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HIGH VOLTAGE 6,6 KV GENERATORS INSULATION RESISTANCE TEST

PROCEDURE

IT IS EXTREMELY IMPORTANT OF FOLLOWING CORRECT PROCEDURES WHILE

WORKING WITH HIGH VOLTAGE. AN ERROR WOULD MOST PROBABLY BE FATAL

WORKING ON A HIGH VOLTAGE SWITCHBOARD. LIKE ALL THE OTHER WORKS WITH

HIGH VOLTAGE, TWO PERSONS ARE ALWAYS REQUIRED, WITH AT LEAST ONE

ELECTRICIAN WITH A HIGH VOLTAGE TRAINING COURSE.

THE INSULATION RESISTANCE TEST OF ALTERNATORS CAN BE DONE FROM HV

SWITCHBOARDS OR LOCALLY FROM GENERATOR SIDE BY REMOVING HV TERMINAL

CONNECTION COVER AT PORT SIDE OF ALTERNATORS.

WITH A VALID MEGGER TESTER, 1000 VOLTS MUST BE APPLIED AND INSULATION

READING MUST BE AT LEAST 5 Mohms IN ORDER TO SAFELY CONNECT THE

GENERATOR AS PER MAKERS INSTRUCTIONS. IT IS PREFERABLE IF 2500 VOLTS CAN BE APPLIED FROM THE MEGGER TESTER TO

THE GENERATOR AND THIS TIME AN ACCEPTABLE RESULT HAS TO BE AT LEAST 100

Mohms.

TURBINE GENERATOR

1. PRIOR TO ANY MOVEMENT THE GENERATOR TURBINE MUST BE SECURED AS IN COLD STATE. THE STEAM VALVES FOR TURBO GENERATORS AND THE AIR VALVE FOR DIESEL

GENERATOR MUST BE CLOSED AND SECURED. PRE-LUBE OIL PUMP MAY OPERATE IN

MANUAL WHILE TURNING GEAR OF GENERATOR TO BE STOPPED AND SWITCHED OFF

FROM THE LOCAL PANEL PROVIDING THAT THE VACUUM IN THE TURBINE CASING IS ZERO.

FINALLY TURN OFF SUPERVISORY PANEL OF GENERATOR.

IT IS A GOOD PRACTICE THAT A WARNING SIGN SUCH AS DO NOT OPERATE HIGH VOLTAGE WORK IN PROGRESS TO BE PLACED IN THE GENERATORS SIDE AND IN THE ECR WORK STATIONS PICTURE-1

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AVR

2. TURN OFF AVR POWER SUPPLY FOR THE CORRECT GENERATOR. THE FUSES SHOULD BE PULLED OUT OR AT LEAST BE TAGGED OUT WITH A NOTICE DO NOT OPERATE OR SIMILAR. AVR TO BE SWITCHED FROM AUTO TO OFF PICTURE-2

VOLTAGE CIRCUIT BREAKER

3. PLACE THE HANDLE TOOL AND ROTATE COUNTER-CLOCKWISE TO ROLL OUT THE ALTERNATOR BREAKER IN TEST POSITION. PICTURE-3

IMPORTANT REMARK:

TO MEASURE THE INSULATION RESISTANCE FROM HV SWITCHBOARD SIDE, ACCORDING TO

THE ABB INSTRUCTION MANUAL THE VCB MUST BE TOTALLY REMOVED BY USING THE SPECIAL

TOOL, PROVIDING THAT VCB WILL BE PULLED AT THE FULL OUT POSITION.

THE PROCEDURE OF THE WITHDRAWAL AND INSERTION MUST ALWAYS BE CARRIED OUT WITH

THE CIRCUIT BREAKER OPENED AND THE SPRING MECHANISM DISCHARGED.

THE PROCEDURE FOR THE VCB REMOVAL IS DESCRIBED IN THE ABB MANUALS. VOLUME 2 of 3,

BOOK 6 of 8, 6.6 KV SWITCHBOARD MANUAL. EM-04 VOL 2 BOOK 6 VOLUME 2 of 3, BOOK 1 of 8,

6.6 KV SWITCHBOARDS TECHNICAL DOCUMENTATION CERTIFICATES. EM-04 VOL 2 BOOK 1

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EARTH INTERLOCK

4. TO ACTIVATE THE EARTH INTERLOCK COIL PRESS ENTER ON THE REM UNTIL TO HIGHLIGHT ES THEN PRESS I. A SHORT CLICK IN THE EARTH SWITCH INTERLOCK COIL WILL BE HEARD AND WILL CHANGE TO CLOSE. PICTURE-4

GROUNDING MECHANISM

5. THE GROUNDING SWITCH MECHANISM IS NOW FREE TO BE ENGAGED. UN-LOCK WITH THE KEY AND INSERT THE HANDLE TOOL INTO THE SLOT. ROTATE CLOCKWISE 180 DEGREES. A

HEAVY CLACK SOUND IS ALWAYS COMING DUE TO THE ENGAGEMENT. DELAY TO ENGAGE

GROUNDING SWITCH MECHANISM WILL CAUSE THE ES EARTH INTERLOCK COIL TO RETURN TO OPEN STATE. ENSURE THAT ON THE REM GROUNDING INDICATION IS ON, ALSO

A WARNING ALARM WILL BE ACTIVATED IN THE IAS MONITORS E.G.No1 T G GROUNDING REMOVE HANDLE TOOL, LOCK WITH THE KEY AND KEEP IT INSIDE YOUR POCKET.

PICTURE-5

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VOLTAGE AND MEGGER TESTING

6. REMOVE HV SIDE TERMINAL CONNECTION BOX COVER OF THE GENERATOR TO BE TESTED.

AS A RULE REMEMBER THAT HIGH VOLTAGE EQUIPMENT SHOULD BE CONSIDERED ALIVE

UNTIL TO ESTABLISH VISIBLE EARTH OF THE WORK PLACE. DO A VOLTAGE TEST WITH THE

HIGH VOLTAGE TESTER, REMEMBER TO DO A FUNCTION TEST OF THE TESTER BOTH TIMES

BEFORE AND AFTER THE ACTUAL TEST

CONNECT MEGGER TESTER TERMINALS ONE ON THE SHIPS METALLIC STRUCTURE AND THE OTHER TO ONE PHASE U PICTURE-6

7. GO BACK TO MAIN SWITCHBOARD AND DO THE ABOVE STEPS REVERSELY. SELECT ES ON THE REM AND PRESS CLOSE IN ORDER TO OPEN EARTH INTERLOCK COIL. UN-LOCK WITH THE KEY AND INSERT-ROTATE HANDLE TOOL COUNTER-CLOCKWISE 180

DEGREES PLACING GROUND SWITCH BACK TO THE ORIGINAL POSITION. GENERATOR

WILL BE UN-GROUNDED AND PHASE IS READY FOR MEGGER TESTING PICTURE-7

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8. AFTER DISENGAGEMENT OF THE GROUND APPARATUS REMEMBER THAT ALL TERMINALS SHOULD BE NOW CONSIDERED ALIVE SINCE THEY ARE NO LONGER GROUNDED. KEEP A SAFE DISTANCE FROM THOSE TERMINALS AS A PRECAUTION.

TAKE MEGGER TEST READING FROM THE CONNECTED PHASE U ONLY PICTURE-8

9. REPEAT STEPS FROM [4 8] TO MEGGER TEST THE SECOND PHASE V AND SO ON.

IMPORTANT REMARKS:

STAY AWAY FROM THE SWITCHBOARD ROOM FIRST TIME CONNECTING THE BREAKER

AGAIN IN AN UNLIKELY EVENT OF FORGOTTEN TOOLS THAT WILL LAST OF MAKING A

SHORT CIRCUIT.

IF EVER NEEDED A MEGGER TEST TO BE DONE USING MORE THAN 6000 VOLTS THEN

FOLLOWING PROCEDURE MUST ALSO BE FOLLOWED.

FOR THE TURBO GENERATORS: CABLES AT TERMINALS U2, V2, W2, N2, U3, V3, W3, C6, C5, CT4,

CT5, CT6, CT7, CT8, CT9 TO BE DISCONNECTED. (DWG N-530069E1B-11). SEE DRAWING 01.

FOR THE DIESEL GENERATOR: CABLES AT TERMINALS U12, V12, W12, N12, U22, V22, W22, N22,

U13, V13, W13, U23, V23, W23, C6A, C5A, C6B, C5B, CT4, CT5, CT6, CT7, CT8, CT9, TO BE

DISCONNECTED. (DWG N-530069E2B-11) SEE DRAWING 02.

THIS IS NOT AN OFFICIAL DOCUMENT THEREFORE EVALUATE ACCORDING

TO YOUR KNOWLEDGE AND EXPERIENCE. IF IT IS NECESSARY TO TAKE MORE

PRECAUTIONS THEN DO IT.. NEVER GET CLOSE TO HIGH VOLTAGE .

CHIEF ENGINEER

GEORGE VRETAKOS

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