Re-take - Useful Information for 2394 :

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Direct measurement of ( Zs )
Q) . What is direct measurement ? A) . Direct-measurement ofEarth-fault-loop-impedance is achieved by use of an Earth-loop-impedance-tester.
This Instrument operates from the ( Main-supply ) making ita Live-Test .

- Instrument is fitted with a standard-13A plug.for connecting to the Installation directly through a normal-socket-outlet .

 

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Thisbring home how Important it is to Test.

Zs. ( Accessory ) Socket-outlet(s) perform the test on the Outlet which is furthest fromthe Origin of the circuit .
Not-known !! . Test all . Socket-outlets inthe circuit & record thehighest-value .

 

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State Three -documents on which the value of prospective fault current should be recorded .- at this point . look in page 391 . 397 .

( EIC ) - p.391 . Nature of Supply Parameters. Prospective fault current ( Ipf ) . “ 1.17 - kA “
Note - (2) . by enquiry or . by Measurement .

( EICR ) p.396 . Nature of Supply Parameters .Prospective fault current ( Ipf ) .
Note - (2) . by enquiry or . by Measurement .

GN-3 : p.57 .
Recording the Prospective fault Current . ( Ipf)
Both the ( EIC ) & the ( EICR ) contains a boxheaded . Nature of Supply Parameters , which requires the ( PFC ) at the origin to be recorded
This value to be recorded is the greater of etherthe . Short-circuit current ( Between live conductor ) or the Earth-faultcurrent ( between line conductor(s)& the main-earthing-terminal )

If it isconsidered necessary to record values at other relevant points , the can berecorded on the . Schedule of Test Results
Where . the protective-devices used at the originhave the necessary rated breaking capacity . & devices with similarbreaking capacity are used throughout the installation . it can be assumed thatthe Regulations are satisfied in this respect for all distribution boards .

 

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Two-methods for measuring RCDs .

BS-EN-61557-6 . fitted with a ( standard-13A plug-top) by plugging the instrument into asuitable-socket-outlet . protected by the RCD under test.
(Appliances should be disconnected prior to Testing )

BS-EN-61557-6 . Tests are made on the ( Load-side ) of the RCDbetween the Line-conductor of the protected-circuit & the associated ( CPC) Circuit-protective-conductor

RCD-test-instrument(s)require a few . milliamperes to operate . this is obtained from the Line &Neutral of the circuit under-test .

 

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Verificationof Test-results . 2394 :

Scheduleof Test-results : is a ( Written-record ) of the results obtained when carrying out theTests required by . Part-6 of BS-7671:2011:

 

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Blastfrom the Past . still out there . Yeah

Measurementof ( Ze ) Three-phase .

Older-method: ( Fuses )Still out there .
Fuse(s)must be .( removed ) to disconnect theInstallation for this test .
Live-test . Red .Yellow . Blue . ( Old-colourswill be still in Use )

Three-probes
1). Probes on disconnected - Earthing-conductor
2). Probes on Neutral .
3). Probe on Line . Red . Yellow . Blue .
Red- 0.25Ω .
Yellow- 0.26Ω .
Blue- 0.25Ω .

 

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Useful junk

Determine of 3phase - fault-current .

Highest . single-phase value measured . = 2.28kA .( 2.28 x √ 3 = 3.95kA )
An . approximation can be done as ( 2 x ) the reading . i.e. ( 2 x 2.28 =4.56kA )

Minimum breaking capacity for protectivedevices kA

 

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( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) are the effective-résistances . to thefurthest-point
( 1.67 - relates to the ratio of résistance of . ( 2.5mm[SUP]2[/SUP] / 1.5mm[SUP]2 [/SUP] ) it won’twork for ( Other-sizes ) Ring-final-circuit Only .

( Zs ) Confirms that a (Satisfactorily-low-fault-path-exists ) to activate the . relevantprotective-devices .

 

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UsefulJunk .

Nuisance-Tripping.
Certain-appliancessuch as Freezers tend to have . bynature of there construction & use . some leakage-currents to earth .

 

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433.1.103. - Ring-final-circuit(s) p.81.
MinimumC.S.A. of PVC-cables . 2.5mm[SUP]2[/SUP]
MinimumC.S.A. of ( MI ) cables . 1.5mm[SUP]2[/SUP]
Minimum-current-carrying-capacityof . Line & Neutral-conductor(s) - ( Iz) 20A - device . 433.1.1
Theload-current should not-exceed what for . long-periods . Current-carrying-capacity of the cable ( Iz ) of the cable .
British-standardsof . accessories to be . BS-1363 .
Overcurrent-device to be rated at . 30A or 32A . protective-device .

 

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Residual-current - Making me . ( dual-current )

TheRCD is designed to trip out when the difference between the . Line-current andthe Neutral-current ( So this is called the . residual-current) reaches the tripping-value . ( or rating ) of the device .
- Sensitivity: IΔn

RCD- Sensitivity is expressed as the rated-residual-operating-current ( IΔn ) .

TheTerm . RCD . is a generic-term applied . which open automatically in response toa . residual-current . equal to or greater than the RCDs - rated-residual-operating-current ( IΔn )

 

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RCDsfall into two-categories in term of the time taken to respond . BS-EN -

(G ) General-type . These RCDs have no specified-minimum-response-time . but have specified . Maximum-response-times.
IΔn ≤ 300mS
5x IΔn ≤ 40mS .

(S ) Type : Known as . delayed-types . specified . Minimum and Maximum-response-times .
IΔn ≤ 130- 500mS
5x IΔn ≤ 150mS

 

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RCDmaximum ( Zs- Ω ) or ( R[SUP]A[/SUP] - Ω )values .
IΔn- ( A ) maximum-touch-voltage - ( 50V )

30mA ) 0.03A - 1667Ω .
100mA ) . 0.1A - 500Ω .
300mA ) . 0.3A - 167Ω .
500mA ) . 0.5A - 100Ω .

- R[SUP]A [/SUP]≤ 50V ÷ 0.03A = 1667Ω . IΔn - 30mA
- R[SUP]A [/SUP]≤ 50V ÷ 0.3A = 167Ω . IΔn - 300mA

 

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Test-procedure: your reason .
Theobject of continuity-testing . is to measure only the résistance of the partsof the wiring-system under test . T&E .

Whatis . Earth-fault-loop-impedance .

The path followed by . fault-current as a result of alow-impedance fault occurring between the . Line-conductor and Earth . & Earth-fault-loop . Fault-current is driven round the loop by thesupply-voltage . the amount of currentdepending on the voltage of the supply and on the impedance of the loop . The higher the impedance . the lower will be thefault-current . and the longer it will take for the circuit-protective-device operate and interrupt the fault . Loop-impedance must be low . to ensure that circuit-breakers will operatequickly enough in the event of a fault . The actual maximum-value depending on the . characteristics of the . circuit-breaker concerned . 2394: Testing of - Circuit(s) must be tested to make sure that the actual . loop-impedance does notexceed that specified for the protective-device ( Circuit-loop-impedance )

 

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Whytwo -RCDs . split-load .2394 :

The circuits need to be divided evenly between two-RCDs to ensure some . lighting & power remainsif one operates .
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RCD- ( G ) general-use . for Instantaneous