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Brand advantage: Allen Bradley, BentlyNevada, ABB, Emerson Ovation, Honeywell DCS, Rockwell ICS Triplex, FOXBORO, Schneider PLC, GE Fanuc, Motorola, HIMA, TRICONEX, Prosoft etc. Various kinds of imported industrial parts

7ML52020EA0 Ultrasonic level meter

Permissive directional comparison scheme In this scheme, each of the protection functions has to receive a signal from the opposite end of line in order to be able to trip. A protection function sends a permissive signal when its current exceeds the enabling level ‘I setting’, the basic time ‘t Basic’ has expired and the fault detected is in the forwards direction. Options:
Echo “Bkr”: Providing this parameter is active, a permissive signal (echo) is sent to the opposite end of the line, if the local circuitbreaker is open and a signal is received. Tripping is thus possible at the infeed end. The duration of the echo signal is limited to 150 ms.
Non-directional echo “Weak infeed”: If the directional E/F function at the weak infeed end of a line cannot measure, because the reference voltage is too low or the current does not reach the enabling level, a signal is returned to the opposite end of the line if one is received. This enables tripping to take place at the end with the stronger infeed.Operation of a permissive directional comparison scheme <...> : optional function Rx : receive MeasFwd : fault in forwards direction MeasBwd : fault in backwards direction including ‘Transient blocking’ MeasBwd’ : fault in backwards direction I dir : current enable for directional measurement (I-dir = 0.7 I-Setting) I Setting : current enabling level Iasymm : asymmetrical currents under normal load conditions Tx : send T : trip TB : transient blocking t TransBlk : blocking time t Basic : basic time t Wait : waiting time U Setting : reference voltage

Blocking directional comparison scheme

 Providing the conditions for directional measurement are fulfilled i.e. the current higher than ‘I dir’ and the voltage higher than its enabling level ‘U-Setting’, a protection function transmits a blocking signal to the remote station immediately it detects a fault in the backwards direction. Note: I dir = 0.7 I-Setting A protection function measuring a fault in the direction of the protected line trips at the end of the adjustable waiting time ‘t wait’, providing a blocking signal is not received beforehand. Options:
SendMode: ‘non-directional’ A blocking signal is transmitted in this mode, if the current is higher than ‘I dir’, the basic time has expired and no fault is detected in the forwards direction (including when 3U0 < U-Setting).Setting the enabling pick-up levels The setting of the current enabling ‘I dir’ must take account of the zero-sequence component in normal operation arising from system asymmetries. The pick-up setting for the voltage enabling signal ‘U-Setting’ is determined by the level of asymmetries on the secondary side (v.t. tolerances, asymmetrical burdens etc.). The ability to read voltage and current values on the relay is a useful aid for determining these settings. For example, if the enabling current setting ‘I-Setting’ is too low, the pick-up signal lights continuously (current circuit enabled). Since an E/F causes asymmetrical voltages in the vicinity of the fault, the current flowing via the system capacitances also has a zero-sequence component. A capacitive current of this kind on a long line lies within the setting range of the sensitive E/F protection function.