Iarthachú Inbhinn: Cad é & Cén Fáth Is Tábhachtach É
Cad é an Comhshúlú?
Comhshúlú táirge is nasc déantar trí ghné maitheamhail idir corp aon seicme leictreach nó pointe neodrach, mar is cuí, go dtí talamh talún níos airde. Is gné maitheamhail de chuid MS flat, CI flat, agus giota GI atá ina chuid den nasc a bhíonn ina chionn sa grid talamh.
Comhshúlú táirge bunaithe ar Stairiúil IS:3043-1987.
Ranguithe de tháirgí leictreach IS: 9409-1980
Rialacha tábhachtacha don slándú agus comhshúlú bunaithe ar rialacha IE 1956
Treoir ar tionchar na modhaint ag dul trí chothromán daonna – IS:8437-1997
Cosaint foirgnimh agus struchtúir ó scianleighe – IS:2309-1969
Talamh: An tóircheann maitheamhail den domhan, a potansal leictreach ar aon phointe atá gnáchmhaire agus glacadh mar ZERO.
Eileacán Talamh: Cúlóir nó grúpa cúlóir i dteagmháil íoghair leis an talamh agus ag tabhairt nasc leictreach go dtí an talamh.
Modhúlachas Eileacán Talamh: An modhúlachas leictreach eileacán talaimh go dtí an maolchuid talaimh.
Cúlóir Comhshúlú: Cúlóir cosanta ag nascadh an teideal comhshúlú príomha le heileacán talamh nó bealach eile comhshúlú.
Bainistiú Cothrom: Nasc leictreach a chuirtear i bhfeidhm chun go mbeidh cothromán daonnachta agus cothromán ionraic ag an gcóras cothrom le chéile.
Eiseamláir: Nasc córas AC/HV cosanta, cúlóir leanúnach talaimh agus risers.Gradáin potansail: An díoltanas potansail in aghaidh aonad faide a mhéastar i dtreo a bhfuil sé ar a uair is airde.
Voltas Teanga: An PD idir struchtúr meiteallach a bhíonn suite agus pointe ar údar talún a bhfuil siad scartha ag tréimhse sreabhadh amháin Metre.
Voltas Scéime: An PD idir dhá pointe ar údar talún a bhfuil siad scartha ag tréimhse scéime (scéim) a mharcar mar Metre.
Grid Talamh: Córas eileacán comhshúlú a chomhshúladh trí chuidicheana ceangailta suite sa talamh chun a chur go ginearálta talaimh ó tháirgí leictreach agus struchtúir meiteallacha.
Mat Talamh: Córas comhshúlú bunaithe ar ghrid de chuidicheana horizontálta suite – Seirbhís do chur isteach modhaint fhealmhais go dtí an talamh agus freisin mar chóras nasc cothrom le chéile.
Cén Fáth go bhfuil an Comhshúlú tábhachtach
Tá an comhshúlú tábhachtach chun:
Sláinte oibrithe
Sláinte tháirgí
Cosaint nó laghdú ar dhiobháil a bheidh ar tháirgí mar thoradh ar sruth mór modhaint
Féabhrú fiabilité an chórais fuinnimh.
Rangú Comhshúlú
Tá an comhshúlú roinnte go forleathan mar
Comhshúlú córais (Nasc idir cuid den tionscal sa chóras ag obair cosúil le neodracht LV transformer fuinnimh winding) agus an talamh.
Comhshúlú táirge (cosaint comhshúlú) ag nasc corp táirgí (mar motor leictreach corp, tank transformer, switchgear box, operating rods of air break switches, corp briseadh LV, corp briseadh HV, corp briseadh feeder etc) go dtí an talamh.
Líomhaintí Ceadaithe Modhúlachais Talamh
Líomhaintí rathúla do modhúlachas talaimh:
Stáisiúin fuinnimh – 0.5 ohms
Stáisiúin EHT – 1.0 ohms
33KV SS – 2 ohms
Struchtúir DTR – 5 ohms
Modhúlachas tolla toraidh – 10 ohms
Cén Básic atá ann chun Líomhaintí Modhúlachais Talamh Ceadaithe a Shroich?
De réir rialacha IE, ní mór a bheith agat bonn cruinn don rud sin de réir rialacha IE, ní mór a bheith agat voltas teanga níos lú ná
Luach suarach 523 volts
Ifault = modhaint is airde i gcórais fault,
Is 100 KVA an modhaint is airde, is 100 A an modhaint i 100 KVA, áit a bhfuil 4% an impedance céadta
Do stáisiún 100 KVA transformer
0.26 ohms being quite low, quality work is to be done during construction, to obtain such a value of the earthing system, and the expenditure for that will be very high.
Hence the electrical inspectors are insisting about 1.0 ohms. This seems to justify for the urban areas. This value may be 2 ohms in case of rural areas, which is recommended by most of the authorities.The earth electrode resistance value also carries importance in view of full protection by lightning arrestors against lightning.
The earth electrode resistance value in that case is given by the formula
Flash over voltage of 11 KV = 75 KV, and a lightning arrestor Displacement = 40 KA.
Cineál Comhshúlú
Cineál Pláta Comhshúlú
In this, cast Iron plate of size 600 mm × 600 mm × 6.3 mm thick plate is being used as earth plate. This is being connected with hot dip GI main earth strip of size 50mm breadth × 6mm thick × 2.5 meter long by means of nut, bolts and washers of required size. The main earth strip is connected with hot dip GI strip of size 40mm × 3mm of required length as per the site location up to the equipment earth / neutral connection.
The earth plate is back filled and covered with earthing material (mixture of charcoal & salt) by 150mm from all six sides. The remaining pit is back filled with excavated earth. Along with earth plate, rigid PVC pipe of 2.5 meter long is also provided in the earth pit for watering purpose for to keep the earthing resistance within specific limit.
Cineál Pípa Comhshúlú
In this method hot dip GI pipe of size 40 mm dia × 2.5 meter is being used for equipment earthing. This pipe is perforated at each interval of 100mm and is tapered at lower end. A clamped is welded with this pipe at 100 mm below the top for making connection with hot dip GI strip of size 40mm × 3mm of required length as per the site location up to the equipment earth / neutral connection. On its open end funnel is being fitted for watering purpose. The earth pipe is placed inside 2700 mm depth pit. A 600mm dia “farma“ of GI sheet or cement pipe in two halves is are placed around the pipe.
Then the angular space between this “farma” and earth pipe is back filled with alternate layer of 300mm height with salt and charcoal. The remaining space outside “farma” will be backfilled by excavated earth. The “farma” is gradually lifted up as the backfilling up progresses.
Thus the pit is being filled up to the 300mm below the ground level. This remaining portion is covered by constructing a small chamber of brick so that top open end of pipe and connection with main earth pipe will be accessible for attending when necessary. The chamber is closed by wooden/stone cover. Water is poured into the pipe through its open end funnel to keep the earthing resistance within specific limit.
Other Types of Earthing: When the capabilities of certain equipment are limited, they may not with stand certain fault currents then the following types of earthing are resorted to limit the fault current.
