H. Cheng (China), Evaluation of Risk Influence from Power Cable to Communication Line In

H. Cheng (China), Evaluation of risk influence from power cable to communication line in transrapid Shanghai (update P2.18, Q1.3) (Shanghai Jiaotong University, [email protected] ; co-authors : Shanghai Jiaotong University: G. Lu ; Shanghai Eastern Power Supply Company: W. He, J. Zhang, G. Pan)

This paper introduces an evaluation technique of risk influence from power cable to communication line. Inductive coupling, capacitive coupling and resistance coupling are three electromagnetic disturbances from power cable to communication line. Inductive coupling is the most important from power cable with metallic shield to communication lines when they are parallel with in a long length. In TRANSRAPID Shanghai, some 110kV power cables are parallel with communication lines, shown as Fig1:

Fig 1. Layout of communication lines and 110kV cables in TRANSRAPID Shanghai

A computation model of inductive voltage from power cable to communication line in worst condition is also presented in this paper. The principle of computation can be illustrated as the following formula:

E    M  I s l p  K m (1) where E ,an inductive voltage;  , angle frequency of influence current,  2f ; f , frequency of influence current, in China, f= 50 Hz; M , mutual inductance between power cable and communication line;

I s , magnitude of effective influence current, is the short circuit current here;

l p , parallel length of two cables;

K m ,equivalent shielding coefficient , is related to the structure and material of communication lines. K m is equal to 0.9 in this place.

Its original inductive voltage on communication lines in TRANSRAPID Shanghai greatly exceeds the national permissible standard because some 110kV power cables are parallel with communication lines. The inductive voltage on communication lines can be greatly reduced via intercrossing of several short power cables shield and a parallel connection on two sides of a long cable shield,shown as Fig2 :

Fig2. Remediation through multi-point earth

Problem of inductive coupling of 110kV power cables and communication lines in TRANSRAPID Shanghai is also effectively solved.

Keywords: power cable, communication lines, inductive coupling, intercross of cable shield, inductive voltage, risk influence, evaluation