Design
The short circuit indicator type GI consists of the reading instrument and 3 pcs. of sensors including connection cables. The reading instrument is available as a surface -mounted instrument. The two versions can be delivered with a remote indication contact.
The sensor-set (version type GI-S) consists of 3 single sensors. The cable output of these sensors is combined in one junction. The cable length from this junction point to the reading instrument is 2600 mm (standard, other lengths are possible on special request).
The light mains sensors (version GI-L) are connected to the reading instrument via light mains ( standard length 1400 mm).
Function
The sensors are installed on the medium voltage cable of a ring network. The reading instrument operates with two flag indicators. The first flag indicator detects the first short circuit. The second flag detects the following short circuit. In case of a short circuit, the high short circuit current energizes a coil which is incorporated in the sensor. This coil transmits an impulse to the reading instrument. When the impulse has reached the preadjusted level, the short circuit will be indicated. The operating point is separately selectable for each sensor. After a preadjusted time, a reset impulse resets the indicator into the stand-by modus (a black surface becomes visible). In case a short circuit occurs within a ring-network, all indicators affected will indicate this fault. By "switching off" the respective section of the network or by opening the ring circuit arrangement, the second flag indicators of the all the short circuit indicators placed between the net input and the location of the fault are stimulated. The short circuit fault is located between the last indicating instrument and the first not-indicating instrument.
On special request, it is possible to adjust an indication-delay for all impulses coming from the sensors. The advantage is that peaks caused by switching on big engines or transformers will not lead to a short circuit indication.
The indication delay is possible within the range of 40 to 300ms.
Assembling The frame on the sensor housing has to be disconnected and laid around the high voltage core. The frame has to be put into its final position and must be connected to the sensor again. The surface-mounted instrument has to be fixed with two screws according to figure 1. The connection cable can be inserted into the terminal box either from the back side or from the bottom.
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