Cad é an Sag i nGnáthcheolaitheoir Oirthear?
Cén fáth atá i gConduidheoir Thar Talamh?
Míniú ar an Fáth
Is é an fáth i líne seachtrach an fad bhearta ón bpunt suime is airde go dtí an bpunt is ísle den chonduidheoir.
Aim an Fháth
Leis an bhfáth cuí a chur isteach, déanann sé sin cosaint ar línte seachtra ó thodhchaí agus dianchúiseanna, go háirithe faoi choinsíonna corrach.Tá an fáth de dhíth i gconduidheoir líne seachtra. Tá na cunduitheoirí comhcheangailte idir dhá taca le luach fáth phearsanta.Tá an fáth tábhachtach mar gheall ar an mbarr a chosaint ó bhogadh ró-mhór agus ó thodhchaí neamhsafach, ag cothromú an fadtéarmachais.
Má tá an chonduidheoir stiúrtha go hiomlán le linn an tionscadail, déanann an gaoth brú ar an chonduidheoir, agus tá deis ag an chonduidheoir dul as a chéile nó a scuabadh ón taca deireanach. Mar sin, ceadaithear an fáth a bheith ann le linn an tionscadail.
Puingí tábhachtacha a mheas
Nuair a choimeádann dhá taca comhionann an chonduidheoir, cruthaíonn sé form shléibhe sa chonduidheoir. Tá an fáth an-bheag i gcomparáid le réimse an chonduidheoir.
Is parabóilíoch an cruinneas fáth-réim.
Ag gach pointe ar an chonduidheoir, is tangential an teannas, ag cothromú an réimse.
Arís, is consant an chuid córasach den theannas ar fud an fhada an chonduidheoir.
Is beagnach cothrom leis an theannas ag na tacáin an theannas ag aon pointe ar an chonduidheoir.
Modh Measúnachta
Nuair a dhéanann tú meas ar fáth i líne seachtra, ní mór dhá chondae éagsúla a mheas:
Nuair atá na tacáin ag an leibhéal céanna
Nuair atá na tacáin nach iad ag an leibhéal céanna
Athraíonn an foirmle chun an fáth a mheas bunaithe ar an leibhéal na dtacáin (mar shampla, na toraidh seachtra a chumasaíonn an chonduidheoir thar talamh).
Míniú ar an fáth nuair atá na tacáin ag an leibhéal céanna
Suppose, AOB is the conductor. A and B are points of supports. Point O is the lowest point and the midpoint.Let, L = length of the span, i.e. ABw is the weight per unit length of the conductorT is the tension in the conductor.We have chosen any point on the conductor, say point P.The distance of point P from the Lowest point O is x.y is the height from point O to point P.
Equating two moments of two forces about point O as per the figure above we get,
Sag calculation for supports are at unequal levels
Suppose AOB is the conductor that has point O as the lowest point.L is the Span of the conductor.h is the difference in height level between two supports.X 1 is the distance of support at the lower level point A from O.x2 is the distance of support at the upper-level point B from O.T is the tension of the conductor.w is the weight per unit length of the conductor.
So, having calculated the value of x 1 and x2, we can easily find out the value of sag S1 and sag S2. This formula calculates sag under conditions of still air and normal temperature, where only the conductor’s own weight affects it.
Impact Éanach
Some of the effects of ice and wind on sag include:
The weight per unit length of the conductor is changed when the wind blows at a certain force on the conductor and ice accumulate around the conductor.
Wind force acts on the conductor to change the conductor self-weight per unit length horizontally in the direction of the airflow.Ice loading acts on the conductor to change the conductor self-weight per unit length vertically downward.Considering wind force and ice loading both at a time, the conductor will have a resultant weight per unit length.
The resultant weight will create an angle with the ice loading down ward direction.Let us assume, w is the weight of the conductor per unit length.wi is the weight of ice per unit lengthwi= density of ice × volume of ice per unit length w is the force of wind per unit length.ww = wind pressure per unit area × projected area per unit length
So, the total weight of the conductor per unit length is
The sag in the conductor is given by
So the vertical sag
Safety Considerations
Proper sag calculation is vital for maintaining the structural integrity and operational reliability of transmission lines.
