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[bobby101]

The 2391 practical assessment

Before you start!!!

1. Ask for previous test results

Functional test

1. test 1 way light switch
2. test 2 way light switch
3. test dimmer light switch
4. test 3 phase socket with phase rotation tester (indicator lamp type or rotating disc type)
5. confirm operation of circuit breakers and main isolators

Earth fault loop impedance

1. test all sockets at single phase board and three phase board confirm polarity and function of sockets

RCD testing

1. draw a table to record results
2. make sure to test on both sides of negative and positive sides of supply
3. test via one socket at the three phase board and the other at the single phase board
4. record the highest result for both the 1x and 5x

Open covers to three phase board
Prospective fault current

1. check condition of instrument
2. isolate the installation
3. using a three lead tester set instrument to 20 ka, PSC
4. apply probes to incoming neutral conductors the earth lead also connect to the neutral conductor, then safe working practice safer to connect to the incoming L1 last
5. take note of the result
6. apply probes to incoming neutral conductors the earth lead also connect to the neutral conductor, then L2
7. take note of the result
8. apply probes to incoming neutral conductors the earth lead also connect to the neutral conductor, then L3
9. take note of the result
10. take note of highest result
11. for prospective fault current take highest reading then multiply it by 2
12. check the rating on protective devices for breaking capacity

Open cover to single phase board

1. (having already checked the instrument no need to recheck it)
2. using a three lead instrument connect to incoming neutral the earth lead to the neutral then connect to incoming line supply conductor
3. prospective earth fault current as above but the earth lead connects to the main earth terminal
4. record result the highest of the two results that is your PFC

 

[bobby101]

Ze testing

1. A Ze reading must be taken at the origin of the installation the three phase installation
2. Check condition of instrument (only necessary if different instrument to above test)
3. Set instrument to 20 ohms, loop
4. Disconnect main earthing conductor
5. Apply test to disconnected earthing conductor and incoming line conductor L1, then redo the test on L2, then on L3
6. Test and record the highest result on both schedules of test results and PIR

Zs results will only be required by calculation Zs=Ze(R1+R2)

Polarity

Check polarity of three phase board

1. Check test lamp via proving unit prior to polarity test
2. Ten test sequence
3. (L1 –E) 230 v
4. ( L2 –E)230 v
5. (L3 – E)230v
6. (L1 - N)230v
7. (L2 – N)230v
8. (L3 – N)230v
9. (N-E)0v
10. (L1 - L2)400v
11. (L1 –L3)400v
12. (L2 - L3)400V

Check polarity at single phase board

1. Re-check test lamp
2. Test at the incoming terminals LINE TO NEUTRAL, NEUTRAL TO EARTH, LINE TO EARTH
3. TICK BOXES CONFIRMATION OF POLARITY

Before you isolate the installation ask permission from tutor small thing but people have failed for not doing so.
Time to isolate and lock off

1. Isolate installation
2. Lock off
3. Post warning notices
4. Test, testlamp
5. Prove dead
6. Re-test test lamp

Visual the whole installation take time to do it manually trace all circuits i cannot tell you what faults there will be you will have to find them yourself.... eek

 

[bobby101]

Insulation resistance
Single phase board

1. Select insulation resistance tester, check condition of instrument
2. Fit temp link to line busbar(s) and neutral busbar(s)
3. Ensure all circuit breakers are on
4. Apply test of 500v d.c. to line and earth this tests the whole installation
5. Operate the two way lighting circuit to bring the strappers into test
6. Record the result
7. Disconnect temp link
8. Isolate the RCD
9. Isolate dimmer circuit breaker (record this as a limitation)
10. apply probes to line and neutral busbars
11. test and record the result

insulation resistance
three phase

1. ensure all circuit breakers are on
2. disconnect the incoming neutral or link at the neutral busbar (only if a three phase isolator)
3. fit temp link to the three line busbars and neutral
4. apply test between the neutral and main earth terminal
5. disconnect the link from the neutral
6. apply test to neutral and line busbars (connecting the probe to the disconnected lead once done leave it there for the duration of the test)
7. disconnect the temp lead from the L1 busbar
8. apply probe to L1 busbar and test
9. disconnect the temp lead from the L2 busbar
10. apply probe to L2 busbar and test
11. ensure you have noted all results
12. go to the three phase socket
13. apply probes and do six separate tests all lines to earth then all lines
14. reconnect the incoming neutral or link at the main neutral busbar

continuity of ring final circuit conductors

1. select a low resistance ohmmeter (check condition of meter, leads, probes, tips, calibration, battery,
2. null or zero instrument)
3. draw a table to record the results
4. disconnect the ring circuit
5. test end to end resistances
6. record this on test schedule
7. cross connect line to neutral and neutral to line
8. take a measurement at each socket between the line and neutral
9. record this result on the table
10. cross connect the line to cpc and the cpc to the line
11. take a measurement between the line and the cpc
12. record the result
13. confirm results by calculation
14. for step 2 L+N/4
15. for step 3 L+CPC/4

 

[bobby101]

continuity of protective conductors including main and supplementary bonding

1. select a low resistance ohmmeter
2. on single phase board connect the lead to the MET then at each appropriate point test for continuity for the circuit protective conductor
3. on the three phase board the same as above
4. on the three phase board, disconnect the main protective bonding conductor apply leads to disconnected end the apply other lead to the MET test and confirm below 0.05 ohms then reconnect
5. to confirm R1+R2
6. connect temp link to the line bus bar(s) and the MET
7. on the single phase board confirm R1+R2 on all light points at the extremity of the circuit between line and earth
8. remember to bring two way light switches into test
9. record the highest reading in test schedule
10. in the three phase board fit temp link to all lines and the MET
11. confirm R1+R2 at the fused connection unit between line an earth record the result
12. for the three phase socket confirm R1+R2 by applying test leads to the three phase socket end connect meter to the L1 to cpc terminal then obtain result by manually operating the contactor
13. record the result

Remove all temp links and replace all busbar covers and panels

Job done .....not yet

Apply R1+R2 readings to Ze result for Zs reading

Confirm results with rule of thumb and GN3

Confirm R1+R2 readings with calculation

R1+R2=mΩ/M X (LENGTH OF CIRCUIT) X ( FOR FULL OPERATING TEMPREATURE A FACTOR OF 1.2)
1000

JOB DONE........