Paper 1 Flashcards
Identify three responsibilities of the inspector during a periodic inspection
A PPL = Ensure no danger to any person or livestock, and property is not damaged
B Confirm compliances with BS7671 or non-compliances which have a safety implication
C Take a view and report on the condition of the installation
State three items of information, relating to the incoming supply for an electrical installation, that must be recorded on the Generic schedule of test results
PFC
Supply polarity
Ze or Zs (db)
If the question asks for TWO examples Ans; PFC & Polarity
State the three general requirements against which installed equipment must be confirmed when carrying out a periodic inspection, as stated in BS7671
See regulation 611.2
To an appropriate standard (BS or other) or comply with section 511
Correctly selected or erected
Not visibly damaged or defective
List three non-compliances that may be identified during the inspection process using the sense of touch
Any three (different) suitable answers that use the sense of touch. Must identify the non compliance. Equipment not secure/loose connections/hot cables or equipment/broken switches. “temperature” or “Hot” not acceptable.
A test of continuity of protective conductors is required as part of Periodic inspection. State;
A, what must be confirmed when testing a radial socket outlet circuit
B, how the recorded measured value is to be confirmed as satisfactory
C, one factor that may affect the measured values obtained
a Each socket-outlet is earthed or continuity of cpc
b By comparison with adjusted Zs values given in BS7671 after deducting the external earth fault loop impedance
c Temperature is the best answer, other possible reasons include length or csa of conductor, parallel paths or loose connections
A test is carried out to obtain an R1 + R2 value at the furthest point of a two-way lighting circuit. Explain why it is necessary to operate the two way switching during this test.
Switching will include all parts of the circuit in the test, so if one strapper has a higher resistance this will be included
A test for continuity of ring final circuit conductors is to be carried out on a circuit containing no spurs. State;
A, the expected value of R1 + R2 for the circuit if the resistance of the line, neutral and cpc loops are 0.2Ω, 0.2Ω and 0.33Ω respectively.
B, the effect on the circuit R1 + R2 value if a non fused spur supplying a socket outlet was added to the circuit.
a r1 + r2 / 4 = R1+R2 0.2 + 0.33 / 4 = 0.133 Ω
(NB. Wrong answer but correct formula award 1 mark)
b R1 + R2 would Increase
During a periodic inspection, an insulation resistance test is to be carried out on a securely isolated three phase motor circuit, state;
A, the two tests to be carried out in order to complete the generic schedule of test results in BS7671
B, how the cable between the motor starter and the motor may be included in the tests in A
A1 Between live conductors
A2 Between live conductors connected together and earth (Live/cpc NOT ACCEPTABLE)
B Disconnect LIVE conductors from motor terminals and test back towards motor starter
(Note; Earth/cpc must not be disconnected)
An insulation resistance test is to be carried out to confirm electrical separation of one circuit from another circuit contained in the same conduit. State the;
A, test connections required to confirm electrical separation
B, minimum acceptable value of insulation resistance
In the past GN3 referred to electrical separation in the context of SELV and PELV only, this has now been expanded and is detailed in 2.7.9 Table 2.6
The first two tests have not changed;
A1 test between primary winding conductors connected together and secondary winding conductors connected together
A2 test between earth and secondary winding conductors connected together
New A3 where the secondary circuit has exposed conductive parts, a test should be conducted between this and any other exposed conductive parts or earth
B 1.0 MΩ (according to the same GN3 table 2.6 the test voltage is 500v dc)
State three methods of providing protection against electric shock for a 16A socket outlet circuit installed on a construction site
Any 3
Reduced low voltage (110 V centre tapped to earth)
Additional protection by RCD of 30mA or less and maximum disconnection time of 40ms when tested at 5 times it rated value (tripping current)
Electrical separation for one item of equipment or one transformer coil
SELV
PELV
State the IP codes for enclosures that provide protection against a;
A, 12.5mm diameter sphere
B, British standard TEST FINGER only
C, 1mm wire
a IP2X (the degree of protection prevents access by BS finger or other item of same size) b IPXXB (the BS finger tester can enter the enclosure but not touch live parts) c IP4X or IPXXD
State the test carried out to confirm that;
A, the outer screw contact of an Edison screw type lamp holder is connected to the neutral conductor
B, a lighting circuit protective device will disconnect within 0.4s in the event of an earth fault
C, a fuse protecting an electrical installation will operate in the event of a short circuit fault
a Polarity test
b Earth loop impedance test
c PSCC test
A test is to be carried out on an earth electrode, using an earth electrode resistance tester. State;
A, why it is necessary to take readings with the centre electrode in three different positions
B, How to determine the electrode resistance if the three readings in A, above are similar in value
C, another type of test instrument that may be used to carry out this test when the electrode being tested forms part of a TT system and is protected by an RCD
a to get a reliable result or to make sure that electrode resistance areas do not overlap
b calculate the average, BY ADDING ALL THREE AND DIVINDING THE RESULT BY 3
c earth fault loop impedance tester /meter
State, for each of the following, the type of system used for public supplies that has an earth return path, external to the installation consisting of;
A, a PEN conductor
B, the general mass of earth
C, separate neutral and protective conductors
a TN-C-S (Not TN-C)
b TT
c TN-S
An earth fault loop impedance test is to be carried out on a healthy ring final circuit consisting of nine socket outlets connected directly in the ring, state the;
A, instrument to be used
B, pattern of test results when carrying out the test at each socket outlet around the ring.
C, value to be recorded on the Generic schedule of test results
a Earth fault loop impedance tester.
b Values start lower, get higher then go lower again
c Highest.
