# US 5,352,983 A · Method and apparatus for detecting flashover between conductors in power transmission lines of different voltage levels suspended in parallel from the same towers

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- Number: US 5,352,983 A
- Document ID: US5352983A
- Status: Granted
- Kind: A
- Application number: 07/983,728
- Filed: 1992-12-01
- Granted: 1994-10-04
- Earliest claimed: 1991-12-20
- Assignees: Asea Brown Boveri AG
- Inventors: Leif Eriksson; Murari M. Saha
- Web page: https://patentgrep.com/patent/US5352983A

## CPC

- G01R 31/08: Locating faults in cables, transmission lines, or networks
- H02H 7/267: {for parallel lines and wires}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)

## Abstract

The invention relates to a method and a device for detecting a flashover between conductors in power transmission lines of different voltage levels suspended from the same towers and wherein the power lines are included in a power network where one of the power lines is stated to be a high-voltage power line (1) and where the other power lines are connected to the high-voltage line via transformers of a known transformer ratio (am) and internal impedance (ZXm) and wherein the line impedances (ZL) are known. Specific to the invention is that the fault current which is caused by a flashover is set to be equal to a detected current change in any of the phases in the high-voltage line. With this assumption an equation system can be set up with the aid of which the relative distance to fault n (0<n<1) can be determined. If the produced value of n lies within the stated region, this is interpreted as if an internal flashover has occurred.

## Claims

### Claim 1

Apparatus for detecting a flashover between conductors in power transmission lines of different voltage levels suspended from the same towers, comprising:
a power network comprising the power lines and wherein one of the power lines is a high voltage power line and the other power lines are connected to the high voltage power line via transformers of a known transformer ratio (am) and internal impedance (ZXm), and wherein the line impedances (ZL) are known;
a flashover indicating means (CALC) storing the known transformer ratios (am), the line impedances (ZL) and the internal impedances (ZXm) for determining the occurrence of a flashover;
said flashover indicating means receiving the phase currents I1 and phase voltages U1 of the high voltage line and detecting a current change I1 in any of the phases in the high voltage line and calculating the following parameters: ##EQU2## where .alpha., .beta., .phi. and .gamma. may be R-, S- or t-phase and n.multidot.ZL is the line impedance from the measuring station to the fault location (F) at the relative distance to fault n, whereby fault n can be determined; and
said flashover determining means generates a signal IF for indicating that a flashover has occurred within the protective zone if 0<n<1.

### Claim 2 (depends on 1)

Apparatus for detecting a flashover according to claim 1, wherein said flashover determining means operates only when the detected current change .DELTA.I1.alpha. exceeds a pre-set limit value .DELTA.I.alpha.g.