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Short Circuit Indicator type MF |
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| Design The short circuit indicator type MF consists of: 1 pc. reading instrument 3 pcs. sensors connection cable The reading instrument is available as a panel- mounted instrument and as a surface- mounted instrument. Both versions can be equipped with a remote indication contact. The set of sensors (version MFS) consists of three 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 3000 mm (standard - on request other lengths are possible, too). The light mains sensors (version MFL) are connected to the reading instrument with light mains ( standard length 1400 mm - other lengths are possible, too). |
| Function The sensors are installed on the medium voltage cables. In case of a short circuit, a coil, which is mounted into the sensor's housing, is being energized. This coil transmits an impulse to the reading instrument. Within the reading instrument the impulse is evaluated. Minimum impulse adjustment: The reading instrument is equipped with a setting for minimum impulse duration. The impulse picked up from the sensor is checked for its length. If the impulse length is shorter than the adjusted mininum impulse duration, no fault will be indicated. If the impulse length is longer than the preadjusted duration, a short circuit is indicated. This equipment allows filtering peak currents caused by switch currents or similar circumstances. Wrong indications are avoided. The reset of the earth fault or short circuit indication can be done in the following ways: a) automatic time reset: A time element controls the indication and resets it after a preadjusted time (3 values between 0.5 h to 40 h are selectable). b) manual reset with a push-button c) recovering net voltage (if the reading instrument is supplied from the monitored net. |
| Assembling (please refer to the assembling instruction) The sensors are installed on the conductors with steel frames. For this purpose, the frame has to be disconnected from the sensor housing and has to be placed around the high voltage core. After this, the sensor has to be fixed in its final position. a.) surface- mounted instrument The surface- mounted instrument has to be fixed with two screws. The connection cable can be inserted into the terminal box of the reading instrument from the back side or from the bottom of the housing. b.) panel- mounted instrument The panel mounted version has to be pushed into a prepared cutout of a panel. (dimensions of the cutout: 91.5+0.8 * 44.5 +0.6 mm). The housing of the reading instrument is equipped with spring clamps (standard; please refer to figure 1). It has to be pushed into the cutout with a little pressure. |
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| Technical
Data operating current: short circuit: 150A to 1500A Dimensions ( W * H * D ) accuracy: +/- 10 % reading instrument: temperature range: -20°C to +70°C panel-mounted instrument 96* 48*63 mm reading instrument: reset time delay: 0.5h to 40h surface-mounted instrument 76*140*42 mm power request: stand by mode: 5-10µA sensor: indication mode: 60µA short circuit sensor 38* 38*26 mm power supply: selectable: - 230 V AC Protection class (also possible with accumulator) panel-mounted instrument IP 46 - 9 V to 110 V DC surface-mounted instrument IP 65 - lithium battery sensors IP 67 remote indication: max. 230 V AC / 50 W to 150 W |
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