output relays.

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5. TECHNICAL SPECIFICATIONS Three Phase Over Current and Earth Fault Relay MC31A 1) Rated current In : 1A or 5A 2) Rated frequency : 50Hz ± 2.5 Hz 3) Auxiliary power supply : 24V to 110V AC/DC ± 15% or 95V to 240V AC/DC ± 15% 4) Settings Over current (Is) : 0.2 - 2.0 times the In (in steps of 0.05 In) Earth fault (Os) : 0.05 - 0.8 times the On (in steps of 0.05 On) Time Multiplier : 0.1 to 1.6 in steps of 0.05 (Independent setting for O/C & E/F modes) 5) Operating Characteristics : Programmable using push button switches i) Time current Characteristics : (Separate characteristic can be selected for O/C & E/F modes) a. Normal inverse time (NI) 3sec b. Normal inverse time (NI) 1.3sec c. Very inverse time (VI) d. Extremely inverse time (EI) e. Definite time (DTL)

Three ranges (1sec, 10sec, 100sec) giving Trip time delay ranges from 100 msec to 160sec.

ii) Accuracy : As per Error class 5, IS : 3231 :1987 iii) Pickup Current : Same as set current iv) Reset Current : 95% - 90% of pickup current

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v) Reset time : 0.1- 10Sec in steps of 0.1Sec or Less than 50ms

6) Burden Current Transformer : Less than 0.25 VA / phase Aux. Power supply : Less than 10 VA

7) Operation indicators : Separate LED indication for : • Power ON

• Trip status (Separate for all the three phases and earth)

Blinks when input crosses setting and becomes permanently ON when relay has tripped. (Manually reset type)

• 4 LEDs (show status for display)Seven segment display • Trip status of each phase & earth fault • Measurement Readings • Setting parameter selected.

8) Output relays : 5 relay outputs • 4 Programmable relays for different fault Instantaneous as well as time delayed (Instantaneous relay is always self-reset)

• One hand/self reset programmable. • One relay to indicate error condition.

9) Contacts Configuration : 1 NO contact Contact rating : Rated voltage: 250V AC/30V DC Rated current : 5A. Rated Breaking Capacity : 2000VA/240 W (Resistive).

10) Over load capacity : 2 times rated current continuously 20 times rated current for 1sec.

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11) Insulation : 2 kV AC. RMS, 50 Hz for one minute across independent circuit as per IS 3231 : 1987.

1 kV AC RMS, 50 Hz for one minute across open contacts as per IS 3231:1987

12) Impulse Withstand : 5kV peak , 1.2/ 50 micro sec.as per IS 8686 :1977

13) High freq. disturbance : 1MHz, 1.0kV peak across input circuit and 1MHz, 2.5kV peak between independent circuits as per IS 8686 :1977.

14) Surge Immunity : As per IEC1000-4-5 Level 4 4 kV (CM), 2kV (DM) 15) Electric Fast Transient : As per IEC1000-4-4 Level 3, 2kV,5KHz

16) Ring Wave : As per IEC1000-4-12 Level 4 4kV (CM), 2kV (DM) 17) Electro Static Discharge : As per IEC1000-4-2 , 15kV

18) Immunity to voltage : As per IEC 1000-4-11 variations,dips and short interrupts

19) Immunity to Radiated : As per IEC1000-4-3 level 3 electromagnetic field 80 - 1000MHz,10V/m

20) Power frequency : IEC 1000-4-8:1000A/m magnetic field

21) Resistance to vibration : AS per IS 3231 and shocks 22) Temperature Operating Temperature : 0o C to 60o C Storage Temperature : -20o C to 70o C

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23) Case : DIN Standard , Panel mounting Front bezel : 158 x136 mm. Panel Cutout : 142 x 113 mm Depth : 204 mm. 24) Weight : Approx. 1.5 Kg.

Information required at the time of order : Aux. power supply range : Type 1: 24V to 110V AC / DC

or Type 2: 95V to 240V AC / DC

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Fig. 2

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Fig. 3

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Time - Current Characteristics( At TMS=1 )

For Trip time at TMS other than 1Trip time = ( Trip time at TMS=1 ) x TMS OR 50msec

whichever is more

Multiple of set current (Is)

A: Normal Inverse 3.0 Sec B: Normal Inverse 1.3 SecC: Very Inverse D: Extreme Inverse

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-26- ANNEXURE-1 Modification for 2NO – 2 NC type of MC31A On special request MC31A relay can be supplied where the relay will have 2 N/O + 2 N/C contacts ( instead of 4 N/O) The 2 NO-2 NC type of MC31A has only three output relays . One among the three , ( R5) is used for indicating the internal fault condition. The other two relays R1 and R3 have one NO output and one NC output. Both the relays can be set in either Hand reset mode or self-reset mode. Programming of these relays is not possible as both trip when the fault occurs (either Earth fault or Over current) . Below given modification helps to set the relays in hand or self-reset mode. Settings: Programming of the Settings:

Display Setting: Display of relay configuration:

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rly : Relay output configuration RES :S/H ( self or hand reset of Relay 1 and relay 3)

Rly : Relay configuration rES :Reset mode for R1 & R3 relay( Self/ hand reset)

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ANNEXURE-2 MC31A RELAY SETTING FORM DATE

RELAY NUMBER

PARAMETER SETTINGS

DEFAULT SETTING ACTUAL SETTING SETTINGS VALUE UNIT SETTINGS VALUE UNIT

OC. 100 % OC. %

OC.Ch. nI 1.3 --- OC.Ch. --- OC.tS. 1.0 Multip

les OC.tS. multipl

es

EF. 20 % EF. % EF.Ch. nI 1.3 --- EF.Ch. --- EF.tS. 1.0 Multip

les EF.tS. multipl

es t.rS t Dis t.rS t Ph.Ct. 100 CT

ratio Ph.Ct.

EF.Ct. 100 CT ratio

EF.Ct.

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RELAY CONFIGURATION

DEFAULT SETTING ACTUAL SETTING SETTINGS VALUE UNIT SETTINGS VALUE UNIT OC.St. - - - - OC.St. OC. 1 - - - OC.

EF.St. - - - - EF.St.

EF. 1 - - - EF. 1.rES. SELF 1.rES.

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ANNEXURE-3

SECONDARY CURRENT INJECTION TEST FOR MC31A:

Test Equipment: Single phase Current injection set

Connections: Connect auxiliary supply between terminal 25 and 26 (as indicated in wiring diagram). Connect terminals 1,2,3,4,5,6,7 and 8 in series so that same current will pass through all the 4 CTs.

Power on: Switch ON the supply, the display and LEDs will blink once and the display will show model number (31A), " Software version (u _.__) in the relay . After this the relay will enter into current measurement mode.

Display & earth fault trip test: Ensure the relay settings are as per Default settings given in the setting form. Pass 2A (0.4A for 1A relay) through the relay. Now the relay will start displaying the current in scrolling mode. Same time earth fault trip led will start flashing and will become permanently ON after 4.39 sec.

Over current trip test: Pass 10A(2A for 1A relay) through the relay. Now all the phase trip LEDs will start flashing indicating the presence of fault. This will continue up to 4.39 sec and later all the trip LEDs will become permanently ON and relay R1 will trip. Check the continuity between the terminals 9 and 10 to ensure tripping of R1. Remove the current and press "reset" button to reset the relay. Now LEDs will become OFF.

This completes the secondary current injection test. Disconnect auxiliary supply and other CT connections. Fix the protective covers back on front panel and terminal block.

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WARRANTY

LARSEN & TOUBRO LIMITED ( L&T) warrants that the protective Relay model MC31A 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. The foregoing 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.

Manufactured by LARSEN & TOUBRO LIMITED, KIADB INDUSTRIAL AREA, HEBBAL, HOOTAGALLY, MYSORE – 570 018. INDIA. Visit us @ www.lntmps.com www.lntebg.com www.larsentoubro.com Reach us @ mpsinfo@myw.ltindia.com Part No. 4D060082 Rev. 5