DE20310361U1 - Power distribution network short circuit detector system counts faults with differential reset times - Google Patents

Abstract

A power distribution network short circuit detector (1.x) system has displays (6) for the first overcurrent pulse and separate displays (7) for other pulses using a time gate that is longer than the shorter supply protective device (2) reset time (tza) but less than the longer supply reset time (tzb).

Description

Utility model application Device for short-circuit direction detection in energy distribution networks

General description / state of the art

In energy distribution networks, particularly in the medium and high voltage range, so-called short-circuit and earth fault indicators (hereinafter referred to as short-circuit indicators) are known which indicate an overcurrent or short-circuit current (hereinafter referred to as overcurrent) when it occurs. The short-circuit indicators can be three-phase (see example Figure 1) as well as single- or two-phase. Overcurrents of a certain magnitude or higher are switched off a few ms after they occur by a higher-level protective device. This means that the measuring input of the short-circuit indicator only receives a brief overcurrent pulse. The display remains with the known short-circuit indicators even when the overcurrent pulse has already subsided. This makes it possible to localize the fault using the displays even several hours after the fault has occurred.

The energy direction of the overcurrent is usually not recorded in the short-circuit indicators. This is also not necessary in so-called radial networks or in networks that are not fed from two sides, since the energy direction is known to the operator anyway.

Task

Especially when used in closed or temporarily closed ring networks or in networks with two-sided feed-in, it is desirable to determine the direction of an overcurrent in order to narrow down the fault location as quickly as possible.

A reference quantity required for the directional decision (e.g. voltage) is not available at the usual installation locations for short-circuit indicators.

If the network is later operated as an open ring again or is only fed from one side, the same short-circuit indicator should be able to detect and indicate an overcurrent or short circuit, if possible without conversion.

Inventive solution

The task is fulfilled by the short-circuit indicator (1.x) being provided with an overcurrent counter, with which it determines the number of overcurrent pulses that have occurred within a predetermined time. The overcurrent counter can be implemented, for example, using a digital circuit known to those skilled in the art or using a microprocessor. If an overcurrent is now switched off by the higher-level protective devices (2), (3) after it has occurred, this state is evaluated and displayed by all short-circuit indicators (1.x) on the line (4) as the first overcurrent pulse. If a feed-in point (2) is switched on again to the faulty line (4) within a predefined time (tza), a second overcurrent pulse is measured by all short-circuit indicators (1.1), (1.2) between the reconnected feed-in point (2) and the fault location (5). The reconnection of the second feeder (3), if it is connected to the faulty line (4) a second time, is selected such that the pause time (tzb) between the first overcurrent pulse and reconnection is significantly longer than the gate time (ta) of the short-circuit indicators (Lx).

The second or further overcurrent pulses are now displayed by the short-circuit indicator using additional or other displays that can be visually differentiated from the first display (e.g. flashing and permanent optical signal or two different colors, etc.). This allows the operator to see from each short-circuit indicator whether he has measured no, one, two or more overcurrent pulses. Depending on the network type implemented, the following error displays are displayed:

In the case of one-sided supply (e.g. only from (2)) or openly operated ring networks, only a single overcurrent pulse is measured and displayed by the short-circuit indicators between the feed-in point and the fault location, i.e. the fault location is located behind the last indicating short-circuit indicator (1.2).

In the case of two-sided feeding or closed ring networks, only the short-circuit indicators (1.1 and 1.2) measure and display two overcurrent pulses between the feed-in point (2) that is reconnected within the gate time ta and the fault location (5), while the other short-circuit indicators (1.3 and 1.4) only detect one overcurrent pulse. This means that the fault location is behind the last short-circuit indicator with the display for two overcurrent pulses.

Claims (3)

1. Device for short-circuit detection (1.x) in energy distribution networks, in particular in the medium or high voltage level, characterized in that it has a display ( 6 ) which shows the occurrence of a first overcurrent pulse and, in addition, has at least one additional display ( 7 ) which can be differentiated at least optically from the display ( 6 ) and which can show the occurrence of further overcurrent pulses within a predetermined gate time (ta). 2. Device according to claim 1, characterized in that this is set in conjunction with a reconnection device at the feed points ( 2 ), ( 3 ) so that it reliably detects the second or further overcurrent pulses which are generated by the reconnection of an individual feed side ( 2 ) after an overcurrent shutdown within an adjustable gate time (ta) and displays them by means of the additional display ( 7 ), while the other feed side ( 3 ) is no longer connected at all or the reconnection takes place after a pause time (tzb) which is selected to be significantly longer than the gate time (ta) of the short-circuit indicators (1.x). 3. Device according to one of claims 1 or 2, characterized in that the short-circuit indicators can be single-phase, two-phase or three-phase and each have more than one indicator.