Siemens 7SR158 Argus, Technical Manual

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7SR158 Technical Manual
Chapter 1) Page 24 of 38 ©2014 Siemens Protection Devices Limited
3.3 Voltage Protection: Neutral Overvoltage (59N)
Two Neutral Overvoltage (or Neutral Voltage Displacement) elements are provided 59NIT & 59NDT .
The relay measures fundamental frequency residual voltage for this function. The relay can be connected to
directly measure residual voltage (3V0 input) i.e. ‘CT/VT CONFIG > Phase Voltage Config’ setting =
‘Vab,Vbc,3Vo’. Alternatively the value of residual voltage can be derived from the phase-neutral voltages i.e.
‘CT/VT CONFIG > Phase Voltage Config’ setting = ‘Van,Vbn,Vcn’.
The 59NIT element can be configured to be either definite time lag (DTL) or inverse definite minimum time
(IDMT),
59NIT Setting sets the pick-up voltage level (3V0) for the element.
An inverse definite minimum time (IDMT) can be selected using 59NIT Char . A time multiplier is applied to the
characteristic curves using the 59NIT Time Mult setting (M):
ms
1
Vs
3Vo
M * 1000
op
t
Alternatively, a definite time lag delay (DTL) can be chosen using 59NITChar . When Delay (DTL) is selected the
time multiplier is not applied and the 59NIT Delay (DTL) setting is used instead.
An instantaneous or definite time delayed reset can be applied using the 59NIT Reset setting.
The 59NDT element has a DTL characteristic. 59NDT Setting sets the pick-up voltage (3V0) and 59NDT Delay
the follower time delay.
Operation of the neutral overvoltage elements can be inhibited from:
Inhibit 59NIT A binary or virtual input.
Inhibit59NDT A binary or virtual input.
User Inhibit Reylogic (graphical logic)
Figure 3-3 Logic Diagram: Neutral Overvoltage Element (59N)