转移点温度计算(举例)

TECHNICAL DATA

for

CURRENT CARRYING CAPACITY & SAG-TENSION PROPERTIES 允许电流及弧垂-张力特性的技术规范书

导线名称

CABLE DESIGNATION :

STACIR/AW 180?

TACSR 110?

STACIR/AW 130?(ALTERNATIVE)

投标单位技术资料号码

TENDER / BIDDER SPEC. NO.

: 0673-NCIP2004/15

业主

CLIENT & CUSTOMER

:

PREPARED BY J. S. GIL

CHECKED BY S. Y. PARK

APPROVED BY H. H. PARK

Manager

Overhead Transmission Project Dept.

Electric Power Division

1 超耐热铝合金镀铝殷钢导线的允许电流 Current Carrying Capacity for STACIR/AW

若提供允许的导线温度，架空铝导线的允许电流，气候条件和导线特性可依照IEEE Std. 738“计算空架空导线的电流-温度关系”算出。

The current carrying capacity of overhead aluminum conductor given a allowable conductor temperature, weather conditions and conductor characteristics can be calculated in accordance with IEEE Std. 738 " Calculating the Current-Temperature Relationship of Bare Overhead Conductors".

1-1 线路详细资料和气候条件

1-2 计算允许电流

Calculating the currebt carrying capacity 1-2.1

对流热损失

Convection heat loss (q c ):

a. 自然对流（风俗=0）：不应用于本案例

Natural convection (wind speed=zero) : Not applicable in this case case this in Applicable Not ,)T T (D 283.0q 25.1a c 75.05.0f c -???=ρ

b. 强制对流

Forc ed convection (wind speed ≠ zero)

speed

wind high for )T T (k V D 1695.0q speed wind low for )T T (k V D 371.001.1q a c f 6

.0f w f 2c a c f 52

.0f w f 1

c -?????

?

?

????=-??????

???

????

? ?????+=μρμρ

在任何风速，

At any wind speeds, the lager of the two calculated convection heat losses is used.

1-2.2

辐射热损失

Radiated heat loss (qr):

????

???????? ??+-???? ?

?+???=4a 4c r 100273T 100273T D 138.0q ε 1-2.3

获取的太阳热 Solar heat gain (qs): [])Z Z cos()H cos(cos ,where '

A )sin(Q q 1c c 1s s -?=???=-θθα

1-2.4

稳定情形的热平衡

Steady-state heat balance:

)

T (R q q q I )

T (R I q q q c s r c c 2s r c -+=

∴?+=+

1-2.5 允许电流的计算结果 Calculation Results for Current Carrying Capacity

2 超耐热铝合金镀铝殷钢导线的弧垂和张力计算

Sag and Tension Calculation for STACIR/AW

超耐热铝合金铝包殷钢导线的弧垂和张力计算方法不同于传统的铝包钢芯。因为用于超耐热铝合金铝包殷钢导线芯的铝包殷钢合金具有极小的线性膨胀系数，导线的线性膨胀合成系数很小。在普通条件下将导线安装在架空输电线时，应考虑这种线性膨胀合成系数。另外，在某个温度以上，殷钢芯使超耐热铝合金铝包殷钢导线的所有机械张力保持不变，因为镀铝殷钢丝的热膨胀远小于铝合金丝的热膨胀，导致铝部分的负荷等于零。上述温度被叫做：“转移点温度”

因此，在转移点温度以上的温度，导线的热膨胀和弹性延伸取决于殷钢芯，且弧垂增加的百分比极小，由此获取极好的弧垂特性。这种做法存在于传统的铝包导线，但是不被考虑，因为它的温度通常高于持续运行温度

The calculation method of the sag and tension for STACIR/AW is different from that of the conventional ACSR. Because the aluminum-clad invar alloy used for core of STACIR/AW has a extremely small coefficient of linear expansion, the composite coefficient of linear expansion of the conductor is small. Under normal conditions for string the conductor on overhead transmission, this composite coefficient of linear expansion can be considered. In addition, all the mechanical tension in the STACIR/AW will be sustained by the invar core above a certain conductor temperature at which the stress of the aluminum part comes to zero because the thermal expansion of an aluminum-clad invar wires is much smaller than that of an aluminum alloy wires.

This certain temperature is called 'transition point temperature'.

The thermal expansion and elastic elongation of the conductor thus depends on those of the invar core above the transition point temperature and the percentage of increase in the sag is extremely small so that excellent sag properties are obtained. This behavior exists in the conventional ACSR but need not to be considered because its temperature is usually higher than the continuous operating temperature.

1) 公式中符号的定义

2) 转移点温度的计算

The calculation of transition point temperature

As for the initial condition that prescribes the relation of the divided tension of the INVAR wire and the STAL wire, we can regard that both of them are under no tension on the temperature condition of t 0 (℃), usually, t 0 = 15℃, with a conductor length of l 0 right after being manufactured. In the meantime, after stringing at site with change of temperature to t (℃) and of tension to T (kg), if we would assume the divided tension of both STAL wire and Invar wire as T a (kg) and T s (kg), the following equation, therefore, would be effective;

{

{}1){(1}1){(1A E T t t l A E T t t l s

s s 0s 0a a a 0a 0+-+=+-+αα---- 等式1.1 Equation 1.1

排除l 0并忽略小的项目 Removing l 0 and ignoring small items

0))((t t A E T A E T 0

s a s

s s a a a =--+-αα---- 等式1.2 Equation 1.2

另一方面, On the other hand,

T T T s a =+ ----- 等式1.3 Equation 1.3

由1.2和1.3排除T s Eliminating T s by equation 1.2 & 1.3

A E A E A E t t A E T T a a a

a s s 0s a s s a )

)((+---=

αα ----- 等式1.4 Equation 1.4

等式1.4表示在温度t(℃)时超耐热铝合金丝承担的张力T(kg)。其次，我们考虑转移点的条件,此时，铝合金丝不承担导线的任何张力。

Equation 1.4 shows the divided tension of STAL wire when tension is T(kg) in temperature t(℃). Next, we consider the condition of the transition point. At that time, Aluminum alloy wire does not share the tension of conductor anymore.

因此，Thus, T a = 0.

由此从等式1.4 So from equation 1.4,

))((t t A E T 0c s a s s c --=αα----- 等式1.5 Equation 1.5

另一方面，由温度和张力关系得出弧垂曲线后的实际长度（在最差条件）。

On the other hand, by the relationship of real length by the sag-curve and that shown calculated by relation of temperature and tension (in the worst condition)

)}(1){EA

1(24S t t T l S T W q 01103

2122

1-α++=+----- 等式1.6 Equation 1.6

在转移点温度

In transition point temperature,

)}(1){EA

1(24S t t T l S T W 0c c 032c 2

-α++=+---- 等式1.7 Equation 1.7

由1.6和1.7，排除l 0 忽略小项目 Removing l 0 by 1.6 & 1.7, ignoring small items

024

EA }EA )(24EA {

S W T t t T T S W q T 2

22

c 1C 1c 222

13C =--α+-+----- 等式1.8 Equation 1.8

同时，我们由等式1.5和1.8得T C & t C 。

We can get T C & t C by equation 1.5 & 1.8, simultaneously.

3)经计算，我们假设T c 并将其应用在1.5和1.8重复地计算。然而这需要较长时间，所以我们将其

简化为实际计算式。现在，我们计算温度 t 0 (℃)无风无雪条件下的张力T 01 (kg)。我们称其为第一条件。

By computing, we assume T c and apply it 1.5 & 1.8 for calculation repeatedly.

But it will take long time. So we can make it simple as the practical calculating expression. Now, we calculate tension T 01 (kg) in t 0 (℃) and no wind, no snow condition. We call it No.1 condition

t 1 = t 0, q 1=1.0 and T 1 = T 01

其次将其应用于1.5和1.8。 Next apply it to 1.5 & 1.8,

M )1M (a a a a 01c 2

01c 3T T T T αααααα??

? ????? ??-=--+---- 等式1.10 Equation 1.10

这里，Here, T S W 301

2

2

24EA M =

----- 等式1.10 equation 1.10

因而，我们计算等式得出可变的

T T 01

C 。 Accordingly, we calculate equation having a variable T T 01

C 从上述方法，转移点不是导线的特殊数字，而是随着T & S 的变化发生变化。 By way of the above, transition point is not peculiar number of conductor, but changing by T & S.

4) 在可选择的环境中弧垂及张力的计算

The calculation of sag and tension in the optional condition

无风无雪条件下计算时，我们依照被请求的温度条件选择参数。当我们计算超耐热铝导线丝分担的张力时，将T 2 和 t 2 应用于公式1.4中的 T 和 t 。在存在雪和雨的重量时转移点会升高。因此，当应用等式1.4分担张力为负数时，先试用第一种方法，再试第二种方法。

About the calculation under no wind and no snow condition, we select the parameter according to the requested temperature condition. When we calculate the divided tension of the STAL wire, we apply T 2 & t 2 to T, t of equation 1.4. In case of the snow and rain weight, turning point may rise. Therefore, try in the first way first and next when the divided tension is minus by equation 1.4, try case II again.