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| The electronically operated short circuit indicator offers many solutions to meet the requested conditions. The following figure shows the different ways of adjusting the indicator and the block diagram of the function. |
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note: |
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can be preadjusted in our workshop
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Description
1.) Sensor
The sensor, which is mounted on the high voltage conductor, detects the short circuit inductively. |
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| The operating level is adjusted in each sensor |
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| Thus any faulty influence on the data transfer between sensor and reading instrument is inhibited |
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2.) Impulse monitoring
The period of the impulses transmitted from the sensor (= actual short circuit current) can be in the range of 10 ms to 400 ms.
The duration of the impulses is checked by the impulse control in order to avoid wrong indications.
A minimum impulse duration is adjusted to make sure that a peak current ( e.g. caused by switching processes, e.g.) does not cause an indication. If the minimum impulse duration has been adjusted to 40 ms, for example, the sensor has to transmit an impulse longer than 40 ms before the reading instrument indicates a short circuit.
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| adjustment of the minimum impulse duration |
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This serves to avoid wrong indications. |
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3.) Evaluation
The short circuit signal impulse transmitted by the impulse control activates the short circuit indication, the remote indication relay and the time reset. After the equipment has been reset either by hand, by operating current or after a pradjusted reset time, the evaluation unit switches the indicator into stand-by modus.
4.) Indication / Remote indication
The short circuit can be indicated visually with LEDs or with flag indicators. For remote indication, a potential-free alternating contact is provided.
5.) Reset
The short circuit indicator can be reset into stand-by modus as follows:
a) by manual reset
The short circuit indicator can be set into stand-by modus any time with a trigger switch.
b) by operating current
The operating current must be deduced from the high voltage system. In case of a short circuit, this voltage breaks down.
When reclosing the system, the operating voltage recovers and resets the indicator automatically. The time between the recovery of the operating voltage and and the reset process of the short circuit indication is adjustable.
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Adjustment of the reset delay after recovery of the operating voltage
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This time delay eliminates those disturbances affecting the short circuit indicator which occur when switching on the network
c.) Time reset
The evaluation unit is equipped with a timing element. This timing element can be adjusted to every reset
time (0,5 - 1 - 2 - 3 - 4 h standard).
This time starts running at the moment when a short circuit occurs, respectively when the power supply of the reading instrument recovers. |
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Preadjusting of reset time of the short circuit indicator
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| The reset time depends on the maintenance system of the user. |
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Standard settings
1) operating point (current) of the short circuit indicator: defined by customer
2) minimum impulse duration: 40 ms
3) reset delay: 2 sec
4) time reset: defined by customer |
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