【正文】 點：它允許改變饋 線的長度和阻抗大小。這種情況下，很多列車會聚集在一個車站內(nèi)。 無節(jié)制的下降電壓水平，可導(dǎo)致火車斷線。接著這個最小值與允許的絕對最小值進行比較，如果電壓太低，那么時間間隔就可以以分鐘為單位進行增加： 11 ???? ?ii （ 1） 然后啟動模型模擬。然后，有可能提供額外的輸入數(shù)據(jù)：固定的列車速度，選擇列車數(shù)，列車間的最小時間間隔，牽引網(wǎng)類型，其阻抗，位移間隔等等。 3 結(jié)論 已經(jīng)指出為何及何時要預(yù)測鐵路供電系統(tǒng)的不同運行模式。該研究還被羅斯托夫州立交通通訊大學用于教育當中。 20 這就是為了盡可能簡單的構(gòu)造的模型仿真的工作模式。首先，用戶從一個預(yù)定列表區(qū)中選擇對 應(yīng)用程序來所數(shù)據(jù)可以用的變電所區(qū)段。 19 也有可能改變火車的速度和 ? 列火車的時間間隔。當然，電壓損失也增加了。最復(fù)雜地是在交流系統(tǒng)中變電所間帶只能從一個鄰近的變電所方向獲得不同相位的供電（圖 4）。 這將導(dǎo)致饋 線短的變電所 電流比饋 線長的變電所的電流總是要大一些。多數(shù)貨物列車由一個平均的負載 。輸入的數(shù)據(jù)是一組收集的真實火車的電流或者計算，該計算采取剖面（ 200 米精度）和列車的負載。在這種情況下，唯一的一個可靠數(shù)據(jù)是一天中和鐵路區(qū)段的列車數(shù)，后者的參數(shù)可以確定電力支出和火車電流。 2 模擬 問題的解決方案包括以下問題： 1） 建立一個計算機模型，就可以預(yù)知供電系統(tǒng)的工作條件 2） 這個模型應(yīng)該有直接對應(yīng)的真實的鐵路區(qū)段，并應(yīng)模擬其特點，越準確越好。像這樣的一個方案總是有很高的電流與電壓的損失。通常讓一些火車成群的在單一軌道區(qū)段上朝一個方向開（火車間有固定的間隙），讓后讓火車往另一方向開。要求成本應(yīng)盡可能低，但又不妨礙可靠性，而且要求可靠性居高不下。s weight into account. The train schedule or the positioning rules are also defined. Modelling the normal mode Let us first consider modelling single track railway sections. Note the main parameters that should be determined by the working model: * Maximum traction work currents * Maximum voltage losses The current in traction work should not exceed the bound permissible by heating norms. Voltage losses should not be too large because train speed depends on the voltage. According to the Russian standards, if the voltage in traction work is kV, minimal possible voltage on a lootive should be 21 kV (which means the losses should never exceed kV) On design stage the type and diameter of a traction work is determined according to these three criteria: * Costs * Maximum traction work current 6 * Maximum voltage losses It is mon to start the research from the least possible traction work diameter. Then it is increased until all three choice criteria are met. On this stage a special train positioning is used: a pack of cargo trains is formed with a minimal possible gap in between and sent to one direction. Most cargo trains in this pack have average weight. but some of them (usually one or two) have maximum weight allowed for the inter substation zone. It should be noted that the number of trains in a pack, as well as the number of heavy trains is determined by a special standard document that fixes their dependency from the overall number of trains on that particular direction. This document is always a very important part of research on Russian railway power supply systems design (see Table 1). Number of trains in a day Time interval (minutes) Number of cargo trains in a pack Cargo Passenger Up to 24 Up to 20 20 2 More than 20 15 3 2436 Up to20 12 4 More than 20 10 6 3748 Up to 20 9 5 More than 20 8 7 4972 Up to 20 8 7 More than 20 6 10 More than 72 Up to 20 7 8 More than 20 5 12 Table 1: Determining the number of cargo trains and the time interval 7 between subsequent trains in a pack. Additionally, the model takes care of: * different ordering of average cargo trains and heavy cargo trains * displacement interval (the time difference between arrival on the inter substation zone of trains from one direction and the other) * feeder length (the length of the feeding wire which connects railway substation with traction work) It is worth mentioning that some railway sections place substations on some distance from the railway. If the length of the feeders is long enough to influence the voltage on the lootive, this should be taken into account. It is also possible to have one railway substation placed at a distance with a feeder length of several kilometres, while the other one is placed directly on a railway. This leads to the currents of the substation with a shorter feeder length to be always greater than the currents of the substation with a longer feeder. In order to pensate the currents it is possible to artificially increase the length of a feeder on the substation which is too close to the railway (Figure 3). Figure 3: Artificial increase in feeder length. Taking all section peculiarities into ac