Complete the following questions regarding electrical test instruments and test sequence:

Transcription

1 SPARKS MAGAZINE SUMMER (MAY) ISSUE ANSWER SHEET Priniples n prties for testing eletro-tehnil systems: (Covering Unit 307 Unerstn priniples, prties n legisltion for the inspetion, testing ommissioning n ertifition of eletro-tehnil systems n equipment in uilings, strutures n the environment (Level 3 NVQ Diplom in Instlling Eletro-Tehnil Systems n Equipment / 91 n the EAL equivlent) Test instruments: Complete the following questions regring eletril test instruments n test sequene: 1) List the instruments whih, uring n eletril ommissioning test on n instlltion, gve the following reings. ) 20MΩ ) 8kA ) 22mS ) Insultion resistne ohmmeter ) Prospetive short iruit urrent tester ) RCD tester 2) Stte THREE sfety heks to e rrie out on n erth fult loop impene tester n les prior to onuting test on lighting iruit. Test proes shoul hve finger gurs Test proe metl tips shoul not exee 4mm ut preferly 2mm Test les shoul e fuse 3) Stte the test voltges require to test insultion resistne on iruits operting t ) 25 V ) 200 V ) 600V ) 250 V SELV iruit ) 500 V Low voltge iruit ) 1000 V Low voltge iruit 4) With referene to insultion resistne testing, stte the tulte test voltges to e pplie n the minimum tulte eptle vlue of insultion resistne for EACH of the following iruits: ) SELV ) LV iruit up to 500V ) LV iruit over 500V ) 250 V.. 0.5MΩ ) 500V.. 1.0MΩ ) 1000V.. 1.0MΩ

2 5) List in the orret sequene, the first THREE tests tht shoul e performe uring n initil verifition on new omesti instlltion. Continuity of protetive onutors inluing min n supplementry oning Continuity of ring finl iruit onutors Insultion resistne 6) The test for the ontinuity of p in ril iruit feeing one soket-outlet uses temporry link n low reing ohmmeter. Stte: ) where the temporry link is onnete e) where the low reing ohmmeter is onnete f) wht the meter reing tully represents ) etween line n iruit protetive (erth) onutor t the onsumers ontrol unit ) etween line n erth t the soket outlet ) the vlue mesure is (R1 + R2) for the iruit 7) List THREE preutions to e tken efore onuting n insultion resistne test on n instlltion. i) hek for eletroni equipment ii) hek for neon lmps, pitors et iii) ll swithes lose n essories or equipment remove Alterntively iv) no ngers to persons or livestok y onuting the test 8) Before strting perioi inspetion n test, stte ) Wht must e gree with the ustomer or lient ) Who nees to gree this with the lient ) Where this greement must e reore ) the extent of the inspetion n test ) the inspetor/test engineer ) the Eletril Instlltion Conition Report (EICR)

3 9) Stte the min reson for onuting perioi inspetion n testing on n eletril instlltion. BS7671: A1 2011; Regultion Perioi inspetion n testing of every eletril instlltion shll e rrie out in orer to etermine, so fr s is resonly prtile, whether the instlltion is in stisftory onition for ontinue servie 10) Stte the mximum re-inspetion n test intervls for the following lotions: i. Crvns ii. Crvn prks iii. Constrution sites i. 3 yers ii. 1 yer iii. 3 months

4 Eletril supply systems: (Covering Outome 3 of Unit 304 Unerstn priniples for seleting les n iruit protetive evies (Level 3 NVQ Diplom in Instlling Eletro-Tehnil Systems n Equipment / 91) Cle seletion: BS7671: A1 2011, (Setion 132 Design) sttes tht iruits must e esigne n tht esign t shoul e me reily ville. Before le n e selete the following steps must e tken: Mke n Assessment of Generl Chrteristis for the instlltion. (Prt 3) Deie on the metho of le instlltion, (Prt 5) Ientify the type of le n protetive mesures for shok n over-urrent, (Prt 4). Stges of le seletion: The following six - step proeure for lulting the urrent - rrying - pity n voltge - rop for les n e use to etermine the ross-setionl-re of le/s for istriution n finl iruits, (Appenix 4): 1) Determine the esign Current (I) 2) Selet rting of suitle protetive evie (In) (Appenix 3 or Tles 41Prt 4) 3) Ientify the rting ftors tht my e pplile to the instlltion: C mient temperture Tle 4B1 Cg grouping Tle 4C1 Ci therml insultion 0.5 or see Tle 52.2 Cf BS3036 fuse, fixe rting ftor Determine the overll rting ftor (C). C = C x Cg x Ci x Cf NOTE: In prtil situtions e seletive with the tul rting ftors, e.g. if therml ftor pplies then will the mient temperture ftor mke gret el of ifferene, if not then use only the most pproprite rting ftor. 4) Clulte the tulte urrent (It) from In / C 5) Choose le to mth (It) from Appenix 4 le tles.

5 6) Chek voltge rop oes not exee limits. (See Tle 4A) The following exmple provies oxes into whih the referene or nswer n e written. Finl iruit requirements re shown in this simple lele line igrm: 25m Amient temperture 45 C 4kW resistive heting lo Uo 230v BS3036 fuse 70ºCPVC single les in steel onuit 3 other iruits in sme onuit I 17.4A In 20A Ftor C 0.79 Cg 0.65 Clulte or referene Chosen from mnufturers t or Appenix 3 Tle Referene (BS7671) 4B1 4C1 Ci N/A Cf Appenix 4 Cle instlltion referene metho B Totl rting ftor: Current Crrying Cpity of le require: (It) C = C x Cg x Ci x Cf It = In It = 20 = 53.7A C 0.79 x 0.65 x Cle size Voltge rop Tle No. 4D1A Tle No: 4D1B Column 4 Column 3 Current rting 57 Voltge rop 4.4 mv/a/m Cle size 10mm²

6 Atul Voltge rop = mv/a/m x I x Length of iruit (L) (AVD) 1000 = 4.4 x 17.4 x 25 = 1.9 V (Cle is oky within 5% llowne)

7 Eletril supply systems: (Covering Outome 6 of Unit 305, Unerstn the prties n proeures for instlling wiring systems, ssoite equipment n enlosures, (Level 3 NVQ Diplom in Instlling Eletro-Tehnil Systems n Equipment / 91 or EAL equivlent) Cle seletion: You will nee ess to BS7671: A1 2011, for this exerise. Finl iruit requirements: 35m Uo 230v Type B RCBO Amient temperture 35 C 10kW Potters Kiln 70ºC PVC, thermo-plsti multi-ore lippe iret to surfe I In 43.5 A 50A Clulte or referene Chosen from mnufturers t or Appenix 3 Ftor C 0.94 Tle Referene (BS7671) 4B1 Cg Ci Cf N/A N/A N/A Cle instlltion referene metho B Totl rting ftor: Current Crrying Cpity of le require: (It) C = C x Cg x Ci x Cf It = In It = 50 = 53.2A Only C pplies C 0.94 Cle size Voltge rop Tle No. 4D2A Tle No: 4D2B Column 6 Column 3 Current rting 63A Voltge rop 4.4 mv/a/m Cle size 10mm²

8 Atul Voltge rop = mv/a/m x I x Length of iruit (L) (AVD) 1000 = 4.4 x 43.5 x 35 = 6.7 V (Cle is oky % llowne)

9 Sfe Isoltion power supplies: (Covering Outome 1 of Unit 307 Unerstn priniples, prties n legisltion for the inspetion, testing, ommissioning n ertifition of eletro-tehnil systems n equipment in uilings, strutures n the environment (Level 3 NVQ Diplom in Instlling Eletro-Tehnil Systems n Equipment / 91) Chek your knowlege: Regultion 14 of the Eletriity t Work Regultions 1989 lerly sttes tht no person shll e engge in ny work tivity on or so ner to ny live onutor It is therefore essentil tht sfe isoltion of the power supply or supplies e me efore ommening work on iruit, or group of iruits or on permnently onnete eletril equipment. Question 1: List the HSE reommene test equipment tht will e neee efore sfe isoltion n e rrie out? The Helth & Sfety Exeutive (HSE) Guine Note, GS38, ientifies the eletril test equipment reommene for use y eletriins. The reommention is to use purpose uilt voltge test instruments omplint with the guine given in GS38. The use of non-ontt voltge initors (voltge stiks), multi-meters n neon srewrivers, shoul not e use. To ensure the orret working of the test instrument it shoul e prove to e working on known live soure or proprietry proving unit efore n fter use. Question 2: Stte the preution / s tht nee to e onsiere efore isolting ny eletril iruit, groups of iruits or eletril equipment? The preutions to e tken efore work is rrie out on low voltge eletril equipment or iruits, is tht: The orret point of isoltion is ientifie Tht permission is grnte for the isoltion of the power supply Note: Cheks must e me tht the iruit / iruits n e isolte n tht no hrm n e one y isolting, n susequently reinstting the power supply. This proeure shoul involve tlking to the ustomer or supervisor n greeing tht isoltion n e unertken.

10 Question 3: Briefly explin the reommene proeure for isolting iruit or groups of eletril iruits. After heking tht isoltion n e me it is essentil tht the supply nnot invertently e reinstte. A plok or suitle loking evie n e use for this purpose. Cution noties will lso e require t the point(s) of isoltion. In the event tht more thn one person will e working on the isolte iruit or equipment it is visle tht eh person hs unique plok n key tht they n use to ensure seurity of the point of isoltion until ll personnel hve omplete their work. A multi-lok evie n e use into whih numer of ploks n e inserte. The si priniple of sfe isoltion is tht the point of isoltion is uner the ontrol of the person who is rrying out the work on the isolte onutors. Question 4: Ientify ll of the possile mens of isoltion for finl iruit. The mens of isoltion my e: Ciruit - reker Fuse Plug n soket, Swith isonnetor Isoltor All personnel involve in work on eletril systems n equipment must e skille (eletrilly) n, where neessry, e suitly instrute (eletrilly), on sfe systems of work. Personnel shoul e provie with written instrutions, n hve ess to, pproprite loking-off evies, wrning noties, voltge etetor n proving unit. Further informtion: Most leing genies provie step-y-step guine for rrying out sfe-isoltion. It will e helpful to explore the guine y looking t we sites. The HSE provie omprehensive informtion regring eletriity t work n the preutions tht nee to e tken when working on or ner live onutors. See Question 4: Complete the reommene sequene of sfe isoltion for single-phse supplies using rrows n sttements to whih proe is onnete first n seon et

11 To ensure tht RCD s n RCBO s o not trip when onneting n pprove - voltge tester to iruits tht my not e isolte, the following sequene of test proe onnetions is reommene. NOTE: It is goo prtie to mke proe ontt with neutrl first efore line so if the supply is not isolte orretly the one free proe is not live. Step 1 Neutrl Line Erth 1 st ontt neutrl 2 n ontt line NOTE: Proviing tht Step 1 proves e then it is ssume sfe to hek to erth without tripping RCD s or RCBO s Step 2 Neutrl Line Erth Leve proe on neutrl 3 r ontt erth Step 3 Neutrl Line Erth 4 th ontt line Leve proe on erth NOTE: If you re trining to e qulifie eletriin it is essentil tht you prtie this proeure uner the guine of n eletrilly skille person.

12 Perioi Inspetion n Testing of eletril instlltions: (Covering Unit 307 Unerstn priniples, prties n legisltion for the inspetion, testing ommissioning n ertifition of eletro-tehnil systems n equipment in uilings, strutures n the environment (Level 3 NVQ Diplom in Instlling Eletro-Tehnil Systems n Equipment / 91 n the EAL equivlent) Prtie Multiple-hoie questions: 1 Whih one of the following is not sttutory oument? Eletriity t Work Regultions 1989 Builing Regultions Eletriity, Sfety, Qulity n Continuity Regultions IET Guine Note 3 X 2 When prouing speifition, vie shoul e otine from whih one of the following? Eletriity supply ompny Min ontrtor Instlltion owner / user X Billing uthority 3 Preise etils regring eletril equipment to e instlle must e otine from? The equipment mnufturer X The lient Min ontrtor Eletriity supplier 4 Guine regring eletril test equipment for use y eletriins is foun in whih of the following ouments? HS (G) 141 HSE Guine EAWR 1989 HSE GN GS 38 X 5 In n isolte system, eletri shok risk my rise from prts of the instlltion exept from? Resistive los X Solr photovolti pnels Voltges on erthe metlwork uring testing Cpitive los

13 6 The responsiilities of n inspetor re eh of the following exept? No nger ours to persons, livestok n property uring testing Compring the test results with esign riteri Consier the onition of the instlltion n vise oringly Issue prohiition noties X 7 Confirmtion tht n instlltion omplies with the originl esign riteri is otine y? Inspetion Inspetion & testing Initil verifition X Comprison with previous test results 8 When inspeting n instlltion for the first time the purpose is to verify eh of the following exept? No prt of the instlltion is mge Test results omply with esign speifition X Prts of the fixe instlltion re orretly selete n erete Instlle eletril equipment is of the orret type 9 Mximum emn, numer of live onutors n type of erthing is informtion require y? The person orering the work The Builing Control Offier The eletril ontrtor The person rrying out the inspetion n testing X 10 A re-inspetion & next test te for new instlltion is eie y? The lient Eletril esigner X Eletril ontrtor The owner of the instlltion

14 11 Completion of the eletril esign, onstrution n inspetion when rrie out y the sme person requires the issue of? A Minor Works Certifite Multiple signture Eletril Instlltion Certifite Sheule of test results Single signture Eletril Instlltion Certifite X 12 Inspetion n e unertken? Throughout ifferent stges of onstrution X On ompletion of the instlltion On ompletion of the onstrution If require uring ommissioning of the instlltion 13 The orret test sequene on lighting iruit is Continuity of protetive onutor / ontinuity of ring finl onutors / polrity Continuity of protetive onutor / polrity / insultion resistne Continuity of protetive onutor / insultion resistne / polrity Insultion resistne / polrity / ontinuity of protetive onutors X 14 Whih of the following is orret for Metho 1 ontinuity of protetive onutor test? R1+Ze R1+R2 X R1+Zs R2+Zs 15 A ril iruit 40m in length is wire with le hving 7.41mΩ/m t 20 C the expete le resistne when Metho 2 test is rrie out will e? 296Ω 2.964Ω 0.592Ω 0.296Ω X

15 Perioi Inspetion n Testing of eletril instlltions: (Covering Unit 307 Unerstn priniples, prties n legisltion for the inspetion, testing ommissioning n ertifition of eletro-tehnil systems n equipment in uilings, strutures n the environment (Level 3 NVQ Diplom in Instlling Eletro-Tehnil Systems n Equipment / 91 n the EAL equivlent) Tsk: omplete the following questions regring the priniples, prties n legisltion for the perioi inspetion n testing of eletril instlltions. Referene (GN) refers to the IET Guine Note 3 Inspetion & Testing ) Perioi inspetion n testing is rrie out for the sfety of persons n livestok ginst the effets of? Answer: eletri shok n urns (pge 61 GN3) 2) List five resons for rrying out perioi inspetion n testing Answer: mge / wer & ter / orrosion / exessive eletril loing / geing (Pge 61 GN3) 3) Perioi inspetion n testing my e require for speifi resons, stte four resons. Answer: to ssess ompline with BS7671 / on hnge of oupny / hnge of use of premises (pge 62 GN3) 4) Routine heks of the eletril instlltion in ommeril or inustril premises n e rrie out y whom? Answer: n eletrilly skille person or someoy who is le to reognise efets (pge 63 GN3) 5) The te for the first perioi inspetion n test is the responsiility of whom? Answer: the instlltion esigner (pge 64 GN3) 6) Stte the mximum re-inspetion n test intervls for the following lotions: Crvns; rvn prks n onstrution sites Answer: 3 yers / 1 yer / 3 months (pge 65 GN3) 7) Briefly explin how to rry-out n overview of n instlltion prior to onuting perioi inspetion n test. Answer: otin informtion from igrms n hrts n wlk roun survey of the premises (pge prgrph: 3)

16 8) Stte two importnt fts tht shoul e note uring the pre-inspetion / testing survey. Answer: ngers tht my rise uring testing / the lotion of ny equipment tht will nee sfety preutions to e tken efore testing (pge 67 GN3) 9) The perioi inspetion smple shoul onsier numer of ftors, ientify four ftors. Answer: ge of property / type n use of the instlltion / effetiveness of on-going mintenne / perio of time sine the lst inspetion n test (pge 68 GN3) 10) If smple inspetion n test revels the instlltion to e in poor onition the inspetor will nee to inrese the smple, riefly explin the tions to e tken. Answer: See pge 69 GN3 11) If n inspetor fins inequies in istriutors equipment the reommene tion is to? Answer: the person orering the work will nee to inform the istrit network uthority (DNO) (Pge 70 GN3) 12) With regrs the termintion of les t enlosures, list four heks tht n inspetor shoul mke. Answer: onnetions not uner strin / no si insultion of onutor showing outsie enlosure / live onutor onnetions equtely enlose / equtely onnete t point of entry to enlosure (Pge 73 GN3) 13) Explin how loop impene test is to e rrie out on n eletri motor. Answer: this test n only e rrie out on the supply sie of the motor strter / ontrolger. A ontinuity test n e performe etween the strter / ontrol-ger n the motor itself to onfirm the reing remins t suitle vlue. (Pge 76 GN3) 14) Briefly esrie the heks to e me on iruit-rekers uring perioi inspetion n test. Answer: See pge 78 GN ()

17 AC / DC Motors: (Covering Unit 309 Outome 8, Unerstn the operting priniples of n motors (Level 3 NVQ Diplom in Instlling Eletro-Tehnil Systems n Equipment / 91 or EAL equivlent) The following questions re ll relte to AC & DC motors: 1) Ientify the type of motor n eh of the omponents numere in the photogrph elow: Type of motor: Single phse AC pitor strt inution motor 1 - Cpitor 2 Run & Strt winings 4 - Shft 3 Lminte steel Sttor

18 2) Ientify the nme of the omponent shown elow n the type of motor it is use in: Nme of omponent: Armture Type of motor in whih it is use: AC Universl or DC mhine i.e. (Shunt / Series or Compoun motor or genertor) 3) Ientify the motor omponent shown n the mterils use in its onstrution. Aluminium rs n en rings Lminte silion steel ore Component: AC ge rotor Mterils use in the onstrution:

19 4) Ientify the motor omponent shown n the mterils use in its onstrution Lminte silion steel frme Copper winings Insulte pper Component: AC motor Sttor (3-phse Sttor) Mterils use in the onstrution: Lminte silion steel frme

20 Eletril supply systems: (Covering Outome 3 of Unit 304 Unerstn priniples for seleting les n iruit protetive evies (Level 3 NVQ Diplom in Instlling Eletro-Tehnil Systems n Equipment / 91) BS7671:2008 +A1:2011 (Answers) The following series of questions will require you to hve opy of BS7671:2008 +A1:2011Appenix 3, Time /Current Chrteristis of Overurrent Protetive Devies n RCD s Question 1: ) Wht informtion oes Appenix 3 ontin? ) How is the informtion presente? ) Who will require this informtion n when? ) Time / urrent hrteristis for rnge of protetive evies, e.g. fuses n iruit-rekers. ) By logrithmi grph n tles. ) Eletril iruit esigners / testing & ommissioning engineers Question 2: ) If the mximum erth fult loop impene for 230V iruit is 2.035Ω lulte the fult urrent tht will flow in the event of line to erth fult ourring in the iruit. ) If the iruit in () is protete y BS88-3 fuse, wht is the operting time of the fuse when the fult urrent ours? ) From the formul: Zs = Uo / I By rerrngement I = Uo / Zs Therefore I = 230 / = 113A ) From Figure 3A1 it n e foun tht the isonnetion time is 0.4 se.

21 Question 3: ) How n ifferent types of RCD e lssifie? ) Wht oes the symol I n represent in regrs to RCD s? ) Ientify the three ommon types of BS EN iruit rekers. ) For eh of the iruit rekers ientifie in () ove, stte the ifferenes etween their overurrent hrteristis. ) Non ely n S type ) Rte resiul operting urrent expresse in ma ) Type B / C n D ) Type B opertes t 5 x the urrent rting of the evie Question 4: The Time / Current hrteristi for ny iruit-reker, shows two overurrent onitions, wht re these onitions? Question 5: Type C opertes t 10 x the urrent rting of the evie Type D opertes t 20 x the urrent rting of the evie i) The urve top setion of the grph represents the therml element of the evie. ii) The stright setion represents the mgneti element of the evie. ) If 40A rte BS88-2 fuse is use to protet single phse 230V istriution iruit stte the fult urrent tht must flow to isonnet the iruit in 100 seons. ) A fult urrent of 20A flows through 5A rte BS3036 semi-enlose fuse. Determine the isonnetion time. ) From the grph Fig: 3A3() fin 100 on the vertil (Time) xes re ross to the 40A urve n then follow the vertil line ownwrs to the ottom of the grph. The reing will e pproximtely 100A ) From Fig: 3A2() follow long the se of the grph, (the prospetive urrent) to 20A, follow upwrs until you meet the 5A urve, re ross horizontlly to the left sie n re off the time: in this se pproximtely 0.7 seons

22 Initil verifition of eletril instlltions: (Covering Unit 308 Unerstn priniples, prties n legisltion for ignosing n orreting eletril fults in eletro-tehnil systems n equipment in uilings, strutures n the environment (Level 3 NVQ Diplom in Instlling Eletro-Tehnil Systems n Equipment / 91 n the EAL equivlent) Erth lmps: The following olour oe my e foun on BS951 erth oning lmps Re is for ry non-orrosive tmospheres Blue is for orrosive or humi onitions Green is for orrosive or humi onitions lrge erth onutors Cle termintions to BS951 lmps: If min protetive oning is to e rrie-out then hoie of terminting methos my e use: Cles my e run seprtely from the min erthing terminl (MET) in the Consumers Control Unit (CCU) or using single le to onnet, un roken, to eh servie lmp, see elow: Revision questions 1: ) Wht is the wrning messge printe on the lel of BS951 erth oning lmp? Sfety Eletril Connetion Do Not Remove ) Stte the purpose of protetive equipotentil oning To mintin ll extrneous onutive prts t erth potentil ) The onnetion of the min protetive oning onutor must ielly e me within 600mm of where? The inoming servie to the premises whether this is gs, wter, oil or ny other servie suh s ompresse ir in n inustril lotion et ) In the se of rnh pipework where must the min protetive oning onutor e onnete? Before ny rnh in the pipework

23 Question 2: When rrying out n initil verifition the inspetor must hek ll erth oning termintions. Look t eh of the following imges n eie whether the protetive oning instlltion hs een orretly terminte. If No stte why 1) Corret termintion: Yes No X This termintion is inorretly terminte euse the onutor strns hve een Reson: ivie so there re four strns n three strns eh sie of the terminl srew, this results in uneven lmping of the onutor 2) Corret termintion: Yes X No Reson: This is n exmple of orretly terminte lmp

24 3) Corret termintion: Yes No X Reson: This is inorret euse the protetive oning onutor is not orretly terminte t either oning lmp. The 4) Corret termintion: Yes No X Reson: This instlltion ppers to e orretly instlle with single protetive onutor use n the gs on me efore the

25 5) Corret termintion: Yes No X Reson: Inorret, lthough suitle lug is tthe the protetive oning is not ontinuous s reommene 6) Corret termintion: Yes X No Reson: Seprte protetive oning onutors n e onnete etween the min

26 Eletri Certifition: (Covering Outome 5 of Unit 307 Unerstn priniples, prties n legisltion for the inspetion, testing, ommissioning n ertifition of eletro-tehnil systems n equipment in uilings, strutures n the environment (Level 3 NVQ Diplom in Instlling Eletro-Tehnil Systems n Equipment / 91) The Minor Eletril Instlltion Works Certifite: Tsk 1: Stte the purpose of the Minor Eletril Instlltion Works Certifite Altertions n itions to existing eletril instlltions. Replement of equipment ut not istriution ors or onsumers ontrol units. The ertifite is single sie A4 pro-form on whih ll the neessry etils relting to the minor eletril instlltion work re stte. Tsk 2:Stte two persons tht nee to retin opies of the Minor Eletril Instlltion Works Certifite when work hs een omplete. A opy of the ertifite must e retine y: The ontrtor (opy) The person orering the work/s. (originl) Tsk 3:The following tsk requires you to stuy the instlltion etils n omplete opy of the tthe Minor Eletril Instlltion Works Certifite INSTALLATION DETAILS SET 1: You hve instlle fuse-onnetion unit, (fuse spur) on n existing 32A rte ring-finl iruit t ABC stores, 243 Wieome Ple, Belhester, DN0 4EX on 1 st April The originl ring iruit ws instlle five yers go n looks in goo onition s oes the rest of the eletril instlltion in the store. The supply system is TN-S n fult protetion is y ADS. The existing ring iruit is protete y 32A Type B iruit-reker to BS EN60898 n itionl protetion is provie y 30mA RCD, the ition of the fuse-onnetion unit will not ompromise the urrent rting of the existing ring-finl iruit. No previous test results re ville to ompre with the test results otine when the ition ws omplete. The new test results re ll within the expete rnge. Continuity of iruit protetive onutor n min protetive oning onutor is 0.1Ω n 0.5Ω respetively; insultion resistne etween ll onutors is +200MΩ; polrity ws onfirme; erth fult loop impene is 1.10Ω n the RCD retion time test prove stisftory with the I n t 25mS. The min wter servie is one with 10mm 2 single-shethe erth le

27 Conneting eletril mesuring instruments: (Covering Unit 309 Outome 7 Unerstn how ifferent eletril properties n ffet eletril iruits, systems n equipment. (Level 3 NVQ Diplom in Instlling Eletro-Tehnil Systems n Equipment / 91) Unerstning the type n use of vrious eletril test instruments is importnt euse inorret onnetion n seriously mge the instrument, the iruit in whih it is onnete n oul pose nger to the opertor. The following tsks relte to the mesuring or etermintion of power in single-phse.. iruits. Tsk 1: Ientify the orret nme for eh of the numere omponents shown in the iruit igrm elow: L N Answer: 1 Voltmeter 2 Ammeter 3 Wttmeter 4- Inutor (hoke) 5 Resistor or Lo Tsk 2: Stte the reson for mesuring the eletril quntities t the points shown in (1), (2) n (3), in the iruit shown ove: By otining mesurements for urrent (2), voltge (1) n power (3) in the inutive iruit the power ftor (pf) of the iruit n e lulte, the formul is: pf = W or pf = true power VA pprent power

28 Tsk 3: Clulte the power rting (W) of n inutive lo if the power ftor is 0.85, the urrent is 50A n the voltge is 230V. pf = true power pf = W therefore W = pf x V x A pprent power VA W = 0.85 x 230 x 50 W = 9775 wtts or 9.78kW (roune up) Perioi Inspetion n Testing of eletril instlltions:

29 Fult Dignosis & Retifition: Revision multiple-hoie questions 1 Whih of the following omintions is the orret sequene of events when rrying out sfe isoltion? 1 reprove test instrument 2 isolte supply n lok off 3 prove isoltion with test instrument 4 test instrument on known supply 1,3,4,2 1,4,3,2 4,2,3,1 X 1,2,3,4 2 A 12v 50W triple spot light is supplie from single 230v to 12v oule-woun trnsformer. If the originl trnsformer fils n is to e reple wht is the VA rting tht will e require? 12VA 12.5VA 50V 150VA X 3 When mesuring the ontinuity of ring finl iruit wire in 2.5mm² Twin n erth le, the resistne of the iruit protetive onutor shoul e? Lower thn the line n neutrl onutors Lower thn the line onutor only Higher thn the line n neutrl onutors X Higher thn the p

30 4 It hs een reporte tht D-O-L motor strter oes not hol on when the strt push utton is relese, the most likely use of this prolem is? No link etween the uxiliry ontt n the strt push X No link etween the strt push n the stop push No supply to the strter No supply to the motor 5 When rrying out ontinuity heks on the winings of singlephse, pitor - strt eletri motor, whih of the following is most likely to e foun? A Strt wining will hve lower resistne thn the run wining Auxiliry wining will hve lower resistne thn the min wining Strt wining will hve higher resistne thn the run wining X Run wining will hve higher resistne thn the strting pitor 6 A omesti ustomer reports tht the lning lighting iruit hs file. The lmp hs een reple ut fils to operte; whih one of the following is most likely to e the use? Ciruit reker hs operte following the filure of the first lmp The two wy swith is not wire orretly etween the swithes The intermeite swith is in the off position The seon lmp is fulty X

31 7 Whih one of the following senses is usully not require when rrying out fult fining? Hering Seeing Touhing Tsting X 8 Whih one of the following sttements is true? A neutrl onutor is onnete to the entre pin of n Eison Srew lmp-holer When viewe from the rer the line terminl of BS1363 soket outlet is on the left A lue oloure BS EN plug is use on 400V supplies A solr photovolti rry n e onnete iretly into omesti onsumer unit X 9 A omesti entrl heting system fils to operte following n Eletril Instlltion Conition Report eing unertken on the property. Wht is the most likely use of this filure? The heting system nees to e overhule The eletroni ontrol pnel hs een mge ue to insultion resistne test voltges eing pplie The power supply hs een isolte t the fuse-onnetion unit for insultion tests to e me. There is n lose iruit on the phse onutor X

32 10 A single tue, glow type strt fluoresent luminire fils to strt following the replement of the tue, whih of the following is most likely to e the use of this prolem? Choke filure Power ftor orretion pitor hs open iruite Inorret tue hs een fitte Strter filure X 11 When rrying out ommissioning test of str elt motor it is foun tht the motor strts in str ut in elt the motor immeitely goes into reverse n mkes lou soun. Wht is the use of this prolem? One phse isonnete Inorret wiring on the elt onttor X Inorret setting of the overlo evie Two phses isonnete 12 A ustomer reports tht the sitting room light immer swith hs file to im the light n tht, when the immer is operte the light ims slightly then goes out. Wht is the most likely use? Wiring filure t the light point Dimmer swith hs een mge A ompt fluoresent lmp hs een instlle X The iruit reker is the wrong type

33 13 The vlue of Ze n e otine y enquiry, lultion or mesurement. Where n the mesurement e me n wht type of instrument is require? At the min swith in the CCU / Erth loop impene tester X At the lst soket in the ring / erth loop impene tester At light point / ontinuity tester Min supply t the CCU / High reing Ohmmeter 14 Whih of the following is issue following remeil work tht oes not exten to new iruit? Instlltion Certifite Minor Eletril Instlltion Work Certifite X Permit to Work Eletril Instlltion Conition Report No Question 15 The type of instrument use to etermine the Prospetive Fult Current (PFC) of n instlltion is? Low reing Ohmmeter High reing Ohmmeter RCD tester Erth fult loop impene tester X

34 16 Dmge n e use to eletroni omponents in iruit ue to whih of the following? Uner-voltge use y voltge rop in iruit Over-voltge from trnsient X Over-urrent ue to line erth fult Frequent swithing on-off of the equipment 17 A mge le must e reple. Whih of the following ouments must e use following ompletion of the iruit? Eletril Instlltion Certifite for the iruit X Minor works ertifite for the whole instlltion Perioi inspetion report for the iruit Sheule of test results for the whole iruit 18 If the oning lmp shown h RED stripe the most suitle environmentl onitions in whih it n e use is? Dmp / wet Outsie lotions Dry insie lotions X Corrosive tmospheres

35 19 Following rewire of omesti property the person who is require to fill out the require oumenttion is? A person with high IQ A person who hs een in the eletril tre for severl yers A ompetent person X A person ting on ehlf of the property insurne ompny 20 Whih one of the following will not require speil preutions to e opte prior to inspetion n testing? Ciruits supplying IT equipment Ciruits supplying remote uilings X Intruer lrm sensors Fire opti les

36 En of Yer Revision: Eletril Siene & Priniples (Covering Unit 309: Unerstning the eletril priniples ssoite with the esign, uiling, instlltion, n mintenne of eletril equipment n systems (Level 3 NVQ Diplom in Instlling Eletro-Tehnil Systems n Equipment / 91 or EAL equivlent) Attempt the following Multiple Choie questions 1 Three resistors of 12Ω, 15Ω n 23Ω re onnete in prllel with eh other. The totl resistne will e? Higher thn 23Ω Higher thn 15Ω Lower thn 15Ω Lower thn 12Ω X 2 Two resistors eh hving resistne of 17Ω re onnete in prllel with resistor of 3.5Ω. The totl resistne is? 12Ω X 13.5Ω 20.5Ω 59.5Ω 3 The totl resistne of iruit is 126Ω. If the iruit onsists of four resistors, n one resistor is 14Ω, wht is the vlue of the remining three? 140Ω 112Ω X 100Ω 9Ω

37 4 Wht is the totl urrent flowing in iruit onsisting of three 66Ω resistors onnete in prllel with eh other n onnete to 50V.. supply? 0.25A 0.72A 0.76A 2.27A X 5 Whih one of the following shows the symol for self - inutne? H C L X M 6 The unit symol for Current is? A X C V I 7 The quntity symol for Power is represente y? A C W P X

38 8 The symol for Energy is W, wht is the unit symol? W J X P C 9 A onutor 45m long n rrying 5A is lying t 90º to mgneti fiel of 2T, wht is the fore on the onutor? 450N X 225N 150N 100N 10 Clulte the length of onutor in whih 50V is inue when it is pssing through flux ensity of 4T t rte of 3m/s 4.2m X 4.0m 3.9m 3.5m 11 Wht is the resistne of 100m of 1.5mm² opper le is if the onutor resistivity is given s 17.2µΩ/mm? 0.50 Ω 0.95 Ω 1.00 Ω 1.15 Ω X

39 12 The eletron hs wht type of eletril hrge? Negtive X Positive None Equl positive n negtive 13 Wht is the ssume urrent emn for n eletri shower rte t 9.5kW when onnete to 230V supply? 30A 38A 39.58A 41.30A X 14 If istriution iruit le is supplie t en A with 230v, n resistive los re tken from it t points B n C, if the overll voltge rop from A to C is 6v, B to C is 2.5v; the voltge t B is? 228V 226.5V X 225V 220.5V

40 15 If n eletri motor is rte t 28kW n hs n effiieny of 75%, the eletril input to the motor will e? 20.05kW 21.00kW 28.00kW 37.33kW X 16 A oule-woun trnsformer opertes on wht priniple? Self -inution Mutul inution X Impene resistne 17 A trnsformer hs rting of 600VA, if the output voltge is 12V wht is the totl urrent tht n e elivere? 5A 32A 45A 50A X

41 18 A step own trnsformer hs primry voltge of 230V n seonry voltge of 24V The turns rtion for the trnsformer is 9.6 : 1 X 6.9 : : : 1 19 The phse voltge of str onnete trnsformer is 250V. Wht is the line voltge? 400V 433V X 445V 460V 20 If the mesuring rnge of n mmeter is to e extene whih one of the following is use? Multiplier Shunt resistor X Dioe Dioe shunt

42 Unerstning Eletril Priniples: (Covering Unit 309 Outome 8 Unerstn the operting priniples n pplitions of DC n AC mhines (Level 3 NVQ Diplom in Instlling Eletro-Tehnil Systems n Equipment / 91) Eletri motors: TYPES OF MOTOR AC DC 3 PHASE 1 PHASE Shunt Split phse Series Synhronous Asynhronous Universl Repulsion Compoun Seprtely exite Woun rotor Cge Inution Single ge Doule ge Motors re often tegorise y the strting metho use, however re must e tken to e sure you unerstn the type of motor for whih the strting metho is suitle.

43 AC motor strting methos: Tsk: Ientify the motor power supplies suitle for eh of the following strting methos: Strting evie / metho Diret on Line (D-O-L) strter Str Delt strting Rotor Resistne strter Auto Trnsformer strter AC 3 phse ü ü ü ü AC 1 phse ü N/A N/A N/A Soft Strt ü ü DC N/A N/A N/A N/A N/A Fe plte strter N/A N/A ü